Water Entrapment Research Articles

Entrapment of Water at the Transmembrane Helix-Helix Interface of Quiescin Sulfhydryl Oxidase 2.

Little is known about how a membrane can regulate interactions between transmembrane helices. Here, we show that strong self-interaction of the transmembrane helix of human quiescin sulfhydryl oxidase 2 rests on a motif of conserved amino acids comprising one face of the helix. Atomistic molecular dynamics simulations suggest that water molecules enter the helix-helix interface and connect serine residues of both partner helices. In addition, an interfacial tyrosine can interact with noninterfacial water or lipid. Dimerization of this transmembrane helix might therefore be controlled by membrane properties controlling water permeation and/or by the lipid composition of the membrane.

Prevention of void formation in particulate-filled polymer composites: Effects of thermoplastic matrices and residual solvent

One of the key concerns in fabrication of particulate-filled polymer composites using polyimide (PI) as a matrix is formation of voids due to entrapment of water during thermal imidization of poly(amic acid) (PAA) precursor. Using hexagonal boron nitride (hBN) flakes as the filler material, this study investigated the effects of thermoplastic PI and fabrication conditions on morphological structures of hBN/PI composite films, in particular void fraction ϕv. A decrease in ϕv was observed in thermoplastic PI composites in comparison with its thermosetting counterpart. The morphological factors analyzed by SEM and WAXD showed a good correlation with the out-of-plane thermal diffusivity. A substantial decrease in ϕv was further achieved by using a solvent with higher boiling point and by shortening the drying time to increase the residual solvent in the hBN/PAA precursor films, from which the remaining solvent was eliminated during the final imidization step. Under optimized conditions, ϕv < 3% at 60 vol% hBN content was achieved through lowered glass transition temperatures of the precursor and the plasticizing effect of the solvent.

Protein Aggregates May Differ in Water Entrapment but Are Comparable in Water Confinement.

Aggregate size and density are related to gel morphology. In the context of the water distribution in complex food systems, in this study, it was aimed to investigate whether protein aggregates varying in size and density differ in entrapped and confined water. Heat-set soy protein aggregates (1%, v/v) prepared in the presence of 3.5 mM divalent salts increased in size and decreased in apparent density following the salt type order MgSO4, MgCl2, CaSO4, and CaCl2. In the absence of applied (centrifugal) forces, larger and less dense aggregates entrap more water. When force is applied from larger and more deformable aggregates, more water can be displaced. Entrapped water of ∼8-13 g of water/g of protein is associated with (pelleted) aggregates, of which approximately 4.5-8.5 g of water/g of protein is not constrained in exchangeability with the solvent. The amount of confined water within aggregates was found to be independent of the aggregate density and accounted for ∼3.5 g of water/g of protein. Confined water in aggregates is hindered in its diffusion because of physical structure constraints and, therefore, not directly exchangeable with the solvent. These insights in the protein aggregate size and deformability in relation to water entrapment and confinement could be used to tune water holding on larger length scales when force is applied.

The dynamics of hydraulic fracture water confined in nano-pores in shale reservoirs

Hydraulic fracturing treatments and horizontal well technology are central to the success of unconventional oil and gas development. In spite of this success, replicated over several thousand wells over diverse shale plays, hydraulic fracturing for shale wells remains poorly understood. This includes the poor recovery of hydraulic fracture water, the inability to explain the progressive increases in produced water salinity and an incomplete understanding of the potential trapping mechanisms for hydraulic fracture water.In this work, we focus on describing the distribution of saline water in organic and inorganic pores as a function of pore size and pore morphology with the purpose of providing fundamental insights into above questions. A kerogen model is constructed by mimicking the maturation process in a molecular dynamics simulator and it incorporates structural features observed in SEM images including the surface roughness, tortuous paths, material disorder and imperfect pore openings of kerogen pores. This work also extends this kerogen model through the use of oxygenated functional groups to study fluid behavior in partially mature shales associated with non-zero oxygen to carbon ratios.Our results demonstrate that water entrapment mechanism and the distribution of water and ions in organic and inorganic pores are strongly related to the pore-surface mineralogy and pore width. The work in this paper also underscores the importance of kerogen thermal maturity and pore roughness on the accessibility of the kerogen material to water.

An investigation of the effects of wind-induced inclination on floating wind turbine dynamics: heave plate excursion

A current trend in offshore wind is the quest for exploitation of ever deeper water sites. At depths between 50m and 100m a promising substructure is the column-stabilised semi-submersible floating type. This solution is currently being tested at full scale at the WindFloat and Fukushima Forward demonstrator sites in Portugal and Japan respectively. The semi-sub design class frequently adopts passive motion control devices based on the water entrapment principle, such as heave plates, tanks, and skirts. Whilst effective for small inclinations, these can underperform when the structure is inclined under wind loading. This study examines the alteration of potential hydrodynamics due to wind-induced trim (geometric non-linearity) and its impact on the wind turbine׳s wave response with focus on heave plate performance. Firstly it is shown by using the boundary element approach that wind trim affects wave loading in the ocean wave band between 5s and 15s, and introduces hydrodynamic coupling typical of non-symmetric hulls. These features are incorporated in frequency-domain dynamic response analysis to demonstrate that said effects bear a significant impact on the turbine׳s motion in waves. Accounting of heave plate excursion improves the assessment of the seaworthiness of floating wind turbine concepts, potentially leading to new design constraints.

Characterization of Biomass Adsorbent ZSG-1 through Isopropanol and Water Azeotrope Dehydration

In this work, a compound starch-based adsorbent material known as ZSG-1, which was formulated in a previous work for high-capacity, low-cost ethanol dehydration, was thermodynamically assessed through dehydration of azeotropic aqueous isopropanol. Comparisons of the retention times, heats of adsorption (ΔH s ), and Gibbs free energies (ΔG) of isopropanol and water confirmed the feasibility of using ZSG-1 in this dehydration process. Retention data were obtained by inverse gas chromatography and revealed the heat of adsorption ΔH s to be −55.73 kJ/mol, demonstrating that water entrapment in ZSG-1 is an exothermic physisorption process. After SEM observation, the inner micrographic pore size and surface area of ZSG-1 were calculated and estimated using an approach that combines nitrogen adsorption and mercury porosimetry. Through tests in a fixed-bed column under conditions determined by orthogonal experiment design, the optimal adsorption conditions were determined from breakthrough curves at different bed depths, bed temperatures, and kettle temperatures.

Microscopic Dynamics of Water and Hydrocarbon in Shale-Kerogen Pores of Potentially Mixed Wettability

Summary Distribution of alkanes and water in organic pores of shale, referred to as kerogen, is essential information required for the estimation of shale-reservoir oil and gas in place, adsorption of hydrocarbon, and fate of hydraulic-fracture water. A practical modeling approach is presented for the proper description of the kerogen pore systems with different mixed wettability, surface roughness, tortuous paths, and material disorder. Three kerogen models—activated kerogen, kerogen free of activated sites, and graphite-slit pore—with proper surface-oxidized functional groups and high-temperature and pressure maturation are constructed by simulation. Distribution of octane and water in the organic pores of these models is predicted by molecular dynamics (MD) simulation. The results from our studies underscore the need for accurate characterization of kerogen pore systems in terms of the pore morphology, level of surface activation, and pore size. The improved kerogen models constructed to structurally resemble real organic materials have the potential to enable a better understanding of the placement, distribution, and trapping mechanisms of hydraulic-fracture water in shales. We demonstrate that depending on the maturity of the kerogen within organic-rich shales, organic pore systems may have mixed-wet characteristics and may create opportunities for water entrapment. The differences in the uptake of water are shown to be a function of the existence of oxygenated functional groups. In addition, the adsorption characteristics of alkanes in pores characterized by surface roughness are shown to be significantly different from those observed in the graphite-slit pore model. Our results indicate that careful consideration of the pore morphology is merited when estimating hydrocarbons in place with the Langmuir monolayer-adsorption theory.

A high-precision 40 Ar/ 39 Ar age for hydrated impact glass from the Dellen impact, Sweden

Abstract The dating of terrestrial impact craters and impact glasses that exhibit high degrees of mineralogical complexity can be problematic. However, if the maximum potential of the terrestrial impact crater record is to be realized, accurate and precise ages for crater-forming events are critical. Here we report a high-precision 40 Ar/ 39 Ar age for the Dellen impact structure, Sweden. Previous radio-isotopic constraints show a wide variation in age as a result of poor sample characterization and analytical approach. A detailed petrographical and mineralogical study provides a solid foundation for interpretation of step-heating 40 Ar/ 39 Ar data, culminating in a statistically robust age of 140.82±0.51 Ma (2σ; full external precision) for the Dellen impact event, for which data disfavour an inherited argon component. Primary hydration of the impact melt during cooling–quenching and entrapment of molecular water promoted rapid loss of inherited 40 Ar from the impact melt of rhyolitic composition. Duplicate analyses of the water content and ∂D of the glass give similar values for the former (1.9±0.1 μmol mg −1 ) but unexpectedly low values for the latter (−159±8‰), with scatter beyond the expected analytical reproducibility due to isotopic heterogeneity. This study highlights that the 40 Ar/ 39 Ar technique is unrivalled in its ability to precisely and accurately date the products of hypervelocity collisional events. Supplementary material: Raw 40 Ar/ 39 Ar data are available at http://www.geolsoc.org.uk/SUP18633 .

Swimming and Survival: Two Lessons from History

Swimming skills, escape from water entrapment and the history of water safety are themes which enjoin all who work, volunteer and serve in the domains of the aquatic professions. The imperative of being able to swim and the importance of survival skills are curiously illustrated by two examples from the history of medicine. One relates to the Code of Hammurabi (1750 BC); the other relates to the punishment by drowning, inflicted by King John of Bohemia (1296 - 1346 AD). In these two examples, escape from water entrapment and the ability to swim were more important skills than the possession of medical interventions with curative outcomes, or even the presumption of innocence following criminal arrest and subsequent judicial trial. In ancient Babylon, it was more important to be able to swim than to be honest.

Impact of oxalate desensitizer combined with ethylene-diamine tetra acetic acid-conditioning on dentin bond strength of one-bottle adhesives during dry bonding

Background:Elimination of water entrapment in hybrid layer during bonding procedure would increase bonding durability.Aims:This study evaluated the effect of oxalate desensitizer (OX) pretreatment on bond strength of three one-bottle adhesives to ethylene-diamine tetra acetic acid (EDTA)-conditioned dentin under dry bonding.Materials and Methods:Three adhesive systems, One-Step Plus (OS), Optibond Solo Plus (OP) and Adper Single Bond (SB) were bonded on dentin surfaces under four bonding conditions: (1) Wet-bonding on acid-etched dentin, (2) wet bonding on EDTA-conditioned dentin, (3) dry bonding on EDTA-conditioned dentin, (4) dry bonding associated with OX on the EDTA-conditioned dentin. After storage and thermo cycling, shear bond strength test was performed. Data were analyzed using two-way analysis of variance and Tukey tests.Results:Wet bonding with EDTA or acid etching showed similar bond strength for test adhesives. Dry bonding with EDTA significantly decreased the bond strength of OS, but it had no effect on the bonding of OP and SB. OX application in the forth bonding condition, in comparison with the third condition, had a negative effect on the bond strength of OP, but not influence on OS and SB.Conclusions:The use of an OX on EDTA-conditioned dentin compromised the bonding efficacy of OS and OP under dry bonding but compatible for SB.

Unexpected T‐cell recognition of an altered peptide ligand is driven by reversed thermodynamics

The molecular basis underlying T-cell recognition of MHC molecules presenting altered peptide ligands is still not well-established. A hierarchy of T-cell activation by MHC class I-restricted altered peptide ligands has been defined using the T-cell receptor P14 specific for H-2D(b) in complex with the immunodominant lymphocytic choriomeningitis virus peptide gp33 (KAVYNFATM). While substitution of tyrosine to phenylalanine (Y4F) or serine (Y4S) abolished recognition by P14, the TCR unexpectedly recognized H-2D(b) in complex with the alanine-substituted semiagonist Y4A, which displayed the most significant structural modification. The observed functional hierarchy gp33 > Y4A > Y4S = Y4F was neither due to higher stabilization capacity nor to differences in structural conformation. However, thermodynamic analysis demonstrated that while recognition of the full agonist H-2D(b) /gp33 was strictly enthalpy driven, recognition of the weak agonist H-2D(b) /Y4A was instead entropy driven with a large reduction in the favorable enthalpy term. The fourfold larger negative heat capacity derived for the interaction of P14 with H-2D(b) /gp33 compared with H-2D(b) /Y4A can possibly be explained by higher water entrapment at the TCR/MHC interface, which is also consistent with the measured opposite entropy contributions for the interactions of P14 with both MHCs. In conclusion, this study demonstrates that P14 makes use of different strategies to adapt to structural modifications in the MHC/peptide complex.

Dynamic Nonequilibrium of Water Flow in Porous Media: A Review

This review provides an overview on various phenomena, hypothesized causes, and modeling approaches that describe “dynamic nonequilibrium” (DNE) of water flow in soils. Dynamic nonequilibrium is characterized from observations on the macroscale by an apparent flow-rate dependence of hydraulic properties or by local nonequilibrium between water content and pressure head under monotonic imbibition or drainage histories, i.e., not affected by traditional hysteresis. The literature indicates that key processes causing DNE are pore-scale phenomena such as relaxation of air–water-interface distributions, limited air-phase permeability, dynamic contact angles, and time-dependent wettability changes. Furthermore, entrapment of water and pore water blockage, air-entry effects, and temperature effects might be involved. These processes act at different pressure head regions and on different time scales, which makes effective modeling of the combined phenomena challenging. On larger scales, heterogeneity of soil properties can contribute to DNE observations. We conclude that there is an urgent need for precision measurements that are designed to quantify dynamic effects.

Stress intensity factors around a 3D squat form crack and prediction of crack growth direction considering water entrapment and elastic foundation

In this paper, the stress intensity factors (SIFs) around a 3D semi-elliptical squat on a rail surface are investigated. Elastic foundation and water trapped inside the crack are considered as key factors in crack propagation. It is found that the opening mode and shear modes show different behavior compared with former models. Also the lateral load can change the SIF pattern significantly. The superposition traction ratio and lateral load can increase the equivalent SIF up to 200%. This study confirms the pressurized water in a crack changes crack propagation direction making a squat.

Modelling a squat form crack on a rail laid on an elastic foundation

Rolling contact fatigue cracks in railway track called squats are studied in this paper. In the first part, the effects of an elastic foundation (sleepers and the ballast) on stress intensity factors obtained at a crack tip are studied. A simplified finite element model (FEM) and an extended finite element model (XFEM) were created to investigate these effects, the XFEM model being limited in geometrical size, but more able to model crack growth. Both FEM and XFEM confirmed that an elastic foundation leads to an additional bending stress which increases the crack growth rate significantly. Field results also authenticate that squat form cracks appear on timber sleepers more commonly than on concrete ones. These results indicate that considering these bending stresses in a FE model, is important to achieve a more realistic model of squat development. In the second part, a short crack of 250μm length is simulated to investigate how variations of traction ratio (TR), friction coefficient between the crack faces (FC) and the crack angle affect SIFs when the rail is mounted on an elastic foundation. Simulations show that a crack on a rail laid on elastic foundation (clips, sleepers and ballast) can lead to significantly higher SIFs in many conditions and consequently raises crack growth rate. This indicates that foundation stiffness is as important as water entrapment and friction coefficient between the crack faces.

Formation of a Mesoscopic Skin Barrier in Mesoglobules of Thermoresponsive Polymers

With the combination of molecular scale information from electron paramagnetic resonance (EPR) spectroscopy and meso-/macroscopic information from various other characterization techniques, the formation of mesoglobules of thermoresponsive dendronized polymers is explained. Apparent differences in the EPR spectra in dependence of the heating rate, the chemical nature of the dendritic substructure of the polymer, and the concentration are interpreted to be caused by the formation of a dense polymeric layer at the periphery of the mesoglobule. This skin barrier is formed in a narrow temperature range of ~4 K above T(C) and prohibits the release of molecules that are incorporated in the polymer aggregate. In large mesoglobules, formed at low heating rates and at high polymer concentrations, a considerable amount of water is entrapped that microphase-separates from the collapsed polymer chains at high temperatures. This results in the aggregates possessing an aqueous core and a corona consisting of collapsed polymer chains. A fast heating rate, a low polymer concentration, and hydrophobic subunits in the dendritic polymer side chains make the entrapment of water less favorable and lead to a higher degree of vitrification. This may bear consequences for the design and use of thermoresponsive polymeric systems in the fast growing field of drug delivery.

(A322) Animals in Disasters and Emergencies: A Version of Wild Kingdom

Dr. Madigan will discuss the evolution of awareness of the need for emergency preparedness and response for the animal component in disasters and emergencies in the United States and internationally. Emergencies and disasters affect animals and those who own them, including companion animals, animals who's use is for sustainment or groups of animals which serve as a key component of individuals economic existence. Numerous studies have shown the public will delay or refuse evacuation from impending risks if they have to leave their animals behind. A significant component of the public will refuse use of non pet associated shelters which then affects public safety and wellbeing. Emergency responders can be put at risk because of rescues required of non-evacuated individuals staying with their animals. Emergency responders may be called to be involved in animal rescues or animal evacuation. Animals impacted by disasters may incur injury, entrapment, and lack of food and water. Veterinary triage, emergency rescue, treatment and humane euthanasia are driven by animal welfare concerns as well as legislation mandating care of animals in declared disasters in some countries. Dr. Madigan's presentation will provide discussion and video examples of organized response to small and large scale animal emergency and disasters associated with 15 years as Chief of the UC Davis Veterinary Emergency Response Team. Additionally the training components needed for effective and safe preparedness and response will be discussed.

Effect of the Cross-Linking with Calcium Ions on the Structural and Thermo-Mechanical Properties of Alginate Films

ABSTRACTThe present research discusses the thermal and structural properties of calcium alginate films synthesized by cross linking precursor sodium alginate films with Ca2+ ions. Raman and FTIR spectroscopy analyses evinced the interchange of Na ions with Ca ions. Both techniques revealed a shift of the COO- vibration modes; the symmetrical COO- peak of calcium alginate exhibited a shift towards higher wavenumber (∼14 cm−1) from 1415 cm−1 to 1429 cm−1 in the Raman spectra. TGA and TMA analyses performed under a nitrogen atmosphere revealed that increasing the Ca-molarity and immersion time resulted in an increase in the glass transition temperature (Tg) and the strain deformation of the Ca-alginate film. The increase in Tg can be attributed to the Ca-cross-linking that could restrict the molecular response to temperature change whereas the increased strain could be due to the enhanced entrapment of water between the molecular chains of the polymer.

Self-assembly of trehalose molecules on a lysozyme surface: the broken glass hypothesis

To help understand how sugar interactions with proteins stabilise biomolecular structures, we compare the three main hypotheses for the phenomenon with the results of long molecular dynamics simulations on lysozyme in aqueous trehalose solution (0.75 M). We show that the water replacement and water entrapment hypotheses need not be mutually exclusive, because the trehalose molecules assemble in distinctive clusters on the surface of the protein. The flexibility of the protein backbone is reduced under the sugar patches supporting earlier findings that link reduced flexibility of the protein with its higher stability. The results explain the apparent contradiction between different experimental and theoretical results for trehalose effects on proteins.

Interaction of the disaccharides trehalose and gentiobiose with lipid bilayers: A comparative molecular dynamics study

Abstract The disaccharide α, α-trehalose (TRH) is known for its bioprotective action in organisms subject to stressful environmental conditions. However, the mechanisms whereby TRH stabilizes biomolecules remains matter of debate, the five main hypotheses being the water replacement (WRH), headgroup bridging (HBH), vitrification (VIH), water entrapment (WEH) and hydration forces (HFH) hypotheses. Four hypotheses (all except HFH) are in principle compatible with a preferential affinity of the sugar molecules (compared to water) for the biomolecular surface. According to the recently proposed sugar-like mechanism (Pereira and Hünenberger [29]), preferential affinity would result from the entropy gain upon releasing many water molecules from the surface region to the bulk, at the cost of immobilizing and rigidifying fewer sugar molecules. Thus, a more flexible disaccharide such as gentiobiose (GNT) should evidence a weaker preferential affinity, limiting its bioprotective ability. In this work, molecular dynamics (MD) simulations of a dipalmitoyl-phosphatidylcholine (DPPC) bilayer patch in the presence of either pure water or aqueous solutions of GNT or TRH are performed in order to assess the validity of this suggestion. At 475 K and 1.6 m (molal), TRH indeed preserves the bilayer structure to a larger extent compared to GNT. However, the present investigation does not unambiguously indicate which of the above mechanism takes place, since the simulations reveal characteristic features of all of them. This suggests either that multiple mechanisms may be simultaneously active or that their definitions are not precise enough.

Dehydrating phospholipid vesicles measured in real-time using ATR Fourier transform infrared spectroscopy

According to the water replacement hypothesis, trehalose stabilizes dry membranes by preventing the decrease in spacing between adjacent phopspholipid headgroups during dehydration. Alternatively, the water-entrapment hypothesis postulates that in the dried state sugars trap residual water at the biomolecule sugar interface. In this study, Fourier transform infrared spectroscopy with an attenuated total reflection accessory was used to investigate the influence of trehalose on the dehydration kinetics and residual water content of egg phosphatidylcholine liposomes in real time under controlled relative humidity conditions. In the absence of trehalose, the lipids displayed a transition to a more ordered gel phase upon drying. The membrane conformational disorder in the dried state was found to decrease with decreasing relative humidity. Even at a relative humidity as high as 94% the conformational disorder of the lipid acyl chains decreased after evaporation of the bulk water. The presence of trehalose affects the rate of water removal from the system and the lipid phase behavior. The rate of water removal is decreased and the residual water content is higher, as compared to drying in the absence of trehalose. During drying, the level of hydrogen bonding to the head groups remains constant. In addition, the conformational disorder of the lipid acyl chains in the dried state more closely resembles that of the lipids in the fully hydrated state. We conclude that water entrapment rather than water replacement explains the effect of trehalose on lipid phase behavior of phosphatidylcholine lipid bilayers during the initial phase of drying.