High Hydration Levels Research Articles

Heat-dried sclerotia of Sclerotinia sclerotiorum myceliogenically germinate in water and are able to infect Brassica napus

The phytopathogenic fungus Sclerotinia sclerotiorum forms dormant structures (termed sclerotia) that germinate myceliogenically under certain environmental conditions. During myceliogenic germination, sclerotia produce hyphae, which can infect leaves or stems of host plants directly from the ground; this is termed basal infection. This study determined which abiotic conditions were most important for promoting myceliogenic germination of sclerotia in vitro. A high sclerotium hydration level and low incubation temperature (15°C) improved mycelial growth in the presence of a nutrient source. Sclerotia incubated without a nutrient source on moist sand, vigorously myceliogenically germinated most frequently (63%) when they had been previously imbibed and then conditioned at −20°C. By far the most consistent amount of vigorous myceliogenic germination (>75%) was produced when sclerotia were heat-dried before being submerged in water. The hyphae of these sclerotia were shown to infect and proliferate on leaves of intact Brassica napus plants. This research provides a better understanding of the abiotic conditions that are likely to increase the risk of basal infection by S. sclerotiorum.

Utilidad del índice de masa corporal en pacientes con enfermedad renal crónica

Introducción: El índice de masa corporal es un indicador que se utiliza frecuentemente para identificar el sobrepeso y la obesidad en los adultos. En la población con enfermedad renal crónica, estudios de observación han reportado resultados contradictorios acerca de la asociación entre la obesidad y la mortalidad. También, diferentes autores, han observado como aquellos que presentan un índice de masa corporal elevado, demuestran un mejor estado nutricional. Objetivo: Analizar el índice de una masa corporal de los pacientes en hemodiálisis y su relación con las complicaciones. Material y Método: Estudio observacional, analítico y longitudinal. La muestra estuvo compuesta por 170 pacientes prevalentes en tratamiento con hemodiálisis o hemodiafiltración online. Se calculó el índice de masa corporal en base al peso real y la talla del paciente en el momento de la recogida de datos. Se registraron los pacientes que causaron éxitus durante el periodo de seguimiento. Resultados: Los pacientes fallecidos presentaban un índice de masa corporal menor, aunque las diferencias no resultaron estadísticamente significativas. Los pacientes que cumplieron el objetivo de índice de masa corporal, presentaron también mayores niveles de sobrehidratación, un menor índice de tejido graso, menores niveles de transferrina en sangre, un mayor Kt/ve y un mayor número de meses en terapia renal sustitutiva. Conclusiones: Un índice de masa corporal = 25 kg/m² no se asoció en nuestro caso con una mayor mortalidad, aunque si se observa una tendencia en los datos en ese sentido. Los pacientes con un índice de masa corporal = 25 kg/m² presentaban un mejor estado nutricional.

Atomistic simulation study of the hydrated structure and transport dynamics of a novel multi acid side chain polyelectrolyte membrane

Perfluoroimide acid (PFIA) belongs to a new class of Multi Acid Side Chain (MASC) polyelectrolyte membranes. Classical molecular dynamics simulations were carried out to study the hydrated nanostructure of PFIA and transport of water molecules and hydronium ions at T = 300 K and T = 353 K for a range of hydration levels. The radial distribution functions showed negligible change with temperature. The PFIA chain radius of gyration was minimally influenced by hydration and temperature which makes it suitable for fuel cells. Our simulations showed the formation of a large continuous water phase cluster in PFIA at high hydration levels which has also been observed in conductive probe atomic force microscopy experiments. These large continuous clusters lead to significantly higher vehicular diffusion rates for water molecules and hydronium ions at higher hydration levels. The vehicular diffusivity constants for water molecules and hydronium ions for PFIA were comparable to those for Nafion at both T = 300 K and T = 353 K. The vehicular proton conductivity values for PFIA were observed to be higher than those for Nafion at both T = 300 K and T = 353 K which agrees qualitatively with the experimental trends.

Interfacial Water Drives Improved Proton Transport in Siliceous Nanocomposite Nafion Thin Films.

Nafion proton exchange membranes dehydrate when they are used in the gas phase and in high-temperature applications, such as fuel cells and (photo)electrolysis. Retaining a high level of membrane hydration under such conditions can be achieved by using inorganic fillers, but has never been demonstrated for thin films. Herein, several types of siliceous nanoparticles were incorporated for the first time into Nafion thin films. For composite Nafion materials, increased water uptake does not always induce increased proton conductivity. Here, increased water uptake did result in higher proton conductivity due to a synergistic effect within the composite film. The nanocomposites displayed a higher water uptake than could be expected based on the water uptake of the individual materials. Excess water present at the Nafion-filler interface was found to cause the proton conductivity of nanocomposite Nafion/Ludox AS-40 thin films to double compared with pristine Nafion at low relative humidity (from 2 to 4 mS cm-2 ). Knowledge about the properties of such interfaces will allow for the better design of self-humidifying nanocomposite Nafion membranes, films, and catalyst layers.

A New Class of Fuel Cells Based on Ion Pair-Coordinated Proton Exchange Membranes

Low temperature proton exchange membrane (PEM) fuel cells that use perfluorinated sulfonic acid are at present being commercialized in fuel cell vehicles, but these cells can operate only at relatively low temperatures, ca. < 100°C, and high hydration levels. High temperature PEM fuel cells that use phosphoric acid-doped polybenzimidazole can operate effectively up to 180°C; however, these are difficult to operate below 140°C without suffering loss of phosphoric acid when exposed to water.1 In this presentation, we discuss a new class of fuel cells based on ion pair-coordinated proton exchange membranes.2 In the ion pair-coordinated proton exchange membranes, quaternary ammonium functionalized membranes, also known as anion exchange membranes, are doped with phosphoric acid. Due to the high basicity of the quaternary ammonium hydroxide, the acidic proton of phosphoric acid is completely deprotonated to form a strong ionic interaction between quaternary ammonium and biphosphate. Our density functional theory calculation indicated that the ion-pair interaction is 8.5 times greater than the conventional acid base interaction in the phosphoric acid doped polybenzimidazole. The strong interaction between the ion pair enables fuel cell operation at lower temperatures with substantially higher water partial pressure than are possible for high-temperature phosphoric acid doped polybenimidazole fuel cells. In this presentation, the chemical structural difference between this new system and the conventional phosphoric acid-doped polybenzimidazole system will be compared. The benefits and challenges of the new system in fuel cell operations will be further discussed. Acknowledgment This work was supported by the US Department of energy, Energy Efficiency and Renewable Energy, Fuel Cell Technology Office (Program Manager: Dimitrios Papageorgopoulos). References G. Bendlamudi Systematic Characterization of HT PEMFCs Containing PBI/H3PO4 Systems: Thermodynamic analysis and Experimental Investigations 104 (Logos Verlag Berlin GmbH, 2011).Kwan-Soo Lee, Jacob S. Spendelow, Yoong-Kee Choe, Cy Fujimoto, and Yu Seung Kim Nature Energy, 1, 16120 (2016).

Effects of disulfide bridges and backbone connectivity on water sorption by protein matrices

Understanding the water sorption behavior of protein powders is important in applications such as the preservation of protein-based pharmaceuticals. Most globular proteins exhibit a characteristic sigmoidal water adsorption isotherm at ambient conditions. However, it is not well understood how water sorption behavior is influenced by intrinsic factors that are related to structural properties of proteins. We investigate computationally how structural constraints on proteins influence the water sorption isotherms of amorphous protein powders. Specifically, we study the effects of non-local disulfide linkages and backbone connectivity using pheromone ER-23 and lysozyme as model proteins. We find that non-local disulfide linkages can significantly restrict structural changes during hydration and dehydration, and this in turn greatly reduces the extent of hysteresis between the adsorption and desorption branches. Upon removing the backbone connectivity by breaking all peptide bonds in lysozyme, we find that the hysteresis shifts towards the lower humidity regime, and the water uptake capacity is significantly enhanced. We attribute these changes to the higher aggregation propensity of the constraint-free amino acids in dehydrated condition, and the formation of a spanning water network at high hydration levels.

Effect of oil and shortening in rice bread quality: Relationship between dough rheology and quality characteristics

This study showed that the type and quantity of fat added in rice based breads affect the bread quality in a different way. In general, it can be said that the incorporation of up to 20% oil improved rice based breads. Oil increased the specific volume, the a* and b* parameters of the crust and the cell density. It also decreases hardness, cohesiveness, springiness, resilience, and the L* parameter. Converse to breads made with oil, the addition of shortening can negatively affect the quality of the breads. Moreover, the correlation analysis has demonstrated that the study of dough rheology could be a good predictor of gluten-free bread quality.

Mitigation strategy towards stabilizing the Electrochemical Interface under high CO and H2O containing reformate gas feed

Despite the enhanced CO tolerance of the high temperature polymer electrolyte membrane (HT PEMFC) technology, the synergistic effect of CO and steam in the anodic reformate gas feed was proven to result in serious performance reduction and operation instabilities, due to the dynamic disturbance of the electrochemical interface (EI). In this work a mitigation strategy is presented by controlling the hydrophilicity of the catalytic layer in order to achieve the optimum structure of the EI. The thin and continuous film distribution of the phosphoric acid (PA) inside the catalytic layer (CL) without blocking the pores is the main characteristic property that determines the good quality of the EI. As shown, a hydrophilic catalytic layer is preferable, since the acid, being at any hydration level, will be able to spread over the catalytic surface aiming to the formation of a thin and continuous film so as to maximize the extend of the EI without blocking the pores of the catalytic layer. This facilitates the uninterrupted transport of protons and the fast diffusion of the reacting gases. Herein, this was accomplished by modifying the surface properties of the CL through the anchoring of pyridine moieties on the MWCNTs, which plays the role of the Pt catalyst support. The basic pyridine moieties enhance the hydrophilicity of the nanotubes through the acid (PA)-base (pyridine) interaction so that the contact angle between a PA drop and the catalytic layer is very close to zero. The good affinity of the PA with the pyridine based catalytic layer secures the PA thin film distribution and continuity. More importantly it is not affected even at high hydration levels of the PA, when the partial pressure of steam is increased at values>20kPa. Otherwise, on conventional C supports, hydrated PA has the tendency to shrink and create ganglia leading to the disruption of the EI. The pyridine modified catalytic layers approach Pt surface utilization values as high as 80% as compared to 50% utilization measured for the case of conventional Pt/C catalytic layers.

Hydrated proton self-diffusion study in ion-exchange membranes by MRI and impedance spectroscopy

Average self-diffusion coefficients of hydrated protons in sulfonated poly (ether sulfone) (SPES), Interpolymer and Nafion 117 membranes are measured by impedance spectroscopy and pulsed field gradient nuclear magnetic resonance (PFG NMR). Self-diffusion coefficient measured by impedance spectroscopy shows two patterns, one is at the low hydration states, i.e. λ = 2–4 and another at the high hydration states (starting from λ = 4). At lower hydration states the diffusion values increases slowly while steep increment is found at higher hydration level. PFG NMR shows similar trend throughout the measurements. The diffusion coefficients at higher temperatures are higher than at lower temperatures as a function of λ for SPES membrane. At the same value of λ, hydrated proton self-diffusion coefficient is found to be increased by 18% from 295.5 to 303 K. The thermo-mechanical properties of the membranes characterised by the means of DSC, TGA and DMA analysis show SPES, stable up to 450 °C and can be used for the high-temperature applications.

Triticale extrudates – Changes of macrostructure, mechanical properties and molecular water dynamics during hydration

The effect of hydration (in the range of aw 0.981–0.090) on changes of macroscopic and mechanical features of triticale snacks produced in different conditions (feed moisture - 16 and 20%; extrusion temperature - 135 and 175 °C) was analysed. Changes of snacks depended both on the hydration level and the extrusion process conditions.As a result of storage at the highest hydration level (aw = 0.981) contraction of snacks was observed. The shrinkage was more pronounced in case of extrudates obtained from raw material containing 16% of water regardless of the extrusion temperature. The hardness of extrudates depended both on the feed moisture and hydration. Samples obtained from the raw material containing 20% moisture were harder than those prepared at the feed moisture of 16%. Based on the results of molecular dynamics study by low field NMR technique, a model of hydration was developed and critical hydration value of extruded snacks was calculated. Higher values of the critical hydration were obtained for snacks extruded at temperature 135 °C than for those obtained at 175 °C. The feed moisture level affected critical hydration values to a lesser extent. Obtained results suggest that the state of water in extrudates depends on extrusion process conditions.

Extreme dehydration observed in Antarctic Turgidosculum complicatulum and in Prasiola crispa.

Gaseous phase hydration effect of extremely dehydrated thallus of the Antarctic lichenized fungus Turgidosculum complicatulum and of green alga Prasiola crispa was observed using hydration kinetics, sorption isotherm, 1H-NMR spectroscopy and relaxometry. Three bound water fractions were distinguished: (1) very tightly bound water, (2) tightly bound water and (3) a loosely bound water fraction detected at higher levels of hydration. Sorption isotherm was sigmoidal in form and well fitted using Dent model. The relative mass of water saturating primary water binding sites was ΔM/m 0=0.055 for T. complicatulum and ΔM/m 0=0.131 for P. crispa. 1H-NMR free induction decays (FIDs) for T. complicatulum and for P. crispa were superpositions of a solid signal component, and one averaged liquid signal component for P. crispa thallus ([Formula: see text] ≈ 80µs) or two liquid signal components coming from a tightly bound ([Formula: see text]≈ 71µs) and from a loosely bound water fraction ([Formula: see text]≈ 278µs) for T. complicatulum. 1H-NMR spectra recorded for T. complicatulum and for P. crispa thalli revealed one averaged mobile proton signal component L. The total liquid signal component expressed in units of solid (L 1+L 2)/S suggests the presence of water soluble fraction in T. complicatulum thallus.

The Influence of the Hofmeister Bias and the Stability and Speciation of Chloridolanthanates on Their Extraction from Chloride Media

ABSTRACTThe possibility of recovering rare earth elements from solutions containing their chloridometalate anions [LnClx](x−3)− via the process: LnClx(x−3)− + (x − 3)Lorg + (x–3)H+ ⇌ [(LH)x−3LnClx]org has been tested using 2-(1,3-bis(hexylamino)-1,3-dioxopropan-2-yl)-4,6-di-tert-butylpyridine (PMA), tri-n-butylphosphate (TBP), and tri-n-octylamine (TOA), which are known to be strong extractants for transition metal chloridometalates. While DFT calculations indicate that the formation of the neutral assembly [(PMAH)3LaCl6] in the gas phase is favorable, no uptake of La(III) from 6 M HCl by toluene solutions of PMA (or of TBP or TOA) was observed in solvent extraction experiments. Successful uptake of the [PtCl6]2− dianion by PMA and the failure to extract the [IrCl6]3− trianion under the same conditions indicate that the higher hydration energy of the latter makes transfer to the toluene solution less favorable and that this militates against extraction of La(III) chlorido complexes carrying charges of −3 or larger in which all the inner-sphere water molecules have been replaced. Computational results confirm literature observations that, in contrast to transition metal trications, formation of REE metalate anions such as [LnClx](x−3)− is not very favorable, particularly so for chloride, compared with nitrato or sulfato systems. Also, they indicate that the formation of outer-sphere assemblies such as {[La(H2O)9]·xCl} in which water ligands are retained in the inner sphere, H-bonded to anions, is more stable than inner-sphere complexes containing an equivalent number of anions. The high level of hydration of such species disfavors their transfer into nonpolar water-immiscible solvents. It is unlikely that recovery of [LnClx](x−3)− from acidic solutions can be achieved efficiently using currently available anion exchange extractants operating in a “pH-swing” process. Receptors giving very high binding energies to chloridolanthanates will be needed to offset the high dehydration energies required.

Molecular dynamics simulation of water permeation through the Nafion membrane

ABSTRACTIn this paper, the process of water permeation through Nafion membrane is investigated in the atomistic scale. Classic molecular dynamics (MD) simulation is carried out to determine the diffusion of water through the Nafionmembrane. Interfacial transport is investigated with non-equilibrium MD simulation. Results indicate that the self-diffusion coefficients increase linearly with water content and agree well with the nuclear magnetic resonance (NMR) experimental results. The interfacial transport coefficients weakly depend on the water contents for high hydration levels and the interfacial resistance can be neglected compared with the diffusion resistance.

STRUCTURE-TRANSPORT RELATIONSHIP OF PERFLUOROSULFONIC-ACID MEMBRANES IN DIFFERENT CATIONIC FORMS

Perfluorosulfonic-acid (PFSA) ionomers are widely used as solid electrolytes and ion-exchange membranes in electrochemical devices, wherein their properties are impacted by the interactions among the anionic sulfonate groups, mobile counter-ions (cations), and hydration levels. Cation-form and humidity collectively affect the structure/transport-property relationship, yet their interplay is still not well known. In this paper, we report changes in water uptake and conductivity of cation-exchanged PFSA in both vapor and liquid water, which are then correlated with changes in mechanical properties and nanostructure (hydrophilic-domain spacing and phase-separation). It is found that the magnitude of changes depends significantly on the membrane water content, with master curves in terms of water volume fraction and water per charge realized. Moreover, membrane nanostructure and dynamical-mechanical behavior is examined to establish structure/transport and transport/stability relationships. It is found that with increasing cation size (radius) and valence, the storage modulus increases, while the water uptake and conductivity decrease. In addition, regardless of the cation type, a universal relationship is found between the conductivity and modulus, indicative of a transport/stability tradeoff. The extent to which the cations impact the transport properties depends on the water content: at low hydration levels the controlling factor is the cation (and its interaction with the sulfonate sites), at increasing hydration the dominant factor becomes water volume fraction, although it is also controlled by the cations. Similarly, the decrease in hydrophilic domain spacing of PFSA exchanged with larger cations scales with cation radius at low water contents, but with Lewis acid strength (LAS) at higher hydration levels. The findings reported here not only provide valuable insights into the interaction between sulfonate groups, cations, and water surrounding these ionic groups, but also for understanding cation contamination in fuel cells and redox flow batteries.

An operationally flexible fuel cell based on quaternary ammonium-biphosphate ion pairs

Fuel cells are promising devices for clean power generation in a variety of economically and environmentally significant applications. Low-temperature proton exchange membrane (PEM) fuel cells utilizing Nafion require a high level of hydration, which limits the operating temperature to less than 100 ∘C. In contrast, high-temperature PEM fuel cells utilizing phosphoric acid-doped polybenzimidazole can operate effectively up to 180 ∘C; however, these devices degrade when exposed to water below 140 ∘C. Here we present a different class of PEM fuel cells based on quaternary ammonium-biphosphate ion pairs that can operate under conditions unattainable with existing fuel cell technologies. These fuel cells exhibit stable performance at 80–160 ∘C with a conductivity decay rate more than three orders of magnitude lower than that of a commercial high-temperature PEM fuel cell. By increasing the operational flexibility, this class of fuel cell can simplify the requirements for heat and water management, and potentially reduce the costs associated with the existing fully functional fuel cell systems. There is intensive research underway into the development of fuel cells. Here, the authors present a proton exchange membrane fuel cell based on quaternary ammonium-biphosphate ion pairs, offering promising performance under a wide range of conditions that are unattainable with conventional technologies.

Computational study of inelastic neutron scattering vibrational spectra of water clusters and their relevance to hydration water in proteins

BackgroundInelastic neutron scattering (INS) vibrational spectra for hydration water in proteins can be obtained from spectral differences, but their interpretation has mainly been limited to comparisons with various forms of ice at high hydration levels without making use of available structural information from neutron protein crystallography. MethodsThe INS vibrational spectra of free and partially constrained water clusters (up to n=17) were calculated with DFT methods using published energy-minimized structures. ResultsReference is made to neutron diffraction studies of hydrated proteins, which contain a wealth of structural information both on individual water molecules and small clusters in the inner “shell” in order to select representative clusters to serve as models for bound, rather than free clusters as they would occur in a protein. ConclusionsINS spectra of the water librational region calculated for a combination of model bound clusters provide a qualitative account of the essentially featureless experimental spectra on water in proteins at very low hydration levels, but do indicate that the well-known rise in intensity near 500cm−1 is connected to increasing numbers of four-coordinate water molecules in larger clusters. General significanceThe combination of structural information of hydration water from neutron protein crystallography with much more sophisticated computational methods than used herein should lead to a much more detailed picture of the hydration of proteins. This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo.

Molecular forces study and microstructure and gelling properties of smooth hound protein gels prepared by heat-induced gelation process: Effect of pH variation on textural and functional properties

Smooth hound gels (SHGs) were prepared from the viscera by heat treatment at different pH values (2.0, 5.0, 7.0 and 9.0). Their physicochemical and functional properties, microstructure and molecular forces were investigated. The pH variation was found to influence the protein molecular weight distribution resulting in different gelling properties. According to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) protein profiles, SHG-9 prepared at pH 9.0 contained the greatest amount of high molecular weight proteins. Further, the SHG-9 exhibited the highest gel strength, fracture resistance and elasticity. On the contrary, microstructure and infrared spectra analyses showed that acidic conditions provided gel networks with unarranged secondary structure and a high hydration level, which might be attributed to the formation of hydrogen bonds between polymer molecules. In addition, the molecular forces study showed that the primary dominated intermolecular forces involved in the SHGs were hydrophobic interactions and hydrogen bonds, while the secondary forces included electrostatic interactions and disulfide bridges. These results were confirmed by the levels of free amino acids. Thus, this study identified opportunities to develop high value-added products from fish by-products that might be used to carry out the function of the desired food application.

Molecular Dynamics Simulations Reveal that Water Diffusion between Graphene Oxide Layers is Slow.

Membranes made of stacked layers of graphene oxide (GO) hold the tantalizing promise of revolutionizing desalination and water filtration if selective transport of molecules can be controlled. We present the findings of an integrated study that combines experiment and molecular dynamics simulation of water intercalated between GO layers. We simulated a range of hydration levels from 1 wt.% to 23.3 wt.% water. The interlayer spacing increased upon hydration from 0.8 nm to 1.1 nm. We also synthesized GO membranes that showed an increase in layer spacing from about 0.7 nm to 0.8 nm and an increase in mass of about 15% on hydration. Water diffusion through GO layers is an order of magnitude slower than that in bulk water, because of strong hydrogen bonded interactions. Most of the water molecules are bound to OH groups even at the highest hydration level. We observed large water clusters that could span graphitic regions, oxidized regions and holes that have been experimentally observed in GO. Slow interlayer diffusion can be consistent with experimentally observed water transport in GO if holes lead to a shorter path length than previously assumed and sorption serves as a key rate-limiting step.

Thickness Dependence of Acidity and Microstructure in Nafion Films

AbstractThin films of Nafion of various thickness viz. 6 and 1 µm, 280, 80 and 33 nm have been probed using the fluorescent molecule 2‐(2′‐pyridyl)benzimidazole (2PBI), at low as well as high hydration levels. The acidity of these films has been found to be less than that of Nafion 117 membrane at hydrated conditions. This has been ascribed to the high water uptake of the films compared to the membrane and the consequent decrease in the local concentration of protons. The fluorophore reports a significant decrease in the acidity of the film upon annealing them, for all values of thickness. Surprisingly, the acidity in annealed film is lesser than in nonannealed films in which H3O+ ions are exchanged with Na+ ions. Acid treatment of the annealed films causes a reversal of this effect, except for the film with thickness less than 80 nm. Thus, pockets inaccessible to proton appear to form in the ultrathin films. The effective proton concentration depends on the thickness of the films and decreases with decrease in thickness of the films. This may be due to the association of protons to sulfonate ions at lower thickness.

Osmotic adjustment and activity of stress-related genes in wheats of different origin exposed to water stress

Plant traits involved in drought tolerance include ability to sustain plant hydration through osmotic adjustment and also the accumulation of certain specific protective proteins. The objective of this work was to evaluate the differences in water stress reaction in several lines of winter wheat (Triticum aestivum L.) of Czech, Hungarian and Syrian origin. The stress response was evaluated in young plants exposed to continuous drying using following parameters: relative water content in leaves, osmotic potential, concentration of proline, and on the molecular level the relative expression of genes from the LEA group (Late Emryogenesis Abundant) (WDHN13 and WRAB17) and genes coding transcription factors (TF) WABI5 and WDREB2γ. Czech varieties showed high expression of WDHN13 and TF WABI5 genes, and to some extent of WDREB2γ, than the other lines. Particularly Meritto variety retained a high level of tissue hydration. Relatively more drought tolerant Syrian lines had higher accumulation of proline and also high activity of the TF WDREB2γ gene. According to the results, the expression of WRAB17 was more associated to the desiccation-induced damages.