Hydration State Research Articles

Muscle-Inspired Formable Wood-Based Phase Change Materials.

Phase change materials (PCMs) are crucial for sustainable thermal management in energy-efficient construction and cold chain logistics, as they can store and release renewable thermal energy. However, traditional PCMs suffer from leakage and a loss of formability above their phase change temperatures, limiting their shape stability and versatility. Inspired by the muscle structure, formable PCMs with a hierarchical structure and solvent-responsive supramolecular networks based on polyvinyl alcohol (PVA)/wood composites are developed. The material, in its hydrated state, demonstrates low stiffness and pliability due to the weak hydrogen bonding between aligned wood fibers and PVA molecules. Through treatment of poly(ethylene glycol) (PEG) into the PVA/wood PEG gel (PEG/PVA/W) with strengthened hydrogen bonds, the resulting wood-based PCMs in the hard and melting states elevate the tensile stress from 10.14 to 80.86MPa and the stiffness from 420MPa to 4.8GPa, making it 530 times stiffer than the PEG/PVA counterpart. Capable of morphing in response to solvent changes, these formable PCMs enable intricate designs for thermal management. Furthermore, supported by a comprehensive life cycle assessment, these shape-adaptable, recyclable, and biodegradable PCMs with lower environmental footprint present a sustainable alternative to conventional plastics and thermal management materials.

A structural determinant of the behavior of water at hydration and nanoconfinement conditions.

The molecular nature of the phases that conform the two-liquid scenario is elucidated in this work in the light of a molecular principle governing water structuring, which unveils the relevance of the contraction and reorientation of the second molecular shell to allow for the existence of coordination defects in water's hydrogen bond network. In turn, such principle is shown to also determine the behavior of hydration and nanoconfined water while enabling to define conditions for wettability (quantifying hydrophobicity and predicting drying transitions), thus opening the possibility to unravel the active role of water in central fields of research.

Hydration status of esports players in a live competition

Objectives: esports are an increasingly popular activity that involves professional players. Dehydration hinders cognitive performance, on which these competitors rely heavily. This observational study assessed the hydration state of esports players on a competition day and its possible associations with esports and lifestyle-related features.Methods: The hydration status of esports players was assessed on a tournament day through urine-specific gravity and by comparison with the Armstrong urine color chart. Binary logistic regression and univariate analysis of variance were applied to assess the relationships between urine-specific gravity and age, BMI, hours of sleep per day, hours of video game play per day, esports title, physical activity level, and professionalism level.Results: Ninety-eight esports players participated in this study. The average urine-specific gravity, assessed through refractometry, was 1.020 (SD = 0.007) g/cm³. 10.2% were classified as well hydrated, 25.5% with minimal dehydration, 60.2% with significant dehydration, and 4.1% with serious dehydration. Considering the eight-color urine chart method, 16.3% were classified with minimal dehydration, 65.3% with significant dehydration, and 18.4% as serious dehydration. There were no significant associations between hydration status and lifestyle-related variables (p > 0.05). The results of the two methods of assessing hydration status presented a positive, moderate, and statistically significant correlation (r = 0.711, p < 0.001). The agreement between the two classifications was 56.1%, with Cohen’s kappa showing a weak agreement (k = 0.213, p < 0.001) even if with linear (k = 0.330, p < 0.001) or quadratic (k = 0.471, p < 0.001) weighting.

The Synergistic Effect of Water Reducer and Water-Repellent Admixture on the Properties of Cement-Based Material

Water reducer and water-repellent admixture are very important in improving the workability and durability of cement-based materials. However, the synergistic effect of the two types of admixtures has not been well investigated. In this study, polycarboxylate ether-based superplasticizer (PCE) and octyltriethoxysilane (OTS) were adopted as water reducer and water-repellent admixture, respectively. Their synergistic effect on the fluidity, compressive strength, and water absorption rate of cement-based materials was investigated. Particularly, the pore structure and hydration state of cement paste were analyzed using 1H Low-Field Nuclear Magnetic Resonance (1H LF NMR). The result showed that the fluidity of cement paste containing different dosages of PCE was reduced by 5–10 mm by incorporating 1% OTS, and the compressive strength at the early age of 3 d of mortar containing high PCE dosage of 0.25% decreased up to 15% by using 1% OTS. In contrast, the compressive strength of mortar containing 0.20% PCE was slightly enhanced by the addition of 1% OTS. 1H LF NMR analysis revealed that the combination of PCE and OTS would increase the pore size and total pore volume of cement paste, and more bleeding water would be generated at high PCE dosage. The intensity-weighted T2 values of the main peak (T2¯) implied that both PCE and OTS produced a retardation effect on cement hydration. However, the water absorption rate decreased by 46.6% despite the increase in pore size and total pore volume. The conflict phenomenon powerfully revealed that the internal hydrophobic treatment by OTS has been successfully achieved. Overall, the combination of 0.20% PCE and 1% OTS exerted a positive synergistic effect in improving the compressive strength and water-repelling ability of cement-based materials, which is meaningful for improving their durability and service life.

The Unusual Functional Role of Protein Flexibility in Photosynthetic Light Harvesting: Protein Dynamics Studied Using Neutron Scattering

In addition to investigations of the three-dimensional protein structure, information on the dynamical properties of proteins is indispensable for an understanding of protein function in general. Correlations between protein dynamics and function are typically anticipated when both molecular mobility and function are concurrently affected under specific temperatures or hydration conditions. In contrast, excitation energy transfer within the major photosynthetic light-harvesting complex II (LHC II) presents an atypical case, as it remains fully operational even at cryogenic temperatures, primarily depending on the interactions between electronic states and involving harmonic protein vibrations only. This review summarizes recent work on vibrational and conformational protein dynamics of LHC II and directly relates these findings to its light-harvesting function. In addition, we give a comprehensive introduction into the use of neutron spectroscopy and molecular dynamics simulations to investigate the protein dynamics of photosynthetic protein complexes in solution, which is information complementary to that obtained by protein crystallography.

Nanocomposite polyphenyleneoxide with amino-functionalized silica: structural characterization based on thermal analysis

AbstractA polymer nanocomposite based on sulfonated polyphenylene oxide with amino-functionalized mesoporous silica was designed, synthesized, and tested as a new material for proton exchange membrane (PEM preparation. Characterization of the intermediate and final products of synthesis was realized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and thermal analysis. Broadband Dielectric Spectroscopy (BDS) was used to determine dielectric properties including ionic conductivity. Thermogravimetric analysis has provided important information regarding the composition and thermal stability of the three compounds, subject to thermal degradation: 1) the amino-silica with cetyltrimethylammonium bromide (CTAB) template inside the pores (MS-NH2I), 2) the mesoporous amino-silica after removing the template (MS-NH2II) and 3) the polymer nanocomposite (sPPO-MS-NH2). The thermal decomposition of the composite samples occurs in three stages: in the first, up to 150 °C, water and organic solvents were lost; the second stage, between 200-300 °C, was due to breaking the organic functionalities (-NH2, amino and -SO3H, sulfonic acid), and the third stage, above 400 °C was due to polymer chain degradation. The final residue at 700 °C reflects the contribution of inorganic silica. The proton conductivity, for polymeric (sPPO) and composite (sPPO-MS-NH2) membranes was determined from BDS dates, both in dry and hydrated states. For dried samples, the higher values of proton conductivities were: 0.16 mS cm−1 (sPPO, 70 °C) and 0.03 mS cm−1 (sPPO-MS-NH2, 120 °C), and the higher values of proton conductivity increased for the hydrated samples with two orders of magnitude: 36.5 mS cm−1 (sPPO, 40 °C) and 22.4 mS cm−1 (sPPO-MS-NH2, 50 °C). However, the proton conductivity is still dependent on the hydration state, even for the composite membrane.

Geological analysis of the hydro-mechanical responses of Opalinus claystone to excavation-induced damage via engineering

In the realm of engineering geology, specifically concerning the containment of high-level radioactive waste, this study examines the excavation-induced damage zone (EDZ) in underground drifts and its evolution, which is critical for the effectiveness of underground repositories. The focus is on the self-sealing capability of the EDZ in Opalinus claystone (OPA) under mechanical compression and hydration induced by a bentonite core sealing component post-nuclear waste emplacement. This core applies a swelling pressure of 5 MPa to the drift walls during resaturation, affecting repository integrity. Using numerical modeling, this study pioneers the simulation of real-time self-sealing mechanisms in OPA, a crucial geological barrier in nuclear waste containment. The approach integrates a plastic damage model with an auxiliary deformation model and Biot’s model to accurately depict moisture-dependent OPA deformation. This modeling is essential for understanding claystone geomechanics in nuclear waste repositories. Detailed post-analysis of crack features and unsaturated fractured OPA permeability, following fracture energy regularization principles and the cubic law, provides insights into the geotechnical properties of the EDZ, enhancing the accuracy of geological forecasts in nuclear waste management. The model’s reliability is confirmed through various numerical simulations, including triaxial compression tests, observations of swelling deformations due to moisture variations, and comprehensive water permeability tests assessing the self-sealing efficiency of fractured OPA during water injection. In situ experiments at the Mont Terri Rock Laboratory support these findings, particularly regarding EDZ self-sealing under combined mechanical and hydration conditions. Comparative analysis of numerical results and experimental data validates the model’s ability to replicate fractured OPA self-sealing behavior, crucial for assessing nuclear waste repository safety and effectiveness. Effective self-sealing is underscored by reduced water permeability in the EDZ during resaturation, affirming the model’s relevance in evaluating nuclear waste containment strategies. Moreover, insights from this model extend to assessing CO2 migration, given claystones’ role as caprocks in CO2 geological sequestration schemes, thereby enhancing its importance in long-term environmental safety evaluations for both nuclear waste and CO2 storage scenarios.

Ionic Polybenzimidazoles Crosslinked through Thiol-Ene Reactions for Anion Exchange Membranes

This research introduces a study outlining the synthesis and characteristics of innovative anion exchange membranes that utilize m-polybenzimidazole (m-PBI) as the polymer backbone structure. These membranes incorporate quaternary ammonium groups and alkene groups as side chains. These ionic m-PBI membranes were further crosslinked through thermal thiol-ene reactions. By adeptly manipulating the quantities of attached quaternary ammonium groups and alkene groups, the ion exchange capacity (IEC) values and crosslinking degrees were independently controlled. A comprehensive range of m-PBI based anion exchange membranes was developed, showcasing IEC values ranging from 1.51 to 2.50 mmol/g. This series of membranes demonstrated hydroxide conductivity levels ranging between 14 and 58 mS/cm at an operational temperature of 80 °C. Particularly noteworthy is the comparison between membranes with similar IEC values: the crosslinked membranes exhibited reduced water absorption while effectively maintaining a level of hydroxide conductivity comparable to that of uncrosslinked membranes. Moreover, the crosslinked membranes exhibited enhanced dimensional stability. An intriguing finding emerged from a crosslinked membrane with an IEC value of 2.46 mmol/g, which retained a remarkable 84% of its original hydroxide conductivity after being immersed in a 1.0 M sodium hydroxide solution at 60 °C for a duration of 720 hours. These membranes demonstrated mechanical strength even in their hydrated state, exhibiting tensile strengths ranging from 10.8 to 14.6 MPa. Given their heightened hydroxide conductivity, improved resistance to alkaline conditions, and favorable mechanical attributes, the crosslinked ionic m-PBIs emerge as promising candidates for anion exchange membranes in fuel cell applications. Keywords ; anion exchange membranes, crosslinking reaction, polybenzimidazole, back titration, mechanical strength.

Intrinsically Microporous Ion-Pair Membranes for HT-PEMFCs

Fuel cells are electrochemical devices with high energy efficiency expected to be applied economically and eco-friendly across various energy sectors. Low-temperature polymer electrolyte membrane fuel cells (LT-PEMFCs) using Nafion operates at a relatively low operating temperature (60-80°C) and fully hydration condition. HT-PEMFC is operable at high temperatures (140-180°C), but requires anhydrous conditions to avoid loss of doped phosphoric acid (PA). In this presentation, polymer membranes designed through with intrinsic microporosity were synthesized through super acid polycondensation. We demonstrated that high proton conductivity (106.33 mS cm-1 at 180℃) is obtained by forming phosphoric acid filled ion-channels within the interconnected microporous structure. Moreover, ion-pair coordinated PIMs are fabricated by methylation of PIMs to improve PA retention even under humidified conditions. It is suggested that the water tolerance of ion-pair coordinated PIMs is improved and can be operated under various conditions regardless of humidification and operating temperature and exceptional membrane electrode assembly performance and durability achieved even under humidified reformate gas conditions.

Investigation of the State of Hydration of a Non-Stoichiometric Hydrate in a Low Dose Formulation Using 19F Solid-State NMR

A variable or non-stoichiometric hydrate of GDC-4379 was developed into a formulated capsule with a 1% drug loading. The water content of this hydrate varied from 0-0.7 moles over the relative humidity (RH) range of 0-98% (25°C). Since a variable state of hydration coupled with rapid equilibration of lattice water with the environmental RH can lead to challenges in formulation development, an analytical method to directly and accurately determine the state of hydration of the active in such a low dose formulation was deemed necessary. Owing to its high selectivity and fast acquisition times, 19F solid-state NMR was effectively utilized to directly determine the lattice water content of the active in the formulated capsule. By correlating Δδ, the chemical shift difference between the isotropic peaks, with the relative humidity and ultimately the lattice water content, the state of hydration of GDC-4379 in the formulated capsule was experimentally determined as 0.63 moles of water/mole of anhydrate.

Experimental and Modeling Study on Methane Hydrate Equilibrium Conditions in the Presence of Inorganic Salts.

The aim of this study was to determine the influence of four inorganic salts, KCl, NaCl, KBr and NaBr, on the thermodynamic conditions of methane hydrate formation. In order to achieve this, the vapor-liquid water-hydrate (VLWH) equilibrium conditions of methane (CH4) hydrate were measured in the temperature range of 274.15 K-282.15 K by the isothermal pressure search method. The results demonstrated that, in comparison with deionized water, the four inorganic salts exhibited a significant thermodynamic inhibition on CH4 hydrate. Furthermore, the inhibitory effect of Na+ on methane hydrate is more pronounced than that of K+, where there is no discernible difference between Cl- and Br-. The dissociation enthalpy (∆Hdiss) of CH4 hydrate in the four inorganic salt solutions is comparable to that of deionized water, indicating that the inorganic salt does not participate in the formation of hydrate crystals. The Chen-Guo hydrate model and N-NRTL-NRF activity model were employed to forecast the equilibrium conditions of CH4 hydrate in electrolyte solution. The absolute relative deviation (AARD) between the predicted and experimental values were 1.24%, 1.08%, 1.18% and 1.21%, respectively. The model demonstrated satisfactory universality and accuracy. This study presents a novel approach to elucidating the mechanism and model prediction of inorganic salt inhibition of hydrate.

Effective approach to predict soil-water retention curve of bentonites considering adsorption and capillarity

Understanding soil–water retention behavior is a longstanding topic. Water retained in soils can be decomposed into adsorptive and capillary components, controlled by different physicochemical mechanisms. The capillary water retention was frequently discussed in literatures, but the adsorption role was rarely considered, especially for high active clays (e.g., bentonite). In this study, two novel equations for quantifying adsorptive and capillary water retentions are proposed, generating a twofold model to continuously simulate soil–water retention behavior of bentonites. Only 5 parameters, i.e., the maximum adsorption capacity, characteristic adsorptive and capillary suctions, and uniformities of adsorptive and capillary pores, are defined with clear physical meanings. A graphical method was suggested to firstly determine the maximum adsorption capacity, and the remaining parameters are efficiently estimated by non-linear curve fitting. The water retention data for various bentonites, representing a variety of hydration conditions, initial compactness, montmorillonite content and suction range, are used to assess the model performance. The predictions agree well with the measured total, adsorptive and capillary water contents of a Wyoming bentonite, and the fitting curves also match well with test data for other bentonites over the full suction range. Adsorption parameters are distributed within a narrow range, while the characteristic capillary suction is also distributed within a limited range under constant volume condition. The proposed model allows reasonable predictions about the capillary onset and the transition from adsorption to capillarity, revealing obvious superiority by comparison with other hybrid models. This work offers a new pathway to quantitively assess the soil–water retention curve of high active clays.

Water dynamics in calcium silicate hydrates probed by inelastic neutron scattering and molecular dynamics simulations

Calcium-silicate-hydrate (C-S-H) is a disordered, nanocrystalline material, acting as a primary binding phase in Portland cement. C-S-H and C-A-S-H (an Al-bearing substitute present in low-CO2 cement) contain thin films of water on solid surfaces and inside nanopores. Water controls multiple chemical and mechanical properties of C-S-H, including drying shrinkage, ion transport, creep, and thermal behavior. Therefore, obtaining a fundamental understanding of its properties is essential. We applied a combination of inelastic incoherent neutron scattering and molecular dynamics simulations to unravel water dynamics in synthetic C-(A)-S-H conditioned at five hydration states (from drier to more hydrated) and with three Ca/Si ratios (0.9, 1, and 1.3). Our results converge towards a picture where the evolution from thin layers of interfacial water to bulk-like capillary water is dampened by the structure of C-(A)-S-H. In particular, the hydrophilic Ca2+ sites organize the distribution of interfacial C-(A)-S-H water.

The Utilization of Brillouin Microscopy in Corneal Diagnostics: A Systematic Review.

Corneal biomechanical data has been used since 2005 to screen for keratoconus and corneal ectasia by corneal specialists. Older technology uses force applanation techniques over a 3 mm area in the central cornea, making it highly dependent on extraneous variables and unable to calculate the elasticity of the tissue. Brillouin microscopy is a newer method that uses a natural shift in the frequency of light as it passes through a material. This frequency shift can be used to estimate the viscoelasticity of the tissue. The advantage of Brillouin microscopy is that it can create a full three-dimensional (3D) map of the entire cornea without direct contact. A literature search was conducted using the databases PubMed, Google Scholar, and Ovid regarding the applications of Brillouin microscopy in corneal diagnostics. A final total of 16 articles was included describing the various ex vivo and in vivo studies conducted using Brillouin microscopy. Applications of this technology spanned from keratoconus diagnosis to post-corneal refractive surgery evaluation. All studies evaluated corneal biomechanics and other corneal properties through the quantification of Brillouin frequency shifts. Many of the studies found that this diagnostic device is capable of detecting subtle changes in corneal thickness and biomechanics in keratoconic corneas at a high level of specificity and sensitivity. However, limitations of Brillouin microscopy may include the duration of time required for use and fluctuations in accuracy depending on the corneal hydration state. Future technology seems to be geared towarda combination of optical coherence tomography (OCT) and Brillouin microscopy, using OCT as a three-dimensional pupil-tracking modality. Further research and understanding of the technology involved will lead to better care of patients in the field of ophthalmology.

Hydration State Throughout Porcine Lumbar Intervertebral Discs: Comparing Fresh and Frozen-Thawed Specimens.

Water content in intervertebral discs (IVDs) is essential for physiological and mechanical function. Freezing post-mortem tissue prior to biomechanical testing is a common practice to prevent tissue degradation, but this process has been theorized to alter hydration within IVDs. The hydration state throughout porcine lumbar IVDs, a common lumbar surrogate, is unknown as are the effects of freezing on porcine IVD hydration. Nineteen porcine lumbar spines were stored in one of the three conditions: frozen (- 20 °C) wrapped in saline-soaked gauze, frozen (- 20 °C) without saline, or fresh. Water content was measured in four disc regions within each of 89 discs: nucleus pulposus (NP), inner (AF-A), intermediate (AF-B), and outer (AF-C) annulus fibrosus. A three-factor, repeated measure analysis of variance was conducted for storage condition, spinal level, and repeated measure disc region. No significant differences were observed in spinal level or storage condition as a main effect. Mean hydration was significantly different in each disc region with mass percentage of water found to be 88.8 ± 1.7% in NP, 79.6 ± 3.8% in AF-A, 71.9 ± 3.7% in AF-B, and 62.3 ± 3.3% in AF-C. No significant differences were shown in NP and AF-C regions between storage conditions. Two significant differences in storage condition were observed in AF-A and AF-B regions, but there is likely no biological difference in these populations. Water content throughout porcine lumbar IVD was determined and results suggest one freeze-thaw cycle at - 20 °C does not alter the overall hydration within the porcine lumbar IVD.

Liquid-Liquid Phase Separation Mediated Formation of Chiral 2D Crystalline Nanosheets of a Co-Assembled System.

The role of macromolecule-macromolecule and macromolecule-H2O interactions and the resulting perturbation of the H-bonded network of H2O in the liquid-liquid phase separation (LLPS) process of biopolymers are well-known. However, the potential of the hydrated state of supramolecular structures (non-covalent analogs of macromolecules) of synthetic molecules is not widely recognized for playing a similar role in the LLPS process. Herein, LLPS occurred during the co-assembly of hydrated supramolecular vesicles (bolaamphiphile, BA1) with a net positive charge (zeta potential, ζ = +60 ± 2mV) and a dianionic chiral molecule (disodium l-[+]-tartrate) is reported. As inferred from cryo-transmission electron microscopy (TEM), the LLPS-formed droplets serve as the nucleation precursors, dictating the structure and properties of the co-assembly. The co-assembled structure formed by LLPS effectively integrates the counter anion's asymmetry, resulting in the formation of ultrathin free-standing, chiral 2D crystalline sheets. The significance of the hydrated state of supramolecular structures in influencing LLPS is unraveled through studies extended to a less hydrated supramolecular structure of a comparable system (BA2). The role of LLPS in modulating the hydrophobic interaction in water paves the way for the creation of advanced functional materials in an aqueous environment.

Process integration and techno-economic assessment of crystallization techniques for Na2SO4 and NaCl recovery from saline effluents

Saline effluents containing primarily sodium chloride (NaCl) and sodium sulfate (Na2SO4) are generated from common salt production, tannery CETPs, textiles industries, desalination rejects, etc. In this work, experimental studies have been conducted for parametric evaluation of crystallization techniques for selective isolation of Na2SO4 and NaCl from saline effluent. Three crystallization approaches, i.e., evaporation-crystallization, cooling-crystallization, and antisolvent-crystallization, are assessed through parametric studies. A representative saline solution generated from a salt refinery unit is considered for the study. Lab-scale experiments were performed to determine the optimum process conditions for each crystallization process, and their performance was evaluated by estimating the separation efficiency. Chemical, P-XRD, and TGA analyses were performed to characterize the product composition, purity, and hydration state. For selective Na2SO4 recovery, cooling crystallization, and antisolvent crystallization were found suitable over evaporation crystallization. Subsequently, integrated process variants for cooling crystallization and antisolvent crystallization-based separation were developed. A techno-economic assessment (TEA) was performed to compare integrated process variants for the recovery of salts (Na2SO4 and NaCl) and establish the prospective towards commercialization. The parametric evaluation and TEA shows that the combined crystallization technologies can be potential approach to recover added-value products from saline effluents promoting waste to wealth notion.

The Cognitive Function and Taekwondo-Specific Kick Performance of Taekwondo Athletes at Different Hydration Statuses.

Successful participation in taekwondo (TKD) requires athletes to possess quick decision-making abilities and demonstrate technical proficiency during competition. Dehydration, occurring during both training and competition, is widely recognized to have various negative effects. This study investigated the impact of different levels of dehydration on cognitive function, as measured by the Vienna Test System, and the specific performance of kicking techniques among TKD athletes. Using a randomized crossover design, 12 participants were involved in the study. Before and after 1 hour of training at 80% of maximal heart rate, participants were weighed and provided urine samples. All participants were randomly assigned to 3 different hydration conditions: the euhydrated (EUH) group had unrestricted access to fluid consumption, while the hypohydrated (HYP) and severelyHYP (S-HYP) groups experienced reductions of 2.0% and 4.0% of their initial body weight, respectively. The EUH group exhibited better reaction speed in reaction-time test-form S1 than the HYP and S-HYP groups. Notably, the EUH group demonstrated a significantly higher success rate in the front-side kick (EUH 98%, HYP 90%, S-HYP 88%; P < .05). However, the success rates of back roundhouse kick and free head kick were similar among the 3 statuses. Furthermore, postexercise heart rates were found to be significantly higher in the HYP and S-HYP groups compared with the EUH group. This study provides insight into the negative effects of dehydration on cognitive function and TKD-specific performance. It is recommended that TKD athletes maintain optimal hydration levels during training and competition to ensure optimal performance.

Characterizing Hydrated Sulfates and Altered Phases in Jezero Crater Fan and Floor Geologic Units With SHERLOC on Mars 2020

AbstractThe Mars 2020 Perseverance rover has explored fluvio‐lacustrine sedimentary rocks within Jezero crater. Prior work showed that igneous crater floor Séítah and Máaz formations have mafic mineralogy with alteration phases that indicate multiple episodes of aqueous alteration. In this work, we extend the analyses of hydration to targets in the Jezero western fan delta, using data from the SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) Raman spectrometer. Spectral features, for example, sulfate and hydration peak positions and shapes, vary within, and across the crater floor and western fan. The proportion of targets with hydration associated with sulfates was approximately equal in the crater floor and the western fan. All hydrated targets in the crater floor and upper fan showed bimodal hydration peaks at ∼3,200 and ∼3,400 cm−1. The sulfate symmetric stretch at ∼1,000 cm−1 coupled with a hydration peak at ∼3,400 cm−1 indicate that MgSO4·nH2O (2 &lt; n ≤ 5) is a likely hydration carrier phase in all units, perhaps paired with low‐hydration (n ≤ 1) amorphous Mg‐sulfates, indicated by the ∼3,200 cm−1 peak. Low‐hydration MgSO4·nH2O (n = 1–2) are more prevalent in the fan, and hydrated targets in the fan front only had one peak at ∼3,400 cm−1. While anhydrite co‐occurs with hydrated Mg‐sulfates in the crater floor and fan front, hydrated Ca‐sulfates are observed instead at the top of the upper fan. Collectively, the data imply aqueous deposition of sediments with formation of salts from high ionic strength fluids and subsequent aridity to preserve the observed hydration states.

Misleading Pore Size Measurements in Gelatin and Alginate Hydrogels Revealed by Confocal Microscopy.

It is a well-documented phenomenon that the porous structure of hydrogels observed with vacuum-based imaging techniques is generated during the freezing and drying process employed prior to observation. Nevertheless, vacuum-based techniques, such as scanning electron microscopy (SEM), are still being commonly used to measure pore sizes in hydrogels, which is often not representative of the actual pore size in hydrated conditions. The frequent underestimation of the impact of freezing and drying on hydrogel structures could stem from a lack of cross-fertilization between materials science and biomedical or food science communities, or from the simplicity and visually appealing nature of SEM imaging, which may lead to an overemphasis on its use. Our study provides a straightforward and impactful way of pinpointing this phenomenon exploiting two hydrogels ubiquitously applied in tissue engineering, including gelatin methacryloyl and alginate as proof-of-concept hydrogels. By comparing images of the samples in the native hydrated state, followed by freezing, freeze-drying, and rehydration using SEM and confocal microscopy, we highlight discrepancies between hydrogel pore sizes in the hydrated versus the dry state. To conclude, our study offers recommendations for researchers seeking insight in hydrogel properties and emphasizes key factors that require careful control when using SEM as a characterization tool.