hydrate crystallization application: Topics by Science.gov

Sample records for hydrate crystallization application

Raman spectroscopic investigations on natural samples from the Integrated Ocean Drilling Program (IODP) Expedition 311: indications for heterogeneous compositions in hydrate crystals.

PubMed

Schicks, J M; Ziemann, M A; Lu, H; Ripmeester, J A

2010-12-01

Natural gas hydrates usually are found in the form of structure I, encasing predominantly methane in the hydrate lattices as guest molecules, sometimes also minor amount of higher hydrocarbons, CO2 or H2S. Raman spectroscopy is an approved tool to determine the composition of the hydrate phase. Thus, in this study Raman spectroscopic analyses have been applied to hydrate samples obtained from Integrated Ocean Drilling Program (IODP) Expedition 311 in two different approaches: studying the samples randomly taken from the hydrate core, and--as a new application--mapping small areas on the surface of clear hydrate crystals. The results obtained imply that the gas composition of hydrate, in terms of relative concentrations of CH4 and H2S, is not homogeneous over a core or even within a crystal. The mapping method yielded results with very high lateral resolution, indicating the coexistence of different phases with the same structure but different compositions within a hydrate crystal. Copyright © 2010 Elsevier B.V. All rights reserved.
Electrostatic energy of transfer and macrobond analyses of intermolecular interactions and hydration effects in protein crystals in a low ionic environment

NASA Astrophysics Data System (ADS)

Sugawara, Yoko; Hirano, Yuji; Yamamura, Shigefumi; Endo, Shigeru; Ootaki, Masanori; Matsumoto, Naoki; Takahashi, Takuya

2017-06-01

We developed an electrostatic energy of transfer (EET) analysis applicable to periodic boundary condition, including a nonrectangular unit cell. It was applied to monoclinic ribonuclease A crystallized with ethanol as a precipitant. Macrobond analysis was also carried out. Owing to the low ionic strength of the solvent region, atomic EET values were non-negligible even at long-distance points. Most of the molecular EET values-defined as the individual contribution of each surrounding molecule-were positive. The inclusion of the molecular EET values of hydration water molecules reduced the repulsive force, and the evaluation of hydration effects in protein crystals was found to be imperative.
An Experiment with Manifold Purposes: The Chemical Reactivity of Crystal Defects upon Crystal Dissolution.

ERIC Educational Resources Information Center

Lazzarini, Annaluisa Fantola; Lazzarini, Ennio

1983-01-01

Background information and procedures are provided for an experiment designed to introduce (1) crystal defects and their reactivity upon crystal dissolution; (2) hydrates electron and its reactivity; (3) application of radiochemical method of analysis; and (4) the technique of competitive kinetics. Suggested readings and additional experiments are…
Structure of the ordered hydration of amino acids in proteins: analysis of crystal structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biedermannová, Lada, E-mail: lada.biedermannova@ibt.cas.cz; Schneider, Bohdan

2015-10-27

The hydration of protein crystal structures was studied at the level of individual amino acids. The dependence of the number of water molecules and their preferred spatial localization on various parameters, such as solvent accessibility, secondary structure and side-chain conformation, was determined. Crystallography provides unique information about the arrangement of water molecules near protein surfaces. Using a nonredundant set of 2818 protein crystal structures with a resolution of better than 1.8 Å, the extent and structure of the hydration shell of all 20 standard amino-acid residues were analyzed as function of the residue conformation, secondary structure and solvent accessibility. Themore » results show how hydration depends on the amino-acid conformation and the environment in which it occurs. After conformational clustering of individual residues, the density distribution of water molecules was compiled and the preferred hydration sites were determined as maxima in the pseudo-electron-density representation of water distributions. Many hydration sites interact with both main-chain and side-chain amino-acid atoms, and several occurrences of hydration sites with less canonical contacts, such as carbon–donor hydrogen bonds, OH–π interactions and off-plane interactions with aromatic heteroatoms, are also reported. Information about the location and relative importance of the empirically determined preferred hydration sites in proteins has applications in improving the current methods of hydration-site prediction in molecular replacement, ab initio protein structure prediction and the set-up of molecular-dynamics simulations.« less
Effects of cyclic structure inhibitors on the morphology and growth of tetrahydrofuran hydrate crystals

NASA Astrophysics Data System (ADS)

Li, Sijia; Wang, Yanhong; Lang, Xuemei; Fan, Shuanshi

2013-08-01

Morphology and growth of hydrate crystals with cyclic structure inhibitors at a hydrate-liquid interface were directly observed through a microscopic manipulating apparatus. Tetrahydrofuran (THF) hydrate was employed as an objective. The effects of four kind of cyclic structure inhibitors, polyvinylpyrrolidone (PVP), poly(N-vinyl-2-pyrrolidone-co-2-vinyl pyridine) (PVPP), poly(2-vinyl pyridine-co-N-vinylcaprolactam) (PVPC) and poly(N-vinylcaprolactam) (PVCap), were investigated. Morphological patterns between each hydrate crystal growth from hydrate-liquid interface into droplet were found differ significantly. Lamellar structure growth of hydrate crystal was observed without inhibitor, while with PVP was featheriness-like, PVPP was like long dendritic crystal, PVPC was Mimosa pudica leaf-like and PVCap was like weeds. The growth rate of hydrate crystal without inhibitor was 0.00498 mm3/s, while with PVPP, PVPC and PVCap, were 0.00339 mm3/s, 0.00350 mm3/s, 0.00386 mm3/s and 0.00426 mm3/s, respectively. Cyclic structure inhibitors can decrease the growth rate, degree of reduction in growth rate of hydrate crystals decrease with the increase of cylinder number.
The effect of a solid surface on the segregation and melting of salt hydrates.

PubMed

Zhang, Yu; Anim-Danso, Emmanuel; Dhinojwala, Ali

2014-10-22

Considering the importance of salt and water on earth, the crystallization of salt hydrates next to solid surfaces has important implications in physical and biological sciences. Heterogeneous nucleation is driven by surface interactions, but our understanding of hydrate formation near surfaces is limited. Here, we have studied the hydrate formation of three commonly prevalent salts, MgCl2, CaCl2, and NaCl, next to a sapphire substrate using surface sensitive infrared-visible sum frequency generation (SFG) spectroscopy. SFG spectroscopy can detect the crystallization and melting of salt hydrates at the interface by observing the changes in the intensity and the location of the cocrystallized water hydroxyl peaks (3200-3600 cm(-1)). The results indicate that the surface crystal structures of these three hydrates are similar to those in the bulk. For the NaCl solution, the brine solution is segregated next to the sapphire substrate after the formation of the ice phase. In contrast, the MgCl2 and CaCl2 surface hydrate crystals are interdispersed with nanometer-size ice crystals. The nanosize ice crystals melt at much lower temperatures than bulk ice crystals. For NaCl and MgCl2 solution, the NaCl hydrates prefer to crystallize next to the sapphire substrate instead of the ice crystals and MgCl2 hydrates.
Visual observation of gas hydrates nucleation and growth at a water - organic liquid interface

NASA Astrophysics Data System (ADS)

Stoporev, Andrey S.; Semenov, Anton P.; Medvedev, Vladimir I.; Sizikov, Artem A.; Gushchin, Pavel A.; Vinokurov, Vladimir A.; Manakov, Andrey Yu.

2018-03-01

Visual observation of nucleation sites of methane and methane-ethane-propane hydrates and their further growth in water - organic liquid - gas systems with/without surfactants was carried out. Sapphire Rocking Cell RCS6 with transparent sapphire cells was used. The experiments were conducted at the supercooling ΔTsub = 20.2 °C. Decane, toluene and crude oils were used as organics. Gas hydrate nucleation occurred on water - metal - gas and water - sapphire - organic liquid three-phase contact lines. At the initial stage of growth hydrate crystals rapidly covered the water - gas or water - organics interfaces (depending on the nucleation site). Further hydrate phase accrete on cell walls (sapphire surface) and into the organics volume. At this stage, growth was accompanied by water «drawing out» from under initial hydrate film formed at water - organic interface. Apparently, it takes place due to water capillary inflow in the reaction zone. It was shown that the hydrate crystal morphology depends on the organic phase composition. In the case of water-in-decane emulsion relay hydrate crystallization was observed in the whole sample, originating most likely due to the hydrate crystal intergrowth through decane. Contacts of such crystals with adjacent water droplets result in rapid hydrate crystallization on this droplet.
Screening and Characterization of Hydrate Forms of T-3256336, a Novel Inhibitor of Apoptosis (IAP) Protein Antagonist.

PubMed

Takeuchi, Shoko; Kojima, Takashi; Hashimoto, Kentaro; Saito, Bunnai; Sumi, Hiroyuki; Ishikawa, Tomoyasu; Ikeda, Yukihiro

2015-01-01

Different crystal packing of hydrates from anhydrate crystals leads to different physical properties, such as solubility and stability. Investigation of the potential of varied hydrate formation, and understanding the stability in an anhydrous/hydrate system, are crucial to prevent an undesired transition during the manufacturing process and storage. Only one anhydrous form of T-3256336, a novel inhibitor of apoptosis (IAP) protein antagonist, was discovered during synthesis, and no hydrate form has been identified. In this study, we conducted hydrate screening such as dynamic water vapor sorption/desorption (DVS), and the slurry experiment, and characterized the solid-state properties of anhydrous/hydrate forms to determine the most desirable crystalline form for development. New hydrate forms, both mono-hydrate and hemi-hydrate forms, were discovered as a result of this hydrate screening. The characterization of two new hydrate forms was conducted, and the anhydrous form was determined to be the most desirable development form of T-3256336 in terms of solid-state stability. In addition, the stability of the anhydrous form was investigated using the water content and temperature controlled slurry experiment to obtain the desirable crystal form in the crystallization process. The water content regions of the stable phase of the desired form, the anhydrous form, were identified for the cooling crystallization process.
RH-temperature phase diagrams of hydrate forming deliquescent crystalline ingredients.

PubMed

Allan, Matthew; Mauer, Lisa J

2017-12-01

Several common deliquescent crystalline food ingredients (including glucose and citric acid) are capable of forming crystal hydrate structures. The propensity of such crystals to hydrate/dehydrate or deliquesce is dependent on the environmental temperature and relative humidity (RH). As an anhydrous crystal converts to a crystal hydrate, water molecules internalize into the crystal structure resulting in different physical properties. Deliquescence is a solid-to-solution phase transformation. RH-temperature phase diagrams of the food ingredients alpha-d-glucose and citric acid, along with sodium sulfate, were produced using established and newly developed methods. Each phase diagram included hydrate and anhydrate deliquescence boundaries, the anhydrate-hydrate phase boundary, and the peritectic temperature (above which the hydrate was no longer stable). This is the first report of RH-temperature phase diagrams of glucose and citric acid, information which is beneficial for selecting storage and processing conditions to promote or avoid hydrate formation or loss and/or deliquescence. Copyright © 2017 Elsevier Ltd. All rights reserved.
The inhibition of tetrahydrofuran clathrate-hydrate formation with antifreeze protein

NASA Astrophysics Data System (ADS)

Zeng, H.; Wilson, L. D.; Walker, V. K.; Ripmeester, J. A.

2003-01-01

The effect of Type I fish antifreeze protein (AFP) from the winter flounder, Pleuronectes americanus (Walbaum), (WfAFP) on the formation of tetrahydrofuran (THF) clathrate hydrate was studied by observing changes in THF crystal morphology and determining the induction time for nucleation. AFP retarded THF clathrate-hydrate growth at the tested temperatures and modified the THF clathrate-hydrate crystal morphology from octahedral to plate-like. AFP appears to be even more effective than the kinetic inhibitor, polyvinylpyrrolidone (PVP). Recombinant AFP from an insect, a spruce budworm, Choristoneura fumiferana (Clem.), moth, (Cf) was also tested for inhibition activity by observation of the THF-hydrate-crystal-growth habit. Like WfAFP, CfAFP appeared to show adsorption on multiple THF-hydrate-crystal faces. A protein with no antifreeze activity, cytochrome C, was used as a control and it neither changed the morphology of the THF clathrate-hydrate crystals, nor retarded the formation of the hydrate. Preliminary experiments on the inhibition activity of WfAFP on a natural gas hydrate assessed induction time and the amount of propane gas consumed. Similar to the observations for THF, the data indicated that WfAFP inhibited propane-hydrate growth. Taken together, these results support our hypothesis that AFPs can inhibit clathrate-hydrate growth and as well, offer promise for the understanding of the inhibition mechanism.
Crystalline coats or hollow crystals as tools for product design in pharmaceutical industry

NASA Astrophysics Data System (ADS)

Ulrich, J.; Schuster, A.; Stelzer, T.

2013-01-01

The coating of pharmaceutical compounds is a field of high interest. As most of the coating materials form an amorphous layer around the material, the studies on crystalline coatings are rare. In this work the progress in this domain should be summarized and innovative results concerning crystalline hollow needles as coating material are presented. Since the first reports on needles formed via a solvent-mediated phase transition from solvates to hydrates, the field could be widened to hydrate-to-anhydrate and anhydrate-to-hydrate transformations. Novel investigations on hollow theophylline monohydrate and carbamazepine dihydrate needles are presented. It is shown that the inclusion of substances into the hollow needle crystals is feasible by simple means, which enable an application in industry as coating for sensitive materials.
Characterization of Methane Hydrate Growth from Aqueous Solution by Raman Spectroscopy

NASA Astrophysics Data System (ADS)

Chou, I.; Lu, W.; Yuan, S.; Li, J.; Burruss, R. C.

2009-12-01

We observed the growth of methane hydrate from aqueous solution in fused silica capillaries near room temperature (RT) in two different experiments. In the first, we sealed methane together with ~2 wt% Na2SO4 solution in a fused silica capillary (0.3x0.3 mm cross-section with 0.05x0.05 mm cavity, and ~6 cm long), using the method of Chou et al. (2008, Geochim. Cosmochim. Acta, 72, 2517). The hydrate, liquid, and vapor coexist at ~23 °C and ~36.5 MPa. The behavior of two methane bubbles, one of which was enclosed by a hydrate crystal and the other near a small hydrate crystal, was monitored. These two bubbles are the only methane sources near the hydrate crystals. The system was slowly cooled to RT (~21 °C), and images were recorded continuously for a period of ~1.5 hours, together with temperature and time information. The images show the exposed bubble decreased in size, while both of the hydrate crystals increased in size, which was caused by the transfer of methane in solution. According to our previous report (Fig. 8 of Lu et al., 2008, Geochim. Cosmochim. Acta, 72, 412), the concentrations of methane in the solution near the exposed bubble are higher than those near the hydrate crystals. Most of the dissolved methane, transferred down the concentration gradient, was consumed and encaged in the nearby crystal, with only a small fraction of methane being consumed by the more distant crystal. Eventually, the exposed vapor bubble was totally consumed, but the bubble shielded by the hydrate crystal remained. This shows hydrate can grow from dissolved methane in the solution far away from free gas. In the 2nd experiment, we sealed methane, together with pure H2O and glass beads (0.04 to 0.07 mm in dia.), in a fused silica capillary (0.3 mm OD, 0.1 mm ID, and ~6 cm long) using the method cited above. We separated the vapor phase from the solution and glass beads by centrifuging the sealed capsule, then imposed a T gradient to the sample by cooling the solution end of the capsule to ~0 °C. It is difficult to recognize the nucleation and growth of hydrate crystals under a microscope, but Raman spectroscopy was used to identify and map the distribution of hydrate crystals along the capsule. Near the original vapor-aqueous phase boundary (V-A B), Raman signals show 100% methane hydrate. However, the lack of dissolved methane in the solution further away from the V-A B limited the growth of hydrate, as indicated by the increase in water/hydrate ratio when the Raman spectrum, which combines signals from both water and hydrate, was collected further away from the V-A B. We are investigating other possible ways to map the distribution of hydrate crystals around the glass beads, including x-ray computed tomography, to understand the nature of methane hydrate crystals that grow around grains in marine sediments from pore water. These observations will improve our ability to interpret the geophysical responses (e.g., electric and acoustic signals) obtained from hydrate-bearing sediments in the field.
A spectroscopic study of the structure and occupancies of clathrate hydrates incorporating hydrogen

NASA Astrophysics Data System (ADS)

Grim, R. Gary

With the ability to store and concentrate gases inside a clean and abundant water framework, clathrate hydrates are considered to be a promising material for many applications related to gas storage, separation, and sequestration. Hydrates of hydrogen are particularly interesting, for in addition to these potential applications, the small molecular size provides an opportunity for use as a model guest in many fundamental studies such as guest diffusion, multiple guest occupancy, and quantum mechanical effects upon confinement. In attempt to study these effects and the viability of H 2 hydrates as an energy storage material, a combined experimental and theoretical approach incorporating Raman spectroscopy, X-ray and neutron diffraction, nuclear magnetic resonance, ab-initio calculations, and molecular dynamic simulations was performed. One of the most significant challenges in the application of H2 clathrate hydrates is the demanding thermodynamic requirements needed for stability. In recent years, a mechanism known as the `tuning' effect had reportedly solved this issue where thermodynamic requirements could be reduced while simultaneously maintaining high storage capacities. In this work, the viability and validity of this technique is explored and alternative explanations in the form of epitaxial hydrate growth under high driving force conditions are discussed. A second, and equally important challenge facing clathrate hydrates as a future storage material is the overall storage capacity of H2. In previous work, H2 has only been experimentally verified to occupy the small 512 and 43566 3 cages and also in the large 51264 cages of the type II clathrate, often with an energy deficient promoter. In order to achieve more robust energy densities, other hydrate cages must be accessible. Herein a new method for increasing overall hydrate energy densities is presented involving the incorporation of H2 in the large cages of the type I clathrate with CH4 as a co-guest molecule. Finally, for all of the collective research on gas hydrates since their discovery in 1810 by Sir Humphrey Davy, the one common theme that unites them is the assumption that guest molecules are trapped at the center (or near center) of the host water cages that makes up the respective crystal structure. For the first time, this work provides evidence suggesting that this definition of clathrate hydrate guest occupancy is possibly incomplete, and should include the addition of interstitial sites within the water crystal lattice. Specifically, H2 is found within the shared heptagonal faces of the large (4 3596273) cage and in cavities formed from the disruption of smaller (445 4) water cages in structure VI hydrates. The ability of H2 to occupy these interstitial sites and fluctuate position in the crystal lattice demonstrates the dynamic behavior of H2 in solids and reveals new insight into guest-guest and guest-host interactions in clathrate hydrates with potential implications in increasing overall energy storage properties.
Roles of Sodium Dodecyl Sulfate on Tetrahydrofuran-Assisted Methane Hydrate Formation.

PubMed

Siangsai, Atsadawuth; Inkong, Katipot; Kulprathipanja, Santi; Kitiyanan, Boonyarach; Rangsunvigit, Pramoch

2018-06-01

Sodium dodecyl sulfate (SDS) markedly improved tetrahydrofuran (THF) - assisted methane hydrate formation. Firstly, methane hydrate formation with different THF amount, 1, 3, and 5.56 mol%, was studied. SDS with 1, 4, and 8 mM was then investigated for its roles on the methane hydrate formation with and without THF. The experiments were conducted in a quiescent condition in a fixed volume crystallizer at 8 MPa and 4°C. The results showed that almost all studied THF and SDS concentrations enhanced the methane hydrate formation kinetics and methane consumption compared to that without the promoters, except 1 mol% THF. Although, with 1 mol% THF, there were no hydrates formed for 48 hours, the addition of just 1 mM SDS surprisingly promoted the hydrate formation with a significant increased in the kinetics. This prompts the use of methane hydrate technology for natural gas storage application with minimal promoters.
[Laser Raman Spectroscopy and Its Application in Gas Hydrate Studies].

PubMed

Fu, Juan; Wu, Neng-you; Lu, Hai-long; Wu, Dai-dai; Su, Qiu-cheng

2015-11-01

Gas hydrates are important potential energy resources. Microstructural characterization of gas hydrate can provide information to study the mechanism of gas hydrate formation and to support the exploitation and application of gas hydrate technology. This article systemly introduces the basic principle of laser Raman spectroscopy and summarizes its application in gas hydrate studies. Based on Raman results, not only can the information about gas composition and structural type be deduced, but also the occupancies of large and small cages and even hydration number can be calculated from the relative intensities of Raman peaks. By using the in-situ analytical technology, laser Raman specstropy can be applied to characterize the formation and decomposition processes of gas hydrate at microscale, for example the enclathration and leaving of gas molecules into/from its cages, to monitor the changes in gas concentration and gas solubility during hydrate formation and decomposition, and to identify phase changes in the study system. Laser Raman in-situ analytical technology has also been used in determination of hydrate structure and understanding its changing process under the conditions of ultra high pressure. Deep-sea in-situ Raman spectrometer can be employed for the in-situ analysis of the structures of natural gas hydrate and their formation environment. Raman imaging technology can be applied to specify the characteristics of crystallization and gas distribution over hydrate surface. With the development of laser Raman technology and its combination with other instruments, it will become more powerful and play a more significant role in the microscopic study of gas hydrate.
Surfactant Effect on Hydrate Crystallization at the Oil-Water Interface.

PubMed

Dann, Kevin; Rosenfeld, Liat

2018-05-29

Gas hydrates pose economic and environmental risks to the oil and gas industry when plug formation occurs in pipelines. A novel approach was applied to understand cyclopentane clathrate hydrate formation in the presence of nonionic surfactant to achieve hydrate inhibition at low percent weight compared to thermodynamic inhibitors. The hydrate-inhibiting performance of low (CMC) concentrations of Span 20, Span 80, Pluronic L31, and Tween 65 at 2 °C on a manually nucleated 2 μL droplet showed a morphological shift in crystallization from planar shell growth to conical growth. Monitoring the internal pressure of the water droplet undergoing hydrate crystallization provides information on the change in interfacial tension during the crystallization process. The results of this study will provide information on the surfactant effect on hydrate crystallization and inhibition. At low surfactant concentrations (below CMC), a planar hydrate crystal was formed. Decreasing interfacial tension was observed, which can be related to the shrinking area of the water-cyclopentane interface. At high surfactant concentration, the crystal morphology was shifted to conical. Interfacial tension measurements reveal oscillations of the interfacial tension during the crystallization process. The oscillations of the interfacial tension result from the fact that once the crystal has reached a critical size a portion of the cone breaks free from the droplet surface, which results in a sudden increase in the available surface for the surfactant molecules. Hence, a temporary increase in the interfacial tension can be observed. The oscillatory behavior of the interfacial tension is a result of the growth and release of the hydrate cones from the surface of the droplet. We have found that the most efficient surfactant in hydrate inhibition would be the one with HLB closest to 10 (equal hydrophilic-hydrophobic parts). In this way, the surfactant molecules will stay at the interface as they observe equal affinities for both the oil and water phases. Surfactant molecules that have the strongest affinity to the interface will be able to inhibit the growth of the crystal as they will force the cones to break and will not allow them to grow.
Investigation of inorganic nonlinear optical potassium penta borate tetra hydrate (PPBTH) single crystals grown by slow evaporation method

NASA Astrophysics Data System (ADS)

Arivuselvi, R.; Babu, P. Ramesh

2018-03-01

Borates family crystals were plays vital role in the field of non linear optics (NLO) due to needs of wide range of applications. In this report, NLO crystals (potassium penta borate tetra hydrate (KB5H8O12) are grown by slow evaporation method at room temperature (28° C) and studied their physical properties. The harvested single crystals are transparent with the dimension of 12 × 10 × 6 mm3 and colourless. X-ray diffraction of single crystals reveals that the grown crystal belongs to orthorhombic system with non-centrosymmetric space group Pba2. All the absorbed functional groups are present in the order of inorganic compounds expect 1688 cm-1 because of water (Osbnd H sbnd O blending) molecule present in the pristine. Crystals show transparent in the entire visible region with 5.9 eV optical band gap and also it shows excellence in both second and third order nonlinear optical properties. Crystals can withstand upto 154 °C without any phase changes which is observed using thermal (TGA/DTA) analysis.
Search for memory effects in methane hydrate: structure of water before hydrate formation and after hydrate decomposition.

PubMed

Buchanan, Piers; Soper, Alan K; Thompson, Helen; Westacott, Robin E; Creek, Jefferson L; Hobson, Greg; Koh, Carolyn A

2005-10-22

Neutron diffraction with HD isotope substitution has been used to study the formation and decomposition of the methane clathrate hydrate. Using this atomistic technique coupled with simultaneous gas consumption measurements, we have successfully tracked the formation of the sI methane hydrate from a water/gas mixture and then the subsequent decomposition of the hydrate from initiation to completion. These studies demonstrate that the application of neutron diffraction with simultaneous gas consumption measurements provides a powerful method for studying the clathrate hydrate crystal growth and decomposition. We have also used neutron diffraction to examine the water structure before the hydrate growth and after the hydrate decomposition. From the neutron-scattering curves and the empirical potential structure refinement analysis of the data, we find that there is no significant difference between the structure of water before the hydrate formation and the structure of water after the hydrate decomposition. Nor is there any significant change to the methane hydration shell. These results are discussed in the context of widely held views on the existence of memory effects after the hydrate decomposition.
Molecular insights into the heterogeneous crystal growth of si methane hydrate.

PubMed

Vatamanu, Jenel; Kusalik, Peter G

2006-08-17

In this paper we report a successful molecular simulation study exploring the heterogeneous crystal growth of sI methane hydrate along its [001] crystallographic face. The molecular modeling of the crystal growth of methane hydrate has proven in the past to be very challenging, and a reasonable framework to overcome the difficulties related to the simulation of such systems is presented. Both the microscopic mechanisms of heterogeneous crystal growth as well as interfacial properties of methane hydrate are probed. In the presence of the appropriate crystal template, a strong tendency for water molecules to organize into cages around methane at the growing interface is observed; the interface also demonstrates a strong affinity for methane molecules. The maximum growth rate measured for a hydrate crystal is about 4 times higher than the value previously determined for ice I in a similar framework (Gulam Razul, M. S.; Hendry, J. G.; Kusalik, P. G. J. Chem. Phys. 2005, 123, 204722).
Role of Polymeric Excipients in the Stabilization of Olanzapine when Exposed to Aqueous Environments.

PubMed

Paisana, Maria; Wahl, Martin; Pinto, João

2015-12-12

Hydrate formation is a phase transition which can occur during manufacturing processes involving water. This work considers the prevention of hydration of anhydrous olanzapine and hydrate conversions in the presence of water and polymers (polyethyleneglycol; hydroxypropylcellulose; polyvinylpyrrolidone) in forming pellets by wet extrusion and spheronisation. Anhydrous olanzapine was added to water with or without those polymers prior to extrusion with microcrystalline cellulose. Assessment of olanzapine conversion was made by XRP-Diffraction; FTIR spectroscopy; calorimetry (DSC) and microscopy (SEM for crystal size and shape). The addition of water converted the anhydrous form into dihydrate B and higher hydrate; whereas polyethyleneglycol promoted a selective hydrate conversion into the higher hydrate olanzapine form. Both polyvinylpyrrolidone and hydroxypropylcellulose prevented the hydrate transformations of the anhydrous drug; the latter even in the presence of hydrate seeds. This may be explained by the higher H-bond ability; higher network association and higher hydrophobicity of hydroxypropylcellulose by comparison with polyethyleneglycol and polyvinylpyrrolidone; which could contribute to its higher affinity to the crystal surfaces of the hydrate nuclei/initial crystals and promoting steric hindrance to the incorporation of other drug molecules into the crystal lattice; thus, preventing the crystal growth. The addition of microcrystalline cellulose needed for the pellets production (final product) did not eliminate the protector effect of both hydroxypropylcellulose and polyvinylpyrrolidone during pellets' processing and dissolution evaluation.

Nucleation pathways of clathrate hydrates: effect of guest size and solubility.

PubMed

Jacobson, Liam C; Hujo, Waldemar; Molinero, Valeria

2010-11-04

Understanding the microscopic mechanism of nucleation of clathrate hydrates is important for their use in hydrogen storage, CO(2) sequestration, storage and transport of natural gas, and the prevention of the formation of hydrate plugs in oil and gas pipelines. These applications involve hydrate guests of varied sizes and solubility in water that form different hydrate crystal structures. Nevertheless, molecular studies of the mechanism of nucleation of hydrates have focused on the single class of small hydrophobic guests that stabilize the sI crystal. In this work, we use molecular dynamics simulations with a very efficient coarse-grained model to elucidate the mechanisms of nucleation of clathrate hydrates of four model guests that span a 2 orders of magnitude range in solubility in water and that encompass sizes which stabilize each one a different hydrate structure (sI and sII, with and without occupancy of the dodecahedral cages). We find that the overall mechanism of clathrate nucleation is similar for all guests and involves a first step of formation of blobs, dense clusters of solvent-separated guest molecules that are the birthplace of the clathrate cages. Blobs of hydrophobic guests are rarer and longer-lived than those for soluble guests. For each guest, we find multiple competing channels to form the critical nuclei, filled dodecahedral (5(12)) cages, empty 5(12) cages, and a variety of filled large (5(12)6(n) with n = 2, 3, and 4) clathrate cages. Formation of empty dodecahedra is an important nucleation channel for all but the smallest guest. The empty 5(12) cages are stabilized by the presence of guests from the blob in their first solvation shell. Under conditions of high supercooling, the structure of the critical and subcritical nuclei is mainly determined by the size of the guest and does not reflect the cage composition or ordering of the stable or metastable clathrate crystals.
Small-Angle Neutron Scattering Investigation of Growth Modifiers on Hydrate Crystal Surfaces

NASA Astrophysics Data System (ADS)

Sun, Thomas; Hutter, Jeffrey L.; Lin, M.; King, H. E., Jr.

1998-03-01

Hydrates are crystals consisting of small molecules enclathrated within an ice-like water cage. Suppression of their growth is important in the oil industry. The presence of small quantities of specific polymers during hydrate crystallization can induce a transition from an octahedral to planar growth habit. This symmetry breaking is surprising because of the suppression of two 111 planes relative to the other six crystallographically equivalent faces. To better understand the surface effects leading to this behavior, we have studied the surface adsorption of these growth-modifing polymers onto the hydrate crytals using SANS. The total hydrate surface area, as measured by Porod scattering, increases in the presence of the growth modifier, but, no significant increase in polymer concentration on the crystal surfaces is found. Implications for possible growth mechanisms will be discussed.
Substituent effect on the thermodynamic solubility of structural analogs: relative contribution of crystal packing and hydration.

PubMed

Ozaki, Shunsuke; Nakagawa, Yoshiaki; Shirai, Osamu; Kano, Kenji

2014-11-01

Thermodynamic analysis of the solubility of benzoylphenylurea (BPU) derivatives was conducted to investigate the relative importance of crystal packing and hydration for improving solubility with minor structural modification. The contribution of crystal packing to solubility was evaluated from the change in Gibbs energy on the transition from the crystalline to liquid state. Hydration Gibbs energy was estimated using a linear free-energy relationship between octanol-water partition coefficients and gas-water partition coefficients. The established solubility model satisfactorily explained the relative thermodynamic solubility of the model compounds and revealed that crystal packing and hydration equally controlled solubility of the structural analogs. All hydrophobic substituents were undesirable for solubility in terms of hydration, as expected. On the other hand, some of these hydrophobic substituents destabilized crystal packing and improved the solubility of the BPU derivatives when their impact on crystal packing exceeded their negative influence on hydration. The replacement of a single substituent could cause more than a 10-fold enhancement in thermodynamic solubility; this degree of improvement was comparable to that generally achieved by amorphous formulations. Detailed analysis of thermodynamic solubility will allow us to better understand the true substituent effect and design drug-like candidates efficiently. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.
THF water hydrate crystallization: an experimental investigation

NASA Astrophysics Data System (ADS)

Devarakonda, Surya; Groysman, Alexander; Myerson, Allan S.

1999-08-01

Supersaturated solutions of THF-water hydrate system were experimentally studied before and during crystallization, to examine the system's behavior in the metastable zone and observe any anomalies suggesting cluster formation. Nucleation induction time measurements, with and without additives, were performed to screen potential growth inhibitors. Shifts in the onset points of crystallization for water and THF-water mixtures with additives were measured using differential scanning calorimetry (DSC). Aspartame was among one of the few successfully screened inhibitors. Preliminary on-line crystal size distribution (CSD) measurements were performed on this system to monitor the crystal size during crystallization. The CSD data was also used to compute the hydrate crystal growth rates, which were found to be in the order of 145 μm/h.
Absorption spectra analysis of hydrated uranium(III) complex chlorides

NASA Astrophysics Data System (ADS)

Karbowiak, M.; Gajek, Z.; Drożdżyński, J.

2000-11-01

Absorption spectra of powdered samples of hydrated uranium(III) complex chlorides of the formulas NH 4UCl 4 · 4H 2O and CsUCl 4 · 3H 2O have been recorded at 4.2 K in the 4000-26 000 cm -1 range. The analysis of the spectra enabled the determination of crystal-field parameters and assignment of 83 and 77 crystal-field levels for the tetrahydrate and trihydrate, respectively. The energies of the levels were computed by applying a simplified angular overlap model as well as a semiempirical Hamiltonian representing the combined atomic and crystal-field interactions. Ab initio calculations have enabled the application of a simplified parameterization and the determination of the starting values of the AOM parameters. The received results have proved that the AOM approach can quite well predict both the structure of the ground multiplet and the positions of the crystal-field levels in the 17 000-25 000 cm -1 range, usually obscured by strong f-d bands.
Report on the sixth blind test of organic crystal structure prediction methods

PubMed Central

Reilly, Anthony M.; Cooper, Richard I.; Adjiman, Claire S.; Bhattacharya, Saswata; Boese, A. Daniel; Brandenburg, Jan Gerit; Bygrave, Peter J.; Bylsma, Rita; Campbell, Josh E.; Car, Roberto; Case, David H.; Chadha, Renu; Cole, Jason C.; Cosburn, Katherine; Cuppen, Herma M.; Curtis, Farren; Day, Graeme M.; DiStasio Jr, Robert A.; Dzyabchenko, Alexander; van Eijck, Bouke P.; Elking, Dennis M.; van den Ende, Joost A.; Facelli, Julio C.; Ferraro, Marta B.; Fusti-Molnar, Laszlo; Gatsiou, Christina-Anna; Gee, Thomas S.; de Gelder, René; Ghiringhelli, Luca M.; Goto, Hitoshi; Grimme, Stefan; Guo, Rui; Hofmann, Detlef W. M.; Hoja, Johannes; Hylton, Rebecca K.; Iuzzolino, Luca; Jankiewicz, Wojciech; de Jong, Daniël T.; Kendrick, John; de Klerk, Niek J. J.; Ko, Hsin-Yu; Kuleshova, Liudmila N.; Li, Xiayue; Lohani, Sanjaya; Leusen, Frank J. J.; Lund, Albert M.; Lv, Jian; Ma, Yanming; Marom, Noa; Masunov, Artëm E.; McCabe, Patrick; McMahon, David P.; Meekes, Hugo; Metz, Michael P.; Misquitta, Alston J.; Mohamed, Sharmarke; Monserrat, Bartomeu; Needs, Richard J.; Neumann, Marcus A.; Nyman, Jonas; Obata, Shigeaki; Oberhofer, Harald; Oganov, Artem R.; Orendt, Anita M.; Pagola, Gabriel I.; Pantelides, Constantinos C.; Pickard, Chris J.; Podeszwa, Rafal; Price, Louise S.; Price, Sarah L.; Pulido, Angeles; Read, Murray G.; Reuter, Karsten; Schneider, Elia; Schober, Christoph; Shields, Gregory P.; Singh, Pawanpreet; Sugden, Isaac J.; Szalewicz, Krzysztof; Taylor, Christopher R.; Tkatchenko, Alexandre; Tuckerman, Mark E.; Vacarro, Francesca; Vasileiadis, Manolis; Vazquez-Mayagoitia, Alvaro; Vogt, Leslie; Wang, Yanchao; Watson, Rona E.; de Wijs, Gilles A.; Yang, Jack; Zhu, Qiang; Groom, Colin R.

2016-01-01

The sixth blind test of organic crystal structure prediction (CSP) methods has been held, with five target systems: a small nearly rigid molecule, a polymorphic former drug candidate, a chloride salt hydrate, a co-crystal and a bulky flexible molecule. This blind test has seen substantial growth in the number of participants, with the broad range of prediction methods giving a unique insight into the state of the art in the field. Significant progress has been seen in treating flexible molecules, usage of hierarchical approaches to ranking structures, the application of density-functional approximations, and the establishment of new workflows and ‘best practices’ for performing CSP calculations. All of the targets, apart from a single potentially disordered Z′ = 2 polymorph of the drug candidate, were predicted by at least one submission. Despite many remaining challenges, it is clear that CSP methods are becoming more applicable to a wider range of real systems, including salts, hydrates and larger flexible molecules. The results also highlight the potential for CSP calculations to complement and augment experimental studies of organic solid forms. PMID:27484368
Surface Relaxation in Protein Crystals

NASA Technical Reports Server (NTRS)

Boutet, S.; Robinson, I. K.; Hu, Z. W.; Thomas, B. R.; Chernov, A. A.

2002-01-01

Surface X-ray diffraction measurements were performed on (111) growth faces of crystals of the Cellular iron-storage protein horse spleen ferritin. Crystal Trunkation Rods (CTR) were measured. A fit of the measured profile of the CTR revealed a surface roughness of 48 +/- 4.5 A and a top layer spacing contraction of 3.9 +/- 1.5%. In addition to the peak from the CTR, the rocking curves of the crystals displayed unexpected extra peaks. Multiple-scattering is demonstrated to account for them. Future applications of the method could allow the exploration of hydration effects on the growth of protein crystals.
Zirconium fluoride glass - Surface crystals formed by reaction with water

NASA Technical Reports Server (NTRS)

Doremus, R. H.; Bansal, N. P.; Bradner, T.; Murphy, D.

1984-01-01

The hydrated surfaces of a zirconium barium fluoride glass, which has potential for application in optical fibers and other optical elements, were observed by scanning electron microscopy. Crystalline zirconium fluoride was identified by analysis of X-ray diffraction patterns of the surface crystals and found to be the main constituent of the surface material. It was also found that hydrated zirconium fluorides form only in highly acidic fluoride solutions. It is possible that the zirconium fluoride crystals form directly on the glass surface as a result of its depletion of other ions. The solubility of zirconium fluoride is suggested to be probably much lower than that of barium fluoride (0.16 g/100 cu cm at 18 C). Dissolution was determined to be the predominant process in the initial stages of the reaction of the glass with water. Penetration of water into the glass has little effect.
Electric double-layer capacitor based on an ionic clathrate hydrate.

PubMed

Lee, Wonhee; Kwon, Minchul; Park, Seongmin; Lim, Dongwook; Cha, Jong-Ho; Lee, Huen

2013-07-01

Herein, we suggest a new approach to an electric double-layer capacitor (EDLC) that is based on a proton-conducting ionic clathrate hydrate (ICH). The ice-like structures of clathrate hydrates, which are comprised of host water molecules and guest ions, make them suitable for applications in EDLC electrolytes, owing to their high proton conductivities and thermal stabilities. The carbon materials in the ICH Me4NOH⋅5 H2O show a high specific capacitance, reversible charge-discharge behavior, and a long cycle life. The ionic-hydrate complex provides the following advantages in comparison with conventional aqueous and polymer electrolytes: 1) The ICH does not cause leakage problems under normal EDLC operating conditions. 2) The hydrate material can be utilized itself, without requiring any pre-treatments or activation for proton conduction, thus shortening the preparation procedure of the EDLC. 3) The crystallization of the ICH makes it possible to tailor practical EDLC dimensions because of its fluidity as a liquid hydrate. 4) The hydrate solid electrolyte exhibits more-favorable electrochemical stability than aqueous and polymer electrolytes. Therefore, ICH materials are expected to find practical applications in versatile energy devices that incorporate electrochemical systems. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Flash crystallization kinetics of methane (sI) hydrate in a thermoelectrically-cooled microreactor.

PubMed

Chen, Weiqi; Pinho, Bruno; Hartman, Ryan L

2017-09-12

The crystallization kinetics of methane (sI) hydrate were investigated in a thermoelectrically-cooled microreactor with in situ Raman spectroscopy. Step-wise and precise control of the temperature allowed acquisition of reproducible data within minutes, while the nucleation of methane hydrates can take up to 24 h in traditional batch reactors. The propagation rates of methane hydrate (from 3.1-196.3 μm s -1 ) at the gas-liquid interface were measured for different Reynolds' numbers (0.7-68.9), pressures (30.0-80.9 bar), and sub-cooling temperatures (1.0-4.0 K). The precise measurement of the propagation rates and their subsequent analyses revealed a transition from mixed heat-transfer-crystallization-rate-limited to mixed heat-transfer-mass-transfer-crystallization-rate-limited kinetics. A theoretical model, based on heat transfer, mass transfer, and intrinsic crystallization kinetics, was derived for the first time to understand the non-linear relationship between the propagation rate and sub-cooling temperature. The molecular diffusivity of methane within a stagnant film (ahead of the propagation front) was discovered to follow Stokes-Einstein, while calculated Hatta (0.50-0.68), Lewis (128-207), and beta (0.79-116) numbers also confirmed that the diffusive flux influences crystal growth. Understanding methane hydrate crystal growth is important to the atmospheric, oceanic, and planetary sciences and to energy production, storage, and transportation. Our discoveries could someday advance the science of other multiphase, high-pressure, and sub-cooled crystallizations.
Hydrogen-bond coordination in organic crystal structures: statistics, predictions and applications.

PubMed

Galek, Peter T A; Chisholm, James A; Pidcock, Elna; Wood, Peter A

2014-02-01

Statistical models to predict the number of hydrogen bonds that might be formed by any donor or acceptor atom in a crystal structure have been derived using organic structures in the Cambridge Structural Database. This hydrogen-bond coordination behaviour has been uniquely defined for more than 70 unique atom types, and has led to the development of a methodology to construct hypothetical hydrogen-bond arrangements. Comparing the constructed hydrogen-bond arrangements with known crystal structures shows promise in the assessment of structural stability, and some initial examples of industrially relevant polymorphs, co-crystals and hydrates are described.
Inhibition of methane and natural gas hydrate formation by altering the structure of water with amino acids.

PubMed

Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Cho, Seong Jun; Lee, Ju Dong; Lee, Kun-Hong

2016-08-16

Natural gas hydrates are solid hydrogen-bonded water crystals containing small molecular gases. The amount of natural gas stored as hydrates in permafrost and ocean sediments is twice that of all other fossil fuels combined. However, hydrate blockages also hinder oil/gas pipeline transportation, and, despite their huge potential as energy sources, our insufficient understanding of hydrates has limited their extraction. Here, we report how the presence of amino acids in water induces changes in its structure and thus interrupts the formation of methane and natural gas hydrates. The perturbation of the structure of water by amino acids and the resulting selective inhibition of hydrate cage formation were observed directly. A strong correlation was found between the inhibition efficiencies of amino acids and their physicochemical properties, which demonstrates the importance of their direct interactions with water and the resulting dissolution environment. The inhibition of methane and natural gas hydrate formation by amino acids has the potential to be highly beneficial in practical applications such as hydrate exploitation, oil/gas transportation, and flow assurance. Further, the interactions between amino acids and water are essential to the equilibria and dynamics of many physical, chemical, biological, and environmental processes.
Inhibition of methane and natural gas hydrate formation by altering the structure of water with amino acids

PubMed Central

Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Cho, Seong Jun; Lee, Ju Dong; Lee, Kun-Hong

2016-01-01

Natural gas hydrates are solid hydrogen-bonded water crystals containing small molecular gases. The amount of natural gas stored as hydrates in permafrost and ocean sediments is twice that of all other fossil fuels combined. However, hydrate blockages also hinder oil/gas pipeline transportation, and, despite their huge potential as energy sources, our insufficient understanding of hydrates has limited their extraction. Here, we report how the presence of amino acids in water induces changes in its structure and thus interrupts the formation of methane and natural gas hydrates. The perturbation of the structure of water by amino acids and the resulting selective inhibition of hydrate cage formation were observed directly. A strong correlation was found between the inhibition efficiencies of amino acids and their physicochemical properties, which demonstrates the importance of their direct interactions with water and the resulting dissolution environment. The inhibition of methane and natural gas hydrate formation by amino acids has the potential to be highly beneficial in practical applications such as hydrate exploitation, oil/gas transportation, and flow assurance. Further, the interactions between amino acids and water are essential to the equilibria and dynamics of many physical, chemical, biological, and environmental processes. PMID:27526869
Inhibition of methane and natural gas hydrate formation by altering the structure of water with amino acids

NASA Astrophysics Data System (ADS)

Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Cho, Seong Jun; Lee, Ju Dong; Lee, Kun-Hong

2016-08-01

Natural gas hydrates are solid hydrogen-bonded water crystals containing small molecular gases. The amount of natural gas stored as hydrates in permafrost and ocean sediments is twice that of all other fossil fuels combined. However, hydrate blockages also hinder oil/gas pipeline transportation, and, despite their huge potential as energy sources, our insufficient understanding of hydrates has limited their extraction. Here, we report how the presence of amino acids in water induces changes in its structure and thus interrupts the formation of methane and natural gas hydrates. The perturbation of the structure of water by amino acids and the resulting selective inhibition of hydrate cage formation were observed directly. A strong correlation was found between the inhibition efficiencies of amino acids and their physicochemical properties, which demonstrates the importance of their direct interactions with water and the resulting dissolution environment. The inhibition of methane and natural gas hydrate formation by amino acids has the potential to be highly beneficial in practical applications such as hydrate exploitation, oil/gas transportation, and flow assurance. Further, the interactions between amino acids and water are essential to the equilibria and dynamics of many physical, chemical, biological, and environmental processes.
Phase transition and epitaxies between hydrated orthorhombic and anhydrous monoclinic uric acid crystals

NASA Astrophysics Data System (ADS)

Boistelle, R.; Rinaudo, C.

1981-05-01

Anhydrous monoclinic and hydrated orthorhombic uric acid crystals can be nucleated and grown from pure water solutions either separately or together with epitaxial relationships. When crystals of one modification exist in the solution they can act as nucleation substrate for the crystals of the other modification. In both cases the new phase grows epitaxially on the substrate; the mutual orientations are the same but the contact planes are different. In addition, the anhydrous modification grows into the hydrated one which undergoes a phase transition by a dissolution-recrystallization process. It is likely that the same processes occur in human stones made up of uric acids.
Effects of physiological environments on the hydration behavior of mineral trioxide aggregate.

PubMed

Lee, Yuan-Ling; Lee, Bor-Shiunn; Lin, Feng-Huei; Yun Lin, Ava; Lan, Wan-Hong; Lin, Chun-Pin

2004-02-01

Utilizing scanning electron microscope, X-ray diffraction (XRD) and microhardness tests, we evaluated how various physiological environments affect the hydration behavior and physical properties of mineral trioxide aggregate (MTA). We found that the microstructure of hydrated MTA consists of cubic and needle-like crystals. The former comprised the principal structure of MTA, whereas the later were less prominent and formed in the inter-grain spaces between the cubic crystals. MTA samples were hydrated in distilled water, normal saline, pH 7, and pH 5. However, no needle-like crystals were observed in the pH 5 specimens, and erosion of the cubic crystal surfaces was noted. XRD indicated a peak corresponding to Portlandite, a hydration product of MTA, and the peak decreased noticeably in the pH 5 group. The pH 5 specimens' microhardness was also significantly weaker compared to the other three groups (p<0.0001). These findings suggest that physiological environmental effects on MTA formation are determined, in part, by environmental pH and the presence of ions. In particular, an acidic environment of pH 5 adversely affects both the physical properties and the hydration behavior of MTA.
Adsorption of Kinetic Hydrate Inhibitors on Growing Surfaces: A Molecular Dynamics Study.

PubMed

Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki

2018-04-05

We investigate the mechanism of a typical kinetic hydrate inhibitor (KHI), polyvinylcaprolactam (PVCap), which has been applied to prevent hydrate plugs from forming in gas pipe lines, using molecular dynamics simulations of crystal growth of ethylene oxide hydrate. Water-soluble ethylene oxide is chosen as a guest species to avoid problems associated with the presence of the gas phase in the simulation cell such as slow crystal growth. A PVCap dodecamer adsorbs irreversibly on the hydrate surface which grows at supercooling of 3 K when the hydrophobic part of two pendent groups are trapped in open cages at the surface. The amide hydrogen bonds make no contribution to the adsorption. PVCap can adsorb on various crystallographic planes of sI hydrate. This is in contrast to antifreeze proteins, each of which prefers a specific plane of ice. The trapped PVCap gives rise to necessarily the concave surface of the hydrate. The crystal growth rate decreases with increasing surface curvature, indicating that the inhibition by PVCap is explained by the Gibbs-Thomson effect.
Phase transitions in mixed gas hydrates: experimental observations versus calculated data.

PubMed

Schicks, Judith M; Naumann, Rudolf; Erzinger, Jörg; Hester, Keith C; Koh, Carolyn A; Sloan, E Dendy

2006-06-15

This paper presents the phase behavior of multicomponent gas hydrate systems formed from primarily methane with small amounts of ethane and propane. Experimental conditions were typically in a pressure range between 1 and 6 MPa, and the temperature range was between 260 and 290 K. These multicomponent systems have been investigated using a variety of techniques including microscopic observations, Raman spectroscopy, and X-ray diffraction. These techniques, used in combination, allowed for measurement of the hydrate structure and composition, while observing the morphology of the hydrate crystals measured. The hydrate formed immediately below the three-phase line (V-L --> V-L-H) and contained crystals that were both light and dark in appearance. The light crystals, which visually were a single solid phase, showed a spectroscopic indication for the presence of occluded free gas in the hydrate. In contrast, the dark crystals were measured to be structure II (sII) without the presence of these occluded phases. Along with hydrate measurements near the decomposition line, an unexpected transformation process was visually observed at P-T-conditions in the stability field of the hydrates. Larger crystallites transformed into a foamy solid upon cooling over this transition line (between 5 and 10 K below the decomposition temperature). Below the transition line, a mixture of sI and sII was detected. This is the first time that these multicomponent systems have been investigated at these pressure and temperature conditions using both visual and spectroscopic techniques. These techniques enabled us to observe and measure the unexpected transformation process showing coexistence of different gas hydrate phases.
Absorbing a Little Water: The Structural, Thermodynamic, and Kinetic Relationship between Pyrogallol and Its Tetarto-Hydrate

PubMed Central

2013-01-01

The anhydrate and the stoichiometric tetarto-hydrate of pyrogallol (0.25 mol water per mol pyrogallol) are both storage stable at ambient conditions, provided that they are phase pure, with the system being at equilibrium at aw (water activity) = 0.15 at 25 °C. Structures have been derived from single crystal and powder X-ray diffraction data for the anhydrate and hydrate, respectively. It is notable that the tetarto-hydrate forms a tetragonal structure with water in channels, a framework that although stabilized by water, is found as a higher energy structure on a computationally generated crystal energy landscape, which has the anhydrate crystal structure as the most stable form. Thus, a combination of slurry experiments, X-ray diffraction, spectroscopy, moisture (de)sorption, and thermo-analytical methods with the computationally generated crystal energy landscape and lattice energy calculations provides a consistent picture of the finely balanced hydration behavior of pyrogallol. In addition, two monotropically related dimethyl sulfoxide monosolvates were found in the accompanying solid form screen. PMID:24027438
Absorbing a Little Water: The Structural, Thermodynamic, and Kinetic Relationship between Pyrogallol and Its Tetarto-Hydrate.

PubMed

Braun, Doris E; Bhardwaj, Rajni M; Arlin, Jean-Baptiste; Florence, Alastair J; Kahlenberg, Volker; Griesser, Ulrich J; Tocher, Derek A; Price, Sarah L

2013-09-04

The anhydrate and the stoichiometric tetarto-hydrate of pyrogallol (0.25 mol water per mol pyrogallol) are both storage stable at ambient conditions, provided that they are phase pure, with the system being at equilibrium at a w (water activity) = 0.15 at 25 °C. Structures have been derived from single crystal and powder X-ray diffraction data for the anhydrate and hydrate, respectively. It is notable that the tetarto-hydrate forms a tetragonal structure with water in channels, a framework that although stabilized by water, is found as a higher energy structure on a computationally generated crystal energy landscape, which has the anhydrate crystal structure as the most stable form. Thus, a combination of slurry experiments, X-ray diffraction, spectroscopy, moisture (de)sorption, and thermo-analytical methods with the computationally generated crystal energy landscape and lattice energy calculations provides a consistent picture of the finely balanced hydration behavior of pyrogallol. In addition, two monotropically related dimethyl sulfoxide monosolvates were found in the accompanying solid form screen.

Transformation and crystallization energetics of synthetic and biogenic amorphous calcium carbonate.

PubMed

Radha, A V; Forbes, Tori Z; Killian, Christopher E; Gilbert, P U P A; Navrotsky, Alexandra

2010-09-21

Amorphous calcium carbonate (ACC) is a metastable phase often observed during low temperature inorganic synthesis and biomineralization. ACC transforms with aging or heating into a less hydrated form, and with time crystallizes to calcite or aragonite. The energetics of transformation and crystallization of synthetic and biogenic (extracted from California purple sea urchin larval spicules, Strongylocentrotus purpuratus) ACC were studied using isothermal acid solution calorimetry and differential scanning calorimetry. Transformation and crystallization of ACC can follow an energetically downhill sequence: more metastable hydrated ACC → less metastable hydrated ACC ⇒ anhydrous ACC ∼ biogenic anhydrous ACC ⇒ vaterite → aragonite → calcite. In a given reaction sequence, not all these phases need to occur. The transformations involve a series of ordering, dehydration, and crystallization processes, each lowering the enthalpy (and free energy) of the system, with crystallization of the dehydrated amorphous material lowering the enthalpy the most. ACC is much more metastable with respect to calcite than the crystalline polymorphs vaterite or aragonite. The anhydrous ACC is less metastable than the hydrated, implying that the structural reorganization during dehydration is exothermic and irreversible. Dehydrated synthetic and anhydrous biogenic ACC are similar in enthalpy. The transformation sequence observed in biomineralization could be mainly energetically driven; the first phase deposited is hydrated ACC, which then converts to anhydrous ACC, and finally crystallizes to calcite. The initial formation of ACC may be a first step in the precipitation of calcite under a wide variety of conditions, including geological CO(2) sequestration.
Physicochemical Properties of α-Form Hydrated Crystalline Phase of 3-(10-Carboxydecyl)-1,1,1,3,5,5,5-heptamethyl Trisiloxane/Higher alcohol/Polyoxyethylene (5 mol) Glyceryl monostearate/Water System.

PubMed

Uyama, Makoto; Araki, Hidefumi; Fukuhara, Tadao; Watanabe, Kei

2018-06-07

The α-form hydrated crystalline phase (often called as an α-gel) is one of the hydrated crystalline phases which can be exhibited by surfactants and lipids. In this study, a novel system of an α-form hydrated crystal was developed, composed of 3-(10-carboxydecyl)-1,1,1,3,5,5,5-heptamethyl trisiloxane (CDTS), polyoxyethylene (5 mol) glyceryl monostearate (GMS-5), higher alcohol. This is the first report to indicate that a silicone surfactant can form an α-form hydrated crystal. The physicochemical properties of this system were characterized by small and wide angle X-ray scattering (SWAXS), differential scanning calorimetry (DSC), and diffusion-ordered NMR spectroscopy (DOSY) experiments. SWAXS and DSC measurements revealed that a plurality of crystalline phases coexist in the CDTS/higher alcohol/water ternary system. By adding GMS-5 to the ternary system, however, a wide region of a single α-form hydrated crystalline phase was obtained. The self-diffusion coefficients (D sel ) from the NMR measurements suggested that all of the CDTS, GMS-5, and higher alcohol molecules were incorporated into the same α-form hydrated crystals.
One-step synthesis of hierarchically porous hybrid TiO2 hollow spheres with high photocatalytic activity

NASA Astrophysics Data System (ADS)

Liu, Ruiping; Ren, Feng; Yang, Jinlin; Su, Weiming; Sun, Zhiming; Zhang, Lei; Wang, Chang-an

2016-03-01

Hierarchically porous hybrid TiO2 hollow spheres were solvothermally synthesized successfully by using tetrabutyl titanate as titanium precursor and hydrated metal sulfates as soft templates. The as-prepared TiO2 spheres with hierarchically pore structures and high specific surface area and pore volume consisted of highly crystallized anatase TiO2 nanocrystals hybridized with a small amount of metal oxide from the hydrated sulfate. The proposed hydrated-sulfate assisted solvothermal (HAS) synthesis strategy was demonstrated to be widely applicable to various systems. Evaluation of the hybrid TiO2 hollow spheres for the photo-decomposition of methyl orange (MO) under visible-light irradiation revealed that they exhibited excellent photocatalytic activity and durability.
Water Sorption in Electron-Beam Evaporated SiO2 on QCM Crystals and Its Influence on Polymer Thin Film Hydration Measurements.

PubMed

Kushner, Douglas I; Hickner, Michael A

2017-05-30

Spectroscopic ellipsometry (SE) and quartz crystal microbalance (QCM) measurements are two critical characterization techniques routinely employed for hydration studies of polymer thin films. Water uptake by thin polymer films is an important area of study to investigate antifouling surfaces, to probe the swelling of thin water-containing ionomer films, and to conduct fundamental studies of polymer brush hydration and swelling. SiO 2 -coated QCM crystals, employed as substrates in many of these hydration studies, show porosity in the thin electron-beam (e-beam) evaporated SiO 2 layer. The water sorption into this porous SiO 2 layer requires correction of the optical and mass characterization of the hydrated polymer due to changes in the SiO 2 layer as it sorbs water. This correction is especially important when experiments on SiO 2 -coated QCM crystals are compared to measurements on Si wafers with dense native SiO 2 layers. Water adsorption filling void space during hydration in ∼200-260 nm thick SiO 2 layers deposited on a QCM crystal resulted in increased refractive index of the layer during water uptake experiments. The increased refractive index led to artificially higher polymer swelling in the optical modeling of the hydration experiments. The SiO 2 -coated QCM crystals showed between 6 and 8% void as measured by QCM and SE, accounting for 60%-85% of the measured polymer swelling in the low humidity regime (<20% RH) and 25%-40% of the polymer swelling in the high humidity regime (>70% RH) from optical modeling for 105 and 47 nm thick sulfonated polymer films. Correcting the refractive index of the SiO 2 layer for its water content resulted in polymer swelling that successfully resembled swelling measured on a silicon wafer with nonporous native oxide.
Transformation and crystallization energetics of synthetic and biogenic amorphous calcium carbonate

PubMed Central

Radha, A. V.; Forbes, Tori Z.; Killian, Christopher E.; Gilbert, P. U. P. A.; Navrotsky, Alexandra

2010-01-01

Amorphous calcium carbonate (ACC) is a metastable phase often observed during low temperature inorganic synthesis and biomineralization. ACC transforms with aging or heating into a less hydrated form, and with time crystallizes to calcite or aragonite. The energetics of transformation and crystallization of synthetic and biogenic (extracted from California purple sea urchin larval spicules, Strongylocentrotus purpuratus) ACC were studied using isothermal acid solution calorimetry and differential scanning calorimetry. Transformation and crystallization of ACC can follow an energetically downhill sequence: more metastable hydrated ACC → less metastable hydrated ACC⇒anhydrous ACC ∼ biogenic anhydrous ACC⇒vaterite → aragonite → calcite. In a given reaction sequence, not all these phases need to occur. The transformations involve a series of ordering, dehydration, and crystallization processes, each lowering the enthalpy (and free energy) of the system, with crystallization of the dehydrated amorphous material lowering the enthalpy the most. ACC is much more metastable with respect to calcite than the crystalline polymorphs vaterite or aragonite. The anhydrous ACC is less metastable than the hydrated, implying that the structural reorganization during dehydration is exothermic and irreversible. Dehydrated synthetic and anhydrous biogenic ACC are similar in enthalpy. The transformation sequence observed in biomineralization could be mainly energetically driven; the first phase deposited is hydrated ACC, which then converts to anhydrous ACC, and finally crystallizes to calcite. The initial formation of ACC may be a first step in the precipitation of calcite under a wide variety of conditions, including geological CO2 sequestration. PMID:20810918
Hydration-induced crystalline transformation of starch polymer under ambient conditions.

PubMed

Qiao, Dongling; Zhang, Binjia; Huang, Jing; Xie, Fengwei; Wang, David K; Jiang, Fatang; Zhao, Siming; Zhu, Jie

2017-10-01

With synchrotron small/wide-angle X-ray scattering (SAXS/WAXS), we revealed that post-harvest hydration at ambient conditions can further alter the starch crystalline structure. The hydration process induced the alignment of starch helices into crystalline lamellae, irrespective of the starch type (A- or B-). In this process, non-crystalline helices were probably packed with water molecules to form new crystal units, thereby enhancing the overall concentration of starch crystallinity. In particular, a fraction of the monoclinic crystal units of the A-type starches encapsulated water molecules during hydration, leading to the outward movement of starch helices. Such movement resulted in the transformation of monoclinic units into hexagonal units, which was associated with the B-type crystallites. Hence, the hydration under ambient conditions could enhance the B-polymorphic features for both A-type and B-type starches. The new knowledge obtained here may guide the design of biopolymer-based liquid crystal materials with controlled lattice regularity and demanded features. Copyright © 2017 Elsevier B.V. All rights reserved.
Temperature- and pressure-dependent structural transformation of methane hydrates in salt environments

NASA Astrophysics Data System (ADS)

Shin, Donghoon; Cha, Minjun; Yang, Youjeong; Choi, Seunghyun; Woo, Yesol; Lee, Jong-Won; Ahn, Docheon; Im, Junhyuck; Lee, Yongjae; Han, Oc Hee; Yoon, Ji-Ho

2017-03-01

Understanding the stability of volatile species and their compounds under various surface and subsurface conditions is of great importance in gaining insights into the formation and evolution of planetary and satellite bodies. We report the experimental results of the temperature- and pressure-dependent structural transformation of methane hydrates in salt environments using in situ synchrotron X-ray powder diffraction, solid-state nuclear magnetic resonance, and Raman spectroscopy. We find that under pressurized and concentrated brine solutions methane hydrate forms a mixture of type I clathrate hydrate, ice, and hydrated salts. Under a low-pressure condition, however, the methane hydrates are decomposed through a rapid sublimation of water molecules from the surface of hydrate crystals, while NaCl · 2H2O undergoes a phase transition into a crystal growth of NaCl via the migration of salt ions. In ambient pressure conditions, the methane hydrate is fully decomposed in brine solutions at temperatures above 252 K, the eutectic point of NaCl · 2H2O.
DEWATERING WASTEWATER TREATMENT SLUDGE BY CLATHRATE FREEZING: A BENCH-SCALE FEASIBILITY STUDY

EPA Science Inventory

Laboratory studies were performed to prove the concept and feasibility for a novel technology to dewater sludges. This involves the formation of solid hydrate crystals of water and specific clathrate-forming agents followed by separation of the hydrate crystal solids from the slu...
Crystal structure of zwitterionic bisimidazolium sulfonates

NASA Astrophysics Data System (ADS)

Kohmoto, Shigeo; Okuyama, Shinpei; Yokota, Nobuyuki; Takahashi, Masahiro; Kishikawa, Keiki; Masu, Hyuma; Azumaya, Isao

2012-05-01

Crystal structures of three zwitterionic bisimidazolium salts 1-3 in which imidazolium sulfonate moieties were connected with aromatic linkers, p-xylylene, 4,4'-dimethylenebiphenyl, and phenylene, respectively, were examined. The latter two were obtained as hydrates. An S-shaped molecular structure in which the sulfonate moiety was placed on the imidazolium ring was observed for 1. A helical array of hydrated water molecules was obtained for 2 while a linear array of hydrated water molecules was observed for 3.
Identification of Clathrate Hydrates, Hexagonal Ice, Cubic Ice, and Liquid Water in Simulations: the CHILL+ Algorithm.

PubMed

Nguyen, Andrew H; Molinero, Valeria

2015-07-23

Clathrate hydrates and ice I are the most abundant crystals of water. The study of their nucleation, growth, and decomposition using molecular simulations requires an accurate and efficient algorithm that distinguishes water molecules that belong to each of these crystals and the liquid phase. Existing algorithms identify ice or clathrates, but not both. This poses a challenge for cases in which ice and hydrate coexist, such as in the synthesis of clathrates from ice and the formation of ice from clathrates during self-preservation of methane hydrates. Here we present an efficient algorithm for the identification of clathrate hydrates, hexagonal ice, cubic ice, and liquid water in molecular simulations. CHILL+ uses the number of staggered and eclipsed water-water bonds to identify water molecules in cubic ice, hexagonal ice, and clathrate hydrate. CHILL+ is an extension of CHILL (Moore et al. Phys. Chem. Chem. Phys. 2010, 12, 4124-4134), which identifies hexagonal and cubic ice but not clathrates. In addition to the identification of hydrates, CHILL+ significantly improves the detection of hexagonal ice up to its melting point. We validate the use of CHILL+ for the identification of stacking faults in ice and the nucleation and growth of clathrate hydrates. To our knowledge, this is the first algorithm that allows for the simultaneous identification of ice and clathrate hydrates, and it does so in a way that is competitive with respect to existing methods used to identify any of these crystals.
Hydration behaviors of calcium silicate-based biomaterials.

PubMed

Lee, Yuan-Ling; Wang, Wen-Hsi; Lin, Feng-Huie; Lin, Chun-Pin

2017-06-01

Calcium silicate (CS)-based biomaterials, such as mineral trioxide aggregate (MTA), have become the most popular and convincing material used in restorative endodontic treatments. However, the commercially available CS-based biomaterials all contain different minor additives, which may affect their hydration behaviors and material properties. The purpose of this study was to evaluate the hydration behavior of CS-based biomaterials with/without minor additives. A novel CS-based biomaterial with a simplified composition, without mineral oxides as minor additives, was produced. The characteristics of this biomaterial during hydration were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectrometry. The hydration behaviors of commercially available gray and white MTAs with mineral oxide as minor additives were also evaluated for reference. For all three test materials, the XRD analysis revealed similar diffraction patterns after hydration, but MTAs presented a significant decrease in the intensities of Bi 2 O 3 -related peaks. SEM results demonstrated similar porous microstructures with some hexagonal and facetted crystals on the outer surfaces. In addition, compared to CS with a simplified composition, the FTIR plot indicated that hydrated MTAs with mineral oxides were better for the polymerization of calcium silicate hydrate (CSH), presenting Si-O band shifting to higher wave numbers, and contained more water crystals within CSH, presenting sharper bands for O-H bending. Mineral oxides might not result in significant changes in the crystal phases or microstructures during the hydration of CS-based biomaterials, but these compounds affected the hydration behavior at the molecular level. Copyright © 2016. Published by Elsevier B.V.
Pectin as an Extraordinary Natural Kinetic Hydrate Inhibitor

PubMed Central

Xu, Shurui; Fan, Shuanshi; Fang, Songtian; Lang, Xuemei; Wang, Yanhong; Chen, Jun

2016-01-01

Pectin as a novel natural kinetic hydrate inhibitor, expected to be eco-friendly and sufficiently biodegradable, was studied in this paper. The novel crystal growth inhibition (CGI) and standard induction time methods were used to evaluate its effect as hydrate inhibitor. It could successfully inhibit methane hydrate formation at subcooling temperature up to 12.5 °C and dramatically slowed the hydrate crystal growth. The dosage of pectin decreased by 66% and effective time extended 10 times than typical kinetic inhibitor. Besides, its maximum growth rate was no more than 2.0%/h, which was far less than 5.5%/h of growth rate for PVCap at the same dosage. The most prominent feature was that it totally inhibited methane hydrate crystal rapid growth when hydrate crystalline occurred. Moreover, in terms of typical natural inhibitors, the inhibition activity of pectin increased 10.0-fold in induction time and 2.5-fold in subcooling temperature. The extraordinary inhibition activity is closely related to its hydrogen bonding interaction with water molecules and the hydrophilic structure. Finally, the biodegradability and economical efficiency of pectin were also taken into consideration. The results showed the biodegradability improved 75.0% and the cost reduced by more than 73.3% compared to typical commercial kinetic inhibitors. PMID:26996773
Polymorphic Protein Crystal Growth: Influence of Hydration and Ions in Glucose Isomerase

PubMed Central

Gillespie, C. M.; Asthagiri, D.; Lenhoff, A. M.

2014-01-01

Crystal polymorphs of glucose isomerase were examined to characterize the properties and to quantify the energetics of protein crystal growth. Transitions of polymorph stability were measured in poly(ethylene glycol)/NaCl solutions, and one transition point was singled out for more detailed quantitative analysis. Single crystal x-ray diffraction was used to confirm space groups and identify complementary crystal structures. Crystal polymorph stability was found to depend on the NaCl concentration, with stability transitions requiring > 1 M NaCl combined with a low concentration of PEG. Both salting-in and salting-out behavior was observed and was found to differ for the two polymorphs. For NaCl concentrations above the observed polymorph transition, the increase in solubility of the less stable polymorph together with an increase in the osmotic second virial coefficient suggests that changes in protein hydration upon addition of salt may explain the experimental trends. A combination of atomistic and continuum models was employed to dissect this behavior. Molecular dynamics simulations of the solvent environment were interpreted using quasi-chemical theory to understand changes in protein hydration as a function of NaCl concentration. The results suggest that protein surface hydration and Na+ binding may introduce steric barriers to contact formation, resulting in polymorph selection. PMID:24955067
Grand canonical ensemble Monte Carlo simulation of the dCpG/proflavine crystal hydrate.

PubMed

Resat, H; Mezei, M

1996-09-01

The grand canonical ensemble Monte Carlo molecular simulation method is used to investigate hydration patterns in the crystal hydrate structure of the dCpG/proflavine intercalated complex. The objective of this study is to show by example that the recently advocated grand canonical ensemble simulation is a computationally efficient method for determining the positions of the hydrating water molecules in protein and nucleic acid structures. A detailed molecular simulation convergence analysis and an analogous comparison of the theoretical results with experiments clearly show that the grand ensemble simulations can be far more advantageous than the comparable canonical ensemble simulations.
Physical properties of organic fullerene cocrystals

NASA Astrophysics Data System (ADS)

Macovez, Roberto

2017-12-01

The basic facts and fundamental properties of binary fullerene cocrystals are reviewed, focusing especially on solvates and salts of Buckminsterfullerene (C60), and hydrates of hydrophilic C60 derivatives. The examined properties include the lattice structure and the presence of orientational disorder and/or rotational dynamics (of both fullerenes and cocrystallizing moieties), thermodynamic properties such as decomposition enthalpies, and charge transport properties. Both thermodynamic properties and molecular orientational disorder shed light on the extent of intermolecular interactions in these binary solid-state systems. Comparison is carried out also with pristine fullerite and with the solid phases of functionalized C60. Interesting experimental findings on binary fullerene cocrystals include the simultaneous occurrence of rotations of both constituent molecular species, crystal morphologies reminiscent of quasi-crystalline behaviour, the observation of proton conduction in hydrate solids of hydrophilic fullerene derivatives, and the production of super-hard carbon materials by application of high pressures on solvated fullerene crystals.
ON THE FREEZING AND IDENTIFICATION OF LIPID MONOLAYER 2-D ARRAYS FOR CRYOELECTRON MICROSCOPY

PubMed Central

Taylor, Dianne W.; Kelly, Deborah F.; Cheng, Anchi; Taylor, Kenneth A.

2008-01-01

Lipid monolayers provide a convenient vehicle for the crystallization of biological macromolecules for 3-D electron microscopy. Although numerous examples of 3-D images from 2-D protein arrays have been described from negatively stained specimens, only six structures have been done from frozen hydrated specimens. We describe here a method that makes high quality frozen-hydrated specimens of lipid monolayer arrays for cryoelectron microscopy. The method uses holey carbon films with patterned holes for monolayer recovery, blotting and plunge freezing to produce thin aqueous films which cover >90% of the available grid area. With this method, even specimens with relatively infrequent crystals can be screened using automated data collection techniques. Though developed for microscopic examination of 2-D arrays, the method may have wider application to the preparation of single particle specimens for 3-D image reconstruction. PMID:17561414
Evidence from mixed hydrate nucleation for a funnel model of crystallization.

PubMed

Hall, Kyle Wm; Carpendale, Sheelagh; Kusalik, Peter G

2016-10-25

The molecular-level details of crystallization remain unclear for many systems. Previous work has speculated on the phenomenological similarities between molecular crystallization and protein folding. Here we demonstrate that molecular crystallization can involve funnel-shaped potential energy landscapes through a detailed analysis of mixed gas hydrate nucleation, a prototypical multicomponent crystallization process. Through this, we contribute both: (i) a powerful conceptual framework for exploring and rationalizing molecular crystallization, and (ii) an explanation of phenomenological similarities between protein folding and crystallization. Such funnel-shaped potential energy landscapes may be typical of broad classes of molecular ordering processes, and can provide a new perspective for both studying and understanding these processes.
Evidence from mixed hydrate nucleation for a funnel model of crystallization

PubMed Central

Hall, Kyle Wm.; Carpendale, Sheelagh; Kusalik, Peter G.

2016-01-01

The molecular-level details of crystallization remain unclear for many systems. Previous work has speculated on the phenomenological similarities between molecular crystallization and protein folding. Here we demonstrate that molecular crystallization can involve funnel-shaped potential energy landscapes through a detailed analysis of mixed gas hydrate nucleation, a prototypical multicomponent crystallization process. Through this, we contribute both: (i) a powerful conceptual framework for exploring and rationalizing molecular crystallization, and (ii) an explanation of phenomenological similarities between protein folding and crystallization. Such funnel-shaped potential energy landscapes may be typical of broad classes of molecular ordering processes, and can provide a new perspective for both studying and understanding these processes. PMID:27790987
Crystal water as the mol-ecular glue for obtaining different co-crystal ratios: the case of gallic acid tris-caffeine hexa-hydrate.

PubMed

Vella-Zarb, L; Baisch, U

2018-04-01

The crystal structure of the hexa-hydrate co-crystal of gallic acid and caffeine, C 7 H 6 O 5 ·3C 8 H 10 N 4 O 2 ·6H 2 O or GAL3CAF·6H 2 O , is a remarkable example of the importance of hydrate water acting as structural glue to facilitate the crystallization of two components of different stoichiometries and thus to compensate an imbalance of hydrogen-bond donors and acceptors. The water mol-ecules provide the additional hydrogen bonds required to form a crystalline solid. Whereas the majority of hydrogen bonds forming the inter-molecular network between gallic acid and caffeine are formed by crystal water, only one direct classical hydrogen bond between two mol-ecules is formed between the carb-oxy-lic oxygen of gallic acid and the carbonyl oxygen of caffeine with d ( D ⋯ A ) = 2.672 (2) Å. All other hydrogen bonds either involve crystal water or utilize protonated carbon atoms as donors.
The influence of ion hydration on nucleation and growth of LiF crystals in aqueous solution.

PubMed

Lanaro, G; Patey, G N

2018-01-14

Molecular dynamics (MD) simulations are employed to investigate crystal nucleation and growth in oversaturated aqueous LiF solutions. Results obtained for a range of temperatures provide evidence that the rate of crystal growth is determined by a substantial energy barrier (∼49 kJ mol -1 ) related to the loss of water from the ion hydration shells. Employing direct MD simulations, we do not observe spontaneous nucleation of LiF crystals at 300 K, but nucleation is easily observable in NVT simulations at 500 K. This contrasts with the NaCl case, where crystal nucleation is directly observed in similar simulations at 300 K. Based on these observations, together with a detailed analysis of ion clustering in metastable LiF solutions, we argue that the ion dehydration barrier also plays a key role in crystal nucleation. The hydration of the relatively small Li + and F - ions strongly influences the probability of forming large, crystal-like ion clusters, which are a necessary precursor to nucleation. This important factor is not accounted for in classical nucleation theory.

The influence of ion hydration on nucleation and growth of LiF crystals in aqueous solution

NASA Astrophysics Data System (ADS)

Lanaro, G.; Patey, G. N.

2018-01-01

Molecular dynamics (MD) simulations are employed to investigate crystal nucleation and growth in oversaturated aqueous LiF solutions. Results obtained for a range of temperatures provide evidence that the rate of crystal growth is determined by a substantial energy barrier (˜49 kJ mol-1) related to the loss of water from the ion hydration shells. Employing direct MD simulations, we do not observe spontaneous nucleation of LiF crystals at 300 K, but nucleation is easily observable in NVT simulations at 500 K. This contrasts with the NaCl case, where crystal nucleation is directly observed in similar simulations at 300 K. Based on these observations, together with a detailed analysis of ion clustering in metastable LiF solutions, we argue that the ion dehydration barrier also plays a key role in crystal nucleation. The hydration of the relatively small Li+ and F- ions strongly influences the probability of forming large, crystal-like ion clusters, which are a necessary precursor to nucleation. This important factor is not accounted for in classical nucleation theory.
An ikaite record of late Holocene climate at the Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Lu, Zunli; Rickaby, Rosalind E. M.; Kennedy, Hilary; Kennedy, Paul; Pancost, Richard D.; Shaw, Samuel; Lennie, Alistair; Wellner, Julia; Anderson, John B.

2012-04-01

Calcium carbonate can crystallize in a hydrated form as ikaite at low temperatures. The hydration water in ikaite grown in laboratory experiments records the δ18O of ambient water, a feature potentially useful for reconstructing δ18O of local seawater. We report the first downcore δ18O record of natural ikaite hydration waters and crystals collected from the Antarctic Peninsula (AP), a region sensitive to climate fluctuations. We are able to establish the zone of ikaite formation within shallow sediments, based on porewater chemical and isotopic data. Having constrained the depth of ikaite formation and δ18O of ikaite crystals and hydration waters, we are able to infer local changes in fjord δ18O versus time during the late Holocene. This ikaite record qualitatively supports that both the Medieval Warm Period and Little Ice Age extended to the Antarctic Peninsula.
Synthesis, crystal structure, and structural conversion of Ni molybdate hydrate NiMoO 4· nH 2O

NASA Astrophysics Data System (ADS)

Eda, Kazuo; Kato, Yasuyuki; Ohshiro, Yu; Sugitani, Takamitu; Whittingham, M. Stanley

2010-06-01

The synthesis and crystal structure of NiMoO 4· nH 2O were investigated. The hydrate crystallized in the triclinic system with space group P-1, Z=4 with unit cell parameters of a=6.7791(2) Å, b=6.8900(2) Å, c=9.2486(2) Å, α=76.681(2)°, β=83.960(2)°, γ=74.218(2)°. Its ideal chemical composition was NiMoO 4·3/4H 2O rather than NiMoO 4·1H 2O. Under hydrothermal conditions the hydrate turned directly into α-NiMoO 4 above 483 K, giving nanorods thinner than the crystallites of the mother hydrate. On the other hand, it turned into Anderson type of polyoxomolybdate via a solid-solution process in a molybdate solution at room temperature.
Determination of Methane Hydrate Solubility in the Absence of Vapor Phase by in-situ Raman Spectroscopy

NASA Astrophysics Data System (ADS)

Lu, W.; Chou, I.; Burruss, R.

2006-12-01

Prediction of the occurrence, distribution, and evolution of methane hydrate in porous marine sediments requires information on solubilities of methane hydrate in water. Solubilities of methane hydrate in the presence of a vapor phase are well established, but those in the absence of a vapor phase are not well defined with differences up to 30%. We have measured methane concentrations in pure water in equilibrium with sI methane hydrate, in the absence of vapor phase, by in-situ Raman spectroscopy at temperatures (T) from 2 to 20 (± 0.3) °C and pressures (P) at 10, 20, 30, and 40 (± 0.4%) MPa. Methane hydrate was synthesized in a high-pressure capillary optical cell (Chou et al., 2005; Advances in High-Pressure Technology for Geophysical Applications. Ed. J. Chen et al., Chapter 24, p. 475, Elsevier). A small quantity of methane was first loaded in an evacuated cell and then pressurized by water. Hydrate crystals were formed near the liquid-vapor interface near the enclosed end of the optical tube at room T, and were then placed at the center of a USGS-type heating-cooling stage. By adjusting sample P and T, the crystals went through dissolution-formation cycles three to four times in three days until the vapor phase was completely consumed and several crystals (typically 40 x 40 x 10 μm) were formed. These crystals were located at about 200 μm from the enclosed end and were about 20 to 40 μm from each other. Raman spectra were collected for the liquid phase adjacent to hydrate crystals near the enclosed end of the tube. A volumetric decrease in crystal size was observed away from the sampling spot; however, no such volumetric decrease was observed in or near the sampling spot. Therefore, equilibrium was likely established locally within the sampling area. The results are represented by the following linear isobaric equations: 10 MPa: ln [X(CH4)] = 0.06175 T - 6.79507; r2 = 0.9991 (n = 6) 20 MPa: ln [X(CH4)] = 0.06170 T - 6.82816; r2 = 0.9985 (n = 6) 30 MPa: ln [X(CH4)] = 0.06186 T - 6.87463; r2 = 0.9971 (n = 10) 40 MPa: ln [X(CH4)] = 0.06147 T - 6.95384; r2 = 0.9983 (n = 22), where X(CH4) is the mole fraction of CH4 in solution and n is the number of observations. These results are in good agreement with measurements by Servio and Englezos (2002, J. Chem. Eng. Data., 47, p. 87) and Kim et al. (2003, Ind. Eng. Chem. Res., 42, p. 2409) and predictions by Glew et al. (2003, Can. J. of Chem., 81, p.1443). However, our solubilities are about 10 to 30% higher than those measured by Yang et al. (2001, Fluid Phase Equilibria, 185, p. 53) and those predicted by Davie et al. (2004, Marine Geol., 203, p. 177) and Zhang and Xu (2003, Earth and Planet. Sci. Lett., 213, p. 133). It should be noted that our solubilities are minimum values if an equilibrium state was not reached during our measurements. When compared with previous direct sampling method, the advantages of our method include: (1) the use of in-situ Raman signals for methane concentration measurements eliminates possible uncertainty caused by pressure drops during sampling; (2) simple and efficient; and (3) high-pressure data can be obtained without safety concern.
The effect of temperature and moisture on the amorphous-to-crystalline transformation of stavudine.

PubMed

Strydom, Schalk; Liebenberg, Wilna; Yu, Lian; de Villiers, Melgardt

2009-09-08

Stavudine is a nucleoside reverse transcriptase inhibitor active against HIV, and is known to exist in two polymorphic forms designated as forms I and II, and a hydrate form III. An amorphous solid of stavudine was successfully prepared and characterized during this investigation. A comprehensive evaluation of the stability of this amorphous solid showed that the amorphous solid transforms to either form II (anhydrous) or form III (hydrate) when exposed to temperature, in the absence or presence of moisture, respectively. The amorphous-to-hydrate transformation occurred at relatively low RH (>32%) and led to the formation of crystal aggregates of the hydrated form. Steady state growth rate analyses also showed that the amorphous-to-crystalline transformation occurs at a greater rate in the presence of moisture, compared to the transformation at the same temperature in a dry environment. Crystal growth studies showed that it is possible to stabilize the amorphous solid of stavudine against crystal transformations in the absence of moisture by coating it with poly(methyl methacrylate). However, this polymer coating could not prevent crystal growth from the amorphous solid during exposure to moisture.
Crystal structure, stability and spectroscopic properties of methane and CO2 hydrates.

PubMed

Martos-Villa, Ruben; Francisco-Márquez, Misaela; Mata, M Pilar; Sainz-Díaz, C Ignacio

2013-07-01

Methane hydrates are highly present in sea-floors and in other planets and their moons. Hence, these compounds are of great interest for environment, global climate change, energy resources, and Cosmochemistry. The knowledge of stability and physical-chemical properties of methane hydrate crystal structure is important for evaluating some new green becoming technologies such as, strategies to produce natural gas from marine methane hydrates and simultaneously store CO2 as hydrates. However, some aspects related with their stability, spectroscopic and other chemical-physical properties of both hydrates are not well understood yet. The structure and stability of crystal structure of methane and CO2 hydrates have been investigated by means of calculations with empirical interatomic potentials and quantum-mechanical methods based on Hartree-Fock and Density Functional Theory (DFT) approximations. Molecular Dynamic simulations have been also performed exploring different configurations reproducing the experimental crystallographic properties. Spectroscopic properties have also been studied. Frequency shifts of the main vibration modes were observed upon the formation of these hydrates, confirming that vibration stretching peaks of C-H at 2915cm(-1) and 2905cm(-1) are due to methane in small and large cages, respectively. Similar effect is observed in the CO2 clathrates. The guest-host binding energy in these clathrates calculated with different methods are compared and discussed in terms of adequacy of empirical potentials and DFT methods for describing the interactions between gas guest and the host water cage, proving an exothermic nature of methane and CO2 hydrates formation process. Copyright © 2013 Elsevier Inc. All rights reserved.
An evaluation of adhesive sample holders for advanced crystallographic experiments

PubMed Central

Mazzorana, Marco; Sanchez-Weatherby, Juan; Sandy, James; Lobley, Carina M. C.; Sorensen, Thomas

2014-01-01

The hydration state of macromolecular crystals often affects their overall order and, ultimately, the quality of the X-ray diffraction pattern that they produce. Post-crystallization techniques that alter the solvent content of a crystal may induce rearrangement within the three-dimensional array making up the crystal, possibly resulting in more ordered packing. The hydration state of a crystal can be manipulated by exposing it to a stream of air at controlled relative humidity in which the crystal can equilibrate. This approach provides a way of exploring crystal hydration space to assess the diffraction capabilities of existing crystals. A key requirement of these experiments is to expose the crystal directly to the dehydrating environment by having the minimum amount of residual mother liquor around it. This is usually achieved by placing the crystal on a flat porous support (Kapton mesh) and removing excess liquid by wicking. Here, an alternative approach is considered whereby crystals are harvested using adhesives that capture naked crystals directly from their crystallization drop, reducing the process to a one-step procedure. The impact of using adhesives to ease the harvesting of different types of crystals is presented together with their contribution to background scattering and their usefulness in dehydration experiments. It is concluded that adhesive supports represent a valuable tool for mounting macromolecular crystals to be used in humidity-controlled experiments and to improve signal-to-noise ratios in diffraction experiments, and how they can protect crystals from modifications in the sample environment is discussed. PMID:25195752
Influence of moisture on the crystal forms of niclosamide obtained from acetone and ethyl acetate.

PubMed

Manek, Rahul V; Kolling, William M

2004-03-04

The purpose of this study was to elucidate the formation of crystal hydrates of niclosamide and to delineate the effect of relative humidity on the crystal forms obtained from acetone and ethyl acetate. Recrystallization of niclosamide was performed in the presence and absence of moisture. Two hydrates and their corresponding anhydrates were isolated. The hydrates obtained by the process of recrystallization from acetone (Form I) and that obtained from ethyl acetate (Form II) were classified based on differences in their dehydration profile, crystal structure, shape, and morphology. Crystals obtained in the absence of moisture were unstable, and when exposed to the laboratory atmosphere transformed to their corresponding hydrates. Differential scanning calorimetry thermograms indicate that Form I changes to an anhydrate at temperatures below 100 degrees C, while Form II dehydrates in a stepwise manner above 140 degrees C. This finding was further confirmed by thermogravimetric analysis. Dehydration of Form II was accompanied by a loss of structural integrity, demonstrating that water molecules play an important role in maintaining its crystal structure. Form I, Form II, and the anhydrate of Form II showed no significant moisture sorption over the entire range of relative humidity. Although the anhydrate of Form I did not show any moisture uptake at low humidity, it converted to the monohydrate at elevated relative humidity (>95%). All forms could be interconverted depending on the solvent and humidity conditions.
Grand canonical ensemble Monte Carlo simulation of the dCpG/proflavine crystal hydrate.

PubMed Central

Resat, H; Mezei, M

1996-01-01

The grand canonical ensemble Monte Carlo molecular simulation method is used to investigate hydration patterns in the crystal hydrate structure of the dCpG/proflavine intercalated complex. The objective of this study is to show by example that the recently advocated grand canonical ensemble simulation is a computationally efficient method for determining the positions of the hydrating water molecules in protein and nucleic acid structures. A detailed molecular simulation convergence analysis and an analogous comparison of the theoretical results with experiments clearly show that the grand ensemble simulations can be far more advantageous than the comparable canonical ensemble simulations. Images FIGURE 5 FIGURE 7 PMID:8873992
Formation of natural gas hydrates in marine sediments 1. Conceptual model of gas hydrate growth conditioned by host sediment properties

USGS Publications Warehouse

Clennell, M.B.; Hovland, M.; Booth, J.S.; Henry, P.; Winters, W.J.

1999-01-01

The stability of submarine gas hydrates is largely dictated by pressure and temperature, gas composition, and pore water salinity. However, the physical properties and surface chemistry of deep marine sediments may also affect the thermodynamic state, growth kinetics, spatial distributions, and growth forms of clathrates. Our conceptual model presumes that gas hydrate behaves in a way analogous to ice in a freezing soil. Hydrate growth is inhibited within fine-grained sediments by a combination of reduced pore water activity in the vicinity of hydrophilic mineral surfaces, and the excess internal energy of small crystals confined in pores. The excess energy can be thought of as a "capillary pressure" in the hydrate crystal, related to the pore size distribution and the state of stress in the sediment framework. The base of gas hydrate stability in a sequence of fine sediments is predicted by our model to occur at a lower temperature (nearer to the seabed) than would be calculated from bulk thermodynamic equilibrium. Capillary effects or a build up of salt in the system can expand the phase boundary between hydrate and free gas into a divariant field extending over a finite depth range dictated by total methane content and pore-size distribution. Hysteresis between the temperatures of crystallization and dissociation of the clathrate is also predicted. Growth forms commonly observed in hydrate samples recovered from marine sediments (nodules, and lenses in muds; cements in sands) can largely be explained by capillary effects, but kinetics of nucleation and growth are also important. The formation of concentrated gas hydrates in a partially closed system with respect to material transport, or where gas can flush through the system, may lead to water depletion in the host sediment. This "freeze-drying" may be detectable through physical changes to the sediment (low water content and overconsolidation) and/or chemical anomalies in the pore waters and metastable presence of free gas within the normal zone of hydrate stability.
Complex admixtures of clathrate hydrates in a water desalination method

DOEpatents

Simmons, Blake A [San Francisco, CA; Bradshaw, Robert W [Livermore, CA; Dedrick, Daniel E [Berkeley, CA; Anderson, David W [Riverbank, CA

2009-07-14

Disclosed is a method that achieves water desalination by utilizing and optimizing clathrate hydrate phenomena. Clathrate hydrates are crystalline compounds of gas and water that desalinate water by excluding salt molecules during crystallization. Contacting a hydrate forming gaseous species with water will spontaneously form hydrates at specific temperatures and pressures through the extraction of water molecules from the bulk phase followed by crystallite nucleation. Subsequent dissociation of pure hydrates yields fresh water and, if operated correctly, allows the hydrate-forming gas to be efficiently recycled into the process stream.
Crystal structures of hydrates of simple inorganic salts. III. Water-rich aluminium halide hydrates: AlCl3 · 15H2O, AlBr3 · 15H2O, AlI3 · 15H2O, AlI3 · 17H2O and AlBr3 · 9H2O.

PubMed

Schmidt, Horst; Hennings, Erik; Voigt, Wolfgang

2014-09-01

Water-rich aluminium halide hydrate structures are not known in the literature. The highest known water content per Al atom is nine for the perchlorate and fluoride. The nonahydrate of aluminium bromide, stable pentadecahydrates of aluminium chloride, bromide and iodide, and a metastable heptadecahydrate of the iodide have now been crystallized from low-temperature solutions. The structures of these hydrates were determined and are discussed in terms of the development of cation hydration spheres. The pentadecahydrate of the chloride and bromide are isostructural. In AlI(3) · 15H2O, half of the Al(3+) cations are surrounded by two complete hydration spheres, with six H2O in the primary and 12 in the secondary. For the heptadecahydrate of aluminium iodide, this hydration was found for every Al(3+).
X-ray investigation of molten crystal hydrates H2SO4(nH2O) and HNO3(nH2O)

NASA Technical Reports Server (NTRS)

Romanova, A. V.; Skryshevskiy, A. F.

1979-01-01

Integral analysis of the intensity of the electron density distribution curve in molten crystal hydrates provided by X-ray analysis, permits the following conclusions on the structure of the complex SO and NO ions, and the short-range order in the structure of the solution. The SO4 ion in the solution has a tetrahedral structure with an S to O distance equal to 1.5 A. For the NO3 in the solution, a planar triangular shape is probable, with an N to O distance equal to 1.2 A. Preferential distances between each of the oxygens of the SO ion and the nearest molecules of water proved near to the corresponding distances in solid crystal hydrates. For an (H2SO4)(H2O) solution, the average number of water molecules surrounding each oxygen atom of the SO4 (--) ion was on the order of 1.3 molecules. Hence the preferential distances between the water molecules and the oxygen atoms of the SO ion, and the preference of their mutual position, correspond to the fixed position of these same elements of the structure in the solid crystal hydrate.
Growth Kinetics and Mechanics of Hydrate Films by Interfacial Rheology.

PubMed

Leopércio, Bruna C; de Souza Mendes, Paulo R; Fuller, Gerald G

2016-05-03

A new approach to study and understand the kinetics and mechanical properties of hydrates by interfacial rheology is presented. This is made possible using a "double wall ring" interfacial rheology cell that has been designed to provide the necessary temperature control. Cyclopentane and water are used to form hydrates, and this model system forms these structures at ambient pressures. Different temperature and water/hydrocarbon contact protocols are explored. Of particular interest is the importance of first contacting the hydrocarbon against ice crystals in order to initiate hydrate formation. Indeed, this is found to be the case, even though the hydrates may be created at temperatures above the melting point of ice. Once hydrates completely populate the hydrocarbon/water interface, strain sweeps of the interfacial elastic and viscous moduli are conducted to interrogate the mechanical response and fragility of the hydrate films. The dependence on temperature, Tf, by the kinetics of formation and the mechanical properties is reported, and the cyclopentane hydrate dissociation temperature was found to be between 6 and 7 °C. The formation time (measured from the moment when cyclopentane first contacts ice crystals) as well as the elastic modulus and the yield strain increase as Tf increases.
Origins of hydration differences in homochiral and racemic crystals of aspartic acid.

PubMed

Juliano, Thomas R; Korter, Timothy M

2015-02-26

The propensity for crystalline hydrates of organic molecules to form is related to the strength of the interactions between molecules, including the chiral composition of the molecular solids. Specifically, homochiral versus racemic crystalline samples can exhibit distinct differences in their ability to form energetically stable hydrates. The focus of the current study is a comparison of the crystal structures and intermolecular forces found in solid-state L-aspartic acid, DL-aspartic acid, and L-aspartic acid monohydrate. The absence of experimental evidence for the DL-aspartic acid monohydrate is considered here in terms of the enhanced thermodynamic stability of the DL-aspartic acid anhydrate crystal as compared to the L-aspartic acid anhydrate as revealed through solid-state density functional theory calculations and terahertz spectroscopic measurements. The results indicate that anhydrous DL-aspartic acid is the more stable solid, not due to intermolecular forces alone but also due to the improved conformations of the molecules within the racemic solid. Hemihydrated and monohydrated forms of DL-aspartic acid have been computationally evaluated, and in each case, the hydrates produce destabilized aspartic acid conformations that prevent DL-aspartic acid hydrate formation from occurring.
Loss of halogens from crystallized and glassy silicic volcanic rocks

USGS Publications Warehouse

Noble, D.C.; Smith, V.C.; Peck, L.C.

1967-01-01

One hundred and sixty-four F and Cl analyses of silicic welded tuffs and lavas and glass separates are presented. Comparison of the F and Cl contents of crystallized rocks with those of nonhydrated glass and hydrated glassy rocks from the same rock units shows that most of the halogens originally present were lost on crystallization. An average of about half of the F and four-fifths of the Cl originally present was lost. Analyses of hydrated natural glasses and of glassy rocks indicate that in some cases significant amounts of halogens may be removed from or added to hydrated glass through prolonged contact with ground water. The data show that the original halogen contents of the groundmass of a silicic volcanic rock can be reliably determined only from nonhydrated glass. ?? 1967.
Methanol incorporation in clathrate hydrates and the implications for oil and gas pipeline flow assurance and icy planetary bodies

PubMed Central

Shin, Kyuchul; Udachin, Konstantin A.; Moudrakovski, Igor L.; Leek, Donald M.; Alavi, Saman; Ratcliffe, Christopher I.; Ripmeester, John A.

2013-01-01

One of the best-known uses of methanol is as antifreeze. Methanol is used in large quantities in industrial applications to prevent methane clathrate hydrate blockages from forming in oil and gas pipelines. Methanol is also assigned a major role as antifreeze in giving icy planetary bodies (e.g., Titan) a liquid subsurface ocean and/or an atmosphere containing significant quantities of methane. In this work, we reveal a previously unverified role for methanol as a guest in clathrate hydrate cages. X-ray diffraction (XRD) and NMR experiments showed that at temperatures near 273 K, methanol is incorporated in the hydrate lattice along with other guest molecules. The amount of included methanol depends on the preparative method used. For instance, single-crystal XRD shows that at low temperatures, the methanol molecules are hydrogen-bonded in 4.4% of the small cages of tetrahydrofuran cubic structure II hydrate. At higher temperatures, NMR spectroscopy reveals a number of methanol species incorporated in hydrocarbon hydrate lattices. At temperatures characteristic of icy planetary bodies, vapor deposits of methanol, water, and methane or xenon show that the presence of methanol accelerates hydrate formation on annealing and that there is unusually complex phase behavior as revealed by powder XRD and NMR spectroscopy. The presence of cubic structure I hydrate was confirmed and a unique hydrate phase was postulated to account for the data. Molecular dynamics calculations confirmed the possibility of methanol incorporation into the hydrate lattice and show that methanol can favorably replace a number of methane guests. PMID:23661058
Methanol incorporation in clathrate hydrates and the implications for oil and gas pipeline flow assurance and icy planetary bodies.

PubMed

Shin, Kyuchul; Udachin, Konstantin A; Moudrakovski, Igor L; Leek, Donald M; Alavi, Saman; Ratcliffe, Christopher I; Ripmeester, John A

2013-05-21

One of the best-known uses of methanol is as antifreeze. Methanol is used in large quantities in industrial applications to prevent methane clathrate hydrate blockages from forming in oil and gas pipelines. Methanol is also assigned a major role as antifreeze in giving icy planetary bodies (e.g., Titan) a liquid subsurface ocean and/or an atmosphere containing significant quantities of methane. In this work, we reveal a previously unverified role for methanol as a guest in clathrate hydrate cages. X-ray diffraction (XRD) and NMR experiments showed that at temperatures near 273 K, methanol is incorporated in the hydrate lattice along with other guest molecules. The amount of included methanol depends on the preparative method used. For instance, single-crystal XRD shows that at low temperatures, the methanol molecules are hydrogen-bonded in 4.4% of the small cages of tetrahydrofuran cubic structure II hydrate. At higher temperatures, NMR spectroscopy reveals a number of methanol species incorporated in hydrocarbon hydrate lattices. At temperatures characteristic of icy planetary bodies, vapor deposits of methanol, water, and methane or xenon show that the presence of methanol accelerates hydrate formation on annealing and that there is unusually complex phase behavior as revealed by powder XRD and NMR spectroscopy. The presence of cubic structure I hydrate was confirmed and a unique hydrate phase was postulated to account for the data. Molecular dynamics calculations confirmed the possibility of methanol incorporation into the hydrate lattice and show that methanol can favorably replace a number of methane guests.
Structural Basis for the Inhibition of Gas Hydrates by α-Helical Antifreeze Proteins

PubMed Central

Sun, Tianjun; Davies, Peter L.; Walker, Virginia K.

2015-01-01

Kinetic hydrate inhibitors (KHIs) are used commercially to inhibit gas hydrate formation and growth in pipelines. However, improvement of these polymers has been constrained by the lack of verified molecular models. Since antifreeze proteins (AFPs) act as KHIs, we have used their solved x-ray crystallographic structures in molecular modeling to explore gas hydrate inhibition. The internal clathrate water network of the fish AFP Maxi, which extends to the protein’s outer surface, is remarkably similar to the {100} planes of structure type II (sII) gas hydrate. The crystal structure of this water web has facilitated the construction of in silico models for Maxi and type I AFP binding to sII hydrates. Here, we have substantiated our models with experimental evidence of Maxi binding to the tetrahydrofuran sII model hydrate. Both in silico and experimental evidence support the absorbance-inhibition mechanism proposed for KHI binding to gas hydrates. Based on the Maxi crystal structure we suggest that the inhibitor adsorbs to the gas hydrate lattice through the same anchored clathrate water mechanism used to bind ice. These results will facilitate the rational design of a next generation of effective green KHIs for the petroleum industry to ensure safe and efficient hydrocarbon flow. PMID:26488661
An evaluation of adhesive sample holders for advanced crystallographic experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mazzorana, Marco; Sanchez-Weatherby, Juan, E-mail: juan.sanchez-weatherby@diamond.ac.uk; Sandy, James

Commercially available adhesives have been evaluated for crystal mounting when undertaking complex macromolecular crystallography experiments. Here, their use as tools for advanced sample mounting and cryoprotection is assessed and their suitability for room-temperature data-collection and humidity-controlled studies is investigated. The hydration state of macromolecular crystals often affects their overall order and, ultimately, the quality of the X-ray diffraction pattern that they produce. Post-crystallization techniques that alter the solvent content of a crystal may induce rearrangement within the three-dimensional array making up the crystal, possibly resulting in more ordered packing. The hydration state of a crystal can be manipulated by exposingmore » it to a stream of air at controlled relative humidity in which the crystal can equilibrate. This approach provides a way of exploring crystal hydration space to assess the diffraction capabilities of existing crystals. A key requirement of these experiments is to expose the crystal directly to the dehydrating environment by having the minimum amount of residual mother liquor around it. This is usually achieved by placing the crystal on a flat porous support (Kapton mesh) and removing excess liquid by wicking. Here, an alternative approach is considered whereby crystals are harvested using adhesives that capture naked crystals directly from their crystallization drop, reducing the process to a one-step procedure. The impact of using adhesives to ease the harvesting of different types of crystals is presented together with their contribution to background scattering and their usefulness in dehydration experiments. It is concluded that adhesive supports represent a valuable tool for mounting macromolecular crystals to be used in humidity-controlled experiments and to improve signal-to-noise ratios in diffraction experiments, and how they can protect crystals from modifications in the sample environment is discussed.« less

High Pressure Response of Siliceous Materials

DTIC Science & Technology

2013-02-01

iron-containing soda lime silicate glass, opal (a hydrated silicate glass), ROBAX glass ceramic, and others were single crystal (α-quartz) and...10 2.6. Opal (hydrated amorphous silica...Raman spectrum as a function of stress for opal (hydrated silica) glass. ................... 29 4.9. Raman spectrum as a function of stress for
Crystal chemistry and structure refinement of five hydrated calcium borates

USGS Publications Warehouse

Clark, J.R.; Appleman, D.E.; Christ, C.L.

1964-01-01

The crystal structures of the five known members of the series Ca2B6O11??xH2O (x = 1, 5, 5, 7, 9, and 13) have been refined by full-matrix least-squares techniques, yielding bond distances and angles with standard errors of less than 0??01 A?? and 0??5??, respectively. The results illustrate the crystal chemical principles that govern the structures of hydrated borate compounds. The importance of hydrogen bonding in the ferroelectric transition of colemanite is confirmed by more accurate proton assignments. ?? 1964.
Supramolecular Organization of Nonstoichiometric Drug Hydrates: Dapsone

NASA Astrophysics Data System (ADS)

Braun, Doris E.; Griesser, Ulrich J.

2018-02-01

The observed moisture- and temperature dependent transformations of the dapsone (4,4'-diaminodiphenyl sulfone, DDS) 0.33-hydrate were correlated to its structure and the number and strength of the water-DDS intermolecular interactions. A combination of characterization techniques was used, including thermal analysis (hot-stage microscopy, differential scanning calorimetry and thermogravimetric analysis), gravimetric moisture sorption/desorption studies and variable humidity powder X-ray diffraction, along with computational modeling (crystal structure prediction and pair-wise intermolecular energy calculations). Depending on the relative humidity the hydrate contains between 0 and 0.33 molecules of water per molecule DDS. The crystal structure is retained upon dehydration indicating that DDS hydrate shows a non-stoichiometric (de)hydration behavior. Unexpectedly, the water molecules are not located in structural channels but at isolated-sites of the host framework, which is counterintuitively for a hydrate with non-stoichiometric behavior. The water-DDS interactions were estimated to be weaker than water-host interactions that are commonly observed in stoichiometric hydrates and the lattice energies of the isomorphic dehydration product (hydrate structure without water molecules) and a stable anhydrate at room temperature (form III) differ only by approximately 1 kJ mol–1. The computational generation of hypothetical monohydrates confirms that the hydrate with the unusual DDS:water ratio of 3:1 is more stable than a feasible monohydrate structure. Overall, this study addresses the critical class of non-stoichiometric hydrates, highlighting that only a multidisciplinary investigation can unravel hydrate formation at a molecular level, knowledge which is a requirement in modern drug development.
Crystallization Caught in the Act with Terahertz Spectroscopy: Non-Classical Pathway for l-(+)-Tartaric Acid.

PubMed

Soltani, Amin; Gebauer, Denis; Duschek, Lennart; Fischer, Bernd M; Cölfen, Helmut; Koch, Martin

2017-10-12

Crystal formation is a highly debated problem. This report shows that the crystallization of l-(+)-tartaric acid from water follows a non-classical path involving intermediate hydrated states. Analytical ultracentrifugation indicates solution clusters of the initial stages aggregate to form an early intermediate. Terahertz spectroscopy performed during water evaporation highlights a transient increase in the absorption during nucleation; this indicates the recurrence of water molecules that are expelled from the intermediate phase. Besides, a transient resonance at 750 GHz, which can be assigned to a natural vibration of large hydrated aggregates, vanishes after the final crystal has formed. Furthermore, THz data reveal the vibration of nanosized clusters in the dilute solution indicated by analytical ultracentrifugation. Infrared spectroscopy and wide-angle X-ray scattering highlight that the intermediate is not a crystalline hydrate. These results demonstrate that nanoscopic intermediate units assemble to form the first solvent-free crystalline nuclei upon dehydration. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Potential Applications of Alkali-Activated Alumino-Silicate Binders in Military Operations

DTIC Science & Technology

1985-11-01

Geopolymers for Reinforced Plastics/ Composits ," PACTEC 󈨓, Society of Plastic Engineers, Costa Mesa, CA, 1979, pp. 151-153. Davidovits, Joseph. 1983...34 Geopolymers II, Processing and Applications of Ultra-High Temperature, Inorganic Matrix Resin for Cast Composite Structures, Molds and Tools for RP/C and...alumino-silicate hydrates with an approximate composition of 3CaO - AI20 3 • 2i0 2 2120, begin to crystallize. As the gels begin to coalesce, bound water
Hydration of nucleic acid fragments: comparison of theory and experiment for high-resolution crystal structures of RNA, DNA, and DNA-drug complexes.

PubMed Central

Hummer, G; García, A E; Soumpasis, D M

1995-01-01

A computationally efficient method to describe the organization of water around solvated biomolecules is presented. It is based on a statistical mechanical expression for the water-density distribution in terms of particle correlation functions. The method is applied to analyze the hydration of small nucleic acid molecules in the crystal environment, for which high-resolution x-ray crystal structures have been reported. Results for RNA [r(ApU).r(ApU)] and DNA [d(CpG).d(CpG) in Z form and with parallel strand orientation] and for DNA-drug complexes [d(CpG).d(CpG) with the drug proflavine intercalated] are described. A detailed comparison of theoretical and experimental data shows positional agreement for the experimentally observed water sites. The presented method can be used for refinement of the water structure in x-ray crystallography, hydration analysis of nuclear magnetic resonance structures, and theoretical modeling of biological macromolecules such as molecular docking studies. The speed of the computations allows hydration analyses of molecules of almost arbitrary size (tRNA, protein-nucleic acid complexes, etc.) in the crystal environment and in aqueous solution. Images FIGURE 1 FIGURE 2 FIGURE 5 FIGURE 6 FIGURE 9 FIGURE 12 FIGURE 13 PMID:7542034
Dynamics of Uncrystallized Water, Ice, and Hydrated Protein in Partially Crystallized Gelatin-Water Mixtures Studied by Broadband Dielectric Spectroscopy.

PubMed

Sasaki, Kaito; Panagopoulou, Anna; Kita, Rio; Shinyashiki, Naoki; Yagihara, Shin; Kyritsis, Apostolos; Pissis, Polycarpos

2017-01-12

The glass transition of partially crystallized gelatin-water mixtures was investigated using broadband dielectric spectroscopy (BDS) over a wide range of frequencies (10 mHz to 10 MHz), temperatures (113-298 K), and concentrations (10-45 wt %). Three dielectric relaxation processes (processes I, II, and III) were clearly observed. Processes I, II, and III originate from uncrystallized water (UCW) in the hydration shells of gelatin, ice, and hydrated gelatin, respectively. A dynamic crossover, called the Arrhenius to non-Arrhenius transition of UCW, was observed at the glass transition temperature of the relaxation process of hydrated gelatin for all mixtures. The amount of UCW increases with increasing gelatin content. However, above 35 wt % gelatin, the amount of UCW became more dependent on the gelatin concentration. This increase in UCW causes a decrease in the glass transition temperature of the cooperative motion of gelatin and UCW, which appears to result from a change in the aggregation structure of gelatin in the mixture at a gelatin concentration of approximately 35 wt %. The temperature dependence of the relaxation time of process II has nearly the same activation energy as pure ice made by slow crystallization of ice Ih. This implies that process II originates from the dynamics of slowly crystallized ice Ih.
Influence of polymeric excipient properties on crystal hydrate formation kinetics of caffeine in aqueous slurries.

PubMed

Gift, Alan D; Southard, Leslie A; Riesberg, Amanda L

2012-05-01

The influence of polymeric excipients on the hydrate transformation of caffeine (CAF) was studied. Anhydrous CAF was added to aqueous solutions containing different additives and the transformation to the hydrate form was monitored using in-line Raman spectroscopy. Various properties of two known inhibitors of CAF hydrate formation, polyacrylic acid (PAA) and polyvinyl alcohol (PVA), were investigated. For inhibition by PAA, a pH dependence was observed: at low pH, the inhibition was greatest, whereas no inhibitory effects were observed at pH above 6.5. For PVA, grades with high percent hydrolysis were the most effective at inhibiting the transformation. In addition, PVA with higher molecular weight showed slightly more inhibition than the shorter chain PVA polymers. A variety of other hydroxyl containing compounds were examined but none inhibited the CAF anhydrate-to-hydrate transformation. The observed inhibitory effects of PAA and PVA are attributed to the large number of closely spaced hydrogen bond donating groups of the polymer molecule, which can interact with the CAF hydrate crystal. Copyright © 2012 Wiley Periodicals, Inc.
Estimating the Aqueous Solubility of Pharmaceutical Hydrates

PubMed Central

Franklin, Stephen J.; Younis, Usir S.; Myrdal, Paul B.

2016-01-01

Estimation of crystalline solute solubility is well documented throughout the literature. However, the anhydrous crystal form is typically considered with these models, which is not always the most stable crystal form in water. In this study an equation which predicts the aqueous solubility of a hydrate is presented. This research attempts to extend the utility of the ideal solubility equation by incorporating desolvation energetics of the hydrated crystal. Similar to the ideal solubility equation, which accounts for the energetics of melting, this model approximates the energy of dehydration to the entropy of vaporization for water. Aqueous solubilities, dehydration and melting temperatures, and log P values were collected experimentally and from the literature. The data set includes different hydrate types and a range of log P values. Three models are evaluated, the most accurate model approximates the entropy of dehydration (ΔSd) by the entropy of vaporization (ΔSvap) for water, and utilizes onset dehydration and melting temperatures in combination with log P. With this model, the average absolute error for the prediction of solubility of 14 compounds was 0.32 log units. PMID:27238488
Single crystal neutron diffraction of hydrous wadsleyite and the reason of sensitivity difference for hydration between upper and lower mantle transition zones

NASA Astrophysics Data System (ADS)

Purevjav, N.; Okuchi, T.; Tomioka, N.; Wang, X.; Hoffmann, C.

2016-12-01

Evidences from seismological and mineralogical studies increasingly indicates that water has been transported from the oceans into the Earth's deep mantle, where the mantle transition zone is believed to be the largest reservoir of this transported water. Wadsleyite and ringwoodite are the major constituents and the most important host minerals absorbing this type of water in the transition zone. These minerals are capable of storing the entire mass of the oceans as a hidden reservoirs. In order to understand the effects of such water on the physical properties and chemical evolution of the Earth's interior, it is essential to determine where in the crystal structure the hydration occurs, and which chemical bonds are altered and weakened after hydration. Here we show the result of a neutron single-crystal Laue diffraction study of hydrous wadsleyite. A crystal of homogenously-hydrated wadsleyite involving 1.4 wt. % of H2O was synthesized by our recently-established slow cooling method, which was an effective way to grow high quality large single crystals [1]. By analyzing this crystal using pulsed neutron beam, we demonstrated that the hydrogen atoms exchange only with Mg2+ at the one of the specific octahedron sites (M3) in wadsleyite. We also determined hydrogen's bonding distances and bonding angle. The results unambiguously demonstrated the unique mechanism of hydrogen incorporation into the wadsleyite crystal structure. We previously found that the hydrogen atoms exchanged with both Mg2+ and Si4+ sites simultaneously in the crystal structure of hydrous ringwoodite [2]. Therefore, the current results show that hydration mechanisms are qualitatively different between the upper and the lower transition zones in the wet mantle. The difference is a vital clue towards understanding why these mantle transition zone minerals show different sensitivity for water in their softening behaviors. In addition, we demonstrated that maximum water concentration in wadsleyite is strictly constrained by its full capacity into M3 site. Also, by this study we demonstrated that single-crystal neutron diffraction is a useful tool for quantitative analysis of H2O concentrations in nominally anhydrous minerals. [1] Okuchi et al., Amer. Miner., 2015; [2] Purevjav et al., Geophys. Res. Lett., 2014.
Gas hydrates (clathrates) causing pore-water freshening and oxygen isotope fractionation in deep-water sedimentary sections of terrigenous continental margins

USGS Publications Warehouse

Hesse, R.; Harrison, W.E.

1981-01-01

The occurrence of gas hydrates in deep-water sections of the continental margins predicted from anomalous acoustic reflectors on seismic profiles has been confirmed by recent deep-sea drilling results. On the Pacific continental slope off Guatemala gas hydrates were brought up for the first time from two holes (497, 498A) drilled during Leg 67 of the DSDP in water depths of 2360 and 5500 m, respectively. The hydrates occur in organic matter-rich Pleistocene to Miocene terrigenous sediments. In the hydrate-bearing zone a marked decrease in interstitial water chlorinities was observed starting at about 10-20 m subbottom depth. Pore waters at the bottom of the holes (near 400 m subbottom) have as little as half the chlorinity of seawater (i.e. 9???). Similar, but less pronounced, trends were observed during previous legs of the DSDP in other hydrate-prone segments of the continental margins where recharge of fresh water from the continent can be excluded (e.g. Leg 11). The crystallization of hydrates, like ice, excludes salt ions from the crystal structure. During burial the dissolved salts are separated from the solids. Subsidence results in a downward motion of the solids (including hydrates) relative to the pore fluids. Thawing of hydrates during recovery releases fresh water which is remixed with the pore fluid not involved in hydrate formation. The volume of the latter decreases downhole thus causing downward decreasing salinity (chlorinity). Hydrate formation is responsible for oxygen isotope fractionation with 18O-enrichment in the hydrate explaining increasingly more positive ??18O values in the pore fluids recovered (after hydrate dissociation) with depth. ?? 1981.
Selective Encaging of N2O in N2O-N2 Binary Gas Hydrates via Hydrate-Based Gas Separation.

PubMed

Yang, Youjeong; Shin, Donghoon; Choi, Seunghyun; Woo, Yesol; Lee, Jong-Won; Kim, Dongseon; Shin, Hee-Young; Cha, Minjun; Yoon, Ji-Ho

2017-03-21

The crystal structure and guest inclusion behaviors of nitrous oxide-nitrogen (N 2 O-N 2 ) binary gas hydrates formed from N 2 O/N 2 gas mixtures are determined through spectroscopic analysis. Powder X-ray diffraction results indicate that the crystal structure of all the N 2 O-N 2 binary gas hydrates is identified as the structure I (sI) hydrate. Raman spectra for the N 2 O-N 2 binary gas hydrate formed from N 2 O/N 2 (80/20, 60/40, 40/60 mol %) gas mixtures reveal that N 2 O molecules occupy both large and small cages of the sI hydrate. In contrast, there is a single Raman band of N 2 O molecules for the N 2 O-N 2 binary gas hydrate formed from the N 2 O/N 2 (20/80 mol %) gas mixture, indicating that N 2 O molecules are trapped in only large cages of the sI hydrate. From temperature-dependent Raman spectra and the Predictive Soave-Redlich-Kwong (PSRK) model calculation, we confirm the self-preservation of N 2 O-N 2 binary gas hydrates in the temperature range of 210-270 K. Both the experimental measurements and the PSRK model calculations demonstrate the preferential occupation of N 2 O molecules rather than N 2 molecules in the hydrate cages, leading to a possible process for separating N 2 O from gas mixtures via hydrate formation. The phase equilibrium conditions, pseudo-pressure-composition (P-x) diagram, and gas storage capacity of N 2 O-N 2 binary gas hydrates are discussed in detail.
Supramolecular Organization of Nonstoichiometric Drug Hydrates: Dapsone.

PubMed

Braun, Doris E; Griesser, Ulrich J

2018-01-01

The observed moisture- and temperature dependent transformations of the dapsone (4,4'-diaminodiphenyl sulfone, DDS) 0. 33-hydrate were correlated to its structure and the number and strength of the water-DDS intermolecular interactions. A combination of characterization techniques was used, including thermal analysis (hot-stage microscopy, differential scanning calorimetry and thermogravimetric analysis), gravimetric moisture sorption/desorption studies and variable humidity powder X-ray diffraction, along with computational modeling (crystal structure prediction and pair-wise intermolecular energy calculations). Depending on the relative humidity the hydrate contains between 0 and 0.33 molecules of water per molecule DDS. The crystal structure is retained upon dehydration indicating that DDS hydrate shows a non-stoichiometric (de)hydration behavior. Unexpectedly, the water molecules are not located in structural channels but at isolated-sites of the host framework, which is counterintuitively for a hydrate with non-stoichiometric behavior. The water-DDS interactions were estimated to be weaker than water-host interactions that are commonly observed in stoichiometric hydrates and the lattice energies of the isomorphic dehydration product (hydrate structure without water molecules) and (form III ) differ only by ~1 kJ mol -1 . The computational generation of hypothetical monohydrates confirms that the hydrate with the unusual DDS:water ratio of 3:1 is more stable than a feasible monohydrate structure. Overall, this study highlights that a deeper understanding of the formation of hydrates with non-stoichiometric behavior requires a multidisciplinary approach including suitable experimental and computational methods providing a firm basis for the development and manufacturing of high quality drug products.
Observation of interstitial molecular hydrogen in clathrate hydrates.

PubMed

Grim, R Gary; Barnes, Brian C; Lafond, Patrick G; Kockelmann, Winfred A; Keen, David A; Soper, Alan K; Hiratsuka, Masaki; Yasuoka, Kenji; Koh, Carolyn A; Sum, Amadeu K

2014-09-26

The current knowledge and description of guest molecules within clathrate hydrates only accounts for occupancy within regular polyhedral water cages. Experimental measurements and simulations, examining the tert-butylamine + H2 + H2O hydrate system, now suggest that H2 can also be incorporated within hydrate crystal structures by occupying interstitial sites, that is, locations other than the interior of regular polyhedral water cages. Specifically, H2 is found within the shared heptagonal faces of the large (4(3)5(9)6(2)7(3)) cage and in cavities formed from the disruption of smaller (4(4)5(4)) water cages. The ability of H2 to occupy these interstitial sites and fluctuate position in the crystal lattice demonstrates the dynamic behavior of H2 in solids and reveals new insight into guest-guest and guest-host interactions in clathrate hydrates, with potential implications in increasing overall energy storage properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Theoretical and Experimental Approaches towards study of Methane Occupation Dynamics within Gas Hydrates

NASA Astrophysics Data System (ADS)

Mendonca, P.; Shemella, P.; Nayak, S.; Sharma, A.

2006-12-01

Hydrate structures of hydrocarbon (commonly methane hydrates) within the continental shelf regions are considered a huge energy resource since they are a significant reservoir for terrestrial carbon. Any changes, abrupt or continual, will have an impact on the carbon (as well as water) cycle. However, tapping into this reservoir for energy resource has been challenging from both technical and scientific fronts primarily because any rapid release of methane (CH4) will likely have serious impact on the global climate of Earth as well as the stability of the continental shelf. While fossil fuel combustion derived CO2 in the atmosphere is considered a major contributor to global warming, the massive amounts of methane release from the gas hydrates has been a point of debate for its impact on the global climate. Due to the lack of a clear physical mechanism for such structural destabilization, environmental changes within the ocean setting (viz. temperature, salinity or biology) are typically assigned as possible causes. A good kinetic model that ties into structural instability of these essentially non-stoichiometric compounds at both the macromolecular (thermodynamic) and nanometric scale is essential. Preliminary experiments on single crystal methane hydrate high pressure phase (~1.0GPa) indicate a measurable kinetics of methane diffusion upon bringing structural disorder to the single crystal. Although there have been several kinetic studies of gas-hydrate nucleation and dissociation, systematic study of kinetics (and dynamics) of diffusion based changes within the gas hydrates has been lacking. In addition to experimental data on single crystal methane hydrates, we will present a first principle study on the structure, energetic, and dynamics of sI phase methane hydrate. We use density functional theory to study the energetic effect of the occupancy of neighboring cages in a cluster model system consisting of two sI gas hydrates. In this situation there can be two, one, or no methane, and we find that the binding for the first methane is exothermic. The second methane binding is endothermic, suggesting that the stability of a methane molecule is determined by the occupancy of adjacent cages. Using these results, we will present the calculated binding energies of a periodic system based on crystal structure data and compare them to the cluster method. This combined experimental and theoretical investigation is aimed at generating fundamental dataset that can be tested for the broader impact of such processes on the global carbon cycle.
Free energy landscape and molecular pathways of gas hydrate nucleation.

PubMed

Bi, Yuanfei; Porras, Anna; Li, Tianshu

2016-12-07

Despite the significance of gas hydrates in diverse areas, a quantitative knowledge of hydrate formation at a molecular level is missing. The impediment to acquiring this understanding is primarily attributed to the stochastic nature and ultra-fine scales of nucleation events, posing a great challenge for both experiment and simulation to explore hydrate nucleation. Here we employ advanced molecular simulation methods, including forward flux sampling (FFS), p B histogram analysis, and backward flux sampling, to overcome the limit of direct molecular simulation for exploring both the free energy landscape and molecular pathways of hydrate nucleation. First we test the half-cage order parameter (H-COP) which we developed for driving FFS, through conducting the p B histogram analysis. Our results indeed show that H-COP describes well the reaction coordinates of hydrate nucleation. Through the verified order parameter, we then directly compute the free energy landscape for hydrate nucleation by combining both forward and backward flux sampling. The calculated stationary distribution density, which is obtained independently of nucleation theory, is found to fit well against the classical nucleation theory (CNT). Subsequent analysis of the obtained large ensemble of hydrate nucleation trajectories show that although on average, hydrate formation is facilitated by a two-step like mechanism involving a gradual transition from an amorphous to a crystalline structure, there also exist nucleation pathways where hydrate crystallizes directly, without going through the amorphous stage. The CNT-like free energy profile and the structural diversity suggest the existence of multiple active transition pathways for hydrate nucleation, and possibly also imply the near degeneracy in their free energy profiles among different pathways. Our results thus bring a new perspective to the long standing question of how hydrates crystallize.
Free energy landscape and molecular pathways of gas hydrate nucleation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bi, Yuanfei; Porras, Anna; Li, Tianshu, E-mail: tsli@gwu.edu

Despite the significance of gas hydrates in diverse areas, a quantitative knowledge of hydrate formation at a molecular level is missing. The impediment to acquiring this understanding is primarily attributed to the stochastic nature and ultra-fine scales of nucleation events, posing a great challenge for both experiment and simulation to explore hydrate nucleation. Here we employ advanced molecular simulation methods, including forward flux sampling (FFS), p{sub B} histogram analysis, and backward flux sampling, to overcome the limit of direct molecular simulation for exploring both the free energy landscape and molecular pathways of hydrate nucleation. First we test the half-cage ordermore » parameter (H-COP) which we developed for driving FFS, through conducting the p{sub B} histogram analysis. Our results indeed show that H-COP describes well the reaction coordinates of hydrate nucleation. Through the verified order parameter, we then directly compute the free energy landscape for hydrate nucleation by combining both forward and backward flux sampling. The calculated stationary distribution density, which is obtained independently of nucleation theory, is found to fit well against the classical nucleation theory (CNT). Subsequent analysis of the obtained large ensemble of hydrate nucleation trajectories show that although on average, hydrate formation is facilitated by a two-step like mechanism involving a gradual transition from an amorphous to a crystalline structure, there also exist nucleation pathways where hydrate crystallizes directly, without going through the amorphous stage. The CNT-like free energy profile and the structural diversity suggest the existence of multiple active transition pathways for hydrate nucleation, and possibly also imply the near degeneracy in their free energy profiles among different pathways. Our results thus bring a new perspective to the long standing question of how hydrates crystallize.« less
Recovering and recycling uranium used for production of molybdenum-99

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reilly, Sean Douglas; May, Iain; Copping, Roy

A processes for recycling uranium that has been used for the production of molybdenum-99 involves irradiating a solution of uranium suitable for forming fission products including molybdenum-99, conditioning the irradiated solution to one suitable for inducing the formation of crystals of uranyl nitrate hydrates, then forming the crystals and a supernatant and then separating the crystals from the supernatant, thus using the crystals as a source of uranium for recycle. Molybdenum-99 is recovered from the supernatant using an adsorbent such as alumina. Another process involves irradiation of a solid target comprising uranium, forming an acidic solution from the irradiated targetmore » suitable for inducing the formation of crystals of uranyl nitrate hydrates, then forming the crystals and a supernatant and then separating the crystals from the supernatant, thus using the crystals as a source of uranium for recycle. Molybdenum-99 is recovered from the supernatant using an adsorbent such as alumina.« less
Inter-subunit electrostatic interactions in ferritin molecule: comparison with inter-molecular interactions in crystals

NASA Astrophysics Data System (ADS)

Takahashi, Takuya; Hogyoku, Michiru; Nagayama, Kuniaki

1996-10-01

We evaluated the contribution of electrostatic interactions to the stability of macromolecular assembly in a horse L ferritin molecule composed of 24 subunits and the three-dimensional crystal of the ferritin molecules with numerical calculation of Poisson-Boltzmann equation based on dielectric model. The calculation showed that the electrostatic energy both favors the assembly of the 24 subunits and the crystalline assembly of the ferritin molecules (i.e., 24-mers). Short-range interactions less than 5 Å such as salt bridges and hydrogen bonds were important for both the subunit assembly and the crystalline assembly. To elucidate the strong stabilization by electrostatic interactions in both the ferritin 24-mer and its crystal, we analyzed the contribution of individual atoms. It revealed that the stabilization was arising from buried salt bridges or hydrogen bonds, which yielded more than 5 kcal/mol in some interactions. These large electrostatic stabilization and also the unexpected small ionic strength dependence was different from those of bovine pancreatic trypsin inhibitor (BPTI) orthorhombic and pig-insulin cubic crystals previously calculated. We also evaluated changes of the accessible surface area (ASA) and hydration free energy in accordance with the process of the subunit assembly. The change of hydration free energy, which was very large (i.e. ˜ + 100 kcal/mol/subunit) and unfavorable for the assembly, was proportional to the electrostatic hydration energy (i.e. Born energy change in hydration process). Hydrophobic groups were likely to appear more frequently than hydrophilic groups at the subunit interfaces. These results suggest that the molecular structure of the ferritin 24-mer and the crystal structure of the 24-mers were both stabilized by local electrostatic interactions, in particular. We view protein crystals as an extension of the protein oligomer to an infinite number of subunits association.
An ikaite record of late Holocene climate at the Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Lu, Z.; Rickaby, R. E.; Kennedy, H.; Pancost, R. D.; Shaw, S.; Lennie, A. R.; Wellner, J. S.; Anderson, J. B.

2011-12-01

Ikaite is a low temperature polymorph of calcium carbonate which is hydrated with water molecules contained in its crystal lattice (CaCO3:6H2O). Ikaite is thought to rapidly decompose into calcite and water at temperatures above 4°C. The hydration water in ikaite grown in laboratory experiments records the δ18O of ambient water, a feature potentially useful for reconstructing δ18O of local seawater. The most recent melting of the Caley Glacier on the Antarctic Peninsula (AP) during last few decades released meltwater into nearby fjords and left a strong signal of light δ18O values in shallow porewater profiles. If ikaite crystals incorporate ambient porewaters into crystal structure as the hydration water, then crystals grown at different times will record the changes in bottom water δ18O due to waxing and waning of (global or local) ice-sheets. U.S. Antarctic Program cruise NBP0703 collected piston cores around the AP and found ikaite crystals in multiple horizons at the Firth of Tay, suitable for reconstructing a low resolution ikaite record of the last 2000 years. We report the first downcore δ18O record of natural ikaite hydration waters and crystals collected from the AP, a region sensitive to climate fluctuations. We are able to establish the zone of ikaite formation within shallow sediments and derive a climatic signal, related to local changes in fjord δ18O, versus time encoded in this late Holocene ikaite record. Our interpretation, based on ikaite isotopes, provides additional qualitative evidence that both the Medieval Warm Period and Little Ice Age were extended to the Southern Ocean and the Antarctic Peninsula.

Liquid Crystal Formation from Sunflower Oil: Long Term Stability Studies.

PubMed

da Rocha-Filho, Pedro Alves; Maruno, Mônica; Ferrari, Márcio; Topan, José Fernando

2016-06-09

The Brazilian biodiversity offers a multiplicity of raw materials with great potential in cosmetics industry applications. Some vegetable oils and fatty esters increase skin hydration by occlusivity, keeping the skin hydrated and with a shiny appearance. Sunflower (Helianthus annus L.) oil is widely employed in cosmetic emulsions in the form of soaps, creams, moisturizers and skin cleansers due to the presence of polyphenols and its high vitamin E content. Liquid crystals are systems with many applications in both pharmaceutical and cosmetic formulations and are easily detected by microscopy under polarized light due to their birefringence properties. The aim of this research was to develop emulsions from natural sunflower oil for topical uses. Sunflower oil (75.0% w/w) was combined with liquid vaseline (25.0% w/w) employing a natural self-emulsifying base (SEB) derivative. The high temperature of the emulsification process did not influence the antioxidant properties of sunflower oil. Fatty esters were added to cosmetic formulations and extended stability tests were performed to characterize the emulsions. Fatty esters like cetyl palmitate and cetyl ester increase the formation of anisotropic structures. O/W emulsions showed acidic pH values and pseudoplastic behavior. The presence of a lamellar phase was observed after a period of 90 days under different storage conditions.
WatAA: Atlas of Protein Hydration. Exploring synergies between data mining and ab initio calculations.

PubMed

Černý, Jiří; Schneider, Bohdan; Biedermannová, Lada

2017-07-14

Water molecules represent an integral part of proteins and a key determinant of protein structure, dynamics and function. WatAA is a newly developed, web-based atlas of amino-acid hydration in proteins. The atlas provides information about the ordered first hydration shell of the most populated amino-acid conformers in proteins. The data presented in the atlas are drawn from two sources: experimental data and ab initio quantum-mechanics calculations. The experimental part is based on a data-mining study of a large set of high-resolution protein crystal structures. The crystal-derived data include 3D maps of water distribution around amino-acids and probability of occurrence of each of the identified hydration sites. The quantum mechanics calculations validate and extend this primary description by optimizing the water position for each hydration site, by providing hydrogen atom positions and by quantifying the interaction energy that stabilizes the water molecule at the particular hydration site position. The calculations show that the majority of experimentally derived hydration sites are positioned near local energy minima for water, and the calculated interaction energies help to assess the preference of water for the individual hydration sites. We propose that the atlas can be used to validate water placement in electron density maps in crystallographic refinement, to locate water molecules mediating protein-ligand interactions in drug design, and to prepare and evaluate molecular dynamics simulations. WatAA: Atlas of Protein Hydration is freely available without login at .
Temperature and pressure correlation for volume of gas hydrates with crystal structures sI and sII

NASA Astrophysics Data System (ADS)

Vinš, Václav; Jäger, Andreas; Hielscher, Sebastian; Span, Roland; Hrubý, Jan; Breitkopf, Cornelia

The temperature and pressure correlations for the volume of gas hydrates forming crystal structures sI and sII developed in previous study [Fluid Phase Equilib. 427 (2016) 268-281], focused on the modeling of pure gas hydrates relevant in CCS (carbon capture and storage), were revised and modified for the modeling of mixed hydrates in this study. A universal reference state at temperature of 273.15 K and pressure of 1 Pa is used in the new correlation. Coefficients for the thermal expansion together with the reference lattice parameter were simultaneously correlated to both the temperature data and the pressure data for the lattice parameter. A two-stage Levenberg Marquardt algorithm was employed for the parameter optimization. The pressure dependence described in terms of the bulk modulus remained unchanged compared to the original study. A constant value for the bulk modulus B0 = 10 GPa was employed for all selected hydrate formers. The new correlation is in good agreement with the experimental data over wide temperature and pressure ranges from 0 K to 293 K and from 0 to 2000 MPa, respectively. Compared to the original correlation used for the modeling of pure gas hydrates the new correlation provides significantly better agreement with the experimental data for sI hydrates. The results of the new correlation are comparable to the results of the old correlation in case of sII hydrates. In addition, the new correlation is suitable for modeling of mixed hydrates.
Properties of inhibitors of methane hydrate formation via molecular dynamics simulations.

PubMed

Anderson, Brian J; Tester, Jefferson W; Borghi, Gian Paolo; Trout, Bernhardt L

2005-12-21

Within the framework of a proposed two-step mechanism for hydrate inhibition, the energy of binding of four inhibitor molecules (PEO, PVP, PVCap, and VIMA) to a hydrate surface is estimated with molecular dynamic simulations. One key feature of this proposed mechanism is that the binding of an inhibitor molecule to the surface of an ensuing hydrate crystal disrupts growth and therein crystallization. It is found through the molecular dynamic simulations that inhibitor molecules that experimentally exhibit better inhibition strength also have higher free energies of binding, an indirect confirmation of our proposed mechanism. Inhibitors increasing in effectiveness, PEO < PVP < PVCap < VIMA, have increasingly negative (exothermic) binding energies of -0.2 < -20.6 < -37.5 < -45.8 kcal/mol and binding free energies of increasing favorability (+0.4 approximately = +0.5 < -9.4 < -15.1 kcal/mol). Furthermore, the effect of an inhibitor molecule on the local liquid water structure under hydrate-forming conditions was examined and correlated to the experimental effectiveness of the inhibitors. Two molecular characteristics that lead to strongly binding inhibitors were found: (1) a charge distribution on the edge of the inhibitor that mimics the charge separation in the water molecules on the surface of the hydrate and (2) the congruence of the size of the inhibitor with respect to the available space at the hydrate-surface binding site. Equipped with this molecular-level understanding of the process of hydrate inhibition via low-dosage kinetic hydrate inhibitors we can design new, more effective inhibitor molecules.
Crystal structure, optical and thermal studies of a new organic nonlinear optical material: L-Histidinium maleate 1.5-hydrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gonsago, C. Alosious; Albert, Helen Merina; Karthikeyan, J.

2012-07-15

Highlights: ► L-Histidinium maleate 1.5-hydrate, a new organic crystal has been grown for the first time. ► The crystal structure is reported for the first time (CCDC 845975). ► The crystal belongs to monoclinic system with space group P2{sub 1}, Z = 4, a = 11.4656(7) Å, b = 8.0530(5) Å, c = 14.9705(9) Å and β = 101.657(2)°. ► The optical absorption study substantiates the complete transparency of the crystal. ► Kurtz powder SHG test confirms the nonlinear property of the crystal. -- Abstract: A new organic nonlinear optical material L-histidinium maleate 1.5-hydrate (LHM) with the molecular formula C{submore » 10}H{sub 16}N{sub 3}O{sub 7.5} has been successfully synthesized from aqueous solution by slow solvent evaporation method. The structural characterization of the grown crystal was carried out by single crystal X-ray diffraction at 293(2) K. In the crystal, molecules are linked through inter and intramolecular N-H⋯O and O-H⋯O hydrogen bonds, generate edge fused ring motif. The hydrogen bonded motifs are linked to each other to form a three dimensional network. The FT-IR spectroscopy was used to identify the functional groups of the synthesized compound. The optical behavior of the grown crystal was examined by UV–visible spectral analysis, which shows that the optical absorption is almost negligible in the wavelength range 280–1300 nm. The nonlinear optical property was confirmed by the powder technique of Kurtz and Perry. The thermal behavior of the grown crystal was analyzed by thermogravimetric analysis.« less
Supramolecular Organization of Nonstoichiometric Drug Hydrates: Dapsone

PubMed Central

Braun, Doris E.; Griesser, Ulrich J.

2018-01-01

The observed moisture- and temperature dependent transformations of the dapsone (4,4′-diaminodiphenyl sulfone, DDS) 0. 33-hydrate were correlated to its structure and the number and strength of the water-DDS intermolecular interactions. A combination of characterization techniques was used, including thermal analysis (hot-stage microscopy, differential scanning calorimetry and thermogravimetric analysis), gravimetric moisture sorption/desorption studies and variable humidity powder X-ray diffraction, along with computational modeling (crystal structure prediction and pair-wise intermolecular energy calculations). Depending on the relative humidity the hydrate contains between 0 and 0.33 molecules of water per molecule DDS. The crystal structure is retained upon dehydration indicating that DDS hydrate shows a non-stoichiometric (de)hydration behavior. Unexpectedly, the water molecules are not located in structural channels but at isolated-sites of the host framework, which is counterintuitively for a hydrate with non-stoichiometric behavior. The water-DDS interactions were estimated to be weaker than water-host interactions that are commonly observed in stoichiometric hydrates and the lattice energies of the isomorphic dehydration product (hydrate structure without water molecules) and (form III) differ only by ~1 kJ mol−1. The computational generation of hypothetical monohydrates confirms that the hydrate with the unusual DDS:water ratio of 3:1 is more stable than a feasible monohydrate structure. Overall, this study highlights that a deeper understanding of the formation of hydrates with non-stoichiometric behavior requires a multidisciplinary approach including suitable experimental and computational methods providing a firm basis for the development and manufacturing of high quality drug products. PMID:29520359
Detection of innersphere interactions between magnesium hydrate and the phosphate backbone of the HDV ribozyme using Raman crystallography.

PubMed

Gong, Bo; Chen, Yuanyuan; Christian, Eric L; Chen, Jui-Hui; Chase, Elaine; Chadalavada, Durga M; Yajima, Rieko; Golden, Barbara L; Bevilacqua, Philip C; Carey, Paul R

2008-07-30

A Raman microscope and Raman difference spectroscopy are used to detect the vibrational signature of RNA-bound magnesium hydrate in crystals of hepatitis delta virus (HDV) ribozyme and to follow the effects of magnesium hydrate binding to the nonbridging phosphate oxygens in the phosphodiester backbone. There is a correlation between the Raman intensity of the innersphere magnesium hydrate signature peak, near 322 cm-1, and the intensity of the PO2- symmetric stretch, near 1100 cm-1, perturbed by magnesium binding, demonstrating direct observation of -PO2-...Mg2+(H2O)x innersphere complexes. The complexes may be pentahydrates (x = 5) and tetrahydrates (x = 4). The assignment of the Raman feature near 322 cm-1 to a magnesium hydrate species is confirmed by isotope shifts observed in D2O and H218O that are semiquantitatively reproduced by calculations. The standardized intensity changes in the 1100 cm-1 PO2- feature seen upon magnesium hydrate binding indicates that there are approximately 5 innersphere Mg2+...-O2P contacts per HDV molecule when the crystal is exposed to a solution containing 20 mM magnesium.
Estimating the Aqueous Solubility of Pharmaceutical Hydrates.

PubMed

Franklin, Stephen J; Younis, Usir S; Myrdal, Paul B

2016-06-01

Estimation of crystalline solute solubility is well documented throughout the literature. However, the anhydrous crystal form is typically considered with these models, which is not always the most stable crystal form in water. In this study, an equation which predicts the aqueous solubility of a hydrate is presented. This research attempts to extend the utility of the ideal solubility equation by incorporating desolvation energetics of the hydrated crystal. Similar to the ideal solubility equation, which accounts for the energetics of melting, this model approximates the energy of dehydration to the entropy of vaporization for water. Aqueous solubilities, dehydration and melting temperatures, and log P values were collected experimentally and from the literature. The data set includes different hydrate types and a range of log P values. Three models are evaluated, the most accurate model approximates the entropy of dehydration (ΔSd) by the entropy of vaporization (ΔSvap) for water, and utilizes onset dehydration and melting temperatures in combination with log P. With this model, the average absolute error for the prediction of solubility of 14 compounds was 0.32 log units. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.
Prediction of Ordered Water Molecules in Protein Binding Sites from Molecular Dynamics Simulations: The Impact of Ligand Binding on Hydration Networks.

PubMed

Rudling, Axel; Orro, Adolfo; Carlsson, Jens

2018-02-26

Water plays a major role in ligand binding and is attracting increasing attention in structure-based drug design. Water molecules can make large contributions to binding affinity by bridging protein-ligand interactions or by being displaced upon complex formation, but these phenomena are challenging to model at the molecular level. Herein, networks of ordered water molecules in protein binding sites were analyzed by clustering of molecular dynamics (MD) simulation trajectories. Locations of ordered waters (hydration sites) were first identified from simulations of high resolution crystal structures of 13 protein-ligand complexes. The MD-derived hydration sites reproduced 73% of the binding site water molecules observed in the crystal structures. If the simulations were repeated without the cocrystallized ligands, a majority (58%) of the crystal waters in the binding sites were still predicted. In addition, comparison of the hydration sites obtained from simulations carried out in the absence of ligands to those identified for the complexes revealed that the networks of ordered water molecules were preserved to a large extent, suggesting that the locations of waters in a protein-ligand interface are mainly dictated by the protein. Analysis of >1000 crystal structures showed that hydration sites bridged protein-ligand interactions in complexes with different ligands, and those with high MD-derived occupancies were more likely to correspond to experimentally observed ordered water molecules. The results demonstrate that ordered water molecules relevant for modeling of protein-ligand complexes can be identified from MD simulations. Our findings could contribute to development of improved methods for structure-based virtual screening and lead optimization.
Rapid gas hydrate formation processes: Will they work?

DOE PAGES

Brown, Thomas D.; Taylor, Charles E.; Bernardo, Mark P.

2010-06-07

Researchers at DOE’s National Energy Technology Laboratory (NETL) have been investigating the formation of synthetic gas hydrates, with an emphasis on rapid and continuous hydrate formation techniques. The investigations focused on unconventional methods to reduce dissolution, induction, nucleation and crystallization times associated with natural and synthetic hydrates studies conducted in the laboratory. Numerous experiments were conducted with various high-pressure cells equipped with instrumentation to study rapid and continuous hydrate formation. The cells ranged in size from 100 mL for screening studies to proof-of-concept studies with NETL’s 15-Liter Hydrate Cell. The results from this work demonstrate that the rapid and continuousmore » formation of methane hydrate is possible at predetermined temperatures and pressures within the stability zone of a Methane Hydrate Stability Curve.« less
Crystallization of uric acid

NASA Astrophysics Data System (ADS)

Kalkura, S. Narayana; Vaidyan, V. K.; Kanakavel, M.; Ramasamy, P.

1993-09-01

Crystals of uric acid have been grown in tetra methoxy silane and silica gel medium. Small winged, transparent, platy crystals of uric acid of about 0.5x0.5x0.1 mm were grown and were found to be hydrated uric acid.
Molecular rotation-vibration dynamics of low-symmetric hydrate crystal in the terahertz region.

PubMed

Fu, Xiaojian; Wu, Hongya; Xi, Xiaoqing; Zhou, Ji

2014-01-16

The rotational and vibrational dynamics of molecules in copper sulfate pentahydrate crystal are investigated with terahertz dielectric spectra. It is shown that the relaxation-like dielectric dispersion in the low frequency region is related to the reorientation of water molecules under the driving of terahertz electric field, whereas the resonant dispersion can be ascribed to lattice vibration. It is also found that, due to the hydrogen-bond effect, the vibrational mode at about 1.83 THz along [-111] direction softens with decreasing temperature, that is, the crystal expands in this direction when cooled. On the contrary, the mode hardens in the direction perpendicular to [-111] during the cooling process. This contributes to the further understanding of the molecular structure and bonding features of hydrate crystals.
Microstructural evolution of gas hydrates in sedimentary matrices observed with synchrotron X-ray computed tomographic microscopy

NASA Astrophysics Data System (ADS)

Chaouachi, Marwen; Falenty, Andrzej; Sell, Kathleen; Enzmann, Frieder; Kersten, Michael; Haberthür, David; Kuhs, Werner F.

2015-06-01

The formation process of gas hydrates in sedimentary matrices is of crucial importance for the physical and transport properties of the resulting aggregates. This process has never been observed in situ at submicron resolution. Here we report on synchrotron-based microtomographic studies by which the nucleation and growth processes of gas hydrate were observed at 276 K in various sedimentary matrices such as natural quartz (with and without admixtures of montmorillonite type clay) or glass beads with different surface properties, at varying water saturation. Both juvenile water and metastably gas-enriched water obtained from gas hydrate decomposition was used. Xenon gas was employed to enhance the density contrast between gas hydrate and the fluid phases involved. The nucleation sites can be easily identified and the various growth patterns are clearly established. In sediments under-saturated with juvenile water, nucleation starts at the water-gas interface resulting in an initially several micrometer thick gas hydrate film; further growth proceeds to form isometric single crystals of 10-20 µm size. The growth of gas hydrate from gas-enriched water follows a different pattern, via the nucleation in the bulk of liquid producing polyhedral single crystals. A striking feature in both cases is the systematic appearance of a fluid phase film of up to several micron thickness between gas hydrates and the surface of the quartz grains. These microstructural findings are relevant for future efforts of quantitative rock physics modeling of gas hydrates in sedimentary matrices and explain the anomalous attenuation of seismic/sonic waves.
Communication: Heterogeneous water dynamics on a clathrate hydrate lattice detected by multidimensional oxygen nuclear magnetic resonance

NASA Astrophysics Data System (ADS)

Adjei-Acheamfour, Mischa; Storek, Michael; Böhmer, Roland

2017-05-01

Previous deuteron nuclear magnetic resonance studies revealed conflicting evidence regarding the possible motional heterogeneity of the water dynamics on the hydrate lattice of an ice-like crystal. Using oxygen-17 nuclei as a sensitive quadrupolar probe, the reorientational two-time correlation function displays a clear nonexponentiality. To check whether this dispersive behavior is a consequence of dynamic heterogeneity or rather of an intrinsic nonexponentiality, a multidimensional, four-time magnetic resonance experiment was devised that is generally applicable to strongly quadrupolarly perturbed half-integer nuclei such as oxygen-17. Measurements of an appropriate four-time function demonstrate that it is possible to select a subensemble of slow water molecules. Its mean time scale is compared to theoretical predictions and evidence for significant motional heterogeneity is found.
Solid-state NMR study of various mono- and divalent cation forms of the natural zeolite natrolite.

PubMed

Park, Min Bum; Vicente, Aurélie; Fernandez, Christian; Hong, Suk Bong

2013-05-28

Here we present the one-dimensional (29)Si and (27)Al MAS NMR and two-dimensional (27)Al MQMAS and DQF-STMAS NMR spectra of the monovalent (Na(+), K(+), Rb(+), Cs(+) and NH4(+)) and divalent (Ca(2+), Sr(2+) and Ba(2+)) cation forms of the natural zeolite natrolite (framework type NAT) with complete Si-Al ordering over the crystallographically distinct tetrahedral sites and with the same hydration state (hydrated, partially dehydrated or fully dehydrated). In the case of monovalent cation-exchanged natrolites, the differences in their crystal symmetry evidenced by (29)Si MAS NMR were found to be in good agreement with those determined by crystallographic analyses. However, (27)Al DQF-STMAS NMR spectroscopy shows the presence of two distinct Al sites in dehydrated K-NAT, Rb-NAT and NH4-NAT, suggesting that their actual crystal symmetry is lower than the reported one (i.e., orthorhombic Fdd2). The MAS NMR results also show that the space group of hydrated Ca-NAT is lower than that (monoclinic F1d1) of hydrated scolecite, the natural calcium counterpart of natrolite, which is also the case with hydrated Sr-NAT and Ba-NAT. We believe that the unexpected diversity in the crystal symmetry of natrolite caused by exchange of various mono- and divalent ions, as well as by dehydration, may be inherently due to the high framework flexibility of this natural zeolite.
The anomalous halogen bonding interactions between chlorine and bromine with water in clathrate hydrates.

PubMed

Dureckova, Hana; Woo, Tom K; Udachin, Konstantin A; Ripmeester, John A; Alavi, Saman

2017-10-13

Clathrate hydrate phases of Cl 2 and Br 2 guest molecules have been known for about 200 years. The crystal structure of these phases was recently re-determined with high accuracy by single crystal X-ray diffraction. In these structures, the water oxygen-halogen atom distances are determined to be shorter than the sum of the van der Waals radii, which indicates the action of some type of non-covalent interaction between the dihalogens and water molecules. Given that in the hydrate phases both lone pairs of each water oxygen atom are engaged in hydrogen bonding with other water molecules of the lattice, the nature of the oxygen-halogen interactions may not be the standard halogen bonds characterized recently in the solid state materials and enzyme-substrate compounds. The nature of the halogen-water interactions for the Cl 2 and Br 2 molecules in two isolated clathrate hydrate cages has recently been studied with ab initio calculations and Natural Bond Order analysis (Ochoa-Resendiz et al. J. Chem. Phys. 2016, 145, 161104). Here we present the results of ab initio calculations and natural localized molecular orbital analysis for Cl 2 and Br 2 guests in all cage types observed in the cubic structure I and tetragonal structure I clathrate hydrates to characterize the orbital interactions between the dihalogen guests and water. Calculations with isolated cages and cages with one shell of coordinating molecules are considered. The computational analysis is used to understand the nature of the halogen bonding in these materials and to interpret the guest positions in the hydrate cages obtained from the X-ray crystal structures.
Computational and Experimental Characterization of Five Crystal Forms of Thymine: Packing Polymorphism, Polytypism/Disorder and Stoichiometric 0.8-Hydrate.

PubMed

Braun, Doris E; Gelbrich, Thomas; Wurst, Klaus; Griesser, Ulrich J

2016-06-01

New polymorphs of thymine emerged in an experimental search for solid forms, which was guided by the computationally generated crystal energy landscape. Three of the four anhydrates (AH) are homeoenergetic ( A° - C ) and their packing modes differ only in the location of oxygen and hydrogen atoms. AHs A° and B are ordered phases, whereas AH C shows disorder (X-ray diffuse scattering). Anhydrates AHs A° and B are ordered phases, whereas AH C shows disorder (X-ray diffuse scattering). Analysis of the crystal energy landscape for alternative AH C hydrogen bonded ribbon motifs identified a number of different packing modes, whose 3D structures were calculated to deviate by less than 0.24 kJ mol -1 in lattice energy. These structures provide models for stacking faults. The three anhydrates A ° - C show strong similarity in their powder X-ray diffraction, thermoanalytical and spectroscopic (IR and Raman) characteristics. The already known anhydrate AH A ° was identified as the thermodynamically most stable form at ambient conditions; AH B and AH C are metastable but show high kinetic stability. The hydrate of thymine is stable only at water activities ( a w ) > 0.95 at temperatures ≤ 25 °C. It was found to be a stoichiometric hydrate despite being a channel hydrate with an unusual water:thymine ratio of 0.8:1. Depending on the dehydration conditions, either AH C or AH D is obtained. The hydrate is the only known precursor to AH D . This study highlights the value and complementarity of simultaneous explorations of computationally and experimentally generated solid form landscapes of a small molecule anhydrate ↔ hydrate system.
Efficacy of Reconstituted Oral Chloral Hydrate from Crystals for Echocardiography Sedation.

PubMed

Hill, Garick D; Walbergh, Deborah B; Frommelt, Peter C

2016-04-01

Chloral hydrate has been the drug of choice for uncooperative infants and children requiring sedation for echocardiography. Recently, the commercially available liquid formulation was discontinued by the manufacturer, and the only oral form of chloral hydrate available was made using reconstituted crystals. The aim of this study was to compare sedation efficacy before and after this change in chloral hydrate formulas. Consecutive patients presenting for echocardiography sedation during the transition from the manufacturer-derived old formulation to the locally reconstituted new formulation were retrospectively reviewed for time to onset of level 3 sedation, duration of level ≤3 sedation, requirement for additional sedative medications, sedation failure, ability to complete the echocardiographic examination, and adverse events related to the sedatives. The cohort included 124 patients (63 old, 61 new). Although the mean age at sedation was younger for the new group, the weight and average dose of chloral hydrate used were not significantly different. There were no adverse events in either group. Time to onset of sedation was the same between the two formulations, but the duration of sedation was significantly shorter for the new group (42.4 ± 24.5 vs 55.3 ± 26.2 min, P = .01). In addition, the need for secondary sedating agents because of inadequate sedation and sedation failure were significantly greater using the new compared with the old formulation. Chloral hydrate reformulation using reconstituted crystals results in a shorter duration of sedation, more frequent requirement for a secondary sedative agent, more frequent sedation failure, and occasional inability to complete the echocardiographic examination compared with the manufacturer's formulation. Copyright © 2016 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.
Computational and Experimental Characterization of Five Crystal Forms of Thymine: Packing Polymorphism, Polytypism/Disorder and Stoichiometric 0.8-Hydrate

PubMed Central

Braun, Doris E.; Gelbrich, Thomas; Wurst, Klaus; Griesser, Ulrich J.

2017-01-01

New polymorphs of thymine emerged in an experimental search for solid forms, which was guided by the computationally generated crystal energy landscape. Three of the four anhydrates (AH) are homeoenergetic (A° – C) and their packing modes differ only in the location of oxygen and hydrogen atoms. AHs A° and B are ordered phases, whereas AH C shows disorder (X-ray diffuse scattering). Anhydrates AHs A° and B are ordered phases, whereas AH C shows disorder (X-ray diffuse scattering). Analysis of the crystal energy landscape for alternative AH C hydrogen bonded ribbon motifs identified a number of different packing modes, whose 3D structures were calculated to deviate by less than 0.24 kJ mol–1 in lattice energy. These structures provide models for stacking faults. The three anhydrates A° – C show strong similarity in their powder X-ray diffraction, thermoanalytical and spectroscopic (IR and Raman) characteristics. The already known anhydrate AH A° was identified as the thermodynamically most stable form at ambient conditions; AH B and AH C are metastable but show high kinetic stability. The hydrate of thymine is stable only at water activities (aw) > 0.95 at temperatures ≤ 25 °C. It was found to be a stoichiometric hydrate despite being a channel hydrate with an unusual water:thymine ratio of 0.8:1. Depending on the dehydration conditions, either AH C or AH D is obtained. The hydrate is the only known precursor to AH D. This study highlights the value and complementarity of simultaneous explorations of computationally and experimentally generated solid form landscapes of a small molecule anhydrate ↔ hydrate system. PMID:28663717
ADR salt pill design and crystal growth process for hydrated magnetic salts

NASA Technical Reports Server (NTRS)

Shirron, Peter J. (Inventor); DiPirro, Michael J. (Inventor); Canavan, Edgar R. (Inventor)

2013-01-01

A process is provided for producing a salt pill for use in very low temperature adiabatic demagnetization refrigerators (ADRs). The method can include providing a thermal bus in a housing. The thermal bus can include an array of thermally conductive metal conductors. A hydrated salt can be grown on the array of thermally conductive metal conductors. Thermal conductance can be provided to the hydrated salt.

Insights into Hydrate Formation and Stability of Morphinanes from a Combination of Experimental and Computational Approaches

PubMed Central

2014-01-01

Morphine, codeine, and ethylmorphine are important drug compounds whose free bases and hydrochloride salts form stable hydrates. These compounds were used to systematically investigate the influence of the type of functional groups, the role of water molecules, and the Cl– counterion on molecular aggregation and solid state properties. Five new crystal structures have been determined. Additionally, structure models for anhydrous ethylmorphine and morphine hydrochloride dihydrate, two phases existing only in a very limited humidity range, are proposed on the basis of computational dehydration modeling. These match the experimental powder X-ray diffraction patterns and the structural information derived from infrared spectroscopy. All 12 structurally characterized morphinane forms (including structures from the Cambridge Structural Database) crystallize in the orthorhombic space group P212121. Hydrate formation results in higher dimensional hydrogen bond networks. The salt structures of the different compounds exhibit only little structural variation. Anhydrous polymorphs were detected for all compounds except ethylmorphine (one anhydrate) and its hydrochloride salt (no anhydrate). Morphine HCl forms a trihydrate and dihydrate. Differential scanning and isothermal calorimetry were employed to estimate the heat of the hydrate ↔ anhydrate phase transformations, indicating an enthalpic stabilization of the respective hydrate of 5.7 to 25.6 kJ mol–1 relative to the most stable anhydrate. These results are in qualitative agreement with static 0 K lattice energy calculations for all systems except morphine hydrochloride, showing the need for further improvements in quantitative thermodynamic prediction of hydrates having water···water interactions. Thus, the combination of a variety of experimental techniques, covering temperature- and moisture-dependent stability, and computational modeling allowed us to generate sufficient kinetic, thermodynamic and structural information to understand the principles of hydrate formation of the model compounds. This approach also led to the detection of several new crystal forms of the investigated morphinanes. PMID:25036525
The dangerous new synthetic drug α-PVP as the hydrated chloride salt α-pyrrolidinopentiophenone hydrochloride 0.786-hydrate.

PubMed

Wood, Matthew R; Bernal, Ivan; Lalancette, Roger A

2016-01-01

α-Pyrrolidinovalerophenone (α-PVP), a dangerous designer drug, is now being marketed around the world as a harmless `bath salt', when in reality it is a powerful β-ketone phenethylamine stimulant. A sample of the free base from a recent law-enforcement seizure was crystallized as the HCl salt [systematic name: 1-(1-oxo-1-phenylpentan-2-yl)pyrrolidin-1-ium chloride 0.786-hydrate], C15H22NO(+)·Cl(-)·0.786H2O. In the crystal structure, the propyl chain is nearly perpendicular to both the phenyl ring and the carbonyl group. The hydrogen-bonding scheme involves the quaternary N atom, the Cl(-) anion and the partially occupied (0.786) water molecule, forming centrosymmetric dimers.
Exploration of crystal simulation potential by fluconazole isomorphism and its application in improvement of pharmaceutical properties

NASA Astrophysics Data System (ADS)

Thakur, Amitha; Kumar, Dinesh; Thipparaboina, Rajesh; Shastri, Nalini R.

2014-11-01

Control of crystal morphology during crystallization is a paramount challenge in pharmaceutical processing. Hence, there is need to introduce computational methods for morphology prediction to manage production cost of drugs and improve related pharmaceutical and biopharmaceutical properties. Layer docking approach with molecular dynamics opens a new avenue for crystal habit prediction in presence of solvent. In the present study, attempts were made to correlate predicted and experimental crystal habits of fluconazole considering solvent interactions using layer docking approach. Simulated results from layer docking approach with methanol as solvent gave two dominant facets (0 1 1) and (1 0 1) with a surface area 22.43% and 19.82% respectively, which were in agreement with the experimental results. Experimentally grown modified crystal habit of fluconazole in methanol showed enhanced dissolution rate (p<0.05) when compared to plain drug. This was attributed to the increased surface area on the specified facets caused by interactions with the solvent. Furthermore, Differential Scanning Calorimetry, Fourier Transform Infrared (FTIR) Spectroscopy and powder X-ray Diffraction of recrystallized samples confirmed only a habit change and absence of any polymorphs, hydrates or solvates. Flow and compressibility of fluconazole recrystallized in methanol was significantly improved when compared to plain drug. This study demonstrates a methodical approach using computational tools for prediction and modification of crystal habit, to enhance dissolution of poorly soluble drugs, for future pharmaceutical applications.
Cage Occupation of Light Hydrocarbons in Gas Hydrate Crystals

NASA Astrophysics Data System (ADS)

Kida, M.; Watanabe, M.; Konno, Y.; Yoneda, J.; Jin, Y.; Nagao, J.

2016-12-01

Naturally occurring gas hydrates in marine or permafrost environments can trap methane and heavier hydrocarbons within its host lattice structure built up with hydrogen-bonded water molecules. Naturally occurring gas hydrates have been expected as new natural gas resources. It is important to reveal the distribution of guest hydrocarbons in host hydrate framework from viewpoint of assessment of gas capacity. In this study, we assessed cage occupancies of guest hydrocarbons in host hydrate framework of synthetic and natural gas hydrates using solid-state 13C NMR technique. As synthetic samples, gas hydrates formed from gas mixtures including C1 to C5 were investigated. As a natural sample, the pore-space gas hydrate sample recovered from the eastern Nankai Trough area during the 2012 JOGMEC/JAPEX Pressure coring operation was studied. As a result, it revealed that all heavier hydrocarbons than ethane are preferentially incorporated into the larger cage cavities in hydrate frameworks. We performed this study as a part of a Japanese National hydrate research program (MH21, funded by METI).
New observations and insights into the morphology and growth kinetics of hydrate films.

PubMed

Li, Sheng-Li; Sun, Chang-Yu; Liu, Bei; Li, Zhi-Yun; Chen, Guang-Jin; Sum, Amadeu K

2014-02-19

The kinetics of film growth of hydrates of methane, ethane, and methane-ethane mixtures were studied by exposing a single gas bubble to water. The morphologies, lateral growth rates, and thicknesses of the hydrate films were measured for various gas compositions and degrees of subcooling. A variety of hydrate film textures was revealed. The kinetics of two-dimensional film growth was inferred from the lateral growth rate and initial thickness of the hydrate film. A clear relationship between the morphology and film growth kinetics was observed. The shape of the hydrate crystals was found to favour heat or mass transfer and favour further growth of the hydrate film. The quantitative results on the kinetics of film growth showed that for a given degree of subcooling, the initial film thicknesses of the double hydrates were larger than that of pure methane or ethane hydrate, whereas the thickest hydrate film and the lowest lateral growth rate occurred when the methane mole fraction was approximately 0.6.
New Observations and Insights into the Morphology and Growth Kinetics of Hydrate Films

PubMed Central

Li, Sheng-Li; Sun, Chang-Yu; Liu, Bei; Li, Zhi-Yun; Chen, Guang-Jin; Sum, Amadeu K.

2014-01-01

The kinetics of film growth of hydrates of methane, ethane, and methane-ethane mixtures were studied by exposing a single gas bubble to water. The morphologies, lateral growth rates, and thicknesses of the hydrate films were measured for various gas compositions and degrees of subcooling. A variety of hydrate film textures was revealed. The kinetics of two-dimensional film growth was inferred from the lateral growth rate and initial thickness of the hydrate film. A clear relationship between the morphology and film growth kinetics was observed. The shape of the hydrate crystals was found to favour heat or mass transfer and favour further growth of the hydrate film. The quantitative results on the kinetics of film growth showed that for a given degree of subcooling, the initial film thicknesses of the double hydrates were larger than that of pure methane or ethane hydrate, whereas the thickest hydrate film and the lowest lateral growth rate occurred when the methane mole fraction was approximately 0.6. PMID:24549241
In situ nanomanipulators as a tool to separate individual tobermorite crystals for AFM studies.

PubMed

Yang, Tianhe; Holzer, Lorenz; Kägi, Ralf; Winnefeld, Frank; Keller, Bruno

2007-10-01

Atomic force microscopy (AFM) studies of cementitious materials are limited, mainly due to the lack of appropriate sample preparation techniques. In porous autoclaved aerated concrete (AAC), calcium silicate hydrate (C-S-H) is produced in its crystalline form, tobermorite. The crystals are lath-like with a length of several micrometers. In this work, we demonstrate the application of nanomanipulators to separate an individual tobermorite crystal from the bulk AAC for subsequent AFM investigations. The nanomanipulators are operated directly in an environmental scanning electron microscope (ESEM). We studied the interaction between moisture and the tobermorite surface under controlled relative humidity (RH). The results of topography and adhesion force measurements with AFM suggest that the surface of tobermorite is hydrophobic, which contrasts the macroscopic material properties (e.g. moisture transport in capillary pores).
Membrane protein crystallization in meso: lipid type-tailoring of the cubic phase.

PubMed Central

Cherezov, Vadim; Clogston, Jeffrey; Misquitta, Yohann; Abdel-Gawad, Wissam; Caffrey, Martin

2002-01-01

Hydrated monoolein forms the cubic-Pn3m mesophase that has been used for in meso crystallization of membrane proteins. The crystals have subsequently provided high-resolution structures by crystallographic means. It is possible that the hosting cubic phase created by monoolein alone, which itself is not a common membrane component, will limit the range of membrane proteins crystallizable by the in meso method. With a view to expanding the range of applicability of the method, we investigated by x-ray diffraction the degree to which the reference cubic-Pn3m phase formed by hydrated monoolein could be modified by other lipid types. These included phosphatidylcholine (PC), phosphatidylethanolamine, phosphatidylserine, cardiolipin, lyso-PC, a polyethylene glycol-lipid, 2-monoolein, oleamide, and cholesterol. The results show that all nine lipids were accommodated in the cubic phase to some extent without altering phase identity. The positional isomer, 2-monoolein, was tolerated to the highest level. The least well tolerated were the anionic lipids, followed by lyso-PC. The others were accommodated to the extent of 20-25 mol %. Beyond a certain concentration limit, the lipid additives either triggered one or a series of phase transitions or saturated the phase and separated out as crystals, as seen with oleamide and cholesterol. The series of phases observed and their order of appearance were consistent with expectations in terms of interfacial curvature changes. The changes in phase type and microstructure have been rationalized on the basis of lipid molecular shape, interfacial curvature, and chain packing energy. The data should prove useful in the rational design of cubic phase crystallization matrices with different lipid profiles that match the needs of a greater range of membrane proteins. PMID:12496106
Crystallization Experiments in the MgO-CO2-H2O system: Role of Amorphous Magnesium Carbonate Precursors in Magnesium Carbonate Hydrated Phases and Morphologies in Low Temperature Hydrothermal Fluids

NASA Astrophysics Data System (ADS)

Giampouras, Manolis; Garcia-Ruiz, Juan Manuel; Garrido, Carlos J.

2017-04-01

Numerous forms of hydrated or basic magnesium carbonates occur in the complex MgO-CO2-H2O system. Mineral saturation states from low temperature hydrothermal fluids in Semail Ophiolite (Oman), Prony Bay (New Caledonia) and Lost City hydrothermal field (mid-Atlantic ridge) strongly indicate the presence of magnesium hydroxy-carbonate hydrates (e.g. hydromagnesite) and magnesium hydroxides (brucite). Study of formation mechanisms and morphological features of minerals forming in the MgO-CO2-H2O system could give insights into serpentinization-driven, hydrothermal, alkaline environments, which are related to early Earth conditions. Temperature, hydration degree, pH and fluid composition are crucial factors regarding the formation, coexistence and transformation of such mineral phases. The rate of supersaturation, on the other hand, is a fundamental parameter to understand nucleation and crystal growth processes. All these parameters can be examined in a solution using different crystallization techniques. In the present study, we applied different crystallization techniques to synthesize and monitor the crystallization of Mg-bearing carbonates and hydroxides under abiotic conditions. Various crystallization techniques (counter-diffusion, vapor diffusion and unseeded solution mixing) were used to screen the formation conditions of each phase, transformation processes and structural development. Mineral and textural characterization of the different synthesized phases were carried out by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy coupled to dispersive energy spectroscopy (FE-SEM-EDS). Experimental investigation of the effect of pH level and silica content under variable reactant concentrations revealed the importance of Amorphous Magnesium Carbonate (AMC) in the formation of hydroxy-carbonate phases (hydromagnesite and dypingite). Micro-structural resemblance between AMC precursors and later stage crystalline phases highlights the critical role of internal molecule re-organization to form crystalline structures. Aggregation of AMC spherulites triggers biomimetic morphologies forming curling laminar structures and rings. The size and number of nesquehonite (MgCO3.3H2O) crystals are controlled by pH and Mg2+ ions at pH < 9. As pH increases, nesquehonite transforms to spherical, rosette-like dypingite and/or hydromagnesite. Crystallization experiments within silica gel impedes the normal growth of prismatic nesquehonite crystals and generates peculiar dendritic crystalline structures. Finally, vapor diffusion techniques resulted in synthesis of NH4+-bearing hydrated compounds after ammonium incorporation when [NH4+]/[Mg2+] ≥ 1 and ≥ 0.5M [NH4+]. Funding: We acknowledge funding from the People programme (Marie Curie Actions - ITN) of the European Union FP7 under REA Grant Agreement n˚ 608001.
Small Effect of Hydration on Elastic Wave Velocities of Ringwoodite in Earth's Transition Zone

NASA Astrophysics Data System (ADS)

Schulze, K.; Marquardt, H.; Boffa Ballaran, T.; Kurnosov, A.; Kawazoe, T.; Koch-Müller, M.

2017-12-01

Ringwoodite can incorporate significant amounts of hydrogen as OH-defects into its crystal structure. The measurement of 1.4 wt.% H20 in a natural ringwoodite diamond inclusion (Pearson et al. 2014) showed that hydrous ringwoodite can exist in the Earth's mantle. Since ringwoodite is considered to be the major phase in the mantle between 520 and 660 km depth it likely plays an important role for Earth's deep water cycle and the mantle water budget. Previous experimental work has shown that hydration reduces seismic wave velocities in ringwoodite, motivating attempts to map the hydration state of the mantle using seismic wave speed variations as depicted by seismic tomography. However, large uncertainties on the actual effects at transition zone pressures and temperatures remain. A major difficulty is the comparability of studies with different experimental setups and pressure- and temperature conditions. Here, we present results from a comparative elasticity study designed to quantify the effects of hydration on the seismic wave velocities of ringwoodite in Earth's transition zone. Focused ion beam cut single-crystals of four samples of either Fo90 or Fo100 ringwoodite with hydration states between 0.21 - 1.71 wt.% H2O were loaded in the pressure chamber of one diamond-anvil cell to ensure identical experimental conditions. Single-crystal Brillouin Spectroscopy and X-ray diffraction measurements were performed at room temperature to a pressure of 22 GPa. Additional experiments at high pressure and temperatures up to 500 K were performed. Our data collected at low pressures show a significant reduction of elastic wave velocities with hydration, consistent with previous work. However, in contrast to previous inferences, our results indicate that pressure significantly reduces the effect of hydration. Based on the outcome of our work, the redution in aggregate velocities caused by 1 wt.% H2O becomes smaller than 1% in ringwoodite at pressures equivalent to the Earth's transition zone. The detection of differences in the hydration state in pyrolitic mantle with about 56% ringwoodite by seismic tomography, might therefore be only possible in mantle regions of very high water contents.
Acemetacin cocrystal structures by powder X-ray diffraction.

PubMed

Bolla, Geetha; Chernyshev, Vladimir; Nangia, Ashwini

2017-05-01

Cocrystals of acemetacin drug (ACM) with nicotinamide (NAM), p -aminobenzoic acid (PABA), valerolactam (VLM) and 2-pyridone (2HP) were prepared by melt crystallization and their X-ray crystal structures determined by high-resolution powder X-ray diffraction. The powerful technique of structure determination from powder data (SDPD) provided details of molecular packing and hydrogen bonding in pharmaceutical cocrystals of acemetacin. ACM-NAM occurs in anhydrate and hydrate forms, whereas the other structures crystallized in a single crystalline form. The carboxylic acid group of ACM forms theacid-amide dimer three-point synthon R 3 2 (9) R 2 2 (8) R 3 2 (9) with three different syn amides (VLM, 2HP and caprolactam). The conformations of the ACM molecule observed in the crystal structures differ mainly in the mutual orientation of chlorobenzene fragment and the neighboring methyl group, being anti (type I) or syn (type II). ACM hydrate, ACM-NAM, ACM-NAM-hydrate and the piperazine salt of ACM exhibit the type I conformation, whereas ACM polymorphs and other cocrystals adopt the ACM type II conformation. Hydrogen-bond interactions in all the crystal structures were quantified by calculating their molecular electrostatic potential (MEP) surfaces. Hirshfeld surface analysis of the cocrystal surfaces shows that about 50% of the contribution is due to a combination of strong and weak O⋯H, N⋯H, Cl⋯H and C⋯H interactions. The physicochemical properties of these cocrystals are under study.
Acemetacin cocrystal structures by powder X-ray diffraction

PubMed Central

Bolla, Geetha

2017-01-01

Cocrystals of acemetacin drug (ACM) with nicotinamide (NAM), p-aminobenzoic acid (PABA), valerolactam (VLM) and 2-pyridone (2HP) were prepared by melt crystallization and their X-ray crystal structures determined by high-resolution powder X-ray diffraction. The powerful technique of structure determination from powder data (SDPD) provided details of molecular packing and hydrogen bonding in pharmaceutical cocrystals of acemetacin. ACM–NAM occurs in anhydrate and hydrate forms, whereas the other structures crystallized in a single crystalline form. The carboxylic acid group of ACM forms theacid–amide dimer three-point synthon R 3 2(9)R 2 2(8)R 3 2(9) with three different syn amides (VLM, 2HP and caprolactam). The conformations of the ACM molecule observed in the crystal structures differ mainly in the mutual orientation of chlorobenzene fragment and the neighboring methyl group, being anti (type I) or syn (type II). ACM hydrate, ACM—NAM, ACM–NAM-hydrate and the piperazine salt of ACM exhibit the type I conformation, whereas ACM polymorphs and other cocrystals adopt the ACM type II conformation. Hydrogen-bond interactions in all the crystal structures were quantified by calculating their molecular electrostatic potential (MEP) surfaces. Hirshfeld surface analysis of the cocrystal surfaces shows that about 50% of the contribution is due to a combination of strong and weak O⋯H, N⋯H, Cl⋯H and C⋯H interactions. The physicochemical properties of these cocrystals are under study. PMID:28512568
Raman studies of methane-ethane hydrate metastability.

PubMed

Ohno, Hiroshi; Strobel, Timothy A; Dec, Steven F; Sloan, E Dendy; Koh, Carolyn A

2009-03-05

The interconversion of methane-ethane hydrate from metastable to stable structures was studied using Raman spectroscopy. sI and sII hydrates were synthesized from methane-ethane gas mixtures of 65% or 93% methane in ethane and water, both with and without the kinetic hydrate inhibitor, poly(N-vinylcaprolactam). The observed faster structural conversion rate in the higher methane concentration atmosphere can be explained in terms of the differences in driving force (difference in chemical potential of water in sI and sII hydrates) and kinetics (mass transfer of gas and water rearrangement). The kinetic hydrate inhibitor increased the conversion rate at 65% methane in ethane (sI is thermodynamically stable) but retards the rate at 93% methane in ethane (sII is thermodynamically stable), implying there is a complex interaction between the polymer, water, and hydrate guests at crystal surfaces.
Structural and spectroscopic features of proton hydrates in the crystalline state. Solid-state DFT study on HCl and triflic acid hydrates

NASA Astrophysics Data System (ADS)

Vener, M. V.; Chernyshov, I. Yu.; Rykounov, A. A.; Filarowski, A.

2018-01-01

Crystalline HCl and CF3SO3H hydrates serve as excellent model systems for protonated water and perfluorosulphonic acid membranes, respectively. They contain characteristic H3O+, H5О+2, H7О+3 and H3O+(H2O)3 (the Eigen cation) structures. The properties of these cations in the crystalline hydrates of strong monobasic acids are studied by solid-state density function theory (DFT). Simultaneous consideration of the HCl and CF3SO3H hydrates reveals the impact of the size of a counter ion and the crystalline environment on the structure and infrared active bands of the simplest proton hydrates. The H7O+3 structure is very sensitive to the size of the counter ion and symmetry of the local environment. This makes it virtually impossible to identify the specific features of H7O+3 in molecular crystals. The H3O+ ion can be treated as the Eigen-like cation in the crystalline state. Structural, infrared and electron-density features of H5О+2 and the Eigen cation are virtually insensitive to the size of the counter ion and the symmetry of the local crystalline environment. These cations can be considered as the simplest stable proton hydrates in the condensed phase. Finally, the influence of the Grimme correction on the structure and harmonic frequencies of the molecular crystals with short (strong) intermolecular O-H···O bonds is discussed.
Research opportunities in salt hydrates for thermal energy storage

NASA Astrophysics Data System (ADS)

Braunstein, J.

1983-11-01

The state of the art of salt hydrates as phase change materials for low temperature thermal energy storage is reviewed. Phase equilibria, nucleation behavior and melting kinetics of the commonly used hydrate are summarized. The development of efficient, reliable inexpensive systems based on phase change materials, especially salt hydrates for the storage (and retrieval) of thermal energy for residential heating is outlined. The use of phase change material thermal energy storage systems is not yet widespread. Additional basic research is needed in the areas of crystallization and melting kinetics, prediction of phase behavior in ternary systems, thermal diffusion in salt hydrate systems, and in the physical properties pertinent to nonequilibrium and equilibrium transformations in these systems.
A crystal-chemical classification of borate structures with emphasis on hydrated borates

USGS Publications Warehouse

Christ, C.L.; Clark, J.R.

1977-01-01

The rules governing formation of hydrated borate polyanions that were proposed by C.L. Christ in 1960 are critically reviewed and new rules added on the basis of recent crystal structure determinations. Principles and classifications previously published by others are also critically reviewed briefly. The fundamental building blocks from which borate polyanions can be constructed are defined on the basis of the number n of boron atoms, and the fully hydrated polyanions are illustrated. Known structures are grouped accordingly, and a shorthand notation using n and symbols ?? = triangle, T = tetrahedron is introduced so that the polyanions can be easily characterized. For example, 3:??+2T describes [B3O3(OH)5]2-. Correct structural formulas are assigned borates with known structures whereas borates of unknown structure are grouped separately. ?? 1977 Springer-Verlag.
Influence of Carbon Nanotubes on the Structure Formation of Cement Matrix

NASA Astrophysics Data System (ADS)

Petrunin, S.; Vaganov, V.; Reshetniak, V.; Zakrevskaya, L.

2015-11-01

The potential of application of CNTs as a reinforcing agent in cement composites is governed by their unique mechanical and electronic properties. The analysis of concrete strength changes under CNTs introduction shows non-uniformity and sometimes inconsistency of results. Due to the fact that CNTs influence the hydration kinetics, structure and phase composition of concrete, an idea concerning the importance of interaction between the surface of CNTs and hydrate ions formed by the dissolution of the clinker phases has been suggested. In this paper, the theoretical and experimental study of interaction between hydrate ions and CNTs surface is discussed. Reference nanotubes and nanotubes functionalized by carboxylic groups are used in this research. Phase composition was determined by X-Ray analysis according to the Rietveld method. It was found that the presence of oxygen-containing functional groups on CNTs surface leads to intensification of the hydration process and increase in concentration of C-S-H gel from 65.9% to 74.4%. Special attention is usually paid to interactions between Ca2+ ions and CNTs, because the hardening rate and structure of cement stone are determined by principle of Ca2+ localization in the solution. In this paper the possible binding mechanisms are discussed. Based on the experimental results, the hypothesis regarding the formation of cement composite structure for different CNTs surface functionalizations is considered. According to this hypothesis, the CNTs act as the centers of crystallization for hydration products contributing to the acceleration of hydration, increase of the concentration of C-S-H gel and strength improvement of CNTs based composites.
Survey and analysis of crystal polymorphism in organic structures

PubMed Central

Kaur, Ramanpreet

2018-01-01

With the intention of producing the most comprehensive treatment of the prevalence of crystal polymorphism among structurally characterized materials, all polymorphic compounds flagged as such within the Cambridge Structural Database (CSD) are analysed and a list of crystallographically characterized organic polymorphic compounds is assembled. Classifying these structures into subclasses of anhydrates, salts, hydrates, non-hydrated solvates and cocrystals reveals that there are significant variations in polymorphism prevalence as a function of crystal type, a fact which has not previously been recognized in the literature. It is also shown that, as a percentage, polymorphic entries are decreasing temporally within the CSD, with the notable exception of cocrystals, which continue to rise at a rate that is a constant fraction of the overall entries. Some phenomena identified that require additional scrutiny include the relative prevalence of temperature-induced phase transitions among organic salts and the paucity of polymorphism in crystals with three or more chemical components. PMID:29765601
Effects of Detergent β-Octylglucoside and Phosphate Salt Solutions on Phase Behavior of Monoolein Mesophases

PubMed Central

Khvostichenko, Daria S.; Ng, Johnathan J.D.; Perry, Sarah L.; Menon, Monisha; Kenis, Paul J.A.

2013-01-01

Using small-angle x-ray scattering (SAXS), we investigated the phase behavior of mesophases of monoolein (MO) mixed with additives commonly used for the crystallization of membrane proteins from lipidic mesophases. In particular, we examined the effect of sodium and potassium phosphate salts and the detergent β-octylglucoside (βOG) over a wide range of compositions relevant for the crystallization of membrane proteins in lipidic mesophases. We studied two types of systems: 1), ternary mixtures of MO with salt solutions above the hydration boundary; and 2), quaternary mixtures of MO with βOG and salt solutions over a wide range of hydration conditions. All quaternary mixtures showed highly regular lyotropic phase behavior with the same sequence of phases (Lα, Ia3d, and Pn3m) as MO/water mixtures at similar temperatures. The effects of additives in quaternary systems agreed qualitatively with those found in ternary mixtures in which only one additive is present. However, quantitative differences in the effects of additives on the lattice parameters of fully hydrated mesophases were found between ternary and quaternary mixtures. We discuss the implications of these findings for mechanistic investigations of membrane protein crystallization in lipidic mesophases and for studies of the suitability of precipitants for mesophase-based crystallization methods. PMID:24138861
Dehydration process in NaCl solutions under various external electric fields

NASA Astrophysics Data System (ADS)

Kadota, Kazunori; Shimosaka, Atsuko; Shirakawa, Yoshiyuki; Hidaka, Jusuke

2007-06-01

Ionic motions at solid-liquid interface in supersaturated NaCl solutions have been investigated by molecular dynamics (MD) simulation for understanding crystal growth processes. The density profile in the vicinity of the interfaces between NaCl(100) and the supersaturated NaCl solution was calculated. Diffusion coefficients of water molecules in the solution were estimated as a function of distance from the crystal interface. It turned out that the structure and dynamics of the solution in the interfaces was different from those of bulk solution owing to electric fields depending on the surface charge. Therefore, the electric field was applied to the supersaturated solutions and dehydration phenomenon occurring in the process of the crystal growth was discussed. As the electric field increased, it was observed that the Na+ keeping strongly hydration structure broke out by the electric force. In supersaturated concentration, the solution structure is significantly different from that of dilution and has a complicated structure with hydration ions and clusters of NaCl. If the electric fields were applied to the solutions, the breakout of hydration structure was not affected with increasing the supersaturated ratio. This reason is that the cluster structures are destroyed by the electric force. The situation depends on the electric field or crystal surface structure.

Evidence of ammonium ion-exchange properties of natural bentonite and application to ammonium detection.

PubMed

Zazoua, A; Kazane, I; Khedimallah, N; Dernane, C; Errachid, A; Jaffrezic-Renault, N

2013-12-01

Ammonium exchange with hybrid PVC-bentonite (mineral montmorillonite clay) thin film was revealed using FTIR spectroscopy, EDX, cyclic voltammetry and electrochemical impedance spectroscopy. The effect of ammonium exchange on the charge transfer resistance of PVC-bentonite hybrid thin film was attributed to a modification of the intersheet distance and hydration of bentonite crystals. The obtained impedimetric ammonium sensor shows a linear range of detection from 10(-4)M to 1M and a detection limit around 10(-6)M. © 2013.
Comments on the paper: 'Optical reflectance, optical refractive index and optical conductivity measurements of nonlinear optics for L-aspartic acid nickel chloride single crystal'

NASA Astrophysics Data System (ADS)

Srinivasan, Bikshandarkoil R.; Naik, Suvidha G.; Dhavskar, Kiran T.

2016-02-01

We argue that the 'L-aspartic acid nickel chloride' crystal reported by the authors of the title paper (Optics Communications, 291 (2013) 304-308) is actually the well-known diaqua(L-aspartato)nickel(II) hydrate crystal.
Quantitative assessment of combination bathing and moisturizing regimens on skin hydration in atopic dermatitis.

PubMed

Chiang, Charles; Eichenfield, Lawrence F

2009-01-01

Standard recommendations for skin care for patients with atopic dermatitis stress the importance of skin hydration and the application of moisturizers. However, objective data to guide recommendations regarding the optimal practice methods of bathing and emollient application are scarce. This study quantified cutaneous hydration status after various combination bathing and moisturizing regimens. Four bathing/moisturizer regimens were evaluated in 10 subjects, five pediatric subjects with atopic dermatitis and five subjects with healthy skin. The regimens consisted of bathing alone without emollient application, bathing and immediate emollient application, bathing and delayed application, and emollient application alone. Each regimen was evaluated in all subjects, utilizing a crossover design. Skin hydration was assessed with standard capacitance measurements. In atopic dermatitis subjects, emollient alone yielded a significantly (p < 0.05) greater mean hydration over 90 minutes (206.2% baseline hydration) than bathing with immediate emollient (141.6%), bathing and delayed emollient (141%), and bathing alone (91.4%). The combination bathing and emollient application regimens demonstrated hydration values at 90 minutes not significantly greater than baseline. Atopic dermatitis subjects had a decreased mean hydration benefit compared with normal skin subjects. Bathing without moisturizer may compromise skin hydration. Bathing followed by moisturizer application provides modest hydration benefits, though less than that of simply applying moisturizer alone.
Gas hydrate property measurements in porous sediments with resonant ultrasound spectroscopy

NASA Astrophysics Data System (ADS)

McGrail, B. P.; Ahmed, S.; Schaef, H. T.; Owen, A. T.; Martin, P. F.; Zhu, T.

2007-05-01

Resonant ultrasound spectroscopy was used to characterize a natural geological core sample obtained from the Mallik 5L-38 gas hydrate research well at high pressure and subambient temperatures. Using deuterated methane gas to form gas hydrate in the core sample, it was discovered that resonance amplitudes are correlated with the fraction of the pore space occupied by the gas hydrate crystals. A pore water freezing model was developed that utilizes the known pore size distribution and pore water chemistry to predict gas hydrate saturation as a function of pressure and temperature. The model showed good agreement with the experimental measurements and demonstrated that pore water chemistry is the most important factor controlling equilibrium gas hydrate saturations in these sediments when gas hydrates are formed artificially in laboratory pressure vessels. With further development, the resonant ultrasound technique can provide a rapid, nondestructive, field portable means of measuring the equilibrium P-T properties and dissociation kinetics of gas hydrates in porous media, determining gas hydrate saturations, and may provide new insights into the nature of gas hydrate formation mechanisms in geologic materials.
Lyotropic liquid crystal engineering moving beyond binary compositional space - ordered nanostructured amphiphile self-assembly materials by design.

PubMed

van 't Hag, Leonie; Gras, Sally L; Conn, Charlotte E; Drummond, Calum J

2017-05-22

Ordered amphiphile self-assembly materials with a tunable three-dimensional (3D) nanostructure are of fundamental interest, and crucial for progressing several biological and biomedical applications, including in meso membrane protein crystallization, as drug and medical contrast agent delivery vehicles, and as biosensors and biofuel cells. In binary systems consisting of an amphiphile and a solvent, the ability to tune the 3D cubic phase nanostructure, lipid bilayer properties and the lipid mesophase is limited. A move beyond the binary compositional space is therefore required for efficient engineering of the required material properties. In this critical review, the phase transitions upon encapsulation of more than 130 amphiphilic and soluble additives into the bicontinuous lipidic cubic phase under excess hydration are summarized. The data are interpreted using geometric considerations, interfacial curvature, electrostatic interactions, partition coefficients and miscibility of the alkyl chains. The obtained lyotropic liquid crystal engineering design rules can be used to enhance the formulation of self-assembly materials and provides a large library of these materials for use in biomedical applications (242 references).
The Effect of Compaction Force on the Transition to Hydrate of Anhydrous Aripiprazole.

PubMed

Togo, Taichiro; Taniguchi, Toshiya; Nakata, Yoshitaka

2018-01-01

Aripiprazole (APZ) is used to treat schizophrenia and is administered as a tablet containing the anhydrous form of APZ. In this study, the effect of compaction force on the crystal form transition was investigated. The crystalline state was observed by X-ray diffraction (XRD). APZ Anhydrous Form II was compacted into tablets. The XRD intensity of anhydrous APZ became lower with higher compressive force. The degree of crystallinity decreased with the compaction force. The powder and the compacted tablets of anhydrous APZ were stored for one week under 60°C and 75% relative humidity. The powder showed no crystal form transition after storage. For the tablets, however, XRD peaks of APZ hydrate were observed after storage. The tablets compacted with higher force showed the higher XRD diffraction intensity of hydrate form. We concluded that the crystallinity reduction of APZ Anhydrous Form II by compaction caused and accelerated the transition to hydrate under high temperature and humidity conditions. In order to manufacture crystallographically stable tablets containing anhydrous APZ, it is important to prevent this crystallinity reduction during compaction.
Time-dependent water dynamics in hydrated uranyl fluoride

DOE PAGES

Miskowiec, Andrew J.; Anderson, Brian B.; Herwig, Kenneth W.; ...

2015-09-15

In this study, uranyl fluoride is a three-layer, hexagonal structure with significant stacking disorder in the c-direction. It supports a range of unsolved ‘thermodynamic’ hydrates with 0–2.5 water molecules per uranium atom, and perhaps more. However, the relationship between water, hydrate crystal structures, and thermodynamic results, collectively representing the chemical pathway through these hydrate structures, has not been sufficiently elucidated. We used high-resolution quasielastic neutron scattering to study the dynamics of water in partially hydrated uranyl fluoride powder over the course of 4 weeks under closed conditions. The spectra are composed of two quasielastic components: one is associated with translationalmore » diffusive motion of water that is approximately five to six times slower than bulk water, and the other is a slow (on the order of 2–300 ps), spatially bounded water motion. The translational component represents water diffusing between the weakly bonded layers in the crystal, while the bounded component may represent water trapped in subnanometre ‘pockets’ formed by the space between uranium-centred polymerisation units. Complementary neutron diffraction measurements do not show any significant structural changes, suggesting that a chemical conversion of the material does not occur in the thermodynamically isolated system on this timescale.« less
Phase transitions in biogenic amorphous calcium carbonate

NASA Astrophysics Data System (ADS)

Gong, Yutao

Geological calcium carbonate exists in both crystalline phases and amorphous phases. Compared with crystalline calcium carbonate, such as calcite, aragonite and vaterite, the amorphous calcium carbonate (ACC) is unstable. Unlike geological calcium carbonate crystals, crystalline sea urchin spicules (99.9 wt % calcium carbonate and 0.1 wt % proteins) do not present facets. To explain this property, crystal formation via amorphous precursors was proposed in theory. And previous research reported experimental evidence of ACC on the surface of forming sea urchin spicules. By using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), we studied cross-sections of fresh sea urchin spicules at different stages (36h, 48h and 72h after fertilization) and observed the transition sequence of three mineral phases: hydrated ACC → dehydrated ACC → biogenic calcite. In addition, we unexpectedly found hydrated ACC nanoparticles that are surrounded by biogenic calcite. This observation indicates the dehydration from hydrated ACC to dehydrated ACC is inhibited, resulting in stabilization of hydrated ACC nanoparticles. We thought that the dehydration was inhibited by protein matrix components occluded within the biomineral, and we designed an in vitro assay to test the hypothesis. By utilizing XANES-PEEM, we found that SM50, the most abundant occluded matrix protein in sea urchin spicules, has the function to stabilize hydrated ACC in vitro.
Hydration kinetics of cementitious materials composed of red mud and coal gangue

NASA Astrophysics Data System (ADS)

Zhang, Na; Li, Hong-xu; Liu, Xiao-ming

2016-10-01

To elucidate the intrinsic reaction mechanism of cementitious materials composed of red mud and coal gangue (RGC), the hydration kinetics of these cementitious materials at 20°C was investigated on the basis of the Krstulović-Dabić model. An isothermal calorimeter was used to characterize the hydration heat evolution. The results show that the hydration of RGC is controlled by the processes of nucleation and crystal growth (NG), interaction at phase boundaries (I), and diffusion (D) in order, and the pozzolanic reactions of slag and compound-activated red mud-coal gangue are mainly controlled by the I process. Slag accelerates the clinker hydration during NG process, whereas the compound-activated red mud-coal gangue retards the hydration of RGC and the time required for I process increases with increasing dosage of red mud-coal gangue in RGC.
Authigenic rhodochrosite from a gas hydrate-bearing structure in Lake Baikal

NASA Astrophysics Data System (ADS)

Krylov, Alexey A.; Hachikubo, Akihiro; Minami, Hirotsugu; Pogodaeva, Tatyana V.; Zemskaya, Tamara I.; Krzhizhanovskaya, Mariya G.; Poort, Jeffrey; Khlystov, Oleg M.

2018-02-01

Early diagenetic carbonates are rare in Lake Baikal. Siderite (Fe carbonate) concretions in the sediments were discovered only recently. Here, we discuss the first finding of rhodochrosite concretions (Mn carbonate) discovered in the near-bottom sediments of the gas hydrate-bearing seepage structure St. Petersburg-2 in the deep water environment of the Central Baikal Basin. The crystal lattice of rhodochrosite contains iron and calcium substituting to manganese. Based on pore water geochemistry and of δ 13C values of rhodochrosite (- 23.3 and - 29.4‰), carbon dioxide (+ 3.8 to - 16.1‰) and methane (- 63.2 to - 67.8‰), we show that carbonate crystallization most likely occurred during microbial anaerobic oxidation of organic matter, and that part of the oxygen making up the rhodochrosite seems to be derived from the 18O-rich water released from dissociating gas hydrates.
Microscopic diffusion in hydrated encysted eggs of brine shrimp

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mamontov, Eugene

We have studied microscopic diffusion of water in fully hydrated encysted eggs of brine shrimp (Artemia). We utilized quasielastic neutron scattering. Dry eggs of brine shrimp were rehydrated using (1) water without additives, (2) eutectic mixture of water and dimethyl sulfoxide, and (3) a concentrated aqueous solution of lithium chloride. Despite the complexity of the hydrated multicellular organism, measurable microscopic diffusivity of water is rather well defined. Pure hydration water in eggs exhibits freezing temperature depression, whereas hydration water in eggs mixed with dimethyl sulfoxide or lithium chloride does not crystallize at all. The characteristic size of the voids occupiedmore » by water or aqueous solvents in hydrated brine shrimp eggs is between 2 and 10 nm. Those voids are accessible to co-solvents such as dimethyl sulfoxide and lithium chloride. There is no evidence of intracellular water in the hydrated eggs. The lack of intracellular water in the fully hydrated (but still under arrested development) state must be linked to the unique resilience against adverse environmental factors documented not only for the anhydrous, but also hydrated encysted eggs of brine shrimp.« less
Microscopic diffusion in hydrated encysted eggs of brine shrimp

DOE PAGES

Mamontov, Eugene

2017-05-24

We have studied microscopic diffusion of water in fully hydrated encysted eggs of brine shrimp (Artemia). We utilized quasielastic neutron scattering. Dry eggs of brine shrimp were rehydrated using (1) water without additives, (2) eutectic mixture of water and dimethyl sulfoxide, and (3) a concentrated aqueous solution of lithium chloride. Despite the complexity of the hydrated multicellular organism, measurable microscopic diffusivity of water is rather well defined. Pure hydration water in eggs exhibits freezing temperature depression, whereas hydration water in eggs mixed with dimethyl sulfoxide or lithium chloride does not crystallize at all. The characteristic size of the voids occupiedmore » by water or aqueous solvents in hydrated brine shrimp eggs is between 2 and 10 nm. Those voids are accessible to co-solvents such as dimethyl sulfoxide and lithium chloride. There is no evidence of intracellular water in the hydrated eggs. The lack of intracellular water in the fully hydrated (but still under arrested development) state must be linked to the unique resilience against adverse environmental factors documented not only for the anhydrous, but also hydrated encysted eggs of brine shrimp.« less
In-situ early-age hydration study of sulfobelite cements by synchrotron powder diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Álvarez-Pinazo, G.; Cuesta, A.; García-Maté, M.

Eco-friendly belite calcium sulfoaluminate (BCSA) cement hydration behavior is not yet well understood. Here, we report an in-situ synchrotron X-ray powder diffraction study for the first hours of hydration of BCSA cements. Rietveld quantitative phase analysis has been used to establish the degree of reaction (α). The hydration of a mixture of ye'elimite and gypsum revealed that ettringite formation (α ∼ 70% at 50 h) is limited by ye'elimite dissolution. Two laboratory-prepared BCSA cements were also studied: non-active-BCSA and active-BCSA cements, with β- and α′{sub H}-belite as main phases, respectively. Ye'elimite, in the non-active-BCSA system, dissolves at higher pace (αmore » ∼ 25% at 1 h) than in the active-BCSA one (α ∼ 10% at 1 h), with differences in the crystallization of ettringite (α ∼ 30% and α ∼ 5%, respectively). This behavior has strongly affected subsequent belite and ferrite reactivities, yielding stratlingite and other layered phases in non-active-BCSA. The dissolution and crystallization processes are reported and discussed in detail. -- Highlights: •Belite calcium sulfoaluminate cements early hydration mechanism has been determined. •Belite hydration strongly depends on availability of aluminum hydroxide. •Orthorhombic ye’elimite dissolved at a higher pace than cubic one. •Ye’elimite larger reaction degree yields stratlingite formation by belite reaction. •Rietveld method quantified gypsum, anhydrite and bassanite dissolution rates.« less
Polymorphism in two biologically active dihydropyrimidinium hydrochloride derivatives: quantitative inputs towards the energetics associated with crystal packing.

PubMed

Panini, Piyush; Venugopala, K N; Odhav, Bharti; Chopra, Deepak

2014-08-01

A new polymorph belonging to the tetrahydropyrimidinium class of compounds, namely 6-(4-chlorophenyl)-5-(methoxycarbonyl)-4-methyl-2-(3-(trifluoromethylthio)phenylamino)-3,6-dihydropyrimidin-1-ium chloride, and a hydrate of 2-(3-bromophenylamino)-6-(4-chlorophenyl)-5-(methoxycarbonyl)-4-methyl-3,6-dihydropyrimidin-1-ium chloride, have been isolated and characterized using single-crystal X-ray diffraction (XRD). A detailed comprehensive analysis of the crystal packing in terms of the associated intermolecular interactions and a quantification of their interaction energies have been performed for both forms of the two different organic salts (A and B) using X-ray crystallography and computational methods such as density functional theory (DFT) quantum mechanical calculations, PIXEL lattice-energy calculations (with decomposition of total lattice energy into the Coulombic, polarization, dispersion and repulsion contribution), the calculation of the Madelung constant (the EUGEN method), Hirshfeld and two-dimensional fingerprint plots. The presence of ionic [N-H](+)···Cl(-) and [C-H](+)···Cl(-) hydrogen bonds mainly stabilizes the crystal packing in both forms A and B, while in the case of B·H2O [N-H](+)···O(water) and O(water)-H···Cl(-) hydrogen bonds along with [N-H](+)···Cl(-) and [C-H](+)···Cl(-) provide stability to the crystal packing. The lattice-energy calculations from both PIXEL and EUGEN methods revealed that in the case of A, form (I) (monoclinic) is more stable whereas for B it is the anhydrous form that is more stable. The analysis of the `Madelung mode' of crystal packing of two forms of A and B and its hydrates suggest that differences exist in the position of the charged ions/atoms in the organic solid state. The R/E (distance-energy) plots for all the crystal structures show that the molecular pairs in their crystal packing are connected with either highly stabilizing (due to the presence of organic R(+) and Cl(-)) or highly destabilizing Coulombic contacts. The difference in crystal packing and associated intermolecular interactions between polymorphs (in the case of A) or the hydrates (in the case of B) have been clearly elucidated by the analysis of Hirshfeld surfaces and two-dimensional fingerprint plots. The relative contributions of the various interactions to the Hirshfeld surface for the cationic (dihydropyrimidinium) part and anionic (chloride ion) part for the two forms of A and B and its hydrate were observed to be different.
A synthesis, X-ray crystallographic and vibrational studies of guanidinium o-nitrobenzoate hydrate. New NLO crystal in guanidinium nitrobenzoate family

NASA Astrophysics Data System (ADS)

Drozd, Marek; Daszkiewicz, Marek

2018-06-01

According to literature data the two crystals are known: guanidinium m-nitrobenzoate and guanidinium p-nitrobenzoate. Both compounds belong to noncetrosymmetric crystallographic systems are consider as second order generators in nonlinear optic (NLO). For each of these crystals the detailed crystallographic, theoretical calculations and vibrational studies were performed. It is interesting that nitrobenzoic acid create tree variety of compounds ((2) ortho-, (3) meta- and (4) para-) what any data for third member of guanidinium nitrobenzoate crystal were not known. The guanidinium o-nitrobenzoate hydrate crystal was synthesized first time. The performed X-ray crystallographic study shown that crystal belongs to space group without macroscopic symmetry center. Additionally, the vibrational spectra (intensities, frequencies and PED analysis) of investigated compound are presented. These results are compared with theoretical calculations for equilibrium geometry and vibrational properties. Furthermore, the results of the theoretical approach include HOMO and LUMO energies and first order hyperpolarizability were obtained, also. On the basis of these data the crystal was classified as second order generator. All obtained results are compared with previous literature data of guanidinium m-nitrobenzoate and guanidinium p-nitrobenzoate compounds. Surprisingly, each of examined crystal belongs to different crystallographic system and shows different vibrational properties.
Growth of single crystals of organic salts with large second-order optical nonlinearities by solution processes for devices

NASA Technical Reports Server (NTRS)

Leslie, Thomas M.

1995-01-01

Data obtained from the electric field induced second harmonic generation (EFISH) and Kurtz Powder Methods will be provided to MSFC for further refinement of their method. A theoretical model for predicting the second-order nonlinearities of organic salts is being worked on. Another task is the synthesis of a number of salts with various counterions. Several salts with promising SHG activities and new salts will be tested for the presence of two crystalline forms. The materials will be recrystallized from dry and wet solvents and compared for SHG efficiency. Salts that have a high SHG efficiency and no tendency to form hydrates will be documented. The synthesis of these materials are included in this report. A third task involves method to aid in the growth of large, high quality single crystals by solution processes. These crystals will be characterized for their applicability in the fabrication of devices that will be incorporated into optical computers in future programs. Single crystals of optimum quality may be obtained by crystal growth in low-gravity. The final task is the design of a temperature lowering single crystal growth apparatus for ground based work. At least one prototype will be built.
Layered Structure and Swelling Behavior of a Multiple Hydrate-Forming Pharmaceutical Compound

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kiang, Y.; Xu, W; Stephens, P

2009-01-01

Investigation of one anhydrous and four hydrated forms of a pharmaceutical compound (1) using both single-crystal and high-resolution powder X-ray diffraction methods revealed a two-dimensional framework which, upon exposure to moisture, absorbed water between the layers, causing the lattice to expand by as much as 20% of the axial length along a. The single-crystal structure was solved and refined for the pentahydrate form in space group C2 with unit cell parameters a = 36.961(5) Angstroms, b = 7.458(2) Angstroms, c = 20.691(4) Angstroms, e = 99.461(1), and V = 5626(4) Angstroms3. In the single-crystal structure the water layers were parallelmore » to the bc plane and sandwiched by the crystalline compound 1 framework. Upon a change of relative humidity, water goes in and out of the interlayer space with the retention of the layer structure of the development compound. Starting from the anhydrous form, each additional water of hydration increased the interlayer spacing of the pharmaceutical solid by 1.3 Angstroms, half the size of a water molecule. In an exploratory formulation, this expansion of interlayer spacing caused tablets to crack upon storage at high relative humidity.« less
Effect of guest-host interaction on Raman spectrum of a CO2 clathrate hydrate single crystal

NASA Astrophysics Data System (ADS)

Ikeda, Tomoko; Mae, Shinji; Uchida, Tsutomu

1998-01-01

The polarized Raman spectra of an artificial CO2 clathrate hydrate single crystal have been measured in order to examine the crystal-orientation dependence of the Raman spectra. Since the crystal had crystallographic facets, the orientation of the crystal was determined by using the Miller indices of the facets. When the angle θ between the polarization plane of the incident laser beam and the direction of one of the <110> axes of the single crystal varied, it was observed that the intensities of the peaks, which were caused by the Fermi resonance of the symmetric stretching mode and the overtone of the bending mode of CO2, and the O-H symmetric stretching vibration mode, varied with θ. Since the tetrakaidecahedron cage in the CO2 clathrate hydrate is distorted along the <100> axis, the variations of the scattering intensities of the CO2 have been calculated by using a simple model that assumes that the CO2 rotates on the {100} plane in the tetrakaidecahedron cage. The results obtained from the experiments are consistent with the calculations made by using this model. It has been concluded that the anisotropy of the peak intensities of the CO2 show the influence of the cage geometry on the motion of the guest molecule. The anisotropy of the O-H symmetric stretching vibration mode was interpreted with a five-body structure model. As the calculation with the model was consistent with the result obtained from the experiment, it was found that the anisotropy of the peak intensity of the O-H symmetric stretching vibration mode was related to the arrangement of the water molecules. We consider that the result indicates the influence of the motion of the guest molecule on the surrounding hydrogen-bonded network.
The molecular and crystal structure of dextrans: a combined electron and X-ray diffraction study. II. A low temperature, hydrated polymorph.

PubMed

Guizard, C; Chanzy, H; Sarko, A

1985-06-05

The crystal and molecular structure of a dextran hydrate has been determined through combined electron and X-ray diffraction analysis, aided by stereochemical model refinement. A total of 65 hk0 electron diffraction intensities were measured on frozen single crystals held at the temperature of liquid nitrogen, to a resolution limit of 1.6 A. The X-ray intensities were measured from powder patterns recorded from collections of the single crystals. The structure crystallizes in a monoclinic unit cell with parameters a = 25.71 A, b = 10.21 A, c (chain axis) = 7.76 A and beta = 91.3 degrees. The space group is P2(1) with b axis unique. The unit cell contains six chains and eight water molecules, with three chains of the same polarity and four water molecules constituting the asymmetric unit. Along the chain direction the asymmetric unit is a dimer residue; however, the individual glucopyranose residues are very nearly related by a molecular 2-fold screw axis. The conformation of the chain is very similar to that in the anhydrous structure, but the chain packing differs in the two structures in that the rotational positions of the chains about the helix axes (the chain setting angles) are considerably different. The chains still pack in the form of sheets that are separated by water molecules. The difference in the chain setting angles between the anhydrous and hydrate structures corresponds to the angle between like unit cell axes observed in the diffraction diagrams recorded from hybrid crystals containing both polymorphs. Despite some beam damage effects, the structure was determined to a satisfactory degree of agreement, with the residuals R''(electron diffraction) = 0.258 and R(X-ray) = 0.127.
Observations of gas hydrates in marine sediments, offshore northern California

USGS Publications Warehouse

Brooks, J.M.; Field, M.E.; Kennicutt, M.C.

1991-01-01

Biogenic gas hydrates were recovered in shallow cores (< 6 m deep) from the Eel River basin in offshore northern California between 40??38??? and 40??56???N. The gas hydrates contained primarily methane (??13C = -57.6 to -69.1???) and occurred as dispersed crystals, small (2-20 mm) nodules, and layered bands within the sediment. These hydrates, recovered in sediment at water depths between 510 and 642 m, coincide nearly, but not exactly, with areas showing bottom-simulating reflectors (BSRs) on seismic-reflection records. This study confirms indirect geophysical and geologic observations that gas hydrates are present north of the Mendocino Fracture Zone in sediment of the Eel River basin but probably are absent to the south in the Point Arena basin. This discovery extends the confirmed sites of gas hydrates in the eastern Pacific region beyond the Peruvian and Central American margins to the northern California margin. ?? 1991.

Molecular dynamics study of structure H clathrate hydrates of methane and large guest molecules.

PubMed

Susilo, Robin; Alavi, Saman; Ripmeester, John A; Englezos, Peter

2008-05-21

Methane storage in structure H (sH) clathrate hydrates is attractive due to the relatively higher stability of sH as compared to structure I methane hydrate. The additional stability is gained without losing a significant amount of gas storage density as happens in the case of structure II (sII) methane clathrate. Our previous work has showed that the selection of a specific large molecule guest substance (LMGS) as the sH hydrate former is critical in obtaining the optimum conditions for crystallization kinetics, hydrate stability, and methane content. In this work, molecular dynamics simulations are employed to provide further insight regarding the dependence of methane occupancy on the type of the LMGS and pressure. Moreover, the preference of methane molecules to occupy the small (5(12)) or medium (4(3)5(6)6(3)) cages and the minimum cage occupancy required to maintain sH clathrate mechanical stability are examined. We found that thermodynamically, methane occupancy depends on pressure but not on the nature of the LMGS. The experimentally observed differences in methane occupancy for different LMGS may be attributed to the differences in crystallization kinetics and/or the nonequilibrium conditions during the formation. It is also predicted that full methane occupancies in both small and medium clathrate cages are preferred at higher pressures but these cages are not fully occupied at lower pressures. It was found that both small and medium cages are equally favored for occupancy by methane guests and at the same methane content, the system suffers a free energy penalty if only one type of cage is occupied. The simulations confirm the instability of the hydrate when the small and medium cages are empty. Hydrate decomposition was observed when less than 40% of the small and medium cages are occupied.
Stochastic Approach to Determine CO2 Hydrate Induction Time in Clay Mineral Suspensions

NASA Astrophysics Data System (ADS)

Lee, K.; Lee, S.; Lee, W.

2008-12-01

A large number of induction time data for carbon dioxide hydrate formation were obtained from a batch reactor consisting of four independent reaction cells. Using resistance temperature detector(RTD)s and a digital microscope, we successfully monitored the whole process of hydrate formation (i.e., nucleation and crystal growth) and detected the induction time. The experiments were carried out in kaolinite and montmorillonite suspensions at temperatures between 274 and 277 K and pressures ranging from 3.0 to 4.0 MPa. Each set of data was analyzed beforehand whether to be treated by stochastic manner or not. Geochemical factors potentially influencing the hydrate induction time under different experimental conditions were investigated by stochastic analyses. We observed that clay mineral type, pressure, and temperature significantly affect the stochastic behavior of the induction times for CO2 hydrate formation in this study. The hydrate formation kinetics along with stochastic analyses can provide basic understanding for CO2 hydrate storage in deep-sea sediment and geologic formation, securing its stability under the environments.
Electrodeposited non-stoichiometric tungstic acid for electrochromic applications: film growth modes, crystal structure, redox behavior and stability

NASA Astrophysics Data System (ADS)

Pugolovkin, Leonid V.; Cherstiouk, Olga V.; Plyasova, Lyudmila M.; Molina, Irina Yu.; Kardash, Tatyana Yu.; Stonkus, Olga A.; Yatsenko, Dmitriy A.; Kaichev, Vasily V.; Tsirlina, Galina A.

2016-12-01

Bath composition for cathodic electrodeposition of non-stoichiometric hydrated tungstic acid with high electrochromic efficiency is optimized with account for selective electroreduction of certain isopolytungstates. XRD data for thin electrodeposited films and chemically synthesized bulk tungstic acid dihydrate are compared in the context of reversible oxidation and reduction in hydrogen atmosphere, in presence of Pt catalyst. XPS and TEM techniques are attracted to understand the nature of reversible and less reversible transformations of films in the course of their storage and operation.
Controlled formation of cyclopentane hydrate suspensions via capillary-driven jet break-up

NASA Astrophysics Data System (ADS)

Geri, Michela; McKinley, Gareth

2017-11-01

Clathrate hydrates are crystalline compounds that form when a lattice of hydrogen-bonded water molecules is filled by guest molecules sequestered from an adjacent gas or liquid phase. Being able to rapidly produce and transport synthetic hydrates is of great interest given their significant potential as a clean energy source and safe option for hydrogen storage. We propose a new method to rapidly produce cyclopentane hydrate suspensions at ambient pressure with tunable particle size distribution by taking advantage of the Rayleigh-Plateau instability to form a mono-disperse stream of droplets during the controlled break-up of a water jet. The droplets are immediately frozen into ice particles through immersion in a subcooled reservoir and converted into hydrates with a dramatic reduction in the nucleation induction time. By measuring the evolution of the rheological properties with time, we monitor the process of hydrates formation via surface crystallization and agglomeration with different droplet size distributions. This new method enables us to gain new insights into hydrate formation and transport which was previously hindered by uncontrolled droplet formation and hydrate nucleation processes. MITei Chevron Fellowship.
Thermodynamic analysis of water molecules at the surface of proteins and applications to binding site prediction and characterization.

PubMed

Beuming, Thijs; Che, Ye; Abel, Robert; Kim, Byungchan; Shanmugasundaram, Veerabahu; Sherman, Woody

2012-03-01

Water plays an essential role in determining the structure and function of all biological systems. Recent methodological advances allow for an accurate and efficient estimation of the thermodynamic properties of water molecules at the surface of proteins. In this work, we characterize these thermodynamic properties and relate them to various structural and functional characteristics of the protein. We find that high-energy hydration sites often exist near protein motifs typically characterized as hydrophilic, such as backbone amide groups. We also find that waters around alpha helices and beta sheets tend to be less stable than waters around loops. Furthermore, we find no significant correlation between the hydration site-free energy and the solvent accessible surface area of the site. In addition, we find that the distribution of high-energy hydration sites on the protein surface can be used to identify the location of binding sites and that binding sites of druggable targets tend to have a greater density of thermodynamically unstable hydration sites. Using this information, we characterize the FKBP12 protein and show good agreement between fragment screening hit rates from NMR spectroscopy and hydration site energetics. Finally, we show that water molecules observed in crystal structures are less stable on average than bulk water as a consequence of the high degree of spatial localization, thereby resulting in a significant loss in entropy. These findings should help to better understand the characteristics of waters at the surface of proteins and are expected to lead to insights that can guide structure-based drug design efforts. Copyright © 2011 Wiley Periodicals, Inc.
Surfactant process for promoting gas hydrate formation and application of the same

DOEpatents

Rogers, Rudy E.; Zhong, Yu

2002-01-01

This invention relates to a method of storing gas using gas hydrates comprising forming gas hydrates in the presence of a water-surfactant solution that comprises water and surfactant. The addition of minor amounts of surfactant increases the gas hydrate formation rate, increases packing density of the solid hydrate mass and simplifies the formation-storage-decomposition process of gas hydrates. The minor amounts of surfactant also enhance the potential of gas hydrates for industrial storage applications.
Hydration water and bulk water in proteins have distinct properties in radial distributions calculated from 105 atomic resolution crystal structures.

PubMed

Chen, Xianfeng; Weber, Irene; Harrison, Robert W

2008-09-25

Water plays a critical role in the structure and function of proteins, although the experimental properties of water around protein structures are not well understood. The water can be classified by the separation from the protein surface into bulk water and hydration water. Hydration water interacts closely with the protein and contributes to protein folding, stability, and dynamics, as well as interacting with the bulk water. Water potential functions are often parametrized to fit bulk water properties because of the limited experimental data for hydration water. Therefore, the structural and energetic properties of the hydration water were assessed for 105 atomic resolution (
Magnetic Diagenesis in the Gas Hydrate System

NASA Astrophysics Data System (ADS)

Enkin, R. J.; Hamilton, T. S.; Esteban, L.

2009-05-01

Natural gas hydrate is a methane-bearing form of ice which occurs in permafrost and continental slope settings. Geochemical processes associated with gas hydrate formation lead to the growth of iron sulphides which have a geophysically measurable magnetic signature. Detailed magnetic investigation and complementary petrological observations were undertaken on unconsolidated sediments from three gas hydrate (GH) settings: permafrost in fluvial-deltaic silts and sands in the Western Canadian Arctic (Japex et al. Mallik 5L-38 in 2002); diamictons and hemipelagics in the Cascadia accretionary wedge west of Vancouver Island (IODP Exp.311 in 2006); and marine sands and hemipelagics from the Bay of Bengal (NGHP Exp.01 in 2007). These magnetic measurements provide stratigraphic profiles which reveal fine scale variations in lithology, magnetic grain size, and paleo-pore fluid geochemistry. The highest magnetic susceptibility values are observed in strata which preserve high initial concentrations of detrital magnetite, such as glacial deposits. The lowest values of magnetic susceptibility are observed where iron has been reduced to paramagnetic pyrite, formed in settings with high methane and sulphate flux such as at methane vents. Enhanced values of magnetic susceptibility characterize the introduction of the ferrimagnetic iron sulphide minerals greigite and smythite. These magnetic minerals are mostly found immediately adjacent to the sedimentary horizons which host the gas hydrate and their textures and compositions indicate rapid disequilibrium crystallization. The observed diagenesis result from the unique physical and geochemical properties of the environment where gas hydrates form: methane is available to fuel microbiological activity and the freezing which accompanied GH crystallization quickly removed pure water, froze the sediments into an impermeable solid and expelled more concentrated brines into the adjacent less permeable strata to the point of inducing fracture formation. Magnetic surveying techniques can help delineate anomalies related to gas hydrate deposits, and magnetic logging of wells and core samples provide information on the original lithology and diagenesis caused by gas hydrate formation.
Recovery of uranium from an irradiated solid target after removal of molybdenum-99 produced from the irradiated target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reilly, Sean Douglas; May, Iain; Copping, Roy

A process for minimizing waste and maximizing utilization of uranium involves recovering uranium from an irradiated solid target after separating the medical isotope product, molybdenum-99, produced from the irradiated target. The process includes irradiating a solid target comprising uranium to produce fission products comprising molybdenum-99, and thereafter dissolving the target and conditioning the solution to prepare an aqueous nitric acid solution containing irradiated uranium. The acidic solution is then contacted with a solid sorbent whereby molybdenum-99 remains adsorbed to the sorbent for subsequent recovery. The uranium passes through the sorbent. The concentrations of acid and uranium are then adjusted tomore » concentrations suitable for crystallization of uranyl nitrate hydrates. After inducing the crystallization, the uranyl nitrate hydrates are separated from a supernatant. The process results in the purification of uranyl nitrate hydrates from fission products and other contaminants. The uranium is therefore available for reuse, storage, or disposal.« less
Isotopic Zonation Within Sulfate Evaporite Mineral Crystals Reveal Quantitative Paleoenvironment Details

NASA Astrophysics Data System (ADS)

Coleman, M.; Rhorssen, M.; Mielke, R. E.

2008-12-01

Isotopic variations measured within a single crystal of hydrated magnesium sulfate are greater than 30 permil for delta 2-H, almost 10 permil for δ18O in water of hydration; and greater than 3 permil in sulfate oxygen. These results are interpreted to indicate the relative humidity of the system during evaporation (15 to 20 percent in this test case) and constrain the volume of water involved. The theoretical basis of this system is the isotopic fractionation between the species in solution and those precipitated as evaporite salts. Precipitation preferentially accumulates more of the heavy isotopes of sulfur and oxygen in mineral sulfate, relative to sulfate in solution. During the course of mineral growth this leads to successive depletion of the respective heavier isotopes in the residual brine reflected in a parallel trend in successive precipitates or even in successive zones within a single crystal. The change in isotopic composition at any one time during the process, relative to the initial value, can be described by an isotopic version of the Rayleigh Fractionation equation, depending only on the extent of the completion of the process and the relevant fractionation factor. Evaporation preferentially removes isotopically lighter hydrogen and oxygen leading to successive extents of enrichment in the respective heavier isotopes in the residual water. However, the relative effects on hydrogen and oxygen isotopes differs as function of relative humidity [1]. ALL OF THESE CHANGES ARE PRESERVED IN THE MINERAL ISOTOPE COMPOSITIONS. We precipitated barium sulfate from epsomite or gypsum samples, which was reduced at 1450°C in the presence of graphite and glassy carbon in a Finnigan TC/EA to produce CO for O isotopic analysis in a Finnigan 253 mass spectrometer, while a separate subsample was oxidized to SO2 in a Costech Elemental Analyzer. However, to make progress with this approach we needed to make a large number of measurements of hydration water and so we developed a new analytical method [2]. We use a modification of the standard TC/EA continuous-flow protocol to measure both hydrogen and oxygen of water of hydration from the same small sample. We have proved the concept of this new approach by analyzing zones within crystals and individual grains, growing epsomite (magnesium sulfate heptahydrate) in the laboratory and by analysis of natural gypsum evaporites. We are now exploring the effects of varying the controlling parameters. Eventual application to Martian sulfates will reveal amount of water involved in sulfate formation, its isotopic composition(s) and details of the paleo-atmospheric humidity. [1] Gat JR and Gonfiantini R, (Eds) (1981) IAEA Technical Report Series. [2] Rohrssen MK, Brunner B Mielke RE and Coleman M (2008) Analyt. Chem. (in press).
The impact of N,N-dimethyldodecylamine N-oxide (DDAO) concentration on the crystallisation of sodium dodecyl sulfate (SDS) systems and the resulting changes to crystal structure, shape and the kinetics of crystal growth.

PubMed

Summerton, Emily; Hollamby, Martin J; Zimbitas, Georgina; Snow, Tim; Smith, Andrew J; Sommertune, Jens; Bettiol, Jeanluc; Jones, Christopher; Britton, Melanie M; Bakalis, Serafim

2018-05-19

At low temperatures stability issues arise in commercial detergent products when surfactant crystallisation occurs, a process which is not currently well-understood. An understanding of the phase transition can be obtained using a simple binary SDS (sodium dodecyl sulfate) + DDAO (N,N-dimethyldodecylamine N-oxide) aqueous system. It expected that the crystallisation temperature of an SDS system can be lowered with addition of DDAO, thus providing a route to improve detergent stability. Detergent systems are typically comprised of anionic surfactants, non-ionic surfactants and water. This study explores the crystallisation of a three component system consisting of sodium dodecyl sulfate (SDS), N,N-dimethyldodecylamine N-oxide (DDAO), and water using wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC) and confocal Raman microscopy. The presence of DDAO lowered the crystallisation temperature of a 20 wt% SDS system. For all aqueous mixtures of SDS + DDAO at low temperatures, SDS hydrated crystals, SDS.1/2H 2 O or SDS·H 2 O, formed. SDS hydrates comprising of layers of SDS separated by water layers. DDAO tended to reside in the vicinity of these SDS crystals. In the absence of DDAO an additional intermediary hydrate structure, SDS.1/8H 2 O, formed whereas for mixed SDS + DDAO systems no such structure was detected during crystallisation. Copyright © 2018. Published by Elsevier Inc.
Adsorption Mechanism of Inhibitor and Guest Molecules on the Surface of Gas Hydrates.

PubMed

Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki

2015-09-23

The adsorption of guest and kinetic inhibitor molecules on the surface of methane hydrate is investigated by using molecular dynamics simulations. We calculate the free energy profile for transferring a solute molecule from bulk water to the hydrate surface for various molecules. Spherical solutes with a diameter of ∼0.5 nm are significantly stabilized at the hydrate surface, whereas smaller and larger solutes exhibit lower adsorption affinity than the solutes of intermediate size. The range of the attractive force is subnanoscale, implying that this force has no effect on the macroscopic mass transfer of guest molecules in crystal growth processes of gas hydrates. We also examine the adsorption mechanism of a kinetic hydrate inhibitor. It is found that a monomer of the kinetic hydrate inhibitor is strongly adsorbed on the hydrate surface. However, the hydrogen bonding between the amide group of the inhibitor and water molecules on the hydrate surface, which was believed to be the driving force for the adsorption, makes no contribution to the adsorption affinity. The preferential adsorption of both the kinetic inhibitor and the spherical molecules to the surface is mainly due to the entropic stabilization arising from the presence of cavities at the hydrate surface. The dependence of surface affinity on the size of adsorbed molecules is also explained by this mechanism.
Inhibition of the solid state transformation of carbamazepine in aqueous solution: impact of polymeric properties.

PubMed

Gift, Alan D; Hettenbaugh, Jacob A; Quandahl, Rachel A; Mapes, Madison

2017-11-06

The effects of polymers on the anhydrate-to-hydrate transformation of carbamazepine (CBZ) was investigated. The three types of polymers studied were polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA) and substituted celluloses which included hydroxypropyl methylcellulose (HPMC) and methylcellulose (MC). Anhydrous CBZ was added to dilute aqueous polymer solutions and Raman spectroscopy measurements were collected to monitor the kinetics of the solution-mediated transformation to CBZ dihydrate. Polymers exhibiting the greatest inhibition were able to reduce the growth phase of the solution-mediated transformation and change the habit of the hydrate crystal indicating polymer adsorption to the hydrate crystal surface as the mechanism of inhibition. The results of the various polymers showed that short chain substituted celluloses (HPMC and MC) inhibited the CBZ transformation to a much greater extent than longer chains. The same trend was observed for PVP and PVA, but to a lesser extent. These chain length effects were attributed to changes in polymer confirmation when adsorbed on the crystal surface. Additionally, decreasing the percentage of hydroxyl groups on the PVA polymer backbone reduced the ability of the polymer to inhibit the transformation and changing the degree of substitutions of methyl and hydroxypropyl groups on the cellulosic polymer backbone had no effect on the transformation.
Neutron powder diffraction studies as a function of temperature of structure II hydrate formed from propane

USGS Publications Warehouse

Rawn, C.J.; Rondinone, A.J.; Chakoumakos, B.C.; Circone, S.; Stern, L.A.; Kirby, S.H.; Ishii, Y.

2003-01-01

Neutron powder diffraction data confirm that hydrate samples synthesized with propane crystallize as structure type II hydrate. The structure has been modeled using rigid-body constraints to describe C3H8 molecules located in the eight larger polyhedral cavities of a deuterated host lattice. Data were collected at 12, 40, 100, 130, 160, 190, 220, and 250 K and used to calculate the thermal expansivity from the temperature dependence of the lattice parameters. The data collected allowed for full structural refinement of atomic coordinates and the atomic-displacement parameters.
Polarized optical absorption and photoluminescence measurements in single-crystal thin films of 4'-dimethylamino-N-methyl-4-stilbazolium tosylate

NASA Astrophysics Data System (ADS)

Bhowmik, Achintya K.; Xu, Jianjun; Thakur, Mrinal

1999-11-01

Single-crystal thin films of the anhydrous (red) and the hydrated (orange) phases of the organic salt 4'-dimethylamino-N-methyl-4-stilbazolium tosylate were grown by a modification of the shear method. The optical absorption coefficients of the films were measured with light polarized along and normal to the dipole/molecular axis at both resonant and off-resonant wavelengths, and a strong dichroism was observed at the resonant wavelengths. The absorption measurements are important considering potential applications of these films (red phase) in high-speed single-pass thin-film electro-optic modulators [M. Thakur, J. Xu, A. Bhowmik, and L. Zhou, Appl. Phys. Lett. 74, 635 (1999)] and other photonic devices. Highly polarized photoluminescence (PL) has been observed in these films. The PL efficiencies of the red- and orange-phase single-crystal films were measured to be about 12% and 14%, respectively, which are significantly higher than the maximum PL efficiency measured in solution (3%).
Enhanced Hydrate Nucleation Near the Limit of Stability.

PubMed

Jimenez-Angeles, Felipe; Firoozabadi, Abbas

2015-03-30

Clathrate hydrates are crystalline structures composed of small guest molecules trapped into cages formed by hydrogen-bonded water molecules. In hydrate nucleation, water and the guest molecules may stay in a metastable fluid mixture for a long period. Metastability is broken if the concentration of the guest is above certain limit. We perform molecular dynamics (MD) simulations of supersaturated water-propane solutions close to the limit of stability. We show that hydrate nucleation can be very fast in a very narrow range of composition at moderate temperatures. Propane density fluctuations near the fluid-fluid demixing are coupled with crystallization producing en- hanced nucleation rates. This is the first report of propane-hydrate nucleation by MD simulations. We observe motifs of the crystalline structure II in line with experiments and new hydrate cages not reported in the literature. Our study relates nucleation to the fluid-fluid spinodal decomposition and demonstration that the enhanced nucleation phenomenon is more general than short range attractive interactions as suggested in nucleation of proteins.
The effect of gyrolite additive on the hydration properties of Portland cement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eisinas, A., E-mail: anatolijus.eisinas@ktu.lt; Baltakys, K.; Siauciunas, R.

2012-01-15

The influence of gyrolite additive on the hydration properties of ordinary Portland cement was examined. It was found that the additive of synthetic gyrolite accelerates the early stage of hydration of OPC. This compound binds alkaline ions and serves as a nucleation site for the formation of hydration products (stage I). Later on, the crystal lattice of gyrolite becomes unstable and turns into C-S-H, with higher basicity (C/S {approx} 0.8). This recrystallization process is associated with the consumption of energy (the heat of reaction) and with a decrease in the rate of heat evolution of the second exothermic reaction (stagemore » II). The experimental data and theoretical hypothesis were also confirmed by thermodynamic and the apparent kinetic parameters of the reaction rate of C{sub 3}S hydration calculations. The changes occur in the early stage of hydration of OPC samples and do not have a significant effect on the properties of cement stone.« less
[In situ Raman spectroscopic observation of micro-processes of methane hydrate formation and dissociation].

PubMed

Liu, Chang-Ling; Ye, Yu-Guang; Meng, Qing-Guo; Lü, Wan-Jun; Wang, Fei-Fei

2011-06-01

Micro laser Raman spectroscopic technique was used for in situ observation of the micro-processes of methane hydrate formed and decomposed in a high pressure transparent capillary. The changes in clathrate structure of methane hydrate were investigated during these processes. The results show that, during hydrate formation, the Raman peak (2 917 cm(-1)) of methane gas gradually splits into two peaks (2 905 and 2 915 cm(-1)) representing large and small cages, respectively, suggesting that the dissolved methane molecules go into two different chemical environments. In the meantime, the hydrogen bonds interaction is strengthened because water is changing from liquid to solid state gradually. As a result, the O-H stretching vibrations of water shift to lower wavenumber. During the decomposition process of methane hydrates, the Raman peaks of the methane molecules both in the large and small cages gradually clear up, and finally turn into a single peak of methane gas. The experimental results show that laser Raman spectroscopy can accurately demonstrate some relevant information of hydrate crystal structure changes during the formation and dissociation processes of methane hydrate.
Applications for special-purpose minerals at a lunar base

NASA Technical Reports Server (NTRS)

Ming, Douglas W.

1992-01-01

Maintaining a colony on the Moon will require the use of lunar resources to reduce the number of launches necessary to transport goods from the Earth. It may be possible to alter lunar materials to produce minerals or other materials that can be used for applications in life support systems at a lunar base. For example, mild hydrothermal alteration of lunar basaltic glasses can produce special-purpose minerals (e.g., zeolites, smectites, and tobermorites) that in turn may be used in life support, construction, waste renovation, and chemical processes. Zeolites, smectites, and tobermorites have a number of potential applications at a lunar base. Zeolites are hydrated aluminosilicates of alkali and alkaline earth cations that possess infinite, three-dimensional crystal structures. They are further characterized by an ability to hydrate and dehydrate reversibly and to exchange some of their constituent cations, both without major change of structure. Based on their unique absorption, cation exchange, molecular sieving, and catalytic properties, zeolites may be used as a solid support medium for the growth of plants, as an adsorption medium for separation of various gases (e.g., N2 from O2), as catalysts, as molecular sieves, and as a cation exchanger in sewage-effluent treatment, in radioactive waste disposal, and in pollution control. Smectites are crystalline, hydrated 2:1 layered aluminosilicates that also have the ability to exchange some of their constituent cations. Like zeolites, smectites may be used as an adsorption medium for waste renovation, as adsorption sites for important essential plant growth cations in solid support plant growth mediums (i.e., 'soils'), as cation exchangers, and in other important application. Tobermorites are cystalline, hydrated single-chained layered silicates that have cation-exchange and selectivity properties between those of smectites and most zeolites. Tobermorites may be used as a cement in building lunar base structures, as catalysts, as media for nuclear and hazardous waste disposal, as exchange media for waste-water treatment, and in other potential applications. Special-purpose minerals synthesized at a lunar base may also have important applications at a space station and for other planetary missions. New technologies will be required at a lunar base to develop life support systems that are self-sufficient, and the use of special-purpose minerals may help achieve this self-sufficiency.
Gas hydrate in seafloor sediments: Impact on future resources and drilling safety

USGS Publications Warehouse

Dillon, William P.; Max, Michael D.

2001-01-01

Gas hydrate concentrates methane and sometimes other gases in its crystal lattice and this gas can be released intentionally creating a resource or escape accidentally forming a hazard. The densest accumulations of gas hydrate tend to occur at sites where the base of the gas hydrate stability zone (commonly the upper several hundred m of the sedimentary section) is configured to trap gas, often as a broad arch. The gas may rise from below or form by bacterial activity at shallow depth, but gas commonly is concentrated near the base of the gas hydrate stability zone by recycling. This gas accumulates in presumably leaky traps, then enriches the hydrate above as it migrates upward by diffusion, fluid movement through sedimentary pores, or flow along fracture channelways. Analysis of seismic reflection profiles is beginning to identify such concentrations and the circumstances that create them. The first attempt to explore for gas hydrate off Japan by the Japanese National Oil Corporation produced quite favorable results, showing high gas hydrate contents in permeable sediments. Gas hydrate dissociation can be a safety concern in drilling and production. The volume of water and gas released in dissociation is often greater than the volume of the hydrate, so overpressures can be created. Furthermore, the gas hydrate can provide shallow seals, so the possibility of high-pressure flows or generation of slides is apparent.

General synthesis and structural evolution of a layered family of Ln8(OH)20Cl4 x nH2O (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Y).

PubMed

Geng, Fengxia; Matsushita, Yoshitaka; Ma, Renzhi; Xin, Hao; Tanaka, Masahiko; Izumi, Fujio; Iyi, Nobuo; Sasaki, Takayoshi

2008-12-03

The synthesis process and crystal structure evolution for a family of stoichiometric layered rare-earth hydroxides with general formula Ln(8)(OH)(20)Cl(4) x nH(2)O (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Y; n approximately 6-7) are described. Synthesis was accomplished through homogeneous precipitation of LnCl(3) x xH(2)O with hexamethylenetetramine to yield a single-phase product for Sm-Er and Y. Some minor coexisting phases were observed for Nd(3+) and Tm(3+), indicating a size limit for this layered series. Light lanthanides (Nd, Sm, Eu) crystallized into rectangular platelets, whereas platelets of heavy lanthanides from Gd tended to be of quasi-hexagonal morphology. Rietveld profile analysis revealed that all phases were isostructural in an orthorhombic layered structure featuring a positively charged layer, [Ln(8)(OH)(20)(H(2)O)(n)](4+), and interlayer charge-balancing Cl(-) ions. In-plane lattice parameters a and b decreased nearly linearly with a decrease in the rare-earth cation size. The interlamellar distance, c, was almost constant (approximately 8.70 A) for rare-earth elements Nd(3+), Sm(3+), and Eu(3+), but it suddenly decreased to approximately 8.45 A for Tb(3+), Dy(3+), Ho(3+), and Er(3+), which can be ascribed to two different degrees of hydration. Nd(3+) typically adopted a phase with high hydration, whereas a low-hydration phase was preferred for Tb(3+), Dy(3+), Ho(3+), Er(3+), and Tm(3+). Sm(3+), Eu(3+), and Gd(3+) samples were sensitive to humidity conditions because high- and low-hydration phases were interconvertible at a critical humidity of 10%, 20%, and 50%, respectively, as supported by both X-ray diffraction and gravimetry as a function of the relative humidity. In the phase conversion process, interlayer expansion or contraction of approximately 0.2 A also occurred as a possible consequence of absorption/desorption of H(2)O molecules. The hydration difference was also evidenced by refinement results. The number of coordinated water molecules per formula weight, n, changed from 6.6 for the high-hydration Gd sample to 6.0 for the low-hydration Gd sample. Also, the hydration number usually decreased with increasing atomic number; e.g., n = 7.4, 6.3, 7.2, and 6.6 for high-hydration Nd, Sm, Eu, and Gd, and n = 6.0, 5.8, 5.6, 5.4, and 4.9 for low-hydration Gd, Tb, Dy, Ho, and Er. The variation in the average Ln-O bond length with decreasing size of the lanthanide ions is also discussed. This family of layered lanthanide compounds highlights a novel chemistry of interplay between crystal structure stability and coordination geometry with water molecules.
Influence of sodium borate on the early age hydration of calcium sulfoaluminate cement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Champenois, Jean-Baptiste; Dhoury, Mélanie; Cau Dit Coumes, Céline, E-mail: celine.cau-dit-coumes@cea.fr

Calcium sulfoaluminate (CSA) cements are potential candidates for the conditioning of radioactive wastes with high sodium borate concentrations. This work thus investigates early age hydration of two CSA cements with different gypsum contents (0 to 20%) as a function of the mixing solution composition (borate and NaOH concentrations). Gypsum plays a key role in controlling the reactivity of cement. When the mixing solution is pure water, increasing the gypsum concentration accelerates cement hydration. However, the reverse is observed when the mixing solution contains sodium borate. Until gypsum exhaustion, the pore solution pH remains constant at ~ 10.8, and a poorlymore » crystallized borate compound (ulexite) precipitates. A correlation is established between this transient precipitation and the hydration delay. Decreasing the gypsum content in the binder, or increasing the sodium content in the mixing solution, are two ways of reducing the stability of ulexite, thus decreasing the hydration delay.« less
Entrapment of Hydrate-coated Gas Bubbles into Oil and Separation of Gas and Hydrate-film; Seafloor Experiments with ROV

NASA Astrophysics Data System (ADS)

Hiruta, A.; Matsumoto, R.

2015-12-01

We trapped gas bubbles emitted from the seafloor into oil-containing collector and observed an unique phenomena. Gas hydrate formation needs water for the crystal lattice; however, gas hydrates in some areas are associated with hydrophobic crude oil or asphalt. In order to understand gas hydrate growth in oil-bearing sediments, an experiment with cooking oil was made at gas hydrate stability condition. We collected venting gas bubbles into a collector with canola oil during ROV survey at a gas hydrate area in the eastern margin of the Sea of Japan. When the gas bubbles were trapped into collector with oil, gas phase appeared above the oil and gas hydrates, between oil and gas phase. At this study area within gas hydrate stability condition, control experiment with oil-free collector suggested that gas bubbles emitted from the seafloor were quickly covered with gas hydrate film. Therefore it is improbable that gas bubbles entered into the oil phase before hydrate skin formation. After the gas phase formation in oil-containing collector, the ROV floated outside of hydrate stability condition for gas hydrate dissociation and re-dived to the venting site. During the re-dive within hydrate stability condition, gas hydrate was not formed. The result suggests that moisture in the oil is not enough for hydrate formation. Therefore gas hydrates that appeared at the oil/gas phase boundary were already formed before bubbles enter into the oil. Hydrate film is the only possible origin. This observation suggests that hydrate film coating gas hydrate was broken at the sea water/oil boundary or inside oil. Further experiments may contribute for revealing kinetics of hydrate film and formation. This work was a part of METI (Ministry of Economy, Trade and Industry)'s project entitled "FY2014 Promoting research and development of methane hydrate". We also appreciate support of AIST (National Institute of Advanced Industrial Science and Technology).
Changes in the solid state of anhydrous and hydrated forms of sodium naproxen under different grinding and environmental conditions: Evidence of the formation of new hydrated forms.

PubMed

Censi, Roberta; Rascioni, Riccardo; Di Martino, Piera

2015-05-01

The aim of the present work was to investigate the solid state change of the anhydrous and hydrate solid forms of sodium naproxen under different grinding and environmental conditions. Grinding was carried out manually in a mortar under the following conditions: at room temperature under air atmosphere (Method A), in the presence of liquid nitrogen under air atmosphere (Method B), at room temperature under nitrogen atmosphere (Method C), and in the presence of liquid nitrogen under nitrogen atmosphere (Method D). Among the hydrates, the following forms were used: a dihydrate form (DSN) obtained by exposing the anhydrous form at 55% RH; a dihydrate form (CSN) obtained by crystallizing sodium naproxen from water; the tetrahydrate form (TSN) obtained by exposing the anhydrous form at 75% RH. The metastable monohydrate form (MSN), previously described in the literature, was not used because of its high physical instability. The chemical stability during grinding was firstly assessed and proven by HPLC. Modification of the particle size and shape, and changes in the solid state under different grinding methods were evaluated by scanning electron microscopy, and X-ray powder diffractometry and thermogravimetry, respectively. The study demonstrated the strong influence of starting form, grinding and environmental conditions on particle size, shape and solid state of recovered sodium naproxen forms. In particular, it was demonstrated that in the absence of liquid nitrogen (Methods A and C), either at air or at nitrogen atmosphere, the monohydrate form (MSN) was obtained from any hydrates, meaning that these grinding conditions favored the dehydration of superior hydrates. The grinding process carried out in the presence of liquid nitrogen (Method B) led to further hydration of the starting materials: new hydrate forms were identified as one pentahydrate form and one hexahydrate form. The hydration was caused by the condensation of the atmospheric water on sodium naproxen particles by liquid nitrogen and by the grinding forces that created a close contact between water and drug. The simultaneous disruption of the crystals, occurring during grinding, and their close contact with water molecules promoted the conversion in higher hydrates. Under the Method D, it was possible to highlight a certain tendency to hydration probably due to a rearrangement of water already present into the hydrates, but results were substantially different from Method B. Thus, summarizing, the different SN forms behave differently under different grinding and environmental conditions. Copyright © 2015 Elsevier B.V. All rights reserved.
Molecular Dynamics Simulation of the Crystal Nucleation and Growth Behavior of Methane Hydrate in the Presence of the Surface and Nanopores of Porous Sediment.

PubMed

Yan, Ke-Feng; Li, Xiao-Sen; Chen, Zhao-Yang; Xia, Zhi-Ming; Xu, Chun-Gang; Zhang, Zhiqiang

2016-08-09

The behavior of hydrate formation in porous sediment has been widely studied because of its importance in the investigation of reservoirs and in the drilling of natural gas hydrate. However, it is difficult to understand the hydrate nucleation and growth mechanism on the surface and in the nanopores of porous media by experimental and numerical simulation methods. In this work, molecular dynamics simulations of the nucleation and growth of CH4 hydrate in the presence of the surface and nanopores of clay are carried out. The molecular configurations and microstructure properties are analyzed for systems containing one H2O hydrate layer (System A), three H2O hydrate layers (System B), and six H2O hydrate layers (System C) in both clay and the bulk solution. It is found that hydrate formation is more complex in porous media than in the pure bulk solution and that there is cooperativity between hydrate growth and molecular diffusion in clay nanopores. The hydroxylated edge sites of the clay surface could serve as a source of CH4 molecules to facilitate hydrate nucleation. The diffusion velocity of molecules is influenced by the growth of the hydrate that forms a block in the throats of the clay nanopore. Comparing hydrate growth in different clay pore sizes reveals that the pore size plays an important role in hydrate growth and molecular diffusion in clay. This simulation study provides the microscopic mechanism of hydrate nucleation and growth in porous media, which can be favorable for the investigation of the formation of natural gas hydrate in sediments.
Shape Recovery with Concomitant Mechanical Strengthening of Amphiphilic Shape Memory Polymers in Warm Water

DOE PAGES

Zhang, Ben; DeBartolo, Janae E.; Song, Jie

2017-01-26

Maintaining adequate or enhancing mechanical properties of shape memory polymers (SMPs) after shape recovery in an aqueous environment are greatly desired for biomedical applications of SMPs as self-fitting tissue scaffolds or minimally invasive surgical implants. Here we report stable temporary shape fixing and facile shape recovery of biodegradable triblock amphiphilic SMPs containing a poly(ethylene glycol) (PEG) center block and flanking poly(lactic acid) or poly(lactic-co-glycolic acid) blocks in warm water, accompanied with concomitant enhanced mechanical strengths. Differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WXRD) and small-angle X-ray scattering (SAXS) analyses revealed that the unique stiffening of the amphiphilic SMPs upon hydrationmore » was due to hydration-driven microphase separation and PEG crystallization. We further demonstrated that the chemical composition of degradable blocks in these SMPs could be tailored to affect the persistence of hydration-induced stiffening upon subsequent dehydration. These properties combined open new horizons for these amphiphilic SMPs for smart weight-bearing in vivo applications (e.g. as self-fitting intervertebral discs). In conclusion, this study also provides a new material design strategy to strengthen polymers in aqueous environment in general.« less
Crystal structure of 8-hy-droxy-quinolin-ium 2-carboxy-6-nitro-benzoate mono-hydrate.

PubMed

Divya Bharathi, M; Ahila, G; Mohana, J; Chakkaravarthi, G; Anbalagan, G

2015-04-01

In the title hydrated salt, C9H8NO(+)·C8H4NO6 (-)·H2O, the deprotonated carboxyl-ate group is almost normal to its attached benzene ring [dihedral angle = 83.56 (8)°], whereas the protonated carboxyl-ate group is close to parallel [dihedral angle = 24.56 (9)°]. In the crystal, the components are linked by N-H⋯O and O-H⋯O hydrogen bonds, generating [001] chains. The packing is consolidated by C-H⋯O and π-π [centroid-to-centroid distances = 3.6408 (9) and 3.6507 (9) Å] inter-actions, which result in a three-dimensional network.
The betainic form of (imidazol-2-yl)phenylphosphinic acid hydrate

PubMed Central

Kunz, Peter C.; Frank, Walter

2010-01-01

Single crystals of the title compound, (imidazolium-2-yl)phenylphosphinate monohydrate, C9H9N2O2·H2O, were obtained from methanol/water after deprotection and oxidation of bis(1-diethoxymethylimidazol-2-yl)phenylphosphane. In the structure, several N–H⋯O and P—O⋯H–O hydrogen bonds are found. π–π interactions between the protonated imidazolyl rings [centroid–centroid distance = 3.977 (2) Å] help to establish the crystal packing. The hydrate water molecule builds hydrogen bridges to three molecules of the phosphinic acid by the O and both H atoms. PMID:21579513
Gas Hydrates as a CH4 Source and a CO2 Sink: New Approaches Based on Fundamental Research

NASA Astrophysics Data System (ADS)

Schicks, J. M.; Spangenberg, E.; Erzinger, J.

2007-12-01

The huge amount of methane, stored in the gas hydrate reservoirs of the world suggests that natural gas hydrates may be used in the future as a source of energy. A first production test was performed during the Mallik 2002 Gas Hydrate Production Research Well Program, showing that the thermal stimulation of natural gas hydrates successfully results in methane production (Dallimore et al. 2005). However, regarding the energy balance, the most efficient method for methane production from hydrates still needs to be developed. From another point of view, the sequestration of CO2 in form of gas hydrates in (marine) sediments is an interesting idea. A combination of methane production from natural gas hydrates on the one hand and CO2 - sequestration on the other hand seems to be an obvious and ideal solution. Different studies on possible methods - e.g. the exchange of CH4 with CO2 in gas hydrates (Lee et al, 2003, Graue and Kvamme, 2006) - have been published recently and demonstrated that this could be a possible way, in principle. Our own investigations on the exchange of CH4 with gaseous CO2 showed that this reaction is much too slow and inefficient to be a reasonable approach. The exchange of only 20 percent CH4 with CO2 could be detected in stable structure I hydrate crystals after 120 hours. In addition, multicomponent hydrates containing higher hydrocarbons beside methane tend to be more stable than pure methane hydrates (Schicks et al, 2006). Therefore, the application of an additional and controlled method for CH4 -hydrate destabilization seems to be necessary and might lead to an efficient release of CH4 from and CO2 inclusion into hydrates. In any case, the question of process optimization still remains. In this contribution the chances and challenges of a combination of these two processes based on experimental data will be examined. Different kinds of experiments have been performed on natural marine and permafrost gas hydrates and synthesized clathrate hydrates: Differential scanning calorimetric measurements for the determination of the specific enthalpy of dissociation, determination of stability fields for pure and multicomponent systems, CH4 - CO2 -exchange reaction in clathrate hydrates and CO2 -hydrate formation in sediments under different pressure and temperature conditions were studied. Based on these fundamental data, new concepts for methane production and combined CO2 - sequestration will be presented and discussed. Reference: S.R. Dallimore, T.S. Collet (Eds.), 2005. Scientific Results from the Mallik 2002 Gas Hydrate Production Research Well Program, Mackenzie Delta, Northwest Territories, Canada, Geological Survey of Canada, WO H. Lee, Y. Seo, Y.-T. Seo, I.L. Moudrakovski, J.A. Ripmeester, 2003. Angewandte Chemie International Edition, 42, 5049-5051 A. Graue, B. Kvamme, 2006. Conference Paper presented at the Offshore Technology Conference in Houston, Texas, U.S.A., 1-4 May 2006 J.M. Schicks, R. Naumann, J. Erzinger, K.C. Hester, Caroly A. Koh, E.D. Sloan, 2006. Journal of Physical Chemistry, 110, 11468-11474
Investigations on structural and photoluminescence mechanism of cerium doped L-Histidine hydrochloride mono hydrate single crystals for optical applications

NASA Astrophysics Data System (ADS)

Rajyalakshmi, S.; Ramachandra Rao, K.; Brahmaji, B.; Samatha, K.; Visweswara Rao, T. K.; Ramakrishna, Y.

2017-02-01

Semi organic nonlinear optical material of Ce3+ ion added L-Histidine hydrochloride monohydrate (LHHC) crystals have been grown successfully by the slow evaporation solution technique (SEST) as well as Sankaranarayanan-Ramasamy (SR) technique. Unit cell data have been measured from the single crystal X-ray diffraction analysis and High resolution X-ray diffraction analysis (HRXRD) study shows relatively a good crystalline perfection. Fourier transform infra-red spectroscopy (FTIR) spectra indicates that the Ce3+ ion is coordinated with carboxylate group of grown crystal. The lower UV-cutoff wavelength of the incorporation of Ce3+ ion in LHHC is 240 nm. The incorporation of Ce3+ ion in the crystal lattice was observed by energy dispersive X-ray analysis (EDAX). The nonlinear optical (NLO) efficiency of SR-grown crystal is 3.7 times greater with respect to potassium dihydrogen phosphate (KDP). We report first-time the photoluminescence (PL) mechanism of emission spectrum, which shows broad band located at 350 nm corresponding to 5d → 4f transition of Ce3+ ion and excited by 250 nm wavelength. The excitation spectrum shows a band at 258 nm due to the 4f → 5d transition of Ce3+ ion. The nature of decay curve of the grown crystal is bi-exponential with a long life time of τ2 is 8.8270 μs.
Bio-inspired nitrile hydration by peptidic ligands based on L-cysteine, L-methionine or L-penicillamine and pyridine-2,6-dicarboxylic acid.

PubMed

Byrne, Cillian; Houlihan, Kate M; Devi, Prarthana; Jensen, Paul; Rutledge, Peter J

2014-12-12

Nitrile hydratase (NHase, EC 4.2.1.84) is a metalloenzyme which catalyses the conversion of nitriles to amides. The high efficiency and broad substrate range of NHase have led to the successful application of this enzyme as a biocatalyst in the industrial syntheses of acrylamide and nicotinamide and in the bioremediation of nitrile waste. Crystal structures of both cobalt(III)- and iron(III)-dependent NHases reveal an unusual metal binding motif made up from six sequential amino acids and comprising two amide nitrogens from the peptide backbone and three cysteine-derived sulfur ligands, each at a different oxidation state (thiolate, sulfenate and sulfinate). Based on the active site geometry revealed by these crystal structures, we have designed a series of small-molecule ligands which integrate essential features of the NHase metal binding motif into a readily accessible peptide environment. We report the synthesis of ligands based on a pyridine-2,6-dicarboxylic acid scaffold and L-cysteine, L-S-methylcysteine, L-methionine or L-penicillamine. These ligands have been combined with cobalt(III) and iron(III) and tested as catalysts for biomimetic nitrile hydration. The highest levels of activity are observed with the L-penicillamine ligand which, in combination with cobalt(III), converts acetonitrile to acetamide at 1.25 turnovers and benzonitrile to benzamide at 1.20 turnovers.
A molecular dynamics study of model SI clathrate hydrates: the effect of guest size and guest-water interaction on decomposition kinetics.

PubMed

Das, Subhadip; Baghel, Vikesh Singh; Roy, Sudip; Kumar, Rajnish

2015-04-14

One of the options suggested for methane recovery from natural gas hydrates is molecular replacement of methane by suitable guests like CO2 and N2. This approach has been found to be feasible through many experimental and molecular dynamics simulation studies. However, the long term stability of the resultant hydrate needs to be evaluated; the decomposition rate of these hydrates is expected to depend on the interaction between these guest and water molecules. In this work, molecular dynamics simulation has been performed to illustrate the effect of guest molecules with different sizes and interaction strengths with water on structure I (SI) hydrate decomposition and hence the stability. The van der Waals interaction between water of hydrate cages and guest molecules is defined by Lennard Jones potential parameters. A wide range of parameter spaces has been scanned by changing the guest molecules in the SI hydrate, which acts as a model gas for occupying the small and large cages of the SI hydrate. All atomistic simulation results show that the stability of the hydrate is sensitive to the size and interaction of the guest molecules with hydrate water. The increase in the interaction of guest molecules with water stabilizes the hydrate, which in turn shows a slower rate of hydrate decomposition. Similarly guest molecules with a reasonably small (similar to Helium) or large size increase the decomposition rate. The results were also analyzed by calculating the structural order parameter to understand the dynamics of crystal structure and correlated with the release rate of guest molecules from the solid hydrate phase. The results have been explained based on the calculation of potential energies felt by guest molecules in amorphous water, hydrate bulk and hydrate-water interface regions.
How the 410-km Discontinuity Reflects Mantle Water Content: Constraints from High-Pressure Experiments on Wadsleyite Single-Crystal Elasticity

NASA Astrophysics Data System (ADS)

Buchen, J.; Marquardt, H.; Boffa Ballaran, T.; Kawazoe, T.; Speziale, S.; Kurnosov, A.

2017-12-01

The olivine-wadsleyite phase transition gives rise to a seismic discontinuity at 410 km depth. By incorporating hydroxyl groups in its crystal structure, wadsleyite can store large amounts of water in the shallow transition zone. The velocity contrast across the 410-km seismic discontinuity has been widely used to deduce mantle mineralogy including estimates of the water content at depth. To interpret seismic observations in terms of mantle mineralogy and deep water cycling, the elastic properties of wadsleyite need to be determined at relevant pressures and temperatures. We performed simultaneous sound wave velocity and density measurements on iron-bearing wadsleyite single crystals at high pressures and first experiments at combined high pressures and high temperatures. When compared with previous work on hydrous iron-bearing wadsleyite with identical Fe/(Mg+Fe) ratio of 0.11, our results show that hydration of iron-bearing wadsleyite reduces the sound wave velocities at low pressures. At high pressures, in contrast, P-wave and S-wave velocities of hydrous and anhydrous iron-bearing wadsleyite cross over and become seismically indistinguishable at conditions of the transition zone. As a consequence, hydrated regions in the shallow transition zone cannot be detected by seismic tomography. Motivated by our experimental results, we modeled velocity, density, and acoustic impedance contrasts across the 410-km seismic discontinuity and found velocity contrasts to vary only slightly with hydration. Instead, we show that the impedance contrast caused by the olivine-wadsleyite phase transition and hence the reflectivity of the 410-km seismic discontinuity are more sensitive to hydration. Our findings give important constraints on the interpretation of seismic observations aiming to trace Earth's deep water cycle.
Thermal conductivity of hydrate-bearing sediments

USGS Publications Warehouse

Cortes, Douglas D.; Martin, Ana I.; Yun, Tae Sup; Francisca, Franco M.; Santamarina, J. Carlos; Ruppel, Carolyn D.

2009-01-01

A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate–saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate–bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces.
Crystal structure of carnidazole form II from synchrotron X-ray powder diffraction: structural comparison with form I, the hydrated form and the low energy conformations in vacuo.

PubMed

de Armas, Héctor Novoa; Peeters, Oswald M; Blaton, Norbert; Van den Mooter, Guy; De Ridder, Dirk J A; Schenk, Henk

2006-10-01

The crystal structure of carnidazole form II, O-methyl [2-(2-methyl-5-nitro-1H-imidazole-1-yl)ethyl]thiocarbamate, has been determined using synchrotron X-ray powder diffraction in combination with simulated annealing and whole profile pattern matching, and refined by the Rietveld method. For structure solution, 12 degrees of freedom were defined: one motion group and six torsions. Form II crystallizes in space group P2(1)/n, Z=4, with unit cell parameters after Rietveld refinement: a=13.915(4), b=8.095(2), c=10.649(3) A, beta=110.83(1) degrees, and V=1121.1(5) A3. The two polymorphic forms, as well as the hydrate, crystallize in the monoclinic space group P2(1)/n having four molecules in the cell. In form II, the molecules are held together by forming two infinite zig-zag chains via hydrogen bonds of the type N--H...N, the same pattern as in form I. A conformational study of carnidazole, at semiempirical PM3 level, was performed using stochastic approaches based on modification of the flexible torsion angles. The values of the torsion angles for the molecules of the two polymorphic forms and the hydrate of carnidazole are compared to those obtained from the conformational search. Form I and form II are enantiotropic polymorphic pairs this agrees with the fact that the two forms are conformational polymorphs. Copyright (c) 2006 Wiley-Liss, Inc. and the American Pharmacists Association
Comparison of skin hydration in combination and single use of common moisturizers (cream, toner, and spray water).

PubMed

Yuanxi, Li; Wei, Hua; Lidan, Xiiong; Li, Li

2016-01-01

This study aims to assess the moisturization in combination or single use (including seven general applications) of three common moisturizers: cream, toner, and spray water. Groups were set as C: cream only; T: toner only; C+T, T+C: cream or toner applied successively within a few minutes; C-T, C-S: cream applied with repeated toner or spray water every 2 h; T-T: toner applied with repeated toner every 2 h; and N: untreated group. Outcomes were the change in skin hydration from baseline at 2, 4, 6, and 8 h after applications. All treated zones displayed a significantly higher degree of hydration compared with the untreated zone ( p < 0.05). For normal skin (hydration value at baseline >35 a.u.), C-T led to greatest hydration change rate compared with others, followed by C+T, T+C, and C. Those three applications exhibited analogous hydration at each test point ( p > 0.05). The hydration rate of C-S differed slightly from T-T, followed by those four mentioned above, with T being the last. For dry skin (hydration value at baseline <35 a.u.), no statistical significance could be detected between C-T zone and C+T, T+C, and C zones ( p > 0.05), the other results were identical. When cream and toner were applied successively, the application order has little effect on skin hydration. The application of cream only was an effective and brief way to achieve favorable moisturization especially for dry skin. As a complement, repeated application of toner rather than spray water is efficacious for skin hydration.
Soft X-Ray Diffraction Microscopy of a Frozen Hydrated Yeast Cell

DOE PAGES

Huang, Xiaojing; Nelson, Johanna; Kirz, Janos; ...

2009-11-01

We report the first image of an intact, frozen hydrated eukaryotic cell using x-ray diffraction microscopy, or coherent x-ray diffraction imaging. By plunge freezing the specimen in liquid ethane and maintaining it below -170 °C, artifacts due to dehydration, ice crystallization, and radiation damage are greatly reduced. In this example, coherent diffraction data using 520 eV x rays were recorded and reconstructed to reveal a budding yeast cell at a resolution better than 25 nm. This demonstration represents an important step towards high resolution imaging of cells in their natural, hydrated state, without limitations imposed by x-ray optics.
Growth of zeolite crystals in the microgravity environment of space

NASA Technical Reports Server (NTRS)

Sacco, A., Jr.; Sand, L. B.; Collette, D.; Dieselman, K.; Crowley, J.; Feitelberg, A.

1986-01-01

Zeolites are hydrated, crystalline aluminosilicates with alkali and alkaling earth metals substituted into cation vacancies. Typically zeolite crystals are 3 to 8 microns. Larger cyrstals are desirable. Large zeolite crystals were produced (100 to 200 microns); however, they have taken restrictively long times to grow. It was proposed if the rate of nucleation or in some other way the number of nuclei can be lowered, fewer, larger crystals will be formed. The microgravity environment of space may provide an ideal condition to achieve rapid growth of large zeolite crystals. The objective of the project is to establish if large zeolite crystals can be formed rapidly in space.
The role of amorphous precursors in the crystallization of La and Nd carbonates

NASA Astrophysics Data System (ADS)

Vallina, Beatriz; Rodriguez-Blanco, Juan Diego; Brown, Andrew P.; Blanco, Jesus A.; Benning, Liane G.

2015-07-01

Crystalline La and Nd carbonates can be formed from poorly-ordered nanoparticulate precursors, termed amorphous lanthanum carbonate (ALC) and amorphous neodymium carbonate (ANC). When reacted in air or in aqueous solutions these precursors show highly variable lifetimes and crystallization pathways. We have characterized these precursors and the crystallization pathways and products with solid-state, spectroscopic and microscopic techniques to explain the differences in crystallization mechanisms between the La and Nd systems. ALC and ANC consist of highly hydrated, 10-20 nm spherical nanoparticles with a general formula of REE2(CO3)3.5H2O (REE = La, Nd). The stabilities differ by ~2 orders of magnitude, with ANC being far more stable than ALC. This difference is due to the Nd3+ ion having a far higher hydration energy compared to the La3+ ion. This, together with temperature and reaction times, leads to clear differences not only in the kinetics and mechanisms of crystallization of the amorphous precursor La- and Nd-carbonate phases but also in the resulting crystallite sizes and morphologies of the end products. All crystalline La and Nd carbonates developed spherulitic morphologies when crystallization occurred from hydrous phases in solution at temperatures above 60 °C (La system) and 95 °C (Nd system). We suggest that spherulitic growth occurs due to a rapid breakdown of the amorphous precursors and a concurrent rapid increase in supersaturation levels in the aqueous solution. The kinetic data show that the crystallization pathway for both La and Nd carbonate systems is dependent on the reaction temperature and the ionic potential of the REE3+ ion.Crystalline La and Nd carbonates can be formed from poorly-ordered nanoparticulate precursors, termed amorphous lanthanum carbonate (ALC) and amorphous neodymium carbonate (ANC). When reacted in air or in aqueous solutions these precursors show highly variable lifetimes and crystallization pathways. We have characterized these precursors and the crystallization pathways and products with solid-state, spectroscopic and microscopic techniques to explain the differences in crystallization mechanisms between the La and Nd systems. ALC and ANC consist of highly hydrated, 10-20 nm spherical nanoparticles with a general formula of REE2(CO3)3.5H2O (REE = La, Nd). The stabilities differ by ~2 orders of magnitude, with ANC being far more stable than ALC. This difference is due to the Nd3+ ion having a far higher hydration energy compared to the La3+ ion. This, together with temperature and reaction times, leads to clear differences not only in the kinetics and mechanisms of crystallization of the amorphous precursor La- and Nd-carbonate phases but also in the resulting crystallite sizes and morphologies of the end products. All crystalline La and Nd carbonates developed spherulitic morphologies when crystallization occurred from hydrous phases in solution at temperatures above 60 °C (La system) and 95 °C (Nd system). We suggest that spherulitic growth occurs due to a rapid breakdown of the amorphous precursors and a concurrent rapid increase in supersaturation levels in the aqueous solution. The kinetic data show that the crystallization pathway for both La and Nd carbonate systems is dependent on the reaction temperature and the ionic potential of the REE3+ ion. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01497b
Microstructural aspects in steel fiber reinforced acrylic emulsion polymer modified concrete

NASA Astrophysics Data System (ADS)

Hazimmah, Dayang; Ayob, Afizah; Sie Yee, Lau; Chee Cung, Wong

2018-03-01

Scanning electron microscope observations of polymer-free and polymer-modified cements have shown that the polymer particles are partitioned between the inside of hydrates and the surface of anhydrous cement grains. For optimum dosage of acrylic emulsion polymer with 2.5%, the C-S-H gel in this structure is finer and more acicular. Some polymer adheres or deposit on the surface of the C-S-H gel. The presence of acrylic emulsion polymer confines the ionic diffusion so that the Ca(OH)2 crystallized locally to form fine crystals. The void in the structures seems to be smaller but no polymer films appears to be bridging the walls of pores although many polymer bonds or C-S-H spread into the pore spaces. In addition to porosity reduction, acrylic emulsion polymer modified the hydration products in the steel fiber -matrix ITZ. The hydration product C-S-H appeared as a needle like shape. The needle-shaped C-S-H increases and gradually formed the gel, with needles growing into the pore space. The phenomenon is more obvious as curing age increased.

Insights into water-mediated ion clustering in aqueous CaSO4 solutions: pre-nucleation cluster characteristics studied by ab initio calculations and molecular dynamics simulations.

PubMed

Li, Hui-Ji; Yan, Dan; Cai, Hou-Qin; Yi, Hai-Bo; Min, Xiao-Bo; Xia, Fei-Fei

2017-05-10

The molecular structure of growth units building crystals is a fundamental issue in the crystallization processes from aqueous solutions. In this work, a systematic investigation of pre-nucleation clusters and their hydration characteristics in aqueous CaSO 4 solutions was performed using ab initio calculations and molecular dynamics (MD) simulations. The results of ab initio calculations and MD simulations indicate that the dominant species in aqueous CaSO 4 solutions are monodentate ion-associated structures. Compared with charged ion clusters, neutral clusters are more likely to be present in an aqueous CaSO 4 solution. Neutral (CaSO 4 ) m clusters are probably the growth units involved in the pre-nucleation or crystallization processes. Meanwhile, hydration behavior around ion associated species in aqueous CaSO 4 solutions plays an important role in related phase/polymorphism selections. Upon ion clustering, the residence of some water molecules around Ca 2+ in ion-associated species is weakened while that of some bridging waters is enhanced due to dual interaction by Ca 2+ and SO 4 2- . Some phase/polymorphism selections can be achieved in aqueous CaSO 4 solutions by controlling the hydration around pre-nucleation clusters. Moreover, the association trend between calcium and sulfate is found to be relatively strong, which hints at the low solubility of calcium sulfate in water.
Improvements of nano-SiO2 on sludge/fly ash mortar.

PubMed

Lin, D F; Lin, K L; Chang, W C; Luo, H L; Cai, M Q

2008-01-01

Sewage sludge ash has been widely applied to cementitious materials. In this study, in order to determine effects of nano-SiO(2) additives on properties of sludge/fly ash mortar, different amounts of nano-SiO(2) were added to sludge/fly ash mortar specimens to investigate their physical properties and micro-structures. A water-binding ratio of 0.7 was assigned to the mix. Substitution amounts of 0%, 10%, 20%, and 30% of sludge/fly ash (1:1 ratio) were proposed. Moreover, 0%, 1%, 2%, and 3% of nano-SiO(2) was added to the mix. Tests, including SEM and compressive strength, were carried out on mortar specimens cured at 3, 7, and 28 days. Results showed that sludge/fly ash can make the crystals of cement hydration product finer. Moreover, crystals increased after nano-SiO(2) was added. Hence, nano-SiO(2) can improve the effects of sludge/fly ash on the hydration of mortar. Further, due to the low pozzolanic reaction active index of sludge ash, early compressive strengths of sludge/fly ash mortar were decreased. Yet, nano-SiO(2) could help produce hydration crystals, which implies that the addition of nano-SiO(2) to mortar can improve the influence of sludge/fly ash on the development of the early strength of the mortar.
Volume change associated with formation and dissociation of hydrate in sediment

USGS Publications Warehouse

Ruppel, Carolyn D.; Lee, J.Y.; Santamarina, J. Carlos

2017-01-01

Gas hydrate formation and dissociation in sediments are accompanied by changes in the bulk volume of the sediment and can lead to changes in sediment properties, loss of integrity for boreholes, and possibly regional subsidence of the ground surface over areas where methane might be produced from gas hydrate in the future. Experiments on sand, silts, and clay subject to different effective stress and containing different saturations of hydrate formed from dissolved phase tetrahydrofuran are used to systematically investigate the impact of gas hydrate formation and dissociation on bulk sediment volume. Volume changes in low specific surface sediments (i.e., having a rigid sediment skeleton like sand) are much lower than those measured in high specific surface sediments (e.g., clay). Early hydrate formation is accompanied by contraction for all soils and most stress states in part because growing gas hydrate crystals buckle skeletal force chains. Dilation can occur at high hydrate saturations. Hydrate dissociation under drained, zero lateral strain conditions is always associated with some contraction, regardless of soil type, effective stress level, or hydrate saturation. Changes in void ratio during formation-dissociation decrease at high effective stress levels. The volumetric strain during dissociation under zero lateral strain scales with hydrate saturation and sediment compressibility. The volumetric strain during dissociation under high shear is a function of the initial volume average void ratio and the stress-dependent critical state void ratio of the sediment. Other contributions to volume reduction upon hydrate dissociation are related to segregated hydrate in lenses and nodules. For natural gas hydrates, some conditions (e.g., gas production driven by depressurization) might contribute to additional volume reduction by increasing the effective stress.
Adhesion force interactions between cyclopentane hydrate and physically and chemically modified surfaces.

PubMed

Aman, Zachary M; Sloan, E Dendy; Sum, Amadeu K; Koh, Carolyn A

2014-12-07

Interfacial interactions between liquid-solid and solid-solid phases/surfaces are of fundamental importance to the formation of hydrate deposits in oil and gas pipelines. This work establishes the effect of five categories of physical and chemical modification to steel on clathrate hydrate adhesive force: oleamide, graphite, citric acid ester, nonanedithiol, and Rain-X anti-wetting agent. Hydrate adhesive forces were measured using a micromechanical force apparatus, under both dry and water-wet surface conditions. The results show that the graphite coating reduced hydrate-steel adhesion force by 79%, due to an increase in the water wetting angle from 42 ± 8° to 154 ± 7°. Two chemical surface coatings (nonanedithiol and the citric acid ester) induced rapid hydrate growth in the hydrate particles; nonanedithiol increased hydrate adhesive force by 49% from the baseline, while the citric acid ester coating reduced hydrate adhesion force by 98%. This result suggests that crystal growth may enable a strong adhesive pathway between hydrate and other crystalline structures, however this effect may be negated in cases where water-hydrocarbon interfacial tension is minimised. When a liquid water droplet was placed on the modified steel surfaces, the graphite and citric acid ester became less effective at reducing adhesive force. In pipelines containing a free water phase wetting the steel surface, chemical or physical surface modifications alone may be insufficient to eliminate hydrate deposition risk. In further tests, the citric acid ester reduced hydrate cohesive forces by 50%, suggesting mild activity as a hybrid anti-agglomerant suppressing both hydrate deposition and particle agglomeration. These results demonstrate a new capability to develop polyfunctional surfactants, which simultaneously limit the capability for hydrate particles to aggregate and deposit on the pipeline wall.
In Situ Monitoring the Uptake of Moisture into Hybrid Perovskite Thin Films.

PubMed

Schlipf, Johannes; Bießmann, Lorenz; Oesinghaus, Lukas; Berger, Edith; Metwalli, Ezzeldin; Lercher, Johannes A; Porcar, Lionel; Müller-Buschbaum, Peter

2018-04-19

Solution-processed hybrid perovskites are of great interest for use in photovoltaics. However, polycrystalline perovskite thin films show strong degradation in humid atmospheres, which poses an important challenge for large-scale market introduction. With in situ grazing incidence neutron scattering (GISANS) we analyzed water content, degradation products, and morphological changes during prolonged exposure to several humidity levels. In high humidity, the formation of metastable hydrate phases is accompanied by domain swelling, which transforms the faceted crystals to a round-washed, pebble-like form. The films incorporate much more water than is integrated into the hydrates, with smaller crystals being more affected, making the degradation strongly dependent on film morphology. Even at low humidity, water is adsorbed on the crystal surfaces without the formation of crystalline degradation products. Thus, although production in an ambient atmosphere is of interest for industrial production it might lead to long-term degradation without appropriate countermeasures like postproduction drying below 30% RH.
Formation of natural gas hydrates in marine sediments. Gas hydrate growth and stability conditioned by host sediment properties

USGS Publications Warehouse

Clennell, M.B.; Henry, P.; Hovland, M.; Booth, J.S.; Winters, W.J.; Thomas, M.

2000-01-01

The stability conditions of submarine gas hydrates (methane clathrates) are largely dictated by pressure, temperature, gas composition, and pore water salinity. However, the physical properties and surface chemistry of the host sediments also affect the thermodynamic state, growth kinetics, spatial distributions, and growth forms of clathrates. Our model presumes that gas hydrate behaves in a way analogous to ice in the pores of a freezing soil, where capillary forces influence the energy balance. Hydrate growth is inhibited within fine-grained sediments because of the excess internal phase pressure of small crystals with high surface curvature that coexist with liquid water in small pores. Therefore, the base of gas hydrate stability in a sequence of fine sediments is predicted by our model to occur at a lower temperature, and so nearer to the seabed than would be calculated from bulk thermodynamic equilibrium. The growth forms commonly observed in hydrate samples recovered from marine sediments (nodules, sheets, and lenses in muds; cements in sand and ash layers) can be explained by a requirement to minimize the excess of mechanical and surface energy in the system.
The Potential of Ikaite to Record the Oceanic Evolution of ?18O

NASA Astrophysics Data System (ADS)

Rickaby, R. E.; Shaw, S.; Bennitt, G.; Kennedy, H. A.; Lennie, A.

2005-12-01

Despite the importance of sea level for understanding past climates, paleoceanographers struggle to construct a continuous and definitive record of oceanic δ18O over millennial timescales. Here, we explore the possibility that ikaite, a hydrated form of calcium carbonate which forms monoclinic crystals made of CaCO3.6H2O units linked together by hydrogen bonds, may record the δ18O of the water from which it precipitates. Naturally occurring samples of ikaite have been found in the Ikka Fjord in Greenland where the crystals grow into huge chimneys around cold water springs at a temperature of 3°C, and ephemeral occurrences are also noted in alkaline lakes such as Mono Lake, California. The stability field of ikaite suggests that it should not exist at normal ocean temperatures and pressures. Nonetheless, the presence of ikaite has been recognised increasingly in areas such as the Bransfield Strait, Sea of Okhotsk, the Laptev Sea and the Lower Zaire Deep Sea fan, where sediments rich in organic carbon are characterised by high alkalinity and the presence of sulphate or phosphate which inhibits calcite precipitation. Whilst the presence and isotopic composition of glendonite, a pseudomorph of ikaite has been used as a key environmental indicator in the geological record, ikaite from recent ocean sediments has never been preserved for geochemical analysis. We have performed a series of laboratory growth experiments of ikaite under controlled conditions of alkalinity and temperature, from waters with a range of δ18O. Our results demonstrate that, in accordance with theory, the crystal bound waters in ikaite are isotopically heavier than the ambient water. Further a simple linear relationship with a non-zero intercept exists between the δ18O of the hydration waters of ikaite, and the waters from which the crystal precipitated. These data provide a firm foundation for application of this methodology to reconstruct oceanic δ18O from ikaite in Pleistocene sediments.
Heterogeneity of Chlorinity distribution within gas hydrate reservoir at Daini-Atsumi knoll, based on logging data analysis

NASA Astrophysics Data System (ADS)

Suzuki, K.; Takayama, T.; Fujii, T.

2016-12-01

We will present possible heterogeneity of pore-water salinity within methane hydrate reservoir of Daini-Atsumi knoll, on the basis of Logging-while-drilling (LWD) data and several kind of wire-line logging dataset. The LWD and the wire-line logging had been carried out during 2012 to 2013, before/after the first offshore gas-production-test from marine-methane-hydrate reservoir at Daini-Atsumi Knoll along the northeast Nankai trough. Several data from the logging, especially data from the reservoir saturation tool; RST, gave us some possible interpretation for heterogeneity distribution of chlorinity within the methane-hydrate reservoir. The computed pore-water chlorinity could be interpreted as condense of chlorinity at gas-hydrate formation. This year, we drilled several number of wells at Daini-Atsumi Knoll, again for next gas production test, and we have also found out possibility of chlorinity heterogeneity from LWD data of Neutron-capture cross section; i.e. Sigma. The distribution of chlorinity within gas-hydrate reservoir may help our understanding of gas hydrate-crystallization and/or dissociation in turbidite reservoir at Daini-Atsumi Knoll. This research is conducted as a part of the Research Consortium for Methane Hydrate Resource in Japan (MH21 Research consortium).
Dehydration-induced amorphous phases of calcium carbonate.

PubMed

Saharay, Moumita; Yazaydin, A Ozgur; Kirkpatrick, R James

2013-03-28

Amorphous calcium carbonate (ACC) is a critical transient phase in the inorganic precipitation of CaCO3 and in biomineralization. The calcium carbonate crystallization pathway is thought to involve dehydration of more hydrated ACC to less hydrated ACC followed by the formation of anhydrous ACC. We present here computational studies of the transition of a hydrated ACC with a H2O/CaCO3 ratio of 1.0 to anhydrous ACC. During dehydration, ACC undergoes reorganization to a more ordered structure with a significant increase in density. The computed density of anhydrous ACC is similar to that of calcite, the stable crystalline phase. Compared to the crystalline CaCO3 phases, calcite, vaterite, and aragonite, the computed local structure of anhydrous ACC is most-similar to those of calcite and vaterite, but the overall structure is not well described by either. The strong hydrogen bond interaction between the carbonate ions and water molecules plays a crucial role in stabilizing the less hydrated ACC compositions compared to the more hydrated ones, leading to a progressively increasing hydration energy with decreasing water content.
Ammonia clathrate hydrates as new solid phases for Titan, Enceladus, and other planetary systems.

PubMed

Shin, Kyuchul; Kumar, Rajnish; Udachin, Konstantin A; Alavi, Saman; Ripmeester, John A

2012-09-11

There is interest in the role of ammonia on Saturn's moons Titan and Enceladus as the presence of water, methane, and ammonia under temperature and pressure conditions of the surface and interior make these moons rich environments for the study of phases formed by these materials. Ammonia is known to form solid hemi-, mono-, and dihydrate crystal phases under conditions consistent with the surface of Titan and Enceladus, but has also been assigned a role as water-ice antifreeze and methane hydrate inhibitor which is thought to contribute to the outgassing of methane clathrate hydrates into these moons' atmospheres. Here we show, through direct synthesis from solution and vapor deposition experiments under conditions consistent with extraterrestrial planetary atmospheres, that ammonia forms clathrate hydrates and participates synergistically in clathrate hydrate formation in the presence of methane gas at low temperatures. The binary structure II tetrahydrofuran + ammonia, structure I ammonia, and binary structure I ammonia + methane clathrate hydrate phases synthesized have been characterized by X-ray diffraction, molecular dynamics simulation, and Raman spectroscopy methods.
Ammonia clathrate hydrates as new solid phases for Titan, Enceladus, and other planetary systems

PubMed Central

Shin, Kyuchul; Kumar, Rajnish; Udachin, Konstantin A.; Alavi, Saman; Ripmeester, John A.

2012-01-01

There is interest in the role of ammonia on Saturn’s moons Titan and Enceladus as the presence of water, methane, and ammonia under temperature and pressure conditions of the surface and interior make these moons rich environments for the study of phases formed by these materials. Ammonia is known to form solid hemi-, mono-, and dihydrate crystal phases under conditions consistent with the surface of Titan and Enceladus, but has also been assigned a role as water-ice antifreeze and methane hydrate inhibitor which is thought to contribute to the outgassing of methane clathrate hydrates into these moons’ atmospheres. Here we show, through direct synthesis from solution and vapor deposition experiments under conditions consistent with extraterrestrial planetary atmospheres, that ammonia forms clathrate hydrates and participates synergistically in clathrate hydrate formation in the presence of methane gas at low temperatures. The binary structure II tetrahydrofuran + ammonia, structure I ammonia, and binary structure I ammonia + methane clathrate hydrate phases synthesized have been characterized by X-ray diffraction, molecular dynamics simulation, and Raman spectroscopy methods. PMID:22908239
Physical stability enhancement of theophylline via cocrystallization.

PubMed

Trask, Andrew V; Motherwell, W D Sam; Jones, William

2006-08-31

The crystal form adopted by the respiratory drug theophylline was modified using a crystal engineering strategy in order to search for a solid material with improved physical stability. Cocrystals, also referred to as crystalline molecular complexes, were prepared with theophylline and one of several dicarboxylic acids. Four cocrystals of theophylline are reported, one each with oxalic, malonic, maleic and glutaric acids. Crystal structures were obtained for each cocrystal material, allowing an examination of the hydrogen bonding and crystal packing features. The cocrystal design scheme was partly based upon a series of recently reported cocrystals of the molecular analogue, caffeine, and comparisons in packing features are drawn between the two cocrystal series. The theophylline cocrystals were subjected to relative humidity challenges in order to assess their stability in relation to crystalline theophylline anhydrate and the equivalent caffeine cocrystals. None of the cocrystals in this study converted into a hydrated cocrystal upon storage at high relative humidity. Furthermore, the theophylline:oxalic acid cocrystal demonstrated superior humidity stability to theophylline anhydrate under the conditions examined, while the other cocrystals appeared to offer comparable stability to that of theophylline anhydrate. The results demonstrate the feasibility of pharmaceutical cocrystal design based upon the crystallization preferences of a molecular analogue, and furthermore show that avoidance of hydrate formation and improvement in physical stability is possible via pharmaceutical cocrystallization.
Crystal Nucleation in Liquids: Open Questions and Future Challenges in Molecular Dynamics Simulations

PubMed Central

2016-01-01

The nucleation of crystals in liquids is one of nature’s most ubiquitous phenomena, playing an important role in areas such as climate change and the production of drugs. As the early stages of nucleation involve exceedingly small time and length scales, atomistic computer simulations can provide unique insights into the microscopic aspects of crystallization. In this review, we take stock of the numerous molecular dynamics simulations that, in the past few decades, have unraveled crucial aspects of crystal nucleation in liquids. We put into context the theoretical framework of classical nucleation theory and the state-of-the-art computational methods by reviewing simulations of such processes as ice nucleation and the crystallization of molecules in solutions. We shall see that molecular dynamics simulations have provided key insights into diverse nucleation scenarios, ranging from colloidal particles to natural gas hydrates, and that, as a result, the general applicability of classical nucleation theory has been repeatedly called into question. We have attempted to identify the most pressing open questions in the field. We believe that, by improving (i) existing interatomic potentials and (ii) currently available enhanced sampling methods, the community can move toward accurate investigations of realistic systems of practical interest, thus bringing simulations a step closer to experiments. PMID:27228560
Crystal Nucleation in Liquids: Open Questions and Future Challenges in Molecular Dynamics Simulations.

PubMed

Sosso, Gabriele C; Chen, Ji; Cox, Stephen J; Fitzner, Martin; Pedevilla, Philipp; Zen, Andrea; Michaelides, Angelos

2016-06-22

The nucleation of crystals in liquids is one of nature's most ubiquitous phenomena, playing an important role in areas such as climate change and the production of drugs. As the early stages of nucleation involve exceedingly small time and length scales, atomistic computer simulations can provide unique insights into the microscopic aspects of crystallization. In this review, we take stock of the numerous molecular dynamics simulations that, in the past few decades, have unraveled crucial aspects of crystal nucleation in liquids. We put into context the theoretical framework of classical nucleation theory and the state-of-the-art computational methods by reviewing simulations of such processes as ice nucleation and the crystallization of molecules in solutions. We shall see that molecular dynamics simulations have provided key insights into diverse nucleation scenarios, ranging from colloidal particles to natural gas hydrates, and that, as a result, the general applicability of classical nucleation theory has been repeatedly called into question. We have attempted to identify the most pressing open questions in the field. We believe that, by improving (i) existing interatomic potentials and (ii) currently available enhanced sampling methods, the community can move toward accurate investigations of realistic systems of practical interest, thus bringing simulations a step closer to experiments.
Crystal structure of 8-hydroxyquinolinium 2-carboxy-6-nitrobenzoate monohydrate

PubMed Central

Divya Bharathi, M.; Ahila, G.; Mohana, J.; Chakkaravarthi, G.; Anbalagan, G.

2015-01-01

In the title hydrated salt, C9H8NO+·C8H4NO6 −·H2O, the deprotonated carboxylate group is almost normal to its attached benzene ring [dihedral angle = 83.56 (8)°], whereas the protonated carboxylate group is close to parallel [dihedral angle = 24.56 (9)°]. In the crystal, the components are linked by N—H⋯O and O—H⋯O hydrogen bonds, generating [001] chains. The packing is consolidated by C—H⋯O and π–π [centroid-to-centroid distances = 3.6408 (9) and 3.6507 (9) Å] interactions, which result in a three-dimensional network. PMID:26029446
A molecular dynamics study of ethanol-water hydrogen bonding in binary structure I clathrate hydrate with CO2

NASA Astrophysics Data System (ADS)

Alavi, Saman; Ohmura, Ryo; Ripmeester, John A.

2011-02-01

Guest-host hydrogen bonding in clathrate hydrates occurs when in addition to the hydrophilic moiety which causes the molecule to form hydrates under high pressure-low temperature conditions, the guests contain a hydrophilic, hydrogen bonding functional group. In the presence of carbon dioxide, ethanol clathrate hydrate has been synthesized with 10% of large structure I (sI) cages occupied by ethanol. In this work, we use molecular dynamics simulations to study hydrogen bonding structure and dynamics in this binary sI clathrate hydrate in the temperature range of 100-250 K. We observe that ethanol forms long-lived (>500 ps) proton-donating and accepting hydrogen bonds with cage water molecules from both hexagonal and pentagonal faces of the large cages while maintaining the general cage integrity of the sI clathrate hydrate. The presence of the nondipolar CO2 molecules stabilizes the hydrate phase, despite the strong and prevalent alcohol-water hydrogen bonding. The distortions of the large cages from the ideal form, the radial distribution functions of the guest-host interactions, and the ethanol guest dynamics are characterized in this study. In previous work through dielectric and NMR relaxation time studies, single crystal x-ray diffraction, and molecular dynamics simulations we have observed guest-water hydrogen bonding in structure II and structure H clathrate hydrates. The present work extends the observation of hydrogen bonding to structure I hydrates.
Pore-Scale Determination of Gas Relative Permeability in Hydrate-Bearing Sediments Using X-Ray Computed Micro-Tomography and Lattice Boltzmann Method

NASA Astrophysics Data System (ADS)

Chen, Xiongyu; Verma, Rahul; Espinoza, D. Nicolas; Prodanović, Maša.

2018-01-01

This work uses X-ray computed micro-tomography (μCT) to monitor xenon hydrate growth in a sandpack under the excess gas condition. The μCT images give pore-scale hydrate distribution and pore habit in space and time. We use the lattice Boltzmann method to calculate gas relative permeability (krg) as a function of hydrate saturation (Shyd) in the pore structure of the experimental hydrate-bearing sand retrieved from μCT data. The results suggest the krg - Shyd data fit well a new model krg = (1-Shyd)·exp(-4.95·Shyd) rather than the simple Corey model. In addition, we calculate krg-Shyd curves using digital models of hydrate-bearing sand based on idealized grain-attaching, coarse pore-filling, and dispersed pore-filling hydrate habits. Our pore-scale measurements and modeling show that the krg-Shyd curves are similar regardless of whether hydrate crystals develop grain-attaching or coarse pore-filling habits. The dispersed pore filling habit exhibits much lower gas relative permeability than the other two, but it is not observed in the experiment and not compatible with Ostwald ripening mechanisms. We find that a single grain-shape factor can be used in the Carman-Kozeny equation to calculate krg-Shyd data with known porosity and average grain diameter, suggesting it is a useful model for hydrate-bearing sand.
Surface acid-base properties and hydration/dehydration mechanisms of aluminum (hydr)oxides.

PubMed

Yang, Xiaofang; Sun, Zhongxi; Wang, Dongsheng; Forsling, Willis

2007-04-15

In this paper, surface physiochemical properties of three typical aluminas, gamma-Al(OH)3, gamma-Al2O3, and alpha-Al2O3, were investigated by means of XRD, SEM, TEM, BET surface area, TG/DTA, and potentiometric titration techniques. Based on the titration data, surface protonation and deprotonation constants were determined using the constant capacitance model (CCM). The emphasis of this research was laid on the comparison of the crystal structure, surface hydration/dehydration and acid-base properties of these three typical alumina minerals. The calculation results revealed that the surface acidity of the aluminas is in the order of alpha-Al2O3>gamma-Al(OH)3>gamma-Al2O3 after being hydrated for 1 h. The correlation between the hydration/dehydration mechanisms of alumina and its acid/base properties is discussed.
Chemistry, isotopic composition, and origin of a methane-hydrogen sulfide hydrate at the Cascadia subduction zone

USGS Publications Warehouse

Kastner, M.; Kvenvolden, K.A.; Lorenson, T.D.

1998-01-01

Although the presence of extensive gas hydrate on the Cascadia margin, offshore from the western U.S. and Canada, has been inferred from marine seismic records and pore water chemistry, solid gas hydrate has only been found at one location. At Ocean Drilling Program (ODP) Site 892, offshore from central Oregon, gas hydrate was recovered close to the sediment - water interface at 2-19 m below the seafloor, (mbsf) at 670 m water depth. The gas hydrate occurs as elongated platy crystals or crystal aggregates, mostly disseminated irregularly, with higher concentrations occurring in discrete zones, thin layers, and/or veinlets parallel or oblique to the bedding. A 2-to 3-cm thick massive gas hydrate layer, parallel to bedding, was recovered at ???17 mbsf. Gas from a sample of this layer was composed of both CH4 and H2S. This sample is the first mixed-gas hydrate of CH4-H2S documented in ODP; it also contains ethane and minor amounts of CO2. Measured temperature of the recovered core ranged from 2 to - 18??C and are 6 to 8 degrees lower than in-situ temperatures. These temperature anomalies were caused by the partial dissociation of the CH4-H2S hydrate during recovery without a pressure core sampler. During this dissociation, toxic levels of H2S (??34S, +27.4???) were released. The ??13C values of the CH4 in the gas hydrate, -64.5 to -67.5???(PDB), together with ??D values of - 197 to - 199???(SMOW) indicate a primarily microbial source for the CH4. The ??18O value of the hydrate H2O is +2.9???(SMOW), comparable with the experimental fractionation factor for sea-ice. The unusual composition (CH4-H2S) and depth distribution (2-19 mbsf) of this gas hydrate indicate mixing between a methane-rich fluid with a pore fluid enriched in sulfide; at this site the former is advecting along an inclined fault into the active sulfate reduction zone. The facts that the CH4-H2S hydrate is primarily confined to the present day active sulfate reduction zone (2-19 mbsf), and that from here down to the BSR depth (19-68 mbsf) the gas hydrate inferred to exist is a ???99% CH4 hydrate, suggest that the mixing of CH4 and H2S is a geologically young process. Because the existence of a mixed CH4-H2S hydrate is indicative of moderate to intense advection of a methane-rich fluid into a near surface active sulfate reduction zone, technically active (faulted) margins with organic-rich sediments and moderate to high sedimentation rates are the most likely regions of occurrence. The extension of such a mixed hydrate below the sulfate reduction zone should reflect the time-span of methane advection into the sulfate reduction zone. ?? 1998 Elsevier Science B.V. All rights reserved.
The effects of ice on methane hydrate nucleation: a microcanonical molecular dynamics study.

PubMed

Zhang, Zhengcai; Guo, Guang-Jun

2017-07-26

Although ice powders are widely used in gas hydrate formation experiments, the effects of ice on hydrate nucleation and what happens in the quasi-liquid layer of ice are still not well understood. Here, we used high-precision constant energy molecular dynamics simulations to study methane hydrate nucleation from vapor-liquid mixtures exposed to the basal, prismatic, and secondary prismatic planes of hexagonal ice (ice Ih). Although no significant difference is observed in hydrate nucleation processes for these different crystal planes, it is found, more interestingly, that methane hydrate can nucleate either on the ice surface heterogeneously or in the bulk solution phase homogeneously. Several factors are mentioned to be able to promote the heterogeneous nucleation of hydrates, including the adsorption of methane molecules at the solid-liquid interface, hydrogen bonding between hydrate cages and the ice structure, the stronger ability of ice to transfer heat than that of the aqueous solution, and the higher occurrence probability of hydrate cages in the vicinity of the ice surface than in the bulk solution. Meanwhile, however, the other factors including the hydrophilicity of ice and the ice lattice mismatch with clathrate hydrates can inhibit heterogeneous nucleation on the ice surface and virtually promote homogeneous nucleation in the bulk solution. Certainly, the efficiency of ice as a promoter and as an inhibitor for heterogeneous nucleation is different. We estimate that the former is larger than the latter under the working conditions. Additionally, utilizing the benefit of ice to absorb heat, the NVE simulation of hydrate formation with ice can mimic the phenomenon of ice shrinking during the heterogeneous nucleation of hydrates and lower the overly large temperature increase during homogeneous nucleation. These results are helpful in understanding the nucleation mechanism of methane hydrate in the presence of ice.

Microcrystalline dolomite within massive Japan Sea methane hydrate: origin and development ascertained by inclusions within inclusions.

NASA Astrophysics Data System (ADS)

Snyder, G. T.; Kakizaki, Y.; Matsumoto, R.; Suzuki, Y.; Takahata, N.; Sano, Y.; Tanaka, K.; Tomaru, H.; Imajo, T.; Iguchi, A.

2017-12-01

Microcrystalline dolomite grains were recently discovered as inclusions within relatively pure massive gas hydrate recovered from the Joetsu Basin area of the Japan Sea. These grains presumably formed as a consequence of the highly saline conditions in fluid inclusions which developed between coalescing grain boundaries within the growing hydrate. Stable carbon and oxygen isotopic composition of the dolomite is consistent with crystal growth occurring within such fluids. In addition to stable isotopes, we investigate trends in Mg/Ca ratios of the grains as well as the composition of inclusions which exist within the dolomites. Preliminary research shows that these inclusions retain valuable information as to the conditions which existed at the time of formation, as well as the dynamics of these extensive hydrate deposits over time. This study was conducted under the commission from AIST as a part of the methane hydrate research project funded by METI (the Ministry of Economy, Trade and Industry, Japan).
Multiscale understanding of tricalcium silicate hydration reactions.

PubMed

Cuesta, Ana; Zea-Garcia, Jesus D; Londono-Zuluaga, Diana; De la Torre, Angeles G; Santacruz, Isabel; Vallcorba, Oriol; Dapiaggi, Monica; Sanfélix, Susana G; Aranda, Miguel A G

2018-06-04

Tricalcium silicate, the main constituent of Portland cement, hydrates to produce crystalline calcium hydroxide and calcium-silicate-hydrates (C-S-H) nanocrystalline gel. This hydration reaction is poorly understood at the nanoscale. The understanding of atomic arrangement in nanocrystalline phases is intrinsically complicated and this challenge is exacerbated by the presence of additional crystalline phase(s). Here, we use calorimetry and synchrotron X-ray powder diffraction to quantitatively follow tricalcium silicate hydration process: i) its dissolution, ii) portlandite crystallization and iii) C-S-H gel precipitation. Chiefly, synchrotron pair distribution function (PDF) allows to identify a defective clinotobermorite, Ca 11 Si 9 O 28 (OH) 2 . 8.5H 2 O, as the nanocrystalline component of C-S-H. Furthermore, PDF analysis also indicates that C-S-H gel contains monolayer calcium hydroxide which is stretched as recently predicted by first principles calculations. These outcomes, plus additional laboratory characterization, yielded a multiscale picture for C-S-H nanocomposite gel which explains the observed densities and Ca/Si atomic ratios at the nano- and meso- scales.
Navigating the Waters of Unconventional Crystalline Hydrates

PubMed Central

2015-01-01

Elucidating the crystal structures, transformations, and thermodynamics of the two zwitterionic hydrates (Hy2 and HyA) of 3-(4-dibenzo[b,f][1,4]oxepin-11-yl-piperazin-1-yl)-2,2-dimethylpropanoic acid (DB7) rationalizes the complex interplay of temperature, water activity, and pH on the solid form stability and transformation pathways to three neutral anhydrate polymorphs (Forms I, II°, and III). HyA contains 1.29 to 1.95 molecules of water per DB7 zwitterion (DB7z). Removal of the essential water stabilizing HyA causes it to collapse to an amorphous phase, frequently concomitantly nucleating the stable anhydrate Forms I and II°. Hy2 is a stoichiometric dihydrate and the only known precursor to Form III, a high energy disordered anhydrate, with the level of disorder depending on the drying conditions. X-ray crystallography, solid state NMR, and H/D exchange experiments on highly crystalline phase pure samples obtained by exquisite control over crystallization, filtration, and drying conditions, along with computational modeling, provided a molecular level understanding of this system. The slow rates of many transformations and sensitivity of equilibria to exact conditions, arising from its varying static and dynamic disorder and water mobility in different phases, meant that characterizing DB7 hydration in terms of simplified hydrate classifications was inappropriate for developing this pharmaceutical. PMID:26075319
Controlled dehydration of a ruthenium complex-DNA crystal induces reversible DNA kinking.

PubMed

Hall, James P; Sanchez-Weatherby, Juan; Alberti, Cora; Quimper, Caroline Hurtado; O'Sullivan, Kyra; Brazier, John A; Winter, Graeme; Sorensen, Thomas; Kelly, John M; Cardin, David J; Cardin, Christine J

2014-12-17

Hydration-dependent DNA deformation has been known since Rosalind Franklin recognized that the relative humidity of the sample had to be maintained to observe a single conformation in DNA fiber diffraction. We now report for the first time the crystal structure, at the atomic level, of a dehydrated form of a DNA duplex and demonstrate the reversible interconversion to the hydrated form at room temperature. This system, containing d(TCGGCGCCGA) in the presence of Λ-[Ru(TAP)2(dppz)](2+) (TAP = 1,4,5,8-tetraazaphenanthrene, dppz = dipyrido[3,2-a:2',3'-c]phenazine), undergoes a partial transition from an A/B hybrid to the A-DNA conformation, at 84-79% relative humidity. This is accompanied by an increase in kink at the central step from 22° to 51°, with a large movement of the terminal bases forming the intercalation site. This transition is reversible on rehydration. Seven data sets, collected from one crystal at room temperature, show the consequences of dehydration at near-atomic resolution. This result highlights that crystals, traditionally thought of as static systems, are still dynamic and therefore can be the subject of further experimentation.
Effect of a new moisturizing lotion on immediate and cumulative skin hydration: Two randomized, intra-individual, vehicle- and comparator-controlled studies.

PubMed

Nogueira, Alessandra; Sidou, Farzaneh; Brocard, Sylvie

2011-08-01

Moisturizers increase skin hydration and can serve as adjunctive care in dermatologic conditions such as xerosis, psoriasis vulgaris, atopic dermatitis and ichthyosis, in which dry skin is implicated. A non-irritating hydrating lotion (CDA lotion) was recently developed. We assessed the effect of CDA lotion on skin hydration in two randomized, evaluator-blind and intra-individual comparison studies. After a single application, CDA lotion induced significantly greater hydration than the non-treated control for at least 24 hours (p < 0.001). After 4 days of twice-daily application, compared with the non-treated control, CDA lotion induced significantly greater skin hydration up to 3 days after treatment cessation (p < 0.05) and significant improvement in the clinical skin dryness score up to 7 days after treatment cessation (p < 0.05). The immediate and cumulative hydration effects of CDA lotion were also compared to those of several currently available moisturizing products. In summary, application of CDA lotion increases skin hydration and alleviates the condition of skin dryness.
Mechanical and electromagnetic properties of northern Gulf of Mexico sediments with and without THF hydrates

USGS Publications Warehouse

Lee, J.Y.; Santamarina, J.C.; Ruppel, C.

2008-01-01

Using an oedometer cell instrumented to measure the evolution of electromagnetic properties, small strain stiffness, and temperature, we conducted consolidation tests on sediments recovered during drilling in the northern Gulf of Mexico at the Atwater Valley and Keathley Canyon sites as part of the 2005 Chevron Joint Industry Project on Methane Hydrates. The tested specimens include both unremolded specimens (as recovered from the original core liner) and remolded sediments both without gas hydrate and with pore fluid exchanged to attain 100% synthetic (tetrahydrofuran) hydrate saturation at any stage of loading. Test results demonstrate the extent to which the electromagnetic and mechanical properties of hydrate-bearing marine sediments are governed by the vertical effective stress, stress history, porosity, hydrate saturation, fabric, ionic concentration of the pore fluid, and temperature. We also show how permittivity and electrical conductivity data can be used to estimate the evolution of hydrate volume fraction during formation. The gradual evolution of geophysical properties during hydrate formation probably reflects the slow increase in ionic concentration in the pore fluid due to ion exclusion in closed systems and the gradual decrease in average pore size in which the hydrate forms. During hydrate formation, the increase in S-wave velocity is delayed with respect to the decrease in permittivity, consistent with hydrate formation on mineral surfaces and subsequent crystal growth toward the pore space. No significant decementation/debonding occurred in 100% THF hydrate-saturated sediments during unloading, hence the probability of sampling hydrate-bearing sediments without disturbing the original sediment fabric is greatest for samples in which the gas hydrate is primarily responsible for maintaining the sediment fabric and for which the time between core retrieval and restoration of in situ effective stress in the laboratory is minimized. In evaluating the impact of core retrieval on specimen properties, it is also important to consider how far removed hydrate-bearing samples are from hydrate stability conditions. ?? 2008 Elsevier Ltd.
Crystal structure of tin(IV) chloride octahydrate

PubMed Central

Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

2014-01-01

The title compound, [SnCl4(H2O)2]·6H2O, was crystallized according to the solid–liquid phase diagram at lower temperatures. It is built-up of SnCl4(H2O)2 octahedral units (point group symmetry 2) and lattice water molecules. An intricate three-dimensional network of O—H⋯O and O—H⋯Cl hydrogen bonds between the complex molecules and the lattice water molecules is formed in the crystal structure. PMID:25552971
Chemical and Biological Sensing Using Diatom Photonic Crystal Biosilica With In-Situ Growth Plasmonic Nanoparticles.

PubMed

Kong, Xianming; Squire, Kenny; Li, Erwen; LeDuff, Paul; Rorrer, Gregory L; Tang, Suning; Chen, Bin; McKay, Christopher P; Navarro-Gonzalez, Rafael; Wang, Alan X

2016-12-01

In this paper, we described a new type of bioenabled nano-plasmonic sensors based on diatom photonic crystal biosilica with in-situ growth silver nanoparticles and demonstrated label-free chemical and biological sensing based on surface-enhanced Raman scattering (SERs) from complex samples. Diatoms are photosynthetic marine micro-organisms that create their own skeletal shells of hydrated amorphous silica, called frustules, which possess photonic crystal-like hierarchical micro- & nanoscale periodic pores. Our research shows that such hybrid plasmonic-biosilica nanostructures formed by cost-effective and eco-friendly bottom-up processes can achieve ultra-high limit of detection for medical applications, food sensing, water/air quality monitoring and geological/space research. The enhanced sensitivity comes from the optical coupling of the guided-mode resonance of the diatom frustules and the localized surface plasmons of the silver nanoparticles. Additionally, the nanoporous, ultra-hydrophilic diatom biosilica with large surface-to-volume ratio can concentrate more analyte molecules to the surface of the SERS substrates, which can help to detect biomolecules that cannot be easily adsorbed by metallic nanoparticles.
Structural Properties, Order–Disorder Phenomena, and Phase Stability of Orotic Acid Crystal Forms

PubMed Central

2016-01-01

Orotic acid (OTA) is reported to exist in the anhydrous (AH), monohydrate (Hy1), and dimethyl sulfoxide monosolvate (SDMSO) forms. In this study we investigate the (de)hydration/desolvation behavior, aiming at an understanding of the elusive structural features of anhydrous OTA by a combination of experimental and computational techniques, namely, thermal analytical methods, gravimetric moisture (de)sorption studies, water activity measurements, X-ray powder diffraction, spectroscopy (vibrational, solid-state NMR), crystal energy landscape, and chemical shift calculations. The Hy1 is a highly stable hydrate, which dissociates above 135 °C and loses only a small part of the water when stored over desiccants (25 °C) for more than one year. In Hy1, orotic acid and water molecules are linked by strong hydrogen bonds in nearly perfectly planar arranged stacked layers. The layers are spaced by 3.1 Å and not linked via hydrogen bonds. Upon dehydration the X-ray powder diffraction and solid-state NMR peaks become broader, indicating some disorder in the anhydrous form. The Hy1 stacking reflection (122) is maintained, suggesting that the OTA molecules are still arranged in stacked layers in the dehydration product. Desolvation of SDMSO, a nonlayer structure, results in the same AH phase as observed upon dehydrating Hy1. Depending on the desolvation conditions, different levels of order–disorder of layers present in anhydrous OTA are observed, which is also suggested by the computed low energy crystal structures. These structures provide models for stacking faults as intergrowth of different layers is possible. The variability in anhydrate crystals is of practical concern as it affects the moisture dependent stability of AH with respect to hydration. PMID:26741914
Nucleation and growth of crystals under cirrus and polar stratospheric cloud conditions

NASA Technical Reports Server (NTRS)

Hallett, John; Queen, Brian; Teets, Edward; Fahey, James

1995-01-01

Laboratory studies examine phase changes of hygroscopic substances which occur as aerosol in stratosphere and troposphere (sodium chloride, ammonium sulfate, ammonium bisulfate, nitric acid, sulfuric acid), under controlled conditions, in samples volume 1 to 10(exp -4) ml. Crystallization of salts from supersaturated solutions is examined by slowly evaporating a solution drop on a substrate, under controlled relative humidity, until self nucleation occurs; controlled nucleation of ice in a mm capillary U-tube gives a measured ice crystallization velocity at known supercooling. Two states of crystallization occur for regions where hydrates exist. It is inferred that all of the materials readily exist as supersaturated/supercooled solutions; the degree of metastability appears to be slightly enhanced by inclusion of aircraft produced soot. The crystallization velocity is taken as a measure of viscosity. Results suggest an approach to a glass transition at high molality, supersaturation and/or supercooling within the range of atmospheric interest. It is hypothesized that surface reactions occur more readily on solidified particles - either crystalline or glass, whereas volume reactions are more important on droplets with sufficiently low viscosity and volume diffusivity. Implications are examined for optical properties of such particles in the atmosphere. In a separate experiment, crystal growth was examined in a modified thermal vapor diffusion chamber over the range of cirrus temperature (-30 to -70 C) and under controlled supersaturation and air pressure. The crystals grew at a velocity of 1-2 microns/s, thickness 60-70 micron, in the form of thin column crystals. Design criteria are given for a system to investigate particle growth down to -100 C, (PSC temperatures) where nitric acid particles can be grown under similar control and in the form of hydrate crystals.
The Dependence of Water Permeability in Quartz Sand on Gas Hydrate Saturation in the Pore Space

NASA Astrophysics Data System (ADS)

Kossel, E.; Deusner, C.; Bigalke, N.; Haeckel, M.

2018-02-01

Transport of fluids in gas hydrate bearing sediments is largely defined by the reduction of the permeability due to gas hydrate crystals in the pore space. Although the exact knowledge of the permeability behavior as a function of gas hydrate saturation is of crucial importance, state-of-the-art simulation codes for gas production scenarios use theoretically derived permeability equations that are hardly backed by experimental data. The reason for the insufficient validation of the model equations is the difficulty to create gas hydrate bearing sediments that have undergone formation mechanisms equivalent to the natural process and that have well-defined gas hydrate saturations. We formed methane hydrates in quartz sand from a methane-saturated aqueous solution and used magnetic resonance imaging to obtain time-resolved, three-dimensional maps of the gas hydrate saturation distribution. These maps were fed into 3-D finite element method simulations of the water flow. In our simulations, we tested the five most well-known permeability equations. All of the suitable permeability equations include the term (1-SH)n, where SH is the gas hydrate saturation and n is a parameter that needs to be constrained. The most basic equation describing the permeability behavior of water flow through gas hydrate bearing sand is k = k0 (1-SH)n. In our experiments, n was determined to be 11.4 (±0.3). Results from this study can be directly applied to bulk flow analysis under the assumption of homogeneous gas hydrate saturation and can be further used to derive effective permeability models for heterogeneous gas hydrate distributions at different scales.
Stability of CO2 hydrate under very high pressure and low temperature

NASA Astrophysics Data System (ADS)

Hirai, H.; Honda, M.; Kawamura, T.; Yamamoto, Y.; Yagi, T.

2009-12-01

CO2 hydrate is a clathrate compound and the crystal structure type is sI at low pressure. CO2-reduction in the atmosphere is one of the most urgent subjects for mankind. Some technical developments to seclude CO2 as CO2 hydrate in ocean floor have been proceeded. Looking around the solar system, existence of CO2 hydrate in and beneath Martian permafrost has been predicted from spacecraft probes and theoretical studies. Thus, its stability and properties under high pressures and low temperatures are of great interest for fundamental understanding of clathrate hydrate, for the ocean sequestration technology, and for planetary science. CO2 hydrate exhibits characteristic properties different from those of other gas hydrate such as methane hydrate. For example, phase boundary between hydrate and gas + water for many gas hydrates shows positive slope in pressure versus temperature field, and the gas hydrates are kept at pressures up to several GPa at room temperature. On the other hand, for CO2 hydrate, the phase boundary turns to negative slope from positive one at a certain critical point [Nakano et al., 1998], and it can exist only at low temperature regions. And, a theoretical study predicted that CO2 hydrate decompose at low temperature region [Longhi, 2005]. In this study, high pressure and low temperature experiments were performed to examine stability and phase changes of CO2 hydrate using diamond anvil cell in a pressure range from 0.1 to 2.5 GPa and a the temperature range from 65 to 265 K. X-ray diffractometry and Raman spectroscopy revealed that the known phase boundary was extended into lower temperature region, and that CO2 hydrate was kept at low temperature regions at least 65 K despite the theoretical prediction of decomposition. References [1] S. Nakano, M. Moritoki, K. Ohgaki, J. Chem. Eng. Data, 43, 807 (1998). [2] J. Longhi, Geochim. Cosmochim. Acta, 69, 529 (2005)
Grain-scale imaging and compositional characterization of cryo-preserved India NGHP 01 gas-hydrate-bearing cores

USGS Publications Warehouse

Stern, Laura A.; Lorenson, T.D.

2014-01-01

We report on grain-scale characteristics and gas analyses of gas-hydrate-bearing samples retrieved by NGHP Expedition 01 as part of a large-scale effort to study gas hydrate occurrences off the eastern-Indian Peninsula and along the Andaman convergent margin. Using cryogenic scanning electron microscopy, X-ray spectroscopy, and gas chromatography, we investigated gas hydrate grain morphology and distribution within sediments, gas hydrate composition, and methane isotopic composition of samples from Krishna–Godavari (KG) basin and Andaman back-arc basin borehole sites from depths ranging 26 to 525 mbsf. Gas hydrate in KG-basin samples commonly occurs as nodules or coarse veins with typical hydrate grain size of 30–80 μm, as small pods or thin veins 50 to several hundred microns in width, or disseminated in sediment. Nodules contain abundant and commonly isolated macropores, in some places suggesting the original presence of a free gas phase. Gas hydrate also occurs as faceted crystals lining the interiors of cavities. While these vug-like structures constitute a relatively minor mode of gas hydrate occurrence, they were observed in near-seafloor KG-basin samples as well as in those of deeper origin (>100 mbsf) and may be original formation features. Other samples exhibit gas hydrate grains rimmed by NaCl-bearing material, presumably produced by salt exclusion during original hydrate formation. Well-preserved microfossil and other biogenic detritus are also found within several samples, most abundantly in Andaman core material where gas hydrate fills microfossil crevices. The range of gas hydrate modes of occurrence observed in the full suite of samples suggests a range of formation processes were involved, as influenced by local in situconditions. The hydrate-forming gas is predominantly methane with trace quantities of higher molecular weight hydrocarbons of primarily microbial origin. The composition indicates the gas hydrate is Structure I.
Simulations of single-particle imaging of hydrated proteins with x-ray free-electron lasers

NASA Astrophysics Data System (ADS)

Fortmann-Grote, C.; Bielecki, J.; Jurek, Z.; Santra, R.; Ziaja-Motyka, B.; Mancuso, A. P.

2017-08-01

We employ start-to-end simulations to model coherent diffractive imaging of single biomolecules using x-ray free electron lasers. This technique is expected to yield new structural information about biologically relevant macromolecules thanks to the ability to study the isolated sample in its natural environment as opposed to crystallized or cryogenic samples. The effect of the solvent on the diffraction pattern and interpretability of the data is an open question. We present first results of calculations where the solvent is taken into account explicitly. They were performed with a molecular dynamics scheme for a sample consisting of a protein and a hydration layer of varying thickness. Through R-factor analysis of the simulated diffraction patterns from hydrated samples, we show that the scattering background from realistic hydration layers of up to 3 Å thickness presents no obstacle for the resolution of molecular structures at the sub-nm level.
cis-Dichloridobis-(5,5'-dimethyl-2,2'-bipyridine)-manganese(II) 2.5-hydrate.

PubMed

Lopes, Lívia Batista; Corrêa, Charlane Cimini; Diniz, Renata

2011-07-01

The metal site in the title compound [MnCl(2)(C(12)H(12)N(2))(2)]·2.5H(2)O has a distorted octa-hedral geometry, coordinated by four N atoms of two 5,5'-dimethyl-2,2'-dipyridine ligands and two Cl atoms. Two and a half water molecules of hydration per complex unit are observed in the crystal structure. The compounds extend along the c axis with O-H⋯Cl, O-H⋯O, C-H⋯Cl and C-H⋯O hydrogen bonds and π-π inter-actions [centroid-centroid distance = 3.70 (2) Å] contributing substanti-ally to the crystal packing. The Mn and one of the water O atoms, the latter being half-occupied, are located on special positions, in this case a rotation axis of order 2.
Laboratory Investigation of the Growth and Crystal Structure of Nitric Acid Hydrates by Transmission Electron Microscopy (TEM)

NASA Technical Reports Server (NTRS)

Blake, David F.; Chang, Sherwood (Technical Monitor)

1994-01-01

A great deal of recent laboratory work has focussed on the characterization of the nitric acid hydrates, thought to be present in type I Polar Stratospheric Clouds (PSCs). Phase relationships and vapor pressure measurements (1-3) and infrared characterizations (4-5) have been made. However, the observed properties of crystalline solids (composition, melting point, vapor pressure, surface reactivity, thermodynamic stability, extent of solid solution with other components, etc.) are controlled by their crystal structure. The only means of unequivocal structural identification for crystalline solids is diffraction (using electrons, X-rays, neutrons, etc.). Other observed properties of crystalline solids, such as their infrared spectra, their vapor pressure as a function of temperature, etc. yield only indirect information about what phases are present, their relative proportions, or whether they are crystalline or amorphous.
X-ray crystal structures of native HIV-1 capsid protein reveal conformational variability

DOE PAGES

Gres, Anna T.; Kirby, Karen A.; KewalRamani, Vineet N.; ...

2015-06-04

The detailed molecular interactions between native HIV-1 capsid protein (CA) hexamers that shield the viral genome and proteins have been elusive. In this paper, we report crystal structures describing interactions between CA monomers related by sixfold symmetry within hexamers (intrahexamer) and threefold and twofold symmetry between neighboring hexamers (interhexamer). The structures describe how CA builds hexagonal lattices, the foundation of mature capsids. Lattice structure depends on an adaptable hydration layer modulating interactions among CA molecules. Disruption of this layer alters interhexamer interfaces, highlighting an inherent structural variability. A CA-targeting antiviral affects capsid stability by binding across CA molecules and subtlymore » altering interhexamer interfaces remote to the ligand-binding site. Finally, inherent structural plasticity, hydration layer rearrangement, and effector binding affect capsid stability and have functional implications for the retroviral life cycle.« less
Measurement of clathrate hydrates via Raman spectroscopy

USGS Publications Warehouse

Sum, A.K.; Burruss, R.C.; Sloan, E.D.

1997-01-01

Raman spectra of clathrate hydrate guest molecules are presented for three known structures (I (sI), II (sII), and H (sH)) in the following systems: CH4 (sI), CO2 (sI), C3H8 (sII), CH4 + CO2 (sI), CD4 + C3H8 (sII), CH4 + N2 (sI), CH4 + THF-d8 (sII), and CH4 + C7D14 (sH). Relative occupancy of CH4 in the large and small cavities of sI were determined by deconvoluting the ??1 symmetric bands, resulting in hydration numbers of 6.04 ?? 0.03. The frequency of the ??1 bands for CH4 in structures I, II, and H differ statistically, so that Raman spectroscopy is a potential tool to identify hydrate crystal structure. Hydrate guest compositions were also measured for two vapor compositions of the CH4 + CO2 system, and they compared favorably with predictions. The large cavities were measured to be almost fully occupied by CH4 and CO2, whereas only a small fraction of the small cavities are occupied by CH4. No CO2 was found in the small cavities. Hydration numbers from 7.27 to 7.45 were calculated for the mixed hydrate.
Pharmaceutical cocrystals: walking the talk.

PubMed

Bolla, Geetha; Nangia, Ashwini

2016-06-28

Pharmaceutical cocrystals belong to a sub-class of cocrystals wherein one of the components is a drug molecule (or an active pharmaceutical ingredient, API) and the second is a benign food or drug grade additive (generally regarded as safe, GRAS). The two components are hydrogen-bonded in a fixed stoichiometric ratio in the crystal lattice. In the past decade, pharmaceutical cocrystals have demonstrated significant promise in their ability to modify the physicochemical and pharmacokinetic properties of drug substances, such as the solubility and dissolution rate, bioavailability, particle morphology and size, tableting and compaction, melting point, physical form, biochemical and hydration stability, and permeability. In this feature review, we highlight some prominent examples of drug cocrystals which exhibit variable hardness/softness and elasticity/plasticity depending on coformer selection, improvement of solubility and permeability in the same cocrystal, increase of the melting point for solid formulation, enhanced color performance, photostability and hydration stability, and a longer half-life. Cocrystals of flavanoids and polyphenols can make improved pharmaceuticals and also extend to the larger class of nutraceuticals. The application of crystal engineering to assemble ternary cocrystals expands this field to drug-drug cocrystals which may be useful in multi-drug resistance, mitigating side effects of drugs, or attenuating/enhancing drug action synergistically by rational selection. The advent of new techniques for structural characterization beyond the standard X-ray diffraction will provide a better understanding of drug phases which are at the borderline of crystalline-amorphous nature and even newer opportunities in the future.
Examination of core samples from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: Effects of retrieval and preservation

USGS Publications Warehouse

Kneafsey, T.J.; Lu, H.; Winters, W.; Boswell, R.; Hunter, R.; Collett, T.S.

2011-01-01

Collecting and preserving undamaged core samples containing gas hydrates from depth is difficult because of the pressure and temperature changes encountered upon retrieval. Hydrate-bearing core samples were collected at the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well in February 2007. Coring was performed while using a custom oil-based drilling mud, and the cores were retrieved by a wireline. The samples were characterized and subsampled at the surface under ambient winter arctic conditions. Samples thought to be hydrate bearing were preserved either by immersion in liquid nitrogen (LN), or by storage under methane pressure at ambient arctic conditions, and later depressurized and immersed in LN. Eleven core samples from hydrate-bearing zones were scanned using x-ray computed tomography to examine core structure and homogeneity. Features observed include radial fractures, spalling-type fractures, and reduced density near the periphery. These features were induced during sample collection, handling, and preservation. Isotopic analysis of the methane from hydrate in an initially LN-preserved core and a pressure-preserved core indicate that secondary hydrate formation occurred throughout the pressurized core, whereas none occurred in the LN-preserved core, however no hydrate was found near the periphery of the LN-preserved core. To replicate some aspects of the preservation methods, natural and laboratory-made saturated porous media samples were frozen in a variety of ways, with radial fractures observed in some LN-frozen sands, and needle-like ice crystals forming in slowly frozen clay-rich sediments. Suggestions for hydrate-bearing core preservation are presented.

An experimental point of view on hydration/solvation in halophilic proteins

PubMed Central

Talon, Romain; Coquelle, Nicolas; Madern, Dominique; Girard, Eric

2014-01-01

Protein-solvent interactions govern the behaviors of proteins isolated from extreme halophiles. In this work, we compared the solvent envelopes of two orthologous tetrameric malate dehydrogenases (MalDHs) from halophilic and non-halophilic bacteria. The crystal structure of the MalDH from the non-halophilic bacterium Chloroflexus aurantiacus (Ca MalDH) solved, de novo, at 1.7 Å resolution exhibits numerous water molecules in its solvation shell. We observed that a large number of these water molecules are arranged in pentagonal polygons in the first hydration shell of Ca MalDH. Some of them are clustered in large networks, which cover non-polar amino acid surface. The crystal structure of MalDH from the extreme halophilic bacterium Salinibacter ruber (Sr) solved at 1.55 Å resolution shows that its surface is strongly enriched in acidic amino acids. The structural comparison of these two models is the first direct observation of the relative impact of acidic surface enrichment on the water structure organization between a halophilic protein and its non-adapted counterpart. The data show that surface acidic amino acids disrupt pentagonal water networks in the hydration shell. These crystallographic observations are discussed with respect to halophilic protein behaviors in solution PMID:24600446
An experimental point of view on hydration/solvation in halophilic proteins.

PubMed

Talon, Romain; Coquelle, Nicolas; Madern, Dominique; Girard, Eric

2014-01-01

Protein-solvent interactions govern the behaviors of proteins isolated from extreme halophiles. In this work, we compared the solvent envelopes of two orthologous tetrameric malate dehydrogenases (MalDHs) from halophilic and non-halophilic bacteria. The crystal structure of the MalDH from the non-halophilic bacterium Chloroflexus aurantiacus (Ca MalDH) solved, de novo, at 1.7 Å resolution exhibits numerous water molecules in its solvation shell. We observed that a large number of these water molecules are arranged in pentagonal polygons in the first hydration shell of Ca MalDH. Some of them are clustered in large networks, which cover non-polar amino acid surface. The crystal structure of MalDH from the extreme halophilic bacterium Salinibacter ruber (Sr) solved at 1.55 Å resolution shows that its surface is strongly enriched in acidic amino acids. The structural comparison of these two models is the first direct observation of the relative impact of acidic surface enrichment on the water structure organization between a halophilic protein and its non-adapted counterpart. The data show that surface acidic amino acids disrupt pentagonal water networks in the hydration shell. These crystallographic observations are discussed with respect to halophilic protein behaviors in solution.
Structural stability of methane hydrate at high pressures

USGS Publications Warehouse

Shu, J.; Chen, X.; Chou, I-Ming; Yang, W.; Hu, Jiawen; Hemley, R.J.; Mao, Ho-kwang

2011-01-01

The structural stability of methane hydrate under pressure at room temperature was examined by both in-situ single-crystal and powder X-ray diffraction techniques on samples with structure types I, II, and H in diamond-anvil cells. The diffraction data for types II (sII) and H (sH) were refined to the known structures with space groups Fd3m and P63/mmc, respectively. Upon compression, sI methane hydrate transforms to the sII phase at 120 MPa, and then to the sH phase at 600 MPa. The sII methane hydrate was found to coexist locally with sI phase up to 500 MPa and with sH phase up to 600 MPa. The pure sH structure was found to be stable between 600 and 900 MPa. Methane hydrate decomposes at pressures above 3 GPa to form methane with the orientationally disordered Fm3m structure and ice VII (Pn3m). The results highlight the role of guest (CH4)-host (H2O) interactions in the stabilization of the hydrate structures under pressure.
Crystallization, dehydration and experimental phasing of WbdD, a bifunctional kinase and methyltransferase from Escherichia coli O9a

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagelueken, Gregor; Huang, Hexian; Harlos, Karl

2012-10-01

The optimization of WbdD crystals using a novel dehydration protocol and experimental phasing at 3.5 Å resolution by cross-crystal averaging followed by molecular replacement of electron density into a non-isomorphous 3.0 Å resolution native data set are reported. WbdD is a bifunctional kinase/methyltransferase that is responsible for regulation of lipopolysaccharide O antigen polysaccharide chain length in Escherichia coli serotype O9a. Solving the crystal structure of this protein proved to be a challenge because the available crystals belonging to space group I23 only diffracted to low resolution (>95% of the crystals diffracted to resolution lower than 4 Å and most onlymore » to 8 Å) and were non-isomorphous, with changes in unit-cell dimensions of greater than 10%. Data from a serendipitously found single native crystal that diffracted to 3.0 Å resolution were non-isomorphous with a lower (3.5 Å) resolution selenomethionine data set. Here, a strategy for improving poor (3.5 Å resolution) initial phases by density modification and cross-crystal averaging with an additional 4.2 Å resolution data set to build a crude model of WbdD is desribed. Using this crude model as a mask to cut out the 3.5 Å resolution electron density yielded a successful molecular-replacement solution of the 3.0 Å resolution data set. The resulting map was used to build a complete model of WbdD. The hydration status of individual crystals appears to underpin the variable diffraction quality of WbdD crystals. After the initial structure had been solved, methods to control the hydration status of WbdD were developed and it was thus possible to routinely obtain high-resolution diffraction (to better than 2.5 Å resolution). This novel and facile crystal-dehydration protocol may be useful for similar challenging situations.« less
Gas Hydrate Stability at Low Temperatures and High Pressures with Applications to Mars and Europa

NASA Technical Reports Server (NTRS)

Marion, G. M.; Kargel, J. S.; Catling, D. C.

2004-01-01

Gas hydrates are implicated in the geochemical evolution of both Mars and Europa [1- 3]. Most models developed for gas hydrate chemistry are based on the statistical thermodynamic model of van der Waals and Platteeuw [4] with subsequent modifications [5-8]. None of these models are, however, state-of-the-art with respect to gas hydrate/electrolyte interactions, which is particularly important for planetary applications where solution chemistry may be very different from terrestrial seawater. The objectives of this work were to add gas (carbon dioxide and methane) hydrate chemistries into an electrolyte model parameterized for low temperatures and high pressures (the FREZCHEM model) and use the model to examine controls on gas hydrate chemistries for Mars and Europa.
Neutron diffraction from aligned stacks of lipid bilayers using the WAND instrument

DOE PAGES

Marquardt, Drew; Frontzek, Matthias D.; Zhao, Yu; ...

2018-02-06

Neutron diffraction from aligned stacks of lipid bilayers is examined using the Wide-Angle Neutron Diffractometer (WAND), located at the High Flux Isotope Reactor, Oak Ridge, Tennessee, USA. Data were collected at different levels of hydration and neutron contrast by varying the relative humidity (RH) and H 2O/D 2O ratio from multi-bilayers of dioleoylphosphatidylcholine and sunflower phosphatidylcholine extract aligned on single-crystal silicon substrates. This work highlights the capabilites of a newly fabricated sample hydration cell, which allows the lipid bilayers to be hydrated with varying H/D ratios from the RH generated by saturated salt solutions, and also demonstrates WAND's capability asmore » an instrument suitable for the study of aligned lipid multi-bilayers.« less
Neutron diffraction from aligned stacks of lipid bilayers using the WAND instrument

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marquardt, Drew; Frontzek, Matthias D.; Zhao, Yu

Neutron diffraction from aligned stacks of lipid bilayers is examined using the Wide-Angle Neutron Diffractometer (WAND), located at the High Flux Isotope Reactor, Oak Ridge, Tennessee, USA. Data were collected at different levels of hydration and neutron contrast by varying the relative humidity (RH) and H 2O/D 2O ratio from multi-bilayers of dioleoylphosphatidylcholine and sunflower phosphatidylcholine extract aligned on single-crystal silicon substrates. This work highlights the capabilites of a newly fabricated sample hydration cell, which allows the lipid bilayers to be hydrated with varying H/D ratios from the RH generated by saturated salt solutions, and also demonstrates WAND's capability asmore » an instrument suitable for the study of aligned lipid multi-bilayers.« less
Two Types of Modeling of Subsurface Water

NASA Image and Video Library

2013-03-18

The Dynamic Albedo of Neutrons DAN instrument on NASA Mars rover Curiosity detects even very small amounts of water in the ground beneath the rover, primarily water bound into the crystal structure of hydrated minerals.
Crystal structures of Ca(ClO4)2·4H2O and Ca(ClO4)2·6H2O

PubMed Central

Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

2014-01-01

The title compounds, calcium perchlorate tetrahydrate and calcium perchlorate hexahydrate, were crystallized at low temperatures according to the solid–liquid phase diagram. The structure of the tetrahydrate consists of one Ca2+ cation eightfold coordinated in a square-antiprismatic fashion by four water molecules and four O atoms of four perchlorate tetrahedra, forming chains parallel to [01-1] by sharing corners of the ClO4 tetrahedra. The structure of the hexahydrate contains two different Ca2+ cations, each coordinated by six water molecules and two O atoms of two perchlorate tetrahedra, forming [Ca(H2O)6(ClO4)]2 dimers by sharing two ClO4 tetrahedra. The dimers are arranged in sheets parallel (001) and alternate with layers of non-coordinating ClO4 tetrahedra. O—H⋯O hydrogen bonds between the water molecules as donor and ClO4 tetrahedra and water molecules as acceptor groups lead to the formation of a three-dimensional network in the two structures. Ca(ClO4)2·6H2O was refined as a two-component inversion twin, with an approximate twin component ratio of 1:1 in each of the two structures. PMID:25552974
Liquefaction of Biopolymers: Solvent-free Liquids and Liquid Crystals from Nucleic Acids and Proteins.

PubMed

Liu, Kai; Ma, Chao; Göstl, Robert; Zhang, Lei; Herrmann, Andreas

2017-05-16

Biomacromolecules, such as nucleic acids, proteins, and virus particles, are persistent molecular entities with dimensions that exceed the range of their intermolecular forces hence undergoing degradation by thermally induced bond-scission upon heating. Consequently, for this type of molecule, the absence of a liquid phase can be regarded as a general phenomenon. However, certain advantageous properties usually associated with the liquid state of matter, such as processability, flowability, or molecular mobility, are highly sought-after features for biomacromolecules in a solvent-free environment. Here, we provide an overview over the design principles and synthetic pathways to obtain solvent-free liquids of biomacromolecular architectures approaching the topic from our own perspective of research. We will highlight the milestones in synthesis, including a recently developed general surfactant complexation method applicable to a large variety of biomacromolecules as well as other synthetic principles granting access to electrostatically complexed proteins and DNA. These synthetic pathways retain the function and structure of the biomacromolecules even under extreme, nonphysiological conditions at high temperatures in water-free melts challenging the existing paradigm on the role of hydration in structural biology. Under these conditions, the resulting complexes reveal their true potential for previously unthinkable applications. Moreover, these protocols open a pathway toward the assembly of anisotropic architectures, enabling the formation of solvent-free biomacromolecular thermotropic liquid crystals. These ordered biomaterials exhibit vastly different mechanical properties when compared to the individual building blocks. Beyond the preparative aspects, we will shine light on the unique potential applications and technologies resulting from solvent-free biomacromolecular fluids: From charge transport in dehydrated liquids to DNA electrochromism to biocatalysis in the absence of a protein hydration shell. Moreover, solvent-free biological liquids containing viruses can be used as novel storage and process media serving as a formulation technology for the delivery of highly concentrated bioactive compounds. We are confident that this new class of hybrid biomaterials will fuel further studies and applications of biomacromolecules beyond water and other solvents and in a much broader context than just the traditional physiological conditions.
Crystal structure and genesis of the hydrated analog of rastsvetaevite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rastsvetaeva, R. K., E-mail: ras@ns.crys.ras.ru; Aksenov, S. M.; Rozenberg, K. A.

2015-11-15

The crystal structure of the hydrated analog of the mineral rastsvetaevite (tentatively called “hydrorastsvetaevite”), which was found by A.P. Khomyakov in ultraagpaitic pegmatites at the Rasvumchorr Mountain of the Khibiny alkaline massif (Kola Peninsula), has been determined by single crystal X-ray diffraction. The trigonal unit-cell parameters are as follows: a = 14.2812(2) Å, c = 60.533(5) Å, V = 10691.54(3) Å{sup 3}, sp. gr. R3m. The structure was refined to R = 5.9% in the isotropic and anisotropic approximation of atomic displacement parameters based on 2068 ref lections with |F| > 3σ(F). “Hydrorastsvetaevite” is on the whole analogous to othermore » 24-layer representatives of the eudialyte group (called “megaeudialytes”), but is characterized by a high potassium content and is distinguished from other potassium-rich minerals (rastsvetaevite, davinciite, and andrianovite) by low sodium and alkaline-earth metal content, as well as by a high degree of hydration accompanied by the insertion of H{sub 3}O groups, which partially or completely replace large cations. The idealized formula of “hydrorastsvetaevite” (Z = 3) is (Na{sub 11}(H{sub 3}O){sub 11}K{sub 6}(H{sub 2}O){sub 1.5}Sr)Ca{sub 12}Fe{sub 3}Na{sub 2}MnZr{sub 6}Si{sub 52}O{sub 144}(OH){sub 4.5}C{sub l3.5}(H{sub 2}O){sub 0.5}. In alkaline pegmatites, “hydrorastsvetaevite” occurs as a secondary mineral developed from the original rastsvetaevite through decationation and hydration. The characteristic features of the genesis of eudialyte-group minerals containing potassium as a species-forming cation are discussed in terms of the concept of transformational mineral species.an]Mis||Original Russian Text © R.K. Rastsvetaeva, S.M. Aksenov, K.A. Rozenberg, 2015, published in Kristallografiya, 2015, Vol. 60, No. 6, pp. 897–905.« less
Characterization of dehydration and hydration behavior of calcium lactate pentahydrate and its anhydrate.

PubMed

Sakata, Yukoh; Shiraishi, Sumihiro; Otsuka, Makoto

2005-12-20

The use of calcium lactate pentahydrate (CLP) as an additional filler-binder for direct compaction of tablets has been reported to result in a short disintegration time and rapid drug release. The aim of this study was to understand the dehydration and hydration behavior of CLP and calcium lactate anhydrate (CLA) under various conditions of storage temperature and relative humidity. The removal and acquisition of crystal water were investigated by using differential scanning calorimetry (DSC), thermogravimetry-differential thermal analysis (TG-DTA), powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). The PXRD results indicated that CLP exists as a crystalline solid and CLA as an amorphous solid. Dehydration of CLP resulted in aggregated particles of CLA with an increase in average particle size. The dehydration and hydration kinetics of CLP were analyzed with the Hancock-Sharp equation on the basis of the isothermal DSC data. The dehydration of CLP followed a zero-order mechanism (Polany-Winger equation). In contrast, the surface roughness of CLA was significantly decreased by hydration. The hydration of CLA followed a three-dimensional diffusion model (Ginstling-Brounshtein equation).
Improvement of gas hydrate preservation by increasing compression pressure to simple hydrates of methane, ethane, and propane

NASA Astrophysics Data System (ADS)

Kida, Masato; Jin, Yusuke; Watanabe, Mizuho; Murayama, Tetsuro; Nagao, Jiro

2017-09-01

In this report, we describe the dissociation behavior of gas hydrate grains pressed at 1 and 6 MPa. Certain simple gas hydrates in powder form show anomalous preservation phenomenon under their thermodynamic unstable condition. Investigation of simple hydrates of methane, ethane, and propane reveals that high pressure applied to the gas hydrate particles enhances their preservation effects. Application of high pressure increases the dissociation temperature of methane hydrate and has a restrictive effect against the dissociation of ethane and propane hydrate grains. These improvements of gas hydrate preservation by increasing pressure to the initial gas hydrate particles imply that appropriate pressure applied to gas hydrate particles enhances gas hydrate preservation effects.
Water purification using organic salts

DOEpatents

Currier, Robert P.

2004-11-23

Water purification using organic salts. Feed water is mixed with at least one organic salt at a temperature sufficiently low to form organic salt hydrate crystals and brine. The crystals are separated from the brine, rinsed, and melted to form an aqueous solution of organic salt. Some of the water is removed from the aqueous organic salt solution. The purified water is collected, and the remaining more concentrated aqueous organic salt solution is reused.
Study on improving the heat storage property of Ba(OH)2·8H2O with paraffin

NASA Astrophysics Data System (ADS)

Cui, Kaixuan; Liu, Liqiang; Sun, Mingjie

2017-12-01

Barium hydroxide octahydrate is the crystalline hydration salt with the highest latent heat density within the phase change temperature interval of 0-120 °C and it has a broad application prospect as a phase-change material (PCM). Firstly, red copper test tube was used for the melting—solidification heat cycle experiment in this paper, which was verified by the corrosion experiment of barium hydroxide solution. After the thermogravimetric analysis, it is found that paraffin can effectively reduce the evaporation escape of barium hydroxide octahydrate crystal water within 100 °C. Repeated heat cycle experiments indicated that the paraffin with larger coverage mass fraction can reduce the inhibiting effect of barium hydroxide octahydrate crystal water more obviously. X-ray diffraction analysis indicated that the phase composition of the barium hydroxide octahydrate sample covered with 50 wt% paraffin nearly had no change, while the sample not covered with paraffin has the weight loss ratio of 34.67% and reacted with CO2 in the air, generating BaCO3. In summary, paraffin can not only inhibit the evaporation of crystal water, but also effectively isolate the air to prevent barium hydroxide octahydrate from denaturation. This greatly improved the practicability of barium hydroxide octahydrate as a PCM, laying a good foundation for the further application of barium hydroxide octahydrate.
Simulation and Characterization of Methane Hydrate Formation

NASA Astrophysics Data System (ADS)

Dhakal, S.; Gupta, I.

2017-12-01

The ever rising global energy demand dictates human endeavor to explore and exploit new and innovative energy sources. As conventional oil and gas reserves deplete, we are constantly looking for newer sources for sustainable energy. Gas hydrates have long been discussed as the next big energy resource to the earth. Its global occurrence and vast quantity of natural gas stored is one of the main reasons for such interest in its study and exploration. Gas hydrates are solid crystalline substances with trapped molecules of gas inside cage-like crystals of water molecules. Gases such as methane, ethane, propane and carbon dioxide can form hydrates but in natural state, methane hydrates are the most common. Subsurface geological conditions with high pressure and low temperature favor the formation and stability of gas hydrates. While the occurrence and potential of gas hydrates as energy source has long been studied, there are still gaps in knowledge, especially in the quantitative research of gas hydrate formation and reservoir characterization. This study is focused on exploring and understanding the geological setting in which gas hydrates are formed and the subsequent changes in rock characteristics as they are deposited. It involves the numerical simulation of methane gas flow through fault to form hydrates. The models are representative of the subsurface geologic setting of Gulf of Mexico with a fault through layers of shale and sandstone. Hydrate formation simulated is of thermogenic origin. The simulations are conducted using TOUGH+HYDRATE, a numerical code developed at the Lawrence Berkley National Laboratory for modeling multiphase flow through porous medium. Simulation results predict that as the gas hydrates form in the pores of the model, the porosity, permeability and other rock properties are altered. Preliminary simulation results have shown that hydrates begin to form in the fault zone and gradually in the sandstone layers. The increase in hydrate saturation is followed by decrease in the porosity and permeability of the reservoir rock. Sensitivities on flow rates of gas and water are simulated, using different reservoir properties, fault angles and grid sizes to study the properties of hydrate formation and accumulation in the subsurface.
Fundamentals and applications of gas hydrates.

PubMed

Koh, Carolyn A; Sloan, E Dendy; Sum, Amadeu K; Wu, David T

2011-01-01

Fundamental understanding of gas hydrate formation and decomposition processes is critical in many energy and environmental areas and has special importance in flow assurance for the oil and gas industry. These areas represent the core of gas hydrate applications, which, albeit widely studied, are still developing as growing fields of research. Discovering the molecular pathways and chemical and physical concepts underlying gas hydrate formation potentially can lead us beyond flowline blockage prevention strategies toward advancing new technological solutions for fuel storage and transportation, safely producing a new energy resource from natural deposits of gas hydrates in oceanic and arctic sediments, and potentially facilitating effective desalination of seawater. The state of the art in gas hydrate research is leading us to new understanding of formation and dissociation phenomena that focuses on measurement and modeling of time-dependent properties of gas hydrates on the basis of their well-established thermodynamic properties.
Gas hydrate inhibition by perturbation of liquid water structure

NASA Astrophysics Data System (ADS)

Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Lee, Kun-Hong

2015-06-01

Natural gas hydrates are icy crystalline materials that contain hydrocarbons, which are the primary energy source for this civilization. The abundance of naturally occurring gas hydrates leads to a growing interest in exploitation. Despite their potential as energy resources and in industrial applications, there is insufficient understanding of hydrate kinetics, which hinders the utilization of these invaluable resources. Perturbation of liquid water structure by solutes has been proposed to be a key process in hydrate inhibition, but this hypothesis remains unproven. Here, we report the direct observation of the perturbation of the liquid water structure induced by amino acids using polarized Raman spectroscopy, and its influence on gas hydrate nucleation and growth kinetics. Amino acids with hydrophilic and/or electrically charged side chains disrupted the water structure and thus provided effective hydrate inhibition. The strong correlation between the extent of perturbation by amino acids and their inhibition performance constitutes convincing evidence for the perturbation inhibition mechanism. The present findings bring the practical applications of gas hydrates significantly closer, and provide a new perspective on the freezing and melting phenomena of naturally occurring gas hydrates.
Gas hydrate inhibition by perturbation of liquid water structure.

PubMed

Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Lee, Kun-Hong

2015-06-17

Natural gas hydrates are icy crystalline materials that contain hydrocarbons, which are the primary energy source for this civilization. The abundance of naturally occurring gas hydrates leads to a growing interest in exploitation. Despite their potential as energy resources and in industrial applications, there is insufficient understanding of hydrate kinetics, which hinders the utilization of these invaluable resources. Perturbation of liquid water structure by solutes has been proposed to be a key process in hydrate inhibition, but this hypothesis remains unproven. Here, we report the direct observation of the perturbation of the liquid water structure induced by amino acids using polarized Raman spectroscopy, and its influence on gas hydrate nucleation and growth kinetics. Amino acids with hydrophilic and/or electrically charged side chains disrupted the water structure and thus provided effective hydrate inhibition. The strong correlation between the extent of perturbation by amino acids and their inhibition performance constitutes convincing evidence for the perturbation inhibition mechanism. The present findings bring the practical applications of gas hydrates significantly closer, and provide a new perspective on the freezing and melting phenomena of naturally occurring gas hydrates.
Quantum Mechanical Metric for Internal Cohesion in Cement Crystals

PubMed Central

Dharmawardhana, C. C.; Misra, A.; Ching, Wai-Yim

2014-01-01

Calcium silicate hydrate (CSH) is the main binding phase of Portland cement, the single most important structural material in use worldwide. Due to the complex structure and chemistry of CSH at various length scales, the focus has progressively turned towards its atomic level comprehension. We study electronic structure and bonding of a large subset of the known CSH minerals. Our results reveal a wide range of contributions from each type of bonding, especially hydrogen bonding, which should enable critical analysis of spectroscopic measurements and construction of realistic C-S-H models. We find the total bond order density (TBOD) as the ideal overall metric for assessing crystal cohesion of these complex materials and should replace conventional measures such as Ca:Si ratio. A rarely known orthorhombic phase Suolunite is found to have higher cohesion (TBOD) in comparison to Jennite and Tobermorite, which are considered the backbone of hydrated Portland cement. PMID:25476741

Thermodynamic data for modeling acid mine drainage problems: compilation and estimation of data for selected soluble iron-sulfate minerals

USGS Publications Warehouse

Hemingway, Bruch S.; Seal, Robert R.; Chou, I-Ming

2002-01-01

Enthalpy of formation, Gibbs energy of formation, and entropy values have been compiled from the literature for the hydrated ferrous sulfate minerals melanterite, rozenite, and szomolnokite, and a variety of other hydrated sulfate compounds. On the basis of this compilation, it appears that there is no evidence for an excess enthalpy of mixing for sulfate-H2O systems, except for the first H2O molecule of crystallization. The enthalpy and Gibbs energy of formation of each H2O molecule of crystallization, except the first, in the iron(II) sulfate - H2O system is -295.15 and -238.0 kJ?mol-1, respectively. The absence of an excess enthalpy of mixing is used as the basis for estimating thermodynamic values for a variety of ferrous, ferric, and mixed-valence sulfate salts of relevance to acid-mine drainage systems.
cis-Dichloridobis(5,5′-dimethyl-2,2′-bipyridine)manganese(II) 2.5-hydrate

PubMed Central

Lopes, Lívia Batista; Corrêa, Charlane Cimini; Diniz, Renata

2011-01-01

The metal site in the title compound [MnCl2(C12H12N2)2]·2.5H2O has a distorted octahedral geometry, coordinated by four N atoms of two 5,5′-dimethyl-2,2′-dipyridine ligands and two Cl atoms. Two and a half water molecules of hydration per complex unit are observed in the crystal structure. The compounds extend along the c axis with O—H⋯Cl, O—H⋯O, C—H⋯Cl and C—H⋯O hydrogen bonds and π–π interactions [centroid-centroid distance = 3.70 (2) Å] contributing substantially to the crystal packing. The Mn and one of the water O atoms, the latter being half-occupied, are located on special positions, in this case a rotation axis of order 2. PMID:21836893
The Temperature Dependence of the Partition of CH4 and C2H6 in Structure I Hydrates

NASA Astrophysics Data System (ADS)

Cheng, H.; Lu, W.

2017-12-01

At present, we mainly use hydrocarbon gas and carbon isotope composition to determine the gas source of natural gas hydrate. Judging the type of gas source plays a key role in the evaluation of hydrate reservoirs, but there is still controversy over this approach. Considering the crystal properties of hydrate, the process of aggregation and decomposition of natural gas hydrates may have an important effect on the gas composition. We used CH4 (C1), C2H6 (C2) and their mixture as gas sources to synthesize hydrates from aqueous solution in high-pressure capillary tubes. Gas concentration in hydrates grew at different temperatures was measured with quantitative Raman spectroscopy. The results show that concentrations of gas in pure methane and pure ethane hydrates increase with temperature. The results of the mixture are similar to pure gas below 288.15 K, the concentration of C1 in small cages (SC, 512) slowly increased, but the competitive relationship between methane and ethane in large cages (LC, 51262) become obvious after 288.15 K. From 278.15 K to 294.15 K, the value of C1/C2 decreased from 26.38 to 6.61, gradually closing to the original gas composition of 4. We find that gas hydrates are more likely to gather C1 when they accumulate. The lower the temperature is, the more obvious it will be, and the closer the value of C1/C2 is to the microbial gases.
Multi-property characterization chamber for geophysical-hydrological investigations of hydrate bearing sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seol, Yongkoo, E-mail: Yongkoo.Seol@netl.doe.gov; Choi, Jeong-Hoon; Dai, Sheng

With the increase in the interest of producing natural gas from methane hydrates as well as potential risks of massive hydrate dissociation in the context of global warming, studies have recently shifted from pure hydrate crystals to hydrates in sediments. Such a research focus shift requires a series of innovative laboratory devices that are capable of investigating various properties of hydrate-bearing sediments (HBS). This study introduces a newly developed high pressure testing chamber, i.e., multi-property characterization chamber (MPCC), that allows simultaneous investigation of a series of fundamental properties of HBS, including small-strain stiffness (i.e., P- and S-waves), shear strength, large-strainmore » deformation, stress-volume responses, and permeability. The peripheral coolant circulation system of the MPCC permits stable and accurate temperature control, while the core holder body, made of aluminum, enables X-ray computer tomography scanning to be easily employed for structural and morphological characterization of specimens. Samples of hydrate-bearing sediments are held within a rubber sleeve inside the chamber. The thick sleeve is more durable and versatile than thin membranes while also being much softer than oedometer-type chambers that are incapable of enabling flow tests. Bias introduced by the rubber sleeve during large deformation tests are also calibrated both theoretically and experimentally. This system provides insight into full characterization of hydrate-bearing sediments in the laboratory, as well as pressure core technology in the field.« less
Entropic Description of Gas Hydrate Ice-Liquid Equilibrium via Enhanced Sampling of Coexisting Phases

NASA Astrophysics Data System (ADS)

Małolepsza, Edyta; Kim, Jaegil; Keyes, Tom

2015-05-01

Metastable β ice holds small guest molecules in stable gas hydrates, so its solid-liquid equilibrium is of interest. However, aqueous crystal-liquid transitions are very difficult to simulate. A new molecular dynamics algorithm generates trajectories in a generalized N P T ensemble and equilibrates states of coexisting phases with a selectable enthalpy. With replicas spanning the range between β ice and liquid water, we find the statistical temperature from the enthalpy histograms and characterize the transition by the entropy, introducing a general computational procedure for first-order transitions.
Clathrate hydrate formation in amorphous cometary ice analogs in vacuo

NASA Technical Reports Server (NTRS)

Blake, David; Allamandola, Louis; Sandford, Scott; Hudgins, Doug; Freund, Friedemann

1991-01-01

Experiments conducted in clathrate hydrates with a modified electron microscope have demonstrated the possibility of such compounds' formation during the warming of vapor-deposited amorphous ices in vacuo, through rearrangements in the solid state. Subsolidus crystallization of compositionally complex amorphous ices may therefore be a general and ubiquitous process. Phase separations and microporous textures thus formed may be able to account for such anomalous cometary phenomena as the release of gas at large radial distances from the sun and the retention of volatiles to elevated temperatures.
Entropic description of gas hydrate ice/liquid equilibrium via enhanced sampling of coexisting phases

DOE PAGES

Malolepsza, Edyta; Kim, Jaegil; Keyes, Tom

2015-04-28

Metastable β ice holds small guest molecules in stable gas hydrates, so its solid/liquid equilibrium is of interest. However, aqueous crystal/liquid transitions are very difficult to simulate. A new MD algorithm generates trajectories in a generalized NPT ensemble and equilibrates states of coexisting phases with a selectable enthalpy. Furthermore, with replicas spanning the range between β ice and liquid water we find the statistical temperature from the enthalpy histograms and characterize the transition by the entropy, introducing a general computational procedure for first-order transitions.
Scanning electron microscopy investigations of laboratory-grown gas clathrate hydrates formed from melting ice, and comparison to natural hydrates

USGS Publications Warehouse

Stern, L.A.; Kirby, S.H.; Circone, S.; Durham, W.B.

2004-01-01

Scanning electron microscopy (SEM) was used to investigate grain texture and pore structure development within various compositions of pure sI and sII gas hydrates synthesized in the laboratory, as well as in natural samples retrieved from marine (Gulf of Mexico) and permafrost (NW Canada) settings. Several samples of methane hydrate were also quenched after various extents of partial reaction for assessment of mid-synthesis textural progression. All laboratory-synthesized hydrates were grown under relatively high-temperature and high-pressure conditions from rounded ice grains with geometrically simple pore shapes, yet all resulting samples displayed extensive recrystallization with complex pore geometry. Growth fronts of mesoporous methane hydrate advancing into dense ice reactant were prevalent in those samples quenched after limited reaction below and at the ice point. As temperatures transgress the ice point, grain surfaces continue to develop a discrete "rind" of hydrate, typically 5 to 30 ??m thick. The cores then commonly melt, with rind microfracturing allowing migration of the melt to adjacent grain boundaries where it also forms hydrate. As the reaction continues under progressively warmer conditions, the hydrate product anneals to form dense and relatively pore-free regions of hydrate grains, in which grain size is typically several tens of micrometers. The prevalence of hollow, spheroidal shells of hydrate, coupled with extensive redistribution of reactant and product phases throughout reaction, implies that a diffusion-controlled shrinking-core model is an inappropriate description of sustained hydrate growth from melting ice. Completion of reaction at peak synthesis conditions then produces exceptional faceting and euhedral crystal growth along exposed pore walls. Further recrystallization or regrowth can then accompany even short-term exposure of synthetic hydrates to natural ocean-floor conditions, such that the final textures may closely mimic those observed in natural samples of marine origin. Of particular note, both the mesoporous and highly faceted textures seen at different stages during synthetic hydrate growth were notably absent from all examined hydrates recovered from a natural marine-environment setting.
In situ Low-temperature Pair Distribution Function (PDF) Analysis of CH4 and CO2 Hydrates

NASA Astrophysics Data System (ADS)

Cladek, B.; Everett, M.; McDonnell, M.; Tucker, M.; Keffer, D.; Rawn, C.

2017-12-01

Gas hydrates occur in ocean floor and sub-surface permafrost deposits and are stable at moderate to high pressures and low temperatures. They are a clathrate structure composed of hydrogen bonded water cages that accommodate a wide variety of guest molecules. CO2 and CH4 hydrates both crystallize as the cubic sI hydrate and can form a solid solution. Natural gas hydrates are interesting as a potential methane source and for CO2 sequestration. Long-range diffraction studies on gas hydrates give valuable structural information but do not provide a detailed understanding of the disordered gas molecule interactions with the host lattice. In-situ low temperature total scattering experiments combined with pair distribution function (PDF) analysis are used to investigate the gas molecule motions and guest-cage interactions. CO2 and methane hydrates exhibit different decomposition behavior, and CO2 hydrate has a smaller lattice parameter despite it being a relatively larger molecule. Total scattering studies characterizing both the short- and long-range order simultaneously help to elucidate the structural source of these phenomena. Low temperature neutron total scattering data were collected using the Nanoscale Ordered MAterials Diffractometer (NOMAD) beamline at the Spallation Neutron Source (SNS) on CO2 and CH4 hydrates synthesized with D2O. Guest molecule motion within cages and interactions between gases and cages are investigated through the hydrate stability and decomposition regions. Data were collected from 2-80 K at a pressure of 55 mbar on CO2 and CH4 hydrates, and from 80-270 K at 25 bar on CH4 hydrate. The hydrate systems were modeled with classical molecular dynamic (MD) simulations to provide an analysis of the total energy into guest-guest, guest-host and host-host contributions. Combined Reitveld and Reverse Monte Carlo (RMC) structure refinement were used to fit models of the data. This combined modeling and simulation characterizes the effects of CO2 and CH4 as guest molecules on the structure and decomposition of gas hydrates. Structure and thermodynamic studies will provide a more comprehensive understanding of CO2-CH4 solid solutions, exchange kinetics, and implications on hydrate structure.
A Simple Sonication Improves Protein Signal in Matrix-Assisted Laser Desorption Ionization Imaging

NASA Astrophysics Data System (ADS)

Lin, Li-En; Su, Pin-Rui; Wu, Hsin-Yi; Hsu, Cheng-Chih

2018-02-01

Proper matrix application is crucial in obtaining high quality matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI). Solvent-free sublimation was essentially introduced as an approach of homogeneous coating that gives small crystal size of the organic matrix. However, sublimation has lower extraction efficiency of analytes. Here, we present that a simple sonication step after the hydration in standard sublimation protocol significantly enhances the sensitivity of MALDI MSI. This modified procedure uses a common laboratory ultrasonicator to immobilize the analytes from tissue sections without noticeable delocalization. Improved imaging quality with additional peaks above 10 kDa in the spectra was thus obtained upon sonication treatment. [Figure not available: see fulltext.
Mechanical resilience and cementitious processes in Imperial Roman architectural mortar.

PubMed

Jackson, Marie D; Landis, Eric N; Brune, Philip F; Vitti, Massimo; Chen, Heng; Li, Qinfei; Kunz, Martin; Wenk, Hans-Rudolf; Monteiro, Paulo J M; Ingraffea, Anthony R

2014-12-30

The pyroclastic aggregate concrete of Trajan's Markets (110 CE), now Museo Fori Imperiali in Rome, has absorbed energy from seismic ground shaking and long-term foundation settlement for nearly two millenia while remaining largely intact at the structural scale. The scientific basis of this exceptional service record is explored through computed tomography of fracture surfaces and synchroton X-ray microdiffraction analyses of a reproduction of the standardized hydrated lime-volcanic ash mortar that binds decimeter-sized tuff and brick aggregate in the conglomeratic concrete. The mortar reproduction gains fracture toughness over 180 d through progressive coalescence of calcium-aluminum-silicate-hydrate (C-A-S-H) cementing binder with Ca/(Si+Al) ≈ 0.8-0.9 and crystallization of strätlingite and siliceous hydrogarnet (katoite) at ≥ 90 d, after pozzolanic consumption of hydrated lime was complete. Platey strätlingite crystals toughen interfacial zones along scoria perimeters and impede macroscale propagation of crack segments. In the 1,900-y-old mortar, C-A-S-H has low Ca/(Si+Al) ≈ 0.45-0.75. Dense clusters of 2- to 30-µm strätlingite plates further reinforce interfacial zones, the weakest link of modern cement-based concrete, and the cementitious matrix. These crystals formed during long-term autogeneous reaction of dissolved calcite from lime and the alkali-rich scoriae groundmass, clay mineral (halloysite), and zeolite (phillipsite and chabazite) surface textures from the Pozzolane Rosse pyroclastic flow, erupted from the nearby Alban Hills volcano. The clast-supported conglomeratic fabric of the concrete presents further resistance to fracture propagation at the structural scale.
Vibrational Properties of Anhydrous and Partially Hydrated Uranyl Fluoride

DOE PAGES

Anderson, Brian B.; Kirkegaard, Marie C.; Miskowiec, Andrew J.; ...

2017-01-01

Uranyl fluoride (UO 2F 2) is a hygroscopic powder with two main structural phases: an anhydrous crystal and a partially hydrated crystal of the same R¯3m symmetry. The formally closed-shell electron structure of anhydrous UO 2F 2 is amenable to density functional theory calculations. We use density functional perturbation theory (DFPT) to calculate the vibrational frequencies of the anhydrous crystal structure and employ complementary inelastic neutron scattering and temperature-dependent Raman scattering to validate those frequencies. As a model closed-shell actinide, we investigated the effect of LDA, GGA, and non-local vdW functionals as well as the spherically-averaged Hubbard +U correction onmore » vibrational frequencies, electronic structure, and geometry of anhydrous UO 2F 2. A particular choice of U eff = 5.5 eV yields the correct U Oyl bond distance and vibrational frequencies for the characteristic Eg and A1g modes that are within the resolution of experiment. Inelastic neutron scattering and Raman scattering suggest a degree of water coupling to the lattice vibrations in the more experimentally accessible partially hydrated UO 2F 2 system, with the symmetric O-U-O stretching vibration shifted approximately 47 cm -1 lower in energy compared to the anhydrous structure. Evidence of water interaction with the uranyl ion is present from a two-peak decomposition of the uranyl stretching vibration in the Raman spectra and anion hydrogen stretching vibrations in the inelastic neutron scattering spectra. A first-order dehydration phase transition temperature is definitively identified to be 125 °C using temperature-dependent Raman scattering.« less
A catalytic metal ion interacts with the cleavage site G•U wobble in the HDV ribozyme†

PubMed Central

Chen, Jui-Hui; Gong, Bo; Bevilacqua, Philip C.; Carey, Paul R.; Golden, Barbara L.

2009-01-01

The HDV ribozyme self-cleaves by a chemical mechanism involving general acid-base catalysis to generate a 2′,3′-cyclic phosphate and a 5′-hydroxyl termini. Biochemical studies from several laboratories have implicated C75 as the general acid and hydrated magnesium as the general base. We have previously shown that C75 has a pKa shifted > 2 pH units toward neutrality [Gong, B., Chen, J. H., Chase, E., Chadalavada, D. M., Yajima, R., Golden, B. L., Bevilacqua, P. C., and Carey, P. R. (2007) J. Am. Chem. Soc. 129, 13335–13342.], while in crystal structures, it is well-positioned for proton transfer. However no crystallographic evidence for a hydrated magnesium poised to serve as a general base in the reaction has been observed in high-resolution crystal structures of various reaction states and mutants. Herein, we use solution kinetic experiments and parallel Raman crystallographic studies to examine the effects of pH on rate and Mg2+-binding properties of wild-type and 7-deazaguanosine mutants of the HDV ribozyme. These data suggest that a previously-unobserved hydrated magnesium ion interacts with the N7 of the cleavage site G•U wobble base pair. Integrating this metal ion binding site with the available crystal structures provides a new three-dimensional model for the active site of the ribozyme that accommodates all available biochemical data and appears competent for catalysis. The position of this metal is consistent with a role of a magnesium-bound hydroxide as a general base as dictated by biochemical data. PMID:19178151
Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

PubMed Central

Landis, Eric N.; Brune, Philip F.; Vitti, Massimo; Chen, Heng; Li, Qinfei; Kunz, Martin; Wenk, Hans-Rudolf; Monteiro, Paulo J. M.; Ingraffea, Anthony R.

2014-01-01

The pyroclastic aggregate concrete of Trajan’s Markets (110 CE), now Museo Fori Imperiali in Rome, has absorbed energy from seismic ground shaking and long-term foundation settlement for nearly two millenia while remaining largely intact at the structural scale. The scientific basis of this exceptional service record is explored through computed tomography of fracture surfaces and synchroton X-ray microdiffraction analyses of a reproduction of the standardized hydrated lime–volcanic ash mortar that binds decimeter-sized tuff and brick aggregate in the conglomeratic concrete. The mortar reproduction gains fracture toughness over 180 d through progressive coalescence of calcium–aluminum-silicate–hydrate (C-A-S-H) cementing binder with Ca/(Si+Al) ≈ 0.8–0.9 and crystallization of strätlingite and siliceous hydrogarnet (katoite) at ≥90 d, after pozzolanic consumption of hydrated lime was complete. Platey strätlingite crystals toughen interfacial zones along scoria perimeters and impede macroscale propagation of crack segments. In the 1,900-y-old mortar, C-A-S-H has low Ca/(Si+Al) ≈ 0.45–0.75. Dense clusters of 2- to 30-µm strätlingite plates further reinforce interfacial zones, the weakest link of modern cement-based concrete, and the cementitious matrix. These crystals formed during long-term autogeneous reaction of dissolved calcite from lime and the alkali-rich scoriae groundmass, clay mineral (halloysite), and zeolite (phillipsite and chabazite) surface textures from the Pozzolane Rosse pyroclastic flow, erupted from the nearby Alban Hills volcano. The clast-supported conglomeratic fabric of the concrete presents further resistance to fracture propagation at the structural scale. PMID:25512521
A catalytic metal ion interacts with the cleavage Site G.U wobble in the HDV ribozyme.

PubMed

Chen, Jui-Hui; Gong, Bo; Bevilacqua, Philip C; Carey, Paul R; Golden, Barbara L

2009-02-24

The HDV ribozyme self-cleaves by a chemical mechanism involving general acid-base catalysis to generate 2',3'-cyclic phosphate and 5'-hydroxyl termini. Biochemical studies from several laboratories have implicated C75 as the general acid and hydrated magnesium as the general base. We have previously shown that C75 has a pK(a) shifted >2 pH units toward neutrality [Gong, B., Chen, J. H., Chase, E., Chadalavada, D. M., Yajima, R., Golden, B. L., Bevilacqua, P. C., and Carey, P. R. (2007) J. Am. Chem. Soc. 129, 13335-13342], while in crystal structures, it is well-positioned for proton transfer. However, no evidence for a hydrated magnesium poised to serve as a general base in the reaction has been observed in high-resolution crystal structures of various reaction states and mutants. Herein, we use solution kinetic experiments and parallel Raman crystallographic studies to examine the effects of pH on the rate and Mg(2+) binding properties of wild-type and 7-deazaguanosine mutants of the HDV ribozyme. These data suggest that a previously unobserved hydrated magnesium ion interacts with N7 of the cleavage site G.U wobble base pair. Integrating this metal ion binding site with the available crystal structures provides a new three-dimensional model for the active site of the ribozyme that accommodates all available biochemical data and appears competent for catalysis. The position of this metal is consistent with a role of a magnesium-bound hydroxide as a general base as dictated by biochemical data.
Protein hydration in solution: Experimental observation by x-ray and neutron scattering

PubMed Central

Svergun, D. I.; Richard, S.; Koch, M. H. J.; Sayers, Z.; Kuprin, S.; Zaccai, G.

1998-01-01

The structure of the protein–solvent interface is the subject of controversy in theoretical studies and requires direct experimental characterization. Three proteins with known atomic resolution crystal structure (lysozyme, Escherichia coli thioredoxin reductase, and protein R1 of E. coli ribonucleotide reductase) were investigated in parallel by x-ray and neutron scattering in H2O and D2O solutions. The analysis of the protein–solvent interface is based on the significantly different contrasts for the protein and for the hydration shell. The results point to the existence of a first hydration shell with an average density ≈10% larger than that of the bulk solvent in the conditions studied. Comparisons with the results of other studies suggest that this may be a general property of aqueous interfaces. PMID:9482874
How does hydroxyl introduction influence the double helical structure: the stabilization of an altritol nucleic acid:ribonucleic acid duplex

PubMed Central

Ovaere, Margriet; Sponer, Jiri; Sponer, Judit E.; Herdewijn, Piet; Van Meervelt, Luc

2012-01-01

Altritol nucleic acids (ANAs) are a promising new tool in the development of artificial small interfering ribonucleic acids (siRNAs) for therapeutical applications. To mimic the siRNA:messenger RNA (mRNA) interactions, the crystal structure of the ANA:RNA construct a(CCGUAAUGCC-P):r(GGCAUUACGG) was determined to 1.96 Å resolution which revealed the hybrid to form an A-type helix. As this A-form is a major requirement in the RNAi process, this crystal structure confirms the potential of altritol-modified siRNAs. Moreover, in the ANA strands, a new type of intrastrand interactions was found between the O2′ hydroxyl group of one residue and the sugar ring O4′ atom of the next residue. These interactions were further investigated by quantum chemical methods. Besides hydration effects, these intrastrand hydrogen bonds may also contribute to the stability of ANA:RNA duplexes. PMID:22638588
Dynamics of Water in Gemini Surfactant-Based Lyotropic Liquid Crystals

DOE PAGES

McDaniel, Jesse G.; Mantha, Sriteja; Yethiraj, Arun

2016-09-26

The dynamics of water confined to nanometer-sized domains is important in a variety of applications ranging from proton exchange membranes to crowding effects in biophysics. In this work we study the dynamics of water in gemini surfactant-based lyotropic liquid crystals (LLCs) using molecular dynamics simulations. These systems have well characterized morphologies, e.g., hexagonal, gyroid, and lamellar, and the surfaces of the confining regions can be controlled by modifying the headgroup of the surfactants. This allows one to study the effect of topology, functionalization, and interfacial curvature on the dynamics of confined water. Through analysis of the translational diffusion and rotationalmore » relaxation we conclude that the hydration level and resulting confinement lengthscale is the predominate determiner of the rates of water dynamics, and other effects, namely surface functionality and curvature, are largely secondary. In conclusion, this novel analysis of the water dynamics in these LLC systems provides an important comparison for previous studies of water dynamics in lipid bilayers and reverse micelles.« less
Crystal structure of tin(II) perchlorate trihydrate

PubMed Central

Hennings, Erik; Schmidt, Horst; Köhler, Martin; Voigt, Wolfgang

2014-01-01

The title compound, [Sn(H2O)3](ClO4)2, was synthesized by the redox reaction of copper(II) perchlorate hexahydrate and metallic tin in perchloric acid. Both the trigonal–pyramidal [Sn(H2O)3]2+ cations and tetrahedral perchlorate anions lie on crystallographic threefold axes. In the crystal, the cations are linked to the anions by O—H⋯O hydrogen bonds, generating (001) sheets. PMID:25552969
Methane hydrate formation in confined nanospace can surpass nature

DOE PAGES

Casco, Mirian E.; Silvestre-Albero, Joaquín; Ramírez-Cuesta, Anibal J.; ...

2015-03-02

Natural methane hydrates are believed to be the largest source of hydrocarbons on Earth. These structures are formed in specific locations such as deep-sea sediments and the permafrost based on demanding conditions of high pressure and low temperature. We report that, by taking advantage of the confinement effects on nanopore space, synthetic methane hydrates grow under mild conditions (3.5 MPa and 2 degrees C), with faster kinetics (within minutes) than nature, fully reversibly and with a nominal stoichiometry that mimics nature. Furthermore, the formation of the hydrate structures in nanospace and their similarity to natural hydrates is confirmed using inelasticmore » neutron scattering experiments and synchrotron X-ray powder diffraction. Our findings may be a step towards the application of a smart synthesis of methane hydrates in energy-demanding applications (for example, transportation).« less

Molecular dynamics studies of water deposition on hematite surfaces

NASA Astrophysics Data System (ADS)

Kvamme, Bjørn; Kuznetsova, Tatiana; Haynes, Martin

2012-12-01

The interest in carbon dioxide for enhanced oil recovery is increasing proportional to the decrease in naturally driven oil production and also due to the increasing demand for reduced emission of carbon dioxide to the atmosphere. Transport of carbon dioxide in offshore pipelines involves high pressure and low temperatures which may lead to the formation of hydrate between residual water dissolved in carbon dioxide. The critical question is whether the water at some condition of temperature and pressure will drop out as liquid droplets or as water adsorbed on the surfaces of the pipeline and then subsequently form hydrates heterogeneously. In this work we have used the 6-311G basis set with B3LYP to estimate the charge distribution of different sizes of hematite crystals. The obtained surface charge distribution were kept unchanged while the inner charge distribution where scaled so as to result in an overall neutral crystal. These rust particles were embedded in water and chemical potential for adsorbed water molecules were estimated through thermodynamic integration and compared to similar estimates for same size water cluster. Estimated values of water chemical potentials indicate that it is thermodynamically favorable for water to adsorb on hematite, and that evaluation of potential carbon dioxide hydrate formation conditions and kinetics should be based this sequence of processes.
A coordination chemistry study of hydrated and solvated cationic vanadium ions in oxidation states +III, +IV, and +V in solution and solid state

PubMed Central

Krakowiak, Joanna; Lundberg, Daniel

2012-01-01

The coordination chemistry of hydrated and solvated vanadium(III), oxovanadium(IV), and dioxovanadium(V) ions in the oxygen donor solvents water, dimethylsulfoxide (dmso) and N,N′-dimethylpropyleneurea (dmpu) has been studied in solution by EXAFS and large angle X-ray scattering (LAXS) and in solid state by single crystal X-ray diffraction and EXAFS. The hydrated vanadium(III) ion has a regular octahedral configuration with a mean V-O bond distance of 1.99 Å. In the hydrated and dimethylsulfoxide solvated oxovanadium(IV) ions vanadium binds strongly to an oxo group at ca. 1.6 Å. The solvent molecule trans to the oxo group is very weakly bound, at ca. 2.2 Å, while the remaining four solvent molecules, with a mean V-O bond distance of 2.0 Å, form a plane slightly below the vanadium atom; the mean O=V-Operp bond angle is ca. 98°. In the dmpu solvated oxovanadium(IV) ion, the space demanding properties of the dmpu molecule leaving no solvent molecule in the trans position to the oxo group which reduces the coordination number to 5. The O=V-O bond angle is consequently much larger, 106°, and the mean V=O and V-O bond distances decrease to 1.58 and 1.97 Å, respectively. The hydrated and dimethylsulfoxide solvated dioxovanadium(V) ions display a very distorted octahedral configuration with the oxo groups in cis position with mean V=O bond distances of 1.6 Å and a O=V=O bond angle of ca. 105°. The solvent molecules trans to the oxo groups are weakly bound, at ca. 2.2 Å, while the remaining two have bond distances of 2.02 Å. The experimental studies of the coordination chemistry of hydrated and solvated vanadium(III,IV,V) ions are complemented by summarizing previously reported crystal structures to yield a comprehensive description of the coordination chemistry of vanadium with oxygen donor ligands. PMID:22950803
[Raman Characterization of Hydrate Crystal Structure Influenced by Mine Gas Concentration].

PubMed

Zhang, Bao-yong; Zhou, Hong-ji; Wu, Qiang; Gao, Xia

2016-01-01

CH4 /C2H6/N2 mixed hydrate formation experiments were performed at 2 degrees C and 5 MPa for three different mine gas concentrations (CH4/C2H6/N2, G1 = 54 : 36 : 10, G2 = 67.5 : 22.5 : 10, G3 = 81 : 9 : 10). Raman spectra for hydration products were obtained by using Microscopic Raman Spectrometer. Hydrate structure is determined by the Raman shift of symmetric C-C stretching vibration mode of C2H6 in the hydrate phase. This work is focused on the cage occupancies and hydration numbers, calculated by the fitting methods of Raman peaks. The results show that structure I (s I) hydrate forms in the G1 and G2 gas systems, while structure II (s II) hydrate forms in the G3 gas system, concentration variation of C2H6 in the gas samples leads to a change in hydrate structure from s I to s II; the percentages of CH4 and C2H6 in s I hydrate phase are less affected by the concentration of gas samples, the percentages of CH4 are respectively 34.4% and 35.7%, C2H6 are respectively 64.6% and 63.9% for gas systems of G1 and G2, the percentages of CH4 and 2 H6 are respectively 73.5% and 22.8% for gas systems of G3, the proportions of object molecules largely depend on the hydrate structure; CH4 and C2H6 molecules occupy 98%, 98% and 92% of the large cages and CH4 molecules occupy 80%, 60% and 84% of the small cages for gas systems of G1, G2 and G3, respectively; additionally, N2 molecules occupy less than 5% of the small cages is due to its weak adsorption ability and the lower partial pressure.
In-situ Micro-structural Studies of Gas Hydrate Formation in Sedimentary Matrices

NASA Astrophysics Data System (ADS)

Kuhs, Werner F.; Chaouachi, Marwen; Falenty, Andrzej; Sell, Kathleen; Schwarz, Jens-Oliver; Wolf, Martin; Enzmann, Frieder; Kersten, Michael; Haberthür, David

2015-04-01

The formation process of gas hydrates in sedimentary matrices is of crucial importance for the physical and transport properties of the resulting aggregates. This process has never been observed in-situ with sub-micron resolution. Here, we report on synchrotron-based micro-tomographic studies by which the nucleation and growth processes of gas hydrate were observed in different sedimentary matrices (natural quartz, glass beds with different surface properties, with and without admixtures of kaolinite and montmorillonite) at varying water saturation. The nucleation sites can be easily identified and the growth pattern is clearly established. In under-saturated sediments the nucleation starts at the water-gas interface and proceeds from there to form predominantly isometric single crystals of 10-20μm size. Using a newly developed synchrotron-based method we have determined the crystallite size distributions (CSD) of the gas hydrate in the sedimentary matrix confirming in a quantitative and statistically relevant manner the impressions from the tomographic reconstructions. It is noteworthy that the CSDs from synthetic hydrates are distinctly smaller than those of natural gas hydrates [1], which suggest that coarsening processes take place in the sedimentary matrix after the initial hydrate formation. Understanding the processes of formation and coarsening may eventually permit the determination of the age of gas hydrates in sedimentary matrices [2], which are largely unknown at present. Furthermore, the full micro-structural picture and its evolution will enable quantitative digital rock physics modeling to reveal poroelastic properties and in this way to support the exploration and exploitation of gas hydrate resources in the future. [1] Klapp S.A., Hemes S., Klein H., Bohrmann G., McDonald I., Kuhs W.F. Grain size measurements of natural gas hydrates. Marine Geology 2010; 274(1-4):85-94. [2] Klapp S.A., Klein H, Kuhs W.F. First determination of gas hydrate crystallite size distribution using high-energy synchrotron radiation. Geophys.Res.Letters, 2007 ; 34 : L13608, DOI:10.1029/2006GL029134
Structural characterization and cytotoxicity studies of different forms of a combretastatin A4 analogue

NASA Astrophysics Data System (ADS)

de Figueiredo, Laysa P.; Ibiapino, Amanda L.; do Amaral, Daniel N.; Ferraz, Letícia S.; Rodrigues, Tiago; Barreiro, Eliezer J.; Lima, Lídia M.; Ferreira, Fabio F.

2017-11-01

It is well known that combretastatin A4 (CA-4), which is a natural stilbene isolated from Combretum caffrum, is used to inhibit angiogenesis. However, depending on the dose administered to the patient, it can cause some side-effects. Herein, we present the synthesis and structural characterization of a novel N-acylhydrazone derivative - LASSBio-1735 - a CA-4 analogue. LASSBio-1735 has displayed in vitro antiproliferative activity against HL-60 (human leukemia), SF-295 (human glioblastoma), MDA-MB435 (melanoma) and HCT-8 (ileocecal adenocarcinoma) tumor cells. We found different hydration levels in two batches of the as-synthesized compound. As a consequence, we could successfully determine the crystal structures - by using X-ray powder diffraction data and a simulated annealing procedure - of the anhydrous and hydrated forms. The effects on cell viability of anhydrous and hydrated forms of LASSBio-1735 were comparatively evaluated in different tumor cell lines, and the hydrated form exhibited higher cytotoxicity in human leukemia K562 cells. These findings lead us to perform a quantitative phase analysis on one of the samples and may shed some light on the search for possible new solvates and/or hydrates.
Noncovalent Polymerization of Mesogens Crystallizes Lysozyme: Correlation between Nonamphiphilic Lyotropic Liquid Crystal Phase and Protein Crystal Formation

PubMed Central

Simon, Karen A.; Shetye, Gauri S.; Englich, Ulrich; Wu, Lei; Luk, Yan-Yeung

2011-01-01

Crystallization of proteins is important for fundamental studies and biopharmaceutical development but remains largely an empirical science. Here, we report the use of organic salts that can form a class of unusual non-amphiphilic lyotropic liquid crystals to crystallize the protein lysozyme. Certain non-amphiphilic organic molecules with fused aromatic rings and two charges can assemble into stable thread-like noncovalent polymers that may further form liquid crystal phases in water, traditionally termed chromonic liquid crystals. Using five of these mesogenic molecules as additives to induce protein crystallization, we discover that molecules that can form liquid crystal phases in water are highly effective at inducing the crystal formation of lysozyme, even at concentrations significantly lower than that required for forming liquid crystal phases. This result reveals an example of inducing protein crystallization by the molecular assembly of the additives, and is consistent with a new mechanism by which the strong hydration of an assembly process provides a gradual means to compete for the water molecules to enable solvated proteins to form crystals. PMID:21786812
Hydrothermal Synthesis, Crystal Structure, and Photoluminescent Properties of Li[UO2(CH3COO)3]3[Co(H2O)6

NASA Astrophysics Data System (ADS)

AlDamen, Murad A.; Juwhari, Hassan K.; Al-zuheiri, Aya M.; Alnazer, Louy A.

2017-12-01

Single crystal of Li[UO2(CH3COO)3]3[Co(H2O)6] was prepared and found to crystallize in the monoclinic crystal system in the sp. gr. C2/ c, with Z = 2, and unit cell parameters a = 22.1857(15) Å, b = 13.6477(8) Å, c = 15.6921(10) Å, β = 117.842(9)°, V = 4201.3(4) Å3. The crystal was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The single crystal X-ray diffraction analysis revealed that the crystal has a lamellar structure in which a cobalt hydrate is sandwiched within the Li[UO2(CH3COO)3]3 2- chains. Furthermore, the room temperature photoluminescence spectrum of the complex was investigated in the solid state.
Crystal structures of Sr(ClO4)2·3H2O, Sr(ClO4)2·4H2O and Sr(ClO4)2·9H2O

PubMed Central

Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

2014-01-01

The title compounds, strontium perchlorate trihydrate {di-μ-aqua-aquadi-μ-perchlorato-strontium, [Sr(ClO4)2(H2O)3]n}, strontium perchlorate tetrahydrate {di-μ-aqua-bis(triaquadiperchloratostrontium), [Sr2(ClO4)4(H2O)8]} and strontium perchlorate nonahydrate {heptaaquadiperchloratostrontium dihydrate, [Sr(ClO4)2(H2O)7]·2H2O}, were crystallized at low temperatures according to the solid–liquid phase diagram. The structures of the tri- and tetrahydrate consist of Sr2+ cations coordinated by five water molecules and four O atoms of four perchlorate tetrahedra in a distorted tricapped trigonal–prismatic coordination mode. The asymmetric unit of the trihydrate contains two formula units. Two [SrO9] polyhedra in the trihydrate are connected by sharing water molecules and thus forming chains parallel to [100]. In the tetrahydrate, dimers of two [SrO9] polyhedra connected by two sharing water molecules are formed. The structure of the nonahydrate contains one Sr2+ cation coordinated by seven water molecules and by two O atoms of two perchlorate tetrahedra (point group symmetry ..m), forming a tricapped trigonal prism (point group symmetry m2m). The structure contains additional non-coordinating water molecules, which are located on twofold rotation axes. O—H⋯O hydrogen bonds between the water molecules as donor and ClO4 tetrahedra and water molecules as acceptor groups lead to the formation of a three-dimensional network in each of the three structures. PMID:25552979
Superposition of two tRNA{sup Ser} acceptor stem crystal structures: Comparison of structure, ligands and hydration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eichert, Andre; Fuerste, Jens P.; Ulrich, Alexander

2010-05-07

We solved the X-ray structures of two Escherichia coli tRNA{sup Ser} acceptor stem microhelices. As both tRNAs are aminoacylated by the same seryl-tRNA-synthetase, we performed a comparative structure analysis of both duplexes to investigate the helical conformation, the hydration patterns and magnesium binding sites. It is well accepted, that the hydration of RNA plays an important role in RNA-protein interactions and that the extensive solvent content of the minor groove has a special function in RNA. The detailed comparison of both tRNA{sup Ser} microhelices provides insights into the structural arrangement of the isoacceptor tRNA aminoacyl stems with respect to themore » surrounding water molecules and may eventually help us to understand their biological function at atomic resolution.« less
Petrophysical Properties Of Sandy Sediments Possibly Hosting Gas Hydrate In The Eastern Margin Of Japan Sea

NASA Astrophysics Data System (ADS)

Uchida, T.; Takashima, I.; Sunaga, H.; Sasaki, S.; Matsumoto, R.

2011-12-01

In 2010 the MD179 project was undertaken by the Marion Dufresne aiming at recovery of deep seated gas and gas hydrate, methane induced carbonate, and deep sediments older than 300 ka in order to develop geologic model of gas hydrate accumulation and evaluate the possible environmental impact of gas hydrate for the last glacial-interglacial cycles. Sediment samples below the seafloor were obtained in the Umitaka Spur, Joetsu Channel, Toyama Trough, Japan Basin, Nishi Tsugaru and Okushiri Ridge areas by the MD179 cruise. Small amounts of sandy sediment have been retrieved as thin intercalations in Pleistocene and Holocene silty layers, where trace fossils and strong bioturbations are commonly observed. Those sandy sediments consist of very fine- to fine-grained sand grains, and are sometimes tuffaceous. Pore-size distribution measurements and thin-section observations of these arenite sands were undertaken, which indicatesd that porosities of muddy sediments are around 50 % but those of arenites range from 42 to 52 %, of which mean pore sizes and permeabilities are larger than those of siltstones and mudstones. These coarser sediments might have been transported approximately around 3 to 30 ka, where supplying sediments may not be abundant due to sea level fluctuation during the Pleistocene ice age. While the presence of gas hydrate in intergranular pores of arenite sands has not been confirmed, the soupy occurrence in recovered sediments may strongly indicate the presence of gas hydrate filling the intergranular pore system of arenite sands that is called pore-space hydrates. They have been recognized till now in the Mallik as well as in the Nankai Trough areas, which are considered to be very common even in the subsurface sandy sediments at the eastern margin of Japan Sea. Concentration of gas hydrate may need primary intergranular pores large enough to occur within a host sediment that may be arenite sand without matrix grains deposited in the sedimentary environment such as deep sea channels. The geological modeling of the gas hydrate formation and evolution system is concerned for energy resource potential in the Japan Sea as well as the Nankai Trough areas. Time of deposition of coarse-grained sediments can be recognized by the thermoluminescence (TL) dating method. TL dating works on the principle that materials containing naturally occurring radioactive isotopes such as uranium, thorium or potassium are subject to low levels of radiation. In mineral crystals, this leads to ionization of the atoms in the host material and freed electrons may become trapped in structural defects or holes in the mineral crystal lattice. These electrons can be released by heating under controlled conditions, and an emission of light occurs which is the basis of TL dating. Additionally they usually provide information about the provenance and the paleoenvironment when the sediments deposited. This study was performed as a part of the MH21 Research Consortium on methane hydrate in Japan.
Crystallization and Colloidal Stabilization of Ca(OH)2 in the Presence of Nopal Juice (Opuntia ficus indica): Implications in Architectural Heritage Conservation.

PubMed

Rodriguez-Navarro, Carlos; Ruiz-Agudo, Encarnacion; Burgos-Cara, Alejandro; Elert, Kerstin; Hansen, Eric F

2017-10-17

Hydrated lime (Ca(OH) 2 ) is a vernacular art and building material produced following slaking of CaO in water. If excess water is used, a slurry, called lime putty, forms, which has been the preferred craftsman selection for formulating lime mortars since Roman times. A variety of natural additives were traditionally added to the lime putty to improve its quality. The mucilaginous juice extracted from nopal cladodes has been and still is used as additive incorporated in the slaking water for formulation of lime mortars and plasters, both in ancient Mesoamerica and in the USA Southwest. Little is known on the ultimate effects of this additive on the crystallization and microstructure of hydrated lime. Here, we show that significant changes in habit and size of portlandite crystals occur following slaking in the presence of nopal juice as well as compositionally similar citrus pectin. Both additives contain polysaccharides made up of galacturonic acid and neutral sugar residues. The carboxyl (and hydroxyl) functional groups present in these residues and in their alkaline degradation byproducts, which are deprotonated at the high pH (12.4) produced during lime slaking, strongly interact with newly formed Ca(OH) 2 crystals acting in two ways: (a) as nucleation inhibitors, promoting the formation of nanosized crystals, and (b) as habit modifiers, favoring the development of planar habit following their adsorption onto positively charged (0001) Ca(OH) 2 faces. Adsorption of polysaccharides on Ca(OH) 2 crystals prevents the development of large particles, resulting in a very reactive, nanosized portlandite slurry. It also promotes steric stabilization, which limits aggregation, thus enhancing the colloidal nature of the lime putty. Overall, these effects are very favorable for the preparation of highly plastic lime mortars with enhanced properties.
On the nature of the reversibility of hydration-dehydration on the crystal structure and magnetism of the ferrimagnet [MnII(enH)(H2O)][CrIII(CN)6].H2O.

PubMed

Yoshida, Yusuke; Inoue, Katsuya; Kurmoo, Mohamedally

2009-01-05

We report the synthesis, crystal structure, and thermal and magnetic properties of the two-dimensional achiral soft ferrimagnet [Mn(II)(enH)(H(2)O)][Cr(III)(CN)(6)].H(2)O (1), en = 1,2-diaminoethane, as well as the recyclability of the dehydration and rehydration and their influence on the crystal structure and its magnetic properties. Unlike [Mn(S-pnH)(H(2)O)][Cr(CN)(6)].H(2)O (2S, pn = 1,2-diaminopropane), which is a chiral (P2(1)2(1)2(1)) enantiopure ferrimagnet (T(C) = 38 K), 1 crystallizes in the achiral orthorhombic Pcmn space group, having a similar two-dimensional square network of Mn-Cr with bridging cyanide, and 1 behaves also as a soft ferrimagnet (T(C) = 42 K). X-ray diffraction experiments on a single crystal of 1 indicate a transformation from a single crystal to an amorphous phase upon dehydrataion and partial recovery of its crystallinity upon rehydration. The dehydrated phase 1-DP exhibits long-range ordering at 75 K to a ferrimagnetic state and coercive field at 2 K of 100 Oe, which are a higher critical temperature and coercive field than for the virgin sample (H(C) = 60 Oe). Thermogravimetric analyses indicate that the crystallinity deteriorates upon hydration-dehydration cycling, with persistence toward the amorphous phase, as also seen by magnetization measurements. This effect is associated with an increase of statistical disorder inherent in the dehydration-rehydration process. X-ray powder diffraction suggests that 1-DP may retain order within the layers but loses coherence in the stacking of the layers.
Assessment of corneal hydration sensing in the terahertz band: in vivo results at 100 GHz

PubMed Central

Taylor, Zachary; Tewari, Pria; Sung, Shijun; Maccabi, Ashkan; Singh, Rahul; Culjat, Martin; Grundfest, Warren; Hubschman, Jean-Pierre; Brown, Elliott

2012-01-01

Abstract. Terahertz corneal hydration sensing has shown promise in ophthalmology applications and was recently shown to be capable of detecting water concentration changes of about two parts in a thousand in ex vivo corneal tissues. This technology may be effective in patient monitoring during refractive surgery and for early diagnosis and treatment monitoring in diseases of the cornea. In this work, Fuchs dystrophy, cornea transplant rejection, and keratoconus are discussed, and a hydration sensitivity of about one part in a hundred is predicted to be needed to successfully distinguish between diseased and healthy tissues in these applications. Stratified models of corneal tissue reflectivity are developed and validated using ex vivo spectroscopy of harvested porcine corneas that are hydrated using polyethylene glycol solutions. Simulation of the cornea’s depth-dependent hydration profile, from 0.01 to 100 THz, identifies a peak in intrinsic reflectivity contrast for sensing at 100 GHz. A 100 GHz hydration sensing system is evaluated alongside the current standard ultrasound pachymetry technique to measure corneal hydration in vivo in four rabbits. A hydration sensitivity, of three parts per thousand or better, was measured in all four rabbits under study. This work presents the first in vivo demonstration of remote corneal hydration sensing. PMID:23085925
Assessment of corneal hydration sensing in the terahertz band: in vivo results at 100 GHz

NASA Astrophysics Data System (ADS)

Bennett, David; Taylor, Zachary; Tewari, Pria; Sung, Sijun; Maccabi, Ashkan; Singh, Rahul; Culjat, Martin; Grundfest, Warren; Hubschman, Jean-Pierre; Brown, Elliott

2012-09-01

Terahertz corneal hydration sensing has shown promise in ophthalmology applications and was recently shown to be capable of detecting water concentration changes of about two parts in a thousand in ex vivo corneal tissues. This technology may be effective in patient monitoring during refractive surgery and for early diagnosis and treatment monitoring in diseases of the cornea. In this work, Fuchs dystrophy, cornea transplant rejection, and keratoconus are discussed, and a hydration sensitivity of about one part in a hundred is predicted to be needed to successfully distinguish between diseased and healthy tissues in these applications. Stratified models of corneal tissue reflectivity are developed and validated using ex vivo spectroscopy of harvested porcine corneas that are hydrated using polyethylene glycol solutions. Simulation of the cornea's depth-dependent hydration profile, from 0.01 to 100 THz, identifies a peak in intrinsic reflectivity contrast for sensing at 100 GHz. A 100 GHz hydration sensing system is evaluated alongside the current standard ultrasound pachymetry technique to measure corneal hydration in vivo in four rabbits. A hydration sensitivity, of three parts per thousand or better, was measured in all four rabbits under study. This work presents the first in vivo demonstration of remote corneal hydration sensing.
A view inside the nature of protein crystals

NASA Astrophysics Data System (ADS)

Oswald, R.; Pietzsch, M.; Ulrich, J.

2017-07-01

In this work a fundamental analysis of protein crystal modifications was presented to compare and confirm the components of protein crystal modifications. The result is that a protein crystal contains besides the protein, the precipitant and water. A mass spectrometer coupled to a thermogravimetry device was used to confirm the different waters (free water -the chosen buffer- and bound water) inside the crystals. Here the biggest amount of water is the free water (the buffer) with an amount of approximately 35%. The bound water (in the sense of a hydrate) has only an amount of about 1-1.5%. Furthermore, an x-ray analysis to confirm the influence range of pH value on the stability of one crystal modification for the understanding of effects on dissolution mechanism of protein crystals was investigated. The crystals of the tetragonal modification crystallized at pH 4.7, 4.85, 5.0, 5.15 and 5.3 maintain according to the x-ray measurements the same lattice parameters. The measured data are discussed.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Casco, Mirian E.; Silvestre-Albero, Joaquín; Ramírez-Cuesta, Anibal J.

Natural methane hydrates are believed to be the largest source of hydrocarbons on Earth. These structures are formed in specific locations such as deep-sea sediments and the permafrost based on demanding conditions of high pressure and low temperature. We report that, by taking advantage of the confinement effects on nanopore space, synthetic methane hydrates grow under mild conditions (3.5 MPa and 2 degrees C), with faster kinetics (within minutes) than nature, fully reversibly and with a nominal stoichiometry that mimics nature. Furthermore, the formation of the hydrate structures in nanospace and their similarity to natural hydrates is confirmed using inelasticmore » neutron scattering experiments and synchrotron X-ray powder diffraction. Our findings may be a step towards the application of a smart synthesis of methane hydrates in energy-demanding applications (for example, transportation).« less
Determination of pore-scale hydrate phase equilibria in sediments using lab-on-a-chip technology.

PubMed

Almenningen, Stian; Flatlandsmo, Josef; Kovscek, Anthony R; Ersland, Geir; Fernø, Martin A

2017-11-21

We present an experimental protocol for fast determination of hydrate stability in porous media for a range of pressure and temperature (P, T) conditions. Using a lab-on-a-chip approach, we gain direct optical access to dynamic pore-scale hydrate formation and dissociation events to study the hydrate phase equilibria in sediments. Optical pore-scale observations of phase behavior reproduce the theoretical hydrate stability line with methane gas and distilled water, and demonstrate the accuracy of the new method. The procedure is applicable for any kind of hydrate transitions in sediments, and may be used to map gas hydrate stability zones in nature.
Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, Marie D.; Landis, Eric N.; Brune, Philip F.

The pyroclastic aggregate concrete of Trajan’s Markets (110 CE), now Museo Fori Imperiali in Rome, has absorbed energy from seismic ground shaking and long-term foundation settlement for nearly two millenia while remaining largely intact at the structural scale. The scientific basis of this exceptional service record is explored through computed tomography of fracture surfaces and synchroton X-ray microdiffraction analyses of a reproduction of the standardized hydrated lime–volcanic ash mortar that binds decimeter-sized tuff and brick aggregate in the conglomeratic concrete. The mortar reproduction gains fracture toughness over 180 d through progressive coalescence of calcium–aluminum-silicate–hydrate (C-A-S-H) cementing binder with Ca/(Si+Al) ≈more » 0.8–0.9 and crystallization of strätlingite and siliceous hydrogarnet (katoite) at ≥90 d, after pozzolanic consumption of hydrated lime was complete. Platey strätlingite crystals toughen interfacial zones along scoria perimeters and impede macroscale propagation of crack segments. In the 1,900 year old mortar, C-A-S-H has low Ca/(Si+Al) ≈ 0.45–0.75. Dense clusters of 2- to 30-µm strätlingite plates further reinforce interfacial zones, the weakest link of modern cement-based concrete, and the cementitious matrix. These crystals formed during long-term autogeneous reaction of dissolved calcite from lime and the alkali-rich scoriae groundmass, clay mineral (halloysite), and zeolite (phillipsite and chabazite) surface textures from the Pozzolane Rosse pyroclastic flow, erupted from the nearby Alban Hills volcano. The clast-supported conglomeratic fabric of the concrete presents further resistance to fracture propagation at the structural scale.« less
Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

DOE PAGES

Jackson, Marie D.; Landis, Eric N.; Brune, Philip F.; ...

2014-12-15

The pyroclastic aggregate concrete of Trajan’s Markets (110 CE), now Museo Fori Imperiali in Rome, has absorbed energy from seismic ground shaking and long-term foundation settlement for nearly two millenia while remaining largely intact at the structural scale. The scientific basis of this exceptional service record is explored through computed tomography of fracture surfaces and synchroton X-ray microdiffraction analyses of a reproduction of the standardized hydrated lime–volcanic ash mortar that binds decimeter-sized tuff and brick aggregate in the conglomeratic concrete. The mortar reproduction gains fracture toughness over 180 d through progressive coalescence of calcium–aluminum-silicate–hydrate (C-A-S-H) cementing binder with Ca/(Si+Al) ≈more » 0.8–0.9 and crystallization of strätlingite and siliceous hydrogarnet (katoite) at ≥90 d, after pozzolanic consumption of hydrated lime was complete. Platey strätlingite crystals toughen interfacial zones along scoria perimeters and impede macroscale propagation of crack segments. In the 1,900 year old mortar, C-A-S-H has low Ca/(Si+Al) ≈ 0.45–0.75. Dense clusters of 2- to 30-µm strätlingite plates further reinforce interfacial zones, the weakest link of modern cement-based concrete, and the cementitious matrix. These crystals formed during long-term autogeneous reaction of dissolved calcite from lime and the alkali-rich scoriae groundmass, clay mineral (halloysite), and zeolite (phillipsite and chabazite) surface textures from the Pozzolane Rosse pyroclastic flow, erupted from the nearby Alban Hills volcano. The clast-supported conglomeratic fabric of the concrete presents further resistance to fracture propagation at the structural scale.« less
Effect of hydrated salts on the microstructure and phase transformation of poly(vinylidenefluoride-hexafluoropropylene) composites

NASA Astrophysics Data System (ADS)

Yuennan, Jureeporn; Sukwisute, Pisan; Muensit, Nantakan

2018-05-01

The present work has investigated a means of fabricating porous, β phase P(VDF-HFP) film by adding two kinds of hydrated metal salts. Without the use of mechanical stretching or electrical poling treatments, MgCl2 · 6H2O and AlCl3 · 6H2O are found to induce the formation of β phase crystals in porous film derived from the solution casting method. Trivalent Al ions have been found to effectively promote the self-oriented β phase of the P(VDF-HFP) film greater than divalent Mg ions. The overall β content is achieved about 38% and 42% for adding 0.25 wt% Mg- and Al-salts, respectively. The average pore sizes and surface roughness of porous P(VDF-HFP) films are increased with increasing salt concentration. The dielectric constant of about 5 for pure P(VDF-HFP) film (at 100 Hz) has been boosted up to 13–19 when adding the salts. In addition, the P(VDF-HFP) films filled with Al-salt exhibit the largest piezoelectric coefficient of 20 pC/N. Thus, the modified polymers are one of candidate materials for using in dielectric and piezoelectric applications.

Laboratory investigation of hydrated lime as an antistripping additive : final report.

DOT National Transportation Integrated Search

1983-01-01

The purpose of this laboratory study was to determine the effectiveness of hydrated lime as an antistripping additive when used in bituminous mixes incorporating aggregates frequently used in such mixes in Virginia. The application of 1% hydrated lim...
CO2 hydrate: Synthesis, composition, structure, dissociation behavior, and a comparison to structure I CH4 hydrate

USGS Publications Warehouse

Circone, S.; Stern, L.A.; Kirby, S.H.; Durham, W.B.; Chakoumakos, B.C.; Rawn, C.J.; Rondinone, A.J.; Ishii, Y.

2003-01-01

Structure I (sI) carbon dioxide (CO2) hydrate exhibits markedly different dissociation behavior from sI methane (CH4) hydrate in experiments in which equilibrated samples at 0.1 MPa are heated isobarically at 13 K/h from 210 K through the H2O melting point (273.15 K). The CO2 hydrate samples release only about 3% of their gas content up to temperatures of 240 K, which is 22 K above the hydrate phase boundary. Up to 20% is released by 270 K, and the remaining CO2 is released at 271.0 plusmn; 0.5 K, where the sample temperature is buffered until hydrate dissociation ceases. This reproducible buffering temperature for the dissociation reaction CO2??nH2O = CO2(g) + nH2O(1 to s) is measurably distinct from the pure H2O melting point at 273.15 K, which is reached as gas evolution ceases. In contrast, when si CH4 hydrate is heated at the same rate at 0.1 MPa, >95% of the gas is released within 25 K of the equilibrium temperature (193 K at 0.1 MPa). In conjunction with the dissociation study, a method for efficient and reproducible synthesis of pure polycrystalline CO2 hydrate with suitable characteristics for material properties testing was developed, and the material was characterized. CO2 hydrate was synthesized from CO2 liquid and H2O solid and liquid reactants at pressures between 5 and 25 MPa and temperatures between 250 and 281 K. Scanning electron microscopy (SEM) examination indicates that the samples consist of dense crystalline hydrate and 50-300 ??m diameter pores that are lined with euhedral cubic hydrate crystals. Deuterated hydrate samples made by this same procedure were analyzed by neutron diffraction at temperatures between 4 and 215 K; results confirm that complete conversion of water to hydrate has occurred and that the measured unit cell parameter and thermal expansion are consistent with previously reported values. On the basis of measured weight gain after synthesis and gas yields from the dissociation experiments, approximately all cages in the hydrate structure are filled such that n ??? 5.75.
Dehydration of planetary ices at high pressure; the role of analogue materials (Invited)

NASA Astrophysics Data System (ADS)

Fortes, A. D.

2013-12-01

Many planet-forming compounds become unstable with respect to their components under conditions of high pressure. In the Earth, for example, Mg2SiO4 breaks down to MgSiO3 + MgO at ~ 25 GPa, a pressure corresponding to the 670 km seismic discontinuity, with significance for the dynamics of convective flow in the mantle. A similar phenomenon occurs with many hydrate compounds thought to be major ';rock forming minerals' inside outer Solar System bodies, undoubtedly with important consequences for the structure and dynamics of icy worlds. It is well known that clathrates tend to form denser polymorphs with an incrementally greater concentration of the guest molecule, exsolving high-pressure phases of water ice in the process, or else (in the case of CO2), break down to entirely to their component molecular solids. My own recent work using high-pressure neutron powder diffraction has explored not only the behaviour of methane clathrates but also the exsolution of water from ammonia dihydrate and monohydrate, both of which break down eventually to ammonia hemihydrate + ice. In some cases, understanding the sequence of changes in both crystal structure and composition at high pressure is challenging, particularly when the starting materials have a complex crystal structure. Some years ago, I identified a high-pressure phase boundary where MgSO4.11H2O (meridianiite) appeared to break down to another hydrate and high-pressure ice VI. However, the powder diffraction pattern of the hydrate formed under these conditions resembled nothing encountered previously in my high-pressure studies of the next lowest hydrate, MgSO4.7H2O (epsomite). This led me to search for hydration states between 7 and 11 which might have escaped detection over several centuries of study of simple divalent metal sulfates. A wide-ranging systematic study of M2+X6+O4.nH2O compounds at low temperatures uncovered two new hydrates, an 8-hydrate and a 9-hydrate, the former occurring only in NiSO4 solutions, and the latter being found in Ni-, Zn-, Cu-, and Fe-doped MgSO4 solutions. Indeed, I determined that small quantities of pure MgSO4.9H2O can co-crystallise at ambient pressure with meridianiite. However, these all appear to be metastable states, and further work was necessary to try and discover stable forms of these hydrates for further study. In experiments carried out earlier this year, evidence has emerged not only that MgMoO4 can form a (possibly) stable 8-hydrate but also that MgSeO4 can form a 9-hydrate that exists in equilibrium with liquid near the eutectic. These apparently esoteric compounds (from a planetary perspective) may yet hold the key to understanding the high-pressure behaviour of true planetary materials. Just as the search for analogue materials over many decades has substantially advanced our knowledge of Earth materials, similar analogue studies are poised to unlock the mysteries of these planetary ices.
The HD molecule in small and medium cages of clathrate hydrates: Quantum dynamics studied by neutron scattering measurements and computation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colognesi, Daniele; Celli, Milva; Ulivi, Lorenzo, E-mail: lorenzo.ulivi@isc.cnr.it

2014-10-07

We report inelastic neutron scattering (INS) measurements on molecular hydrogen deuteride (HD) trapped in binary cubic (sII) and hexagonal (sH) clathrate hydrates, performed at low temperature using two different neutron spectrometers in order to probe both energy and momentum transfer. The INS spectra of binary clathrate samples exhibit a rich structure containing sharp bands arising from both the rotational transitions and the rattling modes of the guest molecule. For the clathrates with sII structure, there is a very good agreement with the rigorous fully quantum simulations which account for the subtle effects of the anisotropy, angular and radial, of themore » host cage on the HD microscopic dynamics. The sH clathrate sample presents a much greater challenge, due to the uncertainties regarding the crystal structure, which is known only for similar crystals with different promoter, but nor for HD (or H{sub 2}) plus methyl tert-butyl ether (MTBE-d12)« less
Infrared light-induced protein crystallization. Structuring of protein interfacial water and periodic self-assembly

NASA Astrophysics Data System (ADS)

Kowacz, Magdalena; Marchel, Mateusz; Juknaité, Lina; Esperança, José M. S. S.; Romão, Maria João; Carvalho, Ana Luísa; Rebelo, Luís Paulo N.

2017-01-01

We show that a physical trigger, a non-ionizing infrared (IR) radiation at wavelengths strongly absorbed by liquid water, can be used to induce and kinetically control protein (periodic) self-assembly in solution. This phenomenon is explained by considering the effect of IR light on the structuring of protein interfacial water. Our results indicate that the IR radiation can promote enhanced mutual correlations of water molecules in the protein hydration shell. We report on the radiation-induced increase in both the strength and cooperativeness of H-bonds. The presence of a structured dipolar hydration layer can lead to attractive interactions between like-charged biomacromolecules in solution (and crystal nucleation events). Furthermore, our study suggests that enveloping the protein within a layer of structured solvent (an effect enhanced by IR light) can prevent the protein non-specific aggregation favoring periodic self-assembly. Recognizing the ability to affect protein-water interactions by means of IR radiation may have important implications for biological and bio-inspired systems.
77 FR 40032 - Methane Hydrate Advisory Committee

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-06

... DEPARTMENT OF ENERGY Methane Hydrate Advisory Committee AGENCY: Office of Fossil Energy, Department of Energy. ACTION: Notice of open meeting. SUMMARY: This notice announces a meeting of the Methane... of the Methane Hydrate Advisory Committee is to provide advice on potential applications of methane...
The effects of mucopolysaccharide polysulphate on hydration and elasticity of human skin.

PubMed

Wanitphakdeedecha, Rungsima; Eimpunth, Sasima; Manuskiatti, Woraphong

2011-01-01

Background. Mucopolysaccharide polysulphate (MPS) has been used in medicine as an anti-inflammatory and antithrombotic agent for over 50 years. Its chemical structure permits considerable hydrogen bonding with adjacent water molecules, which effectively leads to hydration of the surrounding tissue. In addition, it stimulates endogenous hyaluronate synthesis, resulting in an increase in water-binding capacity and viscoelasticity of the skin. Objective. To study the efficacy of 0.1% MPS on hydration and elasticity of human skin. Methods. The first part of this study was a randomized double blind placebo-controlled study which included 60 female volunteers aged 30-45 years with dry skin, defined by Corneometer CM 825. The volunteers were treated with either 0.1% MPS or vehicle control. All subjects were asked to apply 1 g of cream to their face twice daily for a total period of 4 weeks. Skin hydration and elasticity were measured at baseline and week 4 with Corneometer CM 825 and cutometer MPA 580, respectively, at forehead and both cheeks. The second part of this study focused on the efficacy of 0.1% MPS on skin hydration after single application. 20 female volunteers aged 30-45 years with dry skin, defined by Corneometer CM 825, were recruited to the study. All subjects were asked to apply 2 g of 0.1% MPS cream on entirely randomly selected forearm. Skin hydration at the middle of both forearms was measured at baseline, immediately after application, and every 1 hour after application for a period of 10 hours. Results. 57 subjects (28 in vehicle control group, 29 in MPS) completed treatment protocol. The baseline skin hydration of both groups was not significantly different (P = 0.47). Hower, there was a statistically significant difference in skin hydration at 4 weeks between MPS and placebo group (P = 0.01). Skin elasticity was significantly improved at week 4 in both groups (vehicle-control, P < 0.01, and MPS, P < 0.01). However, no significant difference in skin elasticity between MPS and vehicle-control group was noted (P = 0.15). Lastly, there was a statistically significant improvement in skin hydration after a single application (P < 0.01). This improvement was maintained for 10 hours. Conclusions. MPS provided improvement of skin hydration but not skin elasticity in woman with dry skin, compared with vehicle control. And MPS improved the skin hydration for at least 10 hours after single application.
Natural gas hydrate in sediments imaged by cryogenic SEM: Insights from lab experiments on synthetic hydrates as interpretive guides.

NASA Astrophysics Data System (ADS)

Stern, L. A.; Kirby, S. H.

2006-12-01

In the investigation of natural gas hydrates, distinguishing in situ grain textures and microstructures from artifacts produced during retrieval, storage, and examination can be quite challenging. Using cryogenic scanning electron microscopy, we investigated the physical states of gas hydrates produced in our lab as well as of those in drill core of hydrate-bearing sediment from marine and Arctic permafrost environments. Here, we compare grain and pore structures observed in samples from the Cascadia margin (courtesy IODP Expedition 311), McKenzie River Delta (Mallik Well 5L-38), and Gulf of Mexico (RSV Marion Dufresne 2002), with those present in hydrocarbon hydrates grown in our laboratory and subjected to controlled P-T conditions. The following trends are apparent for the natural gas hydrates imaged to-date: (1) Samples typically contain massive domains of polycrystalline gas hydrate that in turn contain isolated gas-filled pores that are sometimes lined with euhedral hydrate crystals. Pores are typically 5 50 microns in diameter and occupy roughly 10-30 percent of the domain. Grain sizes, where visible, are commonly 20 to 50 microns. (2) Hydrate grain boundaries, particularly near the exposed sample surface, are often replaced by a nanoporous material. Based on its location and behavior, this material is presumed to be gas-charged porous ice produced by hydrate decomposition along grain surfaces. In some samples, grains are instead bounded by a framework of dense, tabular material embedded within the sample, best revealed upon sublimation of the hydrate. Their composition is yet unknown but may be salt or carbonate-bearing minerals. (3) Where hydrate grows into clayey sediments, the clays typically arrange with platelets subparallel around the pods or veins of hydrate. (4) Domains of nano-to-micro- porous water ice are also seen in all recovered natural samples, presumed to be hydrate decomposition product produced during drill-core retrieval and handling. Based on lab experiments, we believe the initial liquid product is frozen as a result of the local temperature reduction accompanying the endothermic dissociation reaction. The porous texture is then preserved by liquid nitrogen quenching. (5) Samples from both marine and permafrost environments also display closely juxtaposed regions of dense and porous hydrate and ice. Although the close association of these regions remains puzzling, lab tests verify that dense hydrate can exhibit such porous appearance along it's surface after even minor decomposition at cold conditions (below 273 K). In turn, companion experiments show that nanoporous hydrate anneals to a densely crystalline habit at conditions within the hydrate stability region above 273 K, suggesting that nanoporous gas hydrate is not stable at most in situ natural conditions.
Workshop summary: Physical properties of gas hydrate-bearing sediment

USGS Publications Warehouse

Waite, William F.; Santamarina, J.C.

2008-01-01

A wide range of particle and pore scale phenomena, often coupled, determines the macro-scale response of gas-hydrate bearing sediment to changes in mechanical, thermal, or chemical conditions. Predicting this macro-scale response is critical for applications such as optimizing the production of methane from gas-hydrate deposits, or determining the role of gas hydrates in global carbon cycling and climate change.
Controlled In Meso Phase Crystallization – A Method for the Structural Investigation of Membrane Proteins

PubMed Central

Kubicek, Jan; Schlesinger, Ramona; Baeken, Christian; Büldt, Georg; Schäfer, Frank; Labahn, Jörg

2012-01-01

We investigated in meso crystallization of membrane proteins to develop a fast screening technology which combines features of the well established classical vapor diffusion experiment with the batch meso phase crystallization, but without premixing of protein and monoolein. It inherits the advantages of both methods, namely (i) the stabilization of membrane proteins in the meso phase, (ii) the control of hydration level and additive concentration by vapor diffusion. The new technology (iii) significantly simplifies in meso crystallization experiments and allows the use of standard liquid handling robots suitable for 96 well formats. CIMP crystallization furthermore allows (iv) direct monitoring of phase transformation and crystallization events. Bacteriorhodopsin (BR) crystals of high quality and diffraction up to 1.3 Å resolution have been obtained in this approach. CIMP and the developed consumables and protocols have been successfully applied to obtain crystals of sensory rhodopsin II (SRII) from Halobacterium salinarum for the first time. PMID:22536388
Potential of ikaite to record the evolution of oceanic δ18O

NASA Astrophysics Data System (ADS)

Rickaby, R. E. M.; Shaw, S.; Bennitt, G.; Kennedy, H.; Zabel, M.; Lennie, A.

2006-06-01

A challenge in the quest to understand the sensitivity of the climate system is the separation of the competing effects of ice volume or sea level, salinity, and temperature on foraminiferal δ18O. We present precipitation experiments on the mineral ikaite, a hydrated form of calcium carbonate found in organic carbon rich deep-marine sediments, that show that the hydration waters within the ikaite crystal capture the δ18O of seawater (δ18Osw) with a fractionation factor of 1.0029 (±0.0002). The δ18Osw measures the volume of continental ice, with an overprint of local salinity. Isolation of δ18Osw by analysis of the hydration waters of sedimentary ikaite preserved at temperatures <4 °C could be exploited to create a record of sea level during the Pleistocene. Preliminary data of δ18Osw from hydration waters of ikaite at the Last Glacial Maximum agree with estimates from modeling of pore waters that Antarctic Bottom Water was +1.4‰ ± 0.2‰ heavier.
Definitive Mineralogical Analysis of Martian Rocks and Soil Using the CheMin XRD/XRF Instrument and the USDC Sampler

NASA Technical Reports Server (NTRS)

Blake, D. F.; Sarrazin, P.; Chipera, S. J.; Bish, D. L.; Vaniman, D. T.; Bar-Cohen, Y.; Sherrit, S.; Collins, S.; Boyer, B.; Bryson, C.

2003-01-01

The search for evidence of extant or extinct life on Mars will initially be a search for evidence of present or past conditions supportive of life (e.g., evidence of water), not for life itself. Definitive evidence of past or present water activity lies in the discovery of: * Hydrated minerals: The "rock type" hosting the hydrated minerals could be igneous, metamorphic, or sedimentary, with only a minor hydrated mineral phase. Therefore, the identification of minor phases is important. * Clastic sediments: Clastic sediments are commonly identified by the fact that they contain minerals of disparate origin that could only have come together as a mechanical mixture. Therefore, the identification of all minerals present in a mixture to ascertain mineralogical source regions is important. * Hydrothermal precipitates and chemical sediments: Some chemical precipitates are uniquely identified only by their structure. For example, Opal A, Opal CT, tridymite, crystobalite, high and low Quartz all have the same composition (SiO2) but different crystal structures indicative of different environments - from hydrothermal hydrothermal formation to low temperature precipitation. Other silica types such as stishovite can provide evidence of shock metamorphism. Therefore, identification of crystal structures and structural polymorphs is important. The elucidation of the nature of the Mars soil will require the identification of mineral components that can unravel its history and the history of the Mars atmosphere.
Synthesis, characterization, thermal and explosive properties of potassium salts of trinitrophloroglucinol.

PubMed

Wang, Liqiong; Chen, Hongyan; Zhang, Tonglai; Zhang, Jianguo; Yang, Li

2007-08-17

Three different substituted potassium salts of trinitrophloroglucinol (H(3)TNPG) were prepared and characterized. The salts are all hydrates, and thermogravimetric analysis (TG) and elemental analysis confirmed that these salts contain crystal H2O and that the amount crystal H2O in potassium salts of H3TNPG is 1.0 hydrate for mono-substituted potassium salts of H3TNPG [K(H2TNPG)] and di-substituted potassium salt of H3TNPG [K2(HTNPG)], and 2.0 hydrate for tri-substituted potassium salt of H3TNPG [K3(TNPG)]. Their thermal decomposition mechanisms and kinetic parameters from 50 to 500 degrees C were studied under a linear heating rate by differential scanning calorimetry (DSC). Their thermal decomposition mechanisms undergo dehydration stage and intensive exothermic decomposition stage. FT-IR and TG studies verify that their final residua of decomposition are potassium cyanide or potassium carbonate. According to the onset temperature of the first exothermic decomposition process of dehydrated salts, the order of the thermal stability from low to high is from K(H2TNPG) and K2(HTNPG) to K3(TNPG), which is conform to the results of apparent activation energy calculated by Kissinger's and Ozawa-Doyle's method. Sensitivity test results showed that potassium salts of H3TNPG demonstrated higher sensitivity properties and had greater explosive probabilities.
Humidity scanning quartz crystal microbalance with dissipation monitoring setup for determination of sorption-desorption isotherms and rheological changes

NASA Astrophysics Data System (ADS)

Björklund, Sebastian; Kocherbitov, Vitaly

2015-05-01

A new method to determine water sorption-desorption isotherms with high resolution in the complete range of water activities (relative humidities) is presented. The method is based on quartz crystal microbalance with dissipation monitoring (QCM-D). The QCM-D is equipped with a humidity module in which the sample film is kept in air with controlled humidity. The experimental setup allows for continuous scanning of the relative humidity from either dry to humid conditions or vice versa. The amount of water sorbed or desorbed from the sample is determined from the resonance frequencies of the coated quartz sensor, via analysis of the overtone dependence. In addition, the method allows for characterization of hydration induced changes of the rheological properties from the dissipation data, which is closely connected to the viscoelasticity of the film. The accuracy of the humidity scanning setup is confirmed in control experiments. Sorption-desorption isotherms of pig gastric mucin and lysozyme, obtained by the new method, show good agreement with previous results. Finally, we show that the deposition technique used to coat the quartz sensor influences the QCM-D data and how this issue can be used to obtain further information on the effect of hydration. In particular, we demonstrate that spin-coating represents an attractive alternative to obtain sorption-desorption isotherms, while drop-coating provides additional information on changes of the rheological properties during hydration.
Repulsive hydration forces between calcite surfaces and their effect on the brittle strength of calcite-bearing rocks

NASA Astrophysics Data System (ADS)

Røyne, Anja; Dalby, Kim N.; Hassenkam, Tue

2015-06-01

The long-term mechanical strength of calcite-bearing rocks is highly dependent on the presence and nature of pore fluids, and it has been suggested that the observed effects are due to changes in nanometer-scale surface forces near fracture tips and grain contacts. In this letter, we present measurements of forces between two calcite surfaces in air and water-glycol mixtures using the atomic force microscope. We show a time- and load-dependent adhesion at low water concentrations and a strong repulsion in the presence of water, which is most likely due to hydration of the strongly hydrophilic calcite surfaces. We argue that this hydration repulsion can explain the commonly observed water-induced decrease in strength in calcitic rocks and single calcite crystals. Furthermore, this relatively simple experimental setup may serve as a useful tool for analyzing surface forces in other mineral-fluid combinations.
The mechanism of vapor phase hydration of calcium oxide: implications for CO2 capture.

PubMed

Kudłacz, Krzysztof; Rodriguez-Navarro, Carlos

2014-10-21

Lime-based sorbents are used for fuel- and flue-gas capture, thereby representing an economic and effective way to reduce CO2 emissions. Their use involves cyclic carbonation/calcination which results in a significant conversion reduction with increasing number of cycles. To reactivate spent CaO, vapor phase hydration is typically performed. However, little is known about the ultimate mechanism of such a hydration process. Here, we show that the vapor phase hydration of CaO formed after calcination of calcite (CaCO3) single crystals is a pseudomorphic, topotactic process, which progresses via an intermediate disordered phase prior to the final formation of oriented Ca(OH)2 nanocrystals. The strong structural control during this solid-state phase transition implies that the microstructural features of the CaO parent phase predetermine the final structural and physicochemical (reactivity and attrition) features of the product hydroxide. The higher molar volume of the product can create an impervious shell around unreacted CaO, thereby limiting the efficiency of the reactivation process. However, in the case of compact, sintered CaO structures, volume expansion cannot be accommodated in the reduced pore volume, and stress generation leads to pervasive cracking. This favors complete hydration but also detrimental attrition. Implications of these results in carbon capture and storage (CCS) are discussed.
Structure and interactions of fully hydrated dioleoylphosphatidylcholine bilayers.

PubMed Central

Tristram-Nagle, S; Petrache, H I; Nagle, J F

1998-01-01

This study focuses on dioleoylphosphatidylcholine (DOPC) bilayers near full hydration. Volumetric data and high-resolution synchrotron x-ray data are used in a method that compares DOPC with well determined gel phase dipalmitoylphosphatidylcholine (DPPC). The key structural quantity obtained is fully hydrated area/lipid A0 = 72.2 +/- 1.1 A2 at 30 degrees C, from which other quantities such as thickness of the bilayer are obtained. Data for samples over osmotic pressures from 0 to 56 atmospheres give an estimate for the area compressibility of KA = 188 dyn/cm. Obtaining the continuous scattering transform and electron density profiles requires correction for liquid crystal fluctuations. Quantitation of these fluctuations opens an experimental window on the fluctuation pressure, the primary repulsive interaction near full hydration. The fluctuation pressure decays exponentially with water spacing, in agreement with analytical results for soft confinement. However, the ratio of decay length lambda(fl) = 5.8 A to hydration pressure decay length lambda = 2.2 A is significantly larger than the value of 2 predicted by analytical theory and close to the ratio obtained in recent simulations. We also obtain the traditional osmotic pressure versus water spacing data. Our analysis of these data shows that estimates of the Hamaker parameter H and the bending modulus Kc are strongly coupled. PMID:9675192
Crystal structures of two tetrameric β-carbonic anhydrases from the filamentous ascomycete Sordaria macrospora.

PubMed

Lehneck, Ronny; Neumann, Piotr; Vullo, Daniela; Elleuche, Skander; Supuran, Claudiu T; Ficner, Ralf; Pöggeler, Stefanie

2014-04-01

Carbonic anhydrases (CAs) are metalloenzymes catalyzing the reversible hydration of carbon dioxide to bicarbonate (hydrogen carbonate) and protons. CAs have been identified in archaea, bacteria and eukaryotes and can be classified into five groups (α, β, γ, δ, ζ) that are unrelated in sequence and structure. The fungal β-class has only recently attracted attention. In the present study, we investigated the structure and function of the plant-like β-CA proteins CAS1 and CAS2 from the filamentous ascomycete Sordaria macrospora. We demonstrated that both proteins can substitute for the Saccharomyces cerevisiae β-CA Nce103 and exhibit an in vitro CO2 hydration activity (kcat /Km of CAS1: 1.30 × 10(6) m(-1) ·s(-1) ; CAS2: 1.21 × 10(6 ) m(-1) ·s(-1) ). To further investigate the structural properties of CAS1 and CAS2, we determined their crystal structures to a resolution of 2.7 Å and 1.8 Å, respectively. The oligomeric state of both proteins is tetrameric. With the exception of the active site composition, no further major differences have been found. In both enzymes, the Zn(2) (+) -ion is tetrahedrally coordinated; in CAS1 by Cys45, His101 and Cys104 and a water molecule and in CAS2 by the side chains of four residues (Cys56, His112, Cys115 and Asp58). Both CAs are only weakly inhibited by anions, making them good candidates for industrial applications. CAS1 and CAS2 bind by x-ray crystallography (View interaction) Structural data have been deposited in the Protein Data Bank database under accession numbers 4O1J for CAS1 and 4O1K for CAS2. © 2014 FEBS.
Bis{2-[2,5-bis(pyridin-2-yl)-1H-imidazol-4-yl]pyridinium} tetracyanidoplatinate(II) tetrahydrate

PubMed Central

Gámez-Heredia, Raquel; Navarro, Rosa E.; Höpfl, Herbert; Cruz-Enríquez, Adriana; Campos-Gaxiola, José J.

2013-01-01

The asymmetric unit of the title hydrated complex salt, (C18H14N5)2[Pt(CN)4]·4H2O, consists of one 2-[2,5-bis(pyridin-2-yl)-1H-imidazol-4-yl]pyridinium cation, half a tetracyanidoplatinate(II) dianion, which is located about a crystallographic inversion center, and two water molecules of crystallization. The PtII atom has a square-planar coordination environment, with Pt—CCN distances of 1.992 (4) and 2.000 (4) Å. In the cation, there is an N—H⋯N hydrogen bond linking adjacent pyridinium and pyridine rings in positions 4 and 5. Despite this, the organic component is non-planar, as shown by the dihedral angles of 10.3 (2), 6.60 (19) and 15.66 (18)° between the planes of the central imidazole ring and the pyridine/pyridinium substituents in the 2-, 4- and 5-positions. In the crystal, cations and anions are linked via O—H⋯O, O—H⋯N and N—H⋯O hydrogen bonds, forming a three-dimensional network. Additional π–π, C—H⋯O and C—H⋯N contacts provide stabilization to the crystal lattice. PMID:23794972
Fabrication of GO/Cement Composites by Incorporation of Few-Layered GO Nanosheets and Characterization of Their Crystal/Chemical Structure and Properties.

PubMed

Lv, Shenghua; Hu, Haoyan; Zhang, Jia; Luo, Xiaoqian; Lei, Ying; Sun, Li

2017-12-18

Original graphene oxide (GO) nanosheets were prepared using the Hummers method and found to easily aggregate in aqueous and cement composites. Using carboxymethyl chitosan (CCS) as a dispersant, few-layered GO nanosheets (1-2 layers) were obtained by forming CCS/GO intercalation composites. The testing results indicated that the few-layered GO nanosheets could uniformly spread, both in aqueous and cement composites. The cement composites were prepared with GO dosages of 0.03%, 0.05% and 0.07% and we found that they had a compact microstructure in the whole volume. A special feature was determined, namely that the microstructures consisted of regular-shaped crystals created by self-crosslinking. The X-ray diffraction (XRD) results indicated that there was a higher number of cement hydration crystals in GO/cement composites. Meanwhile, we also found that partially-amorphous Calcium-Silicate-Hydrate (C-S-H) gel turned into monoclinic crystals. At 28 days, the GO/cement composites reached the maximum compressive and flexural strengths at a 0.05% dosage. These strengths were 176.64 and 31.67 MPa and, compared with control samples, their increased ratios were 64.87% and 149.73%, respectively. Durability parameters, such as penetration, freeze-thaw, carbonation, drying-shrinkage value and pore structure, showed marked improvement. The results indicated that it is possible to obtain cement composites with a compact microstructure and with high performances by introducing CCS/GO intercalation composites.

Fabrication of GO/Cement Composites by Incorporation of Few-Layered GO Nanosheets and Characterization of Their Crystal/Chemical Structure and Properties

PubMed Central

Lv, Shenghua; Hu, Haoyan; Zhang, Jia; Luo, Xiaoqian; Lei, Ying; Sun, Li

2017-01-01

Original graphene oxide (GO) nanosheets were prepared using the Hummers method and found to easily aggregate in aqueous and cement composites. Using carboxymethyl chitosan (CCS) as a dispersant, few-layered GO nanosheets (1–2 layers) were obtained by forming CCS/GO intercalation composites. The testing results indicated that the few-layered GO nanosheets could uniformly spread, both in aqueous and cement composites. The cement composites were prepared with GO dosages of 0.03%, 0.05% and 0.07% and we found that they had a compact microstructure in the whole volume. A special feature was determined, namely that the microstructures consisted of regular-shaped crystals created by self-crosslinking. The X-ray diffraction (XRD) results indicated that there was a higher number of cement hydration crystals in GO/cement composites. Meanwhile, we also found that partially-amorphous Calcium-Silicate-Hydrate (C-S-H) gel turned into monoclinic crystals. At 28 days, the GO/cement composites reached the maximum compressive and flexural strengths at a 0.05% dosage. These strengths were 176.64 and 31.67 MPa and, compared with control samples, their increased ratios were 64.87% and 149.73%, respectively. Durability parameters, such as penetration, freeze-thaw, carbonation, drying-shrinkage value and pore structure, showed marked improvement. The results indicated that it is possible to obtain cement composites with a compact microstructure and with high performances by introducing CCS/GO intercalation composites. PMID:29258271
In situ measurements of the mesosphere and stratosphere

NASA Technical Reports Server (NTRS)

Crosky, C.

1976-01-01

The operation of a subsonic, Gerdien condenser probe for in situ measurements of the mesosphere and stratosphere is presented. The inclusion of a flashing Lyman alpha ultraviolet source provides an artifically produced ionization of particular constituents. Detailed theory of operation is presented and the data results from two flights are shown. A great deal of fine structure in mobility is observed due to the presence of various hydrated positive ions. The effect of the Lyman alpha source in the 35 km region was to dissociate a light hydrate ion rather than produce additional ionization. At the 70 km region, photodissociation of the heaviest ions (probably ice crystals) was also observed.
Effect of surface modification on hydration kinetics of carbamazepine anhydrate using isothermal microcalorimetry.

PubMed

Otsuka, Makoto; Ishii, Mika; Matsuda, Yoshihisa

2003-01-01

The purpose of this research was to improve the stability of carbamazepine (CBZ) bulk powder under high humidity by surface modification. The surface-modified anhydrates of CBZ were obtained in a specially designed surface modification apparatus at 60 degrees C via the adsorption of n-butanol, and powder x-ray diffraction, Fourier-Transformed Infrared spectra, and differential scanning calorimetry were used to determine the crystalline characteristics of the samples. The hydration process of intact and surface-modified CBZ anhydrate at 97% relative humidity (RH) and 40 +/-C 1 degrees C was automatically monitored by using isothermal microcalorimetry (IMC). The dissolution test for surface-modified samples (20 mg) was performed in 900 mL of distilled water at 37 +/-C 0.5 degrees C with stirring by a paddle at 100 rpm as in the Japanese Pharmacopoeia XIII. The heat flow profiles of hydration of intact and surface-modified CBZ anhydrates at 97% RH by using IMC profiles showed a maximum peak at around 10 hours and 45 hours after 0 and 10 hours of induction, respectively. The result indicated that hydration of CBZ anhydrate was completely inhibited at the initial stage by surface modification of n-butanol and thereafter transformed into dihydrate. The hydration of surface-modified samples followed a 2-dimensional phase boundary process with an induction period (IP). The IP of intact and surface-modified samples decreased with increase of the reaction temperature, and the hydration rate constant (k) increased with increase of the temperature. The crystal growth rate constants of nuclei of the intact sample were significantly larger than the surface-modified sample's at each temperature. The activation energy (E) of nuclei formation and crystal growth process for hydration of surface-modified CBZ anhydrate were evaluated to be 20.1 and 32.5 kJ/mol, respectively, from Arrhenius plots, but the Es of intact anhydrate were 56.3 and 26.8 kJ/mol, respectively. The dissolution profiles showed that the surface-modified sample dissolved faster than the intact sample at the initial stage. The dissolution kinetics were analyzed based on the Hixon-Crowell equation, and the dissolution rate constants for intact and surface-modified anhydrates were found to be 0.0102 +/-C 0.008 mg(1/3) x min(-1) and 0.1442 +/-C 0.0482 mg(1/3) x min(-1). The surface-modified anhydrate powders were more stable than the nonmodified samples under high humidity and showed resistance against moisture. However, surface modification induced rapid dissolution in water compared to the control.
Investigating the Metastability of Clathrate Hydrates for Energy Storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koh, Carolyn Ann

2014-11-18

Important breakthrough discoveries have been achieved from the DOE award on the key processes controlling the synthesis and structure-property relations of clathrate hydrates, which are critical to the development of clathrate hydrates as energy storage materials. Key achievements include: (i) the discovery of key clathrate hydrate building blocks (stable and metastable) leading to clathrate hydrate nucleation and growth; (ii) development of a rapid clathrate hydrate synthesis route via a seeding mechanism; (iii) synthesis-structure relations of H2 + CH4/CO2 binary hydrates to control thermodynamic requirements for energy storage and sequestration applications; (iv) discovery of a new metastable phase present during clathratemore » hydrate structural transitions. The success of our research to-date is demonstrated by the significant papers we have published in high impact journals, including Science, Angewandte Chemie, J. Am. Chem. Soc. Intellectual Merits of Project Accomplishments: The intellectual merits of the project accomplishments are significant and transformative, in which the fundamental coupled computational and experimental program has provided new and critical understanding on the key processes controlling the nucleation, growth, and thermodynamics of clathrate hydrates containing hydrogen, methane, carbon dioxide, and other guest molecules for energy storage. Key examples of the intellectual merits of the accomplishments include: the first discovery of the nucleation pathways and dominant stable and metastable structures leading to clathrate hydrate formation; the discovery and experimental confirmation of new metastable clathrate hydrate structures; the development of new synthesis methods for controlling clathrate hydrate formation and enclathration of molecular hydrogen. Broader Impacts of Project Accomplishments: The molecular investigations performed in this project on the synthesis (nucleation & growth)-structure-stability relations of clathrate hydrate systems are pivotal in the fundamental understanding of crystalline clathrate hydrates and the discovery of new clathrate hydrate properties and novel materials for a broad spectrum of energy applications, including: energy storage (hydrogen, natural gas); carbon dioxide sequestration; controlling hydrate formation in oil/gas transportation in subsea pipelines. The Project has also enabled the training of undergraduate, graduate and postdoctoral students in computational methods, molecular spectroscopy and diffraction, and measurement methods at extreme conditions of high pressure and low temperature.« less
Interaction of Nanostructured Calcium Silicate Hydrate with Ibuprofen Drug Molecules: X-ray Absorption Near Edge Structure (XANES) Study at the Ca, Si and O K-edge

NASA Astrophysics Data System (ADS)

Guo, X. X.; Sham, T. K.; Zhu, Y. J.; Hu, Y. F.

2013-04-01

Mesoporous calcium silicate hydrate (CSH) nanostructure has been proven to be bioactive and biocompatible, and has a bright future in the application of bone treatment among other applications. X-ray absorption near edge structure (XANES) is a powerful tool for the study of the interactions of calcium silicate hydrates with drug molecules because it is element specific and it probes the unoccupied electronic states. Herein, we report the use of the calcium, silicon and oxygen K-edge XANES spectroscopy to identify how drug molecules interact with different groups in calcium silicate hydrate mesoporous nano-carriers with different morphologies. Significant changes are observed in XANES spectra after drug loading into the calcium silicate hydrate system, especially at the Si and O K-edge. The implications of these findings are discussed.
Polyethylene oxide hydration in grafted layers

NASA Astrophysics Data System (ADS)

Dormidontova, Elena; Wang, Zilu

Hydration of water soluble polymers is one of the key-factors defining their conformation and properties, similar to biopolymers. Polyethylene oxide (PEO) is one of the most important biomedical-applications polymers and is known for its reverse temperature solubility due to hydrogen bonding with water. As in many practical applications PEO chains are grafted to surfaces, e.g. of nanoparticles or planar surfaces, it is important to understand PEO hydration in such grafted layers. Using atomistic molecular dynamic simulations we investigate the details of molecular conformation and hydration of PEO end-grafted to gold surfaces. We analyze polymer and water density distribution as a function of distance from the surface for different grafting densities. Based on a detailed analysis of hydrogen bonding between polymer and water in grafted PEO layers, we will discuss the extent of PEO hydration and its implication for polymer conformation, mobility and layer properties. This research is supported by NSF (DMR-1410928).
Methane Hydrate in Confined Spaces: An Alternative Storage System.

PubMed

Borchardt, Lars; Casco, Mirian Elizabeth; Silvestre-Albero, Joaquin

2018-06-05

Methane hydrate inheres the great potential to be a nature-inspired alternative for chemical energy storage, as it allows to store large amounts of methane in a dense solid phase. The embedment of methane hydrate in the confined environment of porous materials can be capitalized for potential applications as its physicochemical properties, such as the formation kinetics or pressure and temperature stability, are significantly changed compared to the bulk system. We review this topic from a materials scientific perspective by considering porous carbons, silica, clays, zeolites, and polymers as host structures for methane hydrate formation. We discuss the contribution of advanced characterization techniques and theoretical simulations towards the elucidation of the methane hydrate formation and dissociation process within the confined space. We outline the scientific challenges this system is currently facing and look on possible future applications for this technology. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Numerical Simulations for Enhanced Methane Recovery from Gas Hydrate Accumulations by Utilizing CO2 Sequestration

NASA Astrophysics Data System (ADS)

Sridhara, Prathyusha

In 2013, the International Energy Outlook (EIA, 2013) projected that global energy demand will grow by 56% between 2010 and 2040. Despite strong growth in renewable energy supplies, much of this growth is expected to be met by fossil fuels. Concerns ranging from greenhouse gas emissions and energy security are spawning new interests for other sources of energy including renewable and unconventional fossil fuel such as shale gas and oil as well as gas hydrates. The production methods as well as long-term reservoir behavior of gas hydrate deposits have been under extensive investigation. Reservoir simulators can be used to predict the production potentials of hydrate formations and to determine which technique results in enhanced gas recovery. In this work, a new simulation tool, Mix3HydrateResSim (Mix3HRS), which accounts for complex thermodynamics of multi-component hydrate phase comprised of varying hydrate solid crystal structure, is used to perform the CO2-assisted production technique simulations from CH4 hydrate accumulations. The simulator is one among very few reservoir simulators which can simulate the process of CH4 substitution by CO2 (and N2 ) in the hydrate lattice. Natural gas hydrate deposits around the globe are categorized into three different classes based on the characteristics of the geological sediments present in contact with the hydrate bearing deposits. Amongst these, the Class 2 hydrate accumulations predominantly confirmed in the permafrost and along seashore, are characterized by a mobile aqueous phase underneath a hydrate bearing sediment. The exploitation of such gas hydrate deposits results in release of large amounts of water due to the presence of permeable water-saturated sediments encompassing the hydrate deposits, thus lowering the produced gas rates. In this study, a suite of numerical simulation scenarios with varied complexity are considered which aimed at understanding the underlying changes in physical, thermodynamic and transport properties with change in pressure and temperature due to the presence of the simple CO2-hydrate and mixed hydrates (mainly CH4-CO2 hydrate and CH4 -CO2-N2 hydrate) in the porous geologic media. These simulations on CO2/ CH4-CO2 hydrate reservoirs provided a basic insight to formulate and interpret a novel technological approach. This approach aims at prediction of enhanced gas production profiles from Class 2 hydrate accumulations by utilizing CO2 sequestration. The approach also offers a possibility to permanently store CO 2 in the geologic formation to a greater extent compared to a direct injection of CO2 into gas hydrate sediments. The production technique implies a three-stage approach using one vertical well design. In Stage I, the CO2 is injected into the underlying aquifer. In Stage II, the well is shut in and injected CO2 is allowed to be converted into immobile CO2 hydrate. Finally, during Stage III, decomposition of CH4 hydrate is induced by the depressurization method. The gas production potential is estimated over 15 years. The results reveal that methane production is increased together with simultaneous reduction of concomitant water production rate comparing to a conventional Class 2 reservoir production.
Design of nanoengineered hybrid PVA/PNIPAm/CaCl2/SiO2-Polystyrene (PSt) colloidal crystal hydrogel coatings that sweat/rehydrate H2O from the atmosphere to give sustainable cooling and self-indicate their state

NASA Astrophysics Data System (ADS)

Eloi, Jean-Charles; Worsley, Myles P.; Sermon, Paul A.; Healy, William; Dimech, Christine

2016-09-01

The potential for nanoengineering hybrid PVA hydrogel and hydrogel microsphere optical coatings is demonstrated with fine-tuning by the addition of (i) PNIPAm domains, (ii) water-hunting humectant CaCl2, and (ii) polystyrene or SiO2 colloidal crystals. The design and application onto substrates of the hydrogel scaffold is described. The addition of a temperature-triggered component as well as humectant and NIR reflectors are reported. The hybrid hydrogels appeared effective in sustainable adsorption cooling technology (ACT) over sustained periods. It is shown that the thermoresponsive (PNIPAm) domains act as an extra reserve, sweating water above 305K, prolonging the controlled release of water. It is also reported that the addition of humectant is crucial for the natural re-hydration of the hydrogels. For the moment PNIPAm microspheres have only short- lived ACT properties. Finally, coating with microspheres (MSs) in hydrogels produces a visible-NIR reflector effect that may allow optical feedback on ACT.
Kinetics of CH4 and CO2 hydrate dissociation and gas bubble evolution via MD simulation.

PubMed

Uddin, M; Coombe, D

2014-03-20

Molecular dynamics simulations of gas hydrate dissociation comparing the behavior of CH4 and CO2 hydrates are presented. These simulations were based on a structurally correct theoretical gas hydrate crystal, coexisting with water. The MD system was first initialized and stabilized via a thorough energy minimization, constant volume-temperature ensemble and constant volume-energy ensemble simulations before proceeding to constant pressure-temperature simulations for targeted dissociation pressure and temperature responses. Gas bubble evolution mechanisms are demonstrated as well as key investigative properties such as system volume, density, energy, mean square displacements of the guest molecules, radial distribution functions, H2O order parameter, and statistics of hydrogen bonds. These simulations have established the essential similarities between CH4 and CO2 hydrate dissociation. The limiting behaviors at lower temperature (no dissociation) and higher temperature (complete melting and formation of a gas bubble) have been illustrated for both hydrates. Due to the shift in the known hydrate stability curves between guest molecules caused by the choice of water model as noted by other authors, the intermediate behavior (e.g., 260 K) showed distinct differences however. Also, because of the more hydrogen-bonding capability of CO2 in water, as reflected in its molecular parameters, higher solubility of dissociated CO2 in water was observed with a consequence of a smaller size of gas bubble formation. Additionally, a novel method for analyzing hydrate dissociation based on H-bond breakage has been proposed and used to quantify the dissociation behaviors of both CH4 and CO2 hydrates. Activation energies Ea values from our MD studies were obtained and evaluated against several other published laboratory and MD values. Intrinsic rate constants were estimated and upscaled. A kinetic reaction model consistent with macroscale fitted kinetic models has been proposed to indicate the macroscopic consequences of this analysis.
Nucleation and growth constraints and outcome in the natural gas hydrate system

NASA Astrophysics Data System (ADS)

Osegovic, J. P.; Max, M. D.

2016-12-01

Hydrate formation processes are functions of energy distribution constrained by physical and kinetic parameters. The generation of energy and energy derivative plots of a constrained growth crucible are used to demonstrate nucleation probability zones (phase origin(s)). Nucleation sets the stage for growth by further constraining the pathways through changes in heat capacity, heat flow coefficient, and enthalpy which in turn modify the mass and energy flow into the hydrate formation region. Nucleation events result from the accumulation of materials and energy relative to pressure, temperature, and composition. Nucleation induction is predictive (a frequency parameter) rather than directly dependent on time. Growth, as mass tranfer into a new phase, adds time as a direct parameter. Growth has direct feedback on phase transfer, energy dynamics, and mass export/import rates. Many studies have shown that hydrate growth is largely an equilibrium process controlled by either mass or energy flows. Subtle changes in the overall energy distribution shift the equilibrium in a predictable fashion. We will demonstrate the localization of hydrate nucleation in a reservoir followed by likely evolution of growth in a capped, sand filled environment. The gas hydrate stability zone (GHSZ) can be characterized as a semi-batch crystallizer in which nucleation and growth of natural gas hydrate (NGH) is a continuous process that may result in very large concentrations of NGH. Gas flux, or the relative concentration of hydrate-forming gas is the critical factor in a GHSZ. In an open groundwater system in which flow rate exceeds diffusion transport rate, dissolved natural gas is transported into and through the GHSZ. In a closed system, such as a geological trap, diffusion of hydrate-forming gas from a free gas zone below the GHSZ is the primary mechanism for movement of gas reactants. Because of the lower molecular weight of methane, where diffusion is the principal transport mechanism, the natural system can be a purification process for formation of increasingly pure NGH from a mixed gas solution over time.
Morphology and the Strength of Intermolecular Contact in Protein Crystals

NASA Technical Reports Server (NTRS)

Matsuura, Yoshiki; Chernov, Alexander A.

2002-01-01

The strengths of intermolecular contacts (macrobonds) in four lysozyme crystals were estimated based on the strengths of individual intermolecular interatomic interaction pairs. The periodic bond chain of these macrobonds accounts for the morphology of protein crystals as shown previously. Further in this paper, the surface area of contact, polar coordinate representation of contact site, Coulombic contribution on the macrobond strength, and the surface energy of the crystal have been evaluated. Comparing location of intermolecular contacts in different polymorphic crystal modifications, we show that these contacts can form a wide variety of patches on the molecular surface. The patches are located practically everywhere on this surface except for the concave active site. The contacts frequently include water molecules, with specific intermolecular hydrogen-bonds on the background of non-specific attractive interactions. The strengths of macrobonds are also compared to those of other protein complex systems. Making use of the contact strengths and taking into account bond hydration we also estimated crystal-water interfacial energies for different crystal faces.
Skin Hydration Assessment through Modern Non-Invasive Bioengineering Technologies

PubMed Central

CONSTANTIN, Maria-Magdalena; POENARU, Elena; POENARU, Calin; CONSTANTIN, Traian

2014-01-01

Non-invasive bioengineering technologies continuously discovered and developed in recent decades provide a significant input to research development and remarkably contribute to the improvement of medical education and care to our patients. Aim: Assessing skin hydration by using the capacitance method for a group of patients with allergic contact dermatitis versus healthy subjects, before and after applying a moisturiser (assessing the immediate and long-term effectiveness of hydration). Results: For both groups, but especially for the patients with dry skin, there was a clear improvement of hydration, statistically significant after applying the moisturiser. In the case of the patients with allergic contact dermatitis, hydration was at a maximum immediately after the first application, and then maintained an increased level after 7 and 28 days, respectively. In the healthy subjects, the increase in hydration was lower, but progressive. The moisturiser determined an increase in hydration for all age groups, but those who showed the most obvious effect were the young adults (18-29 years old) with an increase of 19.9%. The maintenance effect of hydration lasted for 28 days, while the improvement was important for allergic skin (17.1%) and significant for healthy skin (10.9%). Conclusion: The assessment of epidermal hydration performed by using the corneometer showed very good hydration of the stratum corneum for both groups studied, with immediate and long-term effect. This study also showed that the degree of skin hydration was inversely proportional with age. The corneometer is easy to use, efficient and widely utilised in international studies for measurements in healthy or pathological conditions, for quantitative assessment of the effectiveness of various preparations intended for application to the skin surface, under well-controlled and standardised conditions. PMID:25553123
Skin Hydration Assessment through Modern Non-Invasive Bioengineering Technologies.

PubMed

Constantin, Maria-Magdalena; Poenaru, Elena; Poenaru, Calin; Constantin, Traian

2014-03-01

Non-invasive bioengineering technologies continuously discovered and developed in recent decades provide a significant input to research development and remarkably contribute to the improvement of medical education and care to our patients. Assessing skin hydration by using the capacitance method for a group of patients with allergic contact dermatitis versus healthy subjects, before and after applying a moisturiser (assessing the immediate and long-term effectiveness of hydration). For both groups, but especially for the patients with dry skin, there was a clear improvement of hydration, statistically significant after applying the moisturiser. In the case of the patients with allergic contact dermatitis, hydration was at a maximum immediately after the first application, and then maintained an increased level after 7 and 28 days, respectively. In the healthy subjects, the increase in hydration was lower, but progressive. The moisturiser determined an increase in hydration for all age groups, but those who showed the most obvious effect were the young adults (18-29 years old) with an increase of 19.9%.The maintenance effect of hydration lasted for 28 days, while the improvement was important for allergic skin (17.1%) and significant for healthy skin (10.9%). The assessment of epidermal hydration performed by using the corneometer showed very good hydration of the stratum corneum for both groups studied, with immediate and long-term effect. This study also showed that the degree of skin hydration was inversely proportional with age. The corneometer is easy to use, efficient and widely utilised in international studies for measurements in healthy or pathological conditions, for quantitative assessment of the effectiveness of various preparations intended for application to the skin surface, under well-controlled and standardised conditions.
Molecular level studies on interfacial hydration of zwitterionic and other antifouling polymers in situ.

PubMed

Leng, Chuan; Sun, Shuwen; Zhang, Kexin; Jiang, Shaoyi; Chen, Zhan

2016-08-01

Antifouling polymers have wide applications in biomedical engineering and marine industry. Recently, zwitterionic materials have been reported as promising candidates for antifouling applications, while strong hydration is believed to be the key antifouling mechanism. Zwitterionic materials can be designed with various molecular structures, which affect their hydration and antifouling performance. Although strong hydration has been proposed to occur at the material surfaces, probing the solid material/water interfaces is challenging with traditional analytical techniques. Here in this review, we will review our studies on surface hydration of zwitterionic materials and other antifouling materials by using sum frequency generation (SFG) vibrational spectroscopy, which provides molecular understanding of the water structures at various material surfaces. The materials studied include zwitterionic polymer brushes with different molecular structures, amphiphilic polymers with zwitterionic groups, uncharged hydrophilic polymer brushes, amphiphilic polypeptoids, and widely used antifouling material poly(ethylene glycol). We will compare the differences among zwitterionic materials with various molecular structures as well as the differences between antifouling materials and fouling surfaces of control samples. We will also discuss the effects of pH and biological molecules like proteins on the surface hydration of the zwitterionic materials. Using SFG spectroscopy, we have measured the hydration layers of antifouling materials and found that strong hydrogen bonds are key to the formation of strong hydration layers preventing protein fouling at the polymer interfaces. Antifouling polymers have wide applications in biomedical engineering and marine industry. Recently, zwitterionic materials have been reported as promising candidates for antifouling applications, while strong hydration is believed to be the key antifouling mechanism. However, zwitterionic materials can be designed with various molecular structures, which affect their hydration and antifouling performance. Moreover, although strong hydration has been proposed to occur at the material surfaces, probing the solid material/water interfaces is challenging with traditional analytical techniques. Here in this manuscript, we will review our studies on surface hydration of zwitterionic materials and other antifouling materials by using sum frequency generation (SFG) vibrational spectroscopy, which provides molecular understanding of the water structures at various material surfaces. The materials studied include zwitterionic polymer brushes with different molecular structures, amphiphilic polymers with zwitterionic groups, uncharged hydrophilic polymer brushes, amphiphilic polypeptoids, and widely used antifouling material poly(ethylene glycol). We will compare the differences among zwitterionic materials with various molecular structures as well as the differences between antifouling materials and fouling surfaces of control samples. We will also discuss the effects of pH and biological molecules like proteins on the surface hydration of the zwitterionic materials. All the SFG results indicate that strongly hydrogen-bonded water at the materials' surfaces (strong surface hydration) is closely correlated to the good antifouling properties of the materials. This review will be widely interested by readers of Acta Biomaterialia and will impact many different research fields in chemistry, materials, engineering, and beyond. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Crystal structure and infrared spectra of dicesium trans-tetraaquadichlorochromium(III) chloride

NASA Astrophysics Data System (ADS)

Neumann, E.; Stefov, V.; Šoptrajanov, B.; Engelen, B.; Lutz, H. D.

2004-12-01

The crystal structure of dicesium trans-tetraaquadichlorochromium(III) chloride Cs 2Cr IIICl 5·4H 2O with trans-[M IIIX 2(H 2O) 4] + complex ions (space group C2/c, Z=4, a=1915.3(4) pm, b=614.1(1) pm, c=1392.0(3) pm, and β=118.24(3)°, final R1=0.0246 for 2100 unique reflections) was redetermined by single-crystal X-ray diffraction studies. It was found to crystallize in a 2c super structure of the structure reported previously (Inorg. Chem. 20 (1981) 1566; Inorg. Chem. 36 (1997) 2248). The obtained structure data now agree with the results of infrared spectroscopic studies, which has been confirmed in this work, namely that there are two different hydrate H 2O molecules in the structure. Phase transitions, static or dynamic disorder of the hydrate H 2O molecules, and space group C2/m proposed in the literature were ruled out. The coordinates of the four hydrogen positions derived from the X-ray data have been improved via the O-H distances derived from the wave numbers of the OD stretching modes of matrix isolated HDO molecules (2426, 2323, and 2306 cm -1, 263 K) by using the νOD versus rO-H correlation curve reported in the literature (J. Mol. Struct. 404 (1997) 63). The νOD versus rH⋯Cl correlation curve reported by Mikenda (J. Mol. Struct. 147 (1986) 1) should be improved, especially for strong hydrogen bonds. The two hydrate H 2O molecules of the title compound are strongly distorted with a weak and a relatively strong O-H⋯Cl hydrogen bond each thus intramolecular coupling of the two OH stretching vibrations to coupled ones is largely reduced and, hence, the wavenumbers of the OH and OD stretching modes of the HDO molecules mainly resemble those of the H 2O and D 2O molecules. The strength of the hydrogen bonds is in accordance with the predictions of the competitive and synergetic effects. Chloro ligands are weaker hydrogen bond acceptor groups than chloride ions.
Direct evidence of hydration into mantle during shearing below a trasform fault: Prince Edward transform fault, Southwest Indian Ridge

NASA Astrophysics Data System (ADS)

Michibayashi, K.; Kakihata, Y.; Dick, H. J.

2017-12-01

Southwest Indian Ridge (SWIR) is located to the southwest of Rodriguez Triple Junction, where three Indian ocean ridges meet (Zhou & Dick, 2013, Nature). SWIR is one of the slowest spreading ocean ridges in the world. In this study, we studied microstructural development of 21 peridotite samples obtained from Prince Edward transform fault of SWIR by PROTEA5 cruise in 1983. The peridotites consist dominantly of olivine, orthopyroxene and clinopyroxene with minor amounts of amphibole and plagioclase as well as secondary minerals such as serpentine and magnetite. The peridotites were classified into four groups based on their microstructures: 3 ultramylonites mostly consisting of extremely fine crystals (3-5µm), 13 heterogeneous tectonites consisting of coarse-grained crystals and fine-grained matrix, 1 cataclasite and 4 intensely serpentinized peridotites. Olivine Mg# is 0.90-0.91 and spinel Cr# is 0.1-0.35. Amphibole crystals have chemical compositions of tremolite and magnesio-hornblende and they were intensely deformed within the ultramylonites and the heterogeneous tectonites, indicating that they have occurred before or during intense shearing in mantle. Moreover, extremely fine grain sizes of olivine and microboudin textures in both pyroxene and spinel crystals suggest that these peridotites have been sheared under high stress conditions. Furthermore, olivine crystal-fabrics within the amphibole bearing peridotites have B and E types that could be developed under hydrous conditions, whereas olivine fabrics within the other peridotites have A and D types that could be developed under anhydrous conditions (Karato et al., 2008, Annu. Rev. Earth Planet. Sci.). Consequently, the petrophysical characteristics of peridotites in this study indicate that the uppermost mantle below the Prince Edward transform fault has been locally but intensely hydrated during shearing due to transform movement.
Early-age hydration and volume change of calcium sulfoaluminate cement-based binders

NASA Astrophysics Data System (ADS)

Chaunsali, Piyush

Shrinkage cracking is a predominant deterioration mechanism in structures with high surface-to-volume ratio. One way to allay shrinkage-induced stresses is to use calcium sulfoaluminate (CSA) cement whose early-age expansion in restrained condition induces compressive stress that can be utilized to counter the tensile stresses due to shrinkage. In addition to enhancing the resistance against shrinkage cracking, CSA cement also has lower carbon footprint than that of Portland cement. This dissertation aims at improving the understanding of early-age volume change of CSA cement-based binders. For the first time, interaction between mineral admixtures (Class F fly ash, Class C fly ash, and silica fume) and OPC-CSA binder was studied. Various physico-chemical factors such as the hydration of ye'elimite (main component in CSA cement), amount of ettringite (the main phase responsible for expansion in CSA cement), supersaturation with respect to ettringite in cement pore solution, total pore volume, and material stiffness were monitored to examine early-age expansion characteristics. This research validated the crystallization stress theory by showing the presence of higher supersaturation level of ettringite, and therefore, higher crystallization stress in CSA cement-based binders. Supersaturation with respect to ettringite was found to increase with CSA dosage and external supply of gypsum. Mineral admixtures (MA) altered the expansion characteristics in OPC-CSA-MA binders with fixed CSA cement. This study reports that fly ash (FA) behaves differently depending on its phase composition. The Class C FA-based binder (OPC-CSA-CFA) ceased expanding beyond two days unlike other OPC-CSA-MA binders. Three factors were found to govern expansion of CSA cement-based binders: 1) volume fraction of ettringite in given pore volume, 2) saturation level of ettringite, and 3) dynamic modulus. Various models were utilized to estimate the macroscopic tensile stress in CSA cement-based binders without taking into account the viscoelastic effects. For the first time, model based on poromechanics was used to calculate the macroscopic tensile stress that develops in CSA cement-based binders due to crystallization of ettringite. The models enabled a reasonable prediction of tensile stress due to crystallization of ettringite including the failure of an OPC-CSA binder which had high CSA cement content. Elastic strain based on crystallization stress was calculated and compared with the observed strain. A mismatch between observed and calculated elastic strain indicated the presence of early-age creep. Lastly, the application of CSA cement in concretes is discussed to link the paste and concrete behavior.
Synthesis, crystal structure and redox properties of dihydropyrazole-bridged ferrocene-based derivatives

NASA Astrophysics Data System (ADS)

Li, Heng-Dong; Ma, Zai-He; Yang, Kun; Xie, Li-Li; Yuan, Yao-Feng

2012-09-01

Dihydropyrazole-bridged ferrocene-based derivatives were prepared by corresponding chalcones with hydrazine hydrate, then acylation with 3-(ethoxycarbonyl)propionyl chloride directly in high yields and purity. All of these compounds were characterized by MS, IR, 1H NMR, 13C NMR and elemental analysis. The relationship between the structure and redox properties was investigated based on the results of single crystal X-ray structure determinations and cyclic voltammetry. The mechanism of the electron transfer for representative compound 4b was verified by density functional theory (DFT) calculations.
Synthesis and thermal conductivity of type II silicon clathrates

NASA Astrophysics Data System (ADS)

Beekman, M.; Nolas, G. S.

2006-08-01

We have synthesized and characterized polycrystalline Na 1Si 136 and Na 8Si 136, compounds possessing the type II clathrate hydrate crystal structure. Resistivity measurements from 10 to 300 K indicate very large resistivities in this temperature range, with activated temperature dependences indicative of relatively large band gap semiconductors. The thermal conductivity is very low; two orders-of-magnitude lower than that of diamond-structure silicon at room temperature. The thermal conductivity of Na 8Si 136 displays a temperature dependence that is atypical of crystalline solids and more indicative of amorphous materials. This work is part of a continuing effort to explore the many different compositions and structure types of clathrates, a class of materials that continues to be of interest for scientific and technological applications.

High Strength Phosphogypsum and Its Use as a Building Material

NASA Astrophysics Data System (ADS)

Kanno, Wellington Massayuki; Rossetto, Hebert Luis; de Souza, Milton Ferreira; Máduar, Marcelo Francis; de Campos, Marcia Pires; Mazzilli, Barbara Paci

2008-08-01

A new process (patent applied) that works equally well with both plaster of mineral gypsum and phosphogypsum for the preparation of gypsum components, UCOS, has been developed. The process consists of the following steps: humidification of plaster by fine water droplets, uni-axial compression, hydration reaction and drying. Strong hydrogen bonds develop among the crystals together with adhesion provided by confined water that accounts for nearly 70% of the adhesion forces. By reducing the plaster to water ratio to close the minimum necessary, new features are generated. An experimental house has been constructed, in which walls and ceilings have been built of gypsum and phosphogypsum. Since phosphogypsum potentially contain radioactive elements, the application of an activity concentration index to the phosphogypsum employed in the building was carried out.
Experimental Study of Sand Production and Mud Erosion Phenomena for Sand Mud Alternate Layer

NASA Astrophysics Data System (ADS)

Oyama, H.; Sato, T.

2014-12-01

Methane hydrates are crystalline, ice-like compounds under specific thermodynamic conditions. The existence of methane hydrates is confirmed in the Nankai Trough, an offshore area of Japan. Japan's Methane Hydrate Research and Development Program (MH21) has been under way at this area. In the early 2013, the world's first intentional gas production attempt from marine gas hydrate deposits was tried and accomplished in the Daini Atumi Knoll area of the Eastern Nankai Trough. For gas production, depressurization method has been considered as a promising gas production technique from methane hydrate reservoirs. However, considering of continuous gas production over a long period, there is still something to clarify. The methane hydrate crystals are very small and existed in the intergranular pores of sandy layer of turbidite sediments. When the intergranular methane hydrates will be dissociated, it is considered that dissociated gas and water flow will cause sand production and mud erosion phenomena of turbidite sediments. The production of framework sands into a well is one of the problems plaguing the gas because of its adverse effects on well productivity and equipment. If the eroded mud is accumulated in the pore space of sand, skin is generated and permeability becomes lower. In addition, mud erosion has a negative effect for the well stability. This research presents an experimental study to understand sand production and mud erosion phenomena for sand mud alternate layer. The aims of this study are to understand these phenomena and clarify driving forces. In our experiments, we used an artificial sedimentary core and performed experiments under various conditions. As the results, the driving forces of these phenomena are not dissociation gas flow but water flow through pore.
CO2 hydrate formation and dissociation in cooled porous media: a potential technology for CO2 capture and storage.

PubMed

Yang, Mingjun; Song, Yongchen; Jiang, Lanlan; Zhu, Ningjun; Liu, Yu; Zhao, Yuechao; Dou, Binlin; Li, Qingping

2013-09-03

The purpose of this study was to investigate the hydrate formation and dissociation with CO2 flowing through cooled porous media at different flow rates, pressures, temperatures, and flow directions. CO2 hydrate saturation was quantified using the mean intensity of water. The experimental results showed that the hydrate block appeared frequently, and it could be avoided by stopping CO2 flooding early. Hydrate formed rapidly as the temperature was set to 274.15 or 275.15 K, but the hydrate formation delayed when it was 276.15 K. The flow rate was an important parameter for hydrate formation; a too high or too low rate was not suitable for CO2 hydration formation. A low operating pressure was also unacceptable. The gravity made hydrate form easily in the vertically upward flow direction. The pore water of the second cycle converted to hydrate more completely than that of the first cycle, which was a proof of the hydrate "memory effect". When the pressure was equal to atmospheric pressure, hydrate did not dissociate rapidly and abundantly, and a long time or reduplicate depressurization should be used in industrial application.
Low incidence of hypercalcemia following combined calcipotriol hydrate/betamethasone dipropionate ointment treatment in Japanese patients with severe psoriasis vulgaris.

PubMed

Morita, Akimichi; Muramatsu, Shinnosuke; Kubo, Ryoji; Ikumi, Kyoko; Sagawa, Yoko; Saito, Chiyo; Torii, Kan; Nishida, Emi

2018-01-10

Topical active vitamin D3 application alone or in combination with topical steroid application is widely used to treat psoriasis. In Japan, combined calcipotriol hydrate/betamethasone dipropionate ointment has been used for patients with psoriasis vulgaris since September 2014. Current evidence regarding the incidence of hypercalcemia due to the use of this combination product, however, is insufficient. We evaluated the incidence of hypercalcemia following combined calcipotriol hydrate/betamethasone dipropionate ointment in patients with severe psoriasis vulgaris. Japanese patients (n = 22) with extensive plaque psoriasis (body surface area: 20-30%) applied the combined calcipotriol hydrate/betamethasone dipropionate ointment once daily for 8 weeks, and their serum Ca concentrations were measured periodically. The mean serum Ca concentration changed only marginally, from 9.04 ± 0.34 mg/dL before treatment to 9.08 ± 0.39 mg/dL after 8 weeks of treatment. None of the patients had an elevated serum Ca concentration throughout the study. No cases of hypercalcemia were reported as an adverse event. No correlation was detected between the amount of the combined calcipotriol hydrate/betamethasone dipropionate ointment applied and changes in the serum Ca concentration. The incidence of hypercalcemia due to topical application of a combined calcipotriol hydrate/betamethasone dipropionate ointment is low in Japanese patients with severe psoriasis vulgaris.
Phase transitions of antibiotic clarithromycin forms I, IV and new form VII crystals.

PubMed

Ito, Masataka; Shiba, Rika; Watanabe, Miteki; Iwao, Yasunori; Itai, Shigeru; Noguchi, Shuji

2018-06-01

Metastable crystal form I of the antibiotic clarithromycin has a pharmaceutically valuable characteristic that its crystalline phase transition can be applied for its sustained release from tablets. The phase transition of form I was investigated in detail by single crystal and powder X-ray analyses, dynamic vapor sorption analysis and thermal analysis. The single crystal structure of form I revealed that form I was not an anhydrate crystal but contained a partially occupied water molecule in the channel-like void space. Dynamic vapor sorption (DVS) analysis demonstrated that form I crystals reversibly sorbed water molecules in two steps when the relative humidity (RH) increased and finally transited to hydrate form IV at 95% RH. DVS analysis also showed that when the RH decreased form IV crystals lost water molecules at 40% RH and transited to the newly identified anhydrate crystal form VII. Form VII reversibly transited to form IV at lower RH than form I, suggesting that form I is more suitable for manufacturing a sustained-release tablet of CAM utilizing the crystalline phase transition. Copyright © 2018 Elsevier B.V. All rights reserved.
Characterization of methane hydrate host sediments using synchrotron-computed microtomography (CMT)

USGS Publications Warehouse

Jones, K.W.; Feng, H.; Tomov, S.; Winters, W.J.; Prodanovic, M.; Mahajan, D.

2007-01-01

The hydrate-sediment interaction is an important aspect of gas hydrate studies that needs further examination. We describe here the applicability of the computed microtomography (CMT) technique that utilizes an intense X-ray synchrotron source to characterize sediment samples, two at various depths from the Blake Ridge area (a well-known hydrate-prone region) and one from Georges Bank, that once contained methane trapped as hydrates. Detailed results of the tomographic analysis performed on the deepest sample (667??m) from Blake Ridge are presented as 2-D and 3-D images which show several mineral constituents, the internal grain/pore microstructure, and, following segmentation into pore and grain space, a visualization of the connecting pathways through the pore-space of the sediment. Various parameters obtained from the analysis of the CMT data are presented for all three sediment samples. The micro-scale porosity values showed decreasing trend with increasing depth for all three samples that is consistent with the previously reported bulk porosity data. The 3-D morphology, pore-space pathways, porosity, and permeability values are also reported for all three samples. The application of CMT is now being expanded to the laboratory-formed samples of hydrate in sediments as well as field samples of methane hydrate bearing sediments.
Improved pharmacokinetics of mercaptopurine afforded by a thermally robust hemihydrate.

PubMed

Kersten, Kortney M; Matzger, Adam J

2016-04-18

Structural and thermal data were obtained for a novel hemihydrate of 6-mercaptopurine. The hemihydrate shows increased solubility and bioavailability when compared to the monohydrate form, better stability against conversion in aqueous media than the anhydrate form, and a dehydration temperature of 240 °C, the highest of any known hydrate crystal.
How To Use Crystallographic Information in Teaching First-Year Chemistry.

ERIC Educational Resources Information Center

Bevan, D. J. M.; And Others

1988-01-01

Emphasizes the role that crystallography plays and has played in building up the body of chemical fact. Shows how the teaching of much of this material is illuminated by reference to crystal structures and crystallochemical relationships in all areas of chemistry. Discusses close packing, silicate structures, and salt hydrates. (CW)
Diclofenac salts. III. Alkaline and earth alkaline salts.

PubMed

Fini, Adamo; Fazio, Giuseppe; Rosetti, Francesca; Angeles Holgado, M; Iruín, Ana; Alvarez-Fuentes, Josefa

2005-11-01

Diclofenac salts containing the alkaline and two earth alkaline cations have been prepared and characterized by scanning electron microscopy (SEM) and EDAX spectroscopy; and by thermal and thermogravimetric analysis (TGA): all of them crystallize as hydrate when precipitated from water. The salts dehydrate at room temperature and more easily on heating, but recovery the hydration, when placed in a humid environment. X-ray diffraction spectra suggest that on dehydration new peaks appear on diffractograms and the lattice of the salts partially looses crystallinity. This phenomenon is readily visible in the case of the calcium and magnesium salts, whose thermograms display a crystallization exotherm, before melting or decomposing at temperatures near or above 200 degrees C; these last salts appear to form solvates, when prepared from methanol. The thermogram of each salt shows a complex endotherm of dehydration about 100 degrees C; the calcium salt displays two endotherms, well separated at about 120 and 160 degrees C, which disappear after prolonged heating. Decomposition exotherms, before or soon after the melting, appear below 300 degrees C. The ammonium salt is thermally unstable and, when heated to start dehydration, dissociates and leaves acidic diclofenac.
Raman scattering and X-ray powder diffraction studies of hydrate layered perovskites: dirubidium aquapentafluoromanganate(III) and dipotassium aquapentafluoroferrate(III)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Galicka, Karolina; Slodczyk, Aneta; Ratuszna, Alicja

2004-06-08

The structural and vibrational properties of above mentioned crystals were determined using X-ray powder diffraction and Raman scattering experiments. At room temperature hydrate layered perovskites: Rb{sub 2}MnF{sub 5}{center_dot}H{sub 2}O and K{sub 2}FeF{sub 5}{center_dot}H{sub 2}O exhibit orthorhombic--Cmcm (D{sub 2h}{sup 17}) and monoclinic--C2/c (C{sub 2h}{sup 6}) symmetry. Their structure is built up of MnF{sub 6} or FeF{sub 5}{center_dot}H{sub 2}O octahedra forming trans-linked zig-zag chains or hydrogen bonded zig-zag chains along the major crystallographic direction [0 0 1], respectively. To confirm crystal structures and to describe lattice dynamics of these compounds the vibrational normal modes (in {gamma} point of first Brillouin zone) weremore » calculated on the base of the group theory analysis and compared with the spectra obtained from Raman scattering experiments. A relatively good reliability was obtained for both X-ray powder diffraction and Raman scattering.« less
Effect of Hydration State of Martian Perchlorate Salts on Their Decomposition Temperatures During Thermal Extraction

NASA Astrophysics Data System (ADS)

Royle, Samuel H.; Montgomery, Wren; Kounaves, Samuel P.; Sephton, Mark A.

2017-12-01

Three Mars missions have analyzed the composition of surface samples using thermal extraction techniques. The temperatures of decomposition have been used as diagnostic information for the materials present. One compound of great current interest is perchlorate, a relatively recently discovered component of Mars' surface geochemistry that leads to deleterious effects on organic matter during thermal extraction. Knowledge of the thermal decomposition behavior of perchlorate salts is essential for mineral identification and possible avoidance of confounding interactions with organic matter. We have performed a series of experiments which reveal that the hydration state of magnesium perchlorate has a significant effect on decomposition temperature, with differing temperature releases of oxygen corresponding to different perchlorate hydration states (peak of O2 release shifts from 500 to 600°C as the proportion of the tetrahydrate form in the sample increases). Changes in crystallinity/crystal size may also have a secondary effect on the temperature of decomposition, and although these surface effects appear to be minor for our samples, further investigation may be warranted. A less than full appreciation of the hydration state of perchlorate salts during thermal extraction analyses could lead to misidentification of the number and the nature of perchlorate phases present.
Heterogeneous Nucleation of Methane Hydrate in a Water-Decane-Methane Emulsion

NASA Astrophysics Data System (ADS)

Shestakov, V. A.; Kosyakov, V. I.; Manakov, A. Yu.; Stoporev, A. S.; Grachev, E. V.

2018-07-01

Heterogeneous nucleation in disperse systems with metastable disperse phases plays an important role in the mechanisms of environmental and technological processes. The effect the concentration and activity of particles that initiate the formation of a new phase have on nucleation processes in such systems is considered. An approach is proposed that allows construction of a spectrum of particle activity characterizing the features of nucleation in a sample, based on the fraction of crystallized droplets depending on the level of supercooling and the use of Weibull's distribution. The proposed method is used to describe experimental data on the heterogeneous nucleation of methane hydrate in an emulsion in a water-decane-methane system.
Lattice strains and load partitioning in bovine trabecular bone.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akhtar, R.; Daymond, M. R.; Almer, J. D.

2012-02-01

Microdamage and failure mechanisms have been well characterized in bovine trabecular bone. However, little is known about how elastic strains develop in the apatite crystals of the trabecular struts and their relationship with different deformation mechanisms. In this study, wide-angle high-energy synchrotron X-ray diffraction has been used to determine bulk elastic strains under in situ compression. Dehydrated bone is compared to hydrated bone in terms of their response to load. During compression, load is initially borne by trabeculae aligned parallel to loading direction with non-parallel trabeculae deforming by bending. Ineffective load partitioning is noted in dehydrated bone whereas hydrated bonemore » behaves like a plastically yielding foam« less
Implication of seismic attenuation for gas hydrate resource characterization, Mallik, Mackenzie Delta, Canada

NASA Astrophysics Data System (ADS)

Bellefleur, G.; Riedel, M.; Brent, T.; Wright, F.; Dallimore, S. R.

2007-10-01

Wave attenuation is an important physical property of hydrate-bearing sediments that is rarely taken into account in site characterization with seismic data. We present a field example showing improved images of hydrate-bearing sediments on seismic data after compensation of attenuation effects. Compressional quality factors estimated from zero-offset Vertical Seismic Profiling data acquired at Mallik, Northwest Territories, Canada, demonstrate significant wave attenuation for hydrate-bearing sediments. These results are in agreement with previous attenuation estimates obtained from sonic logs and crosshole data at different frequency intervals. The application of an inverse Q-filter to compensate attenuation effects of permafrost and hydrate-bearing sediments improved the resolution of surface 3D seismic data and its correlation with log data, particularly for the shallowest gas hydrate interval. Compensation of the attenuation effects of the permafrost likely explains most of the improvements for the shallow gas hydrate zone. Our results show that characterization of the Mallik gas hydrates with seismic data not corrected for attenuation would tend to overestimate thicknesses and lateral extent of hydrate-bearing strata and hence, the volume of hydrates in place.
High-level expression and deuteration of sperm whale myoglobin: A study of its solvent structure by X-ray and neutron diffraction methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shu, F.; Ramakrishnan, V.; Schoenborn, B.P.

1994-12-31

Neutron diffraction has become one of the best ways to study light atoms, such as hydrogens. Hydrogen however has a negative coherent scattering factor, and a large incoherent scattering factor, while deuterium has virtually no incoherent scattering, but a large positive coherent scattering factor. Beside causing high background due to its incoherent scattering, the negative coherent scattering of hydrogen tends to cancel out the positive contribution from other atoms in a neutron density map. Therefore a fully deuterated sample will yield better diffraction data with stronger density in the hydrogen position. On this basis, a sperm whale myoglobin gene modifiedmore » to include part of the A cII protein gene has been cloned into the T7 expression system. Milligram amounts of fully deuterated holo-myoglobin have been obtained and used for crystallization. The synthetic sperm whale myoglobin crystallized in P2{sub 1} space group isomorphous with the native protein crystal. A complete X-ray diffraction dataset at 1.5{Angstrom} has been collected. This X-ray dataset, and a neutron data set collected previously on a protonated carbon-monoxymyoglobin crystal have been used for solvent structure studies. Both X-ray and neutron data have shown that there are ordered hydration layers around the protein surface. Solvent shell analysis on the neutron data further has shown that the first hydration layer behaves differently around polar and apolar regions of the protein surface. Finally, the structure of per-deuterated myoglobin has been refined using all reflections to a R factor of 17%.« less
How the hydrophobic factor drives protein folding

PubMed Central

Baldwin, Robert L.; Rose, George D.

2016-01-01

How hydrophobicity (HY) drives protein folding is studied. The 1971 Nozaki–Tanford method of measuring HY is modified to use gases as solutes, not crystals, and this makes the method easy to use. Alkanes are found to be much more hydrophobic than rare gases, and the two different kinds of HY are termed intrinsic (rare gases) and extrinsic (alkanes). The HY values of rare gases are proportional to solvent-accessible surface area (ASA), whereas the HY values of alkanes depend on special hydration shells. Earlier work showed that hydration shells produce the hydration energetics of alkanes. Evidence is given here that the transfer energetics of alkanes to cyclohexane [Wolfenden R, Lewis CA, Jr, Yuan Y, Carter CW, Jr (2015) Proc Natl Acad Sci USA 112(24):7484–7488] measure the release of these shells. Alkane shells are stabilized importantly by van der Waals interactions between alkane carbon and water oxygen atoms. Thus, rare gases cannot form this type of shell. The very short (approximately picoseconds) lifetime of the van der Waals interaction probably explains why NMR efforts to detect alkane hydration shells have failed. The close similarity between the sizes of the opposing energetics for forming or releasing alkane shells confirms the presence of these shells on alkanes and supports Kauzmann's 1959 mechanism of protein folding. A space-filling model is given for the hydration shells on linear alkanes. The model reproduces the n values of Jorgensen et al. [Jorgensen WL, Gao J, Ravimohan C (1985) J Phys Chem 89:3470–3473] for the number of waters in alkane hydration shells. PMID:27791131
Pore-scale Numerical Simulation Using Lattice Boltzmann Method for Mud Erosion in Methane Hydrate Bearing Layers

NASA Astrophysics Data System (ADS)

Yoshida, T.; Sato, T.; Oyama, H.

2014-12-01

Methane hydrates in subsea environments near Japan are believed to new natural gas resources. These methane hydrate crystals are very small and existed in the intergranular pores of sandy sediments in sand mud alternate layers. For gas production, several processes for recovering natural gas from the methane hydrate in a sedimentary reservoir have been proposed, but almost all technique are obtain dissociated gas from methane hydrates. When methane hydrates are dissociated, gas and water are existed. These gas and water are flown in pore space of sand mud alternate layers, and there is a possibility that the mud layer is eroded by these flows. It is considered that the mad erosion causes production trouble such as making skins or well instability. In this study, we carried out pore scale numerical simulation to represent mud erosion. This research aims to develop a fundamental simulation method based on LBM (Lattice Boltzmann Method). In the simulation, sand particles are generated numerically in simulation area which is approximately 200x200x200μm3. The periodic boundary condition is used except for mud layers. The water/gas flow in pore space is calculated by LBM, and shear stress distribution is obtained at the position flow interacting mud surface. From this shear stress, we consider that the driving force of mud erosion. As results, mud erosion can be reproduced numerically by adjusting the parameters such as critical shear stress. We confirmed that the simulation using LBM is appropriate for mud erosion.
Effects of various vehicles on skin hydration in vivo.

PubMed

Wiedersberg, S; Leopold, C S; Guy, R H

2009-01-01

The stratum corneum, the outermost layer of the skin, regulates the passive loss of water to the environment. Furthermore, it is well accepted that drug penetration is influenced by skin hydration, which may be manipulated by the application of moisturizing or oleaginous vehicles. Measurements of transepidermal water loss (TEWL), and of skin hydration using a corneometer, were used to assess the effect of different vehicles on stratum corneum barrier function in vivo in human volunteers. A microemulsion significantly increased skin hydration relative to a reference vehicle based on medium chain triglycerides; in contrast, Transcutol(R) lowered skin hydration. TEWL measurements confirmed these observations. Copyright 2009 S. Karger AG, Basel.
Crystal structure of bis-(2-{[1,1-bis-(hy-droxy-meth-yl)-2-oxidoeth-yl]imino-meth-yl}-6-meth-oxy-phenolato)manganese(IV) 0.39-hydrate.

PubMed

Buvaylo, Elena A; Vassilyeva, Olga Yu; Skelton, Brian W

2015-11-01

The title compound, [Mn(C12H15NO5)2]·0.39H2O, is a 0.39 hydrate of the isostructural complex bis-(2-{[1,1-bis-(hy-droxy-meth-yl)-2-oxidoeth-yl]imino-meth-yl}-6-meth-oxy-phenolato)manganese(IV) that has previously been reported by Back, Oliveira, Canabarro & Iglesias [Z. Anorg. Allg. Chem. (2015), 641, 941-947], based on room-temperature data. The current structure that was determined at 100 K reveals a lengthening of the c cell parameter compared with the published one due to the incorporation of the partial occupancy water mol-ecule. The title compound crystallizes in the tetra-gonal chiral space group P41212; the neutral [Mn(IV)(C12H15NO5)2] mol-ecule is situated on a crystallographic C 2 axis. The overall geometry about the central manganese ion is octa-hedral with an N2O4 core; each ligand acts as a meridional ONO donor. The coordination environment of Mn(IV) at 100 K displays a difference in one of the two Mn-O bond lengths, compared with the room-temperature structure. In the crystal, the neutral mol-ecules are stacked in a helical fashion along the c-axis direction.
Niclosamide methanol solvate and niclosamide hydrate: structure, solvent inclusion mode and implications for properties.

PubMed

Harriss, Bethany I; Wilson, Claire; Radosavljevic Evans, Ivana

2014-08-01

Structural studies have been carried out of two solid forms of niclosamide [5-chloro-N-(2-chloro-4-nitrophenyl)-2-hydroxybenzamide, NCL], a widely used anthelmintic drug, namely niclosamide methanol monosolvate, C13H8Cl2N2O4·CH3OH or NCL·MeOH, and niclosamide monohydrate, denoted HA. The structure of the methanol solvate obtained from single-crystal X-ray diffraction is reported for the first time, elucidating the key host-guest hydrogen-bonding interactions which lead to solvate formation. The essentially planar NCL host molecules interact via π-stacking and pack in a herringbone-type arrangement, giving rise to channels along the crystallographic a axis in which the methanol guest molecules are located. The methanol and NCL molecules interact via short O-H...O hydrogen bonds. Laboratory powder X-ray diffraction (PXRD) measurements reveal that the initially phase-pure NCL·MeOH solvate readily transforms into NCL monohydrate within hours under ambient conditions. PXRD further suggests that the NCL monohydrate, HA, is isostructural with the NCL·MeOH solvate. This is consistent with the facile transformation of the methanol solvate into the hydrate when stored in air. The crystal packing and the topology of guest-molecule inclusion are compared with those of other NCL solvates for which the crystal structures are known, giving a consistent picture which correlates well with known experimentally observed desolvation properties.

Highly improved hydration level sensing properties of copper oxide films with sodium and potassium doping

NASA Astrophysics Data System (ADS)

Sahin, Bünyamin; Kaya, Tolga

2016-01-01

In this study, un-doped, Na-doped, and K-doped nanostructured CuO films were successfully synthesized by the successive ionic layer adsorption and reaction (SILAR) technique and then characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and current-voltage (I-V) measurements. Structural properties of the CuO films were affected from doping. The XRD pattern indicates the formation of polycrystalline CuO films with no secondary phases. Furthermore, doping affected the crystal structure of the samples. The optimum conductivity values for both Na and K were obtained at 4 M% doping concentrations. The comparative hydration level sensing properties of the un-doped, Na-doped, and K-doped CuO nanoparticles were also investigated. A significant enhancement in hydration level sensing properties was observed for both 4 M% Na and K-doped CuO films for all concentration levels. Detailed discussions were reported in the study regarding atomic radii, crystalline structure, and conductivity.
Managing Salmonella Typhimurium and Escherichia coli O157:H7 in soil with hydrated lime - An outdoor study in lysimeters and field plots.

PubMed

Nyberg, Karin A; Vinnerås, Björn; Albihn, Ann

2014-01-01

An outbreak of Salmonella Typhimurium or E. coli O157:H7 among domestic animals can have great financial consequences for an animal enterprise but also be a threat for public health as there is a risk for transmission of the infection through the environment. In order to minimize disease transmission, it is important to treat not only the affected animals but also the areas on which they have been kept. In the present study, the effect of hydrated lime as a treatment for Salmonella Typhimurium or E. coli O157:H7 contaminated soil was investigated. The study was performed outdoors, in a lysimeter system and in field plots. The soils were spiked with Salmonella Typhimurium and/or E. coli O157:H7 and hydrated lime was added at three different concentrations (0.5, 1 and 2%). Sampling was performed over one month, and the levels of bacteria were analyzed by standard culture methods. In addition, the soil pH was monitored throughout the study. The results showed that application of 0.5-1 kg hydrated lime per m(2) reduced both Salmonella Typhimurium and E. coli O157:H7 numbers to below the detection limit (2 log10 CFU g-1 soil) in 3-7 days. Lower application rates of hydrated lime did not reduce pathogen numbers in the lysimeter study, but in the field plots no E. coli O157:H7 was detected at the end of the four-week study period regardless of hydrated lime application. A recommended strategy for treating a Salmonella Typhimurium or E. coli O157:H7 contaminated soil could therefore be to monitor the pH over the time of treatment and to repeat hydrated lime application if a decrease in pH is observed.
[Prospects for Application of Gases and Gas Hydrates to Cryopreservation].

PubMed

Shishova, N V; Fesenko, E E

2015-01-01

In the present review, we tried to evaluate the known properties of gas hydrates and gases participating in the formation of gas hydrates from the point of view of the mechanisms of cryoinjury and cryoprotection, to consider the papers on freezing biological materials in the presence of inert gases, and to analyze the perspectives for the development of this direction. For the purpose, we searched for the information on the physical properties of gases and gas hydrates, compared processes occured during the formation of gas hydrates and water ice, analyzed the influence of the formation and growth of gas hydrates on the structure of biological objects. We prepared a short review on the biological effects of xenon, krypton, argon, carbon dioxide, hydrogen sulfide, and carbon monoxide especially on hypothermal conditions and probable application of these properties in cryopreservation technologies. The description of the existing experiments on cryopreservation of biological objects with the use of gases was analyzed. On the basis of the information we found, the most perspective directions of work in the field of cryopreservation of biological objects with the use of gases were outlined. An attempt was made to forecast the potential problems in this field.
Design, characterization, and clinical evaluation of argan oil nanostructured lipid carriers to improve skin hydration

PubMed Central

Tichota, Deise Michele; Silva, Ana Catarina; Sousa Lobo, José Manuel; Amaral, Maria Helena

2014-01-01

Given its advantages in skin application (eg, hydration, antiaging, and protection), argan oil could be used in both dermatological and cosmetic formulations. Therefore, the preparation of nanostructured lipid carriers (NLCs) using argan oil as a liquid lipid is a promising technique, since the former constitute well-established systems for dermal delivery. The aim of this work was to develop a topical formulation of argan oil NLCs to improve skin hydration. Firstly an NLC dispersion was developed and characterized, and afterward an NLC-based hydrogel was prepared. The in vivo evaluation of the suitability of the prepared formulation for the proposed application was assessed in volunteers, by measuring different skin-surface parameters for 1 month. An argan oil NLC-based hydrogel formulation was successfully prepared and characterized. Moreover, the entrapment of the NLCs in the hydrogel net did not affect their colloidal sizes. Additionally, it was observed that this formulation precipitated an increase in skin hydration of healthy volunteers. Therefore, we concluded that the preparation of NLC systems using argan oil as the liquid lipid is a promising strategy, since a synergistic effect on the skin hydration was obtained (ie, NLC occlusion plus argan oil hydration). PMID:25143733
Design, characterization, and clinical evaluation of argan oil nanostructured lipid carriers to improve skin hydration.

PubMed

Tichota, Deise Michele; Silva, Ana Catarina; Sousa Lobo, José Manuel; Amaral, Maria Helena

2014-01-01

Given its advantages in skin application (eg, hydration, antiaging, and protection), argan oil could be used in both dermatological and cosmetic formulations. Therefore, the preparation of nanostructured lipid carriers (NLCs) using argan oil as a liquid lipid is a promising technique, since the former constitute well-established systems for dermal delivery. The aim of this work was to develop a topical formulation of argan oil NLCs to improve skin hydration. Firstly an NLC dispersion was developed and characterized, and afterward an NLC-based hydrogel was prepared. The in vivo evaluation of the suitability of the prepared formulation for the proposed application was assessed in volunteers, by measuring different skin-surface parameters for 1 month. An argan oil NLC-based hydrogel formulation was successfully prepared and characterized. Moreover, the entrapment of the NLCs in the hydrogel net did not affect their colloidal sizes. Additionally, it was observed that this formulation precipitated an increase in skin hydration of healthy volunteers. Therefore, we concluded that the preparation of NLC systems using argan oil as the liquid lipid is a promising strategy, since a synergistic effect on the skin hydration was obtained (ie, NLC occlusion plus argan oil hydration).
Nanoplate-like tungsten trioxide (hydrate) films prepared by crystal-seed-assisted hydrothermal reaction

NASA Astrophysics Data System (ADS)

Wang, P.; Yang, L.; Dai, B.; Yang, Z.; Guo, S.; Zhu, J.

2017-07-01

Vertically-aligned WO3 nanoplates on transparent conducting fluorine-doped tin oxide (FTO) glass were prepared by a facile template-free crystal-seed-assisted hydrothermal method. The effects of the hydrothermal temperature and reaction time on the crystal structure and morphology of the products were investigated by XRD and SEM. The XRD results showed that the as-prepared thin films obtained below 150∘C comprised orthorhombic WO3 ṡ H2O and completely converted to monoclinic WO3 at 180∘C. It was also noted that there was a phase transformation from orthorhombic to monoclinic by increasing the reaction time from 1 to 12 h. SEM analysis revealed that WO3 thin films are composed of plate-like nanostructures.
Transformation mechanism of amorphous calcium carbonate into calcite in the sea urchin larval spicule.

PubMed

Politi, Yael; Metzler, Rebecca A; Abrecht, Mike; Gilbert, Benjamin; Wilt, Fred H; Sagi, Irit; Addadi, Lia; Weiner, Steve; Gilbert, P U P A; Gilbert, Pupa

2008-11-11

Sea urchin larval spicules transform amorphous calcium carbonate (ACC) into calcite single crystals. The mechanism of transformation is enigmatic: the transforming spicule displays both amorphous and crystalline properties, with no defined crystallization front. Here, we use X-ray photoelectron emission spectromicroscopy with probing size of 40-200 nm. We resolve 3 distinct mineral phases: An initial short-lived, presumably hydrated ACC phase, followed by an intermediate transient form of ACC, and finally the biogenic crystalline calcite phase. The amorphous and crystalline phases are juxtaposed, often appearing in adjacent sites at a scale of tens of nanometers. We propose that the amorphous-crystal transformation propagates in a tortuous path through preexisting 40- to 100-nm amorphous units, via a secondary nucleation mechanism.
The occurence of uric acids and the growth morphology of the anhydrous monoclinic modification : C 5H 4N 4O 3

NASA Astrophysics Data System (ADS)

Rinaudo, C.; Boistelle, R.

1980-07-01

Anhydrous and hydrated uric acid crystals which frequently occur in human urolithiasis have been grown from pure aqueous solutions at 25 and 37°C. The appearance domain of either modification is given as a function of initial uric acid concentration at pH values ranging from 3.0 to 5.5. The present paper mostly deals with the anhydrous phase and it is shown that its experimental and theoretical growth morphologies are in agreement, the crystals exhibiting the {100}, {210}, {121}, {001} and {201} forms. Crystal habit depends on supersaturation; {100} has always the largest extension at low supersaturation {121} develops to the detriment of {210}, {001} and {201}.
Computation of methodology-independent single-ion solvation properties from molecular simulations. IV. Optimized Lennard-Jones interaction parameter sets for the alkali and halide ions in water

NASA Astrophysics Data System (ADS)

Reif, Maria M.; Hünenberger, Philippe H.

2011-04-01

The raw single-ion solvation free energies computed from atomistic (explicit-solvent) simulations are extremely sensitive to the boundary conditions and treatment of electrostatic interactions used during these simulations. However, as shown recently [M. A. Kastenholz and P. H. Hünenberger, J. Chem. Phys. 124, 224501 (2006), 10.1529/biophysj.106.083667; M. M. Reif and P. H. Hünenberger, J. Chem. Phys. 134, 144103 (2010)], the application of appropriate correction terms permits to obtain methodology-independent results. The corrected values are then exclusively characteristic of the underlying molecular model including in particular the ion-solvent van der Waals interaction parameters, determining the effective ion size and the magnitude of its dispersion interactions. In the present study, the comparison of calculated (corrected) hydration free energies with experimental data (along with the consideration of ionic polarizabilities) is used to calibrate new sets of ion-solvent van der Waals (Lennard-Jones) interaction parameters for the alkali (Li+, Na+, K+, Rb+, Cs+) and halide (F-, Cl-, Br-, I-) ions along with either the SPC or the SPC/E water models. The experimental dataset is defined by conventional single-ion hydration free energies [Tissandier et al., J. Phys. Chem. A 102, 7787 (1998), 10.1021/jp982638r; Fawcett, J. Phys. Chem. B 103, 11181] along with three plausible choices for the (experimentally elusive) value of the absolute (intrinsic) hydration free energy of the proton, namely, Δ G_hyd^{ominus }[H+] = -1100, -1075 or -1050 kJ mol-1, resulting in three sets L, M, and H for the SPC water model and three sets LE, ME, and HE for the SPC/E water model (alternative sets can easily be interpolated to intermediate Δ G_hyd^{ominus }[H+] values). The residual sensitivity of the calculated (corrected) hydration free energies on the volume-pressure boundary conditions and on the effective ionic radius entering into the calculation of the correction terms is also evaluated and found to be very limited. Ultimately, it is expected that comparison with other experimental ionic properties (e.g., derivative single-ion solvation properties, as well as data concerning ionic crystals, melts, solutions at finite concentrations, or nonaqueous solutions) will permit to validate one specific set and thus, the associated Δ G_hyd^{ominus }[H+] value (atomistic consistency assumption). Preliminary results (first-peak positions in the ion-water radial distribution functions, partial molar volumes of ionic salts in water, and structural properties of ionic crystals) support a value of Δ G_hyd^{ominus }[H+] close to -1100 kJ.mol-1.
In vacuo X-ray data collection from graphene-wrapped protein crystals.

PubMed

Warren, Anna J; Crawshaw, Adam D; Trincao, Jose; Aller, Pierre; Alcock, Simon; Nistea, Ioana; Salgado, Paula S; Evans, Gwyndaf

2015-10-01

The measurement of diffraction data from macromolecular crystal samples held in vacuo holds the promise of a very low X-ray background and zero absorption of incident and scattered beams, leading to better data and the potential for accessing very long X-ray wavelengths (>3 Å) for native sulfur phasing. Maintaining the hydration of protein crystals under vacuum is achieved by the use of liquid jets, as with serial data collection at free-electron lasers, or is side-stepped by cryocooling the samples, as implemented at new synchrotron beamlines. Graphene has been shown to protect crystals from dehydration by creating an extremely thin layer that is impermeable to any exchanges with the environment. Furthermore, owing to its hydrophobicity, most of the aqueous solution surrounding the crystal is excluded during sample preparation, thus eliminating most of the background caused by liquid. Here, it is shown that high-quality data can be recorded at room temperature from graphene-wrapped protein crystals in a rough vacuum. Furthermore, it was observed that graphene protects crystals exposed to different relative humidities and a chemically harsh environment.
In situ thermal conductivity of gas-hydrate-bearing sediments of the Mallik 5L-38 well

NASA Astrophysics Data System (ADS)

Henninges, J.; Huenges, E.; Burkhardt, H.

2005-11-01

Detailed knowledge about thermal properties of rocks containing gas hydrate is required in order to quantify processes involving gas hydrate formation and decomposition in nature. In the framework of the Mallik 2002 program, three wells penetrating a continental gas hydrate occurrence under permafrost were successfully equipped with permanent fiber-optic distributed temperature sensing cables. Temperature data were collected over a 21-month period after completing the wells. Thermal conductivity profiles were calculated from the geothermal data as well as from a petrophysical model derived from the available logging data and application of mixing law models. Results indicate that thermal conductivity variations are mainly lithologically controlled with a minor influence from hydrate saturation. Average thermal conductivity values of the hydrate-bearing sediments range between 2.35 and 2.77 W m-1 K-1. Maximum gas hydrate saturations can reach up to about 90% at an average porosity of 0.3.
Assessment of viscoelasticity and hydration effect of herbal moisturizers using bioengineering techniques

PubMed Central

Kapoor, Shweta; Saraf, Swarnlata

2010-01-01

Background: A number of moisturizers are available containing natural hydrating, moisturizing, fi rming and occlusive property-imparting agent in the form of herbal extracts, juice and oils. The aim of this study is to assess the hydration and viscoelastic effect of commercially available herbal moisturizers, containing different herbs, on human skin, after a single and 3-week period of application using skin bio mechanical and electrical techniques. Materials and Methods: Twenty selected herbal moisturizers (HM) were coded as HM1-HM20. Forty volunteers, mean age of 40 ± 9 years, were participated in the short- and long-term study. Skin properties in terms of hydration and viscoelastic parameters were measured by multitester and cutometer, respectively. Measurements were done before and after 1, 2, and 3 h (single application) and for the 3-week period of daily application. Results: After single application, significant increase has been observed in both the skin electrical (P < 0.001) and mechanical properties (P < 0.01) as compared to the control, at which no products were applied. After the 3-week period, both effects are maintained and found to be significant at P < 0.001. Short-and long-term study revealed that out of 20 herbal moisturizers, HM8 and HM10 show pronounced increase in skin hydration (90-100%) and HM8, HM10, and HM11 shown marked increase in skin viscoelasticity (90-95%). Conclsuion: The possible reason of maximum effects obtained by these products is multifunctional effects of active ingredients of incorporated herbs. Combined used of both non invasive techniques is useful to substantiate the hydrating and viscoelasticity claim of herbal moisturizer. Short- and long-terms study revealed the best performing herbal moisturizer. PMID:21120032
The effect of topical anesthetic hydration on the depth of thermal injury from the plasma skin regeneration device.

PubMed

Sanderson, Alicia R; Wu, Edward C; Liaw, Lih-Huei L; Garg, Rohit; Gangnes, Richard A

2014-02-01

The plasma skin regeneration (PSR) device delivers thermal energy to the skin by converting nitrogen gas to plasma. Prior to treatment, hydration of the skin is recommended as it is thought to limit the zone of thermal damage. However, there is limited data on optimal hydration time. This pilot study aims to determine the effect of topical anesthetic application time on the depth of thermal injury from a PSR device using histology. PSR (1.8 and 3.5 J) was performed after 0, 30, or 60 minutes of topical anesthetic application. Rhytidectomy was then performed and skin was fixed for histologic analysis. Four patients (two control and four treatment sites per patient) undergoing rhytidectomy were recruited for the study. Each patient served as his/her own control (no hydration). A scoring system for tissue injury was developed. Epidermal injury, the presence of vacuolization, blistering, damage to adnexal structures, and depth of dermal collagen changes were evaluated in over 1,400 high-power microscopy fields. There was a significant difference in the average thermal injury score, depth of thermal damage, and epidermal injury when comparing controls to 30 minutes of hydration (P = 0.012, 0.012, 0.017, respectively). There was no statistical difference between controls and 60 minutes of hydration or between 30 and 60 minutes of hydration. Epidermal vacuolization at low energy and patchy distribution of thermal injury was also observed. Topical hydration influences the amount of thermal damage when applied to skin for 30 minutes prior to treatment with the PSR device. There was a trend toward decreasing thermal damage at 60 minutes, and there was no difference between treatment for 30 or 60 minutes. The data suggest that application of topical anesthetic for a short period of time prior to treatment with the PSR device is cost-effective, safe, and may be clinically beneficial. © 2013 Wiley Periodicals, Inc.
Mobile Technology Application for Improved Urine Concentration Measurement Pilot Study.

PubMed

Walawender, Laura; Patterson, Jeremy; Strouse, Robert; Ketz, John; Saxena, Vijay; Alexy, Emily; Schwaderer, Andrew

2018-01-01

Objectives: Low hydration has a deleterious effect on many conditions. In the absence of a urine concentrating defect, urine concentration is a marker of hydration status. However, markers to evaluate hydration status have not been well studied in children. The objectives of this paper are to compare measures of thirst and urine concentration in children and to develop a novel mobile technology application to measure urine concentration. Study Design: Children age 12-17 years were selected ( n = 21) for this pilot study. Thirst perception, specific gravity (automated dipstick analysis and refractometer), and urine color scale results were correlated to urine osmolality. The technology department developed a mobile technology camera application to measure light penetrance into urine which was tested on 25 random anonymized urine samples. Results: The patients' thirst perception and color scale as well as two researchers color scale did not significantly correlate with osmolality. Correlation between osmolality and hydration markers resulted in the following Pearson coefficients: SG automated dipstick, 0.61 ( P 0.003); SG refractometer, 0.98 ( P < 0.0001); urine color scale (patient), 0.37 ( P 0.10), and light penetrance, -0.77 ( P < 0.0001). The correlation of light penetrance with osmolality was stronger than all measures except SG by refractometer and osmolality. Conclusion: The mobile technology application may be a more accurate tool for urine concentration measurement than specific gravity by automated dipstick, subjective thirst, and urine color scale, but lags behind specific gravity measured by refractometer. The mobile technology application is a step toward patient oriented hydration strategies.
An evaluation of the antiaging properties of strawberry hydrolysate treatment enriched with L-ascorbic acid applied with microneedle mesotherapy.

PubMed

Markiewicz, Agata; Zasada, Malwina; Erkiert-Polguj, Anna; Wieckowska-Szakiel, Marzena; Budzisz, Elzbieta

2018-04-16

Mature skin is characterized by a loss of elasticity, hyperpigmentation, and dehydration. L-ascorbic acid stimulates the synthesis of collagen type I, inhibits melanogenesis, and helps to maintain correct skin hydration. Combining microneedle mesotherapy with the application of preparations rich in vitamin C results in better therapeutic effects due to the improved absorption of active substances. The study evaluates the effectiveness of the application of strawberry hydrolysate enriched with L-ascorbic acid using microneedle mesotherapy. Seventeen volunteers aged 45-70 years underwent a series of four microneedle mesotherapy treatments with vitamin C serum, performed every 10 days. The 20% L-ascorbic acid solution (pH = 3.5) was prepared immediately before application. After the treatment, the participants gave a subjective assessment of the effectiveness. Cutometer ® was used to measure skin elasticity and firmness, Corneometer ® to measure skin hydration, and Mexameter ® skin tone. The results of the survey showed improvements in skin hydration and elasticity. In vivo studies confirmed the effectiveness of serum and the impact of the active substance on skin firmness and elasticity, the degree of hydration and skin tone. Microneedling with vitamin C improves skin tone, hydratation and firmness, and decreases the visibility of hyperpigmentation. © 2018 Wiley Periodicals, Inc.
Clathrate hydrate tuning for technological purposes

NASA Astrophysics Data System (ADS)

di Profio, Pietro; Germani, Raimondo; Savelli, Gianfranco

2010-05-01

Gas hydrates are being increasingly considered as convenient media for gas storage and transportation as the knowledge of their properties increases, in particular as relates to methane and hydrogen. Clathrate hydrates may also represent a feasible sequestration technology for carbon dioxide, due to a well defined P/T range of stability, and several research programs are addressing this possibility. Though the understanding of the molecular structure and supramolecular interactions which are responsible of most properties of hydrates have been elucitated in recent years, the underlying theoretical physico-chemical framework is still poor, especially as relates to the role of "conditioners" (inhibitors and promoters) from the molecular/supramolecular point of view. In the present communication we show some results from our research approach which is mainly focused on the supramolecular properties of clathrate hydrate systems - and their conditioners - as a way to get access to a controlled modulation of the formation, dissociation and stabilization of gas hydrates. In particular, this communication will deal with: (a) a novel, compact apparatus for studying the main parameters of formation and dissociation of gas hydrates in a one-pot experiment, which can be easily and rapidly carried out on board of a drilling ship;[1] (b) the effects of amphiphile molecules (surfactants) as inhibitors or promoters of gas hydrate formation;[2] (c) a novel nanotechnology for a reliable and quick production of hydrogen hydrates, and its application to fuel cells;[3,4] and (d) the development of a clathrate hydrate tecnology for the sequestration and geological storage of man-made CO2, possibly with concomitant recovery of natural gas from NG hydrate fields. Furthermore, the feasibility of catalyzing the reduction of carbon dioxide to energy-rich species by hydrates is being investigated. [1] Di Profio, P., Germani, R., Savelli, G., International Patent Application PCT/IT2006/000274 [2] Di Profio P., Arca S., Germani R., Savelli G., 2005, "Surfactant promoting effects on clathrate hydrate formation: are micelles really involved?", Chem. Eng. Sci., 60, pp. 4141-4145 [3] Di Profio P., Arca S., Germani R., Savelli G., 2006, "Novel Nanostructured Media for Gas Storage and Transport: Clathrate Hydrates of Methane and Hydrogen", J. Fuel Cell Sci. & Tech., February 2007, vol. 4. [4] Di Profio, P., Germani, R., Savelli, G., EP07010346.
Equilibrium, Kinetics, and Spectroscopic Studies of SF6 Hydrate in NaCl Electrolyte Solution.

PubMed

Seo, Youngrok; Moon, Donghyun; Lee, Changho; Park, Jeong-Woo; Kim, Byeong-Soo; Lee, Gang-Woo; Dotel, Pratik; Lee, Jong-Won; Cha, Minjun; Yoon, Ji-Ho

2015-05-19

Many studies have focused on desalination via hydrate formation; however, for their potential application, knowledge pertaining to thermodynamic stability, formation kinetics, and guest occupation behavior in clathrate hydrates needs to be determined. Herein, the phase equilibria of SF6 hydrates in the presence of NaCl solutions (0, 2, 4, and 10 wt %) were monitored in the temperature range of 277-286 K and under pressures of up to 1.4 MPa. The formation kinetics of SF6 hydrates in the presence of NaCl solutions (0, 2, and 4 wt %) was also investigated. Gas consumption curves of SF6 hydrates showed that a pure SF6 hydrate system allowed fast hydrate growth as well as high conversion yield, whereas SF6 hydrate in the presence of NaCl solutions showed retarded hydrate growth rate as well as low conversion yield. In addition, structural identification of SF6 hydrates with and without NaCl solutions was performed using spectroscopic tools such as Raman spectroscopy and X-ray diffraction. The Raman spectrometer was also used to evaluate the temperature-dependent release behavior of guest molecules in SF6 and SF6 + 4 wt % NaCl hydrates. The results indicate that whereas SF6 hydrate starts to decompose at around 240 K, the escape of SF6 molecules in SF6 + 4 wt % NaCl hydrate is initiated rapidly at around 205 K. The results of this study can provide a better understanding of guest-host interaction in electrolyte-containing systems.
Overview: Nucleation of clathrate hydrates

NASA Astrophysics Data System (ADS)

Warrier, Pramod; Khan, M. Naveed; Srivastava, Vishal; Maupin, C. Mark; Koh, Carolyn A.

2016-12-01

Molecular level knowledge of nucleation and growth of clathrate hydrates is of importance for advancing fundamental understanding on the nature of water and hydrophobic hydrate formers, and their interactions that result in the formation of ice-like solids at temperatures higher than the ice-point. The stochastic nature and the inability to probe the small length and time scales associated with the nucleation process make it very difficult to experimentally determine the molecular level changes that lead to the nucleation event. Conversely, for this reason, there have been increasing efforts to obtain this information using molecular simulations. Accurate knowledge of how and when hydrate structures nucleate will be tremendously beneficial for the development of sustainable hydrate management strategies in oil and gas flowlines, as well as for their application in energy storage and recovery, gas separation, carbon sequestration, seawater desalination, and refrigeration. This article reviews various aspects of hydrate nucleation. First, properties of supercooled water and ice nucleation are reviewed briefly due to their apparent similarity to hydrates. Hydrate nucleation is then reviewed starting from macroscopic observations as obtained from experiments in laboratories and operations in industries, followed by various hydrate nucleation hypotheses and hydrate nucleation driving force calculations based on the classical nucleation theory. Finally, molecular simulations on hydrate nucleation are discussed in detail followed by potential future research directions.
Communication: Quantitative Fourier-transform infrared data for competitive loading of small cages during all-vapor instantaneous formation of gas-hydrate aerosols

NASA Astrophysics Data System (ADS)

Uras-Aytemiz, Nevin; Abrrey Monreal, I.; Devlin, J. Paul

2011-10-01

A simple method has been developed for the measurement of high quality FTIR spectra of aerosols of gas-hydrate nanoparticles. The application of this method enables quantitative observation of gas hydrates that form on subsecond timescales using our all-vapor approach that includes an ether catalyst rather than high pressures to promote hydrate formation. The sampling method is versatile allowing routine studies at temperatures ranging from 120 to 210 K of either a single gas or the competitive uptake of different gas molecules in small cages of the hydrates. The present study emphasizes hydrate aerosols formed by pulsing vapor mixtures into a cold chamber held at 160 or 180 K. We emphasize aerosol spectra from 6 scans recorded an average of 8 s after "instantaneous" hydrate formation as well as of the gas hydrates as they evolve with time. Quantitative aerosol data are reported and analyzed for single small-cage guests and for mixed hydrates of CO2, CH4, C2H2, N2O, N2, and air. The approach, combined with the instant formation of gas hydrates from vapors only, offers promise with respect to optimization of methods for the formation and control of gas hydrates.
Overview: Nucleation of clathrate hydrates.

PubMed

Warrier, Pramod; Khan, M Naveed; Srivastava, Vishal; Maupin, C Mark; Koh, Carolyn A

2016-12-07

Molecular level knowledge of nucleation and growth of clathrate hydrates is of importance for advancing fundamental understanding on the nature of water and hydrophobic hydrate formers, and their interactions that result in the formation of ice-like solids at temperatures higher than the ice-point. The stochastic nature and the inability to probe the small length and time scales associated with the nucleation process make it very difficult to experimentally determine the molecular level changes that lead to the nucleation event. Conversely, for this reason, there have been increasing efforts to obtain this information using molecular simulations. Accurate knowledge of how and when hydrate structures nucleate will be tremendously beneficial for the development of sustainable hydrate management strategies in oil and gas flowlines, as well as for their application in energy storage and recovery, gas separation, carbon sequestration, seawater desalination, and refrigeration. This article reviews various aspects of hydrate nucleation. First, properties of supercooled water and ice nucleation are reviewed briefly due to their apparent similarity to hydrates. Hydrate nucleation is then reviewed starting from macroscopic observations as obtained from experiments in laboratories and operations in industries, followed by various hydrate nucleation hypotheses and hydrate nucleation driving force calculations based on the classical nucleation theory. Finally, molecular simulations on hydrate nucleation are discussed in detail followed by potential future research directions.

Probing methane hydrate nucleation through the forward flux sampling method.

PubMed

Bi, Yuanfei; Li, Tianshu

2014-11-26

Understanding the nucleation of hydrate is the key to developing effective strategies for controlling methane hydrate formation. Here we present a computational study of methane hydrate nucleation, by combining the forward flux sampling (FFS) method and the coarse-grained water model mW. To facilitate the application of FFS in studying the formation of methane hydrate, we developed an effective order parameter λ on the basis of the topological analysis of the tetrahedral network. The order parameter capitalizes the signature of hydrate structure, i.e., polyhedral cages, and is capable of efficiently distinguishing hydrate from ice and liquid water while allowing the formation of different hydrate phases, i.e., sI, sII, and amorphous. Integration of the order parameter λ with FFS allows explicitly computing hydrate nucleation rates and obtaining an ensemble of nucleation trajectories under conditions where spontaneous hydrate nucleation becomes too slow to occur in direct simulation. The convergence of the obtained hydrate nucleation rate was found to depend crucially on the convergence of the spatial distribution for the spontaneously formed hydrate seeds obtained from the initial sampling of FFS. The validity of the approach is also verified by the agreement between the calculated nucleation rate and that inferred from the direct simulation. Analyzing the obtained large ensemble of hydrate nucleation trajectories, we show hydrate formation at 220 K and 500 bar is initiated by the nucleation events occurring in the vicinity of water-methane interface, and facilitated by a gradual transition from amorphous to crystalline structure. The latter provides the direct support to the proposed two-step nucleation mechanism of methane hydrate.
Analysis of mixed-layer clay mineral structures

USGS Publications Warehouse

Bradley, W.F.

1953-01-01

Among the enormously abundant natural occurrences of clay minerals, many examples are encountered in which no single specific crystallization scheme extends through a single ultimate grain. The characterization of such assemblages becomes an analysis of the distribution of matter within such grains, rather than the simple identification of mineral species. It having become established that the particular coordination complex typified by mica is a common component of many natural subcrystalline assemblages, the opportunity is afforded to analyze scattering from random associations of these complexes with other structural units. Successful analyses have been made of mixed hydration states of montmorillonite, of montmorillonite with mica, of vermiculite with mica, and of montmorillonite with chlorite, all of which are variants of the mica complex, and of halloysite with hydrated halloysite.
Experimental determination of the kinetics of formation of the benzene-ethane co-crystal and implications for Titan

NASA Astrophysics Data System (ADS)

Cable, Morgan L.; Vu, Tuan H.; Hodyss, Robert; Choukroun, Mathieu; Malaska, Michael J.; Beauchamp, Patricia

2014-08-01

Benzene is found on Titan and is a likely constituent of the putative evaporite deposits formed around the hydrocarbon lakes. We have recently demonstrated the formation of a benzene-ethane co-crystal under Titan-like surface conditions. Here we investigate the kinetics of formation of this new structure as a function of temperature. We show that the formation process would reach completion under Titan surface conditions in ~18 h and that benzene precipitates from liquid ethane as the co-crystal. This suggests that benzene-rich evaporite basins around ethane/methane lakes and seas may not contain pure crystalline benzene, but instead benzene-ethane co-crystals. This co-crystalline form of benzene with ethane represents a new class of materials for Titan's surface, analogous to hydrated minerals on Earth. This new structure may also influence evaporite characteristics such as particle size, dissolution rate, and infrared spectral properties.
Communication: Fourier-transform infrared probing of remarkable quantities of gas trapped in cold homogeneously nucleated nanodroplets.

PubMed

Uras-Aytemiz, Nevin; Devlin, J Paul

2013-07-14

Studies of catalyzed all-vapor gas-hydrate formation on a sub-second timescale have been extended with a special focus on liquid-droplet compositions at the instant of hydrate crystallization. This focus has been enabled by inclusion of methanol in the all-vapor mixture. This slows droplet to gas-hydrate conversion near 200 K to a time scale suited for standard FTIR sampling. Such droplet data are sought as a guide to ongoing efforts to reduce the amount of guest catalyst required for instant formation of the gas hydrates. For the same reason, all-vapor sampling has also been extended to the generation of long-lived liquid droplets with reduced or no water content. Observations of single-solvent droplets show that surprising quantities of gas molecules are trapped during rapid droplet growth. For example, CO2 is trapped at levels near 50 mol. % in droplets of acetone, tetrahydrofuran, or trimethylene oxide formed under CO2 pressures of several Torr in a cold-chamber at 170 K. Less but significant amounts of gas are trapped at higher temperatures, or in methanol or water-methanol droplets. The droplet metastability appears to commonly lead to formation of bubbles larger than the original nanodroplets. Besides serving as a guide for the all-vapor gas-hydrate studies, the semiquantitative evidence of extensive trapping of gases is expected to have a role in future studies of atmospheric aerosols.
Communication: Fourier-transform infrared probing of remarkable quantities of gas trapped in cold homogeneously nucleated nanodroplets

NASA Astrophysics Data System (ADS)

Uras-Aytemiz, Nevin; Devlin, J. Paul

2013-07-01

Studies of catalyzed all-vapor gas-hydrate formation on a sub-second timescale have been extended with a special focus on liquid-droplet compositions at the instant of hydrate crystallization. This focus has been enabled by inclusion of methanol in the all-vapor mixture. This slows droplet to gas-hydrate conversion near 200 K to a time scale suited for standard FTIR sampling. Such droplet data are sought as a guide to ongoing efforts to reduce the amount of guest catalyst required for instant formation of the gas hydrates. For the same reason, all-vapor sampling has also been extended to the generation of long-lived liquid droplets with reduced or no water content. Observations of single-solvent droplets show that surprising quantities of gas molecules are trapped during rapid droplet growth. For example, CO2 is trapped at levels near 50 mol. % in droplets of acetone, tetrahydrofuran, or trimethylene oxide formed under CO2 pressures of several Torr in a cold-chamber at 170 K. Less but significant amounts of gas are trapped at higher temperatures, or in methanol or water-methanol droplets. The droplet metastability appears to commonly lead to formation of bubbles larger than the original nanodroplets. Besides serving as a guide for the all-vapor gas-hydrate studies, the semiquantitative evidence of extensive trapping of gases is expected to have a role in future studies of atmospheric aerosols.
Bioactive Wollastonite-Diopside Foams from Preceramic Polymers and Reactive Oxide Fillers

PubMed Central

Fiocco, Laura; Elsayed, Hamada; Ferroni, Letizia; Gardin, Chiara; Zavan, Barbara; Bernardo, Enrico

2015-01-01

Wollastonite (CaSiO3) and diopside (CaMgSi2O6) silicate ceramics have been widely investigated as highly bioactive materials, suitable for bone tissue engineering applications. In the present paper, highly porous glass-ceramic foams, with both wollastonite and diopside as crystal phases, were developed from the thermal treatment of silicone polymers filled with CaO and MgO precursors, in the form of micro-sized particles. The foaming was due to water release, at low temperature, in the polymeric matrix before ceramic conversion, mainly operated by hydrated sodium phosphate, used as a secondary filler. This additive proved to be “multifunctional”, since it additionally favored the phase development, by the formation of a liquid phase upon firing, in turn promoting the ionic interdiffusion. The liquid phase was promoted also by the incorporation of powders of a glass crystallizing itself in wollastonite and diopside, with significant improvements in both structural integrity and crushing strength. The biological characterization of polymer-derived wollastonite-diopside foams, to assess the bioactivity of the samples, was performed by means of a cell culture test. The MTT assay and LDH activity tests gave positive results in terms of cell viability.
cis-(Acetato-κ2 O,O′)(5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane-κ4 N,N′,N′′,N′′′)nickel(II) perchlorate monohydrate

PubMed Central

Roy, Tapashi G.; Palit, Debashis; Nath, Babul Chandra; Ng, Seik Weng; Tiekink, Edward R. T.

2012-01-01

The complete cation in the title hydrated molecular salt, [Ni(CH3CO2)(C16H36N4)]ClO4·H2O, is generated by the application of crystallographic twofold symmetry; the perchlorate anion and water molecule are each disordered around a twofold axis. The NiII atom exists within a cis-N4O2 donor set based on a strongly distorted octahedron and defined by the four N atoms of the macrocyclic ligand and two O atoms of a symmetrically coordinating acetate ligand. In the crystal, hydrogen bonding (water–acetate/perchlorate O—H⋯O and amine–perchlorate N—H⋯O) leads to layers in the ab plane. The layers stack along the c axis, being connected by C—H⋯O(water) interactions. The crystal studied was found to be a non-merohedral twin; the minor component refined to 15.9 (6)%. PMID:22589873
Diffusive, Displacive Deformations and Local Phase Transformation Govern the Mechanics of Layered Crystals: The Case Study of Tobermorite.

PubMed

Tao, Lei; Shahsavari, Rouzbeh

2017-07-19

Understanding the deformation mechanisms underlying the mechanical behavior of materials is the key to fundamental and engineering advances in materials' performance. Herein, we focus on crystalline calcium-silicate-hydrates (C-S-H) as a model system with applications in cementitious materials, bone-tissue engineering, drug delivery and refractory materials, and use molecular dynamics simulation to investigate its loading geometry dependent mechanical properties. By comparing various conventional (e.g. shear, compression and tension) and nano-indentation loading geometries, our findings demonstrate that the former loading leads to size-independent mechanical properties while the latter results in size-dependent mechanical properties at the nanometer scales. We found three key mechanisms govern the deformation and thus mechanics of the layered C-S-H: diffusive-controlled and displacive-controlled deformation mechanisms, and strain gradient with local phase transformations. Together, these elaborately classified mechanisms provide deep fundamental understanding and new insights on the relationship between the macro-scale mechanical properties and underlying molecular deformations, providing new opportunities to control and tune the mechanics of layered crystals and other complex materials such as glassy C-S-H, natural composite structures, and manmade laminated structures.
Inhibited phase behavior of gas hydrates in graphene oxide: influences of surface and geometric constraints.

PubMed

Kim, Daeok; Kim, Dae Woo; Lim, Hyung-Kyu; Jeon, Jiwon; Kim, Hyungjun; Jung, Hee-Tae; Lee, Huen

2014-11-07

Porous materials have provided us unprecedented opportunities to develop emerging technologies such as molecular storage systems and separation mechanisms. Pores have also been used as supports to contain gas hydrates for the application in gas treatments. Necessarily, an exact understanding of the properties of gas hydrates in confining pores is important. Here, we investigated the formation of CO2, CH4 and N2 hydrates in non-interlamellar voids in graphene oxide (GO), and their thermodynamic behaviors. For that, low temperature XRD and P-T traces were conducted to analyze the water structure and confirm hydrate formation, respectively, in GO after its exposure to gaseous molecules. Confinement and strong interaction of water with the hydrophilic surface of graphene oxide reduce water activity, which leads to the inhibited phase behavior of gas hydrates.
An effective medium inversion algorithm for gas hydrate quantification and its application to laboratory and borehole measurements of gas hydrate-bearing sediments

NASA Astrophysics Data System (ADS)

Chand, Shyam; Minshull, Tim A.; Priest, Jeff A.; Best, Angus I.; Clayton, Christopher R. I.; Waite, William F.

2006-08-01

The presence of gas hydrate in marine sediments alters their physical properties. In some circumstances, gas hydrate may cement sediment grains together and dramatically increase the seismic P- and S-wave velocities of the composite medium. Hydrate may also form a load-bearing structure within the sediment microstructure, but with different seismic wave attenuation characteristics, changing the attenuation behaviour of the composite. Here we introduce an inversion algorithm based on effective medium modelling to infer hydrate saturations from velocity and attenuation measurements on hydrate-bearing sediments. The velocity increase is modelled as extra binding developed by gas hydrate that strengthens the sediment microstructure. The attenuation increase is modelled through a difference in fluid flow properties caused by different permeabilities in the sediment and hydrate microstructures. We relate velocity and attenuation increases in hydrate-bearing sediments to their hydrate content, using an effective medium inversion algorithm based on the self-consistent approximation (SCA), differential effective medium (DEM) theory, and Biot and squirt flow mechanisms of fluid flow. The inversion algorithm is able to convert observations in compressional and shear wave velocities and attenuations to hydrate saturation in the sediment pore space. We applied our algorithm to a data set from the Mallik 2L-38 well, Mackenzie delta, Canada, and to data from laboratory measurements on gas-rich and water-saturated sand samples. Predictions using our algorithm match the borehole data and water-saturated laboratory data if the proportion of hydrate contributing to the load-bearing structure increases with hydrate saturation. The predictions match the gas-rich laboratory data if that proportion decreases with hydrate saturation. We attribute this difference to differences in hydrate formation mechanisms between the two environments.
An effective medium inversion algorithm for gas hydrate quantification and its application to laboratory and borehole measurements of gas hydrate-bearing sediments

USGS Publications Warehouse

Chand, S.; Minshull, T.A.; Priest, J.A.; Best, A.I.; Clayton, C.R.I.; Waite, W.F.

2006-01-01

The presence of gas hydrate in marine sediments alters their physical properties. In some circumstances, gas hydrate may cement sediment grains together and dramatically increase the seismic P- and S-wave velocities of the composite medium. Hydrate may also form a load-bearing structure within the sediment microstructure, but with different seismic wave attenuation characteristics, changing the attenuation behaviour of the composite. Here we introduce an inversion algorithm based on effective medium modelling to infer hydrate saturations from velocity and attenuation measurements on hydrate-bearing sediments. The velocity increase is modelled as extra binding developed by gas hydrate that strengthens the sediment microstructure. The attenuation increase is modelled through a difference in fluid flow properties caused by different permeabilities in the sediment and hydrate microstructures. We relate velocity and attenuation increases in hydrate-bearing sediments to their hydrate content, using an effective medium inversion algorithm based on the self-consistent approximation (SCA), differential effective medium (DEM) theory, and Biot and squirt flow mechanisms of fluid flow. The inversion algorithm is able to convert observations in compressional and shear wave velocities and attenuations to hydrate saturation in the sediment pore space. We applied our algorithm to a data set from the Mallik 2L–38 well, Mackenzie delta, Canada, and to data from laboratory measurements on gas-rich and water-saturated sand samples. Predictions using our algorithm match the borehole data and water-saturated laboratory data if the proportion of hydrate contributing to the load-bearing structure increases with hydrate saturation. The predictions match the gas-rich laboratory data if that proportion decreases with hydrate saturation. We attribute this difference to differences in hydrate formation mechanisms between the two environments.
Scanning electron microscopy of high-pressure-frozen sea urchin embryos.

PubMed

Walther, P; Chen, Y; Malecki, M; Zoran, S L; Schatten, G P; Pawley, J B

1993-12-01

High-pressure-freezing permits direct cryo-fixation of sea urchin embryos having a defined developmental state without the formation of large ice crystals. We have investigated preparation protocols for observing high-pressure-frozen and freeze-fractured samples in the scanning electron microscope. High-pressure-freezing was superior to other freezing protocols, because the whole bulk sample was reasonably well frozen and the overall three-dimensional shape of the embryos was well preserved. The samples were either dehydrated by freeze-substitution and critical-point-drying, or imaged in the partially hydrated state, using a cold stage in the SEM. During freeze-substitution the samples were stabilized by fixatives. The disadvantage of this method was that shrinking and extraction effects, caused by the removal of the water, could not be avoided. These disadvantages were avoided when the sample was imaged in the frozen-hydrated state using a cold-stage in the SEM. This would be the method of choice for morphometric studies. Frozen-hydrated samples, however, were very beam sensitive and many structures remained covered by the ice and were not visible. Frozen-hydrated samples were partially freeze-dried to make visible additional structures that had been covered by ice. However, this method also caused drying artifacts when too much water was removed.
Study of lip hydration with application of photoprotective lipstick: influence of skin phototype, size of lips, age, sex and smoking habits.

PubMed

López-Jornet, Pía; Camacho-Alonso, Fabio; Rodríguez-Espin, Ana

2010-05-01

To study lip hydration levels when applying a lipstick sunscreen for 3 months and to evaluate the influence of size of lips, age, sex, smoking and skin phototype. The study group was formed by 140 volunteer subjects, one group consisting of 70 patients applying a commercial lipstick sunscreen three times a day and the other group of 70 controls in which no product was applied. The age range was 20-86 years. The influence in lip hydration levels of age, sex, phototype, size of the lips and smoking habits was studied using a Corneometer 825 (Courage & Khazaka Electronic GmbH, Cologne, Germany). An increase in lip hydration was found between the basal (53.49 +/- 15.259) and final (59.34 +/- 14.51) Corneometer 825 (Courage & Khazaka Electronic GmbH, Cologne, Germany) measurements over the three months of treatment, with statistically significant differences with respect to the control (p=0.002). However, no statistically significant differences in lip hydration were observed with regard to age, (p=0.48), gender (p=0.876), skin phototype (p=0.653), lip area (p=0.291) and smoking (p=0.178). Application of a lipstick sunscreen 3 times a day for 3 months increases lip hydration.
The influence of sucrose on the crystallization behaviour in the system CaO-SiO{sub 2}-C{sub 12}H{sub 22}O{sub 11}-H{sub 2}O under hydrothermal conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hartmann, A., E-mail: a.hartmann@baustoff.uni-hannover.de; Buhl, J.-Ch.

2010-04-15

Hydrothermal synthesis in the presence of sucrose has been carried out at 200 {sup o}C and autogeneous pressure in the system CaO-SiO{sub 2}-C{sub 12}H{sub 22}O{sub 11}-H{sub 2}O to investigate the influence of C{sub 12}H{sub 22}O{sub 11} on phase formation and the crystal habit of calcium silicate hydrates (CSH-phases). A sucrose/lime ratio of 0.5 was utilized in all experiments and the reactivity of the SiO{sub 2} source was varied using educts of different grain size of {approx}40 mesh and >230 mesh. CaO/SiO{sub 2} concentration ratios of 0.5 and 0.8 have been selected, the latter with respect to the composition of themore » important CSH-phase 11 A tobermorite. The results were compared with experiments under similar but sucrose-free conditions. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX-analysis) as well as Fourier transform infrared spectroscopy (FTIR-spectroscopy) have been applied for analyses. A retarding effect of sucrose on CSH-phase formation has been observed. Only minor amount of CSH without regular morphology was observed instead of typically fibrous 11 A tobermorite formed in the sucrose-free system. Sucrose altered the reaction mechanism in the CSH-system and hydrothermal process started with rapid reaction of sucrose and lime. The further course of crystallization was dominated by an extended precipitation of calcium carbonate and small amounts of calcium oxalate hydrate. Formation of these stable hydrothermal decomposition products of saccharated lime is strongly suppressing the CSH-crystallization.« less
Development of media for dynamic latent heat storage for the low-temperature range. Part 1: Thermal analyses of selected salt hydrate systems

NASA Technical Reports Server (NTRS)

Kanwischer, H.; Tamme, R.

1985-01-01

Phase change temperatures and phase change enthalpies of seventeen salt hydrates, three double salts, and four eutectics were measured thermodynamically and the results reported herein. Good results were obtained, especially for congruently melting salt hydrates. Incongruently melting salt hydrates appear less suitable for heat storage applications. The influence of the second phase - water, acid and hydroxide - to the latent heat is described. From these results, basic values of the working temperatures and storage capabilities of various storage media compositions may be derived.
Isotopic Insights Into the Degassing and Secondary Hydration Rates of Volcanic Glass From the 1980 Eruptions of Mount St. Helens

NASA Astrophysics Data System (ADS)

Seligman, A. N.; Bindeman, I. N.; Van Eaton, A. R.; Hoblitt, R. P.

2016-12-01

Following eruption, volcanic glass undergoes hydration in its depositional environment, which overprints the history of magmatic degassing recorded in the glass. However, the rates of secondary hydration of volcanic glass used for paleoclimate studies are poorly constrained. Here, we present our results of a natural experiment using products of the 1980 eruptions of Mount St. Helens. We measured the δD of extracted water and the δ18O of the bulk glass of samples collected during the dry summer months of 1980 and compared them with material resampled in August of 2015. Results demonstrate that only samples collected from the subsurface near gas escape pipes show elevated water concentrationss (near 2.0 wt.%) and low δD (-110 to -130 ‰) and δ18O (6.0 to 6.6 ‰) values, and that the initial process of secondary hydration is not always a simple addition of low δD waters at ambient temperature. On average, the 2015 surface samples have slightly higher water contents (0.1-0.2 wt.%) and similar δ18O (6.8 - 6.9 ‰) to those collected in 1980. Given the moderate vesicularity of the samples and the slow rate of surface temperature diffusion, we attribute these observations to hydration during cooling, with only little exchange after. We also compare our results to rapidly quenched air fall pumice from the May 18th eruption, which shows moderate δD values (-74 ‰) and water concentrations (0.3 wt.%) that are closer to those for the 1980 samples. Surprisingly, the 2015 surface samples show higher δD values (+15 ‰), which we attribute to any of four possibilities: (1) evaporation or (2) degassing of underlying deposits; (3) exchange of hydrogen with local vegetation; and/or (4) microlite crystallization that aided diffusion of water. Reconstructed δD-H2O trends for the Mount St. Helens samples collected in 1980 support previous studies proposing that exsolved volatiles were trapped within a rapidly rising magma that degassed at shallow depths. The dacitic Mount St. Helens (with rhyolitic groundmass) trend overlaps with crystal-poor rhyolitic eruptions studied previously, suggesting similar behavior of volatiles upon exsolution.
Transformation mechanism of amorphous calcium carbonate into calcite in the sea urchin larval spicule

PubMed Central

Politi, Yael; Metzler, Rebecca A.; Abrecht, Mike; Gilbert, Benjamin; Wilt, Fred H.; Sagi, Irit; Addadi, Lia; Weiner, Steve; Gilbert, P. U. P. A.

2008-01-01

Sea urchin larval spicules transform amorphous calcium carbonate (ACC) into calcite single crystals. The mechanism of transformation is enigmatic: the transforming spicule displays both amorphous and crystalline properties, with no defined crystallization front. Here, we use X-ray photoelectron emission spectromicroscopy with probing size of 40–200 nm. We resolve 3 distinct mineral phases: An initial short-lived, presumably hydrated ACC phase, followed by an intermediate transient form of ACC, and finally the biogenic crystalline calcite phase. The amorphous and crystalline phases are juxtaposed, often appearing in adjacent sites at a scale of tens of nanometers. We propose that the amorphous-crystal transformation propagates in a tortuous path through preexisting 40- to 100-nm amorphous units, via a secondary nucleation mechanism. PMID:18987314
Neutron and X-ray single-crystal diffraction from protein microcrystals via magnetically oriented microcrystal arrays in gels.

PubMed

Tsukui, Shu; Kimura, Fumiko; Kusaka, Katsuhiro; Baba, Seiki; Mizuno, Nobuhiro; Kimura, Tsunehisa

2016-07-01

Protein microcrystals magnetically aligned in D2O hydrogels were subjected to neutron diffraction measurements, and reflections were observed for the first time to a resolution of 3.4 Å from lysozyme microcrystals (∼10 × 10 × 50 µm). This result demonstrated the possibility that magnetically oriented microcrystals consolidated in D2O gels may provide a promising means to obtain single-crystal neutron diffraction from proteins that do not crystallize at the sizes required for neutron diffraction structure determination. In addition, lysozyme microcrystals aligned in H2O hydrogels allowed structure determination at a resolution of 1.76 Å at room temperature by X-ray diffraction. The use of gels has advantages since the microcrystals are measured under hydrated conditions.
The Structure of Glycine Dihydrate: Implications for the Crystallization of Glycine from Solution and Its Structure in Outer Space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Wenqian; Zhu, Qiang; Hu, Chunhua Tony

2017-01-18

Glycine, the simplest amino acid, is also the most polymorphous. Herein, we report the structure determination of an unknown phase of glycine which was firstly reported by Pyne and Suryanarayanan in 2001. To date, the new phase has only been prepared at 208 K as nanocrystals within ice. Through computational crystal structure prediction and powder X-ray diffraction methods, we identified this elusive phase as glycine dihydrate (GDH), representing a first report on a hydrated glycine structure. The structure of GDH has important implications for the state of glycine in aqueous solution, and the mechanisms of glycine crystallization. GDH may alsomore » be the form of glycine that comes to Earth from extraterrestrial sources.« less
Determination of the moisture content in the fluoride oxide fluxes of electroslag remelting

NASA Astrophysics Data System (ADS)

Vdovin, K. N.; Feoktistov, N. A.; Pivovarova, K. G.; Deryabin, D. A.

2016-12-01

ANF-32 flux has been studied with regard to the moisture content both after storage and upon operation. A simple and reliable procedure for the determination of the moisture content in ESR fluxes is proposed, and recommendations are given on monitoring the moisture content in calcined fluxes. The main sources of crystallization water of hydration are hydrogen sources.

Conformational analysis of flavonoids: crystal and molecular structures of morin hydrate and myricetin (1:2) triphenylphosphine oxide complex

NASA Astrophysics Data System (ADS)

Cody, Vivian; Luft, Joseph R.

1994-01-01

The crystal and molecular structures of morin (2',3,4',5,7-pentahydroxyflavone) hydrate ( I), and myricetin (3',4',5',3,5,7-hexahydroxyflavone) triphenylphosphine oxide (TPPO) (1:2) co-crystal complex ( II) have been studied by X-ray analysis and AM1 molecular orbital methods. The molecular conformation of the two flavones described by the torsion angle θ[C(3)-C(2)-C(1t')-C(2')] between the benzopyrone and phenyl ring is -43.3° and 51.0° for molecules A and B of morin, respectively, and -37.0° for myricetin. Minimum energy conformations from AM1 molecular orbital calculations have θ values of -38.2° for morin and -27.0° for myricetin. The energy profile for rotation about θ for morin has a 28 kcal mol -1 barrier at 0° due to steric interactions between the 2'-hydroxy and the 3-hydroxy group. There are two local minima near 30 and 140°, in good agreement with structural results. The profile for myricetin has two equivalent minima near 30 and 150° with a barrier of less than 2 kcal mol -1. In the crystal both flavones form extensive networks of intra- and intermolecular hydrogen bonds. In ( I), each morin conformer packs in alternating layers linked by water molecules, while in ( II), TPPO stabilizes the crystal by formation of short hydrogen bonds (2.58-2.65 Å) of the phosphoryl oxygen to the flavone. Myricetin also forms a two dimensional sheet-like packing in which myricetin molecules hydrogen bond to each other, as well as to TPPO. These conformational and hydrogen bonding patterns provide insight into specific types of ligand-receptor interactions and support structure activity data which suggest the importance of electronic and hydrogen bonding properties in the bioactivity of flavones.
Polymorph Impact on the Bioavailability and Stability of Poorly Soluble Drugs.

PubMed

Censi, Roberta; Di Martino, Piera

2015-10-15

Drugs with low water solubility are predisposed to poor and variable oral bioavailability and, therefore, to variability in clinical response, that might be overcome through an appropriate formulation of the drug. Polymorphs (anhydrous and solvate/hydrate forms) may resolve these bioavailability problems, but they can be a challenge to ensure physicochemical stability for the entire shelf life of the drug product. Since clinical failures of polymorph drugs have not been uncommon, and some of them have been entirely unexpected, the Food and Drug Administration (FDA) and the International Conference on Harmonization (ICH) has required preliminary and exhaustive screening studies to identify and characterize all the polymorph crystal forms for each drug. In the past, the polymorphism of many drugs was detected fortuitously or through manual time consuming methods; today, drug crystal engineering, in particular, combinatorial chemistry and high-throughput screening, makes it possible to easily and exhaustively identify stable polymorphic and/or hydrate/dehydrate forms of poorly soluble drugs, in order to overcome bioavailability related problems or clinical failures. This review describes the concepts involved, provides examples of drugs characterized by poor solubility for which polymorphism has proven important, outlines the state-of-the-art technologies and discusses the pertinent regulations.
Probing the dynamic nature of water molecules and their influences on ligand binding in a model binding site.

PubMed

Cappel, Daniel; Wahlström, Rickard; Brenk, Ruth; Sotriffer, Christoph A

2011-10-24

The model binding site of the cytochrome c peroxidase (CCP) W191G mutant is used to investigate the structural and dynamic properties of the water network at the buried cavity using computational methods supported by crystallographic analysis. In particular, the differences of the hydration pattern between the uncomplexed state and various complexed forms are analyzed as well as the differences between five complexes of CCP W191G with structurally closely related ligands. The ability of docking programs to correctly handle the water molecules in these systems is studied in detail. It is found that fully automated prediction of water replacement or retention upon docking works well if some additional preselection is carried out but not necessarily if the entire water network in the cavity is used as input. On the other hand, molecular interaction fields for water calculated from static crystal structures and hydration density maps obtained from molecular dynamics simulations agree very well with crystallographically observed water positions. For one complex, the docking and MD results sensitively depend on the quality of the starting structure, and agreement is obtained only after redetermination of the crystal structure and refinement at higher resolution.
Hydration level dependence of the microscopic dynamics of water adsorbed in ultramicroporous carbon

DOE PAGES

Mamontov, Eugene; Yue, Yanfeng; Bahadur, Jitendra; ...

2016-10-20

Even when not functionalized intentionally, most carbon materials are not hydrophobic and readily adsorb water molecules from atmospheric water vapor. We have equilibrated an ultramicroporous carbon at several levels of relative humidity, thereby attaining various hydration levels. The water molecules were adsorbed on the pore walls (but did not fill completely the pore volume) and thus could be better described as hydration, or surface, rather than confined, water. We used quasielastic neutron scattering to perform a detailed investigation of the dependence of microscopic dynamics of these adsorbed water species on the hydration level and temperature. The behavior of hydration watermore » in ultramicroporous carbon clearly demonstrates the same universal traits that characterize surface (hydration) water in other materials that are surface-hydrated. In addition, unless special treatment is intentionally applied to ultramicroporous carbon, the species filling its pores in various applications, ranging from hydrogen molecules to electrolytes, likely find themselves in contact with non-freezing water molecules characterized by rich microscopic dynamics.« less
CO₂ processing and hydration of fruit and vegetable tissues by clathrate hydrate formation.

PubMed

Takeya, Satoshi; Nakano, Kohei; Thammawong, Manasikan; Umeda, Hiroki; Yoneyama, Akio; Takeda, Tohoru; Hyodo, Kazuyuki; Matsuo, Seiji

2016-08-15

CO2 hydrate can be used to preserve fresh fruits and vegetables, and its application could contribute to the processing of carbonated frozen food. We investigated water transformation in the frozen tissue of fresh grape samples upon CO2 treatment at 2-3 MPa and 3°C for up to 46 h. Frozen fresh bean, radish, eggplant and cucumber samples were also investigated for comparison. X-ray diffraction indicated that after undergoing CO2 treatment for several hours, structure I CO2 hydrate formed within the grape tissue. Phase-contrast X-ray imaging using the diffraction-enhanced imaging technique revealed the presence of CO2 hydrate within the intercellular spaces of these tissues. The carbonated produce became effervescent because of the dissociation of CO2 hydrate through the intercellular space, especially above the melting point of ice. In addition, suppressed metabolic activity resulting from CO2 hydrate formation, which inhibits water and nutrient transport through intercellular space, can be expected. Copyright © 2016 Elsevier Ltd. All rights reserved.
Anomalous preservation of pure methane hydrate at 1 atm

USGS Publications Warehouse

Stern, L.A.; Circone, S.; Kirby, S.H.; Durham, W.B.

2001-01-01

Direct measurement of decomposition rates of pure, polycrystalline methane hydrate reveals a thermal regime where methane hydrate metastably `preserves' in bulk by as much as 75 K above its nominal equilibrium temperature (193 K at 1 atm). Rapid release of the sample pore pressure at isothermal conditions between 242 and 271 K preserves up to 93% of the hydrate for at least 24 h, reflecting the greatly suppressed rates of dissociation that characterize this regime. Subsequent warming through the H2O ice point then induces rapid and complete dissociation, allowing controlled recovery of the total expected gas yield. This behavior is in marked contrast to that exhibited by methane hydrate at both colder (193-240 K) and warmer (272-290 K) test conditions, where dissociation rates increase monotonically with increasing temperature. Anomalous preservation has potential application for successful retrieval of natural gas hydrate or hydrate-bearing sediments from remote settings, as well as for temporary low-pressure transport and storage of natural gas.
Crystal-chemistry of alteration products of vitrified wastes: Implications on the retention of polluting elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sterpenich, Jerome

2008-07-01

Alteration products of vitrified wastes coming from the incineration of household refuse (MSW) are described. Two vitrified wastes containing 50% and 70% of fly ash and a synthetic stained-glass with a composition close to that of an ancient glass (medieval stained-glass) were altered under different pH conditions (1, 5.5 corresponding to demineralized water and 10) during 181 days. Under acidic condition, the alteration layer is made of an amorphous hydrated silica gel impoverished in most of the initial elements. A minor phase MPO{sub 4} . nH{sub 2}O, where M represents Fe, Ti, Al, Ca and K cations, also constitutes themore » altered layer of the synthetic stained-glass. Under neutral and basic conditions, the altered layer is made of an amorphous hydrated silica gel and a crystallized calcium phosphate phase. The silica gel is depleted in alkalis and alkali-earth elements but contains significant amounts of aluminium, magnesium and transition elements, whereas the calcium phosphate is a hydroxylapatite-like phase with P-Si substitutions and a Ca/P ratio depending on the pH of the solution. This study shows: (i) the strong influence of pH conditions on the crystal-chemistry of alteration products and thus on the mechanisms of weathering resulting in different trapping of polluting elements, and (ii) that glass alteration does not necessary produce thermodynamically stable phases which has to be taken into account for the prediction of the long-term behavior.« less
Effective pore size and radius of capture for K(+) ions in K-channels.

PubMed

Moldenhauer, Hans; Díaz-Franulic, Ignacio; González-Nilo, Fernando; Naranjo, David

2016-02-02

Reconciling protein functional data with crystal structure is arduous because rare conformations or crystallization artifacts occur. Here we present a tool to validate the dimensions of open pore structures of potassium-selective ion channels. We used freely available algorithms to calculate the molecular contour of the pore to determine the effective internal pore radius (r(E)) in several K-channel crystal structures. r(E) was operationally defined as the radius of the biggest sphere able to enter the pore from the cytosolic side. We obtained consistent r(E) estimates for MthK and Kv1.2/2.1 structures, with r(E) = 5.3-5.9 Å and r(E) = 4.5-5.2 Å, respectively. We compared these structural estimates with functional assessments of the internal mouth radii of capture (r(C)) for two electrophysiological counterparts, the large conductance calcium activated K-channel (r(C) = 2.2 Å) and the Shaker Kv-channel (r(C) = 0.8 Å), for MthK and Kv1.2/2.1 structures, respectively. Calculating the difference between r(E) and r(C), produced consistent size radii of 3.1-3.7 Å and 3.6-4.4 Å for hydrated K(+) ions. These hydrated K(+) estimates harmonize with others obtained with diverse experimental and theoretical methods. Thus, these findings validate MthK and the Kv1.2/2.1 structures as templates for open BK and Kv-channels, respectively.
Experimental and Numerical Observations of Hydrate Reformation during Depressurization in a Core-Scale Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seol, Yongkoo; Myshakin, Evgeniy

2011-01-01

Gas hydrate has been predicted to reform around a wellbore during depressurization-based gas production from gas hydrate-bearing reservoirs. This process has an adverse effect on gas production rates and it requires time and sometimes special measures to resume gas flow to producing wells. Due to lack of applicable field data, laboratory scale experiments remain a valuable source of information to study hydrate reformation. In this work, we report laboratory experiments and complementary numerical simulations executed to investigate the hydrate reformation phenomenon. Gas production from a pressure vessel filled with hydrate-bearing sand was induced by depressurization with and without heat fluxmore » through the boundaries. Hydrate decomposition was monitored with a medical X-ray CT scanner and pressure and temperature measurements. CT images of the hydrate-bearing sample were processed to provide 3-dimensional data of heterogeneous porosity and phase saturations suitable for numerical simulations. In the experiments, gas hydrate reformation was observed only in the case of no-heat supply from surroundings, a finding consistent with numerical simulation. By allowing gas production on either side of the core, numerical simulations showed that initial hydrate distribution patterns affect gas distribution and flow inside the sample. This is a direct consequence of the heterogeneous pore network resulting in varying hydraulic properties of the hydrate-bearing sediment.« less
[Preclinical safety evaluation of chloral hydrate after topical application using the example of psoriatic itch].

PubMed

Wohlrab, J; Gilbrich, F; Wolff, L; Fischer, M; Philipp, S

2017-03-01

Psoriasis is known today as a T‑cell-mediated autoimmunological systemic disease. The chronic inflammatory processes involve neuroimmunological factors that are held responsible not only for various aspects of psychiatric-neurological comorbidities but also for neurosensory problems, primarily itching. Amongst other things, the significance of GABA A receptors are often discussed in this context. The topical use of chloral hydrate in semisolid preparations for antipruritic therapy goes back to Neisser and is currently experiencing a revival in individually manufactured formulations. However, it is currently unknown whether the unwanted side effects that are described for systemic use of chloral hydrate are also relevant for topical application. For lack of clinical safety data, preclinical tests for cutaneous cytotoxicity and calculations for systemic bioavailability after topical application have been performed. The present data cannot fully remove safety concerns for topical application of chloral hydrate in the formulation favoured by the NRF (Neues Rezepturformularium)-the so-called 1‑2-3-cream. A twice daily use of the 1‑2-3-cream on a maximum of 10% of the body surface can be regarded as safe. For a better assessment of harmlessness, tests for cutaneous bioavailability (concentration-time profile) on human skin and clinical studies would be necessary.
Preliminary Measurements of the Attenuation Properties of Polycrystalline Water Ice and CO2 Clathrate Hydrates at the Tidal Frequencies of Europa and Enceladus

NASA Astrophysics Data System (ADS)

Choukroun, M.; Castillo, J. C.; Young, J. B.; Mielke, R.

2009-12-01

We will report measurements of the attenuation properties of polycrystalline water ice and CO2 clathrate hydrates samples obtained in the frequency range 3x10-6 to 10-2 Hz, which encompasses the tidal frequencies of Europa and Enceladus. Previous attenuation measurements obtained on a variety of planetary materials have demonstrated that the mechanisms driving attenuation in the frequency range 10-4 to 1 Hz are controlled by the same parameters controlling the creep properties of these materials: temperature, stress, microstructure (including grain size), and the presence of second-phase impurities. Thus, accurate control and characterization of the microstructure and composition of tested samples are key steps toward the development of empirical relationships describing the mechanical response of these materials. This is the reason why we have invested significant effort in the development of synthesis procedures for the production of our samples. Both water ice and clathrate hydrate samples are grown from H2O ice seeds, which are produced by grinding ice crystals pre-grown at -30°C from pure de-ionized liquid water. A high pressure - low temperature vessel, which achieves pressures up to 200 bars and temperatures within the range -50 - +50 °C, is used for the growth of clathrate hydrates. These are synthesized by reaction of ice seeds with CO2 at temperatures close to the melting point of ice in order to improve reaction kinetics. Characterization of the samples composition and microstructure is carried out via crossed-polarized cryo-microscopic observations, and via imaging with a Scanning Electron Microprobe equipped with a liquid - nitrogen cooled stage (CryoSEM). The Energy Dispersive Spectrometer capability of the SEM provides elemental composition for verification of the purity of the samples. For clathrate hydrates, Raman microspectroscopy is also used to ensure the homogeneity of sample composition. We will show that the grain size of the ice seeds is not affected by the transformation into clathrate hydrates. However, the sub-grain structure obviously undergoes significant changes, which might be reflected in the mechanical behavior. In order to remove microporosity, a compaction system has been implemented, which consists to the application of high pressures under vacuum and at very low temperatures. We will show the result of compaction experiments in terms of residual porosity and microstructure evolution. We will also present initial measurements on the attenuation properties of polycrystalline water ice and CO2 clathrate hydrates at the stress conditions and tidal frequencies approaching those of icy satellites such as Europa and Enceladus. Acknowledgements: We gratefully acknowledge C. McCarthy and H. Engelhardt for technical advise and support. MC is supported by a NASA Postdoctoral Fellowship, administered by Oak Ridge Associated Universities. This work has been conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2009, California Institute of Technology. Government sponsorship acknowledged.
Molecular structures of N-ethylpiperidine betaine hydrate and its 1:1 complex with squaric acid

NASA Astrophysics Data System (ADS)

Dega-Szafran, Z.; Dutkiewicz, G.; Kosturkiewicz, Z.; Szafran, M.

2013-12-01

N-ethylpiperidine betaine, (N-carboxymethyl-N-ethylpiperidinium inner salt, EtPB) crystallizes as a hydrate. EtPB and water molecules are bonded by intermolecular OH⋯O hydrogen bonds of 2.817(1) and 2.863(1) Å, into a centrosymmetric dimer, in which only one carboxylate oxygen atom is involved in H-bonds formation. In the complex of EtPB with squaric acid (3,4-dihydroxy-3-cyclobutene-1,2-dione, H2SQ) both carboxylate oxygen atoms are engaged in the hydrogen bonds which links molecules through two short, non-symmetric OH⋯O hydrogen bonds of 2.489(1) and 2.500(1) Å. The preferences of the conformation of the EtPB unit in the hydrogen bond formation have been studied by X-ray diffraction, FTIR and NMR spectroscopy and the results are supported by DFT calculations. EtPB, in hydrate and in the complex, has a chair conformation with the CH3CH2 group in the axial position and the CH2COO substituent in the equatorial position.
Cyclobutanone Mimics of Intermediates in Metallo-β-Lactamase Catalysis.

PubMed

Abboud, Martine I; Kosmopoulou, Magda; Krismanich, Anthony P; Johnson, Jarrod W; Hinchliffe, Philip; Brem, Jürgen; Claridge, Timothy D W; Spencer, James; Schofield, Christopher J; Dmitrienko, Gary I

2018-04-17

The most important resistance mechanism to β-lactam antibiotics involves hydrolysis by two β-lactamase categories: the nucleophilic serine and the metallo-β-lactamases (SBLs and MBLs, respectively). Cyclobutanones are hydrolytically stable β-lactam analogues with potential to inhibit both SBLs and MBLs. We describe solution and crystallographic studies on the interaction of a cyclobutanone penem analogue with the clinically important MBL SPM-1. NMR experiments using 19 F-labeled SPM-1 imply the cyclobutanone binds to SPM-1 with micromolar affinity. A crystal structure of the SPM-1:cyclobutanone complex reveals binding of the hydrated cyclobutanone through interactions with one of the zinc ions, stabilisation of the hydrate by hydrogen bonding to zinc-bound water, and hydrophobic contacts with aromatic residues. NMR analyses using a 13 C-labeled cyclobutanone support assignment of the bound species as the hydrated ketone. The results inform on how MBLs bind substrates and stabilize tetrahedral intermediates. They support further investigations on the use of transition-state and/or intermediate analogues as inhibitors of all β-lactamase classes. © 2018 Die Autoren. Veröffentlicht von Wiley-VCH Verlag GmbH & Co. KGaA.
Cyclobutanone Mimics of Intermediates in Metallo‐β‐Lactamase Catalysis

PubMed Central

Abboud, Martine I.; Kosmopoulou, Magda; Krismanich, Anthony P.; Johnson, Jarrod W.; Hinchliffe, Philip; Brem, Jürgen; Claridge, Timothy D. W.

2018-01-01

Abstract The most important resistance mechanism to β‐lactam antibiotics involves hydrolysis by two β‐lactamase categories: the nucleophilic serine and the metallo‐β‐lactamases (SBLs and MBLs, respectively). Cyclobutanones are hydrolytically stable β‐lactam analogues with potential to inhibit both SBLs and MBLs. We describe solution and crystallographic studies on the interaction of a cyclobutanone penem analogue with the clinically important MBL SPM‐1. NMR experiments using 19F‐labeled SPM‐1 imply the cyclobutanone binds to SPM‐1 with micromolar affinity. A crystal structure of the SPM‐1:cyclobutanone complex reveals binding of the hydrated cyclobutanone through interactions with one of the zinc ions, stabilisation of the hydrate by hydrogen bonding to zinc‐bound water, and hydrophobic contacts with aromatic residues. NMR analyses using a 13C‐labeled cyclobutanone support assignment of the bound species as the hydrated ketone. The results inform on how MBLs bind substrates and stabilize tetrahedral intermediates. They support further investigations on the use of transition‐state and/or intermediate analogues as inhibitors of all β‐lactamase classes. PMID:29250863
Halobetasol Propionate Lotion, 0.05% Provides Superior Hydration Compared to Halobetasol Propionate Cream, 0.05% in a Double-Blinded Study of Occlusivity and Hydration.

PubMed

Grove, Gary; Zerweck, Charles; Houser, Tim; Andrasfay, Anthony; Gauthier, Bob; Holland, Charles; Piacquadio, Daniel

2017-02-01

This study measured skin hydration and occlusivity of two test products [halobetasol propionate lotion, 0.05% (HBP Lotion) and Ultravate® (halobetasol propionate) cream, 0.05% (HBP Cream)] at 2, 4, and 6 hours after application to skin test sites previously challenged by dry shaving, which was performed to compromise the integrity of the stratum corneum barrier. Trans-epidermal water loss (TEWL), an indicator of skin barrier function, was measured using cyberDERM, inc. RG-1 evaporimeter. Skin hydration was evaluated using IBS SkiCon-200 conductance meter. Test products were applied bilaterally on dry-shaved sites on the volar forearm sites, according to a randomization scheme, with two test sites untreated to serve as "dry-shaved" controls. TEWL and conductance were measured at 2, 4, and 6 hours post-treatment. HBP Lotion displayed a significant increase in skin hydration at 2, 4, and 6 hours post-treatment compared to the baseline values and dry-shaved controls (each, P less than 0.001). However, HBP Cream produced statistically significant increased skin hydration only after 6 hours (P less than 0.05). HBP Lotion was significantly more effective than HBP Cream in increasing skin hydration at 2 and 4 hours post-treatment (each, P less than 0.001), and had a directional advantage (not statistically significant) at 6 hours. Neither test product had a significant occlusive effect as measured by TEWL at 2, 4, and 6 hours post-application. Both formulations of HBP (Lotion and Cream) contributed to skin moisturization, as measured by skin conductance. HBP Lotion produced a significantly more rapid onset and higher level of moisturization at 2 and 4 hours post-application compared to HBP Cream. The TEWL results indicate that neither HBP Lotion nor HBP Cream provided any significant occlusivity to the skin.
J Drugs Dermatol. 2017;16(2):140-144.
.
Modeling Nanomechanical Behavior of Calcium-Silicate-Hydrate

DTIC Science & Technology

2012-08-01

applicability to hardened pastes of tricalcium silicate, Portland cement, and blends of Portland cement with blast-furnace slag , metakaolin, or silica...Hydrated Nanocomposites: Concrete, Bone, and Shale. J. Am. Ceram . Soc., 90(9): 2677-2692. Wu, Jianzhong. and John M. Prausnitz. 2002. Generalizations for
Production of hydrocarbons from hydrates. [DOE patent application

DOEpatents

McGuire, P.L.

1981-09-08

An economical and safe method of producing hydrocarbons (or natural gas) from in situ hydrocarbon-containing hydrates is given. Once started, the method will be self-driven and will continue producing hydrocarbons over an extended period of time (i.e., many days).
Research Of The Influence Of Reftinskii SDPP’S Ash On The Processes Of Cement Stone’S Structure Forming

NASA Astrophysics Data System (ADS)

Zimakova, G. A.; Solonina, V. A.; Zelig, M. P.

2017-01-01

The article describes the experimental research of cement stone. Cement stone forming involves highly dispersive mineral additive - ground ash. It is stated that the substitution of some part of cement with activated ash leaves cement strength high. This is possible due to the activity of ash in structure forming processes. Activation of ash provides the increase in its puzzolanic activity, complete hydration processes. it is stated that ash grinding leads to a selective crystallization hydrated neoformations. Their morthology is different on outer and inner surfaces of ash spheres. The usage of ash can provide cement economy on condition that rheological characteristics of concrete stay constant. Besides, the usage of ash will improve physical and mechanic characteristics of cement stone and concrete.
The 24-hour skin hydration and barrier function effects of a hyaluronic 1%, glycerin 5%, and Centella asiatica stem cells extract moisturizing fluid: an intra-subject, randomized, assessor-blinded study.

PubMed

Milani, Massimo; Sparavigna, Adele

2017-01-01

Moisturizing products are commonly used to improve hydration in skin dryness conditions. However, some topical hydrating products could have negative effects on skin barrier function. In addition, hydrating effects of moisturizers are not commonly evaluated up to 24 hours after a single application. Hyaluronic acid (HA) and glycerin are very well-known substances able to improve skin hydration. Centella asiatica extract (CAE) could exert lenitive, anti-inflammatory and reepithelialization actions. Furthermore, CAE could inhibit hyaluronidase enzyme activity, therefore prolonging the effect of HA. A fluid containing HA 1%, glycerin 5% and stem cells CAE has been recently developed (Jaluronius CS [JCS] fluid). To evaluate and compare the 24-hour effects of JCS fluid on skin hydration and on transepidermal water loss (TEWL) in healthy subjects in comparison with the control site. Twenty healthy women, mean age 40 years, were enrolled in an intra-subject (right vs left), randomized, assessor-blinded, controlled, 1-day trial. The primary end points were the skin hydration and TEWL, evaluated at the volar surface of the forearm and in standardized conditions (temperature- and humidity-controlled room: 23°C and 30% of humidity) using a corneometer and a vapometer device at baseline, 1, 8 and 24 hours after JCS fluid application. Measurements were performed by an operator blinded for the treatments. Skin hydration after 24 hours was significantly higher ( P =0.001; Mann-Whitney U test) in the JCS-treated area in comparison with the control site. JCS induced a significant ( P =0.0001) increase in skin hydration at each evaluation time (+59% after 1 hour, +48% after 8 hours and +29% after 24 hours) in comparison with both baseline ( P =0.0001) and non-treated control site ( P =0.001). TEWL after 24 hours was significantly lower ( P =0.049; Mann-Whitney U test) in the JCS-treated area in comparison with the control site (13±4 arbitrary units [AU] vs 16±6 AU). JCS fluid significantly reduced post-stripping TEWL in comparison with baseline after 1, 8 and 24 hours (-52%, -32% and -48%, respectively). In the control site, TEWL was not reduced in comparison with baseline values at each time point's evaluation. A single application of JCS significantly improves skin hydration for up to 24 hours at the same time as improving skin barrier function.
Development of Biodegradable Poly(citrate)-Polyhedral Oligomeric Silsesquioxanes Hybrid Elastomers with High Mechanical Properties and Osteogenic Differentiation Activity.

PubMed

Du, Yuzhang; Yu, Meng; Chen, Xiaofeng; Ma, Peter X; Lei, Bo

2016-02-10

Biodegradable elastomeric biomaterials have attracted much attention in tissue engineering due to their biomimetic viscoelastic behavior and biocompatibility. However, the low mechanical stability at hydrated state, fast biodegradation in vivo, and poor osteogenic activity greatly limited bioelastomers applications in bone tissue regeneration. Herein, we develop a series of poly(octanediol citrate)-polyhedral oligomeric silsesquioxanes (POC-POSS) hybrids with highly tunable elastomeric behavior (hydrated state) and biodegradation and osteoblasts biocompatibility through a facile one-pot thermal polymerization strategy. POC-POSS hybrids show significantly improved stiffness and ductility in either dry or hydrated conditions, as well as good antibiodegradation ability (20-50% weight loss in 3 months). POC-POSS hybrids exhibit significantly enhanced osteogenic differentiation through upregulating alkaline phosphatase (ALP) activity, calcium deposition, and expression of osteogenic markers (ALPL, BGLAP, and Runx2). The high mechanical stability at hydrated state and enhanced osteogenic activity make POC-POSS hybrid elastomers promising as scaffolds and nanoscale vehicles for bone tissue regeneration and drug delivery. This study may also provide a new strategy (controlling the stiffness under hydrated condition) to design advanced hybrid biomaterials with high mechanical properties under physiological condition for tissue regeneration applications.

Carbohydrates as efficient catalysts for the hydration of α-amino nitriles.

PubMed

Chitale, Sampada; Derasp, Joshua S; Hussain, Bashir; Tanveer, Kashif; Beauchemin, André M

2016-11-01

Directed hydration of α-amino nitriles was achieved under mild conditions using simple carbohydrates as catalysts exploiting temporary intramolecularity. A broadly applicable procedure using both formaldehyde and NaOH as catalysts efficiently hydrated a variety of primary and secondary susbtrates, and allowed the hydration of enantiopure substrates to proceed without racemization. This work also provides a rare comparison of the catalytic activity of carbohydrates, and shows that the simple aldehydes at the basis of chemical evolution are efficient organocatalysts mimicking the function of hydratase enzymes. Optimal catalytic efficiency was observed with destabilized aldehydes, and with difficult substrates only simple carbohydrates such as formaldehyde and glycolaldehyde proved reliable.
Moisture changes in the plant cell wall force cellulose crystallites to deform.

PubMed

Zabler, S; Paris, O; Burgert, I; Fratzl, P

2010-08-01

Nano-crystallite deformation of cellulose microfibrils in the secondary cell wall layer of spruce wood tracheids was observed during de- and rehydration experiments below the fibre saturation point. A quantitative analysis of the (004), (200) and the (110)/(11 0) doublet X-ray diffraction peaks revealed longitudinal contraction, lateral expansion and changes in the monoclinic angle of the cellulose unit cell during drying of wood fibres. Experiments on unfixed samples as well as the simultaneous application of mechanical tensile and dehydration stress to samples hold at constant length showed two deformation mechanisms of different nature and magnitude. The first mechanism depends on the relative wood moisture content and the second one on the macroscopic tensile stress. These findings imply a new perspective on the role of water adsorption perceiving a hydration-induced structural change of cellulose crystal structure as a major driving force for deformation. Copyright 2010 Elsevier Inc. All rights reserved.
Effect of hydration of sugar groups on adsorption of Quillaja bark saponin at air/water and Si/water interfaces.

PubMed

Wojciechowski, Kamil; Orczyk, Marta; Marcinkowski, Kuba; Kobiela, Tomasz; Trapp, Marcus; Gutberlet, Thomas; Geue, Thomas

2014-05-01

Adsorption of a natural glycoside surfactant Quillaja bark saponin ("QBS", Sigma Aldrich 84510) was studied at the air/water and Si/water interfaces using a combination of surface pressure (SP), surface dilatational rheology, neutron reflectivity (NR), Infra-Red Attenuated Total Reflection Spectroscopy (IR ATR) and Quartz Crystal Microbalance (QCM). The adsorbed layers formed at the air/water interface are predominantly elastic, with the dilatational surface storage modulus reaching the maximum value of E'=184 mN/m. The NR results point to a strong hydration of the adsorbed layers (about 65% hydration, corresponding to about 60 molecules of water per one QBS molecule), most likely related to the presence of multiple sugar groups constituting the glycone part of the QBS molecules. With a layer thickness of 19 Å, the adsorbed amount obtained from NR seems largely underestimated in comparison to the value obtained from the surface tension isotherm. While this high extent of hydration does not prevent formation of dense and highly elastic layers at the air-water surface, QBS adsorption at the Si/water interface is much weaker. The adsorption isotherm of QBS on Si obtained from the QCM study reflects much lower affinity of highly hydrated and negatively charged saponin molecules to the Si/water interface. We postulate that at the air/water interface, QBS adsorbs through the triterpene aglycone moiety. In contrast, weak hydrogen bonding between the glycone part and the surface silanol groups of Si is responsible for QBS adsorption on more polar Si/water interface. Copyright © 2014 Elsevier B.V. All rights reserved.
Traditional Portland cement and MgO-based cement: a promising combination?

NASA Astrophysics Data System (ADS)

Tonelli, Monica; Martini, Francesca; Calucci, Lucia; Geppi, Marco; Borsacchi, Silvia; Ridi, Francesca

2017-06-01

MgO/SiO2 cements are materials potentially very useful for radioactive waste disposal, but knowledge about their physico-chemical properties is still lacking. In this paper we investigated the hydration kinetics of cementitious formulations prepared by mixing MgO/SiO2 and Portland cement in different proportions and the structural properties of the hydrated phases formed in the first month of hydration. In particular, the hydration kinetics was investigated by measuring the free water index on pastes by means of differential scanning calorimetry, while the structural characterization was carried out by combining thermal (DTA), diffractometric (XRD), and spectroscopic (FTIR, 29Si solid state NMR) techniques. It was found that calcium silicate hydrate (C-S-H) and magnesium silicate hydrate (M-S-H) gels mainly form as separate phases, their relative amount and structural characteristics depending on the composition of the hydrated mixture. Moreover, the composition of the mixtures strongly affects the kinetics of hydration and the pH of the aqueous phase in contact with the cementitious materials. The results here reported show that suitable mixtures of Portland cement and MgO/SiO2 could be used to modify the properties of hydrated phases with potential application in the storage of nuclear waste in clayey disposal.
Phase equilibria and thermodynamic modeling of ethane and propane hydrates in porous silica gels.

PubMed

Seo, Yongwon; Lee, Seungmin; Cha, Inuk; Lee, Ju Dong; Lee, Huen

2009-04-23

In the present study, we examined the active role of porous silica gels when used as natural gas storage and transportation media. We adopted the dispersed water in silica gel pores to substantially enhance active surface for contacting and encaging gas molecules. We measured the three-phase hydrate (H)-water-rich liquid (L(W))-vapor (V) equilibria of C(2)H(6) and C(3)H(8) hydrates in 6.0, 15.0, 30.0, and 100.0 nm silica gel pores to investigate the effect of geometrical constraints on gas hydrate phase equilibria. At specified temperatures, the hydrate stability region is shifted to a higher pressure region depending on pore size when compared with those of bulk hydrates. Through application of the Gibbs-Thomson relationship to the experimental data, we determined the values for the C(2)H(6) hydrate-water and C(3)H(8) hydrate-water interfacial tensions to be 39 +/- 2 and 45 +/- 1 mJ/m(2), respectively. By using these values, the calculation values were in good agreement with the experimental ones. The overall results given in this study could also be quite useful in various fields, such as exploitation of natural gas hydrate in marine sediments and sequestration of carbon dioxide into the deep ocean.
Skin hydration in postmenopausal women: argan oil benefit with oral and/or topical use.

PubMed

Boucetta, Kenza Qiraouani; Charrouf, Zoubida; Derouiche, Abdelfattah; Rahali, Younes; Bensouda, Yahya

2014-10-01

The aim of this study was to evaluate the effect of daily consumption and/or application of argan oil on skin hydration in postmenopausal women. Sixty postmenopausal women consumed butter during the stabilization period and were randomly divided into two groups for the intervention period: the treatment group absorbed alimentary argan oil (n = 30) and the control group olive oil (n = 30). Both groups applied cosmetic argan oil in the left volar forearm during a sixty days' period. Evaluation of skin hydration, i.e. transepidermal water loss (TEWL) and water content of the epidermis (WCE) on both volar forearms of the two groups, were performed during three visits at D0, D30 and after sixty days (D60) of oils treatment. The consumption of argan oil has led to a significant decrease in TEWL (p = 0.023) and a significant increase in WCE (p = 0.001). The application of argan oil has led to a significant decrease in TEWL (p = 0.01) and a significant increase in WCE (p < 0.001). Our findings suggest that the daily consumption and application of argan oil have improved the skin hydration by restoring the barrier function and maintaining the water-holding capacity.
NIST Gas Hydrate Research Database and Web Dissemination Channel.

PubMed

Kroenlein, K; Muzny, C D; Kazakov, A; Diky, V V; Chirico, R D; Frenkel, M; Sloan, E D

2010-01-01

To facilitate advances in application of technologies pertaining to gas hydrates, a freely available data resource containing experimentally derived information about those materials was developed. This work was performed by the Thermodynamic Research Center (TRC) paralleling a highly successful database of thermodynamic and transport properties of molecular pure compounds and their mixtures. Population of the gas-hydrates database required development of guided data capture (GDC) software designed to convert experimental data and metadata into a well organized electronic format, as well as a relational database schema to accommodate all types of numerical and metadata within the scope of the project. To guarantee utility for the broad gas hydrate research community, TRC worked closely with the Committee on Data for Science and Technology (CODATA) task group for Data on Natural Gas Hydrates, an international data sharing effort, in developing a gas hydrate markup language (GHML). The fruits of these efforts are disseminated through the NIST Sandard Reference Data Program [1] as the Clathrate Hydrate Physical Property Database (SRD #156). A web-based interface for this database, as well as scientific results from the Mallik 2002 Gas Hydrate Production Research Well Program [2], is deployed at http://gashydrates.nist.gov.
Obsidian Hydration Dating in the Undergraduate Curriculum.

ERIC Educational Resources Information Center

Manche, Emanuel P.; Lakatos, Stephen

1986-01-01

Provides an overview of obsidian hydration dating for the instructor by presenting: (1) principles of the method; (2) procedures; (3) applications; and (4) limitations. The theory of the method and one or more laboratory exercises can be easily introduced into the undergraduate geology curriculum. (JN)
Consequences of CO2 solubility for hydrate formation from carbon dioxide containing water and other impurities.

PubMed

Kvamme, Bjørn; Kuznetsova, Tatiana; Jensen, Bjørnar; Stensholt, Sigvat; Bauman, Jordan; Sjøblom, Sara; Nes Lervik, Kim

2014-05-14

Deciding on the upper bound of water content permissible in a stream of dense carbon dioxide under pipeline transport conditions without facing the risks of hydrate formation is a complex issue. In this work, we outline and analyze ten primary routes of hydrate formation inside a rusty pipeline, with hydrogen sulfide, methane, argon, and nitrogen as additional impurities. A comprehensive treatment of equilibrium absolute thermodynamics as applied to multiple hydrate phase transitions is provided. We also discuss in detail the implications of the Gibbs phase rule that make it necessary to consider non-equilibrium thermodynamics. The analysis of hydrate formation risk has been revised for the dominant routes, including the one traditionally considered in industrial practice and hydrate calculators. The application of absolute thermodynamics with parameters derived from atomistic simulations leads to several important conclusions regarding the impact of hydrogen sulfide. When present at studied concentrations below 5 mol%, the presence of hydrogen sulfide will only support the carbon-dioxide-dominated hydrate formation on the phase interface between liquid water and hydrate formers entering from the carbon dioxide phase. This is in contrast to a homogeneous hydrate nucleation and growth inside the aqueous solution bulk. Our case studies indicate that hydrogen sulfide at higher than 0.1 mol% concentration in carbon dioxide can lead to growth of multiple hydrate phases immediately adjacent to the adsorbed water layers. We conclude that hydrate formation via water adsorption on rusty pipeline walls will be the dominant contributor to the hydrate formation risk, with initial concentration of hydrogen sulfide being the critical factor.
Nucleation and crystallization kinetics of hydrated amorphous lactose above the glass transition temperature.

PubMed

Schmitt, E A; Law, D; Zhang, G G

1999-03-01

The crystallization kinetics of amorphous lactose in the presence and absence of seed crystals were investigated at 57.5% relative humidity. Isothermal crystallization studies were conducted gravimetrically in an automated vacuum moisture balance at several temperatures between 18 and 32 degrees C. The crystallization rate constants were then determined from Johnson-Mehl-Avrami (JMA) treatment and isothermal activation energies were obtained from Arrhenius plots. Based on microscopic observations, a reaction order of 3 was used for JMA analysis. The nonisothermal activation energies were determined by differential scanning calorimetry using Kissinger's analysis. Isothermal activation energies for amorphous lactose with and without seed crystals were 89.5 (+/-5.6) kJ/mol and 186.5 (+/-17.6) kJ/mol, respectively. Nonisothermal activation energies with and without seed crystals were 71 (+/-7.5) kJ/mol and 80.9 (+/-8.9) kJ/mol, respectively. The similarity of the isothermal and nonisothermal activation energies for the sample with seeds suggested that crystallization was occurring by growth from a fixed number of preexisting nuclei. Markedly different isothermal and nonisothermal activation energies in the absence of seeds suggested a site-saturated nucleation mechanism, and therefore allowed calculation of an activation energy for nucleation of 317 kJ/mol.
The Structure of Glycine Dihydrate: Implications for the Crystallization of Glycine from Solution and Its Structure in Outer Space.

PubMed

Xu, Wenqian; Zhu, Qiang; Hu, Chunhua Tony

2017-02-13

Glycine, the simplest amino acid, is also the most polymorphous. Herein, we report the structure determination of a long unknown phase of glycine, which was first reported by Pyne and Suryanarayanan in 2001. To date, this phase has only been prepared at 208 K as nanocrystals within ice. Through computational crystal-structure prediction and powder X-ray diffraction methods, we identified this elusive phase as glycine dihydrate (GDH), representing the first report on the structure of a hydrated glycine structure. The structure of GDH has important implications for the state of glycine in aqueous solution and the mechanisms of glycine crystallization. GDH may also be the form of glycine that comes to Earth from extraterrestrial sources. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Ion-Specific Interfacial Crystallization of Polymer-Grafted Nanoparticles

DOE PAGES

Zhang, Honghu; Wang, Wenjie; Mallapragada, Surya; ...

2017-06-27

In this study, ion-specific effects on the assembly and crystallization of polyethylene-glycol-grafted Au nanoparticles (PEG-AuNPs) at the vapor–liquid interface are examined by surface sensitive synchrotron X-ray scattering methods. We show that monovalent salts, such as KCl and NaCl, that do not advance phase separation of pure PEG at room temperature induce two-dimensional (2D) self-assembly and crystallization of PEG-AuNPs with some distinctions. Whereas for KCl the 2D hexagonal coherence length of the PEG-AuNP superlattices is remarkably large compared to other salts (over micron-sized crystalline grains), NaCl induces coexistence of two hexagonal structures. Using various salts, we find that the value ofmore » the lattice constant is correlated to the ionic hydration entropy consistent with the Hofmeister series.« less
A comparison of leaf crystal macropatterns in the two sister genera Piper and Peperomia (Piperaceae).

PubMed

Horner, Harry T; Wanke, Stefan; Samain, Marie-Stéphanie

2012-06-01

This is the first large-scale study comparing leaf crystal macropatterns of the species-rich sister genera Piper and Peperomia. It focuses on identifying types of calcium oxalate crystals and their macropatterns in leaves of both genera. The Piper results are placed in a phylogenetic context to show evolutionary patterns. This information will expand knowledge about crystals and provide specific examples to help study their form and function. One example is the first-time observation of Piper crystal sand tumbling in chlorenchyma vacuoles. Herbarium and fresh leaves were cleared of cytoplasmic content and examined with polarizing microscopy to identify types of crystals and their macropatterns. Selected hydrated herbarium and fresh leaf punches were processed for scanning electron microscopy and x-ray elemental analysis. Vibratome sections of living Piper and Peperomia leaves were observed for anatomical features and crystal movement. Both genera have different leaf anatomies. Piper displays four crystal types in chlorenchyma-crystal sand, raphides, styloids, and druses, whereas Peperomia displays three types-druses, raphides, and prisms. Because of different leaf anatomies and crystal types between the genera, macropatterns are completely different. Crystal macropattern evolution in both is characterized by increasing complexity, and both may use their crystals for light gathering and reflection for efficient photosynthesis under low-intensity light environments. Both genera have different leaf anatomies, types of crystals and crystal macropatterns. Based on Piper crystals associated with photosynthetic tissues and low-intensity light, further study of their function and association with surrounding chloroplasts is warranted, especially active crystal movement.
Comparative atomic-scale hydration of the ceramide and phosphocholine headgroup in solution and bilayer environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gillams, Richard J.; McLain, Sylvia E., E-mail: sylvia.mclain@bioch.ox.ac.uk; Lorenz, Christian D., E-mail: chris.lorenz@kcl.ac.uk

2016-06-14

Previous studies have used neutron diffraction to elucidate the hydration of the ceramide and the phosphatidylcholine headgroup in solution. These solution studies provide bond-length resolution information on the system, but are limited to liquid samples. The work presented here investigates how the hydration of ceramide and phosphatidylcholine headgroups in a solution compares with that found in a lipid bilayer. This work shows that the hydration patterns seen in the solution samples provide valuable insight into the preferential location of hydrating water molecules in the bilayer. There are certain subtle differences in the distribution, which result from a combination of themore » lipid conformation and the lipid-lipid interactions within the bilayer environment. The lipid-lipid interactions in the bilayer will be dependent on the composition of the bilayer, whereas the restricted exploration of conformational space is likely to be applicable in all membrane environments. The generalized description of hydration gathered from the neutron diffraction studies thus provides good initial estimation for the hydration pattern, but this can be further refined for specific systems.« less
Effect of lead ion concentration on the structural and optical properties of nano-crystalline PbS thin films

NASA Astrophysics Data System (ADS)

Zaman, S.; Mehmood, S. K.; Mansoor, M.; Asim, M. M.

2014-06-01

PbS thin films have received considerable attention because of their potential applications in opto-electronics applications. Spontaneous reaction of lead acetate and thiourea in aqueous hydrazine hydrate has been used for depositing PbS thin films on glass substrates. Structural and optical properties of PbS thin films are greatly influenced by the morality of the reactants and crystal defects in the lattice. Our work focuses on the variation in lead ion concentration and its effect on the structural and optical properties of PbS thin films. The deposited films were analyzed using XRD, SEM, spectrophotometer and dark resistance measurement. XRD patterns indicated the formation of major phase of nano crystalline PbS with minor presence of lead oxide phase. We also noticed that peak intensity ratio of I111/I200 varied by changing the Pb ion concentration. The film thickness and dark resistance increased whereas optical band gap decreased with the decreasing Pb ion concentration. SEM scans showed that the grain size is less than 100 nm and is not affected by varying Pb ion concentration.
Effects of the Hydration State on the Mid-Infrared Spectra of Urea and Creatinine in Relation to Urine Analyses

PubMed Central

Oliver, Katherine V.; Maréchal, Amandine

2016-01-01

When analyzing solutes by Fourier transform infrared (FT-IR) spectroscopy in attenuated total reflection (ATR) mode, drying of samples onto the ATR crystal surface can greatly increase solute band intensities and, therefore, aid detection of minor components. However, analysis of such spectra is complicated by the existence of alternative partial hydration states of some substances that can significantly alter their infrared signatures. This is illustrated here with urea, which is a dominant component of urine. The effects of hydration state on its infrared spectrum were investigated both by incubation in atmospheres of fixed relative humidities and by recording serial spectra during the drying process. Significant changes of absorption band positions and shapes were observed. Decomposition of the CN antisymmetric stretching (νas) band in all states was possible with four components whose relative intensities varied with hydration state. These correspond to the solution (1468 cm–1) and dry (1464 cm–1) states and two intermediate (1454 cm–1 and 1443 cm–1) forms that arise from specific urea–water and/or urea–urea interactions. Such intermediate forms of other compounds can also be formed, as demonstrated here with creatinine. Recognition of these states and their accommodation in analyses of materials such as dried urine allows more precise decomposition of spectra so that weaker bands of diagnostic interest can be more accurately defined. PMID:27170705
Molecular insight into the nanoconfined calcite–solution interface

PubMed Central

Diao, Yijue; Espinosa-Marzal, Rosa M.

2016-01-01

Little is known about the influence of nanoconfinement on calcium carbonate mineralization. Here, colloidal probe atomic force microscopy is used to confine the calcite–solution interface with a silica microsphere and to measure Derjaguin–Landau–Verwey–Overbeek (DLVO) and non-DLVO forces as a function of the calcium concentration, also after charge reversal of both surfaces occurs. Through the statistical analysis of the oscillatory component of a strong hydration force, the subnanometer interfacial structure of the confined atomically flat calcite is resolved in aqueous solution. By applying a mechanical work, both water and hydrated counterions are squeezed out from the nanoconfined solution, leaving the calcite surface more negatively charged than the analogous unconfined surfaces. Layer size and applied work allow a distinction between the hydration states of the counterions in the Stern layer; we propose counterions to be inner- and outer-sphere calcium ions, with a population of inner-sphere calcium ions larger than on unconfined calcite surfaces. It is also shown that the composition of the nanoconfined solution can be tuned by varying calcium concentration. This is a fundamental study of DLVO and hydration forces, and of their connection, on atomically flat calcite. More broadly, our work scrutinizes the greatly unexplored relation between surface science and confined mineralization, with implications for diverse areas of inquiry, such as nanoconfined biomineralization, CO2 sequestration in porous aquifers, and pressure solution and crystallization in confined hydrosystems. PMID:27790988
Canola Oil Fuel Cell Demonstration: Volume 3 - Technical, Commercialization, and Application Issues Associated with Harvested Biomass

DTIC Science & Technology

2006-08-17

Hydratable and non-hydratable phosphatides are removed from the oil using a degumming solution (0.1 percent of 0.85 wt percent phosphoric acid aqueous...solution or 2500 ppm citric acid may be used) followed by the addition of soft water equal to 75 percent of the phosphatide content in the crude oil...converted to water-soluble phosphatidic acid through the addition of phosphoric acid , and hydratable phosphatides are formed from the addition of soft
In Vivo skin hydration and anti-erythema effects of Aloe vera, Aloe ferox and Aloe marlothii gel materials after single and multiple applications.

PubMed

Fox, Lizelle T; du Plessis, Jeanetta; Gerber, Minja; van Zyl, Sterna; Boneschans, Banie; Hamman, Josias H

2014-04-01

To investigate the skin hydrating and anti-erythema activity of gel materials from Aloe marlothii A. Berger and A. ferox Mill. in comparison to that of Aloe barbadensis Miller (Aloe vera) in healthy human volunteers. Aqueous solutions of the polisaccharidic fractions of the selected aloe leaf gel materials were applied to the volar forearm skin of female subjects. The hydration effect of the aloe gel materials were measured with a Corneometer(®) CM 825, Visioscan(®) VC 98 and Cutometer(®) dual MPA 580 after single and multiple applications. The Mexameter(®) MX 18 was used to determine the anti-erythema effects of the aloe material solutions on irritated skin areas. The A. vera and A. marlothii gel materials hydrated the skin after a single application, whereas the A. ferox gel material showed dehydration effects compared to the placebo. After multiple applications all the aloe materials exhibited dehydration effects on the skin. Mexameter(®) readings showed that A. vera and A. ferox have anti-erythema activity similar to that of the positive control group (i.e. hydrocortisone gel) after 6 days of treatment. The polysaccharide component of the gel materials from selected aloe species has a dehydrating effect on the skin after multiple applications. Both A. vera and A. ferox gel materials showed potential to reduce erythema on the skin similar to that of hydrocortisone gel.
In Vivo skin hydration and anti-erythema effects of Aloe vera, Aloe ferox and Aloe marlothii gel materials after single and multiple applications

PubMed Central

Fox, Lizelle T.; du Plessis, Jeanetta; Gerber, Minja; van Zyl, Sterna; Boneschans, Banie; Hamman, Josias H.

2014-01-01

Objective: To investigate the skin hydrating and anti-erythema activity of gel materials from Aloe marlothii A. Berger and A. ferox Mill. in comparison to that of Aloe barbadensis Miller (Aloe vera) in healthy human volunteers. Materials and Methods: Aqueous solutions of the polisaccharidic fractions of the selected aloe leaf gel materials were applied to the volar forearm skin of female subjects. The hydration effect of the aloe gel materials were measured with a Corneometer® CM 825, Visioscan® VC 98 and Cutometer® dual MPA 580 after single and multiple applications. The Mexameter® MX 18 was used to determine the anti-erythema effects of the aloe material solutions on irritated skin areas. Results: The A. vera and A. marlothii gel materials hydrated the skin after a single application, whereas the A. ferox gel material showed dehydration effects compared to the placebo. After multiple applications all the aloe materials exhibited dehydration effects on the skin. Mexameter® readings showed that A. vera and A. ferox have anti-erythema activity similar to that of the positive control group (i.e. hydrocortisone gel) after 6 days of treatment. Conclusion: The polysaccharide component of the gel materials from selected aloe species has a dehydrating effect on the skin after multiple applications. Both A. vera and A. ferox gel materials showed potential to reduce erythema on the skin similar to that of hydrocortisone gel. PMID:24991119

Effects of Attenuation of Gas Hydrate-bearing Sediments on Seismic Data: Example from Mallik, Northwest Territories, Canada

NASA Astrophysics Data System (ADS)

Bellefleur, G.; Riedel, M.; Brent, T.

2007-05-01

Wave attenuation is an important physical property of hydrate-bearing sediments that is rarely taken into account in site characterization with seismic data. We present a field example showing improved images of hydrate- bearing sediments on seismic data after compensation of attenuation effects. Compressional quality factors (Q) are estimated from zero-offset Vertical Seismic Profiling data acquired at Mallik, Northwest Territories, Canada. During the last 10 years, two internationally-partnered research drilling programs have intersected three major intervals of sub-permafrost gas hydrates at Mallik, and have successfully extracted core samples containing significant amount of gas hydrates. Individual gas hydrate intervals are up to 40m in thickness and are characterized by high in situ gas hydrate saturation, sometimes exceeding 80% of pore volume of unconsolidated clastic sediments having average porosities ranging from 25% to 40%. The Q-factors obtained from the VSP data demonstrate significant wave attenuation for permafrost and hydrate- bearing sediments. These results are in agreement with previous attenuation estimates from sonic logs and crosshole data at different frequency intervals. The Q-factors obtained from VSP data were used to compensate attenuation effects on surface 3D seismic data acquired over the Mallik gas hydrate research wells. Intervals of gas hydrate on surface seismic data are characterized by strong reflectivity and effects from attenuation are not perceptible from a simple visual inspection of the data. However, the application of an inverse Q-filter increases the resolution of the data and improves correlation with log data, particularly for the shallowest gas hydrate interval. Compensation of the attenuation effects of the permafrost likely explains most of the improvements for the shallow gas hydrate zone. Our results show that characterization of the Mallik gas hydrates with seismic data not corrected for attenuation would tend to overestimate thicknesses and lateral extent of hydrate-bearing strata and hence, the volume of hydrates in place.
The effect of topical anti blister products on the risk of friction blister formation on the foot.

PubMed

Hashmi, Farina; Kirkham, Suzanne; Nester, Christopher; Lam, Sharon

2016-08-01

Foot blisters are a common injury, which can impact on activity and lead to infection. Increased skin surface hydration has been identified as a risk factor for blister formation, indicating that a reduction in hydration could reduce the risk of blister. Thirty healthy adults were randomised into 3 groups, each receiving a preventative foot blister treatment (2Toms(®) Blister Shield(®); Flexitol(®) Blistop and Boots Anti-Perspirant Foot Spray). Cycles of compression and shear loads where applied to heel skin using a mechanism driven by compressed air. Temperature changes were measured during load application using a thermal imaging camera (FLIR Systems Inc. and Therm CAM™ Quick Report). Near surface hydration of the skin was measured using a Corneometer(®) (C & K, Germany). There was no significant difference in the rate of temperature change of the skin between the three groups compared to not using products (p = 0.767, p = 0.767, p = 0.515) or when comparing each product (p = 0.551). There was a significant decrease in near surface skin hydration, compared to baseline, after the application of powder (-8.53 AU, p = 0.01). There was no significant difference in hydration after the application of film former and antiperspirant (-1.47 AU, p = 0.26; -1.00 AU, p = 0.80, respectively). With the application of external load we found no significant difference in the effect of the three products on temperature change. The powder product demonstrated an effect on reducing the risk of blister. It is postulated that powder may have a barrier effect. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.
Cortlandtitic enclaves associated with calc-alkaline granites from Tapia-Asturias (Hercynian Belt, northwestern Spain)

NASA Astrophysics Data System (ADS)

Galán, G.; Suárez, O.

1989-10-01

Petrographic and mineralogical characteristics of amphibole-olivine- and pyroxene-bearing ultramafic rocks from Asturias (NW Spain) are dealt with in this paper. These rocks are of cortlandtitic type and occur as small rare enclaves in basic rocks related to Hercynian calc-alkaline, post-tectonic epizonal granites, in the northwest of the Iberian Peninsula. These particular ultramafic enclaves are characterized by poikilitic cumulate microtexture. Olivine (Fo 77-81), spinel, from chromite to pleonaste composition, enstatite, subordinated diopside and sulphides are included in large brown calcic amphibole crystals displaying an irregular zonation. Phlogopite and plagioclase are also found, in a much lower proportion, between the large amphibole crystals. Mineral assemblage and chemical composition of minerals indicate formation conditions of 1150°C, 7-8 kbar of Ptotal and PH 2O < Ptotal. These rocks could represent the earlier products of fractional crystallization from a hydrated high-alumina basalt involved in the genesis of the calc-alkaline granites. This basic magma would start crystallizing at a relatively deep level, carrying up the first products of its crystallization during its ascent.
Influence of triethanolamine on the hydration product of portlandite in cement paste and the mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan-Rong, Zhang; School of Civil Engineering, Beijing Key Laboratory of Track Engineering, Beijing Jiaotong University, Beijing 100044; Xiang-Ming, Kong

The influences of triethanolamine (TEA) on the portlandite in hardened cement pastes (HCPs) were systematically investigated. Results show that the addition of TEA in cement pastes leads to a visible reduction of Ca(OH){sub 2} (CH) content and considerably alters the morphology of CH crystals from large and parallel-stacked lamellar shape to smaller and distorted actinomorphic one. For the first time, the CH micro-crystals and even non-crystalline CH in HCPs were observed in the presence of TEA. Due to integration of CH micro-crystals in C–S–H phase, remarkable higher Ca/Si ratio of C–S–H phase was found. The formation of TEA-Ca{sup 2+} complexmore » via the interaction between Ca{sup 2+} and the oxygen atoms in TEA molecule was evidenced by the results of NMR and UV. It is believed that TEA can be introduced into the crystallization process of portlandite and thus significantly alters the morphology of CH crystals and even the content of the crystalline CH phase.« less
Effect of pH on the morphology of kidney stones

NASA Astrophysics Data System (ADS)

Agarwal, Neelesh; Sova, Stacey; Singh, N. B.; Arnold, Brad; Choa, Fow-Sen; Cullum, Brian; Su, Ching-Hua

2016-05-01

The process for the formation of kidney stone is very complex phenomena and has some similarity to the crystal growth from a solution. It is very much dependent on the acidity pH of the fluids. This pH variation affects the content and amount of filtering residue and its morphology. In this study we have performed experiments using carbonate, oxides and urea to simulate and understand the morphologies of the residue filtered and coarsened in different conditions. We observed that different of morphologies of kidney stones can be explained on the basis of acidity and hydration conditions. At lower pH fat prism crystals are observed and as pH increases, long fat needle crystals with large aspect ratio are observed. The coarsening experiments showed further growth of crystals. The remelting experiments showed that during dissolution of kidney stones the joining material breaks first leaving the large faceted crystals undissolved when attempts are made to dissolve into small crystallites. However, the morphology did not change. It was also observed that impurities such as magnesium oxide (MgO) affect the morphology significantly.
Preparation, structural characterization, and decomposition studies of two new γ-octamolybdates of 4-methylpyridine.

PubMed

Szymańska, Anna; Nitek, Wojciech; Rutkowska-Zbik, Dorota; Łasocha, Wiesław

We synthesized two new γ-octamolybdates, and determined their crystal structures from single-crystal X-ray diffraction data. Orange-yellow tetrakis(4-methylpyridinium) bis(4-methylpyridine)-γ-octamolybdate 1 crystallizes in space group P2 1 /c with a = 11.586(2) Å, b = 15.526(2) Å, c = 16.247(2) Å, β = 118.753(1)º, Z = 2. White tetrakis(4-methylpyridinium) bis(4-methylpyridine)-γ-octamolybdate hydrate 2 crystallizes in space group C2/c with a = 27.086(4) Å, b = 11.917(2) Å, c = 19.332(2) Å, β = 124.427(1)º, Z = 4. Results of crystal structure determinations are presented and discussed in this paper. Thermal stability and decomposition studies of the obtained two new γ-octamolybdates were performed using TG/DSC and XRPD methods. Both compounds decomposed with the formation of 4-methylpyridinium β-octamolybdate. The two compounds are pseudo-polymorphs, exhibiting both striking similarities as well as significant differences in their structures and properties.
Solubility behavior of lamivudine crystal forms in recrystallization solvents.

PubMed

Jozwiakowski, M J; Nguyen, N A; Sisco, J M; Spancake, C W

1996-02-01

Lamivudine can be obtained as acicular crystals (form I, 0.2 hydrate) from water or methanol and as bipyramidal crystals (form II, nonsolvated) from many nonaqueous solvents. Form II is thermodynamically favored in the solid state (higher melting point and greater density than form I) at ambient relative humidities. Solubility measurements on both forms versus solvent and temperature was used to determine whether entropy or enthalpy was the driving force for solubility. Solution calorimetry data indicated that form I is favored (less soluble) in all solvents studied on the basis of enthalpy alone. In higher alcohols and other organic solvents, form I has a larger entropy of solution than form II, which compensates for the enthalpic factors and results in physical stability for form II in these systems. The metastable crystal form solubility at 25 degrees C was estimated to be 1.2-2.3 times as high as the equilibrium solubility of the stable form, depending on the temperature, solvent, and crystal form. Binary solvent studies showed that > 18-20% water must be present in ethanol to convert the excess solid to form I at equilibrium.
Clathrate structure-type recognition: Application to hydrate nucleation and crystallisation

NASA Astrophysics Data System (ADS)

Lauricella, Marco; Meloni, Simone; Liang, Shuai; English, Niall J.; Kusalik, Peter G.; Ciccotti, Giovanni

2015-06-01

For clathrate-hydrate polymorphic structure-type (sI versus sII), geometric recognition criteria have been developed and validated. These are applied to the study of the rich interplay and development of both sI and sII motifs in a variety of hydrate-nucleation events for methane and H2S hydrate studied by direct and enhanced-sampling molecular dynamics (MD) simulations. In the case of nucleation of methane hydrate from enhanced-sampling simulation, we notice that already at the transition state, ˜80% of the enclathrated CH4 molecules are contained in a well-structured (sII) clathrate-like crystallite. For direct MD simulation of nucleation of H2S hydrate, some sI/sII polymorphic diversity was encountered, and it was found that a realistic dissipation of the nucleation energy (in view of non-equilibrium relaxation to either microcanonical (NVE) or isothermal-isobaric (NPT) distributions) is important to determine the relative propensity to form sI versus sII motifs.
High-pressure protein crystallography of hen egg-white lysozyme

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamada, Hiroyuki; Nagae, Takayuki; Watanabe, Nobuhisa, E-mail: nobuhisa@nagoya-u.jp

The crystal structure of hen egg-white lysozyme (HEWL) was analyzed under pressures of up to 950 MPa. The high pressure modified the conformation of the molecule and induced a novel phase transition in the tetragonal crystal of HEWL. Crystal structures of hen egg-white lysozyme (HEWL) determined under pressures ranging from ambient pressure to 950 MPa are presented. From 0.1 to 710 MPa, the molecular and internal cavity volumes are monotonically compressed. However, from 710 to 890 MPa the internal cavity volume remains almost constant. Moreover, as the pressure increases to 950 MPa, the tetragonal crystal of HEWL undergoes a phasemore » transition from P4{sub 3}2{sub 1}2 to P4{sub 3}. Under high pressure, the crystal structure of the enzyme undergoes several local and global changes accompanied by changes in hydration structure. For example, water molecules penetrate into an internal cavity neighbouring the active site and induce an alternate conformation of one of the catalytic residues, Glu35. These phenomena have not been detected by conventional X-ray crystal structure analysis and might play an important role in the catalytic activity of HEWL.« less
Effective pore size and radius of capture for K+ ions in K-channels

PubMed Central

Moldenhauer, Hans; Díaz-Franulic, Ignacio; González-Nilo, Fernando; Naranjo, David

2016-01-01

Reconciling protein functional data with crystal structure is arduous because rare conformations or crystallization artifacts occur. Here we present a tool to validate the dimensions of open pore structures of potassium-selective ion channels. We used freely available algorithms to calculate the molecular contour of the pore to determine the effective internal pore radius (rE) in several K-channel crystal structures. rE was operationally defined as the radius of the biggest sphere able to enter the pore from the cytosolic side. We obtained consistent rE estimates for MthK and Kv1.2/2.1 structures, with rE = 5.3–5.9 Å and rE = 4.5–5.2 Å, respectively. We compared these structural estimates with functional assessments of the internal mouth radii of capture (rC) for two electrophysiological counterparts, the large conductance calcium activated K-channel (rC = 2.2 Å) and the Shaker Kv-channel (rC = 0.8 Å), for MthK and Kv1.2/2.1 structures, respectively. Calculating the difference between rE and rC, produced consistent size radii of 3.1–3.7 Å and 3.6–4.4 Å for hydrated K+ ions. These hydrated K+ estimates harmonize with others obtained with diverse experimental and theoretical methods. Thus, these findings validate MthK and the Kv1.2/2.1 structures as templates for open BK and Kv-channels, respectively. PMID:26831782
Structural characterization of two tetrachloridozincate salts of 4-carboxy-1H-imidazol-3-ium: a salt hydrate and a co-crystal salt hydrate

PubMed Central

Martens, Sean J.

2017-01-01

Imidazole-containing compounds exhibit a myriad of pharmacological activities. Two tetrachloridozincate salts of 4-carboxy-1H-imidazol-3-ium, ImHCO2H+, are reported. Bis(4-carboxy-1H-imidazol-3-ium) tetrachloridozincate monohydrate, (C4H5N2O2)2[ZnCl4]·H2O, (I), crystallizes as a monohydrate salt, while bis(4-carboxy-1H-imidazol-3-ium) tetrachloridozincate bis(1H-imidazol-3-ium-4-carboxylato) monohydrate, (C4H5N2O2)2[ZnCl4]·2C4H4N2O2·H2O, (II), is a co-crystal salt with six residues: two ImHCO2H+ cations, two formula units of the zwitterionic 1H-imidazol-3-ium-4-carboxylate, ImHCO2, one tetrachloridozincate anion and one water molecule disordered over two sites in a 0.60 (4):0.40 (4) ratio. The geometric parameters of the ImHCO2H+ and the ImHCO2 moieties are the same within the standard uncertainties of the measurements. Both compounds exhibit extensive hydrogen bonding, including involvement of the tetrachloridozincate anion, resulting in interconnected chains of anions joined by water molecules. PMID:28217334
DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Brian B.; Kirkegaard, Marie C.; Miskowiec, Andrew J.

Uranyl fluoride (UO 2F 2) is a hygroscopic powder with two main structural phases: an anhydrous crystal and a partially hydrated crystal of the same R¯3m symmetry. The formally closed-shell electron structure of anhydrous UO 2F 2 is amenable to density functional theory calculations. We use density functional perturbation theory (DFPT) to calculate the vibrational frequencies of the anhydrous crystal structure and employ complementary inelastic neutron scattering and temperature-dependent Raman scattering to validate those frequencies. As a model closed-shell actinide, we investigated the effect of LDA, GGA, and non-local vdW functionals as well as the spherically-averaged Hubbard +U correction onmore » vibrational frequencies, electronic structure, and geometry of anhydrous UO 2F 2. A particular choice of U eff = 5.5 eV yields the correct U Oyl bond distance and vibrational frequencies for the characteristic Eg and A1g modes that are within the resolution of experiment. Inelastic neutron scattering and Raman scattering suggest a degree of water coupling to the lattice vibrations in the more experimentally accessible partially hydrated UO 2F 2 system, with the symmetric O-U-O stretching vibration shifted approximately 47 cm -1 lower in energy compared to the anhydrous structure. Evidence of water interaction with the uranyl ion is present from a two-peak decomposition of the uranyl stretching vibration in the Raman spectra and anion hydrogen stretching vibrations in the inelastic neutron scattering spectra. A first-order dehydration phase transition temperature is definitively identified to be 125 °C using temperature-dependent Raman scattering.« less
Reflective terahertz (THz) imaging: system calibration using hydration phantoms

NASA Astrophysics Data System (ADS)

Bajwa, Neha; Garritano, James; Lee, Yoon Kyung; Tewari, Priyamvada; Sung, Shijun; Maccabi, Ashkan; Nowroozi, Bryan; Babakhanian, Meghedi; Sanghvi, Sajan; Singh, Rahul; Grundfest, Warren; Taylor, Zachary

2013-02-01

Terahertz (THz) hydration sensing continues to gain traction in the medical imaging community due to its unparalleled sensitivity to tissue water content. Rapid and accurate detection of fluid shifts following induction of thermal skin burns as well as remote corneal hydration sensing have been previously demonstrated in vivo using reflective, pulsed THz imaging. The hydration contrast sensing capabilities of this technology were recently confirmed in a parallel 7 Tesla Magnetic Resonance (MR) imaging study, in which burn areas are associated with increases in local mobile water content. Successful clinical translation of THz sensing, however, still requires quantitative assessments of system performance measurements, specifically hydration concentration sensitivity, with tissue substitutes. This research aims to calibrate the sensitivity of a novel, reflective THz system to tissue water content through the use of hydration phantoms for quantitative comparisons of THz hydration imagery.Gelatin phantoms were identified as an appropriate tissue-mimicking model for reflective THz applications, and gel composition, comprising mixtures of water and protein, was varied between 83% to 95% hydration, a physiologically relevant range. A comparison of four series of gelatin phantom studies demonstrated a positive linear relationship between THz reflectivity and water concentration, with statistically significant hydration sensitivities (p < .01) ranging between 0.0209 - 0.038% (reflectivity: %hydration). The THz-phantom interaction is simulated with a three-layer model using the Transfer Matrix Method with agreement in hydration trends. Having demonstrated the ability to accurately and noninvasively measure water content in tissue equivalent targets with high sensitivity, reflective THz imaging is explored as a potential tool for early detection and intervention of corneal pathologies.
Origins of saccharide-dependent hydration at aluminate, silicate, and aluminosilicate surfaces.

PubMed

Smith, Benjamin J; Rawal, Aditya; Funkhouser, Gary P; Roberts, Lawrence R; Gupta, Vijay; Israelachvili, Jacob N; Chmelka, Bradley F

2011-05-31

Sugar molecules adsorbed at hydrated inorganic oxide surfaces occur ubiquitously in nature and in technologically important materials and processes, including marine biomineralization, cement hydration, corrosion inhibition, bioadhesion, and bone resorption. Among these examples, surprisingly diverse hydration behaviors are observed for oxides in the presence of saccharides with closely related compositions and structures. Glucose, sucrose, and maltodextrin, for example, exhibit significant differences in their adsorption selectivities and alkaline reaction properties on hydrating aluminate, silicate, and aluminosilicate surfaces that are shown to be due to the molecular architectures of the saccharides. Solid-state (1)H, (13)C, (29)Si, and (27)Al nuclear magnetic resonance (NMR) spectroscopy measurements, including at very high magnetic fields (19 T), distinguish and quantify the different molecular species, their chemical transformations, and their site-specific adsorption on different aluminate and silicate moieties. Two-dimensional NMR results establish nonselective adsorption of glucose degradation products containing carboxylic acids on both hydrated silicates and aluminates. In contrast, sucrose adsorbs intact at hydrated silicate sites and selectively at anhydrous, but not hydrated, aluminate moieties. Quantitative surface force measurements establish that sucrose adsorbs strongly as multilayers on hydrated aluminosilicate surfaces. The molecular structures and physicochemical properties of the saccharides and their degradation species correlate well with their adsorption behaviors. The results explain the dramatically different effects that small amounts of different types of sugars have on the rates at which aluminate, silicate, and aluminosilicate species hydrate, with important implications for diverse materials and applications.
Crystal structure of N,N,N′,N′,N′′,N′′-hexamethylguanidinium cyanate 1.5-hydrate

PubMed Central

Tiritiris, Ioannis; Kantlehner, Willi

2015-01-01

The title hydrated salt, C7H18N3 +·OCN−.1.5H2O, was synthesized starting from N,N,N′,N′,N′′,N′′-hexamethylguanidinium chloride by a twofold anion-exchange reaction. The asymmetric unit contains two cations, two cyanate anions and three water molecules. One cation shows orientational disorder and two sets of N-atom positions were found related by a 60° rotation, with an occupancy ratio of 0.852 (6):0.148 (6). The C—N bond lengths in both guanidinium ions range from 1.329 (2) to 1.358 (10) Å, indicating double-bond character, pointing towards charge delocalization within the NCN planes. Strong O—H⋯N hydrogen bonds between the crystal water molecules and the cyanate ions and strong O—H⋯O hydrogen bonds between the water molecules are present, resulting in a two-dimensional hydrogen bonded network running parallel to the (001) plane. The hexamethylguanidinium ions are packed in between the layers built up by water molecules and cyanate ions. PMID:26870506
Synthesis, crystal structure, spectroscopic characterization, Hirshfeld surface analysis, and DFT calculations of 1,4-dimethyl-2-oxo-pyrimido[1,2-a]benzimidazole hydrate

NASA Astrophysics Data System (ADS)

El Bakri, Youness; Anouar, El Hassane; Ramli, Youssef; Essassi, El Mokhtar; Mague, Joel T.

2018-01-01

Imidazopyrimidine derivatives are organic synthesized compounds with a pyrimido[1,2-a]benzimidazole as basic skeleton. They are known for their various biological properties and as an important class of compounds in medicinal chemistry. A new 1,4-dimethyl-2-oxo-pyrimido[1,2-a]benzimidazole hydrate derivative of the tilted group has been synthesized and characterized by spectroscopic techniques NMR and FT-IR; and by a single crystal X-ray diffraction. The X-ray results showed that the tricyclic core of the title compound, C12H11N3O·H2O, is almost planar. The molecules stack along the a-axis direction in head-to- tail fashion through π-stacking interactions involving all three rings. The stacks are tied together by direct Csbnd H⋯O hydrogen bonds and by Osbnd H⋯O, Osbnd N⋯N and Csbnd H⋯O hydrogen bonds with the lattice water. DFT calculations at B3LYP/6-311++G(d,p) in gas phase an polarizable continuum model have been carried out to predict the spectral and geometrical data of the tilted compound. The obtained results showed relatively good correlations between the predicted and experimental data with correlation coefficients higher than 98%.
Physical chemistry of the H2SO4/HNO3/H2O system - Implications for polar stratospheric clouds

NASA Technical Reports Server (NTRS)

Molina, M. J.; Zhang, R.; Wooldridge, P. J.; Mcmahon, J. R.; Kim, J. E.; Chang, H. Y.; Beyer, K. D.

1993-01-01

Polar stratospheric clouds (PSCs) play a key role in stratospheric ozone depletion. Surface-catalyzed reactions on PSC particles generate chlorine compounds that photolyze readily to yield chlorine radicals, which in turn destroy ozone very efficiently. The most prevalent PSCs form at temperatures several degrees above the ice frost point and are believed to consist of HNO3 hydrates; however, their formation mechanism is unclear. Results of laboratory experiments are presented which indicate that the background stratospheric H2SO4/H2O aerosols provide an essential link in this mechanism: These liquid aerosols absorb significant amounts of HNO3 vapor, leading most likely to the crystallization of nitric acid trihydrate (NAT). The frozen particles then grow to form PSCs by condensation of additional amounts of HNO3 and H2O vapor. Furthermore, reaction probability measurements reveal that the chlorine radical precursors are formed readily at polar stratospheric temperatures not just on NAT and ice crystals, but also on liquid H2SO4 solutions and on solid H2SO4 hydrates. These results imply that the chlorine activation efficiency of the aerosol particles increases rapidly as the temperature approaches the ice frost point regardless of the phase or composition of the particles.
Hydration structure of the barite (001)–water interface: Comparison of x-ray reflectivity with molecular dynamics simulations

DOE PAGES

Bracco, Jacquelyn N.; Lee, Sang Soo; Stubbs, Joanne E.; ...

2017-05-11

The three-dimensional structure of the barite (001)-water interface was studied using in situ specular and non-specular X-ray reflectivity (XR). Displacements of the barium and sulfate ions in the surface of a barite crystal and the interfacial water structure were defined in the analyses. The largest relaxations (0.13 Å lateral and 0.08 Å vertical) were observed for the barium and sulfate ions in the topmost unit cell layer, which diminished rapidly with depth. The best fit structure identified four distinct adsorbed species, which in comparison with molecular dynamics (MD) simulations, reveals that they are associated with positions of adsorbed water, eachmore » of which coordinates one or two surface ions (either barium, sulfate, or both). These water molecules also adsorb in positions consistent with those of bariums and sulfates in the bulk crystal lattice. These results demonstrate the importance of combining high resolution XR with MD simulations to fully describe the atomic structure of the hydrated mineral surface. As a result, the agreement between the results indicates both the uniqueness of the structural model obtained from the XR analysis and the accuracy of the force field used in the simulations.« less
Hydration structure of the barite (001)–water interface: Comparison of x-ray reflectivity with molecular dynamics simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bracco, Jacquelyn N.; Lee, Sang Soo; Stubbs, Joanne E.

The three-dimensional structure of the barite (001)-water interface was studied using in situ specular and non-specular X-ray reflectivity (XR). Displacements of the barium and sulfate ions in the surface of a barite crystal and the interfacial water structure were defined in the analyses. The largest relaxations (0.13 Å lateral and 0.08 Å vertical) were observed for the barium and sulfate ions in the topmost unit cell layer, which diminished rapidly with depth. The best fit structure identified four distinct adsorbed species, which in comparison with molecular dynamics (MD) simulations, reveals that they are associated with positions of adsorbed water, eachmore » of which coordinates one or two surface ions (either barium, sulfate, or both). These water molecules also adsorb in positions consistent with those of bariums and sulfates in the bulk crystal lattice. These results demonstrate the importance of combining high resolution XR with MD simulations to fully describe the atomic structure of the hydrated mineral surface. As a result, the agreement between the results indicates both the uniqueness of the structural model obtained from the XR analysis and the accuracy of the force field used in the simulations.« less
Development of hydrate risk quantification in oil and gas production

NASA Astrophysics Data System (ADS)

Chaudhari, Piyush N.

Subsea flowlines that transport hydrocarbons from wellhead to the processing facility face issues from solid deposits such as hydrates, waxes, asphaltenes, etc. The solid deposits not only affect the production but also pose a safety concern; thus, flow assurance is significantly important in designing and operating subsea oil and gas production. In most subsea oil and gas operations, gas hydrates form at high pressure and low temperature conditions, causing the risk of plugging flowlines, with a undesirable impact on production. Over the years, the oil and gas industry has shifted their perspective from hydrate avoidance to hydrate management given several parameters such as production facility, production chemistry, economic and environmental concerns. Thus, understanding the level of hydrate risk associated with subsea flowlines is an important in developing efficient hydrate management techniques. In the past, hydrate formation models were developed for various flow-systems (e.g., oil dominated, water dominated, and gas dominated) present in the oil and gas production. The objective of this research is to extend the application of the present hydrate prediction models for assessing the hydrate risk associated with subsea flowlines that are prone to hydrate formation. It involves a novel approach for developing quantitative hydrate risk models based on the conceptual models built from the qualitative knowledge obtained from experimental studies. A comprehensive hydrate risk model, that ranks the hydrate risk associated with the subsea production system as a function of time, hydrates, and several other parameters, which account for inertial, viscous, interfacial forces acting on the flow-system, is developed for oil dominated and condensate systems. The hydrate plugging risk for water dominated systems is successfully modeled using The Colorado School of Mines Hydrate Flow Assurance Tool (CSMHyFAST). It is found that CSMHyFAST can be used as a screening tool in order to reduce the parametric study that may require a long duration of time using The Colorado School of Mines Hydrate Kinetic Model (CSMHyK). The evolution of the hydrate plugging risk along flowline-riser systems is modeled for steady state and transient operations considering the effect of several critical parameters such as oil-hydrate slip, duration of shut-in, and water droplet size on a subsea tieback system. This research presents a novel platform for quantification of the hydrate plugging risk, which in-turn will play an important role in improving and optimizing current hydrate management strategies. The predictive strength of the hydrate risk quantification and hydrate prediction models will have a significant impact on flow assurance engineering and design with respect to building safe and efficient hydrate management techniques for future deep-water developments.

Formation of protein molecular imprints within Langmuir monolayers: A quartz crystal microbalance study

PubMed Central

Turner, Nicholas W.; Wright, Bryon E.; Hlady, Vladimir; Britt, David W.

2008-01-01

Protein imprinting leading to enhanced rebinding of ferritin to ternary lipid monolayers is demonstrated using a quartz crystal microbalance. Monolayers consisting of cationic dioctadecyldimethylammonium bromide, non-ionic methyl stearate, and poly(ethylene glycol) bearing phospholipids were imprinted with ferritin at the air/water interface of a Langmuir-Blodgett trough and transferred hydrated to hydrophobic substrates for study. This immobilization was shown by fluorescence correlation spectroscopy to significantly hinder any further diffusion of lipids, while rebinding studies demonstrated up to a six-fold increase in ferritin adsorption to imprinted versus control monolayers. A diminished rebinding of ferritin to its imprint was observed through pH reduction to below the protein isoelectric point, demonstrating the electrostatic nature of the interaction. Rebinding to films where imprint pockets remained occupied by the template protein was also minimal. Studies with a smaller acidic protein revealed the importance of the steric influence of poly(ethylene glycol) in forming the protein binding pockets, as albumin-imprinted monolayers showed low binding of ferritin, while ferritin-imprinted monolayers readily accommodated albumin. The controllable structure-function relationship and limitations of this system are discussed with respect to the application of protein imprinting in sensor development as well as fundamental studies of proteins at dynamic interfaces. PMID:17204279
4-(3-Methylanilino)-N-[N-(1-methylethyl)carbamoyl]pyridinium-3-sulfonamidate (torasemide) methanol 0.25-solvate 0.25-hydrate

PubMed Central

Bartolucci, Gianluca; Bruni, Bruno; Coran, Silvia A.; Di Vaira, Massimo

2009-01-01

The title compound, C16H20N4O3S·0.25CH4O·0.25H2O, is a hydrate/methanol solvate of torasemide, a diuretic drug used in the treatment of hypertension. The asymmetric unit contains two torasemide molecules and half-occupied methanol and water molecules. It is isomorphous with the previously reported nonsolvated T–II form of torasemide. The water molecules contribute to the stability of the structure by participating in an extensive system of O—H⋯O hydrogen bonds; N—H⋯N and N—H⋯O hydrogen bonds are also present. Both asymmetric molecules of torasemide form inversion dimers in the crystal. PMID:21584012
An open-framework thorium sulfate hydrate with 11.5 A voids.

PubMed

Wilson, Richard E; Skanthakumar, S; Knope, Karah E; Cahill, Christopher L; Soderholm, L

2008-10-20

We report the synthesis of a thorium sulfate hydrate with 11.5 A open channels that propagate through the structure. The compound crystallizes in the tetragonal space group P4(2)/nmc, a = b = 25.890(4) A, c = 9.080(2) A, Z = 8, V = 6086.3(2) A(3). The thermal stability of the compound was investigated using thermogravimetric analysis and high-energy X-ray scattering (HEXS) revealing that the compound begins to undergo decomposition near 200 degrees C with an accompanied loss in crystallinity. The immediate coordination environment about the thorium atoms remains intact through heating to 500 degrees C as demonstrated by HEXS. Further heating reveals the formation of at least two crystalline phases, Th(SO4)2 and ThO2, which ultimately decompose to ThO2.
Comparison of Intermolecular Forces in Anhydrous Sorbitol and Solvent Cocrystals.

PubMed

Dierks, Teresa M; Korter, Timothy M

2017-08-03

The hygroscopicity of solid sorbitol is important for its utilization as a sweetener in the pharmaceutical and food industries. The molecular foundations of sorbitol hydration characteristics are explored here using two solvated cocrystals, sorbitol-water and sorbitol-pyridine. In this work, solid-state density functional theory and terahertz time-domain spectroscopy were used to evaluate the relative stabilities of these cocrystals as compared to anhydrous sorbitol in terms of conformational and cohesive energies. The modification of the hydrogen-bonding network in crystalline sorbitol by solvent molecules gives new insight into the origins of the notable stability of sorbitol-water as compared to similar solids such as mannitol-water. In particular, the energy analysis reveals that the relative instability of the mannitol hydrate is based primarily in the lack of water-water interactions which provide considerable stabilization in the sorbitol-water crystal.
Aqua(pentahydrogennitrilotris(methylenephosphonato))lithium hydrate [Li(H{sub 2}O)(N(CH{sub 2}PO{sub 3}){sub 3}H{sub 5})] • H{sub 2}O: Synthesis and structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Somov, N. V., E-mail: somov@phys.unn.ru; Chausov, F. F., E-mail: xps@ftiudm.ru; Zakirova, R. M., E-mail: ftt@udsu.ru

Aqua(pentahydrogennitrilotris(methylenephosphonato))lithium hydrate is a linear coordination polymer. Its crystal structure is described in space group P{sup –}1, Z = 2; a = 5.5732(2), b = 7.0106(2), and c = 16.9010(5) Å; α = 97.515(2)°, β = 94.551(2)°, and γ = 95.123(2)°. The tetrahedral coordination of the Li atom includes two oxygen atoms of a phosphonate ligand, one oxygen atom of another phosphonate ligand, and a water molecule. Complex formation is accompanied by closing of the eight-membered Li–O–P–C–N–C–P–O chelate ring. Polymeric chains run along the [100] direction. The chains are connected by hydrogen bonds.
Controlling the hydration of the skin though the application of occluding barrier creams

PubMed Central

Sparr, Emma; Millecamps, Danielle; Isoir, Muriel; Burnier, Véronique; Larsson, Åsa; Cabane, Bernard

2013-01-01

The skin is a barrier membrane that separates environments with profoundly different water contents. The barrier properties are assured by the outer layer of the skin, the stratum corneum (SC), which controls the transepidermal water loss. The SC acts as a responding membrane, since its hydration and permeability vary with the boundary condition, which is the activity of water at the outer surface of the skin. We show how this boundary condition can be changed by the application of a barrier cream that makes a film with a high resistance to the transport of water. We present a quantitative model that predicts hydration and water transport in SC that is covered by such a film. We also develop an experimental method for measuring the specific resistance to water transport of films made of occluding barrier creams. Finally, we combine the theoretical model with the measured properties of the barrier creams to predict how a film of cream changes the activity of water at the outer surface of the SC. Using the known variations of SC permeability and hydration with the water activity in its environment (i.e. the relative humidity), we can thus predict how a film of barrier cream changes SC hydration. PMID:23269846
Controlling the hydration of the skin though the application of occluding barrier creams.

PubMed

Sparr, Emma; Millecamps, Danielle; Isoir, Muriel; Burnier, Véronique; Larsson, Åsa; Cabane, Bernard

2013-03-06

The skin is a barrier membrane that separates environments with profoundly different water contents. The barrier properties are assured by the outer layer of the skin, the stratum corneum (SC), which controls the transepidermal water loss. The SC acts as a responding membrane, since its hydration and permeability vary with the boundary condition, which is the activity of water at the outer surface of the skin. We show how this boundary condition can be changed by the application of a barrier cream that makes a film with a high resistance to the transport of water. We present a quantitative model that predicts hydration and water transport in SC that is covered by such a film. We also develop an experimental method for measuring the specific resistance to water transport of films made of occluding barrier creams. Finally, we combine the theoretical model with the measured properties of the barrier creams to predict how a film of cream changes the activity of water at the outer surface of the SC. Using the known variations of SC permeability and hydration with the water activity in its environment (i.e. the relative humidity), we can thus predict how a film of barrier cream changes SC hydration.
Formation of Structured Water and Gas Hydrate by the Use of Xenon Gas in Vegetable Tissue

NASA Astrophysics Data System (ADS)

Ando, Hiroko; Suzuki, Toru; Kawagoe, Yoshinori; Makino, Yoshio; Oshita, Seiichi

Freezing is a valuable technique for food preservation. However, vegetables are known to be softening remarkably after freezing and thawing process. It is expected to find alternative technique instead of freezing. Recently, the application of structured water and/or gas hydrate had been attempted to prolong the preservation of vegetable. In this study, the formation process of structure water and/or gas hydrate in pure water and carrot tissue was investigated by using NMR relaxation times, T1 and T2, of which applying condition was up to 0.4MPa and 0.8MPa at 5oC. Under the pressure of 0.4MPa, no gas hydrate was appeared, however, at 0.8MPa, formation of gas hydrate was recognized in both water and carrot tissue. Once the gas hydrate formation process in carrot tissue started, T1 and T2 increased remarkably. After that, as the gas hydrate developed, then T1 and T2 turned to decrease. Since this phenomenon was not observed in pure water, it is suggested that behavior of NMR relaxation time just after the formation of gas hydrate in carrot tissue may be peculiar to compartment system such as inter and intracellular spaces.
Resveratrol-Loaded Lipid Nanocarriers: Correlation between In Vitro Occlusion Factor and In Vivo Skin Hydrating Effect

PubMed Central

Parenti, Carmela; Turnaturi, Rita

2017-01-01

Lipid nanocarriers show occlusive properties that may be related to their ability to improve skin hydration. The aim of this work was to evaluate the relationship between in vitro occlusion factor and in vivo skin hydration for three types of lipid nanocarriers: nanoemulsions (NEs), solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs). These lipid nanocarriers were loaded with trans-resveratrol (RSV) and incorporated in gel vehicles. In vitro occlusion factor was in the order SLNs > NLCs > NEs. Gels containing unloaded or RSV loaded lipid nanocarriers were applied on the back of a hand of 12 healthy volunteers twice a day for one week, recording skin hydration changes using the instrument Soft Plus. An increase of skin hydration was observed for all lipid nanocarriers (SLNs > NLCs > NEs). RSV loading into these nanocarriers did not affect in vitro and in vivo lipid nanocarriers effects. A linear relationship (r2 = 0.969) was observed between occlusion factor and in vivo increase of skin hydration. Therefore, the results of this study showed the feasibility of using the occlusion factor to predict in vivo skin hydration resulting from topical application of different lipid nanocarriers loading an active ingredient with no inherent hydrating activity. PMID:29232856
Hydrogen-bond symmetrization in methane and hydrogen hydrates in the Mbar range

NASA Astrophysics Data System (ADS)

Bove, L. E.; Ranieri, U.; Gaal, R.; Finocchi, F.; Kuhs, W. F.; Falenty, A.; Klotz, S.; Gillet, P.

2016-12-01

Ice-VII and ice-X phases are the most stable forms of ice at high temperature and extreme pressures, typical of the interiors of satellites and planets. The phase transition between them is a prototypical case of quantum-driven phenomenon, as it can be described as a quantum delocalization of protons in the middle of O-O distances. Recent studies on LiCl- and NaCl-doped ice 1-3 have shown that the presence of salt inclusions in the ice lattice suppresses the quantum behavior of protons, hindering the appearance of the symmetric phase, and possibly suppressing the predicted high temperature superionic phase. This finding stimulated the investigation of similar effects in other water-based compounds, which are thought to be present in icy bodies, namely hydrogen and methane high pressure hydrates. Few experiments have been performed in the past to identify signatures of the hydrogen-bond symmetrization in methane and hydrogen hydrates without reaching conclusive results4,5. Here we present new results on the hydrogen-bond symmetrization of methane and hydrogen hydrates using Raman scattering in the Mbar range and semiclassical simulations including nuclear quantum effects. 1 Bove L. E. et al., E_ect of salt on the H-bond symmetrization in ice, Proc. Natl. Acad. Sci. USA 112, 8216, 2015 ; 2. Bronstein Y. et al., Quantum versus classical protons in pure and salty ice under pressure, Phys. Rev. B 93, 024104, 2016. 3. Klotz S. et al., Ice VII from aqueous salt solutions: From a glass to a crystal with broken H-bonds, Nature Sci. Rep. , in press. 4. Tanaka T. et al., Phase changes of _lled ice Ih methane hydrate under low temperature and high pressure, J. Chem. Phys. 139, 104701, 2013 5. Hirai H. et al., Structural changes of _lled ice Ic hydrogen hydrate under low temperatures and high pressures from 5 to 50 GPa, J. Chem. Phys. 137, 074505, 2012
Selenium Derivatization of Nucleic Acids for Crystallography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang,J.; Sheng, J.; Carrasco, N.

2007-01-01

The high-resolution structure of the DNA (5'-GTGTACA-C-3') with the selenium derivatization at the 2'-position of T2 was determined via MAD and SAD phasing. The selenium-derivatized structure (1.28 {angstrom} resolution) with the 2'-Se modification in the minor groove is isomorphorous to the native structure (2.0 {angstrom}). To directly compare with the conventional bromine derivatization, we incorporated bromine into the 5-postion of T4, determined the bromine-derivatized DNA structure at 1.5 {angstrom} resolution, and found that the local backbone torsion angles and solvent hydration patterns were altered in the structure with the Br incorporation in the major groove. Furthermore, while the native andmore » Br-derivatized DNAs needed over a week to form reasonable-size crystals, we observed that the Se-derivatized DNAs grew crystals overnight with high-diffraction quality, suggesting that the Se derivatization facilitated the crystal formation. In addition, the Se-derivatized DNA sequences crystallized under a broader range of buffer conditions, and generally had a faster crystal growth rate. Our experimental results indicate that the selenium derivatization of DNAs may facilitate the determination of nucleic acid X-ray crystal structures in phasing and high-quality crystal growth. In addition, our results suggest that the Se derivatization can be an alternative to the conventional Br derivatization.« less
The effect of moisture on the structures and properties of lead halide perovskites: a first-principles theoretical investigation.

PubMed

Zhang, Lei; Ju, Ming-Gang; Liang, WanZhen

2016-08-17

With efficiencies exceeding 20% and low production costs, lead halide perovskite solar cells (PSCs) have become potential candidates for future commercial applications. However, there are serious concerns about their long-term stability and environmental friendliness, heavily related to their commercial viability. Herein, we present a theoretical investigation based on the ab initio molecular dynamics (AIMD) simulations and the first-principles density functional theory (DFT) calculations to investigate the effects of sunlight and moisture on the structures and properties of MAPbI3 perovskites. AIMD simulations have been performed to simulate the impact of a few water molecules on the structures of MAPbI3 surfaces terminated in three different ways. The evolution of geometric and electronic structures as well as the absorption spectra has been shown. It is found that the PbI2-terminated surface is the most stable while both the MAI-terminated and PbI2-defective surfaces undergo structural reconstruction, leading to the formation of hydrated compounds in a humid environment. The moisture-induced weakening of photoabsorption is closely related to the formation of hydrated species, and the hydrated crystals MAPbI3·H2O and MA4PbI6·2H2O scarcely absorb the visible light. The electronic excitation in the bare and water-absorbed MAPbI3 nanoparticles tends to weaken Pb-I bonds, especially those around water molecules, and the maximal decrease of photoexcitation-induced bond order can reach up to 20% in the excited state in which the water molecules are involved in the electronic excitation, indicating the accelerated decomposition of perovskites in the presence of sunlight and moisture. This work is valuable for understanding the mechanism of chemical or photochemical instability of MAPbI3 perovskites in the presence of moisture.
Characterizing Natural Gas Hydrates in the Deep Water Gulf of Mexico: Applications for Safe Exploration and Production Activities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bent, Jimmy

2014-05-31

In 2000 Chevron began a project to learn how to characterize the natural gas hydrate deposits in the deep water portion of the Gulf of Mexico (GOM). Chevron is an active explorer and operator in the Gulf of Mexico and is aware that natural gas hydrates need to be understood to operate safely in deep water. In August 2000 Chevron worked closely with the National Energy Technology Laboratory (NETL) of the United States Department of Energy (DOE) and held a workshop in Houston, Texas to define issues concerning the characterization of natural gas hydrate deposits. Specifically, the workshop was meantmore » to clearly show where research, the development of new technologies, and new information sources would be of benefit to the DOE and to the oil and gas industry in defining issues and solving gas hydrate problems in deep water.« less
Clinical study on orofacial photonic hydration using phototherapy and biomaterials

NASA Astrophysics Data System (ADS)

Lizarelli, Rosane F. Z.; Grandi, Natália D. P.; Florez, Fernando L. E.; Grecco, Clovis; Lopes, Luciana A.

2015-06-01

Skin hydration is important to prevent aging and dysfunction of orofacial system. Nowadays, it is known that cutaneous system is linked to muscle system, then every dentist need to treat healthy facial skin, as lips, keeping orofacial functions healthy. Thirty-two patients were treated using laser and led therapy single or associated to biomaterials (dermo-cosmetics) searching for the best protocol to promote skin hydration. Using a peace of equipment to measure electric impedance, percentage of water and oil from skin, before and after different treatments were analyzed. Statistic tests using 5% and 0.1% of significance were applied and results showed that light could improve hydration of epidermis layer of facial skin. Considering just light effect, using infrared laser followed by blue led system is more effective to hydration than just blue led system application. Considering dermo-cosmetic and light, the association between both presented the best result.
Effect of Material Ion Exchanges on the Mechanical Stiffness Properties and Shear Deformation of Hydrated Cement Material Chemistry Structure C-S-H Jennite -- A Computational Modeling Study

NASA Astrophysics Data System (ADS)

Adebiyi, Babatunde Mattew

Material properties and performance are governed by material molecular chemistry structures and molecular level interactions. Methods to understand relationships between the material properties and performance and their correlation to the molecular level chemistry and morphology, and thus find ways of manipulating and adjusting matters at the atomistic level in order to improve material performance, are required. A computational material modeling methodology is investigated and demonstrated for a key cement hydrated component material chemistry structure of Calcium-Silicate-Hydrate (C-S-H) Jennite in this work. The effect of material ion exchanges on the mechanical stiffness properties and shear deformation behavior of hydrated cement material chemistry structure of Calcium Silicate Hydrate (C-S-H) Jennite was studied. Calcium ions were replaced with Magnesium ions in Jennite structure of the C-S-H gel. Different level of substitution of the ions was used. The traditional Jennite structure was obtained from the American Mineralogist Crystal Structure Database and super cells of the structures were created using a Molecular Dynamics Analyzer and Visualizer Material Studio. Molecular dynamics parameters used in the modeling analysis were determined by carrying out initial dynamic studies. 64 unit cell of C-S-H Jennite was used in material modeling analysis studies based on convergence results obtained from the elastic modulus and total energies. NVT forcite dynamics using COMPASS force field based on 200 ps dynamics time was used to determine mechanical modulus of the traditional C-S-H gel and the Magnesium ion modified structures. NVT Discover dynamics using COMPASS forcefield was used in the material modeling studies to investigate the influence of ionic exchange on the shear deformation of the associated material chemistry structures. A prior established quasi-static deformation method to emulate shear deformation of C-S-H material chemistry structure that is based on a triclinic crystal structure was used, by deforming the triclinic crystal structure at 0.2 degree per time step for 75 steps of deformation. It was observed that there is a decrease in the total energies of the systems as the percentage of magnesium ion increases in the C-S-H Jennite molecular structure systems. Investigation of effect of ion exchange on the elastic modulus shows that the elastic stiffness modulus tends to decrease as the amount of Mg in the systems increases, using either COMPASS or universal force field. On the other hand, shear moduli obtained after deforming the structures computed from the stress-strain curve obtained from material modeling increases as the amount of Mg increases in the system. The present investigations also showed that ultimate shear stress obtained from predicted shear stress---strain also increases with amount of Mg in the chemistry structure. Present study clearly demonstrates that computational material modeling following molecular dynamics analysis methodology is an effective way to predict and understand the effective material chemistry and additive changes on the stiffness and deformation characteristics in cementitious materials, and the results suggest that this method can be extended to other materials.
Competitive Sorption of CO2 and H2O in 2:1 Layer Phyllosilicates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schaef, Herbert T.; Loring, John S.; Glezakou, Vassiliki Alexandra

The salting out effect, where increasing the ionic strength of aqueous solutions decreases the solubility of dissolved gases is a well-known phenomenon. Less explored is the opposite process where an initially anhydrous system containing a volatile, relatively non-polar component and inorganic ions is systematically hydrated. Expandable clays such as montmorillonite are ideal systems for exploring this scenario as they have readily accessible exchange sites containing cations that can be systematically dehydrated or hydrated, from near anhydrous to almost bulk-like water conditions. This phenomenon has new significance with the simultaneous implementation of geological sequestration and secondary utilization of CO2 to bothmore » mitigate climate warming and enhance extraction of methane from hydrated clay-rich formations. Here, the partitioning of CO2 and H2O between Na-, Ca-, and Mg-exchanged montmorillonite and variably hydrated supercritical CO2 (scCO2) was investigated using in situ X-ray diffraction, infrared (IR)spectroscopic titrations, and quartz crystal microbalance (QCM) measurements. Density functional theory calculations provided mechanistic insights. Structural volumetric changes were correlated to quantified changes in sorbed H2O and CO2 concentrations as a function of %H2O saturated in scCO2. Intercalation of CO2 is favored at low H2O/CO2 ratios in the interlayer region, where CO2 can solvate the interlayer cation. As the clay becomes more hydrated and the H2O/CO2 ratio increases, H2O displaces CO2 from the solvation shell of the cation and CO2 tends to segregate. This transition decreases both the entropic and enthalpic driving force for CO2 intercalation, consistent with experimentally observed loss of intercalated CO2.« less
Specific effects of background electrolytes on the kinetics of step propagation during calcite growth

NASA Astrophysics Data System (ADS)

Ruiz-Agudo, Encarnación; Putnis, Christine V.; Wang, Lijun; Putnis, Andrew

2011-07-01

The mechanisms by which background electrolytes modify the kinetics of non-equivalent step propagation during calcite growth were investigated using Atomic Force Microscopy (AFM), at constant driving force and solution stoichiometry. Our results suggest that the acute step spreading rate is controlled by kink-site nucleation and, ultimately, by the dehydration of surface sites, while the velocity of obtuse step advancement is mainly determined by hydration of calcium ions in solution. According to our results, kink nucleation at acute steps could be promoted by carbonate-assisted calcium attachment. The different sensitivity of obtuse and acute step propagation kinetics to cation and surface hydration could be the origin of the reversed geometries of calcite growth hillocks (i.e., rate of obtuse step spreading < rate of acute step spreading) observed in concentrated (ionic strength, IS = 0.1) KCl and CsCl solutions. At low IS (0.02), ion-specific effects seem to be mainly associated with changes in the solvation environment of calcium ions in solution. With increasing electrolyte concentration, the stabilization of surface water by weakly paired salts appears to become increasingly important in determining step spreading rate. At high ionic strength (IS = 0.1), overall calcite growth rates increased with increasing hydration of calcium in solution (i.e., decreasing ion pairing of background electrolytes for sodium-bearing salts) and with decreasing hydration of the carbonate surface site (i.e., increasing ion pairing for chloride-bearing salts). Changes in growth hillock morphology were observed in the presence of Li +, F - and SO42-, and can be interpreted as the result of the stabilization of polar surfaces due to increased ion hydration. These results increase our ability to predict crystal reactivity in natural fluids which contain significant amounts of solutes.
Chord length distributions interpretation using a polydispersed population: Modeling and experiments

NASA Astrophysics Data System (ADS)

Cameirao, A.; Le Ba, H.; Darbouret, M.; Herri, J.-M.; Peytavy, J.-L.; Glénat, P.

2012-03-01

Chord length distributions were measured during the crystallization of gas hydrates in a flow loop. The conditions on the flow loop were similar with the conditions in the marine pipelines. The flow loop was filled with water in oil emulsion and pressurized with methane (7 MPa) at low temperature (277 K). During crystallization water droplets crystallize and agglomerate. The CLD measures were interpreted in a preceding work [Le Ba et al., 2010] [1] by constructing random aggregates with known geometrical proprieties from a monodispersed population of droplets and calculating their CLD. Comparing calculated CLD with CLD from the experiment, the geometrical parameters: number of primary particles and fractal dimension of experimental aggregates are identified. However some differences remained between the experiment and the calculated CLD. In the present work the droplets population was considered polydispersed improving the comparison between the model and the experiment.
Transmission electron microscopy characterization of macromolecular domain cavities and microstructure of single-crystal calcite tooth plates of the sea urchin Lytechinus variegatus.

PubMed

Robach, J S; Stock, S R; Veis, A

2005-07-01

The calcite plates and prisms in Lytechinus variegatus teeth form a complex biocomposite and employ a myriad of strengthening and toughening strategies. These crystal elements have macromolecule-containing internal cavities that may act to prevent cleavage. Transmission electron microscopy employing a small objective aperture was used to quantify several characteristics of these cavities. Cavity diameters ranged from 10 to 225 nm, the mean cavity diameter was between 50 and 60 nm, and cavities comprised approximately 20% of the volume of the crystal. Some cavities exhibited faceting and trace analysis identified these planes as being predominately of {1014} type. Through focus series of micrographs show the cavities were homogeneously distributed throughout the foil. The electron beam decomposed a substance within cavities and this suggests that these cavities are filled with a hydrated organic phase.
Numerical Simulation of Response Characteristics of Audio-magnetotelluric for Gas Hydrate in the Qilian Mountain Permafrost, China

NASA Astrophysics Data System (ADS)

Xiao, Kun; Zou, Changchun; Yu, Changqing; Pi, Jinyun

2015-10-01

Audio-magnetotelluric (AMT) method is a kind of frequency-domain sounding technique, which can be applied to gas hydrate prospecting and assessments in the permafrost region due to its high frequency band. Based on the geological conditions of gas hydrate reservoir in the Qilian Mountain permafrost, by establishing high-resistance abnormal model for gas hydrate and carrying out numerical simulation using finite element method (FEM) and nonlinear conjugate gradient (NLCG) method, this paper analyzed the application range of AMT method and the best acquisition parameters setting scheme. When porosity of gas hydrate reservoir is less than 5%, gas hydrate saturation is greater than 70%, occurrence scale is less than 50 m, or bury depth is greater than 500 m, AMT technique cannot identify and delineate the favorable gas hydrate reservoir. Survey line should be more than twice the length of probable occurrence scale, while tripling the length will make the best result. The number of stations should be no less than 6, and 11 stations are optimal. At the high frequency section (10˜1000 Hz), there should be no less than 3 frequency points, 4 being the best number.

[Correction of the human body hydration in different periods of space flight].

PubMed

Noskov, V B

2003-01-01

Hydration level of the human body at the end of space flight is not same as at its beginning. This was the reason for development and testing of opposite in action methods for hydration improvement: at the onset of microgravity a dehydration therapy is applied and, on the contrary, in the final period of space flight methods for retaining body fluids are of preference. Consumption of a diuretic and a water-salt supplement by orbiting crews reached the required effect suggesting applicability of the pharmaceutical correction as a measure against dehydration.
Early Age Carbonation Heat and Products of Tricalcium Silicate Paste Subject to Carbon Dioxide Curing.

PubMed

Li, Zhen; He, Zhen; Shao, Yixin

2018-05-04

This paper presents a study on the carbonation reaction heat and products of tricalcium silicate (C₃S) paste exposed to carbon dioxide (CO₂) for rapid curing. Reaction heat was measured using a retrofitted micro-calorimeter. The highest heat flow of a C₃S paste subject to carbonation curing was 200 times higher than that by hydration, and the cumulative heat released by carbonation was three times higher. The compressive strength of a C₃S paste carbonated for 2 h and 24 h was 27.5 MPa and 62.9 MPa, respectively. The 24-h carbonation strength had exceeded the hydration strength at 28 days. The CO₂ uptake of a C₃S paste carbonated for 2 h and 24 h was 17% and 26%, respectively. The X-ray diffraction (XRD), transmission electron microscope coupled with energy dispersive spectrometer (TEM-EDS), and 29 Si magic angle spinning⁻nuclear magnetic resonance ( 29 Si MAS-NMR) results showed that the products of a carbonated C₃S paste were amorphous silica (SiO₂) and calcite crystal. There was no trace of calcium silicate hydrate (C⁻S⁻H) or other polymorphs of calcium carbonate (CaCO₃) detected.
Interaction between BaCO{sub 3} and OPC/BFS composite cements at 20 {sup o}C and 60 {sup o}C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Utton, C.A., E-mail: c.utton@sheffield.ac.u; Gallucci, E.; Hill, J.

2011-03-15

A BaCO{sub 3} slurry, containing radioactive {sup 14}C, is produced during the reprocessing of spent nuclear fuel. This slurry is encapsulated in a Portland-blastfurnace slag composite cement. The effect of BaCO{sub 3} on the hydration of OPC and Portland-blastfurnace slag cements has been studied in this work. Samples containing a simulant BaCO{sub 3} slurry were cured for up to 720 days at 20 and 60 {sup o}C and analysed by XRD, SEM(EDX) and ICC. BaCO{sub 3} reacted with OPC to precipitate BaSO{sub 4} from a reaction between soluble sulfate and BaCO{sub 3}. Calcium monocarboaluminate subsequently formed from the carbonate released.more » The monocarboaluminate precipitated as crystals in voids formed during hydration. At 60 {sup o}C in OPC, it was not identified by XRD, suggesting the phase is unstable in this system around this temperature. In the Portland-blastfurnace slag cements containing BaCO{sub 3}, less monocarboaluminate and BaSO{sub 4} were formed, but the hydration of BFS was promoted and monocarboaluminate was stable up to 60 {sup o}C.« less
Steps Towards Understanding Large-scale Deformation of Gas Hydrate-bearing Sediments

NASA Astrophysics Data System (ADS)

Gupta, S.; Deusner, C.; Haeckel, M.; Kossel, E.

2016-12-01

Marine sediments bearing gas hydrates are typically characterized by heterogeneity in the gas hydrate distribution and anisotropy in the sediment-gas hydrate fabric properties. Gas hydrates also contribute to the strength and stiffness of the marine sediment, and any disturbance in the thermodynamic stability of the gas hydrates is likely to affect the geomechanical stability of the sediment. Understanding mechanisms and triggers of large-strain deformation and failure of marine gas hydrate-bearing sediments is an area of extensive research, particularly in the context of marine slope-stability and industrial gas production. The ultimate objective is to predict severe deformation events such as regional-scale slope failure or excessive sand production by using numerical simulation tools. The development of such tools essentially requires a careful analysis of thermo-hydro-chemo-mechanical behavior of gas hydrate-bearing sediments at lab-scale, and its stepwise integration into reservoir-scale simulators through definition of effective variables, use of suitable constitutive relations, and application of scaling laws. One of the focus areas of our research is to understand the bulk coupled behavior of marine gas hydrate systems with contributions from micro-scale characteristics, transport-reaction dynamics, and structural heterogeneity through experimental flow-through studies using high-pressure triaxial test systems and advanced tomographical tools (CT, ERT, MRI). We combine these studies to develop mathematical model and numerical simulation tools which could be used to predict the coupled hydro-geomechanical behavior of marine gas hydrate reservoirs in a large-strain framework. Here we will present some of our recent results from closely co-ordinated experimental and numerical simulation studies with an objective to capture the large-deformation behavior relevant to different gas production scenarios. We will also report on a variety of mechanically relevant test scenarios focusing on effects of dynamic changes in gas hydrate saturation, highly uneven gas hydrate distributions, focused fluid migration and gas hydrate production through depressurization and CO2 injection.
Continuous Preparation of 1:1 Haloperidol-Maleic Acid Salt by a Novel Solvent-Free Method Using a Twin Screw Melt Extruder.

PubMed

Lee, Hung Lin; Vasoya, Jaydip M; Cirqueira, Marilia de Lima; Yeh, Kuan Lin; Lee, Tu; Serajuddin, Abu T M

2017-04-03

Salts are generally prepared by acid-base reaction in relatively large volumes of organic solvents, followed by crystallization. In this study, the potential for preparing a pharmaceutical salt between haloperidol and maleic acid by a novel solvent-free method using a twin-screw melt extruder was investigated. The pH-solubility relationship between haloperidol and maleic acid in aqueous medium was first determined, which demonstrated that 1:1 salt formation between them was feasible (pH max 4.8; salt solubility 4.7 mg/mL). Extrusion of a 1:1 mixture of haloperidol and maleic acid at the extruder barrel temperature of 60 °C resulted in the formation of a highly crystalline salt. The effects of operating temperature and screw configuration on salt formation were also investigated, and those two were identified as key processing parameters. Salts were also prepared by solution crystallization from ethyl acetate, liquid-assisted grinding, and heat-assisted grinding and compared with those obtained by melt extrusion by using DSC, PXRD, TGA, and optical microscopy. While similar salts were obtained by all methods, both melt extrusion and solution crystallization yielded highly crystalline materials with identical enthalpies of melting. During the pH-solubility study, a salt hydrate form was also identified, which, upon heating, converted to anhydrate similar to that obtained by other methods. There were previous reports of the formation of cocrystals, but not salts, by melt extrusion. 1 H NMR and single-crystal X-ray diffraction confirmed that a salt was indeed formed in the present study. The haloperidol-maleic acid salt obtained was nonhygroscopic in the moisture sorption study and converted to the hydrate form only upon mixing with water. Thus, we are reporting for the first time a relatively simple and solvent-free twin-screw melt extrusion method for the preparation of a pharmaceutical salt that provides material comparable to that obtained by solution crystallization and is amenable to continuous manufacturing and easy scale up.
A petroleum system model for gas hydrate deposits in northern Alaska

USGS Publications Warehouse

Lorenson, T.D.; Collett, Timothy S.; Wong, Florence L.

2011-01-01

Gas hydrate deposits are common on the North Slope of Alaska around Prudhoe Bay, however the extent of these deposits is unknown outside of this area. As part of a United States Geological Survey (USGS) and the Bureau of Land Management (BLM) gas hydrate research collaboration, well cutting and mud gas samples have been collected and analyzed from mainly industry-drilled wells on the Alaska North Slope for the purpose of prospecting for gas hydrate deposits. On the Alaska North Slope, gas hydrates are now recognized as an element within a petroleum systems approach or TPS (Total Petroleum System). Since 1979, 35 wells have been samples from as far west as Wainwright to Prudhoe Bay in the east. Geochemical studies of known gas hydrate occurrences on the North Slope have shown a link between gas hydrate and more deeply buried conventional oil and gas deposits. Hydrocarbon gases migrate from depth and charge the reservoir rock within the gas hydrate stability zone. It is likely gases migrated into conventional traps as free gas, and were later converted to gas hydrate in response to climate cooling concurrent with permafrost formation. Gas hydrate is known to occur in one of the sampled wells, likely present in 22 others based gas geochemistry and inferred by equivocal gas geochemistry in 11 wells, and absent in one well. Gas migration routes are common in the North Slope and include faults and widespread, continuous, shallowly dipping permeable sand sections that are potentially in communication with deeper oil and gas sources. The application of this model with the geochemical evidence suggests that gas hydrate deposits may be widespread across the North Slope of Alaska.
Point of zero potential of single-crystal electrode/inert electrolyte interface.

PubMed

Zarzycki, Piotr; Preočanin, Tajana

2012-03-15

Most of the environmentally important processes occur at the specific hydrated mineral faces. Their rates and mechanisms are in part controlled by the interfacial electrostatics, which can be quantitatively described by the point of zero potential (PZP). Unfortunately, the PZP value of specific crystal face is very difficult to be experimentally determined. Here we show that PZP can be extracted from a single-crystal electrode potentiometric titration, assuming the stable electrochemical cell resistivity and lack of specific electrolyte ions sorption. Our method is based on determining a common intersection point of the electrochemical cell electromotive force at various ionic strengths, and it is illustrated for a few selected surfaces of rutile, hematite, silver chloride, and bromide monocrystals. In the case of metal oxides, we have observed the higher PZP values than those theoretically predicted using the MultiSite Complexation Model (MUSIC), that is, 8.4 for (001) hematite (MUSIC-predicted ~6), 8.7 for (110) rutile (MUSIC-predicted ~6), and about 7 for (001) rutile (MUSIC-predicted 6.6). In the case of silver halides, the order of estimated PZP values (6.4 for AgCl<6.5 for AgBr) agrees well with sequence estimated from the silver halide solubility products; however, the halide anions (Cl(-), Br(-)) are attracted toward surface much stronger than the Ag(+) cations. The observed PZPs sequence and strong anions affinity toward silver halide surface can be correlated with ions hydration energies. Presented approach is the complementary one to the hysteresis method reported previously [P. Zarzycki, S. Chatman, T. Preočanin, K.M. Rosso, Langmuir 27 (2011) 7986-7990]. A unique experimental characterization of specific crystal faces provided by these two methods is essential in deeper understanding of environmentally important processes, including migration of heavy and radioactive ions in soils and groundwaters. Copyright © 2012 Elsevier Inc. All rights reserved.
Influence of precipitating agents on thermodynamic parameters of protein crystallization solutions.

PubMed

Stavros, Philemon; Saridakis, Emmanuel; Nounesis, George

2016-09-01

X-ray crystallography is the most powerful method for determining three-dimensional structures of proteins to (near-)atomic resolution, but protein crystallization is a poorly explained and often intractable phenomenon. Differential Scanning Calorimetry was used to measure the thermodynamic parameters (ΔG, ΔH, ΔS) of temperature-driven unfolding of two globular proteins, lysozyme, and ribonuclease A, in various salt solutions. The mixtures were categorized into those that were conducive to crystallization of the protein and those that were not. It was found that even fairly low salt concentrations had very large effects on thermodynamic parameters. High concentrations of salts conducive to crystallization stabilized the native folded forms of proteins, whereas high concentrations of salts that did not crystallize them tended to destabilize them. Considering the ΔH and TΔS contributions to the ΔG of unfolding separately, high concentrations of crystallizing salts were found to enthalpically stabilize and entropically destabilize the protein, and vice-versa for the noncrystallizing salts. These observations suggest an explanation, in terms of protein stability and entropy of hydration, of why some salts are good crystallization agents for a given protein and others are not. This in turn provides theoretical insight into the process of protein crystallization, suggesting ways of predicting and controlling it. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 642-652, 2016. © 2016 Wiley Periodicals, Inc.
Insight into Nucleation Mechanisms of Tetrahedral Materials from Advanced Molecular Dynamics Simulations

NASA Astrophysics Data System (ADS)

Bi, Yuanfei

This dissertation studies the nucleation mechanisms of ice, clathrate hydrate and silicon clathrate which all belong to tetrahedral materials and carry significant importance to modern society. Because of the stochastic nature and the ultra-fine scale of nucleation, the mechanisms through which these important tetrahedral materials form from liquid remain poorly understood. Our goal is to address the current knowledge gap between experiment and theory on the nucleation mechanisms by conducting molecular dynamics (MD) studies. To overcome the rare event nature of nucleation, an advanced sampling method Forward Flux Sampling (FFS) is integrated with classical MD simulations. This integration allows obtaining not only nucleation rate explicitly but also an ensemble of nucleation trajectories with their correct statistical weights. By analyzing the ensemble of trajectories obtained from FFS, we reveal the important details of nucleation at the molecular level, particular at the early stage of nucleation. By combining Backward Flux Sampling (BFS) with FFS, we can also compute the free energy profile of nucleation explicitly, which allows a comparison against the classical nucleation theory (CNT). We began our investigation by studying heterogeneous ice nucleation, which is the most relevant form of ice formation. In this part of study, we aim to understand the key microscopic factors that control ice formation, including surface hydrophilicity, surface crystallinity, and surface geometry. Our simulations reveal that heterogeneous ice nucleation on graphitic surfaces is controlled by the coupling of surface crystallinity and surface hydrophilicity. In particular, our analysis shows that the crystalline graphitic lattice with an appropriate hydrophilicity may indeed template ice basal plane by forming a strained ice layer, thus significantly enhance its ice nucleation efficiency. The templating effect is further found to transit from within the first contact layer of water to the second as the surface hydrophilicity increases, which yields an oscillating distinction between the crystalline and amorphous graphitic surfaces in their ice nucleation efficiency. With this understanding, we then shifted our focus on the role of surface geometry, where we find that an atomically sharp, concave wedge can further promote ice nucleation. Remarkably, our molecular analysis shows a significant enhancement of ice nucleation can emerge both when the geometry of a wedge matches the ice lattice and when such lattice match does not exist. We then investigated the nucleation of gas hydrate, a binary compound composed of water and natural gas, e.g., methane. To facilitate the application of FFS in studying gas hydrate nucleation, we proposed a new order parameter: Half-Cage Order Parameter (H-COP), based on the topological signature of hydrate structure, and conducted a pB histogram analysis to verify the effectiveness of the H-COP order parameter. Our analyses show that the nucleation of M-hydrate (M can be methane or carbon dioxide) starts in the vicinity of water-M interface, and gradually transit from amorphous to crystalline structures. This is the direct support to the proposed two-step nucleation mechanism of methane hydrate. However, within the ensemble of nucleation trajectories, we also identified some direct crystallization pathways without going through a amorphous phase in the nucleation of both M-hydrate and L-hydrate. Remarkably the free energy profile of L-hydrate nucleation, which is obtained independent of nucleation theory, is found to fit well against the CNT, albeit with noticeable differences when the nucleus is small. Therefore, the CNT-like free energy profile and the existence of multiple nucleation pathways indicate the near degeneracy of these pathways in their free energy profiles and highlight the complexity of hydrate nucleation. On the basis of these results, we further proposed a new perspective of gas hydrate nucleation, which can be considered to be an entropically driven, kinetic process that proceeds via multiple pathways that have similar free energy profiles. Finally, inspired by our insight gained in studying gas hydrate nucleation, we proposed a novel synthesis route to obtain inert gas silicon clathrate, which has an attractive opto-electronic property for energy application, but remains as an experimental challenge for synthesis. We thoroughly examined this proposal through high-throughput computational studies that show the novel phases of silicon could form spontaneously from liquid silicon in the presence of noble gases under high pressure and high temperature. In particular, our results show that a medium size of noble gas, e.g., Ar, can trigger the nucleation and growth of inert-gas silicon clathrate, whereas a small noble gas such as He is able to induce the formation of an unconventional, inclusion-type compound Si2He. Our findings, along with the gained molecular insights, thus strongly suggest it is viable to experimentally synthesize novel silicon phases with noble gas through high pressure and high temperature. (Abstract shortened by ProQuest.).
Water flow in carbon-based nanoporous membranes impacted by interactions between hydrated ions and aromatic rings.

PubMed

Liu, Jian; Shi, Guosheng; Fang, Haiping

2017-02-24

Carbon-based nanoporous membranes, such as carbon nanotubes (CNTs), graphene/graphene oxide and graphyne, have shown great potential in water desalination and purification, gas and ion separation, biosensors, and lithium-based batteries, etc. A deep understanding of the interaction between hydrated ions in an aqueous solution and the graphitic surface in systems composed of water, ions and a graphitic surface is essential for applications with carbon-based nanoporous membrane platforms. In this review, we describe the recent progress of the interaction between hydrated ions and aromatic ring structures on the carbon-based surface and its applications in the water flow in a carbon nanotube. We expect that these works can be extended to the understanding of water flow in other nanoporous membranes, such as nanoporous graphene, graphyne and stacked sheets of graphene oxide.
Effects of the Hydration State on the Mid-Infrared Spectra of Urea and Creatinine in Relation to Urine Analyses.

PubMed

Oliver, Katherine V; Maréchal, Amandine; Rich, Peter R

2016-06-01

When analyzing solutes by Fourier transform infrared (FT-IR) spectroscopy in attenuated total reflection (ATR) mode, drying of samples onto the ATR crystal surface can greatly increase solute band intensities and, therefore, aid detection of minor components. However, analysis of such spectra is complicated by the existence of alternative partial hydration states of some substances that can significantly alter their infrared signatures. This is illustrated here with urea, which is a dominant component of urine. The effects of hydration state on its infrared spectrum were investigated both by incubation in atmospheres of fixed relative humidities and by recording serial spectra during the drying process. Significant changes of absorption band positions and shapes were observed. Decomposition of the CN antisymmetric stretching (νas) band in all states was possible with four components whose relative intensities varied with hydration state. These correspond to the solution (1468 cm(-1)) and dry (1464 cm(-1)) states and two intermediate (1454 cm(-1) and 1443 cm(-1)) forms that arise from specific urea-water and/or urea-urea interactions. Such intermediate forms of other compounds can also be formed, as demonstrated here with creatinine. Recognition of these states and their accommodation in analyses of materials such as dried urine allows more precise decomposition of spectra so that weaker bands of diagnostic interest can be more accurately defined. © The Author(s) 2016.
Life Origination Hydrate Hypothesis (LOH-Hypothesis)

PubMed Central

Ostrovskii, Victor; Kadyshevich, Elena

2012-01-01

The paper develops the Life Origination Hydrate Hypothesis (LOH-hypothesis), according to which living-matter simplest elements (LMSEs, which are N-bases, riboses, nucleosides, nucleotides), DNA- and RNA-like molecules, amino-acids, and proto-cells repeatedly originated on the basis of thermodynamically controlled, natural, and inevitable processes governed by universal physical and chemical laws from CH4, niters, and phosphates under the Earth's surface or seabed within the crystal cavities of the honeycomb methane-hydrate structure at low temperatures; the chemical processes passed slowly through all successive chemical steps in the direction that is determined by a gradual decrease in the Gibbs free energy of reacting systems. The hypothesis formulation method is based on the thermodynamic directedness of natural movement and consists ofan attempt to mentally backtrack on the progression of nature and thus reveal principal milestones alongits route. The changes in Gibbs free energy are estimated for different steps of the living-matter origination process; special attention is paid to the processes of proto-cell formation. Just the occurrence of the gas-hydrate periodic honeycomb matrix filled with LMSEs almost completely in its final state accounts for size limitation in the DNA functional groups and the nonrandom location of N-bases in the DNA chains. The slowness of the low-temperature chemical transformations and their “thermodynamic front” guide the gross process of living matter origination and its successive steps. It is shown that the hypothesis is thermodynamically justified and testable and that many observed natural phenomena count in its favor. PMID:25382120
Influence of solidification accelerators on structure formation of anhydrite-containing binders

NASA Astrophysics Data System (ADS)

Anikanova, L.; Volkova, O.; Kudyakov, A.; Sarkisov, Y.; Tolstov, D.

2016-01-01

The article presents results of scientific analysis of chemical additives influence on acid fluoride binder. It was found that the influence of sulfate nature additives on the process of hydration and solidification of the binder is similar to influence of additives on indissoluble anhydrite. Additives with SO42- anion NO- are more efficient. The mentioned additives according to accelerating effect belong to the following succession: K2SO4 > Na2SO4 > FeSO4 > MgSO4. Facilitation of the process of hydration and solidification of the binder, increase in density and durability of the binder (32 MPa) is to the greatest extent achieved with the introduction of 2% sodium sulfate additive of the binder's mass into the composition of the binder along with the ultrasonic treatment of water solution. Directed crystal formation process with healing of porous structure by new growths presented as calcium sulfate dehydrate and hydroglauberite provides positive effect.
Single-phase and well-dispersed Cu1.75S nanocrystals by ambient pressure diethylene glycol solution synthesis

NASA Astrophysics Data System (ADS)

Zheng, Xuerong; Jin, Zhengguo; Liu, Hui; Wang, Yueqiu; Wang, Xin; Du, Haiyan

2013-02-01

Single-phase, well-dispersed Cu1.75S nanocrystals were synthesized by an ambient pressure, hydrazine hydrate and ethylenediamine co-assisted diethylene glycol based solution chemical process using copper chloride and thioacetamide as precursors at the temperature range from 180 to 210 °C. Influence of hydrazine hydrate and ethylenediamine adding amounts, synthetic temperature on crystal growth, size distribution and optical properties of the synthesized Cu1.75S nanocrystals were investigated by XRD, TEM, HRTEM, EDX and UV-vis measurements. The synthetic reaction at above 200 °C grew flaky-shaped nanocrystals with relatively narrow size distribution. The formation of single-phase Cu1.75S nanocrystals in the diethylene glycol based solution process might be involved in the presence of intermediate [Cu(en)n]1+ and [Cu(NH3)4]2+ complexes in reaction solution, providing a stable Cu(I) and Cu(II) valent-mixed precursor.
Infrared optical constants of H2O ice, amorphous nitric acid solutions, and nitric acid hydrates

NASA Technical Reports Server (NTRS)

Toon, Owen B.; Koehler, Birgit G.; Middlebrook, Ann M.; Tolbert, Margaret A.; Jordon, Joseph

1994-01-01

We determined the infrared optical constants of nitric acid trihydrate, nitric acid dihydrate, nitric acid monohydrate, and solid amorphous nitric acid solutions which crystallize to form these hydrates. We have also found the infrared optical constants of H2O ice. We measured the transmission of infrared light throught thin films of varying thickness over the frequency range from about 7000 to 500/cm at temperatures below 200 K. We developed a theory for the transmission of light through a substrate that has thin films on both sides. We used an iterative Kramers-Kronig technique to determine the optical constants which gave the best match between measured transmission spectra and those calculated for a variety of films of different thickness. These optical constants should be useful for calculations of the infrared spectrum of polar stratospheric clouds.
Laboratory and field studies of stratospheric aerosols: Phase changes under high supersaturation

NASA Technical Reports Server (NTRS)

Hallet, John

1991-01-01

It is well known that water in the form of isolated small droplets supercool as much as 40 C below their equilibrium melting point. Solutions similarly supercool (with respect to water) and supersaturate (with respect of the solute). Experiments are described in which bulk solutions typical of atmospheric aerosols (nitric acid, sulfuric acid, and hydrates; ammonium sulfate; ammonium bisulfate; sodium chloride) are supercooled and/or supersaturated and nucleated to initiate crystal growth. Supersaturation of 300 percent is readily attainable, with linear growth of crystals increasing roughly as (supercooling/supersaturation)sup 2. The implication of the experiments is that the situation of metastability in polar stratosphere clouds is very likely, with nucleation only occuring under a high degree of supercooling or supersaturation.
A history of neutrons in biology: the development of neutron protein crystallography at BNL and LANL.

PubMed

Schoenborn, Benno P

2010-11-01

The first neutron diffraction data were collected from crystals of myoglobin almost 42 years ago using a step-scan diffractometer with a single detector. Since then, major advances have been made in neutron sources, instrumentation and data collection and analysis, and in biochemistry. Fundamental discoveries about enzyme mechanisms, biological complex structures, protein hydration and H-atom positions have been and continue to be made using neutron diffraction. The promise of neutrons has not changed since the first crystal diffraction data were collected. Today, with the developments of beamlines at spallation neutron sources and the use of the Laue method for data collection, the field of neutrons in structural biology has renewed vitality.
DNA octaplex formation with an I-motif of water-mediated A-quartets: reinterpretation of the crystal structure of d(GCGAAAGC).

PubMed

Sato, Yoshiteru; Mitomi, Kenta; Sunami, Tomoko; Kondo, Jiro; Takénaka, Akio

2006-12-01

The crystal structure of the tetragonal form of d(gcGAAAgc) has been revised and reasonably refined including the disordered residues. The two DNA strands form a base-intercalated duplex, and the four duplexes are assembled according to the crystallographic 222 symmetry to form an octaplex. In the central region, the eight strands are associated by I-motif of double A-quartets. Furthermore, eight hydrated-magnesium cations link the four duplexes to support the octaplex formation. Based on these structural features, a proposal that folding of d(GAAA)n, found in the non-coding region of genomes, into an octaplex can induce slippage during replication to facilitate length polymorphism is presented.
Monomorphism of cytidine (Cyd) vs. polymorphism of 2'deoxycytidine (dCyd). Structural and functional consequences

NASA Astrophysics Data System (ADS)

Wiewiórowski, M.; Alejska, M.; Malinowska, N.; Bratek-Wiewiórowska, M. D.

1997-12-01

It has been found that 2'deoxycytidine (dCyd) crystallizes in different forms, denoted dCyd A, dCyd B and dCyd C·H 2O. In the crystal lattice of the newly discovered form dCydC·H 2O there is a crystalline water molecule present. The monohydrate of dCydC, under suitable conditions (RT, over P 2O 5, 48h), undergoes transformation into the fully dehydrated form—dCydC anhydro. The whole process of de- and re-hydratation has been observed by FTIR-PAS spectroscopy. The nature of the differences and similarities between structural and functional properties of crystalline forms of 2'dCyd and Cyd molecules has been discussed.
X-ray Diffraction from Membrane Protein Nanocrystals

PubMed Central

Hunter, M.S.; DePonte, D.P.; Shapiro, D.A.; Kirian, R.A.; Wang, X.; Starodub, D.; Marchesini, S.; Weierstall, U.; Doak, R.B.; Spence, J.C.H.; Fromme, P.

2011-01-01

Membrane proteins constitute >30% of the proteins in an average cell, and yet the number of currently known structures of unique membrane proteins is <300. To develop new concepts for membrane protein structure determination, we have explored the serial nanocrystallography method, in which fully hydrated protein nanocrystals are delivered to an x-ray beam within a liquid jet at room temperature. As a model system, we have collected x-ray powder diffraction data from the integral membrane protein Photosystem I, which consists of 36 subunits and 381 cofactors. Data were collected from crystals ranging in size from 100 nm to 2 μm. The results demonstrate that there are membrane protein crystals that contain <100 unit cells (200 total molecules) and that 3D crystals of membrane proteins, which contain <200 molecules, may be suitable for structural investigation. Serial nanocrystallography overcomes the problem of x-ray damage, which is currently one of the major limitations for x-ray structure determination of small crystals. By combining serial nanocrystallography with x-ray free-electron laser sources in the future, it may be possible to produce molecular-resolution electron-density maps using membrane protein crystals that contain only a few hundred or thousand unit cells. PMID:21190672

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