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Sample records for hydrated soft contact

  1. Soft lithography contacts to organics

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    Julia W.P. Hsu

    2005-07-01

    Full Text Available Organic materials play an increasingly important role in (optoelectronics, particularly in low-cost or flexible devices. A major challenge is the contact between the electrodes and the organic material. Processes developed for inorganic semiconductors are inapplicable because of the sensitivity of organic materials to heat, radiation, and chemicals. Deposition of metal(s through shadow masks onto organic materials is commonly used, despite problems with ill-controlled interfaces and material damage. In addition, conventional approaches restrict device size to >1 μm. Clearly, a better technique is needed. In this article, two soft lithography methods for making contacts to organic materials are reviewed: nanotransfer printing (nTP and soft-contact lamination (ScL. These new approaches produce devices that outperform those made by conventional methods. The link between better device performance and better interfacial control is explained, and nanoscale devices are described.

  2. Polymer-interaction driven diffusionof eyeshadow in soft contact lenses.

    Science.gov (United States)

    Tavazzi, Silvia; Rossi, Alessandra; Picarazzi, Sara; Ascagni, Miriam; Farris, Stefano; Borghesi, Alessandro

    2017-07-07

    Soft contact lenses used for the correction of ametropia are often made of hydrogel and silicone-hydrogel materials. Since they are placed directly on the surface of the eye and they are hydrated by tears, eye cosmetics can compromise the lens performance and, even worse, can be transported from an external environment to the ocular surface through the contact lens. The diffusion of the dye component of a purple eyeshadow in soft contact lenses of different materials is here evaluated. Diffusivity is found to be typically higher in silicone-hydrogels than in hydrogels. In hydrogels, diffusivity is greater in the case of lower oxygen transmissibility. Despite differences between materials, absorbed mass of dye is much larger (10-100 times) than the expected mass by simple hydration and swelling of the contact lens. The most contaminated materials are also resistant to cleaning solutions. The results indicate that, notwithstanding the complexity of contact lens networks, diffusion of dye is found to follow Fick's law and it is driven by polymer-dye interaction, which governs lens hydration and swelling. Copyright © 2017 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  3. Experimental Study on Soft X-ray Contact Microscopy for Biological Specimens

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    XIE Honglan; GAO Hongyi; JIANG Shiping; CHEN Jianwen; LU Peixiang; XU Zhizhan

    2002-01-01

    Using Hefei Synchrotron radiation as X-ray source and photoresist PMMA as recording medium, soft X-ray contact microscopic imaging experiment on hydrated leaf epidermal cells of a kind of dicotyledon is performed and its latent image is read out by a light microscope. Several main factors degrading the resolution of the image are discussed in detail.

  4. Corneal topography and soft contact lens fit.

    Science.gov (United States)

    Young, Graeme; Schnider, Cristina; Hunt, Chris; Efron, Suzanne

    2010-05-01

    To determine which ocular topography variables affect soft contact lens fit. Fifty subjects each wore three pairs of soft lenses in random succession (Vistakon Acuvue 2, Vistakon Acuvue Advance, Ciba Vision Night & Day), and various aspects of lens fit were evaluated. The steeper base curves of each type were worn in one eye and the flatter base curves in the other eye. Corneal topography data were collected using a Medmont E300 corneal topographer (Camberwell, Australia). Corneal curvature, shape factor (SF), and corneal height were measured over a 10 mm chord and also over the maximum measurable diameter. These were measured in the horizontal, vertical, steepest, and flattest meridians. With each lens type, the steeper base curve provided the best fit on the greatest proportion of eyes and the significant differences in various aspects of fit were noted between base curves. For each lens type, there was no significant difference in mean K-reading between those eyes best fit with the steeper base curve and those eyes best fit with the flatter base curve. Two of the lenses showed a positive correlation between centration and horizontal corneal height (maximum), whereas one lens showed a negative correlation between centration and horizontal SF (SF = e). Several lenses showed a positive correlation between post-blink movement and horizontal or vertical corneal SF. The measurement of corneal topography using current Placido disc instrumentation allows a better prediction of soft lens fit than by keratometry, but it is not reliable enough to enable accurate selection of the best fitting base curve. Some correlations are evident between corneal measurements; however, trial fitting remains the method of choice for selection of soft lens base curve.

  5. Soft Contact Lenses Safe for Kids and Teens, Review Finds

    Science.gov (United States)

    ... news release, Bullimore said the findings should reassure parents about the safety of soft contacts in children and teens. They may improve young people's self-esteem and quality of life, and have been shown ...

  6. Molecular modeling of the dissociation of methane hydrate in contact with a silica surface.

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    Bagherzadeh, S Alireza; Englezos, Peter; Alavi, Saman; Ripmeester, John A

    2012-03-15

    We use constant energy, constant volume (NVE) molecular dynamics simulations to study the dissociation of the fully occupied structure I methane hydrate in a confined geometry between two hydroxylated silica surfaces between 36 and 41 Å apart, at initial temperatures of 283, 293, and 303 K. Simulations of the two-phase hydrate/water system are performed in the presence of silica, with and without a 3 Å thick buffering water layer between the hydrate phase and silica surfaces. Faster decomposition is observed in the presence of silica, where the hydrate phase is prone to decomposition from four surfaces, as compared to only two sides in the case of the hydrate/water simulations. The existence of the water layer between the hydrate phase and the silica surface stabilizes the hydrate phase relative to the case where the hydrate is in direct contact with silica. Hydrates bound between the silica surfaces dissociate layer-by-layer in a shrinking core manner with a curved decomposition front which extends over a 5-8 Å thickness. Labeling water molecules shows that there is exchange of water molecules between the surrounding liquid and intact cages in the methane hydrate phase. In all cases, decomposition of the methane hydrate phase led to the formation of methane nanobubbles in the liquid water phase.

  7. Drug delivery through soft contact lenses: An introduction

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    Gourishanker Jha

    2011-01-01

    Full Text Available Current ophthalmic drug delivery systems are insufficient, specifically eye drops, which allow approximately 95% of the drug contained in the drops to be lost due to absorption through the conjunctiva or through the tear drainage. The use of soft contact lenses has been proposed as a method to deliver drugs to the eye in an efficient manner. The contact lenses restrict the drug from being lost to tear drainage by releasing the drug into two tear layers on either side of the contact lens, where it ultimately diffuses into the eye. By using loaded soft contact lenses, continuous drug release for extended period is possible. This paper focuses on the different methods of drug loading used throughout a polymer hydrogel.

  8. Measurement of the refractive index of soft contact lenses during wear.

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    Varikooty, Jalaiah; Keir, Nancy; Woods, Craig A; Fonn, Desmond

    2010-01-01

    To determine whether the refractive index (RI) of a soft contact lens can be evaluated using refractometry while the lens remains on the eye and to compare this with more traditional ex vivo RI measurements. A slitlamp apparatus was modified to incorporate a customized Atago hand refractometer. With a double-masked study design, nine adapted symptomatic soft contact lens wearers wore a contact lens in each eye (lotrafilcon B and etafilcon A) in a randomized order. In vivo RI was determined from the relative Brix scale measurements immediately after lens insertion and after 1 and 10 hr of lens wear. Ex vivo refractometry was performed after 10 hr of lens wear for comparison. Means +/- standard errors of the means are reported. In vivo RI values at baseline were 1.422 +/- 0.0004 (lotrafilcon B) and 1.405 +/- 0.0021 (etafilcon A); after 1 hr of lens wear, values were 1.423 +/- 0.0006 and 1.408 +/- 0.0007, respectively; and after 10 hr of lens wear, values were 1.424 +/- 0.0004 and 1.411 +/- 0.0010, respectively. Ex vivo RI values at the end of the 10 hr wearing period were 1.424 +/- 0.0003 (lotrafilcon B) and 1.412 +/- 0.0017 (etafilcon A). The change in in vivo RI across the day was statistically significant for the etafilcon A lens (repeated-measures analysis of variance, P0.05). This novel adaptation of refractometry was able to measure the RI of soft contact lenses during wear (without lens removal). End of day RI measurements using in vivo and ex vivo refractometry were comparable with each other. Future work is required to determine whether this in vivo method can improve our understanding of the relationships between soft contact lens RI, hydration, on-eye lens performance, and symptomology.

  9. Frictional Compliant Haptic Contact and Deformation of Soft Objects

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    Naci Zafer

    2016-05-01

    Full Text Available This paper is concerned with compliant haptic contact and deformation of soft objects. A human soft fingertip model is considered to act as the haptic interface and is brought into contact with and deforms a discrete surface. A nonlinear constitutive law is developed in predicting normal forces and, for the haptic display of surface texture, motions along the surface are also resisted at various rates by accounting for dynamic Lund-Grenoble (LuGre frictional forces. For the soft fingertip to apply forces over an area larger than a point, normal and frictional forces are distributed around the soft fingertip contact location on the deforming surface. The distribution is realized based on a kernel smoothing function and by a nonlinear spring-damper net around the contact point. Experiments conducted demonstrate the accuracy and effectiveness of our approach in real-time haptic rendering of a kidney surface. The resistive (interaction forces are applied at the user fingertip bone edge. A 3-DoF parallel robotic manipulator equipped with a constraint based controller is used for the implementation. By rendering forces both in lateral and normal directions, the designed haptic interface system allows the user to realistically feel both the geometrical and mechanical (nonlinear properties of the deforming kidney.

  10. Frictional Compliant Haptic Contact and Deformation of Soft Objects

    Directory of Open Access Journals (Sweden)

    Naci Zafer

    2016-05-01

    Full Text Available This paper is concerned with compliant haptic contact and deformation of soft objects. A human soft fingertip model is considered to act as the haptic interface and is brought into contact with and deforms a discrete surface. A nonlinear constitutive law is developed in predicting normal forces and, for the haptic display of surface texture, motions along the surface are also resisted at various rates by accounting for dynamic Lund-Grenoble (LuGre frictional forces. For the soft fingertip to apply forces over an area larger than a point, normal and frictional forces are distributed around the soft fingertip contact location on the deforming surface. The distribution is realized based on a kernel smoothing function and by a nonlinear spring-damper net around the contact point. Experiments conducted demonstrate the accuracy and effectiveness of our approach in real-time haptic rendering of a kidney surface. The resistive (interaction forces are applied at the user fingertip bone edge. A 3-DoF parallel robotic manipulator equipped with a constraint based controller is used for the implementation. By rendering forces both in lateral and normal directions, the designed haptic interface system allows the user to realistically feel both the geometrical and mechanical (nonlinear properties of the deforming kidney.

  11. Interactions of benzalkonium chloride with soft and hard contact lenses

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    Chapman, J.M.; Cheeks, L.; Green, K. (Medical College of Georgia, Augusta (USA))

    1990-02-01

    We measured the uptake and washout of benzalkonium chloride, using radioactive tracer, by representative hard and soft contact lenses. Uptake by soft contact lenses after 7 days of continuous exposure is high (30 to 56 micrograms/mg of lens weight), with a low percentage of washout in 24 hours (between 0.2% and 1.5% of total uptake). High-water content lenses absorb greater quantities of benzalkonium than do low-water content lenses. Hard lenses take up a much smaller quantity of benzalkonium but release between 30% and 60% of total uptake during washout for 24 hours. Fluorosilicone-acrylate polymer lenses adsorb and release the most preservative, while polymethylmethacrylate lenses (Paragon Optical Inc, Mesa, Ariz) adsorb and release the least. The released benzalkonium from either soft or hard lenses is of a sufficient concentration to be at or above the upper limits of safety.

  12. The conformity of a soft contact lens on the eye.

    Science.gov (United States)

    Funkenbusch, G M; Benson, R C

    1996-08-01

    An axisymmetric elastic shell deformation model has been created to predict the conformity of a soft contact lens when pressed against the eye. Regions of contact and gap may be predicted, and the nonuniform reaction pressure between the lens and eye may also be found. This is important for issues like abrasion and comfort. Bending, membrane and transverse shear loads within the lens are also computed. Commercial soft contact lenses and a representative eye shape are used for the examples. We find that the uniformity of loading against the eye is strongly affected by the degree to which the lens is shaped to fit the eye, and relatively unaffected by the thickness of the lens.

  13. Drop impact on soft surfaces: beyond the static contact angles.

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    Rioboo, Romain; Voué, Michel; Adão, Helena; Conti, Joséphine; Vaillant, Alexandre; Seveno, David; De Coninck, Joël

    2010-04-06

    The wettability of cross-linked poly(dimethylsiloxane) elastomer films and of octadecyltrichlorosilane self-assembled monolayers with water has been measured and compared using various methods. Contact angle hysteresis values were compared with values reported in the literature. A new method to characterize advancing, receding contact angles, and hysteresis using drop impact have been tested and compared with usual methods. It has been found that for the rigid surfaces the drop impact method is comparable with other methods but that for elastomer surfaces the hysteresis is function of the drop impact velocity which influences the extent of the deformation of the soft surface at the triple line.

  14. In Situ Soft X-ray Spectromicroscopy of Early Tricalcium Silicate Hydration

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    Sungchul Bae

    2016-12-01

    Full Text Available The understanding and control of early hydration of tricalcium silicate (C3S is of great importance to cement science and concrete technology. However, traditional characterization methods are incapable of providing morphological and spectroscopic information about in situ hydration at the nanoscale. Using soft X-ray spectromicroscopy, we report the changes in morphology and molecular structure of C3S at an early stage of hydration. In situ C3S hydration in a wet cell, beginning with induction (~1 h and acceleration (~4 h periods of up to ~8 h, was studied and compared with ex situ measurements in the deceleration period after 15 h of curing. Analysis of the near-edge X-ray absorption fine structure showed that the Ca binding energy and energy splitting of C3S changed rapidly in the early age of hydration and exhibited values similar to calcium silicate hydrate (C–S–H. The formation of C–S–H nanoseeds in the C3S solution and the development of a fibrillar C–S–H morphology on the C3S surface were visualized. Following this, silicate polymerization accompanied by C–S–H precipitation produced chemical shifts in the peaks of the main Si K edge and in multiple scattering. However, the silicate polymerization process did not significantly affect the Ca binding energy of C–S–H.

  15. Investigating the shelf life of disposable soft contact lenses

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    E. Chetty

    2008-01-01

    Full Text Available Numerous studies have been done to scrutinize the sterility and/or efficacy of contact lens solutions1-3, contact lens storage cases4-6 and soft contact lenses (SCLs 7-10. To the best of our knowledge, a paucity of research regarding the sterility or efficacy of expired SCLs that are in sealed packages exists. One may question the need to investigate this facet of contact lens research. Many blogs and Q&A websites, such as the Optiboard website11, feature contact lens practitioners or contact lens patients who are curious about the repercussions of using expired SCLs. The purpose of this pilot study is not to offer all the answers regarding expired contact lenses, but rather to initiate curiosity about the quality and utility of expired SCLs. This study endeavors to investigate the sterility of sealed SCLs that are past their expiry date. Fifty-four SCLs were tested for the presence of fungal (27 samples and bacterial (27 samples contamination. These samples included both expired and unexpired SCLs that were either blister packed or vial packed. A small percentage of the lenses testedpositive for contamination.

  16. Implicit frictional-contact model for soft particle systems

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    Nezamabadi, Saeid; Radjai, Farhang; Averseng, Julien; Delenne, Jean-Yves

    2015-10-01

    We introduce a novel numerical approach for the simulation of soft particles interacting via frictional contacts. This approach is based on an implicit formulation of the Material Point Method, allowing for large particle deformations, combined with the Contact Dynamics method for the treatment of unilateral frictional contacts between particles. This approach is both precise due to the treatment of contacts with no regularization and artificial damping parameters, and robust due to implicit time integration of both bulk degrees of freedom and relative contact velocities at the nodes representing the contact points. By construction, our algorithm is capable of handling arbitrary particle shapes and deformations. We illustrate this approach by two simple 2D examples: a Hertz contact and a rolling particle on an inclined plane. We also investigate the compaction of a packing of circular particles up to a solid fraction well above the jamming limit of hard particles. We find that, for the same level of deformation, the solid fraction in a packing of frictional particles is above that of a packing of frictionless particles as a result of larger particle shape change.

  17. Soft wearable contact lens sensor for continuous intraocular pressure monitoring.

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    Chen, Guo-Zhen; Chan, Ion-Seng; Leung, Leo K K; Lam, David C C

    2014-09-01

    Intraocular pressure (IOP) is a primary indicator of glaucoma, but measurements from a single visit to the clinic miss the peak IOP that may occur at night during sleep. A soft chipless contact lens sensor that allows the IOP to be monitored throughout the day and at night is developed in this study. A resonance circuit composed of a thin film capacitor coupled with a sensing coil that can sense corneal curvature deformation is designed, fabricated and embedded into a soft contact lens. The resonance frequency of the sensor is designed to vary with the lens curvature as it changes with the IOP. The frequency responses and the ability of the sensor to track IOP cycles were tested using a silicone rubber model eye. The results showed that the sensor has excellent linearity with a frequency response of ∼8 kHz/mmHg, and the sensor can accurately track fluctuating IOP. These results showed that the chipless contact lens sensor can potentially be used to monitor IOP to improve diagnosis accuracy and treatment of glaucoma.

  18. Capillary Pressure and Contact Line Force on a Soft Solid

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    Marchand, Antonin; Snoeijer, Jacco H; Andreotti, Bruno

    2012-01-01

    The surface free energy, or surface tension, of a liquid interface gives rise to a pressure jump when the interface is curved. Here we show that a similar capillary pressure arises at the interface of soft solids. We present experimental evidence that immersion of a thin elastomeric wire into a liquid induces a substantial elastic compression due to the solid capillary pressure at the bottom. We quantitatively determine the effective surface tension from the elastic displacement field, and find a value comparable to the liquid-vapor surface tension. Most importantly, these results also reveal the way the liquid pulls on the solid close to the contact line: the capillary force is not oriented along the liquid-air interface, nor perpendicularly to the solid surface, as previously hypothesized, but towards the interior of the liquid.

  19. Evaluation of prophilaxis of dry eye syndrome associated with soft contact lenses

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    Erkin Bilalov

    2013-12-01

    Full Text Available The purpose of the paper was to investigate the possibilities of dry eye syndrome prevention associated with soft contact lenses wearing. The algorithm of dry eye syndrome diagnostics and soft contact lenses selection has been developed based on the results of this work. The research showed that “Slezol Forte” is highly effective in the prevention of dry eye syndrome associated with wearing of soft contact lenses.

  20. Effects of Different Contact Lens Designs on Visual Quality Among the Soft Spherical Contact Lens Users

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    Mustafa Demir

    2013-10-01

    Full Text Available Purpose: To evaluate the effects of different lens designs on visual quality among soft spherical contact lens users. Material and Method: Forty eyes of twenty patients from our contact lens unit were included in this study. Refractive errors of the patients were between -0.50 and -6.0 diopters with 0.05. Total higher order aberration mean rms value was 0.29±0.10 µm without glasses, while it was 0.33±0.10 µm with Balafilcon A lenses and 0.31±0.10 µm with Senofilcon A lenses. Higher order aberration values measured after contact lens application did not show a significant difference for two contact lens designs (p>0.05. Discussion: High and low contrast sensitivity values were better with spectacles compared to contact lenses. We did not observe significant difference in higher order aberration values and visual quality between aspheric and spheric designed lenses. (Turk J Ophthalmol 2013; 43: 321-5

  1. Effect of skin hydration on the dynamics of fingertip gripping contact

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    André, T.; Lévesque, V.; Hayward, V.; Lefèvre, P.; Thonnard, J.-L.

    2011-01-01

    The dynamics of fingertip contact manifest themselves in the complex skin movements observed during the transition from a stuck state to a fully developed slip. While investigating this transition, we found that it depended on skin hydration. To quantify this dependency, we asked subjects to slide their index fingertip on a glass surface while keeping the normal component of the interaction force constant with the help of visual feedback. Skin deformation inside the contact region was imaged with an optical apparatus that allowed us to quantify the relative sizes of the slipping and sticking regions. The ratio of the stuck skin area to the total contact area decreased linearly from 1 to 0 when the tangential force component increased from 0 to a maximum. The slope of this relationship was inversely correlated to the normal force component. The skin hydration level dramatically affected the dynamics of the contact encapsulated in the course of evolution from sticking to slipping. The specific effect was to reduce the tendency of a contact to slip, regardless of the variations of the coefficient of friction. Since grips were more unstable under dry skin conditions, our results suggest that the nervous system responds to dry skin by exaggerated grip forces that cannot be simply explained by a change in the coefficient of friction. PMID:21490002

  2. Power Profiles of Commercial Multifocal Soft Contact Lenses

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    Kim, Eon; Bakaraju, Ravi C.; Ehrmann, Klaus

    2017-01-01

    ABSTRACT Purpose To evaluate the optical power profiles of commercially available soft multifocal contact lenses and compare their optical designs. Methods The power profiles of 38 types of multifocal contact lenses—three lenses each—were measured in powers +6D, +3D, +1D, −1D, −3D, and −6D using NIMO TR1504 (Lambda-X, Belgium). All lenses were measured in phosphate buffered saline across 8 mm optic zone diameter. Refractive index of each lens material was measured using CLR 12-70 (Index Instruments, UK), which was used for converting measured power in the medium to in-air radial power profiles. Results Three basic types of power profiles were identified: center-near, center-distance, and concentric-zone ring-type designs. For most of the lens types, the relative plus with respect to prescription power was lower than the corresponding spectacle add. For some lens types, the measured power profiles were shifted by up to 1D across the power range relative to their labeled power. Most of the lenses were designed with noticeable amounts of spherical aberration. The sign and magnitude of spherical aberration can either be power dependent or consistent across the power range. Conclusions Power profiles can vary widely between the different lens types; however, certain similarities were also observed between some of the center-near designs. For the more recently released lens types, there seems to be a trend emerging to reduce the relative plus with respect to prescription power, include negative spherical aberration, and keep the power profiles consistent across the power range. PMID:27748699

  3. Resultant vertical prism in toric soft contact lenses.

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    Sulley, Anna; Hawke, Ryan; Lorenz, Kathrine Osborn; Toubouti, Youssef; Olivares, Giovanna

    2015-08-01

    Rotational stability of toric soft contact lenses (TSCLs) is achieved using a range of designs. Designs utilising prism or peripheral ballast may result in residual prism in the optic zone. This study quantifies the vertical prism in the central 6mm present in TSCLs with various stabilisation methods. Vertical prism was computed using published refractive index and vertical thickness changes in the central optic zone on a full lens thickness map. Thickness maps were measured using scanning transmission microscopy. Designs tested were reusable, silicone hydrogel and hydrogel TSCLs: SofLens(®) Toric, PureVision(®)2 for Astigmatism, PureVision(®) Toric, Biofinity(®) Toric, Avaira(®) Toric, clariti(®) toric, AIR OPTIX(®) for ASTIGMATISM and ACUVUE OASYS(®) for ASTIGMATISM; with eight parameter combinations for each lens (-6.00DS to +3.00DS, -1.25DC, 90° and 180° axes). All TSCL designs evaluated had vertical prism in the optic zone except one which had virtually none (0.01Δ). Mean prism ranged from 0.52Δ to 1.15Δ, with three designs having prism that varied with sphere power. Vertical prism in ACUVUE OASYS(®) for ASTIGMATISM was significantly lower than all other TSCLs tested. TSCL designs utilising prism-ballast and peri-ballast for stabilisation have vertical prism in the central optic zone. In monocular astigmats fitted with a TSCL or those wearing a mix of toric designs, vertical prism imbalance could create or exacerbate disturbances in binocular vision function. Practitioners should be aware of this potential effect when selecting which TSCL designs to prescribe, particularly for monocular astigmats with pre-existing binocular vision anomalies, and when managing complaints of asthenopia in monocular astigmats. Copyright © 2015 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  4. Microbial contamination of soft contact lenses & accessories in asymptomatic contact lens users

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    Deeksha V Thakur

    2014-01-01

    Full Text Available Background & objectives: With increasing use of soft contact lenses the incidence of contact lens induced infections is also increasing. This study was aimed to assess the knowledge of new and existing contact lens users about the risk of microbial contamination associated with improper use and maintenance of contact lenses, type of microbial flora involved and their potential to cause ophthalmic infections. Methods: Four samples each from 50 participants (n=200 were collected from the lenses, lens care solutions, lens care solution bottles and lens cases along with a questionnaire regarding their lens use. The samples were inoculated onto sheep blood agar, Mac Conkey′s agar and Sabouraud′s dextrose agar. Organisms were identified using standard laboratory protocols. Results: Overall rate of microbial contamination among the total samples was 52 per cent. The most and the least contaminated samples were found to be lens cases (62% and lens care solution (42%, respectively. The most frequently isolated contaminant was Staphylococcus aureus (21% followed by Pseudomonas species (19.5%. Majority (64% of the participants showed medium grade of compliance to lens cleaning practices. Rate of contamination was 100 and 93.75 per cent respectively in those participants who showed low and medium compliance to lens care practices as compared to those who had high level of compliance (43.75% ( p0 <0.05. Interpretation & conclusions: Lens care practices amongst the participants were not optimum which resulted into high level contamination. Hence, creating awareness among the users about the lens care practices and regular cleaning and replacements of lens cases are required.

  5. Modeling of contact mechanics and friction limit surfaces for soft fingers in robotics, with experimental results

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    Xydas, N.; Kao, I.

    1999-09-01

    A new theory in contact mechanics for modeling of soft fingers is proposed to define the relationship between the normal force and the radius of contact for soft fingers by considering general soft-finger materials, including linearly and nonlinearly elastic materials. The results show that the radius of contact is proportional to the normal force raised to the power of {gamma}, which ranges from 0 to 1/3. This new theory subsumes the Hertzian contact model for linear elastic materials, where {gamma} = 1/3. Experiments are conducted to validate the theory using artificial soft fingers made of various materials such as rubber and silicone. Results for human fingers are also compared. This theory provides a basis for numerically constructing friction limit surfaces. The numerical friction limit surface can be approximated by an ellipse, with the major and minor axes as the maximum friction force and the maximum moment with respect to the normal axis of contact, respectively. Combining the results of the contact-mechanics model with the contact-pressure distribution, the normalized friction limit surface can be derived for anthropomorphic soft fingers. The results of the contact-mechanics model and the pressure distribution for soft fingers facilitate the construction of numerical friction limit surfaces, and will enable us to analyze and simulate contact behaviors of grasping and manipulation in robotics.

  6. The effect of multifocal soft contact lenses on peripheral refraction.

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    Kang, Pauline; Fan, Yvonne; Oh, Kelly; Trac, Kevin; Zhang, Frank; Swarbrick, Helen A

    2013-07-01

    To compare changes in peripheral refraction with single-vision (SV) and multifocal (MF) correction of distance central refraction with commercially available SV and MF soft contact lenses (SCLs) in young myopic adults. Thirty-four myopic adult subjects were fitted with Proclear Sphere and Proclear Multifocal SCLs to correct their manifest central refractive error. Central and peripheral refraction were measured with no lens wear and subsequently with the two different types of SCL correction. At baseline, refraction was myopic at all locations along the horizontal meridian. Peripheral refraction was relatively hyperopic compared with center at 30 and 35 degrees in the temporal visual field (VF) in low myopes, and at 30 and 35 degrees in the temporal VF, and 10, 30, and 35 degrees in the nasal VF in moderate myopes. Single-vision and MF distance correction with Proclear Sphere and Proclear Multifocal SCLs, respectively, caused a hyperopic shift in refraction at all locations in the horizontal VF. Compared with SV correction, MF SCL correction caused a significant relative myopic shift at all locations in the nasal VF in both low and moderate myopes and also at 35 degrees in the temporal VF in moderate myopes. Correction of central refractive error with SV and MF SCLs caused a hyperopic shift in both central and peripheral refraction at all positions in the horizontal meridian. Single-vision SCL correction caused the peripheral retina, which initially experienced absolute myopic defocus at baseline with no correction to experience an absolute hyperopic defocus. Multifocal SCL correction resulted in a relative myopic shift in peripheral refraction compared with SV SCL correction. This myopic shift may explain recent reports of reduced myopia progression rates with MF SCL correction.

  7. Effect of single vision soft contact lenses on peripheral refraction.

    Science.gov (United States)

    Kang, Pauline; Fan, Yvonne; Oh, Kelly; Trac, Kevin; Zhang, Frank; Swarbrick, Helen

    2012-07-01

    To investigate changes in peripheral refraction with under-, full, and over-correction of central refraction with commercially available single vision soft contact lenses (SCLs) in young myopic adults. Thirty-four myopic adult subjects were fitted with Proclear Sphere SCLs to under-correct (+0.75 DS), fully correct, and over-correct (-0.75 DS) their manifest central refractive error. Central and peripheral refraction were measured with no lens wear and subsequently with different levels of SCL central refractive error correction. The uncorrected refractive error was myopic at all locations along the horizontal meridian. Peripheral refraction was relatively hyperopic compared to center at 30 and 35° in the temporal visual field (VF) in low myopes and at 30 and 35° in the temporal VF and 10, 30, and 35° in the nasal VF in moderate myopes. All levels of SCL correction caused a hyperopic shift in refraction at all locations in the horizontal VF. The smallest hyperopic shift was demonstrated with under-correction followed by full correction and then by over-correction of central refractive error. An increase in relative peripheral hyperopia was measured with full correction SCLs compared with no correction in both low and moderate myopes. However, no difference in relative peripheral refraction profiles were found between under-, full, and over-correction. Under-, full, and over-correction of central refractive error with single vision SCLs caused a hyperopic shift in both central and peripheral refraction at all positions in the horizontal meridian. All levels of SCL correction caused the peripheral retina, which initially experienced absolute myopic defocus at baseline with no correction, to experience absolute hyperopic defocus. This peripheral hyperopia may be a possible cause of myopia progression reported with different types and levels of myopia correction.

  8. Characterization of nanophotonic soft contact lenses based on poly (2-hydroxyethyl methacrylate and fullerene

    Directory of Open Access Journals (Sweden)

    Debeljković Aleksandra D.

    2013-01-01

    Full Text Available This work presents comparative research of characteristics of a basic and new nanophotonic material, the latter of which was obtained by incorporation fullerene, C60, in the base material for soft contact lenses. The basic (SL38 and nanophotonic materials (SL38-A for soft contact lenses were obtained by radical polymerization of 2-hydroxyethyl methacrylate and 2-hydroxyethyl methacrylate and fullerene, which were derived by the technology in the production lab of the company Soleko (Milan, Italy. The materials were used for production of soft contact lenses in the company Optix (Belgrade, Serbia for the purposes of this research. Fullerene was used due to its apsorption transmission characteristics in ultraviolet, visible and near infrared spectrum. For the purposes of material characterization for potential application as soft contact lenses, network parameters were calculated and SEM analysis of the materials was performed while the optical properties of the soft contact lenses were measured by a Rotlex device. The values of the diffusion exponent, n, close to 0.5 indicated Fick's kinetics corresponding to diffusion. The investigated hydrogels could be classified as nonporous hydrogels. With Rotlex device, values of optical power and map of defects were showed. The obtained values of optical power and map of defects showed that the optical power of synthesized nanophotonic soft contact lens is identical to the nominal value while this was not the case for the basic lens. Also, the quality of the nanophotonic soft contact lens is better than the basic soft contact lens. Hence, it is possible to synthesize new nanophotonic soft contact lenses of desired optical characteristics, implying possibilities for their application in this field.

  9. Association between multifocal soft contact lens decentration and visual performance

    Directory of Open Access Journals (Sweden)

    Fedtke C

    2016-06-01

    Full Text Available Cathleen Fedtke,1 Klaus Ehrmann,1,2 Varghese Thomas,1 Ravi C Bakaraju1,2 1The Brien Holden Vision Institute, Clinical Trial Research Centre, 2School of Optometry and Vision Science, The University of New South Wales, Sydney, NSW, Australia Purpose: The aim of this study was to assess the association between decentration of several commercial multifocal soft contact lenses (MFCLs and various objective and subjective visual performance variables in presbyopic and non-presbyopic participants. Materials and methods: All presbyopic (age >40 years, near add ≥+1.25 D and non-presbyopic (age ≥18 years, no near add requirements, spherical equivalent ≤-0.50 D participants were each fitted bilaterally with six and two MFCLs (test lens, respectively, and with one single vision lens (control lens. Lens decentration, ie, the x- and y-differences between the contact lens and pupil centers, was objectively determined. Third-order aberrations were measured and compared. Visual performance (high- and low-contrast acuities and several subjective variables was analyzed for any associations (Pearson’s correlation, r with MFCL decentration. Results: A total of 17 presbyopic (55.1±6.9 years and eight non-presbyopic (31.0±3.3 years participants completed the study. All lenses displayed a temporal–inferior decentration (x=-0.36±0.29 mm, y=-0.28±0.28 mm, mean ± SD. Compared to the control, a significant inferior decentration was found for the Proclear® MFCL Near lens in both groups (ypresbyopic =-0.26 mm, ynon-presbyopic =-0.70 mm and for the Proclear® MFCL Distance lens in the non-presbyopic group (ynon-presbyopic =-0.69 mm. In both groups, lens-induced vertical coma (C(3, -1 was, by at least tenfold, significantly more positive for the Proclear® MFCL Distance lens and significantly more negative for the Proclear® MFCL Near lens. In the presbyopic group, the correlation of total MFCL decentration with vision variables was weak (r<|0

  10. Effect of soft contact lens curvature on dry eye of flight attendants

    Directory of Open Access Journals (Sweden)

    Chang-Liang Meng

    2014-10-01

    Full Text Available AIM: To discuss the effect of wearing customized curvature soft corneal contact lens to dry eye degree of flight attendants.METHODS: Eighty cases(160 eyesof flight attendants from China Southern were divided into two groups: control group 40 cases(80 eyeswearing ready-made Bausch soft corneal contact lens(curvature 8.4; the experiment group 40 cases(80 eyes, wearing Bausch soft corneal contact lens with customized curvature. Tear break-up time(BUT, Schirmer Ⅰ test(SⅠtand fluorescein(FLstaining were as dry eye evaluation index. The results was statistically analyzed.RESULTS: BUT, SⅠt average shortening value of the experimental group were less than that of the control group, there was statistical significance(PPCONCLUSION: Wearing customized curvature soft corneal contact lens can prevent the flight dry eye more effectively than fixed curvature product.

  11. A clinical study to evaluate therapeutic efficacy of soft contact lenses in corneal diseases

    Directory of Open Access Journals (Sweden)

    Sharda Punjabi

    2016-10-01

    Conclusions: Soft contact lenses can be safely advocated as a part of therapy along with adjuvant conventional management with well expected improvement in the ocular corneal diseases. [Int J Res Med Sci 2016; 4(10.000: 4632-4636

  12. Hydrophobins as aqueous lubricant additive for a soft sliding contact

    DEFF Research Database (Denmark)

    Lee, Seunghwan; Røn, Troels; Pakkanen, Kirsi I.

    2015-01-01

    lubrication characteristic is dominant via ‘self-healing’ mechanism. FpHYD5 revealed a better lubrication than HFBI presumably due to the presence of glycans and improved hydration of the sliding interface. Two type II hydrophobins function more favorably compared to a synthetic amphiphilic copolymer, PEO......-PPO-PEO, with a similar molecular weight. This is ascribed to higher amount of adsorption of the hydrophobins to hydrophobic surfaces from aqueous solution....

  13. Equivalences between refractive index and equilibrium water content of conventional and silicone hydrogel soft contact lenses from automated and manual refractometry.

    Science.gov (United States)

    González-Méijome, José M; López-Alemany, Antonio; Lira, Madalena; Almeida, José B; Oliveira, M Elisabete C D Real; Parafita, Manuel A

    2007-01-01

    The purpose of the present study was to develop mathematical relationships that allow obtaining equilibrium water content and refractive index of conventional and silicone hydrogel soft contact lenses from refractive index measures obtained with automated refractometry or equilibrium water content measures derived from manual refractometry, respectively. Twelve HEMA-based hydrogels of different hydration and four siloxane-based polymers were assayed. A manual refractometer and a digital refractometer were used. Polynomial models obtained from the sucrose curves of equilibrium water content against refractive index and vice-versa were used either considering the whole range of sucrose concentrations (16-100% equilibrium water content) or a range confined to the equilibrium water content of current soft contact lenses (approximately 20-80% equilibrium water content). Values of equilibrium water content measured with the Atago N-2E and those derived from the refractive index measurement with CLR 12-70 by the applications of sucrose-based models displayed a strong linear correlation (r2 = 0.978). The same correlations were obtained when the models are applied to obtain refractive index values from the Atago N-2E and compared with those (values) given by the CLR 12-70 (r2 = 0.978). No significantly different results are obtained between models derived from the whole range of the sucrose solution or the model limited to the normal range of soft contact lens hydration. Present results will have implications for future experimental and clinical research regarding normal hydration and dehydration experiments with hydrogel polymers, and particularly in the field of contact lenses. 2006 Wiley Periodicals, Inc.

  14. Design and economics of direct-contact salt hydrate storage systems

    Energy Technology Data Exchange (ETDEWEB)

    Wright, J. D.

    1981-05-01

    A salt-hydrate latent heat storage system is described in which oil is injected at the bottom of the container and exchanges heat as it floats to the top where it is pumped back to the heat source. Experiments are described which are meant to solve two problems. The first problem is to reliably inject the oil into the salt phase. The second is to minimize the carryover of salt hydrate into the oil, which can be done using two-stage coalescer-filters. Three systems are described and compared: a standard liquid-based sensible heat storage system, a latent heat storage design where oil is the heat-transfer fluid throughout the system, and a latent heat storage system where ethylene glycol/water is used in the collectors and oil in the storage tank. Direct-contact latent heat systems have overall costs roughly equal to those for water thermal storage tanks. The primary advantage of latent heat storage is its substantially smaller volume requirement. (LEW)

  15. Contact Angles on a Soft Solid: From Young’s Law to Neumann’s Law

    NARCIS (Netherlands)

    Marchand, A.; Das, S.; Snoeijer, J.H.; Andreotti, B.

    2012-01-01

    The contact angle that a liquid drop makes on a soft substrate does not obey the classical Young’s relation, since the solid is deformed elastically by the action of the capillary forces. The finite elasticity of the solid also renders the contact angles differently from those predicted by Neumann’s

  16. Contact angles on a soft solid: from Young's law to Neumann's law

    CERN Document Server

    Marchand, Antonin; Snoeijer, Jacco H; Andreotti, Bruno

    2012-01-01

    The contact angle that a liquid drop makes on a soft substrate does not obey the classical Young's relation, since the solid is deformed elastically by the action of the capillary forces. The finite elasticity of the solid also renders the contact angles different from that predicted by Neumann's law, which applies when the drop is floating on another liquid. Here we derive an elasto-capillary model for contact angles on a soft solid, by coupling a mean-field model for the molecular interactions to elasticity. We demonstrate that the limit of vanishing elastic modulus yields Neumann's law or a slight variation thereof, depending on the force transmission in the solid surface layer. The change in contact angle from the rigid limit (Young) to the soft limit (Neumann) appears when the length scale defined by the ratio of surface tension to elastic modulus $\\gamma/E$ reaches a few molecular sizes.

  17. Sugary interfaces mitigate contact damage where stiff meets soft

    Science.gov (United States)

    Yoo, Hee Young; Iordachescu, Mihaela; Huang, Jun; Hennebert, Elise; Kim, Sangsik; Rho, Sangchul; Foo, Mathias; Flammang, Patrick; Zeng, Hongbo; Hwang, Daehee; Waite, J. Herbert; Hwang, Dong Soo

    2016-06-01

    The byssal threads of the fan shell Atrina pectinata are non-living functional materials intimately associated with living tissue, which provide an intriguing paradigm of bionic interface for robust load-bearing device. An interfacial load-bearing protein (A. pectinata foot protein-1, apfp-1) with L-3,4-dihydroxyphenylalanine (DOPA)-containing and mannose-binding domains has been characterized from Atrina's foot. apfp-1 was localized at the interface between stiff byssus and the soft tissue by immunochemical staining and confocal Raman imaging, implying that apfp-1 is an interfacial linker between the byssus and soft tissue, that is, the DOPA-containing domain interacts with itself and other byssal proteins via Fe3+-DOPA complexes, and the mannose-binding domain interacts with the soft tissue and cell membranes. Both DOPA- and sugar-mediated bindings are reversible and robust under wet conditions. This work shows the combination of DOPA and sugar chemistry at asymmetric interfaces is unprecedented and highly relevant to bionic interface design for tissue engineering and bionic devices.

  18. Success rates in the correction of astigmatism with toric and spherical soft contact lens fittings

    OpenAIRE

    Sevda Aydin Kurna; Tomris Şengör; Murat Ün; et al

    2010-01-01

    Sevda Aydin Kurna, Tomris Şengör, Murat Ün, Suat AkiFatih Sultan Mehmet Education and Research Hospital, Ophthalmology Clinics, lstanbul, TurkeyObjectives: To evaluate success rates in the correction of astigmatism with toric and spherical soft contact lens fitting.Methods: 30 patients with soft toric lenses having more than 1.25 D of corneal astigmatism (25 eyes; Group A) or having 0.75–1.25 D of corneal astigmatism (22 eyes; Group B ) and 30 patients with soft sp...

  19. Success rates in the correction of astigmatism with toric and spherical soft contact lens fittings

    OpenAIRE

    Aydin Kurna, Sevda; Tomris,Sengor

    2010-01-01

    Sevda Aydin Kurna, Tomris Şengör, Murat Ün, Suat AkiFatih Sultan Mehmet Education and Research Hospital, Ophthalmology Clinics, lstanbul, TurkeyObjectives: To evaluate success rates in the correction of astigmatism with toric and spherical soft contact lens fitting.Methods: 30 patients with soft toric lenses having more than 1.25 D of corneal astigmatism (25 eyes; Group A) or having 0.75–1.25 D of corneal astigmatism (22 eyes; Group B ) and 30 patients with soft s...

  20. Stick-slip instability of soft contact in the presence of surfactant films

    Science.gov (United States)

    Dussaud, Anne

    2003-11-01

    Stick-slip instability in soft contact is a common problem in lubricating soft bearings. Although it is a much less explored area of application, it is also important in tactile perception when surfactants are rinsed from skin. Here, we designed a "wet" tribometer in a rotating geometry where the friction force between a ball and a soft flat substrate was monitored when it was totally submerged in a surfactant solution. The onset of the stick-slip instability was studied as a function of the surfactant adsorption and the hydrodynamic conditions (speed, viscosity, load). The results were analyzed by using an analogy with deformable roll coating flows.

  1. Acanthamoeba Species Keratitis in a Soft Contact Lens Wearer Molecularly Linked to Well Water

    Directory of Open Access Journals (Sweden)

    Samira Mubareka

    2006-01-01

    Full Text Available Acanthamoeba species keratitis has been associated with soft contact lens wear. In the present report, an epidemiological link was established between the patient's isolate and well water from the home using molecular methods. To the authors' knowledge, this is the first case in Canada where such a link has been established. Primary care practitioners and specialists, including ophthalmologists and infectious diseases specialists, must maintain a high degree of clinical suspicion in soft contact lens wearers with keratitis unresponsive to conventional topical and systemic treatment.

  2. Automatic detection of non-cosmetic soft contact lenses in ocular images

    Science.gov (United States)

    Erdogan, Gizem; Ross, Arun

    2013-05-01

    Recent research in iris recognition has established the impact of non-cosmetic soft contact lenses on the recognition performance of iris matchers. Researchers in Notre Dame demonstrated an increase in False Reject Rate (FRR) when an iris without a contact lens was compared against the same iris with a transparent soft contact lens. Detecting the presence of a contact lens in ocular images can, therefore, be beneficial to iris recognition systems. This study proposes a method to automatically detect the presence of non-cosmetic soft contact lenses in ocular images of the eye acquired in the Near Infrared (NIR) spectrum. While cosmetic lenses are more easily discernible, the problem of detecting non-cosmetic lenses is substantially difficult and poses a significant challenge to iris researchers. In this work, the lens boundary is detected by traversing a small annular region in the vicinity of the outer boundary of the segmented iris and locating candidate points corresponding to the lens perimeter. Candidate points are identified by examining intensity profiles in the radial direction within the annular region. The proposed detection method is evaluated on two databases: ICE 2005 and MBGC Iris. In the ICE 2005 database, a correct lens detection rate of 72% is achieved with an overall classification accuracy of 76%. In the MBGC Iris database, a correct lens detection rate of 70% is obtained with an overall classification accuracy of 66:8%. To the best of our knowledge, this is one of the earliest work attempting to detect the presence of non-cosmetic soft contact lenses in NIR ocular images. The results of this research suggest the possibility of detecting soft contact lenses in ocular images but highlight the need for further research in this area.

  3. Development of Soft-Sphere Contact Models for Thermal Heat Conduction in Granular Flows

    Energy Technology Data Exchange (ETDEWEB)

    Morris, A. B.; Pannala, S.; Ma, Zhiwen; Hrenya, C. M.

    2016-12-01

    Conductive heat transfer to flowing particles occurs when two particles (or a particle and wall) come into contact. The direct conduction between the two bodies depends on the collision dynamics, namely the size of the contact area and the duration of contact. For soft-sphere discrete-particle simulations, it is computationally expensive to resolve the true collision time because doing so would require a restrictively small numerical time step. To improve the computational speed, it is common to increase the 'softness' of the material to artificially increase the collision time, but doing so affects the heat transfer. In this work, two physically-based correction terms are derived to compensate for the increased contact area and time stemming from artificial particle softening. By including both correction terms, the impact that artificial softening has on the conductive heat transfer is removed, thus enabling simulations at greatly reduced computational times without sacrificing physical accuracy.

  4. [Use of soft contact lenses in the Riley-Day syndrome in a small child].

    Science.gov (United States)

    Hańczyc, P; Koziorowska, M; Zajac-Pytrus, H; Misiuk-Hojło, M

    1995-01-01

    We present the observation of a boy treated in our Ophthalmological Department in Wrocław from the age of 6 months up to 6 years for the serious keratitis with ulceration. We diagnosed Riley-Day syndrome with regard to many associated pathological features. The efficacy of the local treatment improved after application of soft contact lenses.

  5. Success rates in the correction of astigmatism with toric and spherical soft contact lens fittings

    Directory of Open Access Journals (Sweden)

    Sevda Aydin Kurna

    2010-08-01

    Full Text Available Sevda Aydin Kurna, Tomris Şengör, Murat Ün, Suat AkiFatih Sultan Mehmet Education and Research Hospital, Ophthalmology Clinics, lstanbul, TurkeyObjectives: To evaluate success rates in the correction of astigmatism with toric and spherical soft contact lens fitting.Methods: 30 patients with soft toric lenses having more than 1.25 D of corneal astigmatism (25 eyes; Group A or having 0.75–1.25 D of corneal astigmatism (22 eyes; Group B and 30 patients with soft spheric lenses having 0.75–1.25 D of corneal astigmatism (28 eyes; Group C or less than 0.75 D of corneal astigmatism (23 eyes; Group D were included in the study. Corrected and uncorrected monocular visual acuity measurement with logMAR, biomicroscopic properties, autorefractometry and corneal topography were performed for all patients immediately before and at least 20 minutes after the application of contact lenses. ­Success of contact lens fitting was evaluated by three parameters: astigmatic neutralization, visual success, and retinal deviation.Results: After soft toric lens application, spheric dioptres, cylindric and keratometric astigmatism, and retinal deviation decreased significantly in Groups A and B (P < 0.05. In Group C, spheric dioptres and retinal deviation decreased (P < 0.05, while cylindric and keratometric astigmatism did not change significantly (P > 0.05. In Group D, spheric dioptres, retinal deviation, and cylindric astigmatism decreased (P < 0.05. Keratometric astigmatism did not change significantly (P > 0.05 and astigmatic neutralization even increased.Conclusions: Visual acuity and residual spherical equivalent refraction remained between tolerable limits with the use of toric and spheric contact lenses. Spherical lenses failed to mask corneal toricity during topography, while toric lenses caused central neutralization and decrease in corneal cylinder in low and moderate astigmatic eyes.Keywords: astigmatism, soft toric lenses, soft spheric lenses

  6. Clinical performance of Rose K2 soft contact lens for keratoconus

    Directory of Open Access Journals (Sweden)

    Ihsan Yilmaz

    2017-08-01

    Full Text Available AIM: To evaluate the comfort and visual performance of Rose K2 soft contact lenses in patients with keratoconus.METHODS: Fifty eyes of 50 participants were included in this cross-sectional study. Each participant received a full ophthalmologic examination involving refraction, uncorrected visual acuity(UCVA, best spectacle corrected visual acuity(BCVA, slit-lamp biomicroscopy-fundoscopy, break-up time(BUT, corneal topography, and contrast sensitivity. After contact lens was fitted best contact lens corrected visual acuity(BCLCVA, contrast sensitivity, and comfort rating via visual analogue scales(VASwere performed.RESULTS: The mean age was 26.2±6.0(range: 16 to 39y. The mean logMAR UCVA, BCVA, and BCLCVA with Rose K2 soft(in orderwere 0.61±0.37(range: 0.15-1.3, 0.42±0.32(range: 0-1.3, and 0.18±0.20(range: 0-1.3. There were significant increases in visual acuities with contact lenses(P P CONCLUSION: Rose K2 soft contact lens can improve visual acuity, contrast sensitivity with comfort in patients with keratoconus.

  7. A Review of Techniques to Measure Protein Sorption to Soft Contact Lenses.

    Science.gov (United States)

    Hall, Brad; Forrest, James A; Jones, Lyndon

    2017-09-01

    To compare and critically evaluate a variety of techniques to measure the quantity and biological activity of protein sorption to contact lenses over short time periods. A literature review was undertaken investigating the major techniques to measure protein sorption to soft contact lens materials, with specific reference to measuring protein directly on lenses using in situ, ex situ, protein structural, and biological activity techniques. The use of in situ techniques to measure protein quantity provides excellent sensitivity, but many are not directly applicable to contact lenses. Many ex situ techniques struggle to measure all sorbed proteins, and these measurements can have significant signal interference from the lens materials themselves. Techniques measuring the secondary and tertiary structures of sorbed proteins have exhibited only limited success. There are a wide variety of techniques to measure both the amount of protein and the biological activity of protein sorbed to soft contact lens materials. To measure the mass of protein sorbed to soft contact lenses (not just thin films) over short time periods, the method of choice should be I radiolabeling. This technique is sensitive enough to measure small amounts of deposited protein, provided steps are taken to limit and measure any interaction of the iodine tracer with the materials. To measure the protein activity over short time periods, the method of choice should be to measure the biological function of sorbed proteins. This may require new methods or adaptations of existing ones.

  8. Simultaneous Soft Sensing of Tissue Contact Angle and Force for Millimeter-scale Medical Robots.

    Science.gov (United States)

    Arabagi, Veaceslav; Gosline, Andrew; Wood, Robert J; Dupont, Pierre E

    2013-01-01

    A novel robotic sensor is proposed to measure both the contact angle and the force acting between the tip of a surgical robot and soft tissue. The sensor is manufactured using a planar lithography process that generates microchannels that are subsequently filled with a conductive liquid. The planar geometry is then molded onto a hemispherical plastic scaffolding in a geometric configuration enabling estimation of the contact angle (angle between robot tip tangent and tissue surface normal) by the rotation of the sensor around its roll axis. Contact force can also be estimated by monitoring the changes in resistance in each microchannel. Bench top experimental results indicate that, on average, the sensor can estimate the angle of contact to within ±2° and the contact force to within ±5.3 g.

  9. Conjunctival Microbiome Changes Associated With Soft Contact Lens and Orthokeratology Lens Wearing.

    Science.gov (United States)

    Zhang, Haikun; Zhao, Fuxin; Hutchinson, Diane S; Sun, Wenfeng; Ajami, Nadim J; Lai, Shujuan; Wong, Matthew C; Petrosino, Joseph F; Fang, Jianhuo; Jiang, Jun; Chen, Wei; Reinach, Peter S; Qu, Jia; Zeng, Changqing; Zhang, Dake; Zhou, Xiangtian

    2017-01-01

    Usage of different types of contact lenses is associated with increased risk of sight-threatening complications. Changes in the ocular microbiome caused by contact lens wear are suggested to affect infection development in those individuals. To address this question, this study compares conjunctival microbial communities in contact lens wearers with those in noncontact lens wearers. Paired-end sequencing of the V3 region of the 16S rRNA gene was used to characterize the bacterial communities on the conjunctival surfaces of contact lens wearers and nonwearers. No differences in microbial diversity were detected between contact lens wearers and nonwearers. Nevertheless, some slight microbe variability was evident between these two different groups. Bacillus, Tatumella and Lactobacillus abundance was less in orthokeratology lens (OKL) wearers than in nonwearers. In soft contact lenses (SCL) wearers, Delftia abundance decreased whereas Elizabethkingia levels increased. The difference in the SCL and nonwearer group was smaller than that in the OKL group. Variations in the conjunctival taxonomic composition between SCL wearers were larger than those in other groups. Sex differences in the conjunctival microbiota makeup were only evident among nonwearers. Even though there were slight percentage changes between contact lens wearers and nonwearers in some microbes, there were no differences in their diversity. On the other hand, contact lens usage might cause relative abundance of some taxa to change. Our results will help assess whether or not conjunctival microbiome changes caused by contact lens wear affect infection risk.

  10. Soft Bandage Contact Lenses in Management of Early Bleb Leak Following Trabeculectomy

    Institute of Scientific and Technical Information of China (English)

    Zhenggen Wu; Chukai Huang; Yuqiang Huang; Wanqi Zhang; Di Ma

    2015-01-01

    Purpose:To investigate the efficacy of a soft bandage contact lens in the management of early bleb leak following tra-beculectomy. Methods: Between October 2011 and April 2013, 11 patients with early bleb leak following fornix-based trabeculectomy were instructed to wear a soft bandage contact lens 14 mm in diameter continuously for 1-2 weeks. The daily visual acuity, intraocular pressure (IOP), anterior chamber situation, and healing condition were measured at 1, 3, and 7 d, after con tact lens removal,.and 3 months after trabeculectomy..The con-ditions of blebs,.sensation of wearing contact lens,.and ad-verse events were recorded. Results:.Bleb leaks were observed at 2-8 d after surgery, (4.09±1.10 d on average). The daily LogMAR visual acuity did not significantly differ before and after contact lens wear (P>0.05). The IOP was significantly raised after at 1, 3, and 7 d after lens wear. (all P<0.05).The IOP at 3 months after lens wear did not significantly differ from that measured at lens removal (t=1.191, P=0.089). At 1 d after lens wear, 6 cases had deeper anterior chambers..All patients presented with a significantly deepened anterior chamber at 3 d after lens wear,.and were restored to the preoperative conditions..The bleb leakage was successfully treated at 7 d after lens removal in 10 patients, while 1 patient had to wear the contact lens for another 7 d for full healing of the bleb leak. No ocular infec-tion was noted throughout the management. Conclusion: A soft bandage contact lens of 14 mm diameter is a safe and efficacious therapy for an early bleb leak fol-lowing fornix-based trabeculectomy.

  11. Critical analysis of soft point contact Andreev reflection spectra between superconducting films and pressed In

    Science.gov (United States)

    Parab, Pradnya; Chauhan, Prashant; Muthurajan, H.; Bose, Sangita

    2017-04-01

    We present a critical analysis of an alternative technique of point contact Andreev reflection (PCAR) spectroscopy used to extract energy resolved information of superconductors which is based on making ‘soft-contacts’ between superconductors and indium. This technique is not sensitive to mechanical vibrations and hence can be used in a cryogen free platform increasing its accessibility to users having no access to cryogenic liquids. Through our experiments on large number of superconducting films we show that the PCAR spectra below the T c of In show sub-harmonic gap structures consistent with the theory of multiple Andreev reflection (MAR) and a zero bias conductance (ZBC) anomaly associated with the Josephson supercurrent. Furthermore, we demonstrate that large contact resistance with low transparency ballistic contacts in the PCAR regime are required to obtain reliable spectroscopic data. One limitation of the technique arises for low contact resistance junctions where the superconducting proximity effect (SPE) reduces the value of the superconducting energy gap.

  12. THREE-DIMENSIONAL CHARACTERISTICS AND HOMOGENIZATION OF ELECTROMAGNETIC FIELD IN SOFT-CONTACT CONTINUOUS CASTING MOLD

    Institute of Scientific and Technical Information of China (English)

    A.Y. Deng; G.L. Jia; J.C. He

    2001-01-01

    The three-dimensional electromagnetic characteristics and non-uniform distribution of electromagnetic field in soft-contact mold have been analyzed by numerical simulation. The results show that the maximum electromagnetic flux density is found in front of slit; the electromagnetic flux density becomes large as coil current and slit number increase. In a certain frequency range, the electromagnetic flux density increases with increasing frequency; and the frequency range is different with changing of azimuthal position along inner wall of mold. The uniformity of electromagnetic field is effected mainly by frequency and mold structure parameters. Increasing slit number and adjusting slit arrangement position can improve the electromagnetic flux density and the uniformity of electromagnetic field. For a soft-contact mold with 16 slits, when frequency is 20kHz, the optimal slit arrangement parameter is a: b = 1: 2.c=0.

  13. First Report of Hartmannella keratitis in a Cosmetic Soft Contact Lens Wearer in Iran

    Directory of Open Access Journals (Sweden)

    Hoda Abedkhojasteh

    2013-09-01

    Full Text Available Background: Poor hygiene will provide good condition for corneal infections by opportunistic free-living amoebae (FLA in soft contact lens wearers. In the present study an amoebic keratitis due to Hartmannella has been recognized in a 22-year-old girl with a history of improper soft contact lens use. She had unilateral keratitis on her left eye. Her clinical signs were eye pain, redness, blurred vision and photopho­bia. The round cysts of free-living amoebae were identified in non-nutrient agar medium by light microscopy. These cysts were suspected to be Hartmannella using morphological criteria. A PCR assay has been confirmed that the round cysts were belonged to H. vermiformis.

  14. The efficacy of soft contact lens disinfection solutions against Serratia marcescens and Pseudomonas aeruginosa.

    Science.gov (United States)

    Parment, P A; Colucci, B; Nyström, B

    1996-06-01

    Samples of five different solutions for disinfection of soft contact lenses were experimentally inoculated with a strain of Pseudomonas aeruginosa or Serratia marcescens. No bacteria could be detected after one hour in solutions with biguanids, while they survived in reduced number up to 72 h in solutions with polyquaternium as active substance. However, prolonged survival after one week could not be detected. Lenses treated with polyquaternium based contact lens disinfectant solutions overnight may still harbour bacteria, which might increase the risk for bacterial complications, such as keratitis.

  15. Influence of cosmetically tinted soft contact lenses on higher-order wavefront aberrations and visual performance.

    Science.gov (United States)

    Hiraoka, Takahiro; Ishii, Yuko; Okamoto, Fumiki; Oshika, Tetsuro

    2009-02-01

    To investigate the influence of cosmetically tinted soft contact lenses on ocular higher-order aberrations and visual performance, and to analyze the relationship between these parameters after the lens wear. In 44 eyes of 22 subjects, visual acuity, contrast sensitivity under photopic and mesopic conditions, and ocular higher-order aberrations were evaluated before and after wearing the tinted soft contact lenses (1-day Acuvue Colours; Vistakon, Jacksonville, FL). Contrast sensitivity under a photopic condition was determined at 3, 6, 12, and 18 cycles per degree, and the area under the log contrast sensitivity function (AULCSF) was calculated. Mesopic contrast sensitivity with and without glare was assessed. Ocular higher-order aberrations for a 4-mm pupil were measured, and coma-like, spherical-like, and total higher-order aberrations were determined. The tinted contact lens wearing resulted in significant decreases in log contrast sensitivity at all spatial frequencies (P 0.05), the changes in total higher-order aberrations showed a significant correlation with those in AULCSF (P 0.05). Cosmetically tinted contact lenses increase ocular higher-order aberrations and worsen contrast sensitivity under both photopic and mesopic conditions. Increases in higher-order aberrations are responsible for decreased contrast sensitivity under the photopic condition. Tinted contact lens wearers should be sufficiently informed about the possible reduction in optical quality of the eye and quality of vision.

  16. The Evaluation of the Effects of Differently-Designed Toric Soft Contact Lenses on Visual Quality

    Directory of Open Access Journals (Sweden)

    Sevda Aydın Kurna

    2013-08-01

    Full Text Available Purpose: The purpose of this study was to evaluate the effects of aspheric Balafilcon A and spherical Senofilcon A toric soft contact lenses, which have two different stabilization systems, on visual quality. Material and Method: Forty eyes of 20 patients who were followed up in our contact lens section were included in this study. Refractive errors of the patients were between -0.50 and -6.0 diopters of myopia and >0.75 diopter of astigmatism. The patients were randomly assigned to wear Balafilcon A (Purevision Toric, Baush&Lomb with prism balast toric system or spherical designed Senofilcon A (Acuvue Oasys for astigmatism, Johnson&Johnson with accelerated stabilization toric system. We recorded and compared the visual acuity with Snellen chart, contrast sensitivity with Bailey-Lovie chart in letters, mean root mean square (RMS of corneal aberration with by Nidek Magellan Mapper for all eyes with and without glasses and while wearing Balafilcon A or Senofilcon A toric soft contact lenses. Results: We did not observe any difference in visual acuity between contact lenses. Contrast sensitivity was increased approximately 4.8-5.4 letters with contact lenses. Total higher order aberrations of mean RMS values were 0.42±0.14 µm without contact lens, 0.37±0.23 µm with Balafilcon A lens, 0.43±0.15 µm with Senofilcon A (p=0.507. Trefoil values were significantly higher with Senofilcon A lenses when compared to Balafilcon A lenses. There was no statistically significant difference for other measured higher order aberrations. Discussion: High and low contrast vision values were adequate in both contact lens groups. There was a non-significant decrease in total higher order aberration values with aspheric design contact lenses when compared to spherical designs. Although there were differences in aberrations related to lens designs, they did not have significant effect on visual quality. (Turk J Ophthalmol 2013; 43: 253-7

  17. The polyvinylpyrrolidone graft copolymers and soft contact lenses on their basis

    Directory of Open Access Journals (Sweden)

    Oleg Suberlyak

    2014-12-01

    Full Text Available The graft polymerization of 2-hydroxyethyl methacrylate in presence of polyvinylpyrrolidone, which occurs through a stage of complex formation between the reactants, was investigated. The basic performance properties of hydrogel copolymers depending on their composition were investigated. A hydrogel polymeric material “Akrylan-LPI” for soft contact lenses was developed. Clinical testing confirmed the effectiveness of using of such lenses for vision correction as well as for eye injuries and burns treating.

  18. Drops on soft solids: Free energy and double transition of contact angles

    OpenAIRE

    Lubbers, Luuk A.; Weijs, Joost H.; Botto, Lorenzo; Das, Siddhartha; Andreotti, Bruno; Snoeijer, Jacco H.

    2013-01-01

    The equilibrium shape of liquid drops on elastic substrates is determined by minimising elastic and capillary free energies, focusing on thick incompressible substrates. The problem is governed by three length scales: the size of the drop $R$, the molecular size $a$, and the ratio of surface tension to elastic modulus $\\gamma/E$. We show that the contact angles undergo two transitions upon changing the substrates from rigid to soft. The microscopic wetting angles deviate from Young's law when...

  19. Efficacy of highly hydrophilic soft contact lenses for persistent corneal epithelial defects after anterior segment surgery

    Directory of Open Access Journals (Sweden)

    Zhi-Wei Peng

    2015-02-01

    Full Text Available AIM:To investigate the efficacy of highly hydrophilic soft contact lenses for persistent corneal epithelial defects.METHODS:In this retrospective case analysis, 28 patients(28 eyeswith persistent corneal epithelial defects after anterior segment surgery from January 2011 to June 2013 in our hospital were reviewed. After regular treatment for at least 2wk, the persistent corneal epithelial defects were treated with highly hydrophilic soft contact lenses, until the corneal epithelial healing. Continued to wear the same lens no more than 3wk, or in need of replacement the new one. All cases were followed up for 6mo. Key indicators of corneal epithelial healling, corneal fluorescein staining and ocular symptoms improvement were observed.RESULTS: Twenty-one eyes were cured(75.00%, markedly effective in 5 eyes(17.86%, effective in 2 eyes(7.14%, no invalid cases, the total efficiency of 100.00%. Ocular symptoms of 25 cases(89.29%relieved within 2d, the rest 3 cases(10.71%relieved within 1wk. The corneal epithelial of 6 cases(21.43%repaired in 3wk, 13 cases(46.43%in 6wk, 7 cases(25.00%in 9wk, 2 cases(7.14%over 12wk. There were no signs of secondary infection. And no evidence of recurrence in 6mo. CONCLUSION: Highly hydrophilic soft contact lenses could repair persistent corneal epithelial defects after anterior segment surgery significantly, while quickly and effectively relieve a variety of ocular irritation.

  20. Antifungal efficacy of soft contact lens disinfecting solutions against Fusarium solani and Candida albicans.

    Science.gov (United States)

    Mohammadinia, Mohadeseh; Amiri, Mohammad Aghazadeh; Delavari, Fatemeh; Yousefzadeh, Bahman; Maymeh, Maryam Heydarpour

    2012-03-01

    The aim was to evaluate the disinfection properties of six multi-purpose contact lens disinfection solutions (MPDS) available in Iran against Fusarium solani and Candida albicans, based on the International Organization for Standardization (ISO) 14729 guidelines. Three lots each of six multi-purpose solutions, namely, Renu MultiPlus, Solo Care Aqua, All-Clean soft, Contact All In One Advanced, Hippia, Ginza Multi-Purpose Solution and 0.9% normal saline solution were inoculated with standard strains of Fusarium solani (ATCC 36031) and Candida albicans (ATCC 10231). Surviving fungi were determined by counting colony-forming units on recovery plates at specified times. The mean log reduction in fungal numbers at the manufacturer's minimum recommended disinfection time was determined and compared with the criteria for stand-alone disinfection products for each MPDS against each fungal strain. Renu MultiPlus, Contact All In One Advanced and All-Clean Soft were effective in achieving the mean 1.0 log reduction in fungal numbers, based on ISO 14729 stand-alone primary acceptance criteria. Solo Care Aqua failed to achieve the ISO 14729 stand-alone primary acceptance criteria for Candida albicans. The other solutions were not effective against test microorganisms after the specified times. There were differences in the rates of disinfection efficacy. Generally, Renu MultiPlus, Contact All In One Advanced and All-Clean Soft exceeded the primary acceptance criteria of the ISO 14729 guidelines for stand-alone contact lens solutions. © 2012 Government of Iran. Clinical and Experimental Optometry © 2012 Optometrists Association Australia.

  1. Neuro fuzzy force control for soft dry contact Hertzian ultrasonic probe

    Science.gov (United States)

    Gallegos, E.; Baltazar, A.; Treesatayapun, C.

    2016-02-01

    In this work the use of a cartesian robotic manipulator as scanner for the automated identification of hidden defects in an aluminum test plate is proposed. The robotic manipulator includes a custom made soft deformable ultrasonic probe and a force sensor for the recollection of the ultrasonic signals and force feedback. The contact between the soft probe and the test plate is regulated using a Neuro Fuzzy controller in order to avoid the complex mathematical model produced by the interaction. Finally the use of the correlation coefficient is proposed for the post processing of the obtained ultrasonic signals and identification of hidden defects inside the test plate. Experimental studies demonstrated the efficiency of the method.

  2. Drops on soft solids: Free energy and double transition of contact angles

    CERN Document Server

    Lubbers, Luuk A; Botto, Lorenzo; Das, Siddhartha; Andreotti, Bruno; Snoeijer, Jacco H

    2013-01-01

    The equilibrium shape of liquid drops on elastic substrates is determined by minimising elastic and capillary free energies. The problem is governed by three length scales: the size of the drop $R$, the molecular size $a$, and the ratio of surface tension to elastic modulus $\\gamma/E$. We show that the contact angles undergo two transitions upon changing the substrates from rigid to soft. The microscopic wetting angles deviate from Young's law when $\\gamma/Ea \\gg 1$, while the apparent macroscopic angle only changes in the very soft limit $\\gamma/ER \\gg 1$. Details of the elastic deformations are worked out in the simplifying case where the surface energy of the solid is assumed independent of the elastic strain. The total free energy is found to be lowest on softer substrates, consistent with recent experiments. Finally, we discuss how the variational framework can be generalized to properly account for surface stress.

  3. Soft-Contact Printing of Nanoparticle-Based Nanoink for Functional Nanopatterns

    Directory of Open Access Journals (Sweden)

    Ujwal Kumar Thakur

    2015-01-01

    Full Text Available A simple solution-based soft-contact printing process that could easily generate sub-100 nm nanopatterns having negligible thickness of residual layer was developed. In this process, the thickness of residual layer could be significantly decreased by controlling the concentration of nanoink or by utilizing nanoink having high curing point. Furthermore, the additional sonication process, introduced to the soft-printing process, could facilitate further decreasing the thickness of residual layer. Consequently, ZnO nanostructures having negligible residual layer were successfully fabricated, and Ag nanostructures having 63.1% average transmittance were demonstrated. We expect that our printing process can be utilized to fabricate semitransparent conductor for various optoelectronic devices by optimizing the dimensional parameters of nanopatterns.

  4. Compliance and hygiene behaviour among soft contact lens wearers in the Maldives.

    Science.gov (United States)

    Gyawali, Rajendra; Nestha Mohamed, Fathimath; Bist, Jeewanand; Kandel, Himal; Marasini, Sanjay; Khadka, Jyoti

    2014-01-01

    Significant levels of non-compliance and poor hygiene among contact lens wearers have been reported previously from different parts of the world. This survey aimed at identifying the scope of hygiene and non-compliant behaviour of soft contact lens wearers in the Maldives. Established soft lens wearers attending two eye clinics in Male' city, were interviewed in office or via telephone. A set of interviewer-administered questions was used to access the subjective response on compliance and hygiene behaviour (hand and lens case hygiene, water exposure, adherence to lens replacement schedule, dozing and overnight wear, awareness of aftercare visits and reuse of disinfecting solution). Participants were also asked to rate themselves as a contact lens user based on their perceived compliance and hygiene practices. Out of 107 participants, 79 (74.8 per cent) were interviewed in the office and the rest via telephone. The majority of lens wearers were female, office workers and students, with a mean age of 20.64 ± 4.4 years. Mean duration of lens wear was 28.04 ± 8.36 months. Most of them were using spherical lenses (86.9 per cent) on a daily wear basis (96.3 per cent). Major reported forms of non-compliance were poor hand hygiene (60.7 per cent), lack of aftercare awareness (39.3 per cent), water exposure (35.5 per cent) and over-use of lenses (24.3 per cent). While females were more likely to overuse their lenses than males (p hygienic behaviour. A significant number of Maldivian contact lens wearers exhibited poor levels of hygiene and compliance with contact lenses and lens care systems. An effective educational reinforcement strategy needs to be developed to modify lens wearers' non-compliance. © 2013 The Authors. Clinical and Experimental Optometry © 2013 Optometrists Association Australia.

  5. Identification and enumeration of staphylococci from the eye during soft contact lens wear.

    Science.gov (United States)

    Leitch, E C; Harmis, N Y; Corrigan, K M; Willcox, M D

    1998-04-01

    An extensive study was conducted to identify and enumerate staphylococcal microbiota found on ocular sites during asymptomatic soft contact lens (SCL) wear. A biochemical identification system separately grouped the eight clinically relevant staphylococci. Total counts and isolation frequencies from SCLs and ocular sites were evaluated. The epidermidis group was the most numerous isolate from extended wear (EW) lenses; the capitis/warneri group was the most numerous (p microbiota of the ocular surface during SCL wear. Furthermore, an increase and a shift in staphylococcal microbiota between DW and EW regimes was highlighted.

  6. [Acanthamoeba keratitis after use of soft contact lenses--case report].

    Science.gov (United States)

    Ziak, P; Ondriska, F; Mrva, M

    2003-09-01

    The case history of a 39-year patient suffering from a deep inflammation of cornea and not responding to conventional antibiotic treatment is presented. The patient was using soft contact lenses during the period of initial symptoms; moreover, he was bathing in thermal bathing pool. A cultivation examination of smears from the area of corneal defect revealed the presence of Acanthamoeba lugdunensis in combination with bacterial infection by Pseudomonas aeruginosa. The available data indicate that it is the first case of acanthamoeba karatitis (AK) after the application of contact lenses in Slovakia. A long-term local treatment with propamidin isethionate (Brolene gtt, ung.) resulted in healing up. The subsequent vision after 16 months since the initial symptoms proved to be 6/12 (0.5). The healing of the centrally localized defect changed the curvature of cornea with consequent hypermetropic shift. The defect completely corrected the patient's myopia (-8.5). The paper describes present possibilities of AK therapy.

  7. Vision improvement by correcting higher-order aberrations with customized soft contact lenses in keratoconic eyes

    Science.gov (United States)

    Sabesan, Ramkumar; Jeong, Tae Moon; Carvalho, Luis; Cox, Ian G.; Williams, David R.; Yoon, Geunyoung

    2007-04-01

    Higher-order aberration correction in abnormal eyes can result in significant vision improvement, especially in eyes with abnormal corneas. Customized optics such as phase plates and customized contact lenses are one of the most practical, nonsurgical ways to correct these ocular higher-order aberrations. We demonstrate the feasibility of correcting higher-order aberrations and improving visual performance with customized soft contact lenses in keratoconic eyes while compensating for the static decentration and rotation of the lens. A reduction of higher-order aberrations by a factor of 3 on average was obtained in these eyes. The higher-order aberration correction resulted in an average improvement of 2.1 lines in visual acuity over the conventional correction of defocus and astigmatism alone.

  8. The effect of cleaning soft contact lenses. A scanning electron microscopic study.

    Science.gov (United States)

    Fowler, S A; Allansmith, M R

    1981-08-01

    Scanning electron microscopy was used to investigate the effectiveness of surfactant and enzyme cleaners in removing coatings from soft contact lenses. We examined ten continuously worn lenses and 15 lenses worn and cleaned regularly for at six months. About 30% of the surface of continuously worn lenses cleaned with surfactant or enzyme was uncoated; smooth, matted coating covered the remainder. Continuously worn lenses cleaned with the combination surfactant and enzyme cleaner had similar deposits covering 50% of the surface. Lenses worn and cleaned regularly had more deposits after cleaning with surfactant or enzyme cleaner than after cleaning with combination cleaner. Approximately 25% of the surface of lenses cleaned with the combination was coated with deposits. The deposits on both types of lenses were about 30% less thick after use of the combination cleaner than with either single cleaner. The coating on worn contact lenses is not completely removed by any method we tested.

  9. Steady-State Diffusion of Water through Soft-Contact LensMaterials

    Energy Technology Data Exchange (ETDEWEB)

    Fornasiero, Francesco; Krull, Florian; Radke, Clayton J.; Prausnitz, JohnM.

    2005-01-31

    Water transport through soft contact lenses (SCL) is important for acceptable performance on the human eye. Chemical-potential gradient-driven diffusion rates of water through soft-contact-lens materials are measured with an evaporation-cell technique. Water is evaporated from the bottom surface of a lens membrane by impinging air at controlled flow rate and humidity. The resulting weight loss of a water reservoir covering the top surface of the contact-lens material is recorded as a function of time. New results are reported for a conventional hydrogel material (SofLens{trademark} One Day, hilafilcon A, water content at saturation W{sub 10} = 70 weight %) and a silicone hydrogel material (PureVision{trademark}, balafilcon A, W{sub 10} = 36 %), with and without surface oxygen plasma treatment. Also, previously reported data for a conventional HEMA-SCL (W{sub 10} = 38 %) hydrogel are reexamined and compared with those for SofLens{trademark} One Day and PureVision{trademark} hydrogels. Measured steady-state water fluxes are largest for SofLens{trademark} One Day, followed by PureVision{trademark} and HEMA. In some cases, the measured steady-state water fluxes increase with rising relative air humidity. This increase, due to an apparent mass-transfer resistance at the surface (trapping skinning), is associated with formation of a glassy skin at the air/membrane interface when the relative humidity is below 55-75%. Steady-state water-fluxes are interpreted through an extended Maxwell-Stefan diffusion model for a mixture of species starkly different in size. Thermodynamic nonideality is considered through Flory-Rehner polymer-solution theory. Shrinking/swelling is self-consistently modeled by conservation of the total polymer mass. Fitted Maxwell-Stefan diffusivities increase significantly with water concentration in the contact lens.

  10. Polymer Electrolyte Fuel Cells Membrane Hydration by Direct Liquid Water Contact

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, M.S.; Zawodzinski, C.; Gottesfeld, S.

    1998-11-01

    An effective means of providing direct liquid hydration of the membrane tends to improve performance particularly of cells with thicker membranes or at elevated temperatures. Supplying the water to the membrane from the anode flow-field through the anode backing via wicks would appear to have advantages over delivering the water through the thickness of the membrane with regards to the uniformity and stability of the supply and the use of off-the-shelf membranes or MEAs. In addition to improving cell performance, an important contribution of direct liquid hydration approaches may be that the overall fuel cell system becomes simpler and more effective. The next steps in the evolution of this approach are a demonstration of the effectiveness of this technique with larger active area cells as well as the implementation of an internal flow-field water reservoir (to eliminate the injection method). Scale-up to larger cell sizes and the use of separate water channels within the anode flow-field is described.

  11. A liquid contact line receding on a soft gel surface : dip-coating geometry investigation

    CERN Document Server

    Kajiya, Tadashi; Royon, Laurent; Daerr, Adrian; Receveur, Mathieu; Limat, Laurent

    2015-01-01

    We studied the dynamics of a liquid contact line receding on a hydrophobic soft gel (SBS-paraffin). In order to realize a well-defined geometry with an accurate control of velocity, a dip-coating setup was implemented. Provided that the elastic modulus is small enough, a significant deformation takes place near the contact line, which in turn drastically influences the wetting behaviour. Depending on the translation velocity of the substrate, the contact line exhibits different regimes of motions. Continuous motions are observed at high and low velocities, meanwhile two types of stick-slip motion, periodic and erratic, appear at intermediate velocities. We suggest that the observed transitions could be explained in terms of the competition between different frequencies, i.e., the frequency of the strain field variation induced by the contact line motion and the crossover frequency of the gel related to the material relaxation. Our results provide systematic views on how the wetting of liquid is modified by th...

  12. Topical voriconazole therapy of Purpureocillium lilacinum keratitis that occurred in disposable soft contact lens wearers.

    Science.gov (United States)

    Todokoro, Daisuke; Yamada, Norihiro; Fukuchi, Mariko; Kishi, Shoji

    2014-10-01

    The objective of this study was to describe 2 cases of keratitis caused by Purpureocillium lilacinum (formerly Paecilomyces lilacinus) that occurred in disposable contact lens users, which were successfully treated with topical voriconazole. Case 1 was a healthy 44-year-old woman, who wore weekly disposable contact lenses and had developed a superficial corneal infection in her right eye. For diagnosis, corneal scraping and molecular identification of the cultured pathogen were performed. A corneal smear revealed the presence of fungi. The pathogen was identified as P. lilacinum by traditional morphological identification of fungal culture, and this identification was confirmed by DNA sequencing of the ribosomal internal transcribed spacer (ITS) sequence. Therapy with topical fluconazole, topical pimaricin (natamycin), and oral itraconazole were ineffective. Topical voriconazole showed a significant effect, and the keratitis was successfully treated. Case 2 was a 43-year-old woman with bilateral recurrent peripheral corneal ulcers by meibomian gland dysfunction, who used therapeutic bandage contact lenses on her left eye. However, a corneal abscess with hypopyon occurred in the eye after 3 months. The microbial smear examination showed the presence of fungi and the fungal culture, and the DNA sequence of ITS region revealed that the causative agent was P. lilacinum. The susceptibility testing against antifungal agents showed that voriconazole was effective. The lesion improved gradually by topical voriconazole. As a conclusion, P. lilacinum keratitis can occur in disposable soft contact lens wearer. Early and accurate detection of the pathogenic organism is essential. Topical voriconazole was effective against P. lilacinum keratitis.

  13. Solidification in Soft-Contact Continuous Casting Mold with Alternating Electromagnetic Field

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A three-dimensional coupled mathematical model for steel flow and solidification in a soft-contact EMC (Electro-Magnetic Casting) mold was developed. Non-staggered grid system with BFC (Body Fitted Coordinate) for the steel flow and solidification considering the complex geometry of the electromagnetic mold and the irregular meniscus shape of the melt were used. This mathematical model was applied to investigate the steel flow and solidification, and the effect of electromagnetic parameters on steel solidification in a 100 mm×100 mm square billet soft-contact mold. Numerical results showed that the electromagnetic induction heat mainly affects the distribution of steel temperature at upper part of EMC mold especially in the vicinity of meniscus. Consequently the steel temperature near the free surface is increased distinctly, and the hot-top condition is formed at the top of mold. It was clearly seen that the solidification start point shifts downward under the three-phase point by applying alternative electromagnetic field. As a result, the initial shell thickness gets thinner and the shell length shorter.

  14. Opto-thermal transient emission radiometry for rapid, non-destructive and non-contact determination of hydration and hydration depth profile in the skin of a grape

    NARCIS (Netherlands)

    Guo, X.; Bicanic, D.D.; Keijser, K.; Imhof, R.

    2003-01-01

    .The concept of optothermal transient emission radiometry at a wavelength of 2.94 µm was applied to non-destructively determine the level of hydration and the profile of hydration in the skin of intact fresh grapes taken from top and bottom sections of the same bunch.

  15. Direct visualization of tear film on soft contact lens using ultra-high resolution spectral domain optical coherence tomography

    Science.gov (United States)

    Wang, Jianhua; Jiao, Shuliang; Ruggeri, Marco; Wehbe, Hassan M.

    2008-02-01

    The integrity of the tear film on the surface of contact lenses is essential to maintaining visual clarity and the overall health of the superficial structures of the eye (cornea and conjunctiva) for contact lens wearers. It is very critical to evaluate pre- and post-lens tear films in contact lens practice to make sure the lens is properly fitted. Improper lens fitting may cause ocular discomfort, visual distortion and ocular infection. It is very often for soft contact lens wearers to experience dry eye, especially in the afternoon after wearing the lens for a period of time. Dry eye has been a common cause of contact lens drop-off. There is currently no method available to directly visualize the tears on and underneath the contact lens in situ on human eye, mainly due to the extremely difficulty in imaging the micrometer-thin tear layer. An ultra-high resolution spectral domain optical coherence tomography has been developed with a telecentric light delivery system mounted with a slit-lamp. The system has a 3 micrometer depth resolution with a scan width up to 15 mm. The system was used to image soft contact lenses on the human eye. For the first time to our knowledge, tear films on the center and edge of the soft contact lens were directly visualized in vivo.

  16. Contacting organic molecules by soft methods: towards molecule-based electronic devices.

    Science.gov (United States)

    Haick, Hossam; Cahen, David

    2008-03-01

    contacts easily and rapidly and allow many types of monolayers and metals to be analyzed. However, in their present forms such approaches are not technologically practical. Direct in situ vacuum evaporation of metals has been used successfully only with bifunctional molecules because it is too invasive and damaging, in general. A more general approach is indirect vacuum evaporation, where the metal atoms and clusters, emitted from the source, reach the sample surface in an indirect line of sight, while cooled by multiple collisions with an inert gas. This method has clear technological possibilities, but more research is needed to increase deposition efficiency and find ways to characterize the molecules at the interface and to prevent metal penetration between molecules or through pinholes, also if molecules lack reactive termination groups. This Account stresses the advantages, weak points, and possible routes for the development of contacting methods. This way it shows that there is at present no one ideal soft contacting method, whether it is because of limitations and problems inherent in each of the methods or because of insufficient understanding of the interfacial chemistry and physics. Hopefully, this Account will present the latter issue as a research challenge to its readers.

  17. Distribution of Magnetic Flux Density in Soft-Contact EMCC Rectangular Mold

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lin-tao; WANG En-gang; DENG An-yuan; HE Ji-cheng

    2006-01-01

    The distribution of the magnetic flux density in a soft-contact electromagnetic continuous casting (EMCC) rectangular mold was investigated. The experimental results show that with an increase in electric power, the magnetic flux density increases. The position where the maximum magnetic flux density appears will shift up when the coil moves to the top of the mold. At the same time, the maximum magnetic flux density will increase and the effective acting range of electromagnetic pressure will widen. As a result, in practice, the coil should be placed near the top part of the mold. The meniscus should be controlled near the top part of the coil, as this not only remarkably improves the billet surface quality but also saves energy. With the same electric power input, the higher the frequency, the lower the magnetic flux density.

  18. Acanthamoeba keratitis presenting as dendritic keratitis in a soft contact lens wearer.

    Science.gov (United States)

    Yeung, Edward Yip; Huang, Samuel Chao-Ming; Tsai, Ray Jui-Fang

    2002-03-01

    Acanthamoeba keratitis is a rare cause of corneal infection in Taiwan, which can result in devastating visual outcomes. A 37-year-old woman, who wore soft contact lenses, suffered from severe pain in her left eye. Biomicroscopy revealed dendritic keratitis, radial keratoneuritis, and fine keratic precipitates on her cornea. Culture, using non-nutrient agar plate seeded with Escherichia coli, resulted in heavy growth of Acanthamoeba. The inpatient treatment, including topical neomycin-polymyxin B and metronidazole (0.5%) eyedrops, oral ketoconazole, and then oral prednisolone, successfully controlled the corneal infection. The best-corrected visual acuity was 0.9 without any evidence of recurrence of infection after 21 months of follow up. Acanthamoeba keratitis can present as dendritic keratitis, which mimics herpes simplex infection, thus, delays appropriate treatment. Early diagnosis and judicious treatment are essential for restoring the vision and avoiding the subsequent need of penetrating keratoplasty.

  19. Bacterial colonization of disposable soft contact lenses is greater during corneal infiltrative events than during asymptomatic extended lens wear.

    Science.gov (United States)

    Sankaridurg, P R; Sharma, S; Willcox, M; Naduvilath, T J; Sweeney, D F; Holden, B A; Rao, G N

    2000-12-01

    Microorganisms, especially gram-negative bacteria, are considered to play a role in the etiology of certain corneal infiltrative events (CIEs) observed during soft contact lens wear. This study explored the possibility of microbial colonization of soft contact lenses as a risk factor leading to CIEs. In a clinical trial conducted from March 1993 to January 1996, 330 subjects wore disposable soft contact lenses on a 6-night extended-wear and disposal schedule. During this period, 4,321 lenses (118 during CIEs; 4,203 during asymptomatic lens wear) were recovered aseptically and analyzed for microbial colonization. A greater percentage of lenses were free from microbial colonization during asymptomatic wear than during CIEs (42 versus 23%; P ocular microbiota. Of the gram-positive bacteria, the incidence of Streptococcus pneumoniae was greater during CIE than during asymptomatic wear (7.6 versus 0.6%; P < 0. 0001). While gram-negative bacteria were seen in few cases during asymptomatic wear, their incidence during CIE in comparison to asymptomatic wear was substantial and significant (23.7 versus 3.8%; P < 0.0001). Also, the level of colonization was high. Of CIEs, events of microbial keratitis, contact lens acute red eye, and asymptomatic infiltrative keratitis were associated with lens colonization with gram-negative bacteria or S. pneumoniae. Colonization of soft contact lenses with pathogenic bacteria, especially gram-negative bacteria and S. pneumoniae, appears to be a significant risk factor leading to CIE.

  20. Air-coupled acoustic radiation force source for non-contact measurement of soft media elasticity (Conference Presentation)

    Science.gov (United States)

    Ambroziński, Lukasz; Pelivanov, Ivan; Song, Shaozhen; Yoon, Soon Joon; Li, David S.; Gao, Liang; Shen, Tueng T.; Wang, Ruikang K.; O'Donnell, Matthew

    2017-04-01

    Acoustic radiation force (ARF) is commonly used in ultrasound (US)-based elastography to generate shear waves deep within soft tissue. These waves can be detected with different methods, e.g. contact conventional ultrasound imaging probes or contact free magnetic resonance or optical coherence tomography (OCT). For many clinical applications, however, for instance the eye, a totally non-contact system for generation/detection of mechanical waves is needed. Here, we present a method for efficient non-contact excitation of broadband transverse mechanical waves in soft media. The approach is based on pushing the medium under study with a 1 MHz chirped US wave focused to its surface from air. The US beam reflected from the air/medium interface provides the ARF force to the medium surface launching a transient mechanical wave in the transverse (lateral) direction. The design and performance of the air-coupled transducer is discussed. The focal zone, peak pressure and acoustic intensity are measured for transducers with different numerical apertures. Time and frequency characteristics of the propagating mechanical waves, generated in soft tissue, are tracked with a phase-sensitive ultra-fast frame rate OCT imaging system. Application of the proposed method for non-contact, non-invasive, sub-mm resolution elasticity measurement in soft tissue is proposed.

  1. Peripheral refraction with different designs of progressive soft contact lenses in myopes.

    Science.gov (United States)

    Allinjawi, Kareem; Sharanjeet-Kaur, Sharanjeet-Kaur; Akhir, Saadah Mohamed; Mutalib, Haliza Abdul

    2016-01-01

    Aim: The purpose of this study was to compare the changes in relative peripheral refractive error produced by two different designs of progressive soft contact lenses in myopic schoolchildren. Methods: Twenty-seven myopic schoolchildren age between 13 to 15 years were included in this study. The measurements of central and peripheral refraction were made using a Grand-Seiko WR-5100K open-field autorefractometer without correction (baseline), and two different designs of progressive contact lenses (PCLs) (Multistage from SEED & Proclear from Cooper Vision) with an addition power of +1.50 D. Refractive power was measured at center and at eccentricities between 35º temporal to 35º nasal visual field (in 5º steps). Results: Both PCLs showed a reduction in hyperopic defocus at periphery. However, this reduction was only significant for the Multistage PCL (p= 0.015), (Proclear PCL p= 0.830).  Conclusion: Multistage PCLs showed greater reduction in peripheral retinal hyperopic defocus among myopic schoolchildren in comparison to Proclear PCLs.

  2. Development of ocular drug delivery systems using molecularly imprinted soft contact lenses.

    Science.gov (United States)

    Tashakori-Sabzevar, Faezeh; Mohajeri, Seyed Ahmad

    2015-05-01

    Recently, significant advances have been made in order to optimize drug delivery to ocular tissues. The main problems in ocular drug delivery are poor bioavailability and uncontrollable drug delivery of conventional ophthalmic preparations (e.g. eye drops). Hydrogels have been investigated since 1965 as new ocular drug delivery systems. Increase of hydrogel loading capacity, optimization of drug residence time on the ocular surface and biocompatibility with the eye tissue has been the main focus of previous studies. Molecular imprinting technology provided the opportunity to fulfill the above-mentioned objectives. Molecularly imprinted soft contact lenses (SCLs) have high potentials as novel drug delivery systems for the treatment of eye disorders. This technique is used for the preparation of polymers with specific binding sites for a template molecule. Previous studies indicated that molecular imprinting technology could be successfully applied for the preparation of SCLs as ocular drug delivery systems. Previous research, particularly in vivo studies, demonstrated that molecular imprinting is a versatile and effective method in optimizing the drug release behavior and enhancing the loading capacity of SCLs as new ocular drug delivery systems. This review highlights various potentials of molecularly imprinted contact lenses in enhancing the drug-loading capacity and controlling the drug release, compared to other ocular drug delivery systems. We have also studied the effects of contributing factors such as the type of comonomer, template/functional monomer molar ratio, crosslinker concentration in drug-loading capacity, and the release properties of molecularly imprinted hydrogels.

  3. In vitro release of two anti-muscarinic drugs from soft contact lenses

    Directory of Open Access Journals (Sweden)

    Hui A

    2017-09-01

    Full Text Available Alex Hui,1 Magdalena Bajgrowicz-Cieslak,2 Chau-Minh Phan,3 Lyndon Jones3 1School of Optometry and Vision Science, UNSW Sydney, Sydney, NSW, Australia; 2Department of Mechanics, Material Science and Engineering, Wroclaw University of Technology, Wroclaw, Poland; 3Centre for Contact Lens Research, School of Optometry & Vision Science, University of Waterloo, Waterloo, ON, Canada Abstract: The purpose of this study was to investigate the release of the anti-myopia drugs atropine sulfate and pirenzepine dihydrochloride from commercially available soft contact lenses. Standard ultraviolet (UV absorbance–concentration curves were generated for atropine and pirenzepine. Ten commercially available contact lenses, including four multifocal lenses, were loaded by soaking in atropine or pirenzepine solutions at two different concentrations (10 mg/mL and 1 mg/mL. The release of the drugs into phosphate-buffered saline was determined over the course of 24 hours at 34°C using UV absorbance. Materials with surface charge released the greatest amount of atropine when loaded with either concentration when compared to the other lens types (p<0.05, releasing upward of 1.026±0.035 mg/lens and 0.979±0.024 mg/lens from etafilcon A and ocufilcon A, respectively. There were no significant differences in the amount of atropine or pirenzepine released from the multifocal and non-multifocal lenses made from the same lens materials. Narafilcon A material demonstrated prolonged release of up to 8 hours when loaded with pirenzepine, although the overall dose delivered from the lens into the solution was among the lowest of the materials investigated. The rest of the lenses reached a plateau within 2 hours of release, suggesting that they were unable to sustain drug release into the solution for long periods of time. Given that no single method of myopia control has yet shown itself to be completely effective in preventing myopia progression, a combination of

  4. Exploring pH-Sensitive Hydrogels Using an Ionic Soft Contact Lens: An Activity Using Common Household Materials

    Science.gov (United States)

    Chen, Yueh-Huey; He, Yu-Chi; Yaung, Jing-Fun

    2014-01-01

    Hydrogels of the so-called smart polymers or environment-sensitive polymers are important modern biomaterials. Herein, we describe a hands-on activity to explore the pH-responsive characteristics of hydrogels using a commercially available ionic soft contact lens that is a hydrogel of poly(2-hydroxyethyl methacrylate-"co"-methacrylic…

  5. A retrospective analysis of vision correction and safety in keratoconus patients wearing Toris K soft contact lenses.

    Science.gov (United States)

    Sultan, Pinar; Dogan, Cezmi; Iskeleli, Guzin

    2016-12-01

    The purpose of this study was to investigate the efficacy and safety of the Toris K silicone hydrogel contact lens (SwissLens; Prilly, Switzerland) in keratoconus patients. A database with information on 50 keratoconus patients (64 eyes) fitted with Toris K soft contact lenses over a 2-year period was retrospectively reviewed. Demographic data, prefitting refraction, the reason for choosing the Toris K soft contact lens, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), best-corrected visual acuity with a rigid gas permeable lens (BCVA RGP), best-corrected visual acuity with the Toris K lens (BCVA Toris K), and complications were evaluated. The mean age ± standard deviation at the time of fitting was 27.92 ± 9.86 years. The mean spherical refractive power was -4.62 ± 6.53 dioptres, and the mean cylinder was -3.78 ± 2.43 dioptres. The most common reason for using Toris K soft contact lenses was an inability to fit the patient with a RGP contact lens. There was a statistically significant difference between UCVA and BCVA Toris K (p = 0.0001), as well as between BSCVA and BCVA Toris K (p = 0.0001). However, there was no statistically significant difference between BCVA Toris K and BCVA RGP (p = 0.20). Superficial punctate keratitis and giant papillary conjunctivitis were the most common complications. The Toris K contact lens is a viable alternative for the optical management of all grades of keratoconus. The Toris K soft contact lens is a promising alternative for the visual rehabilitation of keratoconus patients who cannot tolerate RGP lenses or achieve a good fit.

  6. Engineering interfacial properties of organic semiconductors through soft-contact lamination and surface functionalization

    Science.gov (United States)

    Shu, Andrew Leo

    Organic electronics is a topic of interest due to its potential for low temperature and solution processing for large area and flexible applications. Examples of organic electronic devices are already available on the market; however these are, in general, still rather expensive. In order to fully realize inexpensive and efficient organic electronics, the properties of organic films need to be understood and strategies developed to take advantage of these properties to improve device performance. This work focuses on two strategies that can be used to control charge transport at interfaces with active organic semiconducting thin films. These strategies are studied and verified with a range of photoemission spectroscopy, surface probe microscopy, and electrical measurements. Vacuum evaporated molecular organic devices have long used layer stacking of different materials as a method of dividing roles in a device and modifying energy level alignment to improve device performance and efficiency. Applying this type of architecture for solution-processed devices, on the other hand, is nontrivial, as an issue of removal of or mixing with underlying layers arises. We present and examine here soft-contact lamination as a viable technique for depositing solution-processed multilayer structures. The energetics at homojunctions of a couple of air-stable polymers is investigated. Charge transport is then compared between a two-layer film and a single-layer film of equivalent thicknesses. The interface formed by soft-contact lamination is found to be transparent with respect to electronic charge carriers. We also propose a technique for modifying electronic level alignment at active organic-organic heterojunctions using dipolar self-assembled monolayers (SAM). An ultra-thin metal oxide is first deposited via a gentle low temperature chemical vapor deposition as an adhesion layer for the SAM. The deposition is shown to be successful for a variety of organic films. A series of

  7. Using Design of Experiments Methods for Assessing Peak Contact Pressure to Material Properties of Soft Tissue in Human Knee

    Directory of Open Access Journals (Sweden)

    Marjan Bahraminasab

    2013-01-01

    Full Text Available Contact pressure in the knee joint is a key element in the mechanisms of knee pain and osteoarthritis. Assessing the contact pressure in tibiofemoral joint is a challenging mechanical problem due to uncertainty in material properties. In this study, a sensitivity analysis of tibiofemoral peak contact pressure to the material properties of the soft tissue was carried out through fractional factorial and Box-Behnken designs. The cartilage was modeled as linear elastic material, and in addition to its elastic modulus, interaction effects of soft tissue material properties were added compared to previous research. The results indicated that elastic modulus of the cartilage is the most effective factor. Interaction effects of axial/radial modulus with elastic modulus of cartilage, circumferential and axial/radial moduli of meniscus were other influential factors. Furthermore this study showed how design of experiment methods can help designers to reduce the number of finite element analyses and to better interpret the results.

  8. Endoluminal non-contact soft tissue ablation using fiber-based Er:YAG laser delivery

    Science.gov (United States)

    Kundrat, Dennis; Fuchs, Alexander; Schoob, Andreas; Kahrs, Lüder A.; Ortmaier, Tobias

    2016-03-01

    The introduction of Er:YAG lasers for soft and hard tissue ablation has proven promising results over the last decades due to strong absorption at 2.94 μm wavelength by water molecules. An extension to endoluminal applications demands laser delivery without mirror arms due to dimensional constraints. Therefore, fiber-based solutions are advanced to provide exible access while keeping space requirements to a minimum. Conventional fiber-based treatments aim at laser-tissue interactions in contact mode. However, this procedure is associated with disadvantages such as advancing decrease in power delivery due to particle coverage of the fiber tip, tissue carbonization, and obstructed observation of the ablation progress. The objective of this work is to overcome aforementioned limitations with a customized fiber-based module for non-contact robot-assisted endoluminal surgery and its associated experimental evaluation. Up to the authors knowledge, this approach has not been presented in the context of laser surgery at 2.94 μm wavelength. The preliminary system design is composed of a 3D Er:YAG laser processing unit enabling automatic laser to fiber coupling, a GeO2 solid core fiber, and a customized module combining collimation and focusing unit (focal length of 20 mm, outer diameter of 8 mm). The performance is evaluated with studies on tissue substitutes (agar-agar) as well as porcine samples that are analysed by optical coherence tomography measurements. Cuts (depths up to 3mm) with minimal carbonization have been achieved under adequate moistening and sample movement (1.5mms-1). Furthermore, an early cadaver study is presented. Future work aims at module miniaturization and integration into an endoluminal robot for scanning and focus adaptation.

  9. Comparison of fitting stability of the different soft toric contact lenses.

    Science.gov (United States)

    Momeni-Moghaddam, Hamed; Naroo, Shehzad A; Askarizadeh, Farshad; Tahmasebi, Fatemeh

    2014-10-01

    To compare lens orientation and rotational recovery of five currently available soft toric lenses. Twenty subjects were recruited and trialed with each of the study lenses in a random order. Study lenses were PureVision(®) Toric (B&L), Air Optix(®) for Astigmatism (Alcon), Biofinity(®) Toric (CooperVision), Acuvue(®) Advance for Astigmatism (Vistakon), and Proclear(®) Toric (CooperVision). Lens orientation in primary position to determine the lens rotation form the vertical position and rotational recovery to primary gaze orientation following a 45° manual misorientation for the different lenses was compared. The Biofinity Toric showed the lowest rotation from the vertical position and the Proclear Toric the highest. Also, the highest and the lowest reorientation speed were related to the Biofinity Toric and the Acuvue Advance for Astigmatism, respectively. The Repeated Measures ANOVA showed a significant difference in the lens rotation (P=0.004) and rotational recovery (P<0.001) among different contact lenses and the performed multiple comparisons indicated differences in rotation and also in reorientation speed were only seen between the Biofinity Toric when compared to four other lenses (P<0.05). Although there was appropriate fitting, based upon lens orientation and reorientation speed, with each of the study lenses it would appear that the optimized ballast technique used in the design of the Biofinity Toric helps reduce lens rotation and improve rotational recovery compared to others. Copyright © 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  10. Visual Performance and Optical Quality of Standardized Asymmetric Soft Contact Lenses in Patients With Keratoconus.

    Science.gov (United States)

    Suzaki, Asaki; Maeda, Naoyuki; Fuchihata, Mutsumi; Koh, Shizuka; Nishida, Kohji; Fujikado, Takashi

    2017-06-01

    To evaluate the visual performance and optical quality of a standardized asymmetric soft contact lens (SCL) used for correction of higher-order aberrations (HOAs) in eyes with keratoconus. We included 30 eyes (26 patients) with keratoconus (average K: 45.7 ± 2.3 diopters [D]). The patients were subjected to corneal tomography, aberrometry, measurements of manifest refraction and visual acuity (VA), and visual analog scale (VAS) assessments. The study lenses were made using a molding method and consisted of six standardized types, in which an asymmetric power distribution of approximately 2 to 12 D (2-D step) was used to correct HOAs. The lens type suitable for each eye was selected based on the corneal tomography and aberrometry data. The on-eye performance of the lens was evaluated using aberrometry (4-mm pupil), over refraction, VA, and VAS. The standardized asymmetric SCL improved the best spectacle-corrected VA from -0.07 ± 0.09 to -0.11 ± 0.08 logMAR (P keratoconus who wear rigid gas-permeable lenses.

  11. EFFECT OF SHORT-TERM SOFT CONTACT LENS WEAR ON HUMAN OCULAR ABERRATIONS

    Institute of Scientific and Technical Information of China (English)

    YU Jing; CHEN Yi-hui; CHEN Hui; SHENG Min-jie

    2009-01-01

    Objective To evaluate the effect of short-term soft contact lens (SCLs) wearing on human ocular aberrations (HOA).Methods This prospective study included 50 eyes of 50 young volunteers wearing SCLs for 1month. The ocular aberrations were measured by Allegretto Wavefront Analyzer. The root-mean-square (RMS) values of the general (RMSG), higher-order (RMSH), first to sixth order (RMS1 to RMS6) and aberration coefficients were analyzed.Results There were no significant differences in the mean values of RMSG, RMSH, RMS1 to RMS6 (P>0.05) and changes of absolute values of aberration coefficients between baseline and various visits after SCLs discontinuation. However, at d1 after the discontinuation of SCLs, changes in coefficient values of the third-order aberrations (C6 to C9) were slightly higher than others, and C7 was the highest. The increase factors of RMS values were higher at 1 week and lower at the 2 week visit after SCLs discontinuation. The uniformity of dominating type in HOA and the corneal topography form was both about 60% after discontinuation of SCLs. The corneal thickness increased after SCLs wear and gradually decreased to baseline until 1month discontinuation of SCLs.Conclusion The effect of short-term SCLs wear on human ocular aberrations is slight but profound. A month or more wait should be allowed before the short-term SCLs wearers are scheduled for wavefronted-guided LASIK.

  12. Drug release from liposome coated hydrogels for soft contact lenses: the blinking and temperature effect.

    Science.gov (United States)

    Paradiso, P; Colaço, R; Mata, J L G; Krastev, R; Saramago, B; Serro, A P

    2016-05-18

    In this article, liposome-based coatings aiming to control drug release from therapeutic soft contact lenses (SCLs) materials are analyzed. A PHEMA based hydrogel material loaded with levofloxacin is used as model system for this research. The coatings are formed by polyelectrolyte layers containing liposomes of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and DMPC + cholesterol (DMPC + CHOL). The effect of friction and temperature on the drug release is investigated. The aim of the friction tests is to simulate the blinking of the eyelid in order to verify if the SCLs materials coated with liposomes are able to keep their properties, in particular the drug release ability. It was observed that under the study conditions, friction did not affect significantly the drug release from the liposome coated PHEMA material. In contrast, increasing the temperature of release leads to an increase of the drug diffusion rate through the hydrogel. This phenomenon is recorded both in the control and in the coated samples. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2016.

  13. In-situ visualization of N2 evolution in operating direct hydrazine hydrate fuel cell by soft X-ray radiography

    Science.gov (United States)

    Sakamoto, Tomokazu; Deevanhxay, Phengxay; Asazawa, Koichiro; Tsushima, Shohji; Hirai, Shuichiro; Tanaka, Hirohisa

    2014-04-01

    Soft X-ray radiography technique was firstly applied to operating direct hydrazine hydrate fuel cell (DHFCs) in order to visualize N2 gas behaviors with high spatial and temporal resolution. Two different cells for in-situ visualization of N2 gas in the DHFCs in in-plane and through-plane direction were designed and fabricated. The utilization of soft X-ray made the visualization of generated N2 behavior in the DHFC possible with the spatial resolution of 1.5 μm and the temporal resolution of 2.0 s frame-1. In the in-plane visualization, the inhomogeneous N2 gas distribution, suggesting non-uniform reaction distribution in the anode of DHFC, was observed. In the through-plane visualization, N2 gas accumulation under the rib of anode and discharge to the channel was clearly observed, which are related with cell performance instability.

  14. The effect of tinted soft contact lens wear on functional visual acuity and higher-order aberrations.

    Science.gov (United States)

    Watanabe, Kazuhiro; Kaido, Minako; Ishida, Reiko; Dogru, Murat; Negishi, Kazuno; Tsubota, Kazuo

    2014-06-01

    To investigate the differences of functional visual acuity (FVA) and high order aberrations (HOAs) in relation to tinted and clear hydrogel soft contact lens (SCL) wear. A prospective comparative study was performed in 16 eyes of 16 healthy volunteers. Dynamic visual acuity (using a FVA measurement system) and higher-order aberrations (using a wavefront sensor) were compared in subjects wearing two types of soft contact lenses: 1-day Acuvue(®) (Vistakon, Jacksonville, FL) clear and the 1-day Acuvue(®) Define(TM) (Vistakon, Jacksonville, FL) tinted lens. The blink rates were recorded during FVA testing. The correlation between the difference of HOAs and differences in FVA values was analyzed. The mean LogMAR FVA scores with clear and tinted SCLs were 0.07 ± 0.13 and 0.14 ± 0.17 (P<0.05). The mean blink frequencies with clear and tinted SCL wear were 18.4 ± 8.3 and 25.3 ± 4.7 blinks/min (P<0.05). Both 3rd-order aberrations and total HOAs showed statistically significant differences between the two types of soft contact lenses for 6mm pupil measurements (P<0.05). A significant positive linear correlation was observed between ΔHOAs and ΔLogMAR FVA for 6mm pupil measurements (R=0.53, P=0.04). Tinted contact lens wear appears to induce a reduction in optical quality. Functional visual acuity measurement is a useful procedure to study the changes of visual performance and quality in tinted contact lens wear. Copyright © 2013 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  15. A soft-contact and wrench based approach to study grasp planning and execution.

    Science.gov (United States)

    Singh, Tarkeshwar; Ambike, Satyajit

    2015-11-01

    Grasping research in robotics has made remarkable progress in the last three decades and sophisticated computational tools are now available for planning robotic grasping in complex environments. However, studying the neural control of prehension in humans is more complex than studying robotic grasping. The elaborate musculoskeletal geometries and complex neural inputs to the hand facilitate a symphonic interplay of power and precision that allows humans to grasp fragile objects in a stable way without either crushing or dropping them. Most prehension studies have focused on a planar simplification of prehension since planar analyses render the complex problem of prehension tractable with few variables. The caveat is that planar simplification allows researchers to ask only a limited set of questions. In fact, one of the problems with extending prehension studies to three dimensions is the lack of analytical tools for quantifying features of spatial prehension. The current paper provides a theoretical adaptation and a step-by-step implementation of a widely used soft-contact wrench model for spatial human prehension. We propose two indices, grasp caliber and grasp intensity, to quantitatively relate digit placement and digit forces to grasp stability. Grasp caliber is the smallest singular value of the grasp matrix and it indicates the proximity of the current grasp configuration to instability. Grasp intensity is the magnitude of the excessive wrench applied by the digits to counter perturbations. Apart from quantifying stability of spatial grasps, these indices can also be applied to investigate sensory-motor coupling and the role of perception in grasp planning.

  16. Demodex sp. as a Potential Cause of the Abandonment of Soft Contact Lenses by Their Existing Users

    Directory of Open Access Journals (Sweden)

    Witold Tarkowski

    2015-01-01

    Full Text Available Demodex mites may be a potential etiological factor in the development of various eye and skin disorders. The aim of the study was to investigate the presence of Demodex in the hair follicles of eyelashes and their potential influence on abandoning soft contact lenses which had been previously well tolerated by their users. A group of 62 users of contact lenses (28 with emerging discomfort and 34 without discomfort were examined. There is a need to check the existence of a relationship between D. folliculorum or/and D. brevis infestation and the emergence of intolerance to the presence of soft contact lenses. The removed lashes were examined under light microscopy, applying standard parasitological methods if demodicosis is suspected. A positive result was assumed if at least one adult stage, larva, protonymph/nymph, or egg of D. folliculorum and/or D. brevis was present. A positive correlation was observed between the presence of Demodex and intolerance to contact lenses by their existing users p<0.05, and Demodex sp. infections were observed in 92.86% of patients with intolerance to contact lenses. Our results provide further evidence for the pathogenic role played by the mites in the development of eye diseases.

  17. Demodex sp. as a Potential Cause of the Abandonment of Soft Contact Lenses by Their Existing Users.

    Science.gov (United States)

    Tarkowski, Witold; Moneta-Wielgoś, Joanna; Młocicki, Daniel

    2015-01-01

    Demodex mites may be a potential etiological factor in the development of various eye and skin disorders. The aim of the study was to investigate the presence of Demodex in the hair follicles of eyelashes and their potential influence on abandoning soft contact lenses which had been previously well tolerated by their users. A group of 62 users of contact lenses (28 with emerging discomfort and 34 without discomfort) were examined. There is a need to check the existence of a relationship between D. folliculorum or/and D. brevis infestation and the emergence of intolerance to the presence of soft contact lenses. The removed lashes were examined under light microscopy, applying standard parasitological methods if demodicosis is suspected. A positive result was assumed if at least one adult stage, larva, protonymph/nymph, or egg of D. folliculorum and/or D. brevis was present. A positive correlation was observed between the presence of Demodex and intolerance to contact lenses by their existing users (p Demodex sp. infections were observed in 92.86% of patients with intolerance to contact lenses. Our results provide further evidence for the pathogenic role played by the mites in the development of eye diseases.

  18. Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

    Science.gov (United States)

    Ambroziński, Łukasz; Pelivanov, Ivan; Song, Shaozhen; Yoon, Soon Joon; Li, David; Gao, Liang; Shen, Tueng T.; Wang, Ruikang K.; O'Donnell, Matthew

    2016-07-01

    A non-contact method for efficient, non-invasive excitation of mechanical waves in soft media is proposed, in which we focus an ultrasound (US) signal through air onto the surface of a medium under study. The US wave reflected from the air/medium interface provides radiation force to the medium surface that launches a transient mechanical wave in the transverse (lateral) direction. The type of mechanical wave is determined by boundary conditions. To prove this concept, a home-made 1 MHz piezo-ceramic transducer with a matching layer to air sends a chirped US signal centered at 1 MHz to a 1.6 mm thick gelatin phantom mimicking soft biological tissue. A phase-sensitive (PhS)-optical coherence tomography system is used to track/image the mechanical wave. The reconstructed transient displacement of the mechanical wave in space and time demonstrates highly efficient generation, thus offering great promise for non-contact, non-invasive characterization of soft media, in general, and for elasticity measurements in delicate soft tissues and organs in bio-medicine, in particular.

  19. Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

    Energy Technology Data Exchange (ETDEWEB)

    Ambroziński, Łukasz [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); AGH University of Science and Technology, Krakow 30059 (Poland); Pelivanov, Ivan, E-mail: ivanp3@uw.edu [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Faculty of Physics, Moscow State University, Moscow 119991 (Russian Federation); Song, Shaozhen; Yoon, Soon Joon; Gao, Liang; O' Donnell, Matthew [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Li, David [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Department of Chemical Engineering, University of Washington Seattle, Washington 98195 (United States); Shen, Tueng T.; Wang, Ruikang K. [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Department of Ophthalmology, University of Washington, Seattle, Washington 98104 (United States)

    2016-07-25

    A non-contact method for efficient, non-invasive excitation of mechanical waves in soft media is proposed, in which we focus an ultrasound (US) signal through air onto the surface of a medium under study. The US wave reflected from the air/medium interface provides radiation force to the medium surface that launches a transient mechanical wave in the transverse (lateral) direction. The type of mechanical wave is determined by boundary conditions. To prove this concept, a home-made 1 MHz piezo-ceramic transducer with a matching layer to air sends a chirped US signal centered at 1 MHz to a 1.6 mm thick gelatin phantom mimicking soft biological tissue. A phase-sensitive (PhS)-optical coherence tomography system is used to track/image the mechanical wave. The reconstructed transient displacement of the mechanical wave in space and time demonstrates highly efficient generation, thus offering great promise for non-contact, non-invasive characterization of soft media, in general, and for elasticity measurements in delicate soft tissues and organs in bio-medicine, in particular.

  20. The Influence of Soft Contact Lens Wear and Two Weeks Cessation of Lens Wear on Corneal Curvature

    OpenAIRE

    Lloyd McKernan, Aoife; O'Dwyer, Veronica; Simo Mannion, Luisa

    2014-01-01

    Abstract Introduction Accurate corneal measurements are crucial in corneal refractive surgery (CRS) to ensure successful outcomes. Soft contact lens (SCL) wear may result in changes to corneal curvature and structure. United States Food and Drug Administration (FDA) pre-operative guidelines recommend that prior to CRS, SCL wearers cease SCL wear for “at least two weeks before examination and treatment”[1]. Corneal curvature changes induced by SCL wear may take longer than two weeks to reso...

  1. Wearable smart sensor systems integrated on soft contact lenses for wireless ocular diagnostics

    Science.gov (United States)

    Kim, Joohee; Kim, Minji; Lee, Mi-Sun; Kim, Kukjoo; Ji, Sangyoon; Kim, Yun-Tae; Park, Jihun; Na, Kyungmin; Bae, Kwi-Hyun; Kyun Kim, Hong; Bien, Franklin; Young Lee, Chang; Park, Jang-Ung

    2017-04-01

    Wearable contact lenses which can monitor physiological parameters have attracted substantial interests due to the capability of direct detection of biomarkers contained in body fluids. However, previously reported contact lens sensors can only monitor a single analyte at a time. Furthermore, such ocular contact lenses generally obstruct the field of vision of the subject. Here, we developed a multifunctional contact lens sensor that alleviates some of these limitations since it was developed on an actual ocular contact lens. It was also designed to monitor glucose within tears, as well as intraocular pressure using the resistance and capacitance of the electronic device. Furthermore, in-vivo and in-vitro tests using a live rabbit and bovine eyeball demonstrated its reliable operation. Our developed contact lens sensor can measure the glucose level in tear fluid and intraocular pressure simultaneously but yet independently based on different electrical responses.

  2. [Study of the surface tear tension and evaluation of its importance for the retinal physiology and pathology in contact correction and in adaptation to soft contact lenses].

    Science.gov (United States)

    Cherepnin, A I; Smoliakova, G P; Sorokin, E L

    2003-01-01

    The surface lachrymal-fluid (LF) tension was investigated by teardrop dissection in 115 patients with myopia before they were prescribed soft contact lenses (SCL). Such tension was found to be of clinical importance for the development of SCL adaptation disorders. A longer adaptation period in patients with myopia was associated with a low surface LF tension. A high surface LF tension concurrent with the teardrop dissection mode of the destruction type was typical of the pathological nature of SCL adaptation (12.1% of patients). The obtained data are needed to detect timely the risk of dysadaptation disorders and corneal complications before SCL prescription for the purpose of undertaking the pathogenetically substantiated medication to prevent such complications.

  3. Contact ion pair formation between hard acids and soft bases in aqueous solutions observed with 2DIR spectroscopy.

    Science.gov (United States)

    Sun, Zheng; Zhang, Wenkai; Ji, Minbiao; Hartsock, Robert; Gaffney, Kelly J

    2013-12-12

    The interaction of charged species in aqueous solution has important implications for chemical, biological, and environmental processes. We have used 2DIR spectroscopy to study the equilibrium dynamics of thiocyanate chemical exchange between free ion (NCS(-)) and contact ion pair configurations (MNCS(+)), where M(2+) = Mg(2+) or Ca(2+). Detailed studies of the influence of anion concentration and anion speciation show that the chemical exchange observed with the 2DIR measurements results from NCS(-) exchanging with other anion species in the first solvation shell surrounding Mg(2+) or Ca(2+). The presence of chemical exchange in the 2DIR spectra provides an indirect, but robust, determinant of contact ion pair formation. We observe preferential contact ion pair formation between soft Lewis base anions and hard Lewis acid cations. This observation cannot be easily reconciled with Pearson's acid-base concept or Collins' Law of Matching Water Affinities. The anions that form contact ion pairs also correspond to the ions with an affinity for water and protein surfaces, so similar physical and chemical properties may control these distinct phenomena.

  4. Effect of Structure Parameters on Power and Magnetic Field in Electromagnetic Soft-Contact Continuous Casting System

    Institute of Scientific and Technical Information of China (English)

    DENG An-yuan; WANG En-gang; HE Ji-cheng

    2008-01-01

    To design a power source system and mold for electromagnetic soft-contact continuous casting process and to theoretically estimate the heat losses from the charges and the system power, the effect of structure parameters on system power and magnetic flux density distribution was calculated using finite element method. The results show that as for electromagnetic soft-contact continuous casting system with partial-segment type mold, the power consumption is much more than that with a full-segment type mold; about 62% of electric power is dissipated in the mold, and the effective acting range of magnetic field is relatively narrow. Optimizing mold structure is a crucial measure of remarkably reducing mold power consumption and saving electric energy. Increasing slit number, width, and length can remarkably increase the magnetic flux density in the mold and can reduce the electric energy consumption. Among structure parameters, slit number and slit width are relatively more effective to reduce energy consumption. For a round billet electromagnetic continuous casting system with diameter of 178 mm, the reasonable slit number, width, and length are about 24-32, 0.5-1.0 mm, and 160 mm, respectively.

  5. Influence of the metallic contact in extreme-ultraviolet and soft x-ray diamond based Schottky photodiodes

    Science.gov (United States)

    Ciancaglioni, I.; Di Venanzio, C.; Marinelli, Marco; Milani, E.; Prestopino, G.; Verona, C.; Verona-Rinati, G.; Angelone, M.; Pillon, M.; Tartoni, N.

    2011-09-01

    X-ray and UV photovoltaic Schottky photodiodes based on single crystal diamond were recently developed at Rome "Tor Vergata" University laboratories. In this work, different rectifying metallic contact materials were thermally evaporated on the oxidized surface of intrinsic single crystal diamond grown by chemical vapor deposition. Their impact on the detection performance in the extreme UV and soft x-ray spectral regions was studied. The electrical characterization of the metal/diamond Schottky junctions was performed at room temperature by measuring the capacitance-voltage characteristics. The diamond photodiodes were then tested both over the extreme UV spectral region from 10 to 60 eV by using He-Ne DC gas discharge as a radiation source and toroidal vacuum monochromator, and in the soft x-ray range from 6 to 20 keV at the Diamond Light Source synchrotron x-ray beam-line in Harwell (UK). In both experimental setups, time response and spectral responsivity were analyzed for all the investigated Schottky contact materials. A good agreement between the experimental data and theoretical results from Monte Carlo simulations is found

  6. The role of Serratia marcescens in soft contact lens associated ocular infections. A review.

    Science.gov (United States)

    Parment, P A

    1997-02-01

    Serratia marcescens is a Gram negative rod which for a century and a half was considered a harmless saphrophyte. However, medical technology and the use of antibacterial agents have created ecological niches for this bacterium, which is now a medical problem. The bacterium is encountered in connection with contact lens keratitis, often associated with contaminated contact lens solutions. The concentrations of chlorhexidin and thiomersal required in contact lens solution to suppress the bacterium have been proved toxic to the eye. Modern contact lens solutions with biguanids have rapid killing kinetics, while in solutions with polyquaternium S. marcescens can survive in reduced numbers for up to 72 hours. The adherence of a specific isolate of Serratia to hydrogel lenses increased with decreased water content of the lenses. However, there has been no correlation between hydrophobicity markers or hemagglutinins and adherence to contact lenses or urinary tract epithelium. When handling medical plastic devices, such as contact lenses, strictly enforced hygiene remains the most important method to combat environmental bacteria such as Serratia marcescens.

  7. Comparison of fitting stability of the different soft toric contact lenses

    OpenAIRE

    Momeni-Moghaddam, Hamed; Naroo, Shehzad A; Askarizadeh, Farshad; Tahmasebi, Fatemeh

    2014-01-01

    Purpose: To compare lens orientation and rotational recovery of five currently available soft toric lenses. Methods: Twenty subjects were recruited and trialed with each of the study lenses in a random order. Study lenses were PureVision® Toric (B&L), Air Optix® for Astigmatism (Alcon), Biofinity® Toric (CooperVision), Acuvue® Advance for Astigmatism (Vistakon), and Proclear® Toric (CooperVision). Lens orientation in primary position to determine the lens rotation form the vertical position a...

  8. A Management Dilemma: Infectious Keratitis Associated with Soft Contact Lens Use and Dubious Treatment Compliance

    Directory of Open Access Journals (Sweden)

    Konstantinos T. Tsaousis

    2010-01-01

    Full Text Available Purpose. To present a case of infectious keratitis caused by the microorganism Serratia marcescens in a contact lens user and further to confer on the most advantageous management of comparable situations. Case. After altering the routine that she used for contact lens disinfection, a 24-year-old patient presented with pain and conjunctival redness in both eyes. Slit-lamp examination revealed two infiltrates in the inferior part of the cornea in the right eye and five smaller infiltrates in the superior half of the left cornea. Appropriate treatment, after hospitalization, improved the symptoms while culture of the contact lens material revealed Serratia marcescens as the responsible infectious factor. Conclusion. Enhancing the availability of information with respect to contact lens users and customized analysis regarding treatment for a particular complication could be beneficial in order to reduce the frequency of admission to the eye clinic due to infectious keratitis. In addition, rapid laboratory testing of the infected materials should be a priority for selection of the optimal treatment regimen.

  9. Wear of soft tool materials in sliding contact with zinc coated steel sheet

    NARCIS (Netherlands)

    Heide, van der E.; Burlat, M.; Bolt, P.J.; Schipper, D.J.

    2003-01-01

    In order to reduce costs of tooling for press operations, efforts are made to use alternative tool materials like wood or plastic. Friction and wear characteristics in sliding contact with zinc-coated steel sheet could, however, limit the applicability of these tool materials for automotive applicat

  10. Effect of low-addition soft contact lenses with decentered optical design on myopia progression in children: a pilot study

    Directory of Open Access Journals (Sweden)

    Fujikado T

    2014-09-01

    Full Text Available Takashi Fujikado,1 Sayuri Ninomiya,2 Takuma Kobayashi,2 Asaki Suzaki,3 Mitsuhiko Nakada,3 Kohji Nishida4 1Department of Applied Visual Science, Osaka University Graduate School of Medicine, Suita, 2Itami Chuo Eye Clinic, Itami, 3Menicon, Nagoya, 4Department of Ophthalmology, Osaka University Graduate School of Medicine, Suita, Japan Purpose: To investigate the effect of low-addition soft contact lenses (CLs with decentered optical design on the progression of myopia in children in a pilot study.Subjects and methods: Twenty-four Japanese children age 10–16 years with baseline myopia of –0.75 to –3.50 D sphere and ≤1.00 D cylinder were studied. The new CLs were designed to have a nasal decentration with the optical center centered on the line of sight, and with progressive-addition power of +0.5 D peripherally. Monofocal soft CLs were used as controls. A pair of new CLs or control CLs was randomly assigned to the children, and they wore the lenses for 12 months during the first phase. Then, the type of CLs was changed, ie, a crossover design, and the children were observed for another 12 months during the second phase. The end points were changes in axial length and refractive error (spherical equivalent under cycloplegia.Results: The change of axial length in the new-CL and control-CL groups was not different between 12 months and baseline, the change of axial length between 12 months and 1 month in the new-CL group (0.09±0.08 mm was significantly smaller (47% than that in the control-CL group (0.17±0.08 mm, P<0.05. During the same period, the change of refractive error in the new-CL group was not significantly different from that in the control group. Neither the change in axial length nor refractive error in the new-CL group was significantly different from those in the control-CL group in the second phase.Conclusion: This pilot study suggests that low-addition soft CLs with decentered optical design can reduce the degree of axial

  11. Nucleus and cell size changes in human bulbar conjunctival cells after soft contact lens wear, as assessed by impression cytology.

    Science.gov (United States)

    Doughty, Michael J; Naase, Taher

    2008-06-01

    To specifically assess the nucleus size and its relationship to cell size for human bulbar conjunctival cells. Impression cytology samples were taken from the nasal side of the intra-palpebral zone of the bulbar conjunctival surface from 20 young adult white European males, half of whom were successful daily soft contact lens wearers. A Millcell-CM filter was used, after topical anaesthesia with oxybuprocaine 0.4%, which was stained with Giemsa and colour images taken at 400x magnification by light microscopy. The images were graded and also a 35mm was prepared. From the projected image, an overlay method was used to outline the borders such that the cell and nucleus areas could be measured by planimetry. The group mean cell area values were 267+/-59microm(2) (n=10, +/-S.D.) and 1028+/-357microm(2) for the non-contact lens wearers and contact lens wearers, respectively. The cell nucleus areas were 64+/-11microm(2) and 99+/-19microm(2), respectively. Both the cell areas and nucleus area values were statistically different between the two groups (pnucleus-to-cytoplasm ratio also changes, but the nucleus size generally increases (rather than decreases).

  12. Surfactant-laden soft contact lenses for extended delivery of ophthalmic drugs.

    Science.gov (United States)

    Kapoor, Yash; Thomas, Justin C; Tan, Grace; John, Vijay T; Chauhan, Anuj

    2009-02-01

    Eye drops are inefficient means of delivering ophthalmic drugs because of limited bioavailability and these can cause significant side effects due to systemic uptake of the drug. The bioavailability for ophthalmic drugs can be increased significantly by using contact lenses. This study focuses on the development of surfactant-laden poly-hydroxy ethyl methacrylate (p-HEMA) contact lenses that can release Cyclosporine A (CyA) at a controlled rate for extended periods of time. We focus on various Brij surfactants to investigate the effects of chain length and the presence of an unsaturated group on the drug release dynamics and partitioning inside the surfactant domains inside the gel. The gels were imaged by cryogenic scanning electron microscopy (cryo-SEM) to obtain direct evidence of the presence of surfactant aggregates in the gel, and to investigate the detailed microstructure for different surfactants. The images show a distribution of nano pores inside the surfactant-laden hydrogels which we speculate are regions of surfactant aggregates, possibly vesicles that have a high affinity for the hydrophobic drug molecule. The gels are further characterized by studying their mechanical and physical properties such as transparency, surface contact angle and equilibrium water content to determine their suitability as extended wear contact lenses. Results show that Brij surfactant-laden p-HEMA gels provide extended release of CyA, and possess suitable mechanical and optical properties for contact lens applications. The gels are not as effective for extended release of two other hydrophobic ophthalmic drugs, dexamethasone (DMS) and dexamethasone 21 acetate (DMSA) because of insufficient partitioning inside the surfactant aggregates.

  13. Water soluble drug releasing soft contact lens in response to pH of tears

    Science.gov (United States)

    Kim, G.; Noh, H.

    2016-06-01

    Human tear characteristics including pH and compositions can vary significantly depending on physical and environmental factors. Contact lenses directly contact with human tears can be swelled or de-swelled depending on the pH of the solution due to the nature of the hydrogel. For examples, anionic hydrogels, when the solution's pH is low, is shrunken due to the electric attraction force within the hydrogel network; the opposite phenomenon appears when the solution is basic. The purpose of this study was to evaluate the extent of water soluble drug, hydroxyl propyl methyl cellulose, released from contact lens according to the pH of the artificial tears. Artificial tears are prepared by mixing lysozyme, albumin, sodium chloride, potassium chloride, and calcium chloride following physiological concentrations. Hydrogel contact lens was thermally polymerized using HEMA, EGDMA, and AIBN. The prepared hydrogel lens was immersed in drug for 3 hours and the eluted drug mass was measured as a function of the time. As a result, the drug was released from the lens for 12 hours in all the pH of artificial tears. At the lower pH of artificial tears (pH 5.8), the total amount of dye emitted from the lens was increased than the total amount of dye emitted at the basic tear (pH 8.4). Also, initial burst at acidic tears was increased within 1 hour. Release pattern of water-soluble drug from hydrogel lens turned out to be different depending on the pH of the artificial tears. When designing drug releasing contact lens, physiological pH of tears should be considered.

  14. On the Importance of Displacement History in Soft-Body Contact Models

    Science.gov (United States)

    2015-07-10

    capable of accurately reproducing results from physical tests typical of the field of geomechanics ; i.e., a direct shear tests on a mono-disperse...frictional contact problems in granular flow dynamics and quasi-static geomechanics applications. The so-called Complementarity Method (CM) is...within the geomechan - ics community [4], DEM-PM can be viewed either as a reg- ularization (or smoothing) approach, which relies on a relax- ation of the

  15. Intraocular pressure measurement over soft contact lens by rebound tonometer: a comparative study

    Institute of Scientific and Technical Information of China (English)

    Senay; Asik; Nacaroglu; Emine; Seker; Un; Mehmet; Giray; Ersoz; Yelda; Tasci

    2015-01-01

    AIM: To evaluate the intraocular pressure(IOP)measurements by Icare rebound tonometer over a contact lens in comparison with Goldmann applanation tonometry(GAT). METHODS: Fifty patients using contact lens were included in this study. One of the eyes of the patients was selected randomly and their IOP were measured by rebound tonometer with and without contact lens(RTCL,RT respectively) and by GAT, as well as their central corneal thickness(CCT) by optical pachymeter. The results of both methods were compared by correlation analysis, general linear method repeated measure and Bland-Altman analysis.RESULTS: Mean IOP values measured by RTCL, RT and GAT were 15.68 ±3.7, 14.50 ±3.4 and 14.16 ±2.8(P <0.001), respectively. Mean IOP by RTCL was significantly higher than the measurements implemented by RT and GAT(P <0.001), while there was no difference between the measurements by GAT and RT(P =0.629). There was a good level of positive correlation between GAT and RTCL as well as RT(r =0.786 P <0.001, r =0.833 P <0.001, respectively). We have observed that CCT increase did not show any correlation with the differences of the measurements between RTCL and RT(P =0.329), RTCL and GAT(P =0.07) as well as RT and GAT(P =0.189) in linear regression model.CONCLUSION: The average of the measurements over contact lens by rebound tonometer was found to be higher than what was measured by GAT. Although this difference is statistically significant, it may be clinically negligible in the normal population.

  16. Analytical solution of axisymmetric contact problem about indentation of a circular indenter into a soft functionally graded elastic layer

    Institute of Scientific and Technical Information of China (English)

    Sergey Volkov; Sergey Aizikovich; Yue-Sheng Wang; Igor Fedotov

    2013-01-01

    The paper addresses a contact problem of the theory of elasticity,i.e.,the penetration of a circular indenter with a flat base into a soft functionally graded elastic layer.The elastic properties of a functionally graded layer arbitrarily vary with depth,and the foundation is assumed to be elastic,yet much harder than a layer.Approximated analytical solution is constructed,and it is shown that the solutions are asymptotically exact both for large and small values of characteristic dimensionless geometrical parameter of the problem.Numerical examples are analyzed for the cases of monotonic and nonmonotonic variations of elastic properties.Numerical results for the case of homogeneous layer are compared with the results for nondeformable foundation.

  17. Adaptação de lente de contato gelatinosa especial para ceratocone Keratoconus special soft contact lens fitting

    Directory of Open Access Journals (Sweden)

    Ester Sakae Yamazaki

    2006-08-01

    Full Text Available OBJETIVO: Relatar a experiência inicial com o uso de lentes de contato gelatinosas especiais para ceratocone. MÉTODOS: Estudo retrospectivo de 80 olhos de 66 pacientes usuários de lentes de contato gelatinosas especial para ceratocone, no Setor de Lentes de Contato da UNIFESP e em clínicas particulares. Os pacientes foram classificados de acordo com o grau de gravidade da doença pela avaliação ceratométrica. Foram coletados os seguintes dados: idade, sexo, diagnóstico, ceratometria, acuidade visual com a lente, equivalente esférico (ES, curvatura da lente e indicação para o seu uso. RESULTADOS: Foram estudados 80 olhos de 66 pacientes usuários de lente gelatinosa para ceratocone. A média de idade foi de 29 anos, sendo 51,5% homens e 48,5% de mulheres. De acordo com os grupos: incipiente: 15,0%, moderado: 53,7%, avançado: 26,3%, grave: 5,0%. A maioria dos olhos estudados (91,25% apresentou acuidade visual melhor que 20/40 com a lente. Foram adaptadas 58% lentes de poder esférico (média de -5,45 dioptrias e 41% lentes com grau esferocilíndrico (variando de -0,50 a -5,00 dioptrias cilíndricas. A curva esférica mais utilizada foi de 7,6 mm (61% dos olhos. As principais razões para a escolha e adaptação desta lente foram devido à intolerância e ao padrão de adaptação insatisfatório com outras lentes. CONCLUSÃO: A lente gelatinosa para ceratocone pode ser usada em casos de difícil adaptação, como uma opção para melhorar o conforto e possibilitar a reabilitação visual em pacientes que não obtiveram alternativas a não ser algum procedimento cirúrgico.PURPOSE: To evaluate the fitting and use of a soft contact lens in keratoconic patients. METHODS: Retrospective study on 80 eyes of 66 patients, fitted with a special soft contact lens for keratoconus, at the Contact Lens Section of UNIFESP and private clinics. Keratoconus was classified according to degrees of disease severity by keratometric pattern. Age, gender

  18. A meta-analysis of studies on cosmetically tinted soft contact lenses

    Directory of Open Access Journals (Sweden)

    Rah MJ

    2013-10-01

    Full Text Available Marjorie J Rah,1 Jeffery Schafer,1 Lening Zhang,1 Osbert Chan,2 Lipika Roy,3 Joseph T Barr11Bausch & Lomb Incorporated, Rochester, NY, USA; 2Bausch & Lomb Incorporated, Asia Pacific Medical Affairs, Hong Kong; 3Bausch & Lomb Incorporated, Asia Pacific Medical Affairs, Singapore, MalaysiaBackground: Concerns regarding the safety of cosmetically tinted contact lenses have been reported in the literature. The purpose of this paper is to evaluate the safety of cosmetically tinted contact lenses in a large number of patients across six clinical trials that varied from 1 week to 3 months in duration.Methods: Lenses tested included: Naturelle limbal ring daily disposable, Lacelle limbal ring daily disposable, Lacelle colored cosmetic daily disposable, Lacelle limbal ring planned replacement at 2 weeks, and Alamode traditional/annual colored cosmetic lens. The primary safety outcome was slit-lamp examination, including epithelial edema, epithelial microcysts, corneal staining, bulbar injection, limbal injection, upper lid tarsal conjunctival abnormalities, corneal neovascularization, and corneal infiltrates. High contrast logMAR visual acuity with lenses, and lens wearing time, movement, and centration, are also presented.Results: A total of 871 subjects (1,742 eyes and 23 clinical investigators participated in the six studies, with an average completion rate of 96.4% across all studies. The mean age of the patients was 26.8 ± 6.6 years, and 86.7% of participants were female. The total number of slit-lamp examinations across the six studies was 2,456 visits by eye (1,228 visits by patient. There were no slit-lamp signs > grade 2 for any finding, with the exception of corneal staining in one study. In this study, grade 3 corneal staining was noted in one eye (0.1% at follow-up visit 1 and four (0.6% of all eligible dispensed eyes at follow-up visit 2, with no eyes requiring medical treatment. No adverse events were reported during any of the trials

  19. The role of water in the molecular structure and properties of soft contact lenses and surface interactions

    Science.gov (United States)

    Monti, Patrizia; Simoni, Rosa

    1992-06-01

    The role played by water in the molecular structure and properties of commercial soft contact lenses (hydrogels) based on poly 2-hydroxyethyl methacrylate (PHEMA) or poly vinylpyrrolidone (PVP) was investigated by means of vibrational spectroscopy and thermal analyses. The results of this study show that the materials having the greatest water percentage have elastic properties closer to those of the ocular tissues with which they come into contact. Water interacts by hydrogen bonding with the hydrophilic groups present in the polymers, and the strength of this interaction depends on the type of hydrophilic group involved. Moreover, in the case of PVP materials, water also modifies the conformation of the hydrophobic groups. The arrangement of surface water molecules can explain the different adhesion capability of Staphilococcus aureus on this type of lens depending on the water content. In connection with this, a simple model is presented. The water molecules present in the hydrogel structures completely exchange with those of the biological environment. A quantitative analytical method for evaluating the amount of water in commercial lenses by means of Raman spectroscopy is reported.

  20. EFFECTS OF PREOPERATIVE SOFT CONTACT LENS WEAR ON HIGHER-ORDER ABERRATIONS AFTER LASER IN SITU KERATOMILEUSIS

    Institute of Scientific and Technical Information of China (English)

    YU Jing; CHEN Hui; CHENG Xin-liang; WANG Fang

    2008-01-01

    Objective To evaluate the effects of preoperative soft contact lens (SCL) wear on higher-order aberrations(HOAs)correction after wavefront-guided and conventional laser in situ keratomileusis (LASIK).Methods A prospective randomized double-masked comparative study was conducted in 180 eyes of 90 patients scheduled for LASIK, including 92 eyes of 46 patients with previous SCL wear. The patients were divided into four groups: no SCL-conventional group, SCL-conventional group, no SCL-wavefront group and SCL-wavefront group. Preoperative and postoperative examinations included uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), contrast sensitivity and HOAs.Results The UCVA and BSCVA were 20/20 in all patients at 6 months postoperatively. And 36.3%, 22.7%, 18.1% and 35.4% gained one line or more of BSCVA in no SCL-wavefront group, SCL-wavefront group, no SCL-conventional group and SCL-conventional group, respectively. Both the safety index and efficacy index surpassed one in 4 groups and were highest in no SCL-wavefront group. The increase in root-mean-square (RMS) values of HOAs was significantly lower in no SCL-wavefront group and higher in SCL-wavefront group. At 6 months postoperatively, the increase in RMS of HOAs (RMSh) were 0.67, 1.58, 1.17 and 1.28 in no SCL-wavefront group, SCL-wavefront group, no SCL-conventional group and SCL-conventional group, respectively.Conclusion Preoperative contact lens wear has significant influence on the efficacy of HOAs correction in wavefront-guided LASIK. Patients with contact lens wear preoperatively should be cautious when scheduled for wavefront-guided LASIK.

  1. Cosmetic Cleansing Oil Absorption by Soft Contact Lenses in Dry and Wet Conditions.

    Science.gov (United States)

    Tsukiyama, Junko; Miyamoto, Yuko; Kodama, Aya; Fukuda, Masahiko; Shimomura, Yoshikazu

    2017-09-01

    Previous reports showed that cosmetic cleansing oil for removing makeup, which contains mineral oil and surfactant, can deform some silicone hydrogel contact lenses (SHCLs) when applied directly to the lenses, although plasma-coated SHCLs (lotrafilcon A and B) were not affected. In the present study, we investigated hydrogel lenses and SHCLs in both wet and dry conditions. Several brands of hydrogel and SHCLs were immersed in a cleansing oil solution containing Sudan Black B for 5 min under wet and dry conditions. The lenses under the wet condition were simply picked up from the saline, whereas those under the dry condition were blotted with paper wipes. After immersing, the excess solution remaining on the lenses was removed by finger rubbing with a multipurpose solution. The lenses were then examined using a stereomicroscope, and their mean brightness was measured and compared. The cosmetic cleansing oil was not absorbed by the hydrogel lenses under wet or dry conditions. However, four of seven brands of SHCLs absorbed the cosmetic cleansing oil under both conditions (dry and wet), whereas asmofilcon A absorbed it only under the dry condition. Lotrafilcon B and delefilcon A did not absorb cleansing oil even under the dry condition. Hydrogel lenses resist cosmetic cleansing oil. However, SHCLs have different degrees of resistance depending on the lens material. Some SHCLs absorbed cosmetic cleansing oil more under dry conditions than under wet conditions.

  2. Efficacy of two-month treatment with Xiloial® eyedrops for discomfort from disposable soft contact lenses

    Directory of Open Access Journals (Sweden)

    Piera Versura

    2010-09-01

    Full Text Available Piera Versura, Vincenzo Profazio, Nicole Balducci, Emilio C CamposOphthalmology Unit, Alma Mater Studiorum University of Bologna, Bologna, ItalyPurpose: To evaluate the efficacy and tolerability of Xiloial® monodose eyedrops in the treatment of patients suffering from subjective symptoms of discomfort related to disposable soft contact lens (dSCL wear.Methods: Fifteen (12 female, three male, medium age 39 ± 9 years dSCL wearers were enrolled. Inclusion criteria were Ocular Surface Disease Index (ODSI symptom questionnaire score >12, tear film break-up time (TFBUT <10 sec, Schirmer test I >10 mm over five minutes, mild punctuate keratopathy, and conjunctival staining (Oxford grading ≤4. Monodose Xiloial eyedrops were administered three times daily for a two-month period. Patients were evaluated at enrollment, after three days of washout (baseline, and after one and two months of treatment, by OSDI score, Schirmer test I, TFBUT, ferning test, ocular surface damage (Oxford grade, and serum albumin in tears (index of passive exudation related to serum leakage.Results: At endpoint versus baseline, respectively, the mean ± standard deviation of all variables improved as follows: OSDI (8.5 ± 3 versus 20.2 ± 1.6; TFBUT (9.6 ± 1.1 versus 7.1 ± 1.0; Oxford grading (0.5 ± 0.1 versus 3.6 ± 0.8; ferning test (2 ± 1 versus 2.4 ± 0.5; and Schirmer test I (14.6 ± 1.1 versus 12 ± 2.1, with P < 0.05 for all variables (Friedman and Wilcoxon tests. Tolerability was high, with no adverse events noted.Conclusions: A two-month treatment with Xiloial showed good tolerance and appeared to reduce ocular surface damage and symptoms of discomfort.Keywords: discomfort, dry eye, disposable contact lens, biopolymer tamarind seed polysaccharide–hyaluronic acid

  3. Micro-bond contact model and its parameters for the deep-sea methane hydrate bearing soils%深海能源土微观力学胶结模型及参数研究

    Institute of Scientific and Technical Information of China (English)

    蒋明镜; 肖俞; 朱方园

    2012-01-01

    天然气水合物主要以胶结物形式存在深海能源土颗粒之间,对能源土强度影响显著,因此研究水合物胶结接触力学特性对能源土力学性质研究有重要作用,而其中的关键是水合物胶结模型及胶结参数的确定。首先,引入并讨论了一种微观胶结接触模型及其对于能源土胶结接触力学特性的适用性;其次,通过文献资料系统分析,获取不同温度、压力及水合物密度条件下天然气水合物的强度与弹性模量表达式;最后,进一步研究了水合物微观胶结模型中的胶结参数,该类水合物微观胶结参数取决于能源土中水合物埋藏深度(赋存环境压力)、温度、水合物密度,这些宏观参量容易确定。%Methane hydrate (MH), which has significant influences on the strength of methane hydrate bearing soils, exits mainly in the form of cement materials between soil particles. Hence, the study of bond mechanical behavior of MH between soil particles is significant to the research of methane hydrate bearing soils, of which the keypoint is the determination of the micro-contact model and corresponding bond parameters of MH. First, a micro-bond contact model is introduced to reflect the contact properties of the soil particles. Second, the strengths and elastic modulus of MH (such as the tensile strength, compressive strength, shear strength and torsion strength) are obtained through the literatures about methane hydrate triaxial tests. Finally, micro bond parameters needed by the contact model are obtained. The results show that the micro bond parameters of gas hydrate are determined by the saturation and strength parameters of gas hydrate, which can be obtained through the temperature, density of hydrate and its burial depth which are easy to be determined.

  4. Visual performance with multifocal soft contact lenses in non-presbyopic myopic eyes during an adaptation period

    Directory of Open Access Journals (Sweden)

    Fedtke C

    2016-04-01

    Full Text Available Cathleen Fedtke,1 Klaus Ehrmann,1,2 Varghese Thomas,1 Ravi C Bakaraju,1,2 1The Brien Holden Vision Institute, Clinical Trial Research Centre, 2School of Optometry and Vision Science, The University of New South Wales, Sydney, NSW, Australia Purpose: Multifocal soft contact lenses (MFCLs have been proposed and used for controlling the rate of myopia progression; however, little is known on the performance and adaptation with MFCLs in non-presbyopes. This study aims to evaluate the visual performance of four commercially available MFCLs in non-presbyopic myopic eyes during an adaptation period. Methods: Fifty-two experienced myopic contact lens wearers (67% female; mean age 21.4±2.0 years were enrolled in this trial and 40 completed the trial. Twenty-six participants (Group 1 wore Lotrafilcon B single vision (SV, control, Omafilcon A MFCL center-distance (D and center-near (N and the other 26 participants (Group 2 wore Lotrafilcon B SV, Lotrafilcon B MFCL N, and Balafilcon A MFCL N. Lens order was randomized. Participants wore each allocated lens for a minimum of 8 days over four scheduled visits (dispensing and three follow-up visits with a 1-week washout period between the lens types. At each visit, high-contrast visual acuity (HCVA (in logarithm of the minimum angle of resolution [logMAR] and seven subjective performance variables (via questionnaire were obtained. Power profiles of each lens type, pupil size, and contact lens centration, with lens placed on the eye, were measured. Results: The SV control outperformed the MFCLs in all variables (P<0.05. There were no significant differences in HCVA over time, with the exception of monocular HCVA with Omafilcon A MFCL N, which at the end of the adaptation period had significantly (P<0.05 improved by 0.10 logMAR. No differences were found between visits for any subjective variables. Subjectively, Lotrafilcon B MFCL N performed best and was the only lens that did not decenter significantly

  5. Storing natural gas as frozen hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Gudmundsson, J.S.; Khokhar, A.A. (Univ. of Trondheim (Norway)); Parlaktuna, M. (Middle East Technical Univ., Ankara (Turkey))

    1994-02-01

    The formation of natural gas hydrates is a well-known problem in the petroleum and natural gas industries. Hydrates are solid materials that form when liquid water and natural gas are brought in contact under pressure. Hydrate formation need not be a problem. On the contrary, it can be an advantage. The volume of hydrates is much less than that of natural gas. At standard conditions, hydrates occupy 150 to 170 times less volume than the corresponding gas. Typically, natural gas hydrates contain 15% gas and 85% water by mass. It follows that hydrates can be used for large-scale storage of natural gas. Benesh proposed using hydrates to improve the load factor of natural gas supply systems. The author suggested that hydrates could be produced by bringing liquid water into contact with natural gas at the appropriate temperature and high pressure. The hydrate then would be stored at a temperature and pressure where it was stable. When gas was needed for the supply system, the hydrate would be melted at low pressure. The stability of a natural gas hydrate during storage at atmospheric pressure and below-freezing temperatures was studied in the laboratory. The gas hydrate was produced in a stirred vessel at 2- to 6-MPa pressure and temperatures from 0 to 20 C. The hydrate was refrigerated and stored in deep freezers at [minus]5, [minus]10, and [minus]18 C for up to 10 days. The natural gas hydrate remained stable when kept frozen at atmospheric pressure.

  6. Clinical Observation of Soft Contact Lens in Corneal Trauma%软性角膜接触镜治疗角膜外伤的临床观察

    Institute of Scientific and Technical Information of China (English)

    张萍

    2015-01-01

    目的:对软性角膜接触镜治疗角膜外伤的临床效果进行观察。方法选取我院2002年1月~2011年1月收治的眼外伤患者52例,对其进行软性角膜接触镜治疗,观察患者的临床治疗效果。结果52例患者中有50例连续戴镜1~12天后伤口基本愈合或愈合,未发生并发症,伤口瘢痕密度低、表面平整。2例患者由于石灰烧伤导致院外角膜接触镜脱失,治疗效果不理想。所有患者在戴镜初期除了不同程度的流泪和异物感之外,没有出现其他不适。结论使用软性角膜接触镜对角膜外伤进行治疗能够起到良好的治疗效果。%Objective To observe the clinical effect of soft contact lens on corneal trauma. Methods 52 patients with eye injury methods in our hospital from 2002 January to 2011 January were selected. Soft corneal contact lens in the treatment of the clinical effect of the treatment of the patients were observed. Results In 52 cases,50 cases healed after continuous wearing mirror 1 to 12 days,no complications,wound scar low density,surface roughness. 2 patient sthat soft contact lens dropout was not ideal due to lime burn. Al patients had no other discomfort in wearing glasses early in addition to tears and foreign body sensation. Conclusion the using soft contact lens on corneal trauma treatment can play a good curative effect.

  7. Ultrastructural imaging and molecular modeling of live bacteria using soft x-ray contact microscopy with nanoseconds laser-plasma radiation

    Science.gov (United States)

    Kado, Masataka; Richardson, Martin C.; Gaebel, Kai; Torres, David S.; Rajyaguru, Jayshree; Muszynski, Michael J.

    1995-09-01

    X-ray images of the various live bacteria, such as Staphylococcus and Streptococcus, and micromolecule such as chromosomal DNA from Escherichis coli, and Lipopolysacchride from Burkholderia cepacia, are obtained with soft x-ray contact microscopy. A compact tabletop type glass laser system is used to produce x-rays from Al, Si, and Au targets. The PMMA photoresists are used to record x-ray images. An AFM (atomic force microscope) is used to reproduce the x-ray images from the developed photoresists. The performance of the 50nm spatial resolutions are achieved and images are able to be discussed on the biological view.

  8. Soft-contact conductive carbon enabling depolarization of LiFePO4 cathodes to enhance both capacity and rate performances of lithium ion batteries

    Science.gov (United States)

    Ren, Wenju; Wang, Kai; Yang, Jinlong; Tan, Rui; Hu, Jiangtao; Guo, Hua; Duan, Yandong; Zheng, Jiaxin; Lin, Yuan; Pan, Feng

    2016-11-01

    Conductive nanocarbons generally are used as the electronic conductive additives to contact with active materials to generate conductive network for electrodes of commercial Li-ion batteries (LIBs). A typical of LiFePO4 (LFP), which has been widely used as cathode material for LIBs with low electronic conductivity, needs higher quantity of conductive nanocarbons to enhance the performance for cathode electrodes. In this work, we systematically studied three types of conductive nanocarbons and related performances in the LFP electrodes, and classify them as hard/soft-contact conductive carbon (named as H/SCC), respectively, according to their crystallite size, surface graphite-defect, specific surface area and porous structure, in which SCC can generate much larger contact area with active nano-particles of cathode materials than that of HCC. It is found that LFP nanocrystals wrapped in SCC networks perform significantly enhanced both capacity and rate performance than that in HCC. Combined experiments with multiphysics simulation, the mechanism is that LFP nanoparticles embedded in SCC with large contact area enable to generate higher depolarized effects with a relatively uniform current density vector (is) and lithium flux vector (NLi) than that in HCC. This discovery will guide us to how to design LIBs by selective using conductive carbon for high-performance LIBs.

  9. Dendritic immune cell densities in the central cornea associated with soft contact lens types and lens care solution types: a pilot study

    Directory of Open Access Journals (Sweden)

    Sindt CW

    2012-03-01

    Full Text Available Christine W Sindt1, Trudy K Grout1, D Brice Critser1, Jami R Kern2, David L Meadows21University of Iowa Hospitals and Clinics, Iowa City, IA; 2Alcon Research Ltd, Fort Worth, TX, USABackground: The purpose of this study was to assess whether differences in central corneal dendritic immune cell densities associated with combinations of soft contact lenses and lens care solutions could be detected by in vivo confocal microscopy.Methods: Participants were adults naïve to contact lens wear (n = 10 or who wore soft contact lenses habitually on a daily-wear schedule (n = 38 or on a study-assigned schedule for 30 days with daily disposable silicone hydrogel lenses (n = 15. Central corneas were scanned using an in vivo confocal microscope. Cell densities were compared among groups by demographic parameters, lens materials, and lens care solutions (polyhexamethylene biguanide [PHMB], polyquaternium-1 and myristamidopropyl dimethylamine [PQ/MAPD], peroxide, or blister pack solution [for daily disposable lenses].Results: Among lens wearers, no associations were observed between immune cell densities and age, gender, or years of lens-wearing experience. Mean cell density was significantly lower (P < 0.01 in nonwearers (29 ± 23 cells/mm2, n = 10 than in lens wearers (64 ± 71 cells/mm2, n = 53. Mean cell density was lower (P = 0.21 with traditional polymer lenses (47 ± 44 cells/mm2, n = 12 than with silicone hydrogel lenses (69 ± 77 cells/mm2, n = 41. Lowest to highest mean density of immune cells among lens wearers was as follows: PQ/MAPD solution (49 ± 28 cells/mm2, blister pack solution (63 ± 81 cells/mm2, PHMB solution (66 ± 44 cells/mm2, and peroxide solution (85 ± 112 cells/mm2.Conclusion: In this pilot study, in vivo confocal microscopy was useful for detecting an elevated immune response associated with soft contact lenses, and for identifying lens-related and solution-related immune responses that merit further research.Keywords: Clear Care

  10. Numerical Simulation of Heat Transfer and Deformation of Initial Shell in Soft Contact Continuous Casting Mold Under High Frequency Electromagnetic Field

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Heat transfer and deformation of initial solidification shell in soft contact continuous casting moldunder high frequency electromagnetic field were analyzed using numerical simulation method; the relative electromagnetic parameters were obtained from the previous studies. Owing to the induction heating of a high frequency electromagnetic field (20 kHz), the thickness of initial solidification shell decreases, and the temperature of strand surface and slit copper mold increases when compared with the case without the electromagnetic filed. The viscosity of flux decreases because of the induction heating of the high frequency electromagnetic field, and the dimension of the flux channel increases with electromagnetic pressure; thus, the deformation behavior of initial solidification shell was different before and after the action of high frequency electromagnetic field. Furthermore, the abatement mechanism of oscillation marks under high frequency electromagnetic field was explained.

  11. A novel type of ultra fast and ultra soft recovery SiGe/Si heterojunction power diode with an ideal ohmic contact

    Institute of Scientific and Technical Information of China (English)

    Ma Li; Gao Yong; Wang Cai-Lin

    2004-01-01

    A novel type of p+ (SiGe)-n--n+ heterojunction switching power diode with high-speed capability is presented to overcome the drawbacks of existing power diodes. The improvement is achieved by using a p+-n+ mosaic layer electrons and holes simultaneously. Compared with conventional p+(SiGe)-n--n+ diodes, the ideal ohmic contact p+ (SiGe)-n--n+ diodes have about one third of the reverse recovery time and a half of peak reverse recovery current.Furthermore, the softness factor increases nearly two times and the leakage current decreases 1-2 orders of magnitude.These improvements are achieved without resorting special process step to lower the carrier lifetime and thus the devices could be easily integrated into power ICs. The Ge percentage content of p+ (SiGe) layer is an important parameter for the optimal device design.

  12. Quantitative Contact Resonance Force Microscopy for Viscoelastic Measurement of Soft Materials at the Solid-Liquid Interface.

    Science.gov (United States)

    Churnside, Allison B; Tung, Ryan C; Killgore, Jason P

    2015-10-13

    Viscoelastic property measurements made at the solid-liquid interface are key to characterizing materials for a variety of biological and industrial applications. Further, nanostructured materials require nanoscale measurements. Here, material loss tangents (tan δ) were extracted from confounding liquid effects in nanoscale contact resonance force microscopy (CR-FM), an atomic force microscope based technique for observing mechanical properties of surfaces. Obtaining reliable CR-FM viscoelastic measurements in liquid is complicated by two effects. First, in liquid, spurious signals arise during cantilever excitation. Second, it is challenging to separate changes to cantilever behavior due to the sample from changes due to environmental damping and added mass effects. We overcame these challenges by applying photothermal cantilever excitation in multiple resonance modes and a predictive model for the hydrodynamic effects. We demonstrated quantitative, nanoscale viscoelastic CR-FM measurements of polymers at the solid-liquid interface. The technique is demonstrated on a point-by-point basis on polymer samples and while imaging in contact mode on a fixed plant cell wall. Values of tan δ for measurements made in water agreed with the values for measurements in air for some experimental conditions on polystyrene and for all examined conditions on polypropylene.

  13. Characterization of protein adsorption on soft contact lenses. IV. Comparison of in vivo spoilage with the in vitro adsorption of tear proteins.

    Science.gov (United States)

    Castillo, E J; Koenig, J L; Anderson, J M

    1986-03-01

    Tear protein and gamma-globulin mixtures were adsorbed on soft contact lenses of different chemical composition, surface quality and water content. The adsorption process was followed by Fourier transform infrared-attenuated total reflectance spectroscopy (ATR-FTIR). It was found that gamma-globulin underwent a conformational and orientational change after its adsorption and the extent of structural change appeared to be proportional to the binding strength of the protein with the hydrogel surface. Electrostatic interactions play a major role in the protein adsorption on lenses containing methacrylic acid. Lysozyme is selectively adsorbed on all of the high water content hydrogels and mucin is the major protein component for the pure PHEMA type of lenses. Studies on in vivo spoiled PHEMA and PVP/MMA lenses indicate that lysozyme is the major adsorbed deposit. Papain cleaning of in vivo spoiled lenses shows that although a portion of the deposits is desorbed, the enzyme itself becomes irreversibly adsorbed to the contact lens which may cause harmful effects to the eye.

  14. Gas hydrates

    Digital Repository Service at National Institute of Oceanography (India)

    Ramprasad, T.

    and the role it plays in the global climate and the future of fuels. Russia, Japan, Nigeria, Peru, Chile, Pakistan, Indonesia, Korea, etc are various countries who are perusing the gas hydrates studies as a future resource for fuel. Indian Initiative..., 1993, Free gas at the base of the gas hydrate zone in the vicinity of the Chile Triple junction: Geology, v. 21, pp. 905-908. Borowski, W.S., C.K. Paull, and U. William, III, 1999, Global and local variations of interstitial sulfate gradients...

  15. Study of Formation Mechanisms of Gas Hydrate

    Science.gov (United States)

    Yang, Jia-Sheng; Wu, Cheng-Yueh; Hsieh, Bieng-Zih

    2015-04-01

    Gas hydrates, which had been found in subsurface geological environments of deep-sea sediments and permafrost regions, are solid crystalline compounds of gas molecules and water. The estimated energy resources of hydrates are at least twice of that of the conventional fossil fuel in the world. Gas hydrates have a great opportunity to become a dominating future energy. In the past years, many laboratory experiments had been conducted to study chemical and thermodynamic characteristics of gas hydrates in order to investigate the formation and dissociation mechanisms of hydrates. However, it is difficult to observe the formation and dissociation of hydrates in a porous media from a physical experiment directly. The purpose of this study was to model the dynamic formation mechanisms of gas hydrate in porous media by reservoir simulation. Two models were designed for this study: 1) a closed-system static model with separated gas and water zones; this model was a hydrate equilibrium model to investigate the behavior of the formation of hydrates near the initial gas-water contact; and 2) an open-system dynamic model with a continuous bottom-up gas flow; this model simulated the behavior of gas migration and studied the formation of hydrates from flowed gas and static formation water in porous media. A phase behavior module was developed in this study for reservoir simulator to model the pressure-volume-temperature (PVT) behavior of hydrates. The thermodynamic equilibriums and chemical reactions were coupled with the phase behavior module to have functions modelling the formation and dissociation of hydrates from/to water and gas. The simulation models used in this study were validated from the code-comparison project proposed by the NETL. According to the modelling results of the closed-system static model, we found that predominated location for the formation of hydrates was below the gas-water contact (or at the top of water zone). The maximum hydrate saturation

  16. Soft-tissue balance evaluation system for total hip arthroplasty by intraoperative contact pressure measurement at the hip joint.

    Science.gov (United States)

    Otake, Yoshito; Suzuki, Naoki; Hattori, Asaki; Hayashibe, Mitsuhiro; Miki, Hidenobu; Yamamura, Mitsuyoshi; Sugano, Nobuhiko; Yonenobu, Kazuo; Ochi, Takahiro

    2006-01-01

    We developed a system for measurement of contact pressure at the hip joint surfaces that enables checking of the artificial hip joint condition during surgery. First, we constructed the pressure sensor that forms the artificial joint. We installed eight small pressure sensors to the spherical head component, a part of the ball-socket joint. Next, we developed software for recording and visualizing the detected pressures that were recorded every 1 ms. The pressure distribution was displayed with the 3D computer graphics in real-time. The system enabled intuitive recognition of pressure direction 3-dimensions. Next, using the system, we conducted measurements during total hip arthroplasty. Although it requires some improvements in its measurement accuracy, the system allows real-time acquisition of information on the artificial hip joint in real-time. Further improvements of the calibration method should enable more accurate measurements. As a complete system, it will be a useful tool for selecting an appropriate implant that fits a patient's hip joint or for estimating the risk of complications after surgery.

  17. Diffusion and Monod kinetics model to determine in vivo human corneal oxygen-consumption rate during soft contact lens wear.

    Science.gov (United States)

    Del Castillo, Luis F; da Silva, Ana R Ferreira; Hernández, Saul I; Aguilella, M; Andrio, Andreu; Mollá, Sergio; Compañ, Vicente

    2015-01-01

    We present an analysis of the corneal oxygen consumption Qc from non-linear models, using data of oxygen partial pressure or tension (P(O2) ) obtained from in vivo estimation previously reported by other authors. (1) METHODS: Assuming that the cornea is a single homogeneous layer, the oxygen permeability through the cornea will be the same regardless of the type of lens that is available on it. The obtention of the real value of the maximum oxygen consumption rate Qc,max is very important because this parameter is directly related with the gradient pressure profile into the cornea and moreover, the real corneal oxygen consumption is influenced by both anterior and posterior oxygen fluxes. Our calculations give different values for the maximum oxygen consumption rate Qc,max, when different oxygen pressure values (high and low P(O2)) are considered at the interface cornea-tears film. Present results are relevant for the calculation on the partial pressure of oxygen, available at different depths into the corneal tissue behind contact lenses of different oxygen transmissibility. Copyright © 2014. Published by Elsevier Espana.

  18. Contact lens in keratoconus

    OpenAIRE

    Varsha M Rathi; Preeji S Mandathara; Srikanth Dumpati

    2013-01-01

    Contact lenses are required for the visual improvement in patients with keratoconus. Various contact lens options, such as rigid gas permeable (RGP) lenses, soft and soft toric lenses, piggy back contact lenses (PBCL), hybrid lenses and scleral lenses are availble. This article discusses about selection of a lens depending on the type of keratoconus and the fitting philosophies of various contact lenses including the starting trial lens. A Medline search was carried out for articles in the En...

  19. Complex admixtures of clathrate hydrates in a water desalination method

    Science.gov (United States)

    Simmons, Blake A.; Bradshaw, Robert W.; Dedrick, Daniel E.; Anderson, David W.

    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.

  20. The impact of single nucleotide polymorphisms on patterns of non-contact musculoskeletal soft tissue injuries in a football player population according to ethnicity.

    Science.gov (United States)

    Pruna, Ricard; Ribas, Jordi; Montoro, Jose Bruno; Artells, Rosa

    2015-02-02

    The prevention, diagnosis, and management of non-contact musculoskeletal soft tissue injuries (NCMSTIs) related to participation in sports are key components of sport and exercise medicine. Epidemiological data have demonstrated the existence of interindividual differences in the severity of NCMSTIs, indicating that these injuries occur as a consequence of both extrinsic and intrinsic factors, including genetic variations. We have collected data on NCMSTIs suffered by 73 elite players of White, black African and Hispanic ethnicity of European football over the course of three consecutive seasons. We have also examined eight single nucleotide polymorphisms (SNPs) in genes related to tissue recovery and tissue repair in blood drawn from the players and correlated our findings with type and severity of injuries in each ethnic group. The frequency of the SNPs varied among the three ethnic sub-groups (p<0.0001). Among Whites, a significant relationship was observed between ligament injuries and ELN (p=0.001) and between tendinous injuries and ELN (p=0.05) and IGF2 (p=0.05). Among Hispanics, there was a significant relation between muscle injuries and ELN (p=0.032) and IGF2 (p=0.016). Interracial genotypic differences may be important in the study of NCMSTIs. A genetic profile based on SNPs may be useful tool to describe each individual's injuribility risk and provide specific treatment and preventive care for football players. Copyright © 2013 Elsevier España, S.L.U. All rights reserved.

  1. Efeito do filtro de ultravioleta em lentes de contato hidrofílicas de alta hidratação Ultraviolet filter effect on hydrophilic high hydrated contact lenses

    Directory of Open Access Journals (Sweden)

    Arlindo José Freire Portes

    2008-06-01

    to estimate the efficacy of ultraviolet contact lenses with high hydration. METHODS: Six types of high hydrated contact lenses from different brands with three new equal units were evaluated, observing the transmittance rates of light energy in the wave bands between 200 to 400 nm measured with spectrophotometer. RESULTS: Three groups that had ultraviolet filters blocked sharply the Uv transmittance from 400 nm to 340 nm. There was an increase in Uv transmittance between 240 nm to 300 nm up to 45%. Below 240 nm and between 300 nm and 320 nm there was a complete Uv block. The three contact lenses types that didn't have ultraviolet filters block sharply Uv radiation below 240 nm and below 220 nm there was a complete Uv block . CONCLUSION: Contact lenses that diddn't have UV filter didin't block efficaciously Uv-A, Uv-B or Uv-C. The ultraviolet filter have blocked the Uv-B radiation almost completely, and partially the Uv-A and Uv-c.

  2. Clinical application and follow-up of new-type HD soft hydrophilic contact lenses%新型HD软性亲水角膜接触镜的临床应用随访

    Institute of Scientific and Technical Information of China (English)

    干锦华; 张俊; 吕红彬

    2012-01-01

    BACKGROUND: The wear of soft hydrophilic contact lens is a method of correcting refractive errors. But the safety and comfort of its clinical application is not definite enough. OBJECTIVE: To investigate the clinical effects and safety of a new type of HD soft hydrophilic contact lenses in comparison with the similar products-NB soft hydrophilic contact lenses that have been listed. METHODS: Seventy-two patients (144 eyes) had the same refractive state of eyes, and the diopter was 0 m"1 to -8.00 m"1. Ametropia patients whose cylinder degree of the better eyes was sc -\\ oo m"1 were randomly divided into experimental group (wearing HD soft hydrophilic contact lenses) and control group (wearing NB soft hydrophilic contact lens) for vision correction. RESULTS AND CONCLUSION: After treatment for 1 week, 1 month and 3 months, there were no significant differences between the experimental group and control group (P > 0.05). These findings suggest that the new-type HD soft hydrophilic contact lenses are safe and effective.%背景:配戴软性亲水角膜接触镜是矫治屈光不正的一种方法.目的:通过与已上市的同类产品NB 软性亲水角膜接触镜对比,观察新型HD 软性亲水角膜接触镜的临床效果及其安全性.方法:将72 例(144 眼)双眼屈光状态基本相同,屈光度在0 ~ -8.00 m-1之间,其中较好眼的柱镜度≤ -1.00 m-1的屈光不正患者随机分成试验组和对照组,分别佩戴HD软性亲水角膜接触镜与NB软性亲水角膜接触镜矫正视力.结果与结论:佩戴1 周、1 个月、3 个月后,两组视力矫正水平、视力清晰程度、视力稳定性、舒适性、角膜点状染色、角膜水肿差异均无显著性意义(P > 0.05).说明新型HD 软性亲水角膜接触镜的临床应用安全有效.

  3. Dynamic impact indentation of hydrated biological tissues and tissue surrogate gels

    Science.gov (United States)

    Ilke Kalcioglu, Z.; Qu, Meng; Strawhecker, Kenneth E.; Shazly, Tarek; Edelman, Elazer; VanLandingham, Mark R.; Smith, James F.; Van Vliet, Krystyn J.

    2011-03-01

    For both materials engineering research and applied biomedicine, a growing need exists to quantify mechanical behaviour of tissues under defined hydration and loading conditions. In particular, characterisation under dynamic contact-loading conditions can enable quantitative predictions of deformation due to high rate 'impact' events typical of industrial accidents and ballistic insults. The impact indentation responses were examined of both hydrated tissues and candidate tissue surrogate materials. The goals of this work were to determine the mechanical response of fully hydrated soft tissues under defined dynamic loading conditions, and to identify design principles by which synthetic, air-stable polymers could mimic those responses. Soft tissues from two organs (liver and heart), a commercially available tissue surrogate gel (Perma-Gel™) and three styrenic block copolymer gels were investigated. Impact indentation enabled quantification of resistance to penetration and energy dissipative constants under the rates and energy densities of interest for tissue surrogate applications. These analyses indicated that the energy dissipation capacity under dynamic impact increased with increasing diblock concentration in the styrenic gels. Under the impact rates employed (2 mm/s to 20 mm/s, corresponding to approximate strain energy densities from 0.4 kJ/m3 to 20 kJ/m3), the energy dissipation capacities of fully hydrated soft tissues were ultimately well matched by a 50/50 triblock/diblock composition that is stable in ambient environments. More generally, the methodologies detailed here facilitate further optimisation of impact energy dissipation capacity of polymer-based tissue surrogate materials, either in air or in fluids.

  4. Contact lens in keratoconus

    Directory of Open Access Journals (Sweden)

    Varsha M Rathi

    2013-01-01

    Full Text Available Contact lenses are required for the visual improvement in patients with keratoconus. Various contact lens options, such as rigid gas permeable (RGP lenses, soft and soft toric lenses, piggy back contact lenses (PBCL, hybrid lenses and scleral lenses are availble. This article discusses about selection of a lens depending on the type of keratoconus and the fitting philosophies of various contact lenses including the starting trial lens. A Medline search was carried out for articles in the English language with the keywords keratoconus and various contact lenses such as Rose k lens, RGP lens, hybrid lens, scleral lens and PBCL.

  5. Binding Hydrated Anions with Hydrophobic Pockets.

    Science.gov (United States)

    Sokkalingam, Punidha; Shraberg, Joshua; Rick, Steven W; Gibb, Bruce C

    2016-01-13

    Using a combination of isothermal titration calorimetry and quantum and molecular dynamics calculations, we demonstrate that relatively soft anions have an affinity for hydrophobic concavity. The results are consistent with the anions remaining partially hydrated upon binding, and suggest a novel strategy for anion recognition.

  6. Fusarium and Candida albicans biofilms on soft contact lenses: model development, influence of lens type and susceptibility to lens care solutions

    Science.gov (United States)

    Fungal keratitis is commonly caused by Fusarium species, while cases of Candida-associated keratitis are less frequent. Recent outbreaks of Fusarium keratitis were associated with contact lens wear and with MoistureLoc contact lens care solution, and biofilm formation on contact lens/lens cases was...

  7. Clathrate hydrates in nature.

    Science.gov (United States)

    Hester, Keith C; Brewer, Peter G

    2009-01-01

    Scientific knowledge of natural clathrate hydrates has grown enormously over the past decade, with spectacular new findings of large exposures of complex hydrates on the sea floor, the development of new tools for examining the solid phase in situ, significant progress in modeling natural hydrate systems, and the discovery of exotic hydrates associated with sea floor venting of liquid CO2. Major unresolved questions remain about the role of hydrates in response to climate change today, and correlations between the hydrate reservoir of Earth and the stable isotopic evidence of massive hydrate dissociation in the geologic past. The examination of hydrates as a possible energy resource is proceeding apace for the subpermafrost accumulations in the Arctic, but serious questions remain about the viability of marine hydrates as an economic resource. New and energetic explorations by nations such as India and China are quickly uncovering large hydrate findings on their continental shelves.

  8. Comparison of corneal histopathology changes between the rigid gas permeable contact lens wearers and the soft contact lens wearers%配戴RGPCL和SCL后角膜组织病理学变化的比较

    Institute of Scientific and Technical Information of China (English)

    韩治华; 胡楠

    2010-01-01

    目的 探讨配戴硬性透气性角膜接触镜(RGPCL)和软性角膜接触镜(SCL)对角膜组织的影响.方法 病例对照研究.高度近视患者60例,30例配戴RGPCL,30例配戴SCL.在配戴3、6、12个月后,应用激光共焦显微镜检查两组患者的中央角膜和周边角膜上皮层、上皮下Langerhans细胞、神经纤维、角膜基质层、角膜内皮细胞及角膜厚度的变化.采用两因素方差分析对数据进行分析.结果 戴镜1年后,SCL组中央角膜表层细胞密度低于RGPCL组(F=4.262,P<0.05),上皮层可见微小囊泡及类似角膜营养不良的角膜小滴,上皮下Langerhans细胞密度及神经纤维曲折度均大于RGPCL组(F=5.362,P<0.05;F=-14.910,P<0.05).SCL组中央角膜浅基质层细胞密度低于RGPCL组(P<0.05),基质层中各层白色点状物密度均高于RGPCL组(P<0.05).SCL组内皮细胞形态变化较RGPCL组明显,但两组内皮细胞密度差异无统计学意义.SCL组中央角膜上皮层厚度小于RGPCL组(F=-2.061,P<0.05).同一戴镜组内各个观察指标在3个月、6个月、12个月间的差异均无统计学意义.结论 RGPCL配戴者角膜上皮细胞、前基质细胞、内皮细胞、Langerhans细胞及神经纤维的变化均轻于SCL配戴者,提示RGPCL的安全性更高.%Objective To investigate the corneal morphologic changes induced by wearing rigid gas permeable contact lenses (RGPCL) and soft contact lenses (SCL). Methods It was a case-control study. Sixty high myopia subjects participated in the study. Thirty were given RGPCL and 30 were given SCL Three, 6 and 12 months after wearing the contact lenses, confocal microscopy was used to observe the central and peripheral corneal epithelial cells, the density of the Langerhans cells,nerve fibers, corneal stroma, and endothelial cells of the 2 groups. A two-way ANOVA was used to analyze the data. Results Twelve months after contact lens wearing, the epithelial cell density of the corneal surface was lower

  9. Contact Lens Risks

    Science.gov (United States)

    ... Tap and distilled water have been associated with Acanthamoeba keratitis, a corneal infection that is resistant to ... to: Advice for Patients With Soft Contact Lenses: Acanthamoeba Keratitis Infections Related to Complete® MoisturePlus Multi Purpose ...

  10. A Wearable Hydration Sensor with Conformal Nanowire Electrodes.

    Science.gov (United States)

    Yao, Shanshan; Myers, Amanda; Malhotra, Abhishek; Lin, Feiyan; Bozkurt, Alper; Muth, John F; Zhu, Yong

    2017-01-27

    A wearable skin hydration sensor in the form of a capacitor is demonstrated based on skin impedance measurement. The capacitor consists of two interdigitated or parallel electrodes that are made of silver nanowires (AgNWs) in a polydimethylsiloxane (PDMS) matrix. The flexible and stretchable nature of the AgNW/PDMS electrode allows conformal contact to the skin. The hydration sensor is insensitive to the external humidity change and is calibrated against a commercial skin hydration system on an artificial skin over a wide hydration range. The hydration sensor is packaged into a flexible wristband, together with a network analyzer chip, a button cell battery, and an ultralow power microprocessor with Bluetooth. In addition, a chest patch consisting of a strain sensor, three electrocardiography electrodes, and a skin hydration sensor is developed for multimodal sensing. The wearable wristband and chest patch may be used for low-cost, wireless, and continuous monitoring of skin hydration and other health parameters.

  11. Comparative Assessment of Advanced Gay Hydrate Production Methods

    Energy Technology Data Exchange (ETDEWEB)

    M. D. White; B. P. McGrail; S. K. Wurstner

    2009-06-30

    Displacing natural gas and petroleum with carbon dioxide is a proven technology for producing conventional geologic hydrocarbon reservoirs, and producing additional yields from abandoned or partially produced petroleum reservoirs. Extending this concept to natural gas hydrate production offers the potential to enhance gas hydrate recovery with concomitant permanent geologic sequestration. Numerical simulation was used to assess a suite of carbon dioxide injection techniques for producing gas hydrates from a variety of geologic deposit types. Secondary hydrate formation was found to inhibit contact of the injected CO{sub 2} regardless of injectate phase state, thus diminishing the exchange rate due to pore clogging and hydrate zone bypass of the injected fluids. Additional work is needed to develop methods of artificially introducing high-permeability pathways in gas hydrate zones if injection of CO{sub 2} in either gas, liquid, or micro-emulsion form is to be more effective in enhancing gas hydrate production rates.

  12. Soft calender; Soft calender

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-04-20

    This facility is a soft nip calender with both hot roll and soft roll. Since a multi-zone controlled shim CD roll is used as the soft roll, profile control of a caliper is possible only by deflection control of the roll without any peripheral facility. Main specifications: (1) Kinds of paper: newspaper paper, medium-quality paper, (2) Designed processing speed: 1,100m/min, (3) Paper width: 8,300mm. Features: (1) Possible of keeping paper strength by soft nip, (2) Soft paper surface, high smoothness and excellent gloss by using the hot roll, (3) Uniform ink absorbing by a constant paper bulk density, (4) Large mass even in kinds of paper including much DIP by possible low-linear pressure operation. (translated by NEDO)

  13. Avaliação da qualidade óptica de lentes de contato gelatinosas na correção de miopia Evaluation of optical performance of soft contact lenses in myopic correction

    Directory of Open Access Journals (Sweden)

    Marcelo Weslley Dalcoll

    2008-12-01

    ções de acuidade visual logMAR de baixo contraste, sensibilidade ao contraste, índice de Strehl, MTF e das aberrações de alta ordem.PURPOSE: To evaluate the optical performance of eyes fitted with two different soft contact lenses: Acuvue® 2 (Vistacon J&J Vision Care Inc., USA and World Vision Disposable Asférica Wave Front® (World Vision Ophthalmic, Brazil. METHODS: An interventional prospective clinical trial studied a sample of 40 myopic patients (-0.75D to -4.50D, with or without astigmatism up to -0.75D. Each patient had one eye randomized to visual performance evaluation including high and low contrast visual acuities, wavefront analysis and contrast sensitivity. RESULTS: The Nidek OPD Scan detected a residual refraction (hypercorrection for both contact lenses. High contrast visual acuity was significantly higher for World Vision soft contact lenses. Low contrast visual acuity was similar for both soft contact lenses. Contrast sensitivity improved significantly at 1.5; 3; 6 e 18 spatial frequencies for both soft contact lenses, but no difference was found between them. Regarding wavefront analysis, no difference was found between both soft contact lenses. There were not significantly differences in the Strehl indices and MTF for both soft contact lenses. CONCLUSION: World Vision Disposable Asférica Wave Front® soft contact lenses had a better performance regarding high contrast visual acuity. However, low contrast visual acuity, wavefront analysis and contrast sensitivity were similar for both soft contact lenses.

  14. Soft-Etching Copper and Silver Electrodes for Significant Device Performance Improvement toward Facile, Cost-Effective, Bottom-Contacted, Organic Field-Effect Transistors.

    Science.gov (United States)

    Wang, Zongrui; Dong, Huanli; Zou, Ye; Zhao, Qiang; Tan, Jiahui; Liu, Jie; Lu, Xiuqiang; Xiao, Jinchong; Zhang, Qichun; Hu, Wenping

    2016-03-01

    Poor charge injection and transport at the electrode/semiconductor contacts has been so far a severe performance hurdle for bottom-contact bottom-gate (BCBG) organic field-effect transistors (OFETs). Here, we have developed a simple, economic, and effective method to improve the carrier injection efficiency and obtained high-performance devices with low cost and widely used source/drain (S/D) electrodes (Ag/Cu). Through the simple electrode etching process, the work function of the electrodes is more aligned with the semiconductors, which reduces the energy barrier and facilitates the charge injection. Besides, the formation of the thinned electrode edge with desirable micro/nanostructures not only leads to the enlarged contact side area beneficial for the carrier injection but also is in favor of the molecular self-organization for continuous crystal growth at the contact/active channel interface, which is better for the charge injection and transport. These effects give rise to the great reduction of contact resistance and the amazing improvement of the low-cost bottom-contact configuration OFETs performance.

  15. A Lagrange multiplier mixed finite element formulation for three-dimensional contact of biphasic tissues.

    Science.gov (United States)

    Yang, Taiseung; Spilker, Robert L

    2007-06-01

    A three-dimensional (3D) contact finite element formulation has been developed for biological soft tissue-to-tissue contact analysis. The linear biphasic theory of Mow, Holmes, and Lai (1984, J. Biomech., 17(5), pp. 377-394) based on continuum mixture theory, is adopted to describe the hydrated soft tissue as a continuum of solid and fluid phases. Four contact continuity conditions derived for biphasic mixtures by Hou et al. (1989, ASME J. Biomech. Eng., 111(1), pp. 78-87) are introduced on the assumed contact surface, and a weighted residual method has been used to derive a mixed velocity-pressure finite element contact formulation. The Lagrange multiplier method is used to enforce two of the four contact continuity conditions, while the other two conditions are introduced directly into the weighted residual statement. Alternate formulations are possible, which differ in the choice of continuity conditions that are enforced with Lagrange multipliers. Primary attention is focused on a formulation that enforces the normal solid traction and relative fluid flow continuity conditions on the contact surface using Lagrange multipliers. An alternate approach, in which the multipliers enforce normal solid traction and pressure continuity conditions, is also discussed. The contact nonlinearity is treated with an iterative algorithm, where the assumed area is either extended or reduced based on the validity of the solution relative to contact conditions. The resulting first-order system of equations is solved in time using the generalized finite difference scheme. The formulation is validated by a series of increasingly complex canonical problems, including the confined and unconfined compression, the Hertz contact problem, and two biphasic indentation tests. As a clinical demonstration of the capability of the contact analysis, the gleno-humeral joint contact of human shoulders is analyzed using an idealized 3D geometry. In the joint, both glenoid and humeral head

  16. Desempenho visual na correção de miopia com óculos e lentes de contato gelatinosas Visual performance in myopic correction with spectacles and soft contact lenses

    Directory of Open Access Journals (Sweden)

    Breno Barth

    2008-02-01

    with three different soft contact lenses [Acuvue® 2 (Vistacon J&J Vision Care Inc., USA, Biomedics® 55 (Ocular Science, USA, and Focus® 1-2 week (Ciba Vision Corporation, USA]. METHODS: An interventional prospective clinical trial studied a sample of 40 myopic patients (-1.00 to -4.50 sph, with or without astigmatism up to -0.75 cyl. Each patient had one eye randomized to visual performance evaluation. RESULTS: The Zywave aberrometer detected a over refraction and significant difference between Acuvue® 2 and Biomedics® 55 regarding spheric refractive components and spheric equivalent. Both soft contact lenses showed hypercorrection as compared to Focus® 1-2 week. Visual performance was not significantly different with spectacles and the three soft contact lenses in visual acuity and contrast sensitivity measurements. The wavefront analysis detected a significant difference in a third order aberration with and without soft contact lenses, with better visual performance with Acuvue® 2 and Biomedics® 55. CONCLUSION: In visual performance evaluation with spectacles and soft contact lenses the wavefront analysis was a more sensible measurement of visual function when compared to high contrast visual acuity and contrast sensitivity. The evaluation model of visual performance with wavefront analysis developed in this investigation may be useful for further similar studies.

  17. Gas Hydrate Storage of Natural Gas

    Energy Technology Data Exchange (ETDEWEB)

    Rudy Rogers; John Etheridge

    2006-03-31

    lower heat transfer rate in the internal heat exchanger than was designed. It is believed that the fins on the heat-exchanger tubes did not make proper contact with the tubes transporting the chilled glycol, and pairs of fins were too close for interior areas of fins to serve as hydrate collection sites. A correction of the fabrication fault in the heat exchanger fin attachments could be easily made to provide faster formation rates. The storage success with the POC process provides valuable information for making the process an economically viable process for safe, aboveground natural-gas storage.

  18. Phthalates in soft PVC products used in food production equipment and in other food contact materials on the Danish and the Nordic Market 2013-2014

    DEFF Research Database (Denmark)

    Petersen, Jens Højslev; Jensen, Lisbeth Krüger

    2016-01-01

    to food type, contact temperature and time in contact with food. In both recent control campaigns about 1/3 of the samples analysed exceeded the current maximum limits for phthalates (especially DBP and DEHP) in plastics or showed migration into the fatty food simulant above the specific migration limits....... Critical sample types were conveyor belts, hoses and gloves. Conclusions Legal limits for phthalates were exceeded in many of the samples analysed in recent tests, including a large proportion of conveyor belts and gloves. The proportion of non-compliant conveyor belts, hoses and gaskets was lower in 2013...

  19. Origins of hydration lubrication.

    Science.gov (United States)

    Ma, Liran; Gaisinskaya-Kipnis, Anastasia; Kampf, Nir; Klein, Jacob

    2015-01-14

    Why is friction in healthy hips and knees so low? Hydration lubrication, according to which hydration shells surrounding charges act as lubricating elements in boundary layers (including those coating cartilage in joints), has been invoked to account for the extremely low sliding friction between surfaces in aqueous media, but not well understood. Here we report the direct determination of energy dissipation within such sheared hydration shells. By trapping hydrated ions in a 0.4-1 nm gap between atomically smooth charged surfaces as they slide past each other, we are able to separate the dissipation modes of the friction and, in particular, identify the viscous losses in the subnanometre hydration shells. Our results shed light on the origins of hydration lubrication, with potential implications both for aqueous boundary lubricants and for biolubrication.

  20. Too late, too vague, too soft: How and why the idea of the first point of contact in the Icelandic health care system has failed

    Directory of Open Access Journals (Sweden)

    Sigurbjörg Sigurgeirsdóttir

    2015-12-01

    Full Text Available This research is about ideas, interests and institutions in health care in Iceland. It describes how the idea of primary care centres as the first point of patients´ contact in health care, on one hand, and the idea of patients´ freedom to choose where to seek medical care, on the other, have been the competing views shaping the system for almost fifty years. The research seeks to shed lights on why the authorities have not succeeded in making primary care become the first point of contact in health care. It aims to create a better understanding about why and how such a gap between objectives and outcomes in public policy emerges. This study draws on published and unpublished findings from the author´s earlier research on the Icelandic health care system, and interviews with medical doctors, civil servants and politicians. Theories on policy implementation are applied in order to bring out a theoretical perspective on government´s policy implementation. Furthermore, the research brings out how issues in health care reach government´s agenda and why government´s attempts at change do sometimes succeed, but most often don´t. It concludes that better access to primary care services emphasized by the early 1970s legislation was first and foremost aimed at people living outside the two main urban areas. On the other hand, the idea of patients´ first point of contact as a goal of government policy emerged too late, its aim and implementation was too ambiguous and the tool of government applied too weak.

  1. Electrostatic interaction of soft particles.

    Science.gov (United States)

    Ohshima, Hiroyuki

    2015-12-01

    Theories of the electrostatic interaction between two soft particles (i.e., particles covered with an ion-penetrable surface layer of polyelectrolytes) in an electrolyte solution are reviewed. Interactions of soft particles after contact of their surface layers are particularly discussed. Interaction in a salt-free medium and the discrete-charge effect are also treated.

  2. Hydration Assessment of Athletes

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ KEY POINTS · Although there is no scientific consensus for 1 ) howbest to assess the hydration status of athletes, 2)what criteria to use as acceptable outcome measurements, or 3) the best time to apply practical assessment methods, there are methods that can be used toprovide athletes with useful feedback about their hydration status

  3. Preparation and evaluation of a contact lens vehicle for puerarin delivery.

    Science.gov (United States)

    Xu, Jinku; Li, Xinsong; Sun, Fuqian

    2010-01-01

    The purpose of this study is to develop a soft contact lens vehicle for puerarin delivery to alleviate glaucoma. Poly(2-hydroxy-ethyl methacrylate-co-N-vinylpyrrolidone-co-methyl acrylate) (pHEMA-NVP-MA) contact lenses were prepared by UV irradiation of HEMA, NVP and MA, to which the cross-linker, a mixture of trimethylolpropane trimethacrylate (TMPTMA) and allyl methacrylate (AMA) (1:1, w/w) was added previously. The contact lenses were characterized by equilibrium swelling ratio (ESR) and tensile tester. The results showed that incorporation of poly-N-vinylpyrrolidone (PVP) component in the hydrogels caused increase of ESR and decrease of tensile strength. Co-polymerization of MA monomer in the hydrogel led to a slight drop of ESR and improved tensile strength of hydrogel. Four kinds of hydrated contact lenses with different PVP content were presoaked in PBS solution of puerarin and the in vitro drug release was measured. The contact lenses matrix incorporated with PVP had a remarkable loading capacity of puerarin. In rabbit eyes, the presoaked contact lenses extended the mean resident time of puerarin to 77.45 min from 12.88 min of 1% puerarin eye drops. Moreover, contact lens presoaked in puerarin solution at the concentration of 0.802 mg/ml showed about the same bioavailability (AUC(0-t)) in tear fluid as that of the puerarin eye drops. This kind of presoaked contact lens has potential application as vehicle of puerarin to alleviate glaucoma.

  4. Hydration rate of obsidian.

    Science.gov (United States)

    Friedman, I; Long, W

    1976-01-30

    The hydration rates of 12 obsidian samples of different chemical compositions were measured at temperatures from 95 degrees to 245 degrees C. An expression relating hydration rate to temperature was derived for each sample. The SiO(2) content and refractive index are related to the hydration rate, as are the CaO, MgO, and original water contents. With this information it is possible to calculate the hydration rate of a sample from its silica content, refractive index, or chemical index and a knowledge of the effective temperature at which the hydration occurred. The effective hydration temperature can be either measured or approximated from weather records. Rates have been calculated by both methods, and the results show that weather records can give a good approximation to the true EHT, particularly in tropical and subtropical climates. If one determines the EHT by any of the methods suggested, and also measures or knows the rate of hydration of the particular obsidian used, it should be possible to carry out absolute dating to +/- 10 percent of the true age over periods as short as several years and as long as millions of years.

  5. Process and device for hydrating organic compounds which can be hydrated by cathodically separated hydrogen. Verfahren und Vorrichtung zur Hydrierung von hydrierbaren organischen Verbindungen durch kathodisch abgeschiedenen Wasserstoff

    Energy Technology Data Exchange (ETDEWEB)

    Biallas, B.; Schulten, R.; Weirich, W.

    1984-03-29

    Hydratable compounds, particularly alcohols, can be hydrated by cathodically separated hydrogen, by bringing them into contact with the back of the cathode, which is itself permeable to hydrogen. This procedure is particularly suitable for the hydration of methanol by cathodically separated hydrogen during electrolysis of water in the context of a hybrid circuit process for generating hydrogen, together with steam reforming and synthesis of methanol as further parts of the process.

  6. Hydrate morphology: Physical properties of sands with patchy hydrate saturation

    Science.gov (United States)

    Dai, S.; Santamarina, J.C.; Waite, William F.; Kneafsey, T.J.

    2012-01-01

    The physical properties of gas hydrate-bearing sediments depend on the volume fraction and spatial distribution of the hydrate phase. The host sediment grain size and the state of effective stress determine the hydrate morphology in sediments; this information can be used to significantly constrain estimates of the physical properties of hydrate-bearing sediments, including the coarse-grained sands subjected to high effective stress that are of interest as potential energy resources. Reported data and physical analyses suggest hydrate-bearing sands contain a heterogeneous, patchy hydrate distribution, whereby zones with 100% pore-space hydrate saturation are embedded in hydrate-free sand. Accounting for patchy rather than homogeneous hydrate distribution yields more tightly constrained estimates of physical properties in hydrate-bearing sands and captures observed physical-property dependencies on hydrate saturation. For example, numerical modeling results of sands with patchy saturation agree with experimental observation, showing a transition in stiffness starting near the series bound at low hydrate saturations but moving toward the parallel bound at high hydrate saturations. The hydrate-patch size itself impacts the physical properties of hydrate-bearing sediments; for example, at constant hydrate saturation, we find that conductivity (electrical, hydraulic and thermal) increases as the number of hydrate-saturated patches increases. This increase reflects the larger number of conductive flow paths that exist in specimens with many small hydrate-saturated patches in comparison to specimens in which a few large hydrate saturated patches can block flow over a significant cross-section of the specimen.

  7. Wet hydrate dissolution plant

    OpenAIRE

    Stanković Mirjana S.; Kovačević Branimir T.; Pezo Lato L.

    2003-01-01

    The IGPC Engineering Department designed basic projects for a wet hydrate dissolution plant, using technology developed in the IGPC laboratories. Several projects were completed: technological, machine, electrical, automation. On the basis of these projects, a production plant with capacity of 50,000 t/y was manufactured, at "Zeolite Mira", Mira (VE), Italy, in 1997, for increasing detergent zeolite production from 50,000 to 100,000 t/y. Several goals were realized by designing a wet hydrate ...

  8. Bilateral Acanthamoeba ulcer in a user of disposable soft contact lenses: a tragic incident or a consequence of the aggressive policy of soft contact lens trading? Úlcera bilateral por Acanthamoeba em usuária de lentes de contato gelatinosas descartáveis: um incidente trágico ou uma conseqüência da política agressiva de venda de lentes de contato gelatinosas?

    Directory of Open Access Journals (Sweden)

    Sidney Júlio de Faria e Sousa

    2008-06-01

    Full Text Available This is the report of a case of bilateral Acanthamoeba keratitis in a 19-year-old woman who bought a pair of disposable soft contact lenses in a boutique. She wore this same pair of lenses for 3 months daily without the appropriate care. This led to bilateral corneal transplantation with cataract extraction and also trabeculectomy in the right eye. When last seen, both grafts were crystal clear but the visual acuities were far from satisfactory. She also had bilateral secondary glaucoma, barely controlled by topical medication. Actually, the physical features and the wearing time characteristics of the disposable soft contact lenses created unprecedented difficulties to the medical surveillance of their wearers. Without the right assistance they tend to become careless regarding routine cleaning. They also feel free to buy less expensive lenses, to use saline instead of lens solutions, to violate the limits of wearing time and to extend the use over the sleeping period. Additionally, the aggressive marketing and the wide distribution of these lenses increase the chances that economically or educationally unprepared people will acquire them. The question that remains is: Is the present case an accidental event or an example of what is likely to happen in the future if the indiscriminate selling of disposable soft contact lenses continues to evolve?Este é o relato de uma paciente do sexo feminino, de 19 anos, com ceratite bilateral por Acanthamoeba, devido ao uso de lentes de contato descartáveis, adquiridas em uma butique. Fez uso do mesmo par de lentes durante três meses, sem os cuidados adequados. Foi submetida a transplante penetrante de córnea e facectomia bilateral, além de trabeculectomia no olho direito. Quando vista pela última vez, os enxertos estavam transparentes, mas a visão de ambos os olhos não era satisfatória. Ela também apresentava glaucoma secundário bilateral, controlado precariamente com medicação tópica. Ocorre

  9. Spectroscopic determination of optimal hydration time of zircon surface

    Energy Technology Data Exchange (ETDEWEB)

    Ordonez R, E. [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Garcia R, G. [Instituto Tecnologico de Toluca, Division de Estudios del Posgrado, Av. Tecnologico s/n, Ex-Rancho La Virgen, 52140 Metepec, Estado de Mexico (Mexico); Garcia G, N., E-mail: eduardo.ordonez@inin.gob.m [Universidad Autonoma del Estado de Mexico, Facultad de Quimica, Av. Colon y Av. Tollocan, 50180 Toluca, Estado de Mexico (Mexico)

    2010-07-01

    When a mineral surface is immersed in an aqueous solution, it develops and electric charge produced by the amphoteric dissociation of hydroxyl groups created by the hydration of the solid surface. This is one influential surface property. The complete hydration process takes a time which is specific for each mineral species. The knowledge of the aqueous solution contact time for complete surface hydration is mandatory for further surface phenomena studies. This study deals with the optimal hydration time of the raw zircon (ZrSiO{sub 4}) surface comparing the classical potentiometric titrations with a fluorescence spectroscopy technique. The latter is easy and rea liable as it demands only one sample batch to determine the optimal time to ensure a total hydration of the zircon surface. The analytical results of neutron activation analysis showed the presence of trace quantities of Dy{sup 3+}, Eu{sup 3+} and Er{sup 3} in the bulk of zircon. The Dy{sup 3+} is structured in the zircon crystalline lattice and undergoes the same chemical reactions as zircon. Furthermore, the Dy{sup 3+} has a good fluorescent response whose intensity is enhanced by hydration molecules. The results show that, according to the potentiometric analysis, the hydration process for each batch (at least 8 sample batches) takes around 2 h, while the spectrometric method indicates only 5 minutes from only one batch. Both methods showed that the zircon surface have a 16 h optimal hydration time. (Author)

  10. Desempenho visual de lentes de contato gelatinosas de diferentes tipos baseado na análise de frentes de onda Optical performance of different soft contact lenses based on wavefront analysis

    Directory of Open Access Journals (Sweden)

    Roberta Fagnani Gatti

    2008-12-01

    valor médio de outras aberrações de alta ordem (que exclui coma de terceira ordem e aberração esférica de quarta ordem, caracterizada pelo componente "outros" no exame de aberrometria. As lentes Focus® Choice AB apresentaram melhor desempenho visual em relação a este componente. CONCLUSÕES: O uso de lentes de contato gelatinosas alteram o comportamento das aberrações de alta ordem, com tendência ao aumento no valor médio das aberrações de Zernike assimétricas. Tal tendência ao aumento não foi verificada para as aberrações simétricas. Não foram encontradas diferenças estatisticamente significantes ao compararmos o padrão de influência obtido com os seis tipos de lentes incluídos no estudo.PURPOSE: To evaluate the visual performance by wavefront analyses of six different kinds of soft contact lenses: Cooperflex® (Cooper Vision, Frequency® 55 Aspheric (Cooper Vision, World Vision FW® (World Vision, Pure Vision® (Bausch & Lomb, Focus® Monthly (Ciba Vision and Focus® Choice AB (Ciba Vision. METHODS: A prospective study was performed with 130 eyes of 71 myopic or hyperopic patients with astigmatism until 1.50 diopter and best corrected visual acuity 20/20 or better. The patients first underwent ophthalmic examination and then wavefront analyses without visual correction and wearing one of the different contact lenses included in the study. The patients were divided into six similar groups, each one tested with one of the six lenses included in the study. RESULTS: Changes at the values of high order aberrations were verified during the use of contact lenses. In 78 (60% of the 130 analyzed eyes an increase at the RMS (rooth mean square values during the use of contact lens was detected. All types of analyzed contact lenses showed an increase of "coma" aberrations due to contact lens use. Frequency® Aspheric and Cooperflex® had the best visual performance in relation to "coma". There was a decrease in the medium value of spherical aberrations

  11. Air Flotation/Hydrolysis Acidification/Biological Contact Oxidation/BAF Process for Soft Drink-processing Wastewater Treatment%气浮/水解酸化/接触氧化/BAF工艺处理饮料生产废水

    Institute of Scientific and Technical Information of China (English)

    潘登; 王娟; 周俊强; 贾莹莹

    2013-01-01

    The wastewater from a soft drink-processing enterprise was characterized with high concentration of SS and good biodegradability. Air flotation/hydrolysis acidification/biological contact oxidation/biological aerated filter process was used to treat the wastewater. High treatment efficiency was a-chieved, and the effluent quality met the first level A criteria specified in the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant ( GB 18918 - 2002 ) .%某饮料生产企业废水具有悬浮物含量较高、可生化性较好的特点,采用气浮/水解酸化/生物接触氧化/曝气生物滤池多级工艺处理,取得了较好的处理效果,出水水质达到了《城镇污水处理厂污染物排放标准》(GB 18918-2002)的一级A标准.

  12. Multifocal contact lens myopia control.

    Science.gov (United States)

    Walline, Jeffrey J; Greiner, Katie L; McVey, M Elizabeth; Jones-Jordan, Lisa A

    2013-11-01

    Previous studies on soft multifocal contact lens myopia control published in the peer-reviewed literature reported findings of noncommercial contact lenses worn for 1 year or less. This study sought to determine the progression of myopia and axial elongation of children fitted with commercially available distance center soft multifocal contact lenses for 2 years. Eight- to eleven-year-old children with -1.00 D to -6.00 D spherical component and less than 1.00 D astigmatism were fitted with soft multifocal contact lenses with a +2.00 D add (Proclear Multifocal "D"; CooperVision, Fairport, NY). They were age- and gender-matched to participants from a previous study who were fitted with single-vision contact lenses (1 Day Acuvue; Vistakon, Jacksonville, FL). A-scan ultrasound and cycloplegic autorefraction were performed at baseline, after 1 year, and after 2 years. Multilevel modeling was used to compare the rate of change of myopia and axial length between single-vision and soft multifocal contact lens wearers. Forty participants were fitted with soft multifocal contact lenses, and 13 did not contribute complete data (5 contributed 1 year of data). The adjusted mean ± standard error spherical equivalent progression of myopia at 2 years was -1.03 ± 0.06 D for the single-vision contact lens wearers and -0.51 ± 0.06 for the soft multifocal contact lens wearers (p < 0.0001). The adjusted mean axial elongation was 0.41 ± 0.03 and 0.29 ± 0.03 for the single-vision and soft multifocal contact lens wearers, respectively (p < 0.0016). Soft multifocal contact lens wear resulted in a 50% reduction in the progression of myopia and a 29% reduction in axial elongation during the 2-year treatment period compared to a historical control group. Results from this and other investigations indicate a need for a long-term randomized clinical trial to investigate the potential for soft multifocal contact lens myopia control.

  13. Contact dermatitis

    Science.gov (United States)

    Dermatitis - contact; Allergic dermatitis; Dermatitis - allergic; Irritant contact dermatitis; Skin rash - contact dermatitis ... There are 2 types of contact dermatitis. Irritant dermatitis: This ... with acids, alkaline materials such as soaps and detergents , ...

  14. Soft, Embodied, Situated & Connected

    DEFF Research Database (Denmark)

    Tomico, Oscar; Wilde, Danielle

    2016-01-01

    Soft wearables include clothing and textile-based accessories that incorporate smart textiles and soft electronic interfaces to enable responsive and interactive experiences. When designed well, soft wearables leverage the cultural, sociological and material qualities of textiles, fashion and dress......; diverse capabilities and meanings of the body; as well as the qualities and capabilities afforded by smart and programmable elements. Textiles behave in particular ways. They are part of culture. No matter a person’s views on fashion, dress, their own or others’ body, they will have an intimate...... relationship with textiles, as they are one of the few products worn much of the time, often in direct contact with the body. When designing wearables a designer must consider a range of requirements that do not typically demand focus when designing products that are not worn, including: sensitivity...

  15. Soft drop

    Energy Technology Data Exchange (ETDEWEB)

    Larkoski, Andrew J. [Center for Theoretical Physics, Massachusetts Institute of Technology,Cambridge, MA 02139 (United States); Marzani, Simone [Institute for Particle Physics Phenomenology, Durham University,South Road, Durham DH1 3LE (United Kingdom); Soyez, Gregory [IPhT, CEA Saclay, CNRS URA 2306,F-91191 Gif-sur-Yvette (France); Thaler, Jesse [Center for Theoretical Physics, Massachusetts Institute of Technology,Cambridge, MA 02139 (United States)

    2014-05-29

    We introduce a new jet substructure technique called “soft drop declustering”, which recursively removes soft wide-angle radiation from a jet. The soft drop algorithm depends on two parameters — a soft threshold z{sub cut} and an angular exponent β — with the β=0 limit corresponding roughly to the (modified) mass drop procedure. To gain an analytic understanding of soft drop and highlight the β dependence, we perform resummed calculations for three observables on soft-dropped jets: the energy correlation functions, the groomed jet radius, and the energy loss due to soft drop. The β=0 limit of the energy loss is particularly interesting, since it is not only “Sudakov safe” but also largely insensitive to the value of the strong coupling constant. While our calculations are strictly accurate only to modified leading-logarithmic order, we also include a discussion of higher-order effects such as multiple emissions and (the absence of) non-global logarithms. We compare our analytic results to parton shower simulations and find good agreement, and we also estimate the impact of non-perturbative effects such as hadronization and the underlying event. Finally, we demonstrate how soft drop can be used for tagging boosted W bosons, and we speculate on the potential advantages of using soft drop for pileup mitigation.

  16. Effect of hydration film on scanning images of atomic force microscope

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A standard calibration grating was used for image scanning to investigate the effect of hydration films on imaging resolution by Atomic Force Microscope (AFM). The results showed that the hydration films greatly affect the imaging resolution for the tapping mode, but no evident effect on the contact mode. The possible reasons for the effect of hydration films on scanning images of AFM are also brought forward here.

  17. 软性虹彩片联合透气性半硬性角膜接触镜矫治外伤性无虹膜无晶状体眼%Soft cosmetic contact lens combined with half-rigid gas permeable contact lens for traumatic aniridia and aphakia

    Institute of Scientific and Technical Information of China (English)

    刘立洲; 吕燕云; 彭丽

    2011-01-01

    目的 评价软性虹彩片联合透气性半硬性角膜接触镜(RGPCL)对外伤性无虹膜无晶状体眼的矫治效果.设计回顾性病例系列.研究对象 角膜内皮细胞密度在2500个/mm2以上外伤性无虹膜无晶状体眼患者59例(59眼).方法患者联合戴用软性虹彩片和RGPCL,比较初诊时的插片视力和RGPCL矫正视力,随诊5年,非接触性角膜内皮计数仪检测角膜内皮细胞改变情况及裂隙灯下检查角结膜并发症情况.主要指标矫正视力,角膜内皮细胞计数,角结膜并发症.结果 外伤性无虹膜无晶状体眼配戴软性虹彩片联合RGPCL的平均矫正视力(0.64±0.23)明显高于初诊时的插片视力(0.33±0.21),差异有统计学意义(t=7.750,P=0.000);畏光症状减轻;初诊时平均角膜内皮细胞计数为(2695.5±125.4)个/mm2(n=59),戴镜1、2、3、4、5年分别平均为(2705.4±145.6)个/mm2(n=43),(2639.5±146.7)个/mm2(n=30),(2625.5±143.6)个/mm2(n=26),(2641.5±168.5)个/mm2(n=32),(2638.2±128.6)个/mm2(n=29),第5年与初诊相比平均减少(70.3±8.7)个/mm2.角膜、结膜未见严重并发症.结论 软性虹彩片联合RGPCL对角膜内皮细胞密度在2500个/mm2以上的外伤性无虹膜无晶状体眼在提高视力和解决畏光方面是一种有效方法,但要定期复查角结膜情况.%Objective To investigate the clinical effects of soft cosmetic contact lens combined with half-rigid gas permeable contact lens (RGPCL) for traumatic aniridia and aphakia. Design Retrospective case series. Participants 59 patients (59 eyes) with traumatic aniridia and aphakia,whose corneal endothelial cell density was above 2500 cells/mm2. Methods 59 patients (59 eyes) fitted with soft cosmetic contact lens combined with RGPCL were followed up for 5 years. The corrected visual acuity was compared between contact lens group and glasses group. The corneal endothelial changes were observed. The complications in cornea and conjunctiva were observed using slit

  18. PART II. HYDRATED CEMENTS

    Directory of Open Access Journals (Sweden)

    Milan Drabik

    2014-09-01

    Full Text Available Essential focus of the study has been to acquire thermoanalytical events, incl. enthalpies of decompositions - ΔH, of technological materials based on two types of Portland cements. The values of thermoanalytical events and also ΔH of probes of technological compositions, if related with the data of a choice of minerals of calcium-silicate-sulfate-aluminate hydrates, served as a valued input for the assessment of phases present and phase changes due to the topical hydraulic processes. The results indicate mainly the effects of "standard humidity" or "wet storage" of the entire hydration/hydraulic treatment, but also the presence of cement residues alongside calcium-silicate-sulfate-aluminate hydrates (during the tested period of treatment. "A diluting" effect of unhydrated cement residues upon the values of decomposition enthalpies in the studied multiphase system is postulated and discussed

  19. Formation of porous gas hydrates

    CERN Document Server

    Salamatin, Andrey N

    2015-01-01

    Gas hydrates grown at gas-ice interfaces are examined by electron microscopy and found to have a submicron porous texture. Permeability of the intervening hydrate layers provides the connection between the two counterparts (gas and water molecules) of the clathration reaction and makes further hydrate formation possible. The study is focused on phenomenological description of principal stages and rate-limiting processes that control the kinetics of the porous gas hydrate crystal growth from ice powders. Although the detailed physical mechanisms involved in the porous hydrate formation still are not fully understood, the initial stage of hydrate film spreading over the ice surface should be distinguished from the subsequent stage which is presumably limited by the clathration reaction at the ice-hydrate interface and develops after the ice grain coating is finished. The model reveals a time dependence of the reaction degree essentially different from that when the rate-limiting step of the hydrate formation at...

  20. Study on Joule Heat of Molten Steel in Soft-contact Billet Mold%方坯软接触结晶器内钢液焦耳热场研究

    Institute of Scientific and Technical Information of China (English)

    王杏娟; 刘然; 朱立光; 贾相明

    2013-01-01

    Based on the theory of electromagnetics and heat transfer,a three demensional finite element modle of molten steel magnetic field and temperature field were developed to investigate the joule heat distribution rule for molten steel in soft-contact billet mold.The results showed that a certain amount of joule heat existed in molten steel external surface,the skin layer thickness was about 10 mm (20 kHz,640 A).The joule heat increased with power frequency increased,and the growing rate decreased when power frequency higher than 40 kHz,but the joule heat was being scaled up with current intensity increased.%基于电磁学和传热学理论,针对结晶器内钢液,建立方坯软接触电磁连铸结晶器内电磁场和温度场的数学模型,利用有限元软件模拟了结晶器内钢液的电磁场和焦耳热场.结果发现:电源频率为20 kHz,电流强度为640A时,结晶器内钢液外表面因感应生成一定量的焦耳热,形成厚度约10mm“集肤层”.焦耳热随电源频率增加而增大,频率高于40 kHz后增幅减小,但焦耳热随电流强度增加呈正比例增大关系.

  1. A clinical study of bandage soft contact lenses used as in Astigmatism%绷带型软性角膜接触镜对外伤性散光的应用研究

    Institute of Scientific and Technical Information of China (English)

    姜海峰; 张旭永; 姜慧君; 姜丽君

    2015-01-01

    目的 评价角膜穿通伤术后的患者配戴绷带型软性角膜接触镜对术后存在的角膜散光矫正的疗效.方法 对2014~2015年间入院行角膜穿通伤术后的患者54例54只眼,根据随机分为对照组(22例22只眼)和观察组(32例32只眼),观察组术后第二天即配戴绷带型软性角膜接触镜,持续21天,两组分别于术后第1天、第2天、第3天、第7天、第15天、30天、45天检查术眼裸眼视力(UC-VA)、最佳矫正视力(BCVA)、术后角膜散光及散光轴偏离情况.不同时间点的测量数据采用重复测量数据的方差分析,组间采用LSD检验.结果 对照组在术后各随访时间点的UCVA为平均(0.61±0.21,63)%≥0.5,41% ≥0.8,BCVA平均为(0.71 ±0.23,72)%≥0.5,60% ≥0.8.前15天角膜散光平均(3.64±1.34)D,30天散光平均(3.25±1.52)D,45天散光平均(2.87±1.43)D,散光轴位偏离为(3.65±1.79)°观察组在术后各随访时间点的UCVA平均为(0.73±0.25,85)%≥0.5,68%≥0.8,BC-VA平均为0.83±0.27,93%≥0.5,84% ≥0.8.前15天角膜散光平均(3.02±1.62)D,30天散光平均(2.37±1.63)D,45天散光平均(1.87±1.72)D,散光轴位偏离为(3.76±1.32)°.观察组散光均低于对照组,两组差异有统计学意义(P <0.001).结论 绷带型软性角膜接触镜对预防角膜穿通伤造成的散光及降低散光度数有有效、安全、简便的作用.%Objective To evaluate the effect of comeal penetrating injured patients who wear bandage soft contact lens for the therapy of postoperative corneal astigmatism correction.Methods Randomly divided the patients admitted corneal penetrating injury operation (54 cases 54 eye) between 2014 to 2015 into control group (22 cases 22 eye) and observation group (32 cases 32 eye),observation group wear bandages soft corneal contact lens second day after operation,continued for 21 days,two groups respectively check operation naked eye vision (UCVA),and best correction vision (BCVA

  2. Soft Drop

    CERN Document Server

    Larkoski, Andrew J; Soyez, Gregory; Thaler, Jesse

    2014-01-01

    We introduce a new jet substructure technique called "soft drop declustering", which recursively removes soft wide-angle radiation from a jet. The soft drop algorithm depends on two parameters--a soft threshold $z_\\text{cut}$ and an angular exponent $\\beta$--with the $\\beta = 0$ limit corresponding roughly to the (modified) mass drop procedure. To gain an analytic understanding of soft drop and highlight the $\\beta$ dependence, we perform resummed calculations for three observables on soft-dropped jets: the energy correlation functions, the groomed jet radius, and the energy loss due to soft drop. The $\\beta = 0$ limit of the energy loss is particularly interesting, since it is not only "Sudakov safe" but also largely insensitive to the value of the strong coupling constant. While our calculations are strictly accurate only to modified leading-logarithmic order, we also include a discussion of higher-order effects such as multiple emissions and (the absence of) non-global logarithms. We compare our analytic r...

  3. [Hydration in clinical practice].

    Science.gov (United States)

    Maristany, Cleofé Pérez-Portabella; Segurola Gurruchaga, Hegoi

    2011-01-01

    Water is an essential foundation for life, having both a regulatory and structural function. The former results from active and passive participation in all metabolic reactions, and its role in conserving and maintaining body temperature. Structurally speaking it is the major contributer to tissue mass, accounting for 60% of the basis of blood plasma, intracellular and intersticial fluid. Water is also part of the primary structures of life such as genetic material or proteins. Therefore, it is necessary that the nurse makes an early assessment of patients water needs to detect if there are signs of electrolyte imbalance. Dehydration can be a very serious problem, especially in children and the elderly. Dehydrations treatment with oral rehydration solution decreases the risk of developing hydration disorders, but even so, it is recommended to follow preventive measures to reduce the incidence and severity of dehydration. The key to having a proper hydration is prevention. Artificial nutrition encompasses the need for precise calculation of water needs in enteral nutrition as parenteral, so the nurse should be part of this process and use the tools for calculating the patient's requirements. All this helps to ensure an optimal nutritional status in patients at risk. Ethical dilemmas are becoming increasingly common in clinical practice. On the subject of artificial nutrition and hydration, there isn't yet any unanimous agreement regarding hydration as a basic care. It is necessary to take decisions in consensus with the health team, always thinking of the best interests of the patient.

  4. Language Contact.

    Science.gov (United States)

    Nelde, Peter Hans

    1995-01-01

    Examines the phenomenon of language contact and recent trends in linguistic contact research, which focuses on language use, language users, and language spheres. Also discusses the role of linguistic and cultural conflicts in language contact situations. (13 references) (MDM)

  5. Structure and Hydration of Highly Branched, Monodisperse Phytoglycogen Nanoparticles

    Science.gov (United States)

    Atkinson, John; Nickels, Jonathan; Stanley, Christopher; Diallo, Souleymane; Katsaras, John; Dutcher, John

    Monodisperse phytoglycogen nanoparticles are a promising, new soft colloidal nanomaterial with many applications in the personal care, food, nutraceutical and pharmaceutical industries. These applications rely on exceptional properties that emerge from the highly branched structure of phytoglycogen and its interaction with water, such as extraordinarily high water retention, and low viscosity and exceptional stability in water. The structure and hydration of the nanoparticles was characterized using small angle neutron scattering (SANS) and quasielastic neutron scattering (QENS). SANS allowed us to determine the size of the nanoparticles, evaluate their radial density profile, quantify the particle-to-particle spacing, and determine their water content. The results show clearly that the nanoparticles are highly hydrated, with each nanoparticle containing 250% of its mass in water, and that aqueous dispersions approach a jamming transition at ~ 25% (w/w). QENS experiments provided an independent and consistent measure of the high level of hydration of the particles.

  6. Drugs Approved for Soft Tissue Sarcoma

    Science.gov (United States)

    ... 2015 2014 2013 2012 Media Resources Media Contacts Multicultural Media ... This page lists cancer drugs approved by the Food and Drug Administration (FDA) for soft tissue sarcoma. The list includes ...

  7. Parametric study of the physical properties of hydrate-bearing sand, silt, and clay sediments: 2. Small-strain mechanical properties

    Science.gov (United States)

    Lee, J. Y.; Francisca, F. M.; Santamarina, J. C.; Ruppel, C.

    2010-11-01

    The small-strain mechanical properties (e.g., seismic velocities) of hydrate-bearing sediments measured under laboratory conditions provide reference values for calibration of logging and seismic exploration results acquired in hydrate-bearing formations. Instrumented cells were designed for measuring the compressional (P) and shear (S) velocities of sand, silts, and clay with and without hydrate and subject to vertical effective stresses of 0.01 to 2 MPa. Tetrahydrofuran (THF), which is fully miscible in water, was used as the hydrate former to permit close control over the hydrate saturation Shyd and to produce hydrate from dissolved phase, as methane hydrate forms in most natural marine settings. The results demonstrate that laboratory hydrate formation technique controls the pattern of P and S velocity changes with increasing Shyd and that the small-strain properties of hydrate-bearing sediments are governed by effective stress, σ'v and sediment specific surface. The S velocity increases with hydrate saturation owing to an increase in skeletal shear stiffness, particularly when hydrate saturation exceeds Shyd≈ 0.4. At very high hydrate saturations, the small strain shear stiffness is determined by the presence of hydrates and becomes insensitive to changes in effective stress. The P velocity increases with hydrate saturation due to the increases in both the shear modulus of the skeleton and the bulk modulus of pore-filling phases during fluid-to-hydrate conversion. Small-strain Poisson's ratio varies from 0.5 in soft sediments lacking hydrates to 0.25 in stiff sediments (i.e., subject to high vertical effective stress or having high Shyd). At Shyd ≥ 0.5, hydrate hinders expansion and the loss of sediment stiffness during reduction of vertical effective stress, meaning that hydrate-rich natural sediments obtained through pressure coring should retain their in situ fabric for some time after core retrieval if the cores are maintained within the hydrate

  8. Modeling Hydrates and the Gas Hydrate Markup Language

    Directory of Open Access Journals (Sweden)

    Weihua Wang

    2007-06-01

    Full Text Available Natural gas hydrates, as an important potential fuels, flow assurance hazards, and possible factors initiating the submarine geo-hazard and global climate change, have attracted the interest of scientists all over the world. After two centuries of hydrate research, a great amount of scientific data on gas hydrates has been accumulated. Therefore the means to manage, share, and exchange these data have become an urgent task. At present, metadata (Markup Language is recognized as one of the most efficient ways to facilitate data management, storage, integration, exchange, discovery and retrieval. Therefore the CODATA Gas Hydrate Data Task Group proposed and specified Gas Hydrate Markup Language (GHML as an extensible conceptual metadata model to characterize the features of data on gas hydrate. This article introduces the details of modeling portion of GHML.

  9. Overview: Nucleation of clathrate hydrates

    Science.gov (United States)

    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.

  10. A study on gas hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Byoung Jae; Jung, Tae Jin; Sunwoo, Don [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)

    1996-12-01

    Sufficient documents were reviewed to understand solid components of water and gaseous hydrocarbon known as gas hydrates, which represent an important potential energy resource of the future. The review provides us with valuable information on crystal structures, kinetics, origin and distribution of gas hydrates. In addition, the review increased our knowledge of exploration and development methods of gas hydrates. Large amounts of methane, the principal component of natural gas, in the form of solid gas hydrate are found mainly offshore in outer continental margin sediment and, to a lesser extent, in polar regions commonly associated with permafrost. Natural gas hydrates are stable in some environments where the hydrostatic pressure exerted by overlying water column is sufficient for hydrate formation and stability. The required high pressures generally restrict gas hydrate to sediments beneath water of approximately 400 m. Higher sediment temperatures at greater subbottom depths destabilize gas hydrates. Based on the pressure- temperature condition, the outer continental margin of East Sea where water depth is deep enough to form gas hydrate is considered to have high potential of gas hydrate accumulations. (author). 56 refs., tabs., figs.

  11. Nonequilibrium adiabatic molecular dynamics simulations of methane clathrate hydrate decomposition

    Science.gov (United States)

    Alavi, Saman; Ripmeester, J. A.

    2010-04-01

    Nonequilibrium, constant energy, constant volume (NVE) molecular dynamics simulations are used to study the decomposition of methane clathrate hydrate in contact with water. Under adiabatic conditions, the rate of methane clathrate decomposition is affected by heat and mass transfer arising from the breakup of the clathrate hydrate framework and release of the methane gas at the solid-liquid interface and diffusion of methane through water. We observe that temperature gradients are established between the clathrate and solution phases as a result of the endothermic clathrate decomposition process and this factor must be considered when modeling the decomposition process. Additionally we observe that clathrate decomposition does not occur gradually with breakup of individual cages, but rather in a concerted fashion with rows of structure I cages parallel to the interface decomposing simultaneously. Due to the concerted breakup of layers of the hydrate, large amounts of methane gas are released near the surface which can form bubbles that will greatly affect the rate of mass transfer near the surface of the clathrate phase. The effects of these phenomena on the rate of methane hydrate decomposition are determined and implications on hydrate dissociation in natural methane hydrate reservoirs are discussed.

  12. Drilling Gas Hydrates on hydrate Ridge, Oregon continental margin

    Science.gov (United States)

    Trehu, A. M.; Bohrmann, G.; Leg 204 Science Party

    2002-12-01

    During Leg 204, we cored and logged 9 sites on the Oregon continental margin to determine the distribution and concentration of gas hydrates in an accretionary ridge and adjacent slope basin, investigate the mechanisms that transport methane and other gases into the gas hydrate stability zone (GHSZ), and obtain constraints on physical properties of hydrates in situ. A 3D seismic survey conducted in 2000 provided images of potential subsurface fluid conduits and indicated the position of the GHSZ throughout the survey region. After coring the first site, we acquired Logging-While-Drilling (LWD) data at all but one site to provide an overview of downhole physical properties. The LWD data confirmed the general position of key seismic stratigraphic horizons and yielded an initial estimate of hydrate concentration through the proxy of in situ electrical resistivity. These records proved to be of great value in planning subsequent coring. The second new hydrate proxy to be tested was infrared thermal imaging of cores on the catwalk as rapidly as possible after retrieval. The thermal images were used to identify hydrate samples and to estimate the distribution and texture of hydrate within the cores. Geochemical analyses of interstitial waters and of headspace and void gases provide additional information on the distribution and concentration of hydrate within the stability zone, the origin and pathway of fluids into and through the GHSZ, and the rates at which gas hydrate is forming. Bio- and lithostratigraphic description of cores, measurement of physical properties, and in situ pressure core sampling and thermal measurements complement the data set, providing ground-truth tests of inferred physical and sedimentological properties. Among the most interesting preliminary results are: 1) that gas hydrates are distributed through a broad depth range within the GHSZ and that different physical and chemical proxies for hydrate distribution and concentration give generally

  13. Rapid gas hydrate formation process

    Science.gov (United States)

    Brown, Thomas D.; Taylor, Charles E.; Unione, Alfred J.

    2013-01-15

    The disclosure provides a method and apparatus for forming gas hydrates from a two-phase mixture of water and a hydrate forming gas. The two-phase mixture is created in a mixing zone which may be wholly included within the body of a spray nozzle. The two-phase mixture is subsequently sprayed into a reaction zone, where the reaction zone is under pressure and temperature conditions suitable for formation of the gas hydrate. The reaction zone pressure is less than the mixing zone pressure so that expansion of the hydrate-forming gas in the mixture provides a degree of cooling by the Joule-Thompson effect and provides more intimate mixing between the water and the hydrate-forming gas. The result of the process is the formation of gas hydrates continuously and with a greatly reduced induction time. An apparatus for conduct of the method is further provided.

  14. Soft Clouding

    DEFF Research Database (Denmark)

    Søndergaard, Morten; Markussen, Thomas; Wetton, Barnabas;

    2012-01-01

    Soft Clouding is a blended concept, which describes the aim of a collaborative and transdisciplinary project. The concept is a metaphor implying a blend of cognitive, embodied interaction and semantic web. Furthermore, it is a metaphor describing our attempt of curating a new semantics of sound...

  15. Examination of Hydrate Formation Methods: Trying to Create Representative Samples

    Energy Technology Data Exchange (ETDEWEB)

    Kneafsey, T.J.; Rees, E.V.L.; Nakagawa, S.; Kwon, T.-H.

    2011-04-01

    Forming representative gas hydrate-bearing laboratory samples is important so that the properties of these materials may be measured, while controlling the composition and other variables. Natural samples are rare, and have often experienced pressure and temperature changes that may affect the property to be measured [Waite et al., 2008]. Forming methane hydrate samples in the laboratory has been done a number of ways, each having advantages and disadvantages. The ice-to-hydrate method [Stern et al., 1996], contacts melting ice with methane at the appropriate pressure to form hydrate. The hydrate can then be crushed and mixed with mineral grains under controlled conditions, and then compacted to create laboratory samples of methane hydrate in a mineral medium. The hydrate in these samples will be part of the load-bearing frame of the medium. In the excess gas method [Handa and Stupin, 1992], water is distributed throughout a mineral medium (e.g. packed moist sand, drained sand, moistened silica gel, other porous media) and the mixture is brought to hydrate-stable conditions (chilled and pressurized with gas), allowing hydrate to form. This method typically produces grain-cementing hydrate from pendular water in sand [Waite et al., 2004]. In the dissolved gas method [Tohidi et al., 2002], water with sufficient dissolved guest molecules is brought to hydrate-stable conditions where hydrate forms. In the laboratory, this is can be done by pre-dissolving the gas of interest in water and then introducing it to the sample under the appropriate conditions. With this method, it is easier to form hydrate from more soluble gases such as carbon dioxide. It is thought that this method more closely simulates the way most natural gas hydrate has formed. Laboratory implementation, however, is difficult, and sample formation is prohibitively time consuming [Minagawa et al., 2005; Spangenberg and Kulenkampff, 2005]. In another version of this technique, a specified quantity of gas

  16. Conjunctival impression cytology in contact lens wearers.

    Directory of Open Access Journals (Sweden)

    Simon Priya

    2002-01-01

    Full Text Available PURPOSE: To evaluate the cytological changes in conjunctiva following regular contact lens wear and to determine the correlation, if any, between severity of cytological alteration and symptoms related to contact lens wear. METHODS: One hundred eyes (50 normal asymptomatic subjects who served as a control group were studied by conjunctival impression cytology (CIC. These subjects were fitted with rigid gas permeable (RGP or soft contact lenses and were followed up at the end of 3 and 6 months. At each follow-up visit the CIC was repeated. A filter paper with the impression specimen was stained with periodic acid schiff (PAS and haematoxylin stain to study goblet cell loss. Papanicolaou stain was done to study squamous metaplasia. The cytological changes were graded using the system described by Natadisastra et al. RESULTS: Severity of cytological changes increased with the duration of contact lens wear (P = 0.00001. At the end of 6 months, 60% of symptomatic eyes wearing soft contact lens and RGP lens showed abnormal CIC changes. None of the asymptomatic RGP contact lens wearing eyes showed abnormal CIC changes whereas 33.4% of the asymptomatic soft contact lens wearing eyes showed abnormal CIC changes (P = 0.033. Epithelial changes occurred within 3-6 months of contact lens fitting. CONCLUSION: Severity of cytological changes increased with duration of lens wear (P = 0.00001. Prevalence and severity of cytological alteration is more in symptomatic contact lens wearers. Soft contact lens wearers although asymptomatic showed severe CIC changes.

  17. Nanoparticle-Laden Contact Lens for Controlled Ocular Delivery of Prednisolone: Formulation Optimization Using Statistical Experimental Design

    Directory of Open Access Journals (Sweden)

    Amr ElShaer

    2016-04-01

    Full Text Available Human eye is one of the most accessible organs in the body, nonetheless, its physiology and associated precorneal factors such as nasolacrimal drainage, blinking, tear film, tear turnover, and induced lacrimation has significantly decreased the residence time of any foreign substances including pharmaceutical dosage forms. Soft contact lenses are promising delivery devices that can sustain the drug release and prolong residence time by acting as a geometric barrier to drug diffusion to tear fluid. This study investigates experimental parameters such as composition of polymer mixtures, stabilizer and the amount of active pharmaceutical ingredient on the preparation of a polymeric drug delivery system for the topical ocular administration of Prednisolone. To achieve this goal, prednisolone-loaded poly (lactic-co-glycolic acid (PLGA nanoparticles were prepared by single emulsion solvent evaporation method. Prednisolone was quantified using a validated high performance liquid chromatography (HPLC method. Nanoparticle size was mostly affected by the amount of co-polymer (PLGA used whereas drug load was mostly affected by amount of prednisolone (API used. Longer homogenization time along with higher amount of API yielded the smallest size nanoparticles. The nanoparticles prepared had an average particle size of 347.1 ± 11.9 nm with a polydispersity index of 0.081. The nanoparticles were then incorporated in the contact lens mixture before preparing them. Clear and transparent contact lenses were successfully prepared. When the nanoparticle (NP-loaded contact lenses were compared with control contact lenses (unloaded NP contact lenses, a decrease in hydration by 2% (31.2% ± 1.25% hydration for the 0.2 g loaded NP contact lenses and light transmission by 8% (unloaded NP contact lenses 94.5% NP 0.2 g incorporated contact lenses 86.23%. The wettability of the contact lenses remained within the desired value (<90 °C even upon incorporation of the NP. NP

  18. Hydration and physical performance.

    Science.gov (United States)

    Murray, Bob

    2007-10-01

    There is a rich scientific literature regarding hydration status and physical function that began in the late 1800s, although the relationship was likely apparent centuries before that. A decrease in body water from normal levels (often referred to as dehydration or hypohydration) provokes changes in cardiovascular, thermoregulatory, metabolic, and central nervous function that become increasingly greater as dehydration worsens. Similarly, performance impairment often reported with modest dehydration (e.g., -2% body mass) is also exacerbated by greater fluid loss. Dehydration during physical activity in the heat provokes greater performance decrements than similar activity in cooler conditions, a difference thought to be due, at least in part, to greater cardiovascular and thermoregulatory strain associated with heat exposure. There is little doubt that performance during prolonged, continuous exercise in the heat is impaired by levels of dehydration >or= -2% body mass, and there is some evidence that lower levels of dehydration can also impair performance even during relatively short-duration, intermittent exercise. Although additional research is needed to more fully understand low-level dehydration's effects on physical performance, one can generalize that when performance is at stake, it is better to be well-hydrated than dehydrated. This generalization holds true in the occupational, military, and sports settings.

  19. Ductile flow of methane hydrate

    Science.gov (United States)

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

    2003-01-01

    Compressional creep tests (i.e., constant applied stress) conducted on pure, polycrystalline methane hydrate over the temperature range 260-287 K and confining pressures of 50-100 MPa show this material to be extraordinarily strong compared to other icy compounds. The contrast with hexagonal water ice, sometimes used as a proxy for gas hydrate properties, is impressive: over the thermal range where both are solid, methane hydrate is as much as 40 times stronger than ice at a given strain rate. The specific mechanical response of naturally occurring methane hydrate in sediments to environmental changes is expected to be dependent on the distribution of the hydrate phase within the formation - whether arranged structurally between and (or) cementing sediments grains versus passively in pore space within a sediment framework. If hydrate is in the former mode, the very high strength of methane hydrate implies a significantly greater strain-energy release upon decomposition and subsequent failure of hydrate-cemented formations than previously expected.

  20. Some thermodynamical aspects of protein hydration water

    Energy Technology Data Exchange (ETDEWEB)

    Mallamace, Francesco, E-mail: francesco.mallamace@unime.it [Dipartimento di Fisica e Scienze della Terra, Università di Messina and CNISM, I-98168 Messina (Italy); Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States); Corsaro, Carmelo [Dipartimento di Fisica e Scienze della Terra, Università di Messina and CNISM, I-98168 Messina (Italy); CNR-IPCF, Viale F. Stagno D’Alcontres 37, I-98158 Messina (Italy); Mallamace, Domenico [Dipartimento SASTAS, Università di Messina, I-98166 Messina (Italy); Vasi, Sebastiano [Dipartimento di Fisica e Scienze della Terra, Università di Messina and CNISM, I-98168 Messina (Italy); Vasi, Cirino [CNR-IPCF, Viale F. Stagno D’Alcontres 37, I-98158 Messina (Italy); Stanley, H. Eugene [Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States); Chen, Sow-Hsin [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2015-06-07

    We study by means of nuclear magnetic resonance the self-diffusion of protein hydration water at different hydration levels across a large temperature range that includes the deeply supercooled regime. Starting with a single hydration shell (h = 0.3), we consider different hydrations up to h = 0.65. Our experimental evidence indicates that two phenomena play a significant role in the dynamics of protein hydration water: (i) the measured fragile-to-strong dynamic crossover temperature is unaffected by the hydration level and (ii) the first hydration shell remains liquid at all hydrations, even at the lowest temperature.

  1. Silica surfaces lubrication by hydrated cations adsorption from electrolyte solutions.

    Science.gov (United States)

    Donose, Bogdan C; Vakarelski, Ivan U; Higashitani, Ko

    2005-03-01

    Adsorption of hydrated cations on hydrophilic surfaces has been related to a variety of phenomena associated with the short-range interaction forces and mechanisms of the adhesive contact between the surfaces. Here we have investigated the effect of the adsorption of cations on the lateral interaction. Using lateral force microscopy (LFM), we have measured the friction force between a silica particle and silica wafer in pure water and in electrolyte solutions of LiCl, NaCl, and CsCl salts. A significant lubrication effect was demonstrated for solutions of high electrolyte concentrations. It was found that the adsorbed layers of smaller and more hydrated cations have a higher lubrication capacity than the layers of larger and less hydrated cations. Additionally, we have demonstrated a characteristic dependence of the friction force on the sliding velocity of surfaces. A mechanism for the observed phenomena based on the microstructures of the adsorbed layers is proposed.

  2. Thermal conductivity measurements in Porous mixtures of methane hydrate and quartz sand

    Science.gov (United States)

    Waite, W.F.; deMartin, B.J.; Kirby, S.H.; Pinkston, J.; Ruppel, C.D.

    2002-01-01

    Using von Herzen and Maxwell's needle probe method, we measured thermal conductivity in four porous mixtures of quartz sand and methane gas hydrate, with hydrate composing 0, 33, 67 and 100% of the solid volume. Thermal conductivities were measured at a constant methane pore pressure of 24.8 MPa between -20 and +15??C, and at a constant temperature of -10??C between 3.5 and 27.6 MPa methane pore pressure. Thermal conductivity decreased with increasing temperature and increased with increasing methane pore pressure. Both dependencies weakened with increasing hydrate content. Despite the high thermal conductivity of quartz relative to methane hydrate, the largest thermal conductivity was measured in the mixture containing 33% hydrate rather than in hydrate-free sand. This suggests gas hydrate enhanced grain-to-grain heat transfer, perhaps due to intergranular contact growth during hydrate synthesis. These results for gas-filled porous mixtures can help constrain thermal conductivity estimates in porous, gas hydrate-bearing systems.

  3. Using Carbon Dioxide to Enhance Recovery of Methane from Gas Hydrate Reservoirs: Final Summary Report

    Energy Technology Data Exchange (ETDEWEB)

    McGrail, B. Peter; Schaef, Herbert T.; White, Mark D.; Zhu, Tao; Kulkarni, Abhijeet S.; Hunter, Robert B.; Patil, Shirish L.; Owen, Antionette T.; Martin, P F.

    2007-09-01

    Carbon dioxide sequestration coupled with hydrocarbon resource recovery is often economically attractive. Use of CO2 for enhanced recovery of oil, conventional natural gas, and coal-bed methane are in various stages of common practice. In this report, we discuss a new technique utilizing CO2 for enhanced recovery of an unconventional but potentially very important source of natural gas, gas hydrate. We have focused our attention on the Alaska North Slope where approximately 640 Tcf of natural gas reserves in the form of gas hydrate have been identified. Alaska is also unique in that potential future CO2 sources are nearby, and petroleum infrastructure exists or is being planned that could bring the produced gas to market or for use locally. The EGHR (Enhanced Gas Hydrate Recovery) concept takes advantage of the physical and thermodynamic properties of mixtures in the H2O-CO2 system combined with controlled multiphase flow, heat, and mass transport processes in hydrate-bearing porous media. A chemical-free method is used to deliver a LCO2-Lw microemulsion into the gas hydrate bearing porous medium. The microemulsion is injected at a temperature higher than the stability point of methane hydrate, which upon contacting the methane hydrate decomposes its crystalline lattice and releases the enclathrated gas. Small scale column experiments show injection of the emulsion into a CH4 hydrate rich sand results in the release of CH4 gas and the formation of CO2 hydrate

  4. Flow assurance intervention, hydrates remediation

    Energy Technology Data Exchange (ETDEWEB)

    Mancini, Christopher S. [Oceaneering International Inc., Houston, TX (United States)

    2012-07-01

    This paper addresses the issues of removing hydrates in sub sea flow lines and associated equipment with an Remotely Operated Vehicle (ROV) of opportunity and a multi-service-vessel (MSV). The paper is split into three topics: the equipment used with the ROV, assessing the interface points and handling fluids produced from drawing down the pressure. Each section is explained thoroughly and backed up with real world experience. The equipment section details information from actual jobs performed and why the particular components were utilized. The system is generally contained in an ROV mounted skid. Pumps are utilized to draw down the pressure inside the hydrated section of equipment, removing one of the three necessary components for hydrates formation. Once the section is pumped down, several options exist for handling the fluids pumped out of the system: pumping to surface, re-injection into the well, or injection into an operating flow line. This method of hydrates remediation is both economical and timely. Hydrate blockages form in low temperatures and high pressures. Reducing the pressure or increasing the temperature so the conditions lie to the right of the hydrate dissociation curve will slowly decompose the blockage. Depressurization and the use of MEG or methanol will give favorable conditions to remove the hydrate plug. Oceaneering has the capabilities to remove hydrates using the FRS in conjunction with an installation vessel to dispose of the gas and fluid removed from the flow line. Hydrate remediation techniques should be implemented into the initial design to reduce costs later. The cost of stopped production combined with the day rate for equipment needed for hydrate removal outweighs the costs if no technique is utilized. (author)

  5. Tear exchange and contact lenses: a review.

    Science.gov (United States)

    Muntz, Alex; Subbaraman, Lakshman N; Sorbara, Luigina; Jones, Lyndon

    2015-01-01

    Tear exchange beneath a contact lens facilitates ongoing fluid replenishment between the ocular surface and the lens. This exchange is considerably lower during the wear of soft lenses compared with rigid lenses. As a result, the accumulation of tear film debris and metabolic by-products between the cornea and a soft contact lens increases, potentially leading to complications. Lens design innovations have been proposed, but no substantial improvement in soft lens tear exchange has been reported. Researchers have determined post-lens tear exchange using several methods, notably fluorophotometry. However, due to technological limitations, little remains known about tear hydrodynamics around the lens and, to-date, true tear exchange with contact lenses has not been shown. Further knowledge regarding tear exchange could be vital in aiding better contact lens design, with the prospect of alleviating certain adverse ocular responses. This article reviews the literature to-date on the significance, implications and measurement of tear exchange with contact lenses.

  6. Investigation on Gas Storage in Methane Hydrate

    Institute of Scientific and Technical Information of China (English)

    Zhigao Sun; Rongsheng Ma; Shuanshi Fan; Kaihua Guo; Ruzhu Wang

    2004-01-01

    The effect of additives (anionic surfactant sodium dodecyl sulfate (SDS), nonionic surfactant alkyl polysaccharide glycoside (APG), and liquid hydrocarbon cyclopentane (CP)) on hydrate induction time and formation rate, and storage capacity was studied in this work. Micelle surfactant solutions were found to reduce hydrate induction time, increase methane hydrate formation rate and improve methane storage capacity in hydrates. In the presence of surfactant, hydrate could form quickly in a quiescent system and the energy costs of hydrate formation were reduced. The critical micelle concentrations of SDS and APG water solutions were found to be 300× 10-6 and 500× 10-6 for methane hydrate formation system respectively. The effect of anionic surfactant (SDS) on methane storage in hydrates is more pronounced compared to a nonionic surfactant (APG). CP also reduced hydrate induction time and improved hydrate formation rate, but could not improve methane storage in hydrates.

  7. Soft Robotics Week

    CERN Document Server

    Rossiter, Jonathan; Iida, Fumiya; Cianchetti, Matteo; Margheri, Laura

    2017-01-01

    This book offers a comprehensive, timely snapshot of current research, technologies and applications of soft robotics. The different chapters, written by international experts across multiple fields of soft robotics, cover innovative systems and technologies for soft robot legged locomotion, soft robot manipulation, underwater soft robotics, biomimetic soft robotic platforms, plant-inspired soft robots, flying soft robots, soft robotics in surgery, as well as methods for their modeling and control. Based on the results of the second edition of the Soft Robotics Week, held on April 25 – 30, 2016, in Livorno, Italy, the book reports on the major research lines and novel technologies presented and discussed during the event.

  8. On the thermodynamical admissibility of the triphasic theory of charged hydrated tissues

    NARCIS (Netherlands)

    Huyghe, J.M.; Wilson, W.; Malakpoor, K.

    2009-01-01

    The triphasic theory on soft charged hydrated tissues (Lai, W. M., Hou, J. S., and Mow, V. C., 1991, "A Triphasic Theory for the Swelling and Deformation Behaviors of Articular Cartilage," ASME J. Biomech. Eng., 113, pp. 245-258) attributes the swelling propensity of articular cartilage to three dif

  9. Evaluation of Hydrated Lime Filler in Asphalt Mixtures

    Directory of Open Access Journals (Sweden)

    Mohammed Abbas Hasan Al-Jumaily

    2008-01-01

    Full Text Available Mineral filler is one of important materials and affecting on properties and quality of asphalt mixtures .There are different types of mineral filler depended on cost and quality , the matter encourages us to achieve this study to evaluate hydrated lime filler effects on properties of asphalt mixes related with strength and durability. Conventional asphaltic concrete mixtures with Portland cement and soft sandstone fillers and mixtures modified with hydrated lime were evaluated for their fundamental engineering properties as defined by Marshall properties , index of retained strength , indirect tensile strength , permanent deformation characteristics , and fatigue resistance .A typical dense graded mixture employed in construction of surface course pavement in Iraq in accordance with SCRB specifications was used .The materials used in this study included mineral aggregate materials (coarse and fine sizes were originally obtained from Najaf Sea quarries and two grades of asphalt cements produced from Daurah refinery which are D47 and D66 . The physical properties , stiffness modulus and chemical composition are evaluated for the recovered asphalt cement from prepared asphalt mixes containing various filler types .The paper results indicated that the addition of hydrated lime as mineral filler improved the permanent deformation characteristics and fatigue life and the use of hydrated lime will decrease the moisture susceptibility of the asphalt mixtures.

  10. Hydrates fighting tools; Des outils de lutte contre les hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    2003-04-01

    Shell Exploration and Production company (SEPCo) is the operator of the 'Popeye' deep offshore field in the Gulf of Mexico. Thanks to the introduction of a low dosing hydrates inhibitor (LDHI) elaborated by Shell Global Solutions, the company has added a 7.5 Gpc extra volume of gas to its recoverable reserves. This new technology avoids the plugging of pipes by hydrates formation. (J.S.)

  11. Obsidian Hydration: A New Paleothermometer

    Energy Technology Data Exchange (ETDEWEB)

    Anovitz, Lawrence {Larry} M [ORNL; Riciputi, Lee R [ORNL; Cole, David R [ORNL; Fayek, Mostafa [ORNL; Elam, J. Michael [University of Tennessee, Knoxville (UTK)

    2006-01-01

    The natural hydration of obsidian was first proposed as a dating technique for young geological and archaeological specimens by Friedman and Smith (1960), who noted that the thickness of the hydrated layer on obsidian artifacts increases with time. This approach is, however, sensitive to temperature and humidity under earth-surface conditions. This has made obsidian hydration dating more difficult, but potentially provides a unique tool for paleoclimatic reconstructions. In this paper we present the first successful application of this approach, based on combining laboratory-based experimental calibrations with archaeological samples from the Chalco site in the Basin of Mexico, dated using stratigraphically correlated 14C results and measuring hydration depths by secondary ion mass spectrometry. The resultant data suggest, first, that this approach is viable, even given the existing uncertainties, and that a cooling trend occurred in the Basin of Mexico over the past 1450 yr, a result corroborated by other paleoclimatic data.

  12. Obsidian hydration: A new paleothermometer

    Science.gov (United States)

    Anovitz, Lawrence M.; Riciputi, Lee R.; Cole, David R.; Fayek, Mostafa; Elam, J. Michael

    2006-07-01

    The natural hydration of obsidian was first proposed as a dating technique for young geological and archaeological specimens by Friedman and Smith (1960), who noted that the thickness of the hydrated layer on obsidian artifacts increases with time. This approach is, however, sensitive to temperature and humidity under earth-surface conditions. This has made obsidian hydration dating more difficult, but potentially provides a unique tool for paleoclimatic reconstructions. In this paper we present the first successful application of this approach, based on combining laboratory-based experimental calibrations with archaeological samples from the Chalco site in the Basin of Mexico, dated using stratigraphically correlated 14C results and measuring hydration depths by secondary ion mass spectrometry. The resultant data suggest, first, that this approach is viable, even given the existing uncertainties, and that a cooling trend occurred in the Basin of Mexico over the past 1450 yr, a result corroborated by other paleoclimatic data.

  13. Obsidian hydration dates glacial loading?

    Science.gov (United States)

    Friedman, I; Pierce, K L; Obradovich, J D; Long, W D

    1973-05-18

    Three different groups of hydration rinds have been measured on thin sections of obsidian from Obsidian Cliff, Yellowstone National Park, Wyoming. The average thickness of the thickest (oldest) group of hydration rinds is 16.3 micrometers and can be related to the original emplacement of the flow 176,000 years ago (potassium-argon age). In addition to these original surfaces, most thin sections show cracks and surfaces which have average hydration rind thicknesses of 14.5 and 7.9 micrometers. These later two hydration rinds compare closely in thickness with those on obsidian pebbles in the Bull Lake and Pinedale terminal moraines in the West Yellowstone Basin, which are 14 to 15 and 7 to 8 micrometers thick, respectively. The later cracks are thought to have been formed by glacial loading during the Bull Lake and Pinedale glaciations, when an estimated 800 meters of ice covered the Obsidian Cliff flow.

  14. Obituary--rigid contact lenses.

    Science.gov (United States)

    Efron, Nathan

    2010-10-01

    Scleral and corneal rigid lenses represented 100 per cent of the contact lens market immediately prior to the invention of soft lenses in the mid-1960s. In the United Kingdom today, rigid lenses comprise 2 per cent of all new lens fits. Low rates of rigid lens fitting are also apparent in 27 other countries which have recently been surveyed. Thus, the 1998 prediction of the author that rigid lenses--also referred to as 'rigid gas permeable' (RGP) lenses or 'gas permeable' (GP) lenses--would be obsolete by the year 2010 has essentially turned out to be correct. In this obituary, the author offers 10 reasons for the demise of rigid lens fitting: initial rigid lens discomfort; intractable rigid lens-induced corneal and lid pathology; extensive soft lens advertising; superior soft lens fitting logistics; lack of rigid lens training opportunities; redundancy of the rigid lens 'problem solver' function; improved soft toric and bifocal/varifocal lenses; limited uptake of orthokeratology; lack of investment in rigid lenses; and the emergence of aberration control soft lenses. Rigid lenses are now being fitted by a minority of practitioners with specialist skills/training. Certainly, rigid lenses can no longer be considered as a mainstream form of contact lens correction. May their dear souls (bulk properties) rest in peace.

  15. Multiaspect Soft Sets

    Directory of Open Access Journals (Sweden)

    Nor Hashimah Sulaiman

    2013-01-01

    Full Text Available We introduce a novel concept of multiaspect soft set which is an extension of the ordinary soft set by Molodtsov. Some basic concepts, operations, and properties of the multiaspect soft sets are studied. We also define a mapping on multiaspect soft classes and investigate several properties related to the images and preimages of multiaspect soft sets.

  16. Phase equilibria and thermodynamic modeling of ethane and propane hydrates in porous silica gels.

    Science.gov (United States)

    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.

  17. Structure of the ordered hydration of amino acids in proteins: analysis of crystal structures

    Energy Technology Data Exchange (ETDEWEB)

    Biedermannová, Lada, E-mail: lada.biedermannova@ibt.cas.cz; Schneider, Bohdan [Institute of Biotechnology CAS, Videnska 1083, 142 20 Prague (Czech Republic)

    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. The 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.

  18. Detection and context of hydrated mineralogy in the Tyrrhena Terra region, Mars

    Science.gov (United States)

    den Haan, J.; Zegers, T. E.; van Ruitenbeek, F. J. A.; van der Werff, H. M. A.; Rossi, A.

    2008-09-01

    Introduction The discovery of phyllosilicates on Mars [1] has had major implications on the perceived geologic and climatologic evolution of Mars [2]. Not only do phyllosilicates represent a `wet' period on Mars, they might also represent a potentially favorable environment for life. The phyllosilicates have so far exclusively been found in or close to ancient Noachian highland terrain. Those phyllosilicate deposits studied (e.g. [3]) show a clear association between hydrated mineralogy and heavily eroded and crater-saturated outcrops. Phyllosilicates on Earth are associated with a wide variety of geological processes (volcanism, metamorphism, hydrothermal alteration, sedimentation). The occurrence of phyllosilicates on Mars may be equally diverse in nature. To be able to place constraints on the early Martian environment, the processes by which these phyllosilicates formed need to be reconstructed. To derive this information from individual phyllosilicate deposits, it is necessary to interpret their composition in relation to their geological context and relative time relationships. We conducted such an integrated hyperspectral and geological study of the Tyrrhena Terra region. Data products ad methods HRSC data products (both image at 12 m/pixel and stereo-derived DTMs) are used for examining geologic cross-cutting relationships, geomorphologic landforms and visual determination of unit boundaries. Odyssey THEMIS nighttime TIR images are analyzed for spatial variations in thermal inertia. Where available, HRSC is supplemented by higher-resolution visible observations of CTX or MOC. Hyperspectral analysis is conducted using data from the OMEGA hyperspectral instrument. In order to batch-process large amounts of OMEGA data, an IDL/ENVI tool was developed on top of the existing SOFT04, distributed by PSA. The applied atmospheric correction assumes that atmospheric contributions are multiplicative, and follow a power-law distribution with altitude [4]. The ratio of

  19. Airway Hydration and COPD

    Science.gov (United States)

    Ghosh, Arunava; Boucher, R.C.; Tarran, Robert

    2015-01-01

    Chronic obstructive pulmonary disease (COPD) is one of the prevalent causes of worldwide mortality and encompasses two major clinical phenotypes, i.e., chronic bronchitis (CB) and emphysema. The most common cause of COPD is chronic tobacco inhalation. Research focused on the chronic bronchitic phenotype of COPD has identified several pathological processes that drive disease initiation and progression. For example, the lung’s mucociliary clearance (MCC) system performs the critical task of clearing inhaled pathogens and toxic materials from the lung. MCC efficiency is dependent on: (i) the ability of apical plasma membrane ion channels such as the cystic fibrosis transmembrane conductance regulator (CFTR) and the epithelial Na+ channel (ENaC) to maintain airway hydration; (ii) ciliary beating; and, (iii) appropriate rates of mucin secretion. Each of these components is impaired in CB and likely contributes to the mucus stasis/accumulation seen in CB patients. This review highlights the cellular components responsible for maintaining MCC and how this process is disrupted following tobacco exposure and with CB. We shall also discuss existing therapeutic strategies for the treatment of chronic bronchitis and how components of the MCC can be used as biomarkers for the evaluation of tobacco or tobacco-like-product exposure. PMID:26068443

  20. Mechanism of gypsum hydration

    Directory of Open Access Journals (Sweden)

    Pacheco, G.

    1991-06-01

    Full Text Available There is an hypothesis that the mechanism o f gypsum hydration and dehydration is performed through two simultaneous phenomena. In this study we try to clear up this phenomenon using chlorides as accelerators or a mixture of ethanol-methanol as retarders to carry out the gypsum setting. Natural Mexican gypsum samples and a hemihydrate prepared in the laboratory are used. The following analytical techniques are used: MO, DRX, DTA, TG and DTG. In agreement with the obtained results, it can be concluded: that colloid formation depends on the action of accelerators or retarders and the crystals are a consequence of the quantity of hemihydrate formed.

    En el mecanismo de hidratación y deshidratación del yeso existe la hipótesis de que éste se efectúa por dos fenómenos simultáneos. Este estudio intenta esclarecer estos fenómenos, empleando: cloruros como aceleradores o mezcla etanol-metanol como retardadores para efectuar el fraguado del yeso. Se emplean muestras de yeso de origen natural mexicano y hemihydrate preparado en laboratorio; se utilizan técnicas analíticas: MO, DRX, DTA, TG y DTG. De acuerdo a los resultados obtenidos se puede deducir: que la formación del coloide depende de la acción de los agentes aceleradores o retardadores y que los cristales son consecuencia de la cantidad de hemihidrato formado.

  1. A Sea Floor Methane Hydrate Displacement Experiment Using N2 Gas

    Science.gov (United States)

    Brewer, P. G.; Peltzer, E. T.; Walz, P. M.; Zhang, X.; Hester, K.

    2009-12-01

    The production of free methane gas from solid methane hydrate accumulations presents a considerable challenge. The presently preferred procedure is pressure reduction whereby the relief of pressure to a condition outside the hydrate phase boundary creates a gas phase. The reaction is endothermic and thus a problematic water ice phase can form if the extraction of gas is too rapid, limiting the applicability of this procedure. Additionally, the removal of the formation water in contact with the hydrate phase is required before meaningful pressure reduction can be attained -- and this can take time. An alternate approach that has been suggested is the injection of liquid CO2 into the formation, thereby displacing the formation water. Formation of a solid CO2 hydrate is thermodynamically favored under these conditions. Competition between CH4 and CO2 for the hydrate host water molecules can occur displacing CH4 from the solid to the gas phase with formation of a solid CO2 hydrate. We have investigated another alternate approach with displacement of the surrounding bulk water phase by N2 gas, resulting in rapid release of CH4 gas and complete loss of the solid hydrate phase. Our experiment was carried out at the Southern Summit of Hydrate Ridge, offshore Oregon, at 780m depth. There we harvested hydrate fragments from surficial sediments using the robotic arm of the ROV Doc Ricketts. Specimens of the hydrate were collected about 1m above the sediment surface in an inverted funnel with a mesh covered neck as they floated upwards. The accumulated hydrate was transferred to an inverted glass cylinder, and N2 gas was carefully injected into this container. Displacement of the water phase occurred and when the floating hydrate material approached the lower rim the gas injection was stopped and the cylinder placed upon a flat metal plate effectively sealing the system. We returned to this site after 7 days to measure progress, and observed complete loss of the hydrate phase

  2. Tetrahydrofuran hydrate decomposition characteristics in porous media

    Science.gov (United States)

    Song, Yongchen; Wang, Pengfei; Wang, Shenglong; Zhao, Jiafei; Yang, Mingjun

    2016-12-01

    Many tetrahydrofuran (THF) hydrate properties are similar to those of gas hydrates. In the present work THF hydrate dissociation in four types of porous media is studied. THF solution was cooled to 275.15 K with formation of the hydrate under ambient pressure, and then it dissociated under ambient conditions. THF hydrate dissociation experiments in each porous medium were conducted three times. Magnetic resonance imaging (MRI) was used to obtain images. Decomposition time, THF hydrate saturation and MRI mean intensity (MI) were measured and analyzed. The experimental results showed that the hydrate decomposition time in BZ-4 and BZ-3 was similar and longer than that in BZ-02. In each dissociation process, the hydrate decomposition time of the second and third cycles was shorter than that of the first cycle in BZ-4, BZ-3, and BZ-02. The relationship between THF hydrate saturation and time is almost linear.

  3. Molecular dynamics study of contact mechanics: contact area and interfacial separation from small to full contact

    Science.gov (United States)

    Yang, Chunyan; Persson, Bo

    2008-03-01

    We report a molecular dynamics study of the contact between a rigid solid with a randomly rough surface and an elastic block with a flat surface. We study the contact area and the interfacial separation from small contact (low load) to full contact (high load). For small load the contact area varies linearly with the load and the interfacial separation depends logarithmically on the load [1-4]. For high load the contact area approaches to the nominal contact area (i.e., complete contact), and the interfacial separation approaches to zero. The present results may be very important for soft solids, e.g., rubber, or for very smooth surfaces, where complete contact can be reached at moderate high loads without plastic deformation of the solids. References: [1] C. Yang and B.N.J. Persson, arXiv:0710.0276, (to appear in Phys. Rev. Lett.) [2] B.N.J. Persson, Phys. Rev. Lett. 99, 125502 (2007) [3] L. Pei, S. Hyun, J.F. Molinari and M.O. Robbins, J. Mech. Phys. Sol. 53, 2385 (2005) [4] M. Benz, K.J. Rosenberg, E.J. Kramer and J.N. Israelachvili, J. Phy. Chem. B.110, 11884 (2006)

  4. Clinker mineral hydration at reduced relative humidities

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Hansen, Per Freiesleben; Lachowski, Eric E.;

    1999-01-01

    Vapour phase hydration of purl cement clinker minerals at reduced relative humidities is described. This is relevant to modern high performance concrete that may self-desiccate during hydration and is also relevant to the quality of the cement during storage. Both the oretical considerations...... and experimental data are presented showing that C(3)A can hydrate at lower humidities than either C3S or C2S. It is suggested that the initiation of hydration during exposure to water vapour is nucleation controlled. When C(3)A hydrates at low humidity, the characteristic hydration product is C(3)AH(6...

  5. Progress of Gas Hydrate Studies in China

    Institute of Scientific and Technical Information of China (English)

    樊栓狮; 汪集旸

    2006-01-01

    A brief overview is given on the gas hydrate-related research activities carried out by Chinese researchers in the past 15 years. The content involves: (1) Historical review. Introducing the gas hydrate research history in China; (2) Gas hydrate research groups in China. There are nearly 20 groups engaged in gas hydrate research now; (3) Present studies.Including fundamental studies, status of the exploration of natural gas hydrate resources in the South China Sea region, and development of hydrate-based new techniques; (4) Future development.

  6. Hydration of fly ash cement

    Energy Technology Data Exchange (ETDEWEB)

    Etsuo Sakai; Shigeyoshi Miyahara; Shigenari Ohsawa; Seung-Heun Lee; Masaki Daimon [Tokyo Institute of Technology, Tokyo (Japan). Department of Metallurgy and Ceramics Science, Graduate School of Science and Engineering

    2005-06-01

    It is necessary to establish the material design system for the utilization of large amounts of fly ash as blended cement instead of disposing of it as a waste. Cement blended with fly ash is also required as a countermeasure to reduce the amount of CO{sub 2} generation. In this study, the influences of the glass content and the basicity of glass phase on the hydration of fly ash cement were clarified and hydration over a long curing time was characterized. Two kinds of fly ash with different glass content, one with 38.2% and another with 76.6%, were used. The hydration ratio of fly ash was increased by increasing the glass content in fly ash in the specimens cured for 270 days. When the glass content of fly ash is low, the basicity of glass phase tends to decrease. Reactivity of fly ash is controlled by the basicity of the glass phase in fly ash during a period from 28 to 270 days. However, at an age of 360 days, the reaction ratios of fly ash show almost identical values with different glass contents. Fly ash also affected the hydration of cement clinker minerals in fly ash cement. While the hydration of alite was accelerated, that of belite was retarded at a late stage.

  7. Generalization of Soft Neutrosophic Rings and Soft Neutrosophic Fields

    Directory of Open Access Journals (Sweden)

    Mumtaz Ali

    2014-12-01

    Full Text Available In this paper we extend soft neutrosophic rings and soft neutrosophic fields to soft neutrosophic birings, soft neutrosophic N-rings and soft neutrosophic bifields and soft neutrosophic N-fields. We also extend soft neutrosophic ideal theory to form soft neutrosophic biideal and soft neutrosophic N-ideals over a neutrosophic biring and soft neutrosophic N-ring. We have given examples to illustrate the theory of soft neutrosophic birings, soft neutrosophic N-rings and soft neutrosophic fields and soft neutrosophic N-fields and display many properties of these.

  8. Fabricating customized hydrogel contact lens

    Science.gov (United States)

    Childs, Andre; Li, Hao; Lewittes, Daniella M.; Dong, Biqin; Liu, Wenzhong; Shu, Xiao; Sun, Cheng; Zhang, Hao F.

    2016-10-01

    Contact lenses are increasingly used in laboratories for in vivo animal retinal imaging and pre-clinical studies. The lens shapes often need modification to optimally fit corneas of individual test subjects. However, the choices from commercially available contact lenses are rather limited. Here, we report a flexible method to fabricate customized hydrogel contact lenses. We showed that the fabricated hydrogel is highly transparent, with refractive indices ranging from 1.42 to 1.45 in the spectra range from 400 nm to 800 nm. The Young’s modulus (1.47 MPa) and hydrophobicity (with a sessile drop contact angle of 40.5°) have also been characterized experimentally. Retinal imaging using optical coherence tomography in rats wearing our customized contact lenses has the quality comparable to the control case without the contact lens. Our method could significantly reduce the cost and the lead time for fabricating soft contact lenses with customized shapes, and benefit the laboratorial-used contact lenses in pre-clinical studies.

  9. Comparison of stromal hydration techniques for clear corneal cataract incisions: conventional hydration versus anterior stromal pocket hydration.

    Science.gov (United States)

    Mifflin, Mark D; Kinard, Krista; Neuffer, Marcus C

    2012-06-01

    Anterior stromal pocket hydration was compared with conventional hydration for preventing wound leak after 2.8 mm uniplanar clear corneal incisions (CCIs) in patients having routine cataract surgery. Conventional hydration involves hydration of the lateral walls of the main incision with visible whitening of the stroma. The anterior stromal pocket hydration technique involves creation of an additional supraincisional stromal pocket overlying the main incision, which is then hydrated instead of the main incision. Sixty-six eyes of 48 patients were included in the data analysis with 33 assigned to each study group. The anterior stromal pocket hydration technique was significantly better than conventional hydration in preventing wound leak due to direct pressure on the posterior lip of the incision. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  10. Multi-channel electrical impedance tomography for regional tissue hydration monitoring.

    Science.gov (United States)

    Chen, Xiaohui; Kao, Tzu-Jen; Ashe, Jeffrey M; Boverman, Gregory; Sabatini, James E; Davenport, David M

    2014-06-01

    Poor assessment of hydration status during hemodialysis can lead to under- or over-hydration in patients with consequences of increased morbidity and mortality. In current practice, fluid management is largely based on clinical assessments to estimate dry weight (normal hydration body weight). However, hemodialysis patients usually have co-morbidities that can make the signs of fluid status ambiguous. Therefore, achieving normal hydration status remains a major challenge for hemodialysis therapy. Electrical impedance technology has emerged as a promising method for hydration monitoring due to its non-invasive nature, low cost and ease-of-use. Conventional electrical impedance-based hydration monitoring systems employ single-channel current excitation (either 2-electrode or 4-electrode methods) to perturb and extract averaged impedance from bulk tissue and use generalized models from large populations to derive hydration estimates. In the present study, a prototype, single-frequency electrical impedance tomography (EIT) system with simultaneous multi-channel current excitation was used to enable regional hydration change detection. We demonstrated the capability to detect a difference in daily impedance change between left leg and right leg in healthy human subjects, who wore a compression sock only on one leg to reduce daily gravitational fluid accumulation. The impedance difference corresponded well with the difference of lower leg volume change between left leg and right leg measured by volumetry, which on average is ~35 ml, accounting for 0.7% of the lower leg volume. We have demonstrated the feasibility of using multi-channel EIT to extract hydration information in different tissue layers with minimal skin interference. Our simultaneous, multi-channel current excitation approach provides an effective method to separate electrode contact impedance and skin condition artifacts from hydration signals. The prototype system has the potential to be used in clinical

  11. Gas hydrates forming and decomposition conditions analysis

    Directory of Open Access Journals (Sweden)

    А. М. Павленко

    2017-07-01

    Full Text Available The concept of gas hydrates has been defined; their brief description has been given; factors that affect the formation and decomposition of the hydrates have been reported; their distribution, structure and thermodynamic conditions determining the gas hydrates formation disposition in gas pipelines have been considered. Advantages and disadvantages of the known methods for removing gas hydrate plugs in the pipeline have been analyzed, the necessity of their further studies has been proved. In addition to the negative impact on the process of gas extraction, the hydrates properties make it possible to outline the following possible fields of their industrial use: obtaining ultrahigh pressures in confined spaces at the hydrate decomposition; separating hydrocarbon mixtures by successive transfer of individual components through the hydrate given the mode; obtaining cold due to heat absorption at the hydrate decomposition; elimination of the open gas fountain by means of hydrate plugs in the bore hole of the gushing gasser; seawater desalination, based on the hydrate ability to only bind water molecules into the solid state; wastewater purification; gas storage in the hydrate state; dispersion of high temperature fog and clouds by means of hydrates; water-hydrates emulsion injection into the productive strata to raise the oil recovery factor; obtaining cold in the gas processing to cool the gas, etc.

  12. On soft topological space via semiopen and semiclosed soft sets

    CERN Document Server

    Mahanta, J

    2012-01-01

    This paper introduces semiopen and semiclosed soft sets in soft topological spaces. The notions of interior and closure are generalized using these sets. A detail study is carried out on properties of semiopen, semiclosed soft sets, semi interior and semi closure of a soft set in a soft topological space. Various forms of soft functions, like semicontinuous, irresolute, semiopen soft functions are introduced and characterized. Further soft semicompactness,soft semiconnectedness and soft semiseparation axioms are introduced and studied.

  13. Hydration of highly charged ions.

    Science.gov (United States)

    Hofer, Thomas S; Weiss, Alexander K H; Randolf, Bernhard R; Rode, Bernd M

    2011-08-01

    Based on a series of ab initio quantum mechanical charge field molecular dynamics (QMCF MD) simulations, the broad spectrum of structural and dynamical properties of hydrates of trivalent and tetravalent ions is presented, ranging from extreme inertness to immediate hydrolysis. Main group and transition metal ions representative for different parts of the periodic system are treated, as are 2 threefold negatively charged anions. The results show that simple predictions of the properties of the hydrates appear impossible and that an accurate quantum mechanical simulation in cooperation with sophisticated experimental investigations seems the only way to obtain conclusive results.

  14. Great Market Potential of Hydrazine Hydrate

    Institute of Scientific and Technical Information of China (English)

    Shi Yuying

    2007-01-01

    @@ Stable consumption growth worldwide Hydrazine hydrate is an organic chemical raw material with extensive applications. The world's capacity to produce hydrazine hydrate has reached more than 200 thousand t/atoday (based on 100% hydrazine content).

  15. Methods to determine hydration states of minerals and cement hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Baquerizo, Luis G., E-mail: luis.baquerizoibarra@holcim.com [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Matschei, Thomas [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Scrivener, Karen L. [Laboratory of Construction Materials, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Saeidpour, Mahsa; Thorell, Alva; Wadsö, Lars [Building Materials, Lund University, Box 124, 221 000 Lund (Sweden)

    2014-11-15

    This paper describes a novel approach to the quantitative investigation of the impact of varying relative humidity (RH) and temperature on the structure and thermodynamic properties of salts and crystalline cement hydrates in different hydration states (i.e. varying molar water contents). The multi-method approach developed here is capable of deriving physico-chemical boundary conditions and the thermodynamic properties of hydrated phases, many of which are currently missing from or insufficiently reported in the literature. As an example the approach was applied to monosulfoaluminate, a phase typically found in hydrated cement pastes. New data on the dehydration and rehydration of monosulfoaluminate are presented. Some of the methods used were validated with the system Na{sub 2}SO{sub 4}–H{sub 2}O and new data related to the absorption of water by anhydrous sodium sulfate are presented. The methodology and data reported here should permit better modeling of the volume stability of cementitious systems exposed to various different climatic conditions.

  16. Novel understanding of calcium silicate hydrate from dilute hydration

    KAUST Repository

    Zhang, Lina

    2017-05-13

    The perspective of calcium silicate hydrate (C-S-H) is still confronting various debates due to its intrinsic complicated structure and properties after decades of studies. In this study, hydration at dilute suspension of w/s equaling to 10 was conducted for tricalcium silicate (C3S) to interpret long-term hydration process and investigate the formation, structure and properties of C-S-H. Based on results from XRD, IR, SEM, NMR and so forth, loose and dense clusters of C-S-H with analogous C/S ratio were obtained along with the corresponding chemical formulae proposed as Ca5Si4O13∙6.2H2O. Crystalline structure inside C-S-H was observed by TEM, which was allocated at the foil-like proportion as well as the edge of wrinkles of the product. The long-term hydration process of C3S in dilute suspension could be sketchily described as migration of calcium hydroxide and in-situ growth of C-S-H with equilibrium silicon in aqueous solution relatively constant and calcium varied.

  17. Help from a Hindrance: Using Astigmatism in Round Capillaries To Study Contact Angles and Wetting Layers.

    Science.gov (United States)

    Hobeika, Nelly; Bouriat, Patrick; Touil, Abdelhafid; Broseta, Daniel; Brown, Ross; Dubessy, Jean

    2017-05-30

    Round glass capillaries are a basic tool in soft-matter science, but often are shunned due to the astigmatism they introduce in micrographs. Here, we show how refraction in a capillary can be a help instead of a hindrance to obtain precise and sensitive information on two important interfacial properties: the contact angle of two immiscible fluids and the presence of thin films on the capillary wall. Understanding optical cusps due to refraction allows direct mesurement of the inner diameter of a capillary at the meniscus, which, with the height of the meniscus cap, determines the contact angle. The meniscus can thus be measured without intrusive additives to enhance visibility, such as dyes or calibrated particles, in uniform, curved, or even tapered capillaries or under demanding conditions not accessible by conventional methods, such as small volumes (μL), high temperatures, or high pressures. We further elicit the conditions for strong internal reflection on the inner capillary wall, involving the wall and fluid refractive indices and the wall thickness, and show how to choose the capillary section to detect thin (submicron) layers on the wall, by the contribution of total internal reflection to the cusps. As examples, we report the following: (i) CO2-water or -brine contact angles at glass interfaces, measured at temperatures and pressures up to 200 °C and 600 bar, revealing an effect apparently so far unreported-the decrease in the water-wet character of glass, due to dissolved salts in brine, is strongly reduced at high temperatures, where contact angles converge toward the values in pure water; (ii) A tenuous gas hydrate layer growing from the water-guest contact line on glass, invisible in transmission microscopy but prominent in the cusps due to total internal reflection.

  18. Molecular Dynamics Modeling of Hydrated Calcium-Silicate-Hydrate (CSH) Cement Molecular Structure

    Science.gov (United States)

    2014-08-30

    properties of key hydrated cement constituent calcium-silicate-hydrate (CSH) at the molecular, nanometer scale level. Due to complexity, still unknown...public release; distribution is unlimited. Molecular Dynamics Modeling of Hydrated Calcium-Silicate- Hydrate (CSH) Cement Molecular Structure The views... Cement Molecular Structure Report Title Multi-scale modeling of complex material systems requires starting from fundamental building blocks to

  19. Relation between the Rheology Characteristic and Initial Hydration Structure of Portland Cement

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Based on the rheology characteristic and the resistivity variation under alternating electric-field of Portland cement hydration by means of AR2000 advanced rheometer and non-contacting electrical resistivity device, the influence of cement kinds and the chemical admixtures on the initial rheology characteristic and structure forming and developing of cement hydration was studied. The relationship between the rheology characteristic, the initial hydration structure forming and the hydration process at very early ages was analyzed by macro properties and microstructure tests. The results showed that, the storage modulus, acted as S, could be described more subtle distinction accompanying with hydration of fresh paste model at very early period. Combining the resistivity alterations, a sudden change on structure forming emerged when the hydration of cement becoming inducing age. The rheology characteristic was interrelated to the hydration structure forming, development and the physical mechanics properties. The sudden change on storage modulus moved up due to the addition of retarder, but the structure forming and developing was retarded to a certain extent.

  20. Sensitivity Analysis of Gas Production from Class 2 and Class 3 Hydrate Deposits

    Energy Technology Data Exchange (ETDEWEB)

    Reagan, Matthew; Moridis, George; Zhang, Keni

    2008-05-01

    Gas hydrates are solid crystalline compounds in which gas molecules are lodged within the lattices of an ice-like crystalline solid. The vast quantities of hydrocarbon gases trapped in hydrate formations in the permafrost and in deep ocean sediments may constitute a new and promising energy source. Class 2 hydrate deposits are characterized by a Hydrate-Bearing Layer (HBL) that is underlain by a saturated zone of mobile water. Class 3 hydrate deposits are characterized by an isolated Hydrate-Bearing Layer (HBL) that is not in contact with any hydrate-free zone of mobile fluids. Both classes of deposits have been shown to be good candidates for exploitation in earlier studies of gas production via vertical well designs - in this study we extend the analysis to include systems with varying porosity, anisotropy, well spacing, and the presence of permeable boundaries. For Class 2 deposits, the results show that production rate and efficiency depend strongly on formation porosity, have a mild dependence on formation anisotropy, and that tighter well spacing produces gas at higher rates over shorter time periods. For Class 3 deposits, production rates and efficiency also depend significantly on formation porosity, are impacted negatively by anisotropy, and production rates may be larger, over longer times, for well configurations that use a greater well spacing. Finally, we performed preliminary calculations to assess a worst-case scenario for permeable system boundaries, and found that the efficiency of depressurization-based production strategies are compromised by migration of fluids from outside the system.

  1. Hydration and Thermal Expansion in Anatase Nanoparticles.

    Science.gov (United States)

    Zhu, He; Li, Qiang; Ren, Yang; Fan, Longlong; Chen, Jun; Deng, Jinxia; Xing, Xianran

    2016-08-01

    A tunable thermal expansion is reported in nanosized anatase by taking advantage of surface hydration. The coefficient of thermal expansion of 4 nm TiO2 along a-axis is negative with a hydrated surface and is positive without a hydrated surface. High-energy synchrotron X-ray pair distribution function analysis combined with ab initio calculations on the specific hydrated surface are carried out to reveal the local structure distortion that is responsible for the unusual negative thermal expansion.

  2. Hydration and Thermal Expansion in Anatase Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, He [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083 China; Li, Qiang [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083 China; Ren, Yang [Argonne National Laboratory, X-Ray Science Division, Argonne IL 60439 USA; Fan, Longlong [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083 China; Chen, Jun [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083 China; Deng, Jinxia [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083 China; Xing, Xianran [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083 China

    2016-06-06

    A tunable thermal expansion is reported in nanosized anatase by taking advantage of surface hydration. The coefficient of thermal expansion of 4 nm TiO2 along a-axis is negative with a hydrated surface and is positive without a hydrated surface. High-energy synchrotron X-ray pair distribution function analysis combined with ab initio calculations on the specific hydrated surface are carried out to reveal the local structure distortion that is responsible for the unusual negative thermal expansion.

  3. Numerical simulations of sand production in interbedded hydrate-bearing sediments during depressurization

    Science.gov (United States)

    Uchida, Shun; Lin, Jeen-Shang; Myshakin, Evgeniy; Seol, Yongkoo; Collett, Timothy S.; Boswell, Ray

    2017-01-01

    Geomechanical behavior of hydrate-bearing sediments during gas production is complex, involving changes in hydrate-dependent mechanical properties. When interbedded clay layers are present, the complexity is more pronounced because hydrate dissociation tends to occur preferentially in the sediments adjacent to the clay layers due to clay layers acting as a heat source. This would potentially lead to shearing deformation along the sand/clay contacts and may contribute to solid migration, which hindered past field-scale gas production tests. This paper presents a near-wellbore simulation of sand/clay interbedded hydrate-bearing sediments that have been subjected to depressurization and discusses the effect of clay layers on sand production.

  4. Fuzzy Soft Topological Groups

    Directory of Open Access Journals (Sweden)

    S. Nazmul

    2014-03-01

    Full Text Available Notions of Lowen type fuzzy soft topological space are introduced and some of their properties are established in the present paper. Besides this, a combined structure of a fuzzy soft topological space and a fuzzy soft group, which is termed here as fuzzy soft topological group is introduced. Homomorphic images and preimages are also examined. Finally, some definitions and results on fuzzy soft set are studied.

  5. Hexosome and hexagonal phases mediated by hydration and polymeric stabilizer.

    Science.gov (United States)

    Amar-Yuli, Idit; Wachtel, Ellen; Shoshan, Einav Ben; Danino, Dganit; Aserin, Abraham; Garti, Nissim

    2007-03-27

    In this research, we studied the factors that control formation of GMO/tricaprylin/water hexosomes and affect their inner structure. As a stabilizer of the soft particles dispersed in the aqueous phase, we used the hydrophilic nonionic triblock polymer Pluronic 127. We demonstrate how properties of the hexosomes, such as size, structure, and stability, can be tuned by their internal composition, polymer concentration, and processing conditions. The morphology and inner structure of the hexosomes were characterized by small-angle X-ray scattering, cryo-transmission electron microscope, and dynamic light scattering. The physical stability (to creaming, aggregation, and coalescence) of the hexosomes was further examined by the LUMiFuge technique. Two competing processes are presumed to take place during the formation of hexosomes: penetration of water from the continuous phase during dispersion, resulting in enhanced hydration of the head groups, and incorporation of the polymer chains into the hexosome structure while providing a stabilizing surface coating for the dispersed particles. Hydration is an essential stage in lyotropic liquid crystal (LLC) formation. The polymer, on the other hand, dehydrates the lipid heads, thereby introducing disorder into the LLC and reducing the domain size. Yet, a critical minimum polymer concentration is necessary in order to form stable nanosized hexosomes. These competing effects require the attention of those preparing hexosomes. The competition between these two processes can be controlled. At relatively high polymer concentrations (1-1.6 wt % of the total formulation of the soft particles), the hydration process seems to occur more rapidly than polymer adsorption. As a result, smaller and more stable soft particles with high symmetry were formed. On the other hand, when the polymer concentration is fixed at lower levels (<1.0 wt %), the homogenization process encourages only partial polymer adsorption during the dispersion

  6. Terahertz sensing of corneal hydration.

    Science.gov (United States)

    Singh, Rahul S; Tewari, Priyamvada; Bourges, Jean Louis; Hubschman, Jean Pierre; Bennett, David B; Taylor, Zachary D; Lee, H; Brown, Elliott R; Grundfest, Warren S; Culjat, Martin O

    2010-01-01

    An indicator of ocular health is the hydrodyanmics of the cornea. Many corneal disorders deteriorate sight as they upset the normal hydrodynamics of the cornea. The mechanisms include the loss of endothelial pump function of corneal dystophies, swelling and immune response of corneal graft rejection, and inflammation and edema, which accompany trauma, burn, and irritation events. Due to high sensitivity to changes of water content in materials, a reflective terahertz (300 GHz and 3 THz) imaging system could be an ideal tool to measure the hydration level of the cornea. This paper presents the application of THz technology to visualize the hydration content across ex vivo porcine corneas. The corneas, with a thickness variation from 470 - 940 µm, were successfully imaged using a reflective pulsed THz imaging system, with a maximum SNR of 50 dB. To our knowledge, no prior studies have reported on the use of THz in measuring hydration in corneal tissues or other ocular tissues. These preliminary findings indicate that THz can be used to accurately sense hydration levels in the cornea using a pulsed, reflective THz imaging system.

  7. Physical properties of gas hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Kliner, J.T.R.; Grozic, J.L.H. [Calgary Univ., AB (Canada)

    2003-07-01

    Gas hydrates are naturally occurring, solid crystalline compounds (clathrates) that encapsulate gas molecules inside the lattices of hydrogen bonded water molecules within a specific temperature-pressure stability zone. Estimates of the total quantity of available methane gas in natural occurring hydrates are based on twice the energy content of known conventional fossil fuels reservoirs. Accurate and reliable in-situ quantification techniques are essential in determining the economic viability of this potential energy yield, which is dependent upon several factors such as sensitivity of the temperature-pressure stability zone, sediment type, porosity, permeability, concentration/abundance of free gas, spatial distribution in pore spaces, specific cage occupancy, and the influence of inhibitors. Various techniques like acoustic P and S waves, time domain reflectometry, and electrical resistance have been used to analyze the quantity and spatial distribution of the gas hydrate samples. These techniques were reviewed and the results obtained in the course of gas hydrate research were presented. 34 refs., 8 figs.

  8. Hydration kinetics of transgenic soybeans

    Directory of Open Access Journals (Sweden)

    Aline Francielle Fracasso

    2015-01-01

    Full Text Available The kinetic and experimental analyses of the hydration process of transgenic soybeans (BRS 225 RR are provided. The importance of the hydration process consists of the grain texture modifications which favor grinding and extraction of soybeans. The soaking isotherms were obtained for four different temperatures. Results showed that temperature affected transgenic soybeans´ hydration rate and time. Moisture content d.b. of the soybeans increased from 0.12 ± 0.01 kg kg-1 to 1.45 ± 0.19 kg kg-1 during 270 min. of process. Two models were used to fit the kinetic curves: an empirical model developed by Peleg (1988 and a phenomenological one, proposed by Omoto et al. (2009. The two models adequately represented the hydration kinetics. Peleg model was applied to the experimental data and the corresponding parameters were obtained and correlated to temperature. The model by Omoto et al. (2009 showed a better statistical fitting. Although Ks was affected by temperature (Ks = 0.38079 exp (-2289.3 T-1, the equilibrium concentration remained practically unchanged.

  9. Improved Design and Fabrication of Hydrated-Salt Pills

    Science.gov (United States)

    Shirron, Peter J.; DiPirro, Michael J.; Canavan, Edgar R.

    2011-01-01

    A high-performance design, and fabrication and growth processes to implement the design, have been devised for encapsulating a hydrated salt in a container that both protects the salt and provides thermal conductance between the salt and the environment surrounding the container. The unitary salt/container structure is known in the art as a salt pill. In the original application of the present design and processes, the salt is, more specifically, a hydrated paramagnetic salt, for use as a refrigerant in a very-low-temperature adiabatic demagnetization refrigerator (ADR). The design and process can also be applied, with modifications, to other hydrated salts. Hydrated paramagnetic salts have long been used in ADRs because they have the desired magnetic properties at low temperatures. They also have some properties, disadvantageous for ADRs, that dictate the kind of enclosures in which they must be housed: Being hydrated, they lose water if exposed to less than 100-percent relative humidity. Because any dehydration compromises their magnetic properties, salts used in ADRs must be sealed in hermetic containers. Because they have relatively poor thermal conductivities in the temperature range of interest (<0.1 K), integral thermal buses are needed as means of efficiently transferring heat to and from the salts during refrigeration cycles. A thermal bus is typically made from a high-thermal-conductivity met al (such as copper or gold), and the salt is configured to make intimate thermal contact with the metal. Commonly in current practice (and in the present design), the thermal bus includes a matrix of wires or rods, and the salt is grown onto this matrix. The density and spacing of the conductors depend on the heat fluxes that must be accommodated during operation.

  10. Lubrication of soft viscoelastic solids

    CERN Document Server

    Pandey, Anupam; Venner, Kees; Snoeijer, Jacco

    2015-01-01

    Lubrication flows appear in many applications in engineering, biophysics, and in nature. Separation of surfaces and minimisation of friction and wear is achieved when the lubrication fluid builds up a lift force. In this paper we analyse soft lubricated contacts by treating the solid walls as viscoelastic: soft materials are typically not purely elastic, but dissipate energy under dynamical loading conditions. We present a method for viscoelastic lubrication and focus on three canonical examples, namely Kelvin-Voigt-, Standard Linear-, and Power Law-rheology. It is shown how the solid viscoelasticity affects the lubrication process when the timescale of loading becomes comparable to the rheological timescale. We derive asymptotic relations between lift force and sliding velocity, which give scaling laws that inherit a signature of the rheology. In all cases the lift is found to decrease with respect to purely elastic systems.

  11. Physical activity, hydration and health

    Directory of Open Access Journals (Sweden)

    Ascensión Marcos

    2014-06-01

    Full Text Available Since the beginning of mankind, man has sought ways to promote and preserve health as well as to prevent disease. Hydration, physical activity and exercise are key factors for enhancing human health. However, either a little dose of them or an excess can be harmful for health maintenance at any age. Water is an essential nutrient for human body and a major key to survival has been to prevent dehydration. However, there is still a general controversy regarding the necessary amount to drink water or other beverages to properly get an adequate level of hydration. In addition, up to now the tools used to measure hydration are controversial. To this end, there are several important groups of variables to take into account such as water balance, hydration biomarkers and total body water. A combination of methods will be the most preferred tool to find out any risk or situation of dehydration at any age range. On the other hand, physical activity and exercise are being demonstrated to promote health, avoiding or reducing health problems, vascular and inflammatory diseases and helping weight management. Therefore, physical activity is also being used as a pill within a therapy to promote health and reduce risk diseases, but as in the case of drugs, dose, intensity, frequency, duration and precautions have to be evaluated and taken into account in order to get the maximum effectiveness and success of a treatment. On the other hand, sedentariness is the opposite concept to physical activity that has been recently recognized as an important factor of lifestyle involved in the obesogenic environment and consequently in the risk of the non-communicable diseases. In view of the literature consulted and taking into account the expertise of the authors, in this review a Decalogue of global recommendations is included to achieve an adequate hydration and physical activity status to avoid overweight/obesity consequences.

  12. Investigation into the Formation and Adhesion of Cyclopentane Hydrates on Mechanically Robust Vapor-Deposited Polymeric Coatings.

    Science.gov (United States)

    Sojoudi, Hossein; Walsh, Matthew R; Gleason, Karen K; McKinley, Gareth H

    2015-06-09

    Blockage of pipelines by formation and accumulation of clathrate hydrates of natural gases (also called gas hydrates) can compromise project safety and economics in oil and gas operations, particularly at high pressures and low temperatures such as those found in subsea or arctic environments. Cyclopentane (CyC5) hydrate has attracted interest as a model system for studying natural gas hydrates, because CyC5, like typical natural gas hydrate formers, is almost fully immiscible in water; and thus CyC5 hydrate formation is governed not only by thermodynamic phase considerations but also kinetic factors such as the hydrocarbon/water interfacial area, as well as mass and heat transfer constraints, as for natural gas hydrates. We present a macroscale investigation of the formation and adhesion strength of CyC5 hydrate deposits on bilayer polymer coatings with a range of wettabilities. The polymeric bilayer coatings are developed using initiated chemical vapor deposition (iCVD) of a mechanically robust and densely cross-linked polymeric base layer (polydivinylbenzene or pDVB) that is capped with a covalently attached thin hydrate-phobic fluorine-rich top layer (poly(perfluorodecyl acrylate) or pPFDA). The CyC5 hydrates are formed from CyC5-in-water emulsions, and differential scanning calorimetry (DSC) is used to confirm the thermal dissociation properties of the solid hydrate deposits. We also investigate the adhesion of the CyC5 hydrate deposits on bare and bilayer polymer-coated silicon and steel substrates. Goniometric measurements with drops of CyC5-in-water emulsions on the coated steel substrates exhibit advancing contact angles of 148.3 ± 4.5° and receding contact angles of 142.5 ± 9.8°, indicating the strongly emulsion-repelling nature of the iCVD coatings. The adhesion strength of the CyC5 hydrate deposits is reduced from 220 ± 45 kPa on rough steel substrates to 20 ± 17 kPa on the polymer-coated steel substrates. The measured strength of CyC5 hydrate

  13. Molecular mechanisms of decomposition of hydrated Na+Cl- ion pairs under planar nanopore conditions

    Science.gov (United States)

    Shevkunov, S. V.

    2017-02-01

    The decomposition of Na+Cl- ion pairs under the conditions of a nanoscopic planar pore with structureless walls in a material contact with water vapor at 298 K is simulated by Monte Carlo method. The transition from the state of a contact ion pair (CIP) to the state of solvent-separated ion pair (SSIP) is shown to occur as a result of an increase in the vapor pressure over a pore after exceeding the threshold number of molecules in a hydrate shell. It is found that the planar form of a molecular cluster under the conditions of a narrow pore does not level an abrupt structural transition and the formation of hydrogen bonds in the hydrate shell starts after three molecules are added. The hydrogen bond length under pore conditions is found to be resistant to variations in the hydrate shell size and coincides with that in water under normal conditions.

  14. Seismic reflections associated with submarine gas hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Andreassen, K.

    1995-12-31

    Gas hydrates are often suggested as a future energy resource. This doctoral thesis improves the understanding of the concentration and distribution of natural submarine gas hydrates. The presence of these hydrates are commonly inferred from strong bottom simulating reflection (BSR). To investigate the nature of BSR, this work uses seismic studies of hydrate-related BSRs at two different locations, one where gas hydrates are accepted to exist and interpreted to be very extensive (in the Beaufort Sea), the other with good velocity data and downhole logs available (offshore Oregon). To ascertain the presence of free gas under the BSR, prestack offset data must supplement near-vertical incidence seismic data. A tentative model for physical properties of sediments partially saturated with gas hydrate and free gas is presented. This model, together with drilling information and seismic data containing the BSR beneath the Oregon margin and the Beaufort Sea, made it possible to better understand when to apply the amplitude-versus-offset (AVO) method to constrain BSR gas hydrate and gas models. Distribution of natural gas hydrates offshore Norway and Svalbard is discussed and interpreted as reflections from the base of gas hydrate-bearing sediments, overlying sediments containing free gas. Gas hydrates inferred to exist at the Norwegian-Svalbard continental margin correlate well with Cenozoic depocenters, and the associated gas is assumed to be mainly biogenic. Parts of that margin have a high potential for natural gas hydrates of both biogenic and thermogenic origin. 235 refs., 86 figs., 4 tabs.

  15. Contribution of hydration to protein folding thermodynamics. I. The enthalpy of hydration.

    Science.gov (United States)

    Makhatadze, G I; Privalov, P L

    1993-07-20

    The enthalpy of hydration of polar and non-polar groups upon protein unfolding has been estimated for four globular proteins in the temperature range 5 to 125 degrees C, using structural information on the groups in these proteins exposed to water in the native and unfolded states and volume-corrected calorimetric information on the enthalpy and heat capacity of transfer into water of various model compounds. It has been shown that the enthalpy of hydration of polar groups greatly exceeds the enthalpy of hydration of non-polar groups. At low temperatures both these enthalpies are negative and change in opposite direction with increasing temperature. Subtracting the total enthalpy of hydration of polar and non-polar groups from the calorimetrically determined enthalpy of protein unfolding, the total enthalpy of internal interactions maintaining the native protein structure has been determined. Using thermodynamic information on the sublimation of organic crystals, the total enthalpy was divided into two components: one associated with the interactions between the non-polar groups (van der Waals interaction) and the rest associated with the interactions between polar groups (hydrogen bonding). This made it possible to estimate the overall enthalpies of disruption of contacts between the polar groups with their exposure to water and between the non-polar groups with their exposure to water. It appears that these enthalpies have opposite signs in the temperature range considered and change in opposite directions with increasing temperature. The enthalpy of transfer of non-polar groups from the protein interior into water is negative below 25 degrees C and positive above. The enthalpy of transfer of polar groups from the protein interior into water is positive at low temperatures and becomes negative at higher temperatures. Over the considered temperature range, however, the enthalpy of transfer of non-polar groups dominates. This results in a positive enthalpy of

  16. Handbook of gas hydrate properties and occurrence

    Energy Technology Data Exchange (ETDEWEB)

    Kuustraa, V.A.; Hammershaimb, E.C.

    1983-12-01

    This handbook provides data on the resource potential of naturally occurring hydrates, the properties that are needed to evaluate their recovery, and their production potential. The first two chapters give data on the naturally occurring hydrate potential by reviewing published resource estimates and the known and inferred occurrences. The third and fourth chapters review the physical and thermodynamic properties of hydrates, respectively. The thermodynamic properties of hydrates that are discussed include dissociation energies and a simplified method to calculate them; phase diagrams for simple and multi-component gases; the thermal conductivity; and the kinetics of hydrate dissociation. The final chapter evaluates the net energy balance of recovering hydrates and shows that a substantial positive energy balance can theoretically be achieved. The Appendices of the Handbook summarize physical and thermodynamic properties of gases, liquids and solids that can be used in designing and evaluating recovery processes of hydrates. 158 references, 67 figures, 47 tables.

  17. Separation of water through gas hydrate formation

    DEFF Research Database (Denmark)

    Boch Andersen, Torben; Thomsen, Kaj

    2009-01-01

    Gas hydrate is normally recognized as a troublemaker in the oil and gas industry. However, gas hydrate has some interesting possibilities when used in connection with separation of water. Nordic Sugar has investigated the possibility of using gas hydrates for concentration of sugar juice. The goa...... volumes and the needs for high pressure. The process could be interesting for concentration of heat sensitive, high value products......Gas hydrate is normally recognized as a troublemaker in the oil and gas industry. However, gas hydrate has some interesting possibilities when used in connection with separation of water. Nordic Sugar has investigated the possibility of using gas hydrates for concentration of sugar juice. The goal...... of the project was to formulate an alternative separation concept, which can replace the traditional water evaporation process in the sugar production. Work with the separation concept showed that gas hydrates can be used for water separation. The process is not suitable for sugar production because of large...

  18. A Wirelessly Powered Smart Contact Lens with Reconfigurable Wide Range and Tunable Sensitivity Sensor Readout Circuitry.

    Science.gov (United States)

    Chiou, Jin-Chern; Hsu, Shun-Hsi; Huang, Yu-Chieh; Yeh, Guan-Ting; Liou, Wei-Ting; Kuei, Cheng-Kai

    2017-01-07

    This study presented a wireless smart contact lens system that was composed of a reconfigurable capacitive sensor interface circuitry and wirelessly powered radio-frequency identification (RFID) addressable system for sensor control and data communication. In order to improve compliance and reduce user discomfort, a capacitive sensor was embedded on a soft contact lens of 200 μm thickness using commercially available bio-compatible lens material and a standard manufacturing process. The results indicated that the reconfigurable sensor interface achieved sensitivity and baseline tuning up to 120 pF while consuming only 110 μW power. The range and sensitivity tuning of the readout circuitry ensured a reliable operation with respect to sensor fabrication variations and independent calibration of the sensor baseline for individuals. The on-chip voltage scaling allowed the further extension of the detection range and prevented the implementation of large on-chip elements. The on-lens system enabled the detection of capacitive variation caused by pressure changes in the range of 2.25 to 30 mmHg and hydration level variation from a distance of 1 cm using incident power from an RFID reader at 26.5 dBm.

  19. Hole-doping of mechanically exfoliated graphene by confined hydration layers

    NARCIS (Netherlands)

    Bollmann, Tjeerd Rogier Johannes; Antipina, L.Y.; Temmen, M.; Reichling, M.; Sorokin, P.B.

    2015-01-01

    By the use of non-contact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM), we measure the local surface potential of mechanically exfoliated graphene on the prototypical insulating hydrophilic substrate of CaF2(111). Hydration layers confined between the graphene and the Ca

  20. Hole-doping of mechanically exfoliated graphene by confined hydration layers

    NARCIS (Netherlands)

    Bollmann, T.R.J.; Antipina, L.Y.; Temmen, M.; Reichling, M.; Sorokin, P.B.

    2015-01-01

    By the use of non-contact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM), we measure the local surface potential of mechanically exfoliated graphene on the prototypical insulating hydrophilic substrate of CaF2(111). Hydration layers confined between the graphene and the Ca

  1. From hydration repulsion to dry adhesion between asymmetric hydrophilic and hydrophobic surfaces.

    Science.gov (United States)

    Kanduč, Matej; Netz, Roland R

    2015-10-01

    Using all-atom molecular dynamics (MD) simulations at constant water chemical potential in combination with basic theoretical arguments, we study hydration-induced interactions between two overall charge-neutral yet polar planar surfaces with different wetting properties. Whether the water film between the two surfaces becomes unstable below a threshold separation and cavitation gives rise to long-range attraction, depends on the sum of the two individual surface contact angles. Consequently, cavitation-induced attraction also occurs for a mildly hydrophilic surface interacting with a very hydrophobic surface. If both surfaces are very hydrophilic, hydration repulsion dominates at small separations and direct attractive force contribution can-if strong enough-give rise to wet adhesion in this case. In between the regimes of cavitation-induced attraction and hydration repulsion we find a narrow range of contact angle combinations where the surfaces adhere at contact in the absence of cavitation. This dry adhesion regime is driven by direct surface-surface interactions. We derive simple laws for the cavitation transition as well as for the transition between hydration repulsion and dry adhesion, which favorably compare with simulation results in a generic adhesion state diagram as a function of the two surface contact angles.

  2. Hole-doping of mechanically exfoliated graphene by confined hydration layers

    NARCIS (Netherlands)

    Bollmann, Tjeerd Rogier Johannes; Antipina, L.Y.; Temmen, M.; Reichling, M.; Sorokin, P.B.

    2015-01-01

    By the use of non-contact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM), we measure the local surface potential of mechanically exfoliated graphene on the prototypical insulating hydrophilic substrate of CaF2(111). Hydration layers confined between the graphene and the

  3. Well log characterization of natural gas hydrates

    Science.gov (United States)

    Collett, Timothy S.; Lee, Myung W.

    2011-01-01

    In the last 25 years we have seen significant advancements in the use of downhole well logging tools to acquire detailed information on the occurrence of gas hydrate in nature: From an early start of using wireline electrical resistivity and acoustic logs to identify gas hydrate occurrences in wells drilled in Arctic permafrost environments to today where wireline and advanced logging-while-drilling tools are routinely used to examine the petrophysical nature of gas hydrate reservoirs and the distribution and concentration of gas hydrates within various complex reservoir systems. The most established and well known use of downhole log data in gas hydrate research is the use of electrical resistivity and acoustic velocity data (both compressional- and shear-wave data) to make estimates of gas hydrate content (i.e., reservoir saturations) in various sediment types and geologic settings. New downhole logging tools designed to make directionally oriented acoustic and propagation resistivity log measurements have provided the data needed to analyze the acoustic and electrical anisotropic properties of both highly inter-bedded and fracture dominated gas hydrate reservoirs. Advancements in nuclear-magnetic-resonance (NMR) logging and wireline formation testing have also allowed for the characterization of gas hydrate at the pore scale. Integrated NMR and formation testing studies from northern Canada and Alaska have yielded valuable insight into how gas hydrates are physically distributed in sediments and the occurrence and nature of pore fluids (i.e., free-water along with clay and capillary bound water) in gas-hydrate-bearing reservoirs. Information on the distribution of gas hydrate at the pore scale has provided invaluable insight on the mechanisms controlling the formation and occurrence of gas hydrate in nature along with data on gas hydrate reservoir properties (i.e., permeabilities) needed to accurately predict gas production rates for various gas hydrate

  4. Thermal conductivity of hydrate-bearing sediments

    Science.gov (United States)

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

    2009-11-01

    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.

  5. Thermal conductivity of hydrate-bearing sediments

    Science.gov (United States)

    Cortes, D.D.; Martin, A.I.; Yun, T.S.; Francisca, F.M.; Santamarina, J.C.; Ruppel, C.

    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. Copyright 2009 by the American Geophysical Union.

  6. The effect of hydrate saturation on water retention curves in hydrate-bearing sediments

    Science.gov (United States)

    Mahabadi, Nariman; Zheng, Xianglei; Jang, Jaewon

    2016-05-01

    The experimental measurement of water retention curve in hydrate-bearing sediments is critically important to understand the behavior of hydrate dissociation and gas production. In this study, tetrahydrofuran (THF) is selected as hydrate former. The pore habit of THF hydrates is investigated by visual observation in a transparent micromodel. It is confirmed that THF hydrates are not wetting phase on the quartz surface of the micromodel and occupy either an entire pore or part of pore space resulting in change in pore size distribution. And the measurement of water retention curves in THF hydrate-bearing sediments with hydrate saturation ranging from Sh = 0 to Sh = 0.7 is conducted for excess water condition. The experimental results show that the gas entry pressure and the capillary pressure increase with increasing hydrate saturation. Based on the experimental results, fitting parameters for van Genuchten equation are suggested for different hydrate saturation conditions.

  7. Prioritized Contact Transport Stream

    Science.gov (United States)

    Hunt, Walter Lee, Jr. (Inventor)

    2015-01-01

    A detection process, contact recognition process, classification process, and identification process are applied to raw sensor data to produce an identified contact record set containing one or more identified contact records. A prioritization process is applied to the identified contact record set to assign a contact priority to each contact record in the identified contact record set. Data are removed from the contact records in the identified contact record set based on the contact priorities assigned to those contact records. A first contact stream is produced from the resulting contact records. The first contact stream is streamed in a contact transport stream. The contact transport stream may include and stream additional contact streams. The contact transport stream may be varied dynamically over time based on parameters such as available bandwidth, contact priority, presence/absence of contacts, system state, and configuration parameters.

  8. Analysing soft matter

    Directory of Open Access Journals (Sweden)

    Tom McLeish

    2005-09-01

    Full Text Available A new volume on soft materials ranges broadly across systems and techniques, experiment, and theory. Despite a lack of coherence, there is much of interest, which conveys the energy within soft-matter science, says

  9. Oxygen and Contact Lens Wear%氧气与角膜接触镜配戴

    Institute of Scientific and Technical Information of China (English)

    王建华; Desmond Fonn; Renee Du Toit

    1999-01-01

    In this article we review the role of oxygen and contact lens wear related to the metabolic processes of the cornea.The critical oxygen requirement of the cornea for maintenance of its normal hydration level to ensure transparency is discussed,as well as the subsequent reversible and irreversible changes to the corneal layers if this requirement is not met.We review the concept of oxygen transmission and its application to rigid gas permeable and soft contact lens material.Corneal responses to induced hypoxia related to extended wear of contact lenses as well as other complications,such as infection,are discussed.In conclusion,we comment on the oxygen performance of a new generation of silicone hydrogel contact lens materials and the future of extended wear.%全球大约有八千万人(约占总人口的1.5%)在配戴角膜接触镜,镜片的透氧性及配戴角膜接触镜后角膜的获氧状态是保证配戴安全性和有效性的关键.角膜需要多种营养物质以保证其正常的代谢功能,氧气是其中是重要的部分,只有在充分氧供的状态下,角膜才能保持稳定的78%的水合状态,保证角膜透明性.为了进一步了解氧气与角膜接触镜配戴的关系,本文着重对角膜接触镜所致的角膜缺氧的主要表现及角膜接触镜的透氧性能及其表达指标作一综述.

  10. Synthesis of hydrated lutetium carbonate

    Energy Technology Data Exchange (ETDEWEB)

    Song Liu [South China Univ. of Technology, Dept. of Applied Chemistry, Guangdong (China); Rong-jun Ma [Changsha Research Institute of Minig and Metallurgy, Hunan (China)

    1997-09-01

    Crystalline lutetium carbonate was synthesized for the corresponding chloride using ammonium bicarbonate as precipitant. The chemical analyses suggest that the synthesized lutetium carbonate is a hydrated basic carbonate or oxycarbonate. The X-ray powder diffraction data are presented. The IR data for the compound show the presence of two different carbonate groups. There is no stable intermediate carbonate in the process of thermal decomposition of the lutetium carbonate. (au) 15 refs.

  11. Crystallite size distributions of marine gas hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Klapp, S.A.; Bohrmann, G.; Abegg, F. [Bremen Univ., Bremen (Germany). Research Center of Ocean Margins; Hemes, S.; Klein, H.; Kuhs, W.F. [Gottingen Univ., Gottingen (Germany). Dept. of Crystallography

    2008-07-01

    Experimental studies were conducted to determine the crystallite size distributions of natural gas hydrate samples retrieved from the Gulf of Mexico, the Black Sea, and a hydrate ridge located near offshore Oregon. Synchrotron radiation technology was used to provide the high photon fluxes and high penetration depths needed to accurately analyze the bulk sediment samples. A new beam collimation diffraction technique was used to measure gas hydrate crystallite sizes. The analyses showed that gas hydrate crystals were globular in shape. Mean crystallite sizes ranged from 200 to 400 {mu}m for hydrate samples taken from the sea floor. Larger grain sizes in the hydrate ridge samples suggested differences in hydrate formation ages or processes. A comparison with laboratory-produced methane hydrate samples showed half a lognormal curve with a mean value of 40{mu}m. Results of the study showed that a cautious approach must be adopted when transposing crystallite-size sensitive physical data from laboratory-made gas hydrates to natural settings. It was concluded that crystallite size information may also be used to resolve the formation ages of gas hydrates when formation processes and conditions are constrained. 48 refs., 1 tab., 9 figs.

  12. IMPORTANCE OF HYDRATION IN SPORTS

    Directory of Open Access Journals (Sweden)

    Goran Vasić

    2008-08-01

    Full Text Available Importance of hydration is detrmined by importance of functions of water in the human organism: i.e. regulation of body temperature, transport, excretion of waste materials through urine, digestion of food which is facilititated by saliva and gastric juices, maintenance of flexibility of organs and tissues About 60 % body mass of an adult person (males: 61 %, females: 54 % is made up of water. Water content of a newly born baby reaches 77 %, and it is up to 50 % in adults. It is very important for sportsmen to provide adequate hydration during and after the time of bodily activities. A symptom of water shortage is thirst. However, thirst is a late response of an organism and it occurs when dehydration has already taken place. Minimum in take of fluids in humans should range between one-and-half to two liters. It has been known for a long time that there is no success in sport without proper hydration in a sportsman.

  13. Dynamic electrowetting of sessile drops on soft surfaces

    CERN Document Server

    Dey, Ranabir; DasGupta, Sunando; Chakraborty, Suman

    2014-01-01

    Electrically-mediated dynamic wetting behaviour of sessile liquid drops on dielectric films is governed by the combined interplay of the wetting line friction and the internal viscous dissipation. We show here that such classical description of the electrospreading phenomenon, as prevalent in the contemporary literature, fails to address the electro-capillarity induced dynamic wetting of sessile drops on soft dielectrics. We first delineate the temporal variations of the macroscopic dynamic contact angle, and the contact radius, during electrowetting on rheologically tunable soft surfaces, at different applied electric potentials; subsequently, we prove through a scaling analysis, and an energy conservation approach, that the dielectric elasticity dependent, microscale elastocapillary deformation of the soft substrate, near the three-phase contact line, plays the integral role in dictating the macroscopic electrowetting behaviour. Interestingly, under such electro-elastocapillary phenomenon on soft dielectric...

  14. Achromobacter xylosoxidans keratitis after contact lens usage.

    Science.gov (United States)

    Park, Jung Hyun; Song, Nang Hee; Koh, Jae Woong

    2012-02-01

    To report on Achromobacter xylosoxidans keratitis in two healthy patients who had worn contact lenses foran extended period of time. A 36-year-old female and a 21-year-old female visited our hospital with ocular pain and blurred vision. Both patients had a history of wearing soft contact lenses for over fve years with occasional overnight wear. At the initial presentation, a slit lamp examination revealed corneal stromal infiltrations and epithelial defects with peripheral neovascularization in both patients. Microbiological examinations were performed from samples of corneal scrapings, contact lenses, contact lens cases, and solution. The culture resulting from the samples taken from the contact lenses, contact lens cases, and solution were all positive for Achromobacter xylosoxidans. Confrming that the direct cause of the keratitis was the contact lenses, the frst patient was prescribed ceftazidime and amikacin drops sensitive to Achromobacter xylosoxidans. The second patient was treated with 0.3% gatifoxacin and fortifed tobramycin drops. After treatment, the corneal epithelial defects were completely healed, and subepithelial corneal opacity was observed. Two cases of Achromobacter xylosoxidans keratitis were reported in healthy young females who wore soft contact lenses. Achromobacter xylosoxidans should be considered a rare but potentially harmful pathogen for lens-induced keratitis in healthy hosts.

  15. Soft Congruence Relations over Rings

    Directory of Open Access Journals (Sweden)

    Xiaolong Xin

    2014-01-01

    Full Text Available Molodtsov introduced the concept of soft sets, which can be seen as a new mathematical tool for dealing with uncertainty. In this paper, we initiate the study of soft congruence relations by using the soft set theory. The notions of soft quotient rings, generalized soft ideals and generalized soft quotient rings, are introduced, and several related properties are investigated. Also, we obtain a one-to-one correspondence between soft congruence relations and idealistic soft rings and a one-to-one correspondence between soft congruence relations and soft ideals. In particular, the first, second, and third soft isomorphism theorems are established, respectively.

  16. Soft congruence relations over rings.

    Science.gov (United States)

    Xin, Xiaolong; Li, Wenting

    2014-01-01

    Molodtsov introduced the concept of soft sets, which can be seen as a new mathematical tool for dealing with uncertainty. In this paper, we initiate the study of soft congruence relations by using the soft set theory. The notions of soft quotient rings, generalized soft ideals and generalized soft quotient rings, are introduced, and several related properties are investigated. Also, we obtain a one-to-one correspondence between soft congruence relations and idealistic soft rings and a one-to-one correspondence between soft congruence relations and soft ideals. In particular, the first, second, and third soft isomorphism theorems are established, respectively.

  17. Healthy Contact Lens Wear and Care

    Centers for Disease Control (CDC) Podcasts

    2014-02-04

    In this podcast, CDC’s Dr. Jennifer Cope explains some basic steps for proper wear and care of soft contact lenses.  Created: 2/4/2014 by National Center for Emerging and Zoonotic Infectious Diseases (NCEZID).   Date Released: 2/4/2014.

  18. Soft Robotics: from scientific challenges to technological applications

    Science.gov (United States)

    Laschi, C.

    2016-05-01

    Soft robotics is a recent and rapidly growing field of research, which aims at unveiling the principles for building robots that include soft materials and compliance in the interaction with the environment, so as to exploit so-called embodied intelligence and negotiate natural environment more effectively. Using soft materials for building robots poses new technological challenges: the technologies for actuating soft materials, for embedding sensors into soft robot parts, for controlling soft robots are among the main ones. This is stimulating research in many disciplines and many countries, such that a wide community is gathering around initiatives like the IEEE TAS TC on Soft Robotics and the RoboSoft CA - A Coordination Action for Soft Robotics, funded by the European Commission. Though still in its early stages of development, soft robotics is finding its way in a variety of applications, where safe contact is a main issue, in the biomedical field, as well as in exploration tasks and in the manufacturing industry. And though the development of the enabling technologies is still a priority, a fruitful loop is growing between basic research and application-oriented research in soft robotics.

  19. SEISMIC STUDIES OF MARINE GAS HYDRATES

    Institute of Scientific and Technical Information of China (English)

    SONG Haibin

    2003-01-01

    We give a brief introduction of developments of seismic methods in the studies of marine gas hydrates. Then we give an example of seismic data processing for BSRs in western Nankai accretionary prism, a typical gas hydrate distribution region. Seismic data processing is proved to be important to obtain better images of BSRs distribution. Studies of velocity structure of hydrated sediments are useful for better understanding the distribution of gas hydrates. Using full waveform inversion, we successfully derived high-resolution velocity model of a double BSR in eastern Nankai Trough area. Recent survey and research show that gas hydrates occur in the marine sediments of the South China Sea and East China Sea.But we would like to say seismic researches on gas hydrate in China are very preliminary.

  20. Development of Alaskan gas hydrate resources

    Energy Technology Data Exchange (ETDEWEB)

    Kamath, V.A.; Sharma, G.D.; Patil, S.L.

    1991-06-01

    The research undertaken in this project pertains to study of various techniques for production of natural gas from Alaskan gas hydrates such as, depressurization, injection of hot water, steam, brine, methanol and ethylene glycol solutions through experimental investigation of decomposition characteristics of hydrate cores. An experimental study has been conducted to measure the effective gas permeability changes as hydrates form in the sandpack and the results have been used to determine the reduction in the effective gas permeability of the sandpack as a function of hydrate saturation. A user friendly, interactive, menu-driven, numerical difference simulator has been developed to model the dissociation of natural gas hydrates in porous media with variable thermal properties. A numerical, finite element simulator has been developed to model the dissociation of hydrates during hot water injection process.

  1. Liquid drops on soft solids

    Science.gov (United States)

    Lubbers, Luuk A.; Weijs, Joost H.; Das, Siddhartha; Botto, Lorenzo; Andreotti, Bruno; Snoeijer, Jacco H.

    2014-03-01

    A sessile drop can elastically deform a substrate by the action of capillary forces. The typical size of the deformation is given by the ratio of surface tension and the elastic modulus, γ / E , which can reach up to 10-100 microns for soft elastomers. In this talk we theoretically show that the contact angles of drops on such a surface exhibit two transitions when increasing γ / E : (i) the microsocopic geometry of the contact line first develops a Neumann-like cusp when γ / E is of the order of few nanometers, (ii) the macroscopic angle of the drop is altered only when γ / E reaches the size of the drop. Using the same framework we then show that two neighboring drops exhibit an effective interaction, mediated by the deformation of the elastic medium. This is in analogy to the well-known Cheerios effect, where small particles at a liquid interface attract each other due to the meniscus deformations. Here we reveal the nature of drop-drop interactions on a soft substrate by combining numerical and analytical calculations.

  2. Terahertz Time Domain Spectroscopy for Structure-II Gas Hydrates

    DEFF Research Database (Denmark)

    Takeya, Kei; Zhang, Caihong; Kawayama, Iwao

    2009-01-01

    For the nondestructive inspection of gas hydrates, terahertz (THz) time-domain spectroscopy (TDS) was applied to tetrahydrofuran (THF) hydrate and propane hydrate. The absorption of propane hydrate monotonically increases with frequency, similar to the case of ice, while THF hydrate has a charact...

  3. Clinker mineral hydration at reduced relative humidities

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede

    1998-01-01

    This report deals with gas phase hydration of pure cement clinker minerals at reduced relative humidities. This is an important subject in relation to modern high performance concrete which may self-desiccate during hydration. In addition the subject has relevance to storage stability where...... prehydration may occur. In the report both theoretical considerations and experimental data are presented. It is suggested that the initiation of hydration during water vapour exposure is nucleation controlled....

  4. Impact of CO{sub 2} hydrates on ocean carbon dioxide deposition options

    Energy Technology Data Exchange (ETDEWEB)

    Lund, P.C.

    1995-04-01

    The objective of the research project described in this report was to contribute to the research on greenhouse gases and the global environment. The focus is on the concept of storing large amounts of CO{sub 2} in the ocean. The project was divided into three subtasks: (1) a comprehensive study of the thermodynamic, physical and chemical properties of the seawater/CO{sub 2}/hydrate system, (2) establishment of a micro-scale kinetic model for CO{sub 2} hydrate formation and stability, based on (1), and (3) establishment of macro-scale models for various ocean deposition options based on (2). A database of selected thermodynamic functions has been set up. A large database of oceanic data has also been made; for any given coordinates at sea a computer program provides the temperature, salinity and oxygen profiles from the sea surface to the sea floor. The kinetic model predicts the formation and pseudo-stability of a very thin hydrate film which acts as an inhibitor for diffusion of CO{sub 2} into the sea water. The model predicts that the hydrate film reduces the overall flux from a liquid CO{sub 2} source with about 90%. Thermodynamically, pure CO{sub 2} in contact with water might form hydrates at depths below about 400 m, which would indicate that hydrate formation could play a role for all ocean CO{sub 2} deposition options. However, this study shows that other mechanisms significantly reduce the role of hydrate formation. It is finally concluded that although more modelling and experimental work is required within this field of research, the hydrate film may play an important role for all options except from shallow water injection. 86 refs., 32 figs., 16 tabs.

  5. Prediction of Refrigerant Gas Hydrates Formation Conditions

    Institute of Scientific and Technical Information of China (English)

    Deqing Liang; Ruzhu Wang; Kaihua Guo; Shuanshi Fan

    2001-01-01

    A fugacity model was developed for prediction of mixed refrigerant gas hydrates formation conditions based on the molecule congregation and solution theories. In this model, g as hydrates were regarded as non-ideal solid solution composed of water groups and guest molecules, and the expressions of fugacity of guest molecules in hydrate phase was proposed accordingly. It has been shown that the developed model can indicate successfully the effect of guest-guest molecule interaction. The results showed that the model can describe better the characteristics of phase equilibrium of mixed refrigerant gas hydrates and predictions are in good agreement with experimental data.

  6. Desalination utilizing clathrate hydrates (LDRD final report).

    Energy Technology Data Exchange (ETDEWEB)

    Simmons, Blake Alexander; Bradshaw, Robert W.; Dedrick, Daniel E.; Cygan, Randall Timothy (Sandia National Laboratories, Albuquerque, NM); Greathouse, Jeffery A. (Sandia National Laboratories, Albuquerque, NM); Majzoub, Eric H. (University of Missouri, Columbia, MO)

    2008-01-01

    Advances are reported in several aspects of clathrate hydrate desalination fundamentals necessary to develop an economical means to produce municipal quantities of potable water from seawater or brackish feedstock. These aspects include the following, (1) advances in defining the most promising systems design based on new types of hydrate guest molecules, (2) selection of optimal multi-phase reactors and separation arrangements, and, (3) applicability of an inert heat exchange fluid to moderate hydrate growth, control the morphology of the solid hydrate material formed, and facilitate separation of hydrate solids from concentrated brine. The rate of R141b hydrate formation was determined and found to depend only on the degree of supercooling. The rate of R141b hydrate formation in the presence of a heat exchange fluid depended on the degree of supercooling according to the same rate equation as pure R141b with secondary dependence on salinity. Experiments demonstrated that a perfluorocarbon heat exchange fluid assisted separation of R141b hydrates from brine. Preliminary experiments using the guest species, difluoromethane, showed that hydrate formation rates were substantial at temperatures up to at least 12 C and demonstrated partial separation of water from brine. We present a detailed molecular picture of the structure and dynamics of R141b guest molecules within water cages, obtained from ab initio calculations, molecular dynamics simulations, and Raman spectroscopy. Density functional theory calculations were used to provide an energetic and molecular orbital description of R141b stability in both large and small cages in a structure II hydrate. Additionally, the hydrate of an isomer, 1,2-dichloro-1-fluoroethane, does not form at ambient conditions because of extensive overlap of electron density between guest and host. Classical molecular dynamics simulations and laboratory trials support the results for the isomer hydrate. Molecular dynamics simulations

  7. Waters of Hydration of Cupric Hydrates: A Comparison between Heating and Absorbance Methods

    Science.gov (United States)

    Barlag, Rebecca; Nyasulu, Frazier

    2011-01-01

    The empirical formulas of four cupric hydrates are determined by measuring the absorbance in aqueous solution. The Beer-Lambert Law is verified by constructing a calibration curve of absorbance versus known Cu[superscript 2+](aq) concentration. A solution of the unknown hydrate is prepared by using 0.2-0.3 g of hydrate, and water is added such…

  8. Diode laser soft-tissue surgery: advancements aimed at consistent cutting, improved clinical outcomes.

    Science.gov (United States)

    Romanos, Georgios E

    2013-01-01

    Laser dentistry and soft-tissue surgery, in particular, have become widely adopted in recent years. Significant cost reductions for dental lasers and the increasing popularity of CADCAM, among other factors, have contributed to a substantial increase in the installed base of dental lasers, especially soft-tissue lasers. New development in soft-tissue surgery, based on the modern understanding of laser-tissue interactions and contact soft-tissue surgery mechanisms, will bring a higher quality and consistency level to laser soft-tissue surgery. Recently introduced diode-laser technology enables enhanced control of side effects that result from tissue overheating and may improve soft-tissue surgical outcomes.

  9. Non-equilibrium simulation of CH4 production through the depressurization method from gas hydrate reservoirs

    Science.gov (United States)

    Qorbani, Khadijeh; Kvamme, Bjørn

    2016-04-01

    as non-equilibrium processes under local constraint of mass and heat fluxes. In this work, we have extended RCB by adding another route for dissociation or reformation of CH4-hydrate towards CH4 into the aqueous phase and water. CH4-hydrate formation and dissociation is resolved by looking at supersaturation and undersaturation with respect to thermodynamics variables. Hydrate instability due to undersaturation of CH4 in the contacting water phase is also considered. A complete non-equilibrium thermodynamic package, developed in-house, was combined with RCB to account for competing phase transitions by considering the minimization of Gibb's free energy. The energy differences were calculated from variations in chemical potentials of hydrate and hydrate formers. Mass transport, heat transport and non-equilibrium thermodynamic effects were implemented through classical nucleation theory to model the kinetic rate of hydrate phase transitions. To illustrate our implementations we ran simulations covering time-spans in the order of hundred years. CH4 production was modelled using the depressurization method, where we employed the Messoyakha field data. We discuss our implementations, as well as results obtained from simulations utilizing our modifications.

  10. Hydration in soccer: a review

    Directory of Open Access Journals (Sweden)

    Monteiro Cristiano Ralo

    2003-01-01

    Full Text Available Hydration should be considered before, during and after the exercise. This review intends to approach the main points of hydration process in soccer. The replacement of fluids during exercise is proportional to some factors, such as: exercise intensity; climatic conditions; the athlete's acclimatization; the athlete's physical conditioning; physiologic individual characteristics and the player's biomechanics. Performance is improved when players ingest not only water but also carbohydrate. The rates that carbohydrate and water are absorbed by the organism are limited by the rates of gastric emptying and intestinal absorption. The composition of drinks offered to the players should be influenced by the relative importance of the need of supplying carbohydrates or water; it should be remembered that the depletion of carbohydrate can result in fatigue and decrease of performance, but it is not usually a life-threatening condition. The addition of carbohydrate in these drinks increases the concentrations of blood glucose, increases the use of external fuel through the increase of the glucose oxidation in the muscles and it spares muscle glycogen. So, the ingestion of carbohydrate before and during the exercise can delay the emergence of fatigue and increase the players' performance. Several tactics can be used to avoid dehydration, like hyperhydration before exercise and player's acclimatization. The ideal situation to restore the player's fluid losses is between the sessions of exercises. Since soccer is a sport with quite peculiar characteristics related to hydration, the players should be concerned and educated about the importance of fluid ingestion before, during and after the exercise.

  11. Lipstick Induced Contact Leucoderma

    OpenAIRE

    Gupta Lalit Kumar; Jain Suresh Kumar; Khare Ashok Kumar

    2001-01-01

    Lipstick is a commonly used cosmetic. Its use may sometimes lead to contact dermatitis. Contact leucoderma to lipsticks however, is not common. We report a patient developing contact leucoderma to lipstick in association with contact dermatitis.

  12. Lipstick Induced Contact Leucoderma

    Directory of Open Access Journals (Sweden)

    Gupta Lalit Kumar

    2001-01-01

    Full Text Available Lipstick is a commonly used cosmetic. Its use may sometimes lead to contact dermatitis. Contact leucoderma to lipsticks however, is not common. We report a patient developing contact leucoderma to lipstick in association with contact dermatitis.

  13. Hydration behaviour of polyhydroxylated fullerenes

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Zavala, J G [Departamento de Ciencias Exactas y Tecnologicas, Centro Universitario de Los Lagos, Universidad de Guadalajara, Enrique Diaz de Leon S/N, 47460 Jalisco (Mexico); Barajas-Barraza, R E [Departamento de Matematicas y Fisica, Instituto Tecnologico y de Estudios Superiores de Occidente, Periferico Sur, Manuel Gomez MorIn No 8585, 45604 Jalisco (Mexico); Padilla-Osuna, I; Guirado-Lopez, R A, E-mail: jgrz@culagos.udg.mx, E-mail: ebarajas@iteso.mx, E-mail: ismael@ifisica.uaslp.mx, E-mail: guirado@ifisica.uaslp.mx [Instituto de Fisica ' Manuel Sandoval Vallarta' , Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi (Mexico)

    2011-10-28

    We have performed semi-empirical as well as density functional theory calculations in order to analyse the hydration properties of both bare C{sub 60} and highly hydroxylated C{sub 60}(OH){sub 26} fullerenes. In all of our calculations, a total of 42 and 98 water molecules are always surrounding our here-considered carbon nanostructures. We found different wetting properties as a function of the chemical composition and structure of the OH-molecular over-layer covering the fullerene surface. In the case of bare C{sub 60}, water adsorption reveals that the H{sub 2}O species are not uniformly arranged around the carbon network but rather forms water droplets of different sizes, clearly revealing the hydrophobic nature of the C{sub 60} structure. In contrast, in the polyhydroxylated C{sub 60}(OH){sub 26} fullerenes, the degree of wetting is strongly influenced by the precise location of the hydroxyl groups. We found that different adsorbed configurations for the OH-molecular coating can lead to the formation of partially hydrated or completely covered C{sub 60}(OH){sub 26} compounds, a result that could be used to synthesize fullerene materials with different degrees of wettability. By comparing the relative stability of our hydroxylated structures in both bare and hydrated conditions we obtain that the energy ordering of the C{sub 60}(OH){sub 26} isomers can change in the presence of water. The radial distribution function of our hydrated fullerenes reveals that water near these kinds of surfaces is densely packed. In fact, by counting the number of H{sub 2}O molecules which are adsorbed, by means of hydrogen bonds, to the surface of our more stable C{sub 60}(OH){sub 26} isomer, we found that it varies in the range of 5-10, in good agreement with experiments. Finally, by comparing the calculated optical absorption spectra of various C{sub 60}(OH){sub 26} structures in the presence and absence of water molecules, we note that only slight variations in the position and

  14. Protein dynamics: hydration and cavities

    Directory of Open Access Journals (Sweden)

    K. Heremans

    2005-08-01

    Full Text Available The temperature-pressure behavior of proteins seems to be unique among the biological macromolecules. Thermodynamic as well as kinetic data show the typical elliptical stability diagram. This may be extended by assuming that the unfolded state gives rise to volume and enthalpy-driven liquid-liquid transitions. A molecular interpretation follows from the temperature and the pressure dependence of the hydration and cavities. We suggest that positron annihilation spectroscopy can provide additional quantitative evidence for the contributions of cavities to the dynamics of proteins. Only mature amyloid fibrils that form from unfolded proteins are very resistant to pressure treatment.

  15. Concave soft sets, critical soft points, and union-soft ideals of ordered semigroups.

    Science.gov (United States)

    Jun, Young Bae; Song, Seok Zun; Muhiuddin, G

    2014-01-01

    The notions of union-soft semigroups, union-soft l-ideals, and union-soft r-ideals are introduced, and related properties are investigated. Characterizations of a union-soft semigroup, a union-soft l-ideal, and a union-soft r-ideal are provided. The concepts of union-soft products and union-soft semiprime soft sets are introduced, and their properties related to union-soft l-ideals and union-soft r-ideals are investigated. Using the notions of union-soft l-ideals and union-soft r-ideals, conditions for an ordered semigroup to be regular are considered. The concepts of concave soft sets and critical soft points are introduced, and their properties are discussed.

  16. Concave Soft Sets, Critical Soft Points, and Union-Soft Ideals of Ordered Semigroups

    Directory of Open Access Journals (Sweden)

    Young Bae Jun

    2014-01-01

    Full Text Available The notions of union-soft semigroups, union-soft l-ideals, and union-soft r-ideals are introduced, and related properties are investigated. Characterizations of a union-soft semigroup, a union-soft l-ideal, and a union-soft r-ideal are provided. The concepts of union-soft products and union-soft semiprime soft sets are introduced, and their properties related to union-soft l-ideals and union-soft r-ideals are investigated. Using the notions of union-soft l-ideals and union-soft r-ideals, conditions for an ordered semigroup to be regular are considered. The concepts of concave soft sets and critical soft points are introduced, and their properties are discussed.

  17. Formation rate of natural gas hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Mork, Marit

    2002-07-01

    The rate of methane hydrate and natural gas hydrate formation was measured in a 9.5 litre stirred tank reactor of standard design. The experiments were performed to better understand the performance and scale-up of a reactor for continuous production of natural gas hydrates. The hydrate formation rate was measured at steady-state conditions at pressures between 70 and 90 bar and temperatures between 7 and 15 deg C. Between 44 and 56 % of the gas continuously supplied to the reactor was converted to hydrate. The experimental results show that the rate of hydrate formation is strongly influenced by gas injection rate and pressure. The effect of stirring rate is less significant and subcooling has no observable effect on the formation rate. Hydrate crystal concentration and gas composition do not influence the hydrate formation rate. Observations of produced hydrate crystals indicate that the crystals are elongated, about 5 micron in diameter and 10 micron long. Analysis of the results shows that the rate of hydrate formation is dominated by gas-liquid mass transfer. A mass transfer model, the bubble-to-crystal model, was developed for the hydrate formation rate in a continuous stirred tank reactor, given in terms of concentration driving force and an overall mass transfer coefficient. The driving force is the difference between the gas concentration at the gas-liquid interface and at the hydrate crystal surface. These concentrations correspond to the solubility of gas in water at experimental temperature and pressure and the solubility of gas at hydrate equilibrium temperature and experimental pressure, respectively. The overall mass transfer coefficient is expressed in terms of superficial gas velocity and impeller power consumption, parameters commonly used in study of stirred tank reactors. Experiments and modeling show that the stirred tank reactor has a considerable potential for increased production capacity. However, at higher hydrate production rates the

  18. EDITORIAL: Close contact Close contact

    Science.gov (United States)

    Demming, Anna

    2010-07-01

    The development of scanning probe techniques, such as scanning tunnelling microscopy [1], has often been touted as the catalyst for the surge in activity and progress in nanoscale science and technology. Images of nanoscale structural detail have served as an invaluable investigative resource and continue to fascinate with the fantastical reality of an intricate nether world existing all around us, but hidden from view of the naked eye by a disparity in scale. As is so often the case, the invention of the scanning tunnelling microscope heralded far more than just a useful new apparatus, it demonstrated the scope for exploiting the subtleties of electronic contact. The shrinking of electronic devices has been a driving force for research into molecular electronics, in which an understanding of the nature of electronic contact at junctions is crucial. In response, the number of experimental techniques in molecular electronics has increased rapidly in recent years. Scanning tunnelling microscopes have been used to study electron transfer through molecular films on a conducting substrate, and the need to monitor the contact force of scanning tunnelling electrodes led to the use of atomic force microscopy probes coated in a conducting layer as studied by Cui and colleagues in Arizona [2]. In this issue a collaboration of researchers at Delft University and Leiden University in the Netherlands report a new device architecture for the independent mechanical and electrostatic tuning of nanoscale charge transport, which will enable thorough studies of molecular transport in the future [3]. Scanning probes can also be used to pattern surfaces, such as through spatially-localized Suzuki and Heck reactions in chemical scanning probe lithography. Mechanistic aspects of spatially confined Suzuki and Heck chemistry are also reported in this issue by researchers in Oxford [4]. All these developments in molecular electronics fabrication and characterization provide alternative

  19. Power profiles of multifocal contact lenses and their interpretation.

    Science.gov (United States)

    Plainis, Sotiris; Atchison, David A; Charman, W Neil

    2013-10-01

    Many contact lens (CL) manufacturers produce simultaneous-image lenses in which power varies either smoothly or discontinuously with zonal radius. We present in vitro measurements of some recent CLs and discuss how power profiles might be approximated in terms of nominal distance corrections, near additions, and on-eye visual performance. Fully hydrated soft, simultaneous-image CLs from four manufacturers (Air Optix AQUA, Alcon; PureVision multifocal, Bausch & Lomb; Acuvue OASYS for Presbyopia, Vistakon; Biofinity multifocal- "D" design, Cooper Vision) were measured with a Phase focus Lens Profiler (Phase Focus Ltd., Sheffield, UK) in a wet cell and powers were corrected to powers in air. All lenses had zero labeled power for distance. Sagittal power profiles revealed that the "low" add PureVision and Air Optix lenses exhibit smooth (parabolic) profiles, corresponding to negative spherical aberration. The "mid" and "high" add PureVision and Air Optix lenses have bi-aspheric designs, leading to different rates of power change for the central and peripheral portions. All OASYS lenses display a series of concentric zones, separated by abrupt discontinuities; individual profiles can be constrained between two parabolically decreasing curves, each giving a valid description of the power changes over alternate annular zones. Biofinity lenses have constant power over the central circular region of radius 1.5 mm, followed by an annular zone where the power increases approximately linearly, the gradient increasing with the add power, and finally an outer zone showing a slow, linear increase in power with a gradient being almost independent of the add power. The variation in power across the simultaneous-image lenses produces enhanced depth of focus. The through-focus nature of the image, which influences the "best focus" (distance correction) and the reading addition, will vary with several factors, including lens centration, the wearer's pupil diameter, and ocular

  20. Simple Ontology Format (SOFT)

    Energy Technology Data Exchange (ETDEWEB)

    2011-10-01

    Simple Ontology Format (SOFT) library and file format specification provides a set of simple tools for developing and maintaining ontologies. The library, implemented as a perl module, supports parsing and verification of the files in SOFt format, operations with ontologies (adding, removing, or filtering of entities), and converting of ontologies into other formats. SOFT allows users to quickly create ontologies using only a basic text editor, verify it, and portray it in a graph layout system using customized styles.

  1. Dynamics of a photoexcited hydrated electron

    NARCIS (Netherlands)

    Pshenichnikov, M.S.; Baltuška, A.; Wiersma, D.A.; Kärtner, F.X.

    2004-01-01

    Combining photon-echo and frequency-resolved pump-probe techniques with extremely short laser pulses that consist of only few optical cycles, we investigate the dynamics of the equilibrated hydrated electron. The pure dephasing time of the hydrated electron deduced from the photon-echo measurements

  2. Gas hydrate inhibition of drilling fluid additives

    Energy Technology Data Exchange (ETDEWEB)

    Xiaolan, L.; Baojiang, S.; Shaoran, R. [China Univ. of Petroleum, Dongying (China). Inst. of Petroleum Engineering

    2008-07-01

    Gas hydrates that form during offshore well drilling can have adverse impacts on well operational safety. The hydrates typically form in the risers and the annulus between the casing and the drillstring, and can stop the circulation of drilling fluids. In this study, experiments were conducted to measure the effect of drilling fluid additives on hydrate inhibition. Polyalcohols, well-stability control agents, lubricating agents, and polymeric materials were investigated in a stirred tank reactor at temperatures ranging from -10 degree C to 60 degrees C. Pressure, temperature, and torque were used to detect onset points of hydrate formation and dissociation. The inhibitive effect of the additives on hydrate formation was quantified. Phase boundary shifts were measured in terms of temperature difference or sub-cooling gained when chemicals were added to pure water. Results showed that the multiple hydroxyl groups in polyalcohol chemicals significantly inhibited hydrate formation. Polymeric and polyacrylamide materials had only a small impact on hydrate formation, while sulfonated methyl tannins were found to increase hydrate formation. 6 refs., 1 tab., 4 figs.

  3. Hydration shells exchange charge with their protein

    DEFF Research Database (Denmark)

    Abitan, Haim; Lindgård, Per-Anker; Nielsen, Bjørn Gilbert;

    2010-01-01

    Investigation of the interaction between a protein and its hydration shells is an experimental and theoretical challenge. Here, we used ultrasonic pressure waves in aqueous solutions of a protein to explore the conformational states of the protein and its interaction with its hydration shells. In...

  4. A new geotechnical gas hydrates research laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Grozic, J.L.H. [Calgary Univ., AB (Canada)

    2003-07-01

    Gas hydrates encapsulate natural gas molecules in a very compact form, as ice-like compounds composed of water molecules. Permafrost environments and offshore areas contain vast quantities of gas hydrates within soil and rock. This paper describes the role played by gas hydrates in submarine slope instability, their potential as a sustainable energy source, and their effects on global climate change. A new state-of-the-art laboratory located at the University of Calgary, which was developed to study the geomechanical behaviour of gas hydrate-sediment mixtures, was also presented. A specialized high pressure low temperature triaxial apparatus capable of performing a suite of tests on gas hydrate-sediment mixtures is housed in this laboratory. Extensive renovations were required in order to enable the use of methane gas to simulate natural hydrate formation conditions. The laboratory is specifically designed to examine the properties and behaviour of reconstituted gas hydrate-sediment mixtures and natural gas hydrate core samples. 26 refs., 9 figs.

  5. Investigations into surfactant/gas hydrate relationship

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, Rudy; Zhang, Guochang; Dearman, Jennifer; Woods, Charles [Swalm School of Chemical Engineering, Mississippi State University, Mississippi State, MS 39762 (United States)

    2007-03-15

    Gas hydrates have unique physical properties portending useful industrial applications of gas storage, gas separation, or water desalination. When gas hydrates were found in the early 1990s to occur naturally and abundantly in seafloors, three other primary interests and concerns emerged: potential new energy source, climate threat from their greenhouse gases, and seafloor instabilities. This paper presents research showing how anionic synthetic surfactants helped develop an industrial gas hydrate storage process for natural gas and how naturally-occurring in-situ anionic biosurfactants influence the formation and placement of gas hydrates in ocean sediments. The catalytic effects, mechanisms, and surface specificities imparted by synthetic surfactants in the gas storage process and imparted by biosurfactants in porous media are discussed. The Bacillus subtilis bacterium that is indigenous to gas hydrate mounds in the Gulf of Mexico was cultured in the laboratory. Its biosurfactant was separated and found to catalyze gas hydrates in porous media. The experiments indicate that seafloor-biosurfactants can be produced rapidly in-situ to achieve threshold concentrations whereby hydrates are promoted. The biosurfactants accumulate and promote hydrate formation on specific mineral surfaces such as sodium montmorillonite. (author)

  6. Raman Spectroscopic Studies of Methane Gas Hydrates

    DEFF Research Database (Denmark)

    Hansen, Susanne Brunsgaard; Berg, Rolf W.

    2009-01-01

    A brief review of the Raman spectroscopic studies of methane gas hydrates is given, supported by some new measurements done in our laboratory.......A brief review of the Raman spectroscopic studies of methane gas hydrates is given, supported by some new measurements done in our laboratory....

  7. Flavoured Soft Leptogenesis

    CERN Document Server

    Fong, Chee Sheng

    2008-01-01

    We study the impact of flavour in ``soft leptogenesis'' (leptogenesis induced by soft supersymmetry breaking terms). We address the question of how flavour effects can affect the region of parameters in which successful soft leptogenesis induced by CP violation in the right-handed sneutrino mixing is possible. We find that for decays which occur in the intermediate to strong washout regimes for all flavours, the produced total $B-L$ asymmetry can be up to a factor ${\\cal O}(30)$ larger than the one predicted with flavour effects being neglected. This enhancement, permits slightly larger values of the required lepton violating soft bilinear term.

  8. Soft matter physics

    CERN Document Server

    Doi, Masao

    2013-01-01

    Soft matter (polymers, colloids, surfactants and liquid crystals) are an important class of materials in modern technology. They also form the basis of many future technologies, for example in medical and environmental applications. Soft matter shows complex behaviour between fluids and solids, and used to be a synonym of complex materials. Due to the developments of the past two decades, soft condensed matter can now be discussed on the same sound physical basis as solid condensedmatter. The purpose of this book is to provide an overview of soft matter for undergraduate and graduate students

  9. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Donn McGuire; Steve Runyon; Richard Sigal; Bill Liddell; Thomas Williams; George Moridis

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the final stages of a cost-shared partnership between Maurer Technology, Noble Corporation, Anadarko Petroleum, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. Hot Ice No. 1 was planned to test the Ugnu and West Sak sequences for gas hydrates and a concomitant free gas accumulation on Anadarko's 100% working interest acreage in section 30 of Township 9N, Range 8E of the Harrison Bay quadrangle of the North Slope of Alaska. The Ugnu and West Sak intervals are favorably positioned in the hydrate-stability zone over an area extending from Anadarko's acreage westward to the vicinity of the aforementioned gas-hydrate occurrences. This suggests that a large, north-to-south trending gas-hydrate accumulation may exist in that area. The presence of gas shows in the Ugnu and West Sak reservoirs in wells situated eastward and down dip of the Hot Ice location indicate that a free-gas accumulation may be trapped by gas hydrates. The Hot Ice No. 1 well was designed to core from the surface to the base of the West Sak interval using the

  10. Negative printing by soft lithography.

    Science.gov (United States)

    Ong, Jason Kee Yang; Moore, David; Kane, Jennifer; Saraf, Ravi F

    2014-08-27

    In inkless microcontact printing (IμCP) by soft lithography, the poly(dimethylsiloxane) (PDMS) stamp transfers uncured polymer to a substrate corresponding to its pattern. The spontaneous diffusion of PDMS oligomers to the surface of the stamp that gives rise to this deleterious side effect has been leveraged to fabricate a variety of devices, such as organic thin film transistors, single-electron devices, and biomolecular chips. Here we report an anomalous observation on a partially cured PDMS stamp where the transfer of oligomers onto Au occurred on regions that were not in contact with the stamp, while the surface in contact with the stamp was pristine with no polymer. On the SiO2 surface of the same chip, as expected, the transfer of PDMS occurred exclusively on regions in contact with the stamp. The printing on Au was quantified by a novel method where the submonolayer of PDMS transfer was measured by probing the local electrochemical passivation of the Au. The local transfer of polymer on SiO2 (and also Au) was measured by selective deposition of Au nanoparticle necklaces that exclusively deposited on PDMS at submonolayer sensitivity. It was discovered that the selectivity and sharpness of PDMS deposition on Au for inkless printing (i.e., negative) is significantly better than the traditional (positive) microcontact printing where the stamp is "inked" with low molecular weight PDMS.

  11. Compound Natural Gas Hydrate: A Natural System for Separation of Hydrate-Forming Gases

    Science.gov (United States)

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

    2007-12-01

    Natural processes that separate materials from a mixture may exert a major influence on the development of the atmospheres and surfaces of planets, moons, and other planetary bodies. Natural distillation and gravity separation, amongst others, are well known means of differentiating materials through liquid-gas partitioning. One of the least known attributes of clathrate (gas) hydrates is their potential effect on the evolution of planetary system oceans and atmospheres. Gas hydrates separate gases from mixtures of gases by concentrating preferred hydrate-forming materials (HFM) guests within the water-molecule cage structure of crystalline hydrate. Different HFMs have very different fields of stability. When multiple hydrate formers are present, a preference series based on their selective uptake exists. Compound hydrate, which is formed from two or more species of HFM, extract preferred HFM from a mixture in very different proportions to their relative percentages of the original mixture. These compound hydrates can have different formation and dissociation conditions depending on the evolution of the environment. That is, the phase boundary of the compound hydrate that is required for dissociation lies along a lower pressure - higher temperature course. Compound hydrates respond to variations in temperature, pressure, and HFM composition. On Earth, the primary naturally occurring hydrate of interest to global climate modeling is methane hydrate. Oceanic hydrate on Earth is the largest store of carbon in the biosphere that is immediately reactive to environmental change, and is capable of releasing large amounts of methane into the atmosphere over a short geological time span. Hydrate formation is essentially metastable and is very sensitive to environmental change and to gas flux. Where natural variations in temperature and pressure varies so that hydrate will form and dissociate in some cyclical manner, such as in oceans where sea level is capable of rising and

  12. Overview on Hydrate Coring, Handling and Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Jon Burger; Deepak Gupta; Patrick Jacobs; John Shillinglaw

    2003-06-30

    Gas hydrates are crystalline, ice-like compounds of gas and water molecules that are formed under certain thermodynamic conditions. Hydrate deposits occur naturally within ocean sediments just below the sea floor at temperatures and pressures existing below about 500 meters water depth. Gas hydrate is also stable in conjunction with the permafrost in the Arctic. Most marine gas hydrate is formed of microbially generated gas. It binds huge amounts of methane into the sediments. Worldwide, gas hydrate is estimated to hold about 1016 kg of organic carbon in the form of methane (Kvenvolden et al., 1993). Gas hydrate is one of the fossil fuel resources that is yet untapped, but may play a major role in meeting the energy challenge of this century. In June 2002, Westport Technology Center was requested by the Department of Energy (DOE) to prepare a ''Best Practices Manual on Gas Hydrate Coring, Handling and Analysis'' under Award No. DE-FC26-02NT41327. The scope of the task was specifically targeted for coring sediments with hydrates in Alaska, the Gulf of Mexico (GOM) and from the present Ocean Drilling Program (ODP) drillship. The specific subjects under this scope were defined in 3 stages as follows: Stage 1: Collect information on coring sediments with hydrates, core handling, core preservation, sample transportation, analysis of the core, and long term preservation. Stage 2: Provide copies of the first draft to a list of experts and stakeholders designated by DOE. Stage 3: Produce a second draft of the manual with benefit of input from external review for delivery. The manual provides an overview of existing information available in the published literature and reports on coring, analysis, preservation and transport of gas hydrates for laboratory analysis as of June 2003. The manual was delivered as draft version 3 to the DOE Project Manager for distribution in July 2003. This Final Report is provided for records purposes.

  13. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Thomas E. Williams; Keith Millheim; Bill Liddell

    2005-03-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Oil-field engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in Arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrates agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is a cost-shared partnership between Maurer Technology, Anadarko Petroleum, Noble Corporation, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to help identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. As part of the project work scope, team members drilled and cored the HOT ICE No. 1 on Anadarko leases beginning in January 2003 and completed in March 2004. Due to scheduling constraints imposed by the Arctic drilling season, operations at the site were suspended between April 21, 2003 and January 30, 2004. An on-site core analysis laboratory was designed, constructed and used for determining physical characteristics of frozen core immediately after it was retrieved from the well. The well was drilled from a new and innovative Anadarko Arctic Platform that has a greatly reduced footprint and environmental impact. Final efforts of the project were to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists for future hydrate operations. Unfortunately, no gas hydrates were encountered in this well; however, a wealth of information was generated

  14. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Thomas E. Williams; Keith Millheim; Buddy King

    2004-07-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the final stages of a cost shared partnership between Maurer Technology, Noble Corporation, Anadarko Petroleum, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. The work scope drilled and cored a well The HOT ICE No.1 on Anadarko leases beginning in FY 2003 and completed in 2004. An on-site core analysis laboratory was built and utilized for determining the physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. The final efforts of the project are to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists developing reservoir models. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained in this report.

  15. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Thomas E. Williams; Keith Millheim; Buddy King

    2004-06-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the final stages of a cost shared partnership between Maurer Technology, Noble Corporation, Anadarko Petroleum, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. The work scope drilled and cored a well The HOT ICE No.1 on Anadarko leases beginning in FY 2003 and completed in 2004. An on-site core analysis laboratory was built and utilized for determining the physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. The final efforts of the project are to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists developing reservoir models. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained in this report.

  16. Experimental Study of Natural Gas Storage in Hydrates

    Institute of Scientific and Technical Information of China (English)

    孙志高; 王如竹; 郭开华; 樊栓狮

    2004-01-01

    Hydrate formation rate plays an important role in the making of hydrates for natural gas storage. The effect of sodium dodecyl sulfate (SDS), alkyl polysaccharide glycoside (APG) and cyclopentane (CP) on natural gas hydrate formation rate, induction time and storage capacity was studied. Micellar surfactant solutions were found to increase hydrate formation rate in a quiescent system and improve hydrate formation rate and natural gas storage capacity. The process of hydrate formation includes two stages with surfactant presence. Hydrate forms quickly in the first stage, and then the formation rate is slowed down. Surfactants (SDS or APG) reduce the induction time of hydrate formation. The effect of an anionic surfactant (SDS) on gas storage in hydrates is more pronounced compared to a nonionic surfactant (APG). CP also reduces the induction time of hydrate formation, but can not improve the natural gas storage capacity in hydrates.

  17. Methane Recovery from Hydrate-bearing Sediments

    Energy Technology Data Exchange (ETDEWEB)

    J. Carlos Santamarina; Costas Tsouris

    2011-04-30

    Gas hydrates are crystalline compounds made of gas and water molecules. Methane hydrates are found in marine sediments and permafrost regions; extensive amounts of methane are trapped in the form of hydrates. Methane hydrate can be an energy resource, contribute to global warming, or cause seafloor instability. This study placed emphasis on gas recovery from hydrate bearing sediments and related phenomena. The unique behavior of hydrate-bearing sediments required the development of special research tools, including new numerical algorithms (tube- and pore-network models) and experimental devices (high pressure chambers and micromodels). Therefore, the research methodology combined experimental studies, particle-scale numerical simulations, and macro-scale analyses of coupled processes. Research conducted as part of this project started with hydrate formation in sediment pores and extended to production methods and emergent phenomena. In particular, the scope of the work addressed: (1) hydrate formation and growth in pores, the assessment of formation rate, tensile/adhesive strength and their impact on sediment-scale properties, including volume change during hydrate formation and dissociation; (2) the effect of physical properties such as gas solubility, salinity, pore size, and mixed gas conditions on hydrate formation and dissociation, and it implications such as oscillatory transient hydrate formation, dissolution within the hydrate stability field, initial hydrate lens formation, and phase boundary changes in real field situations; (3) fluid conductivity in relation to pore size distribution and spatial correlation and the emergence of phenomena such as flow focusing; (4) mixed fluid flow, with special emphasis on differences between invading gas and nucleating gas, implications on relative gas conductivity for reservoir simulations, and gas recovery efficiency; (5) identification of advantages and limitations in different gas production strategies with

  18. Imaging bacterial spores by soft-x-ray microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stead, A.D.; Ford, T.W. [Univ. of London, Surrey (United Kingdom); Judge, J. [Unilever plc, Sharnbrook (United Kingdom)] [and others

    1997-04-01

    Bacterial spores are able to survive dehydration, but neither the physiological nor structural basis of this have been fully elucidated. Furthermore, once hydrated, spores often require activation before they will germinate. Several treatments can be used to activate spores, but in the case of Bacillus subtlis the most effective is heat treatment. The physiological mechanism associated with activation is also not understood, but some workers suggest that the loss of calcium from the spores may be critical. However, just prior to germination, the spores change from being phase bright to phase dark when viewed by light microscopy. Imaging spores by soft x-ray microscopy is possible without fixation. Thus, in contrast to electron microscopy, it is possible to compare the structure of dehydrated and hydrated spores in a manner not possible previously. A further advantage is that it is possible to monitor individual spores by phase contrast light microscopy immediately prior to imaging with soft x-rays; whereas, with both electron microscopy and biochemical studies, it is a population of spores being studied without knowledge of the phase characteristics of individual spores. This study has therefore tried to compare dehydrated and hydrated spores and to determine if there is a mass loss from individual spores as they pass the transition from being phase bright to phase dark.

  19. learning and soft skills

    DEFF Research Database (Denmark)

    Rasmussen, Lauge Baungaard

    2000-01-01

    Learning of soft skills are becoming more and more necessary due to the complexe development of modern companies and their environments. However, there seems to be a 'gap' between intentions and reality regarding need of soft skills and the possiblities to be educated in this subject in particular...

  20. learning and soft skills

    DEFF Research Database (Denmark)

    Rasmussen, Lauge Baungaard

    2000-01-01

    Learning of soft skills are becoming more and more necessary due to the complexe development of modern companies and their environments. However, there seems to be a 'gap' between intentions and reality regarding need of soft skills and the possiblities to be educated in this subject in particular...

  1. Embodying Soft Wearables Research

    DEFF Research Database (Denmark)

    Tomico, Oscar; Wilde, Danielle

    2016-01-01

    of soft wearables. Throughout, we will experiment with how embodied design research techniques might be shared, developed, and used as direct and unmediated vehicles for their own reporting. Rather than engage in oral presentations, participants will lead each other through a proven embodied method...... and knowledge transfer in the context of soft wearables....

  2. Model Analysis of Initial Hydration and Structure Forming of Portland Cement

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The auto efficiently hydration heat arrangement and the non-contacting electrical resistivity device were used to test the thermology effect and the resistivity variation of Portland cement hydration.The structure forming model of Portland cement initial hydration was established through the systematical experiments with different cements, the amount of mixing water and the chemical admixture. The experimental results show that, the structure forming model of cement could be divided into three stages, i e, solution-solution equilibrium period, structure forming period and structure stabilizing period. Along with the increase of mixing water, the time of inflexion appeared is in advance for thermal process of cement hydration and worsened for the structure forming process. Comparison with the control specimen, adding Na2SO4 makes the minimum critical point lower, the flattening period shorter and the growing slope after stage one steeper. So the hydration and structure forming process of Portland cement could be described more exactly by applying the thermal model and the structure-forming model.

  3. Mass fractionation of noble gases in synthetic methane hydrate: Implications for naturally occurring gas hydrate dissociation

    Science.gov (United States)

    Hunt, Andrew G.; Stern, Laura; Pohlman, John W.; Ruppel, Carolyn; Moscati, Richard J.; Landis, Gary P.

    2013-01-01

    As a consequence of contemporary or longer term (since 15 ka) climate warming, gas hydrates in some settings may presently be dissociating and releasing methane and other gases to the ocean-atmosphere system. A key challenge in assessing the impact of dissociating gas hydrates on global atmospheric methane is the lack of a technique able to distinguish between methane recently released from gas hydrates and methane emitted from leaky thermogenic reservoirs, shallow sediments (some newly thawed), coal beds, and other sources. Carbon and deuterium stable isotopic fractionation during methane formation provides a first-order constraint on the processes (microbial or thermogenic) of methane generation. However, because gas hydrate formation and dissociation do not cause significant isotopic fractionation, a stable isotope-based hydrate-source determination is not possible. Here, we investigate patterns of mass-dependent noble gas fractionation within the gas hydrate lattice to fingerprint methane released from gas hydrates. Starting with synthetic gas hydrate formed under laboratory conditions, we document complex noble gas fractionation patterns in the gases liberated during dissociation and explore the effects of aging and storage (e.g., in liquid nitrogen), as well as sampling and preservation procedures. The laboratory results confirm a unique noble gas fractionation pattern for gas hydrates, one that shows promise in evaluating modern natural gas seeps for a signature associated with gas hydrate dissociation.

  4. Contact lenses fitting after intracorneal ring segments implantation in keratoconus

    Directory of Open Access Journals (Sweden)

    Luciane Bugmann Moreira

    2013-08-01

    Full Text Available PURPOSE: Evaluate contact lenses fitting after intracorneal ring implantation for keratoconus, its visual acuity and comfort. METHODS: Retrospective study of patients undergoing contact lenses fitting, after intracorneal ring for keratoconus. The criterion for contact lens fitting was unsatisfactory visual acuity with spectacle correction as referred by the patients. All patients were intolerants to contact lenses prior to intracorneal implantation. Visual acuity analysis was done by conversion of Snellen to logMAR scales. The comfort was evaluated according subjective questioning of good, medium or poor comfort. RESULTS: Nineteen patients were included in the study. Two patients (10.5% did not achieved good comfort with contact lenses and underwent penetrating keratoplasties. All the others 17 patients showed good or medium comfort. Four rigid gas-permeable contact lenses were fitted, one piggyback approach, 3 toric soft contact lenses, 2 soft lenses specially design for keratoconus and 7 disposable soft lenses. The average visual acuity improved from 0.77 ± 0.37 to 0.19 ± 0.13 logMAR units after contact lenses fitting. CONCLUSION: Contact lens fitting after intracorneal ring is possible, provides good comfort, improves visual acuity, and therefore, may postpone the need for penetrating keratoplasty.

  5. Evaluating six soft approaches

    Directory of Open Access Journals (Sweden)

    Lene Sørensen

    2008-09-01

    Full Text Available The paper introduces and evaluates six soft approaches used in strategy development and planning. We take a planner’s perspective on discussing the concepts of strategy development and planning. This means that we see strategy development and planning as learning processes based on Ackoff’s interactive planning principles to be supported by soft approaches in carrying out the principles in action. These six soft approaches are suitable for supporting various steps of the strategy development and planning process. These are the SWOT analysis, the Future Workshop, the Scenario methodology, Strategic Option Development and Analysis, Strategic Choice Approach and Soft Systems Methodology. Evaluations of each methodology are carried out using a conceptual framework in which the organisation, the result, the process and the technology of the specific approach are taken into consideration. Using such a conceptual framework for evaluations of soft approaches increases the understanding of them, their transparency, and their usability in practice.

  6. Hydration Properties of Ground Granulated Blast-Furnace Slag (GGBS Under Different Hydration Environments

    Directory of Open Access Journals (Sweden)

    Shuhua LIU

    2017-02-01

    Full Text Available The hydration properties of various cementitious materials containing Ground Granulated Blast-furnace Slag (GGBS, two alkali-activated slag cements (AAS-1 and AAS-2 in which sodium silicate and sodium hydroxide act as alkaline activators respectively, supersulfated cement (SSC and slag Portland cement(PSC, are compared with ordinary Portland cement (OPC to investigate the effect of activating environment on the hydration properties in this study by determining the compressive strength of the pastes, the hydration heat of binders within 96 hours, and the hydration products at age of 28 days. The results show that C-S-H gels are the main hydrated products for all cementitious systems containing GGBS. Ca(OH2 is the hydration products of OPC and PSC paste. However, ettringite and gypsum crystals instead of Ca(OH2 are detected in SSC paste. Additionally, tobermorite, a crystalline C-S-H, and calcite are hydrated products in AAS-1. Tobermorite, cowlesite and calcite are hydrated products of AAS-2 as well. Based on strength results, AAS-1 paste exhibits the highest compressive strength followed by POC, PSC, SSC in order at all testing ages and AAS-2 give the lowest compressive strength except for the early age at 3 days, which is higher than SSC but still lower than PSC. From hydration heat analysis, alkalinity in the reaction solution is a vital factor influencing the initial hydration rate and the initial hydration rate from higher to lower is AAS-2, AAS-1, OPC, PSC and SSC. Although AAS possesses a faster reaction rate in the initial hours, cumulative hydration heat of AAS is comparably lower than that of OPC, but higher than those of PSC and SSC in turn, which indicates that the hydration heat of clinkers is much higher than that of slag.DOI: http://dx.doi.org/10.5755/j01.ms.23.1.14934

  7. Pf1 bacteriophage hydration by magic angle spinning solid-state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Sergeyev, Ivan V.; Bahri, Salima; McDermott, Ann E., E-mail: aem5@columbia.edu [Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027 (United States); Day, Loren A. [Public Health Research Institute, Rutgers University, 225 Warren St., Newark, New Jersey 07103 (United States)

    2014-12-14

    High resolution two- and three-dimensional heteronuclear correlation spectroscopy ({sup 1}H–{sup 13}C, {sup 1}H–{sup 15}N, and {sup 1}H–{sup 13}C–{sup 13}C HETCOR) has provided a detailed characterization of the internal and external hydration water of the Pf1 virion. This long and slender virion (2000 nm × 7 nm) contains highly stretched DNA within a capsid of small protein subunits, each only 46 amino acid residues. HETCOR cross-peaks have been unambiguously assigned to 25 amino acids, including most external residues 1–21 as well as residues 39–40 and 43–46 deep inside the virion. In addition, the deoxyribose rings of the DNA near the virion axis are in contact with water. The sets of cross-peaks to the DNA and to all 25 amino acid residues were from the same hydration water {sup 1}H resonance; some of the assigned residues do not have exchangeable side-chain protons. A mapping of the contacts onto structural models indicates the presence of water “tunnels” through a highly hydrophobic region of the capsid. The present results significantly extend and modify results from a lower resolution study, and yield a comprehensive hydration surface map of Pf1. In addition, the internal water could be distinguished from external hydration water by means of paramagnetic relaxation enhancement. The internal water population may serve as a conveniently localized magnetization reservoir for structural studies.

  8. Dependence of Softness on Fabric Surface Quality and Compressibility

    Institute of Scientific and Technical Information of China (English)

    HU Ji-yong; DING Xin; WANG Ru-bin

    2006-01-01

    The term "softness" is loosely used to describe the physical as well as sensory attributes of fabric and other textiles, and several psychophysical evaluation methods as well as its predicting equations exist. However, the information for physiological mechanism of fabric softness is lack. To explain the biomechanical and the potential neurophysiological phenomenon for exploring fabric softness,accompanying to the procedures in manual exploration for softness and the anatomical multilayer structures of human finger, a contact finite element (FE) model between finger and fabric is made to conduct an active contact analysis. In present FE model, the effect of surface friction index,compression modulus, Poisson's ratio of fabric on softness discrimination is investigated. The interests are in the contributions of these fabric property variables to contact area, interfacial friction shear stress and contact pressure distributions, which are significant cognitive variables or stimulus parameters in peripheral neural levels. The mechanistic data for fabric specimens indicates that the basis for the perception of softness of flexible and bulk fabric is likely on the spatial variation of pressure on the skin (or,equivalently the skin displacement and its derivatives)resulting from surface friction phenomenon and compression property of fabric. In present model, however, the effect of Poisson's ratio on the total force exerted by fingertip is not significant statistically. Therefore, compression modulus of fabric is, not the only underlying physical variable accounting for peripheral neural response, and also the surface friction phenomenon plays an important role in feeltouch softness of fabric, i.e. the compressibility and surface properties of fabric are the necessary physical variables involved for the haptic rendering of its softness.

  9. Detection and Production of Methane Hydrate

    Energy Technology Data Exchange (ETDEWEB)

    George Hirasaki; Walter Chapman; Gerald Dickens; Colin Zelt; Brandon Dugan; Kishore Mohanty; Priyank Jaiswal

    2011-12-31

    This project seeks to understand regional differences in gas hydrate systems from the perspective of as an energy resource, geohazard, and long-term climate influence. Specifically, the effort will: (1) collect data and conceptual models that targets causes of gas hydrate variance, (2) construct numerical models that explain and predict regional-scale gas hydrate differences in 2-dimensions with minimal 'free parameters', (3) simulate hydrocarbon production from various gas hydrate systems to establish promising resource characteristics, (4) perturb different gas hydrate systems to assess potential impacts of hot fluids on seafloor stability and well stability, and (5) develop geophysical approaches that enable remote quantification of gas hydrate heterogeneities so that they can be characterized with minimal costly drilling. Our integrated program takes advantage of the fact that we have a close working team comprised of experts in distinct disciplines. The expected outcomes of this project are improved exploration and production technology for production of natural gas from methane hydrates and improved safety through understanding of seafloor and well bore stability in the presence of hydrates. The scope of this project was to more fully characterize, understand, and appreciate fundamental differences in the amount and distribution of gas hydrate and how this would affect the production potential of a hydrate accumulation in the marine environment. The effort combines existing information from locations in the ocean that are dominated by low permeability sediments with small amounts of high permeability sediments, one permafrost location where extensive hydrates exist in reservoir quality rocks and other locations deemed by mutual agreement of DOE and Rice to be appropriate. The initial ocean locations were Blake Ridge, Hydrate Ridge, Peru Margin and GOM. The permafrost location was Mallik. Although the ultimate goal of the project was to understand

  10. Prospecting for marine gas hydrate resources

    Science.gov (United States)

    Boswell, Ray; Shipp, Craig; Reichel, Thomas; Shelander, Dianna; Saeki, Tetsuo; Frye, Matthew; Shedd, William; Collett, Timothy S.; McConnell, Daniel R.

    2016-01-01

    As gas hydrate energy assessment matures worldwide, emphasis has evolved away from confirmation of the mere presence of gas hydrate to the more complex issue of prospecting for those specific accumulations that are viable resource targets. Gas hydrate exploration now integrates the unique pressure and temperature preconditions for gas hydrate occurrence with those concepts and practices that are the basis for conventional oil and gas exploration. We have aimed to assimilate the lessons learned to date in global gas hydrate exploration to outline a generalized prospecting approach as follows: (1) use existing well and geophysical data to delineate the gas hydrate stability zone (GHSZ), (2) identify and evaluate potential direct indications of hydrate occurrence through evaluation of interval of elevated acoustic velocity and/or seismic events of prospective amplitude and polarity, (3) mitigate geologic risk via regional seismic and stratigraphic facies analysis as well as seismic mapping of amplitude distribution along prospective horizons, and (4) mitigate further prospect risk through assessment of the evidence of gas presence and migration into the GHSZ. Although a wide range of occurrence types might ultimately become viable energy supply options, this approach, which has been tested in only a small number of locations worldwide, has directed prospect evaluation toward those sand-hosted, high-saturation occurrences that were presently considered to have the greatest future commercial potential.

  11. Gas Hydrates Research Programs: An International Review

    Energy Technology Data Exchange (ETDEWEB)

    Jorge Gabitto; Maria Barrufet

    2009-12-09

    Gas hydrates sediments have the potential of providing a huge amount of natural gas for human use. Hydrate sediments have been found in many different regions where the required temperature and pressure conditions have been satisfied. Resource exploitation is related to the safe dissociation of the gas hydrate sediments. Basic depressurization techniques and thermal stimulation processes have been tried in pilot efforts to exploit the resource. There is a growing interest in gas hydrates all over the world due to the inevitable decline of oil and gas reserves. Many different countries are interested in this valuable resource. Unsurprisingly, developed countries with limited energy resources have taken the lead in worldwide gas hydrates research and exploration. The goal of this research project is to collect information in order to record and evaluate the relative strengths and goals of the different gas hydrates programs throughout the world. A thorough literature search about gas hydrates research activities has been conducted. The main participants in the research effort have been identified and summaries of their past and present activities reported. An evaluation section discussing present and future research activities has also been included.

  12. Gas hydrate dissociation structures in submarine slopes

    Energy Technology Data Exchange (ETDEWEB)

    Gidley, I.; Grozic, J.L.H. [Calgary Univ., AB (Canada). Dept. of Civil Engineering

    2008-07-01

    Studies have suggested that gas hydrates may play a role in submarine slope failures. However, the mechanics surrounding such failures are poorly understood. This paper discussed experimental tests conducted on a small-scale physical model of submarine soils with hydrate inclusions. The laboratory tests investigated the effects of slope angle and depth of burial of the hydrate on gas escape structures and slope stability. Laponite was used to model the soils due to its ability to swell and produce a clear, colorless thixotropic gel when dispersed in water. An R-11 refrigerant was used to form hydrate layers and nodules. The aim of the experiment was to investigate the path of the fluid escape structures and the development of a subsequent slip plane caused by the dissociation of the R-11 hydrates. Slope angles of 5, 10, and 15 degrees were examined. Slopes were examined using high-resolution, high-speed imaging techniques. Hydrate placement and slope inclinations were varied in order to obtain stability data. Results of the study showed that slope angle influenced the direction of travel of the escaping gas, and that the depth of burial affected sensitivity to slope angle. Theoretical models developed from the experimental data have accurately mapped deformations and stress states during testing. Further research is being conducted to investigate the influence of the size, shape, and placement of the hydrates. 30 refs., 15 figs.

  13. Thin films of soft matter

    CERN Document Server

    Kalliadasis, Serafim

    2007-01-01

    A detailed overview and comprehensive analysis of the main theoretical and experimental advances on free surface thin film and jet flows of soft matter is given. At the theoretical front the book outlines the basic equations and boundary conditions and the derivation of low-dimensional models for the evolution of the free surface. Such models include long-wave expansions and equations of the boundary layer type and are analyzed via linear stability analysis, weakly nonlinear theories and strongly nonlinear analysis including construction of stationary periodic and solitary wave and similarity solutions. At the experimental front a variety of very recent experimental developments is outlined and the link between theory and experiments is illustrated. Such experiments include spreading drops and bubbles, imbibitions, singularity formation at interfaces and experimental characterization of thin films using atomic force microscopy, ellipsometry and contact angle measurements and analysis of patterns using Minkows...

  14. Chemotherapy for Soft Tissue Sarcomas

    Science.gov (United States)

    ... Stage Soft Tissue Sarcoma Treating Soft Tissue Sarcomas Chemotherapy for Soft Tissue Sarcomas Chemotherapy (chemo) is the use of drugs given into ... Depending on the type and stage of sarcoma, chemotherapy may be given as the main treatment or ...

  15. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Thomas E. Williams; Keith Millheim; Buddy King

    2004-03-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the second year of a three-year endeavor being sponsored by Maurer Technology, Noble, and Anadarko Petroleum, in partnership with the DOE. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition. We plan to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. We also plan to design and implement a program to safely and economically drill, core and produce gas from arctic hydrates. The current work scope is to drill and core a well on Anadarko leases in FY 2003 and 2004. We are also using an on-site core analysis laboratory to determine some of the physical characteristics of the hydrates and surrounding rock. The well is being drilled from a new Anadarko Arctic Platform that will have minimal footprint and environmental impact. We hope to correlate geology, geophysics, logs, and drilling and production data to allow reservoir models to be calibrated. Ultimately, our goal is to form an objective technical and economic evaluation of reservoir potential in Alaska.

  16. Methane hydrate stability and anthropogenic climate change

    Directory of Open Access Journals (Sweden)

    D. Archer

    2007-07-01

    Full Text Available Methane frozen into hydrate makes up a large reservoir of potentially volatile carbon below the sea floor and associated with permafrost soils. This reservoir intuitively seems precarious, because hydrate ice floats in water, and melts at Earth surface conditions. The hydrate reservoir is so large that if 10% of the methane were released to the atmosphere within a few years, it would have an impact on the Earth's radiation budget equivalent to a factor of 10 increase in atmospheric CO2.

    Hydrates are releasing methane to the atmosphere today in response to anthropogenic warming, for example along the Arctic coastline of Siberia. However most of the hydrates are located at depths in soils and ocean sediments where anthropogenic warming and any possible methane release will take place over time scales of millennia. Individual catastrophic releases like landslides and pockmark explosions are too small to reach a sizable fraction of the hydrates. The carbon isotopic excursion at the end of the Paleocene has been interpreted as the release of thousands of Gton C, possibly from hydrates, but the time scale of the release appears to have been thousands of years, chronic rather than catastrophic.

    The potential climate impact in the coming century from hydrate methane release is speculative but could be comparable to climate feedbacks from the terrestrial biosphere and from peat, significant but not catastrophic. On geologic timescales, it is conceivable that hydrates could release as much carbon to the atmosphere/ocean system as we do by fossil fuel combustion.

  17. Methane hydrate stability and anthropogenic climate change

    Directory of Open Access Journals (Sweden)

    D. Archer

    2007-04-01

    Full Text Available Methane frozen into hydrate makes up a large reservoir of potentially volatile carbon below the sea floor and associated with permafrost soils. This reservoir intuitively seems precarious, because hydrate ice floats in water, and melts at Earth surface conditions. The hydrate reservoir is so large that if 10% of the methane were released to the atmosphere within a few years, it would have an impact on the Earth's radiation budget equivalent to a factor of 10 increase in atmospheric CO2.

    Hydrates are releasing methane to the atmosphere today in response to anthropogenic warming, for example along the Arctic coastline of Siberia. However most of the hydrates are located at depths in soils and ocean sediments where anthropogenic warming and any possible methane release will take place over time scales of millennia. Individual catastrophic releases like landslides and pockmark explosions are too small to reach a sizable fraction of the hydrates. The carbon isotopic excursion at the end of the Paleocene has been interpreted as the release of thousands of Gton C, possibly from hydrates, but the time scale of the release appears to have been thousands of years, chronic rather than catastrophic.

    The potential climate impact in the coming century from hydrate methane release is speculative but could be comparable to climate feedbacks from the terrestrial biosphere and from peat, significant but not catastrophic. On geologic timescales, it is conceivable that hydrates could release much carbon to the atmosphere/ocean system as we do by fossil fuel combustion.

  18. Molecular dynamics simulations of methane hydrate pre-nucleation phenomena and the effect of PVCap kinetic inhibitor

    Science.gov (United States)

    Kuznetsova, Tatiana; Kvamme, Bjørn; Parmar, Archana

    2012-12-01

    MD simulations were employed to investigate a number of different systems of relevance for methane hydrate formation, dissociation and inhibition. Regions of stability for methane hydrate have been investigated using a model system consisting of a slab of hydrate embedded in liquid water. Water/methane interface structuring and possible precursors to hydrate formation have been investigated using a model system of water and methane at different densities. In yet another system we have investigated the impact of Dodecamers (twelve-unit molecules) of poly (vinyl caprolactam) or PVCap on structuring of water/methane interfaces. PVCap is well known for its performance as hydrate kinetic inhibitor1. Intermolecular interactions were treated by a combination of Coulomb and Lennard-Jones potentials. Temperature was controlled by a simple velocity scaling. Several of the hydrate-containing systems showed a tendency to melt when in contact with methane-saturated water even at temperatures well below the hydrate stability region. We have attributed this behavior to the fact that hydrate volume available in a MD experiment is small and lacks the stabilizing presence of bulk. Systems containing liquid water and methane showed certain signs of hydrate nucleation. The PVCap behavior was shown to be very dependent on its concentration in water. At low concentrations, PVCap tended to prefer the water-methane interface and not to interact with each other, similarly to another kinetic inhibitor, PVP2. When the liquid PVCap content was high, it evidently modified the interfacial tension of water-methane surface, converting the initially disperesed methane phase into separated bubbles. The PVCap molecules then built a system-wide network that partially covered the surface of methane bubbles.

  19. The influence of pipeline wettability and crude oil composition on deposition of gas hydrates during petroleum production

    Energy Technology Data Exchange (ETDEWEB)

    Aspenes, Guro

    2009-07-01

    At specific temperature and pressure conditions, hydrates can sometimes plug production pipelines. It has been shown that some oils contain natural inhibiting compounds (NICs) that prevent hydrate plug formation even though the pressure and temperature are within the hydrate formation conditions. Thus, the hydrate plugging tendency is influenced by the crude oil composition. The mechanisms by which deposition of hydrates occur in a petroleum production system are also likely to be related to pipeline surface properties, e.g. pipeline material, surface free energy and roughness. The ultimate aim of this work is to develop an understanding of the deposition of hydrates on the pipeline wall. Most of the work in this thesis deals with contact angle measurements that determine the wettability of various solids. Different materials and oil compositions have been tested including both model oil systems and crude oil systems. Micromechanical force experiments have been used to determine the adhesion force between hydrates and solids with different amounts of petroleum acids present in the oil phase. The factors that have been identified in this work as most likely influencing deposition of hydrates to the pipeline wall are the presence of free water, surface material and crude oil composition. It may seem as if hydrate deposition will not occur unless free water is present. When the pipeline wall material has a low surface free energy, such as epoxy coated surfaces, deposition seems to be reduced. Crude oils that are assumed as non-plugging and contain high concentrations of acids seems to reduce the probability for deposition to occur. (Author)

  20. Puncture mechanics of soft solids.

    Science.gov (United States)

    Fakhouri, Sami; Hutchens, Shelby B; Crosby, Alfred J

    2015-06-21

    Gels and other soft elastic networks are a ubiquitous and important class of materials whose unique properties enable special behavior, but generally elude characterization due to the inherent difficulty in manipulating them. An example of such behavior is the stability of gels to large local deformations on their surface. This paper analyzes puncture of model soft materials with particular focus on the force response to deep indentation and the critical load for material failure. Large-strain behavior during deep indentation is described with a neo-hookean contact model. A fracture process zone model is applied to the critical load for puncture. It is found that the indenter geometry influences the size of the fracture process zone, resulting in two distinct failure regimes: stress-limited and energy-limited. The methods outlined in this paper provide a simple means for measuring Young's modulus, E, as well as the material's maximum cohesive stress, σ0, fracture energy, Γ0, and the intrinsic length scale linking the two, l0, all without requiring specialized sample preparation.

  1. Proton percolation on hydrated lysozyme powders

    OpenAIRE

    Careri, G; Giansanti, A; Rupley, John A.

    1986-01-01

    The framework of percolation theory is used to analyze the hydration dependence of the capacitance measured for protein samples of pH 3-10, at frequencies from 10 kHz to 4 MHz. For all samples there is a critical value of the hydration at which the capacitance sharply increases with increase in hydration level. The threshold hc = 0.15 g of water per g of protein is independent of pH below pH 9 and shows no solvent deuterium isotope effect. The fractional coverage of the surface at hc is in cl...

  2. Coarse-grained model of water diffusion and proton conductivity in hydrated polyelectrolyte membrane

    Science.gov (United States)

    Lee, Ming-Tsung; Vishnyakov, Aleksey; Neimark, Alexander V.

    2016-01-01

    Using dissipative particle dynamics (DPD), we simulate nanoscale segregation, water diffusion, and proton conductivity in hydrated sulfonated polystyrene (sPS). We employ a novel model [Lee et al. J. Chem. Theory Comput. 11(9), 4395-4403 (2015)] that incorporates protonation/deprotonation equilibria into DPD simulations. The polymer and water are modeled by coarse-grained beads interacting via short-range soft repulsion and smeared charge electrostatic potentials. The proton is introduced as a separate charged bead that forms dissociable Morse bonds with the base beads representing water and sulfonate anions. Morse bond formation and breakup artificially mimics the Grotthuss mechanism of proton hopping between the bases. The DPD model is parameterized by matching the proton mobility in bulk water, dissociation constant of benzenesulfonic acid, and liquid-liquid equilibrium of water-ethylbenzene solutions. The DPD simulations semi-quantitatively predict nanoscale segregation in the hydrated sPS into hydrophobic and hydrophilic subphases, water self-diffusion, and proton mobility. As the hydration level increases, the hydrophilic subphase exhibits a percolation transition from isolated water clusters to a 3D network. The analysis of hydrophilic subphase connectivity and water diffusion demonstrates the importance of the dynamic percolation effect of formation and breakup of temporary junctions between water clusters. The proposed DPD model qualitatively predicts the ratio of proton to water self-diffusion and its dependence on the hydration level that is in reasonable agreement with experiments.

  3. Coarse-grained model of water diffusion and proton conductivity in hydrated polyelectrolyte membrane

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ming-Tsung; Vishnyakov, Aleksey; Neimark, Alexander V., E-mail: aneimark@rutgers.edu [Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854-8058 (United States)

    2016-01-07

    Using dissipative particle dynamics (DPD), we simulate nanoscale segregation, water diffusion, and proton conductivity in hydrated sulfonated polystyrene (sPS). We employ a novel model [Lee et al. J. Chem. Theory Comput. 11(9), 4395-4403 (2015)] that incorporates protonation/deprotonation equilibria into DPD simulations. The polymer and water are modeled by coarse-grained beads interacting via short-range soft repulsion and smeared charge electrostatic potentials. The proton is introduced as a separate charged bead that forms dissociable Morse bonds with the base beads representing water and sulfonate anions. Morse bond formation and breakup artificially mimics the Grotthuss mechanism of proton hopping between the bases. The DPD model is parameterized by matching the proton mobility in bulk water, dissociation constant of benzenesulfonic acid, and liquid-liquid equilibrium of water-ethylbenzene solutions. The DPD simulations semi-quantitatively predict nanoscale segregation in the hydrated sPS into hydrophobic and hydrophilic subphases, water self-diffusion, and proton mobility. As the hydration level increases, the hydrophilic subphase exhibits a percolation transition from isolated water clusters to a 3D network. The analysis of hydrophilic subphase connectivity and water diffusion demonstrates the importance of the dynamic percolation effect of formation and breakup of temporary junctions between water clusters. The proposed DPD model qualitatively predicts the ratio of proton to water self-diffusion and its dependence on the hydration level that is in reasonable agreement with experiments.

  4. Glass powder blended cement hydration modelling

    Science.gov (United States)

    Saeed, Huda

    The use of waste materials in construction is among the most attractive options to consume these materials without affecting the environment. Glass is among these types of potential waste materials. In this research, waste glass in powder form, i.e. glass powder (GP) is examined for potential use in enhancing the characteristics of concrete on the basis that it is a pozzolanic material. The experimental and the theoretical components of the work are carried out primarily to prove that glass powder belongs to the "family" of the pozzolanic materials. The chemical and physical properties of the hydrated activated glass powder and the hydrated glass powder cement on the microstructure level have been studied experimentally and theoretically. The work presented in this thesis consists of two main phases. The first phase contains experimental investigations of the reaction of glass powder with calcium hydroxide (CH) and water. In addition, it includes experiments that are aimed at determining the consumption of water and CH with time. The reactivity, degree of hydration, and nature of the pore solution of the glass powder-blended cement pastes and the effect of adding different ratios of glass powder on cement hydration is also investigated. The experiments proved that glass powder has a pozzolanic effect on cement hydration; hence it enhances the chemical and physical properties of cement paste. Based on the experimental test results, it is recommended to use a glass powder-to-cement ratio (GP/C) of 10% as an optimum ratio to achieve the best hydration and best properties of the paste. Two different chemical formulas for the produced GP C-S-H gel due to the pure GP and GP-CH pozzolanic reaction hydration are proposed. For the pure GP hydration, the produced GP C-S-H gel has a calcium-to-silica ratio (C/S) of 0.164, water-to-silica ratio (H/S) of 1.3 and sodium/silica ratio (N/S) of 0.18. However, for the GP-CH hydration, the produced GP C-S-H gel has a C/S ratio of 1

  5. Distinct Roles for Interfacial Hydration in Site-Specific DNA Recognition by ETS-Family Transcription Factors.

    Science.gov (United States)

    Xhani, Suela; Esaki, Shingo; Huang, Kenneth; Erlitzki, Noa; Poon, Gregory M K

    2017-04-06

    The ETS family of transcription factors is a functionally heterogeneous group of gene regulators that share a structurally conserved, eponymous DNA-binding domain. Unlike other ETS homologues, such as Ets-1, DNA recognition by PU.1 is highly sensitive to its osmotic environment due to excess interfacial hydration in the complex. To investigate interfacial hydration in the two homologues, we mutated a conserved tyrosine residue, which is exclusively engaged in coordinating a well-defined water contact between the protein and DNA among ETS proteins, to phenylalanine. The loss of this water-mediated contact blunted the osmotic sensitivity of PU.1/DNA binding, but did not alter binding under normo-osmotic conditions, suggesting that PU.1 has evolved to maximize osmotic sensitivity. The homologous mutation in Ets-1, which was minimally sensitive to osmotic stress due to a sparsely hydrated interface, reduced DNA-binding affinity at normal osmolality but the complex became stabilized by osmotic stress. Molecular dynamics simulations of wildtype and mutant PU.1 and Ets-1 in their free and DNA-bound states, which recapitulated experimental features of the proteins, showed that abrogation of this tyrosine-mediated water contact perturbed the Ets-1/DNA complex not through disruption of interfacial hydration, but by inhibiting local dynamics induced specifically in the bound state. Thus, a configurationally identical water-mediated contact plays mechanistically distinct roles in mediating DNA recognition by structurally homologous ETS transcription factors.

  6. Effect of Some Admixtures on the Hydration of Silica Fume and Hydrated Lime

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The effects of sodium salt of naphthalene formaldehyde sulfonic acid and stearic acid on the hydration of silica fume and Ca(0H)2 have been investigated. The hydration was carried out at 60℃ and W/S ratio of 4 for various time intervals namely, 1, 3, 7 and 28 days and in the presence of 0.2% and 5% superplasticizer and stearic acid. The results of the hydration kinetics show that both admixtures accelerate the hydration reaction of silica fume and calcium hydroxide during the first 7 days. Whereas, after 28 days hydration there is no significant effect. Generally, most of free calcium hydroxide seems to be consumed after 28 days. In addition, the phase composition as well as the microstructure of the formed hydrates was examined by using X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) respectively.

  7. Impact of hydration on the micromechanical properties of the polymer composite structure of wood investigated with atomistic simulations

    Science.gov (United States)

    Kulasinski, Karol; Derome, Dominique; Carmeliet, Jan

    2017-06-01

    A model of the secondary layer of wood cell wall consisting of crystalline cellulose, hemicellulose, and lignin is constructed and investigated with molecular dynamics simulations in the full range of hydration: from dry to saturated state. The model is considered a composite with the cellulose fibrils embedded in hemicellulose and lignin, forming a soft amorphous matrix. Its complex structure leads to nonlinear and anisotropic swelling and mechanical weakening. The water diffusivity through the pores is affected by an interplay between stiff cellulose fibers and weakening amorphous polymers. The formation and breaking of hydrogen bonds within the polymers and at the interfaces is found to be the underlying mechanism of adsorption-induced mechanical softening. The model is tested for adsorption isotherm, mechanical moduli, hydrogen bonds, and water diffusivity that all undergo a substantial change as the hydration increases. The determined physical and mechanical properties, changing with hydration, agree qualitatively with experimental measurements.

  8. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Vision and Daily Eye Drops After One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume Contacts May Contain Chemicals ...

  9. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume ... use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses ...

  10. Potentially pathogenic free-living amoebae in contact lenses of the asymptomatic contact lens wearers.

    Directory of Open Access Journals (Sweden)

    Maryam Niyyati

    2014-03-01

    Full Text Available Free-living amoebae (FLA including Acanthamoeba spp. and Hartmannella spp. are the causative agents of serious corneal infection especially within contact lens wearers. Thus contact lenses and their storage case could be a suitable niche for potentially pathogenic amoebae. The main objective of the present study was to evaluate the contamination of contact lenses to free living amoebae using morphological and sequencing based methods.Overall, 90 volunteers provided their contact lenses. All volunteers wore soft contact lenses. Both lenses were cultured in the same plate. Forty-eight of the volunteers were medical and dentistry student and 42 were ophthalmology attendees of hospitals in Tehran, Iran. All of the samples were inoculated to non-nutrient medium and monitored daily for the outgrowth of the amoebae. PCR and sequencing were performed using various primer pairs.Of the 90 volunteers, 9 (10% were positive for free-living amoebae outgrowth. Morphological analysis revealed that 3 isolates were belonged to Hartmannella genus according to small round cysts and 6 isolates were belonged to Acanthamoeba genus based on the star shape of endocysts. Sequencing revealed that Acanthamoeba belonged to T4, T3 and T5 genotype. Hartmannella were also belonged to vermiformis species.The presence of potentially pathogenic free living amoebae including Acanthamoeba and Hartmannella could be a high risk for people using soft contact lenses. These results revealed that improved clarification and professional recommendations for contact lens wearers is of utmost importance.

  11. Contact Lens Visual Rehabilitation in Keratoconus and Corneal Keratoplasty

    Directory of Open Access Journals (Sweden)

    Yelda Ozkurt

    2012-01-01

    Full Text Available Keratoconus is the most common corneal distrophy. It’s a noninflammatory progressive thinning process that leads to conical ectasia of the cornea, causing high myopia and astigmatism. Many treatment choices include spectacle correction and contact lens wear, collagen cross linking, intracorneal ring segments implantation and finally keratoplasty. Contact lenses are commonly used to reduce astigmatism and increase vision. There are various types of lenses are available. We reviewed soft contact lenses, rigid gas permeable contact lenses, piggyback contact lenses, hybrid contact lenses and scleral-semiscleral contact lenses in keratoconus management. The surgical option is keratoplasty, but even after sutur removal, high astigmatism may stil exists. Therefore, contact lens is an adequate treatment option to correct astigmatism after keratoplasty.

  12. Three-dimensional distribution of gas hydrate beneath southern Hydrate Ridge: Constraints from ODP Leg 204

    Science.gov (United States)

    Trehu, A.M.; Long, P.E.; Torres, M.E.; Bohrmann, G.; Rack, F.R.; Collett, T.S.; Goldberg, D.S.; Milkov, A.V.; Riedel, M.; Schultheiss, P.; Bangs, N.L.; Barr, S.R.; Borowski, W.S.; Claypool, G.E.; Delwiche, M.E.; Dickens, G.R.; Gracia, E.; Guerin, G.; Holland, M.; Johnson, J.E.; Lee, Y.-J.; Liu, C.-S.; Su, X.; Teichert, B.; Tomaru, H.; Vanneste, M.; Watanabe, M. E.; Weinberger, J.L.

    2004-01-01

    Large uncertainties about the energy resource potential and role in global climate change of gas hydrates result from uncertainty about how much hydrate is contained in marine sediments. During Leg 204 of the Ocean Drilling Program (ODP) to the accretionary complex of the Cascadia subduction zone, we sampled the gas hydrate stability zone (GHSZ) from the seafloor to its base in contrasting geological settings defined by a 3D seismic survey. By integrating results from different methods, including several new techniques developed for Leg 204, we overcome the problem of spatial under-sampling inherent in robust methods traditionally used for estimating the hydrate content of cores and obtain a high-resolution, quantitative estimate of the total amount and spatial variability of gas hydrate in this structural system. We conclude that high gas hydrate content (30-40% of pore space or 20-26% of total volume) is restricted to the upper tens of meters below the seafloor near the summit of the structure, where vigorous fluid venting occurs. Elsewhere, the average gas hydrate content of the sediments in the gas hydrate stability zone is generally <2% of the pore space, although this estimate may increase by a factor of 2 when patchy zones of locally higher gas hydrate content are included in the calculation. These patchy zones are structurally and stratigraphically controlled, contain up to 20% hydrate in the pore space when averaged over zones ???10 m thick, and may occur in up to ???20% of the region imaged by 3D seismic data. This heterogeneous gas hydrate distribution is an important constraint on models of gas hydrate formation in marine sediments and the response of the sediments to tectonic and environmental change. ?? 2004 Published by Elsevier B.V.

  13. Experimental Investigation of Effect on Hydrate Formation in Spray Reactor

    Directory of Open Access Journals (Sweden)

    Jianzhong Zhao

    2015-01-01

    Full Text Available The effects of reaction condition on hydrate formation were conducted in spray reactor. The temperature, pressure, and gas volume of reaction on hydrate formation were measured in pure water and SDS solutions at different temperature and pressure with a high-pressure experimental rig for hydrate formation. The experimental data and result reveal that additives could improve the hydrate formation rate and gas storage capacity. Temperature and pressure can restrict the hydrate formation. Lower temperature and higher pressure can promote hydrate formation, but they can increase production cost. So these factors should be considered synthetically. The investigation will promote the advance of gas storage technology in hydrates.

  14. Evaluating six soft approaches

    DEFF Research Database (Denmark)

    Sørensen, Lene Tolstrup; Vidal, Rene Victor Valqui

    2008-01-01

    's interactive planning principles to be supported by soft approaches in carrying out the principles in action. These six soft approaches are suitable forsupporting various steps of the strategy development and planning process. These are the SWOT analysis, the Future Workshop, the Scenario methodology......, Strategic Option Development and Analysis, Strategic Choice Approach and Soft Systems Methodology. Evaluations of each methodology are carried out using a conceptual framework in which the organisation, the result, the process and the technology of the specific approach are taken into consideration. Using...

  15. Evaluating Six Soft Approaches

    DEFF Research Database (Denmark)

    Sørensen, Lene Tolstrup; Valqui Vidal, René Victor

    2008-01-01

    's interactive planning principles to be supported by soft approaches in carrying out the principles in action. These six soft approaches are suitable forsupporting various steps of the strategy development and planning process. These are the SWOT analysis, the Future Workshop, the Scenario methodology......, Strategic Option Development and Analysis, Strategic Choice Approach and Soft Systems Methodology. Evaluations of each methodology are carried out using a conceptual framework in which the organisation, the result, the process and the technology of the specific approach are taken into consideration. Using...

  16. Evaluating six soft approaches

    DEFF Research Database (Denmark)

    Sørensen, Lene Tolstrup; Vidal, Rene Victor Valqui

    2008-01-01

    's interactive planning principles to be supported by soft approaches in carrying out the principles in action. These six soft approaches are suitable forsupporting various steps of the strategy development and planning process. These are the SWOT analysis, the Future Workshop, the Scenario methodology......, Strategic Option Development and Analysis, Strategic Choice Approach and Soft Systems Methodology. Evaluations of each methodology are carried out using a conceptual framework in which the organisation, the result, the process and the technology of the specific approach are taken into consideration. Using...

  17. A Hydrate Database: Vital to the Technical Community

    Directory of Open Access Journals (Sweden)

    D Sloan

    2007-06-01

    Full Text Available Natural gas hydrates may contain more energy than all the combined other fossil fuels, causing hydrates to be a potentially vital aspect of both energy and climate change. This article is an overview of the motivation, history, and future of hydrate data management using a CODATA vehicle to connect international hydrate databases. The basis is an introduction to the Gas Hydrate Markup Language (GHML to connect various hydrate databases. The accompanying four articles on laboratory hydrate data by Smith et al., on field hydrate data by L?wner et al., on hydrate modeling by Wang et al., and on construction of a Chinese gas hydrate system by Xiao et al. provide details of GHML in their respective areas.

  18. Composite inorganic membranes containing nanoparticles of hydrated zirconium dioxide for electrodialytic separation

    OpenAIRE

    Dzyazko, Yuliya S; Volfkovich, Yurii M; Sosenkin, Valentin E; Nikolskaya, Nadejda F; Gomza, Yurii P

    2014-01-01

    The aim of the work was to elucidate the nature of charge-selective properties of macroporous composite inorganic membranes modified with nanoparticles of hydrated zirconium dioxide. The membranes have been investigated using methods of standard contact porosimetry, potentiometry, electron microscopy and small-angle X-ray scattering. The ion exchanger has been found to deposit inside pores of ceramics. Differential curves of pore volume distribution have been resolved using Lorentz functions;...

  19. Vibrational dynamics of hydration water in amylose

    CERN Document Server

    Cavatorta, F; Albanese, G; Angelini, N

    2002-01-01

    We present a study of the dynamical properties of hydration water associated with amylose helices, based on low-temperature vibrational spectra collected using the TOSCA inelastic spectrometer at ISIS. The structural constraints of the polysaccharidic chains favour the formation of a high-density structure for water, which has been suggested by Imberty and Perez on the basis of conformational analysis. According to this model, hydration water can only enter the pores formed by six adjacent helices and completely fills the pores at a hydration level of about 0.27-g water/g dry amylose. Our measurements show that the dynamical behaviour of hydration water is similar to that observed in high-density amorphous ice. (orig.)

  20. ConocoPhillips Gas Hydrate Production Test

    Energy Technology Data Exchange (ETDEWEB)

    Schoderbek, David; Farrell, Helen; Howard, James; Raterman, Kevin; Silpngarmlert, Suntichai; Martin, Kenneth; Smith, Bruce; Klein, Perry

    2013-06-30

    Work began on the ConocoPhillips Gas Hydrates Production Test (DOE award number DE-NT0006553) on October 1, 2008. This final report summarizes the entire project from January 1, 2011 to June 30, 2013.

  1. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Donn McGuire; Thomas Williams; Bjorn Paulsson; Alexander Goertz

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a drilling hazard by the oil and gas industry for years. Drilling engineers working in Russia, Canada and the USA have documented numerous problems, including drilling kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrates as a potential energy source agree that the resource potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained from physical samples taken from actual hydrate-bearing rocks. This gas-hydrate project is a cost-shared partnership between Maurer Technology, Anadarko Petroleum, Noble Corporation, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. The project team drilled and continuously cored the Hot Ice No. 1 well on Anadarko-leased acreage beginning in FY 2003 and completed in 2004. An on-site core analysis laboratory was built and used for determining physical characteristics of hydrates and surrounding rock. After the well was logged, a 3D vertical seismic profile (VSP) was recorded to calibrate the shallow geologic section with seismic data and to investigate techniques to better resolve lateral subsurface variations of potential hydrate-bearing strata. Paulsson Geophysical Services, Inc. deployed their 80 level 3C clamped borehole seismic receiver array in the wellbore to record samples every 25 ft. Seismic vibrators were successively positioned at 1185 different surface positions in a circular pattern around the wellbore. This technique generated a 3D image of the subsurface. Correlations were

  2. Hydration states of AFm cement phases

    Energy Technology Data Exchange (ETDEWEB)

    Baquerizo, Luis G., E-mail: luis.baquerizoibarra@holcim.com [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Matschei, Thomas [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Scrivener, Karen L. [Laboratory of Construction Materials, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Saeidpour, Mahsa; Wadsö, Lars [Building Materials, Lund University, Box 124, 221 000 Lund (Sweden)

    2015-07-15

    The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively charged layers and water plus charge-balancing anions in the interlayer. It is known that these phases present different hydration states (i.e. varying water content) depending on the relative humidity (RH), temperature and anion type, which might be linked to volume changes (swelling and shrinkage). Unfortunately the stability conditions of these phases are insufficiently reported. This paper presents novel experimental results on the different hydration states of the most important AFm phases: monocarboaluminate, hemicarboaluminate, strätlingite, hydroxy-AFm and monosulfoaluminate, and the thermodynamic properties associated with changes in their water content during absorption/desorption. This data opens the possibility to model the response of cementitious systems during drying and wetting and to engineer systems more resistant to harsh external conditions.

  3. Polyethylene oxide hydration in grafted layers

    Science.gov (United States)

    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).

  4. Formulating formation mechanism of natural gas hydrates.

    Science.gov (United States)

    Palodkar, Avinash V; Jana, Amiya K

    2017-07-25

    A large amount of energy, perhaps twice the total amount of all other hydrocarbon reserves combined, is trapped within gas hydrate deposits. Despite emerging as a potential energy source for the world over the next several hundred years and one of the key factors in causing future climate change, gas hydrate is poorly known in terms of its formation mechanism. To address this issue, a mathematical formulation is proposed in the form of a model to represent the physical insight into the process of hydrate growth that occurs on the surface and in the irregular nanometer-sized pores of the distributed porous particles. To evaluate the versatility of this rigorous model, the experimental data is used for methane (CH4) and carbon dioxide (CO2) hydrates grown in different porous media with a wide range of considerations.

  5. Hydrate Control for Gas Storage Operations

    Energy Technology Data Exchange (ETDEWEB)

    Jeffrey Savidge

    2008-10-31

    The overall objective of this project was to identify low cost hydrate control options to help mitigate and solve hydrate problems that occur in moderate and high pressure natural gas storage field operations. The study includes data on a number of flow configurations, fluids and control options that are common in natural gas storage field flow lines. The final phase of this work brings together data and experience from the hydrate flow test facility and multiple field and operator sources. It includes a compilation of basic information on operating conditions as well as candidate field separation options. Lastly the work is integrated with the work with the initial work to provide a comprehensive view of gas storage field hydrate control for field operations and storage field personnel.

  6. Quantifying hydrate formation and kinetic inhibition

    Energy Technology Data Exchange (ETDEWEB)

    Sloan, E.D.; Subramanian, S.; Matthews, P.N.; Lederhos, J.P.; Khokhar, A.A. [Colorado School of Mines, Golden, CO (United States). Center for Hydrate Research

    1998-08-01

    In the Prausnitz tradition, molecular and macroscopic evidence of hydrate formation and kinetic inhibition is presented. On the microscopic level, the first Raman spectra are presented for the formation of both uninhibited and inhibited methane hydrates with time. This method has the potential to provide a microscopic-based kinetics model. Three macroscopic aspects of natural gas hydrate kinetic inhibition are also reported: (1) The effect of hydrate dissociation residual structures was measured, which has application in decreasing the time required for subsequent formation. (2) The performance of a kinetic inhibitor (poly(N-vinylcaprolactam) or PVCap) was measured and correlated as a function of PVCap molecular weight and concentrations of PVCap, methanol, and salt in the aqueous phase. (3) Long-duration test results indicated that the use of PVCap can prevent pipeline blockage for a time exceeding the aqueous phase residence time in some gas pipelines.

  7. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Ali Kadaster; Bill Liddell; Tommy Thompson; Thomas Williams; Michael Niedermayr

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project was a cost-shared partnership between Maurer Technology, Noble Corporation, Anadarko Petroleum, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. The work scope included drilling and coring a well (Hot Ice No. 1) on Anadarko leases beginning in FY 2003 and completed in 2004. During the first drilling season, operations were conducted at the site between January 28, 2003 to April 30, 2003. The well was spudded and drilled to a depth of 1403 ft. Due to the onset of warmer weather, work was then suspended for the season. Operations at the site were continued after the tundra was re-opened the following season. Between January 12, 2004 and March 19, 2004, the well was drilled and cored to a final depth of 2300 ft. An on-site core analysis laboratory was built and implemented for determining physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. Final efforts of the project are to correlate geology, geophysics, logs, and drilling and

  8. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Thomas E. Williams; Keith Millheim; Bill Liddell

    2004-11-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is a cost-shared partnership between Maurer Technology, Anadarko Petroleum, Noble Corporation, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to help identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. As part of the project work scope, team members drilled and cored a well (the Hot Ice No. 1) on Anadarko leases beginning in January 2003 and completed in March 2004. Due to scheduling constraints imposed by the Arctic drilling season, operations at the site were suspended between April 21, 2003 and January 30, 2004. An on-site core analysis laboratory was constructed and used for determining physical characteristics of frozen core immediately after it was retrieved from the well. The well was drilled from a new and innovative Anadarko Arctic Platform that has a greatly reduced footprint and environmental impact. Final efforts of the project were to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists for future hydrate operations. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained

  9. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Thomas E. Williams; Keith Millheim; Bill Liddell

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is a cost-shared partnership between Maurer Technology, Anadarko Petroleum, Noble Corporation, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to help identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. As part of the project work scope, team members drilled and cored a well (the Hot Ice No. 1) on Anadarko leases beginning in January 2003 and completed in March 2004. Due to scheduling constraints imposed by the Arctic drilling season, operations at the site were suspended between April 21, 2003 and January 30, 2004. An on-site core analysis laboratory was constructed and used for determining physical characteristics of frozen core immediately after it was retrieved from the well. The well was drilled from a new and innovative Anadarko Arctic Platform that has a greatly reduced footprint and environmental impact. Final efforts of the project were to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists for future hydrate operations. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained

  10. Experimental Dissociation of Methane Hydrates Through Depressurization

    Science.gov (United States)

    Borgfeldt, T.; Flemings, P. B.; Meyer, D.; You, K.

    2015-12-01

    We dissociated methane hydrates by stepwise depressurization. The initial hydrates were formed by injecting gas into a cylindrical sample of brine-saturated, coarse-grained sand at hydrate-stable conditions with the intention of reaching three-phase equilibrium. The sample was initially at 1°C with a pore pressure of 1775 psi and a salinity of 7 wt. % NaBr. The depressurization setup consisted of one pump filled with tap water attached to the confining fluid port and a second pump attached to the inlet port where the methane was injected. Depressurization was conducted over sixteen hours at a constant temperature of 1°C. The pore pressure was stepwise reduced from 1775 psi to atmospheric pressure by pulling known volumes of gas from the sample. After each extraction, we recorded the instantaneous and equilibrium pore pressure. 0.503 moles of methane were removed from the sample. The pore pressure decreased smoothly and nonlinearly with the cumulative gas withdrawn from the sample. We interpret that hydrate began to dissociate immediately with depressurization, and it continued to dissociate when the pressure decreased below the three-phase pressure for 1°C and 0 wt. % salinity. Two breaks in slope in the pressure vs. mass extracted data are bounded by smooth, nonlinear curves with differing slopes on either side. We attribute the breaks to dissociation of three zones of hydrate concentration. We created a box model to simulate the experimental behavior. For a 10% initial gas saturation (estimated from the hydrate formation experiment and based on mass conservation), an initial hydrate saturation of 55% is required to match the total methane extracted from the sample. Future experiments will be conducted over a longer timespan while monitoring hydrate dissociation with CT imaging throughout the process.

  11. Hydration of polyethylene glycol-grafted liposomes.

    OpenAIRE

    Tirosh, O; Barenholz, Y.; Katzhendler, J; Priev, A

    1998-01-01

    This study aimed to characterize the effect of polyethylene glycol of 2000 molecular weight (PEG2000) attached to a dialkylphosphatidic acid (dihexadecylphosphatidyl (DHP)-PEG2000) on the hydration and thermodynamic stability of lipid assemblies. Differential scanning calorimetry, densitometry, and ultrasound velocity and absorption measurements were used for thermodynamic and hydrational characterization. Using a differential scanning calorimetry technique we showed that each molecule of PEG...

  12. Exploitation of subsea gas hydrate reservoirs

    Science.gov (United States)

    Janicki, Georg; Schlüter, Stefan; Hennig, Torsten; Deerberg, Görge

    2016-04-01

    Natural gas hydrates are considered to be a potential energy resource in the future. They occur in permafrost areas as well as in subsea sediments and are stable at high pressure and low temperature conditions. According to estimations the amount of carbon bonded in natural gas hydrates worldwide is two times larger than in all known conventional fossil fuels. Besides technical challenges that have to be overcome climate and safety issues have to be considered before a commercial exploitation of such unconventional reservoirs. The potential of producing natural gas from subsea gas hydrate deposits by various means (e.g. depressurization and/or injection of carbon dioxide) is numerically studied in the frame of the German research project »SUGAR«. The basic mechanisms of gas hydrate formation/dissociation and heat and mass transport in porous media are considered and implemented into a numerical model. The physics of the process leads to strong non-linear couplings between hydraulic fluid flow, hydrate dissociation and formation, hydraulic properties of the sediment, partial pressures and seawater solution of components and the thermal budget of the system described by the heat equation. This paper is intended to provide an overview of the recent development regarding the production of natural gas from subsea gas hydrate reservoirs. It aims at giving a broad insight into natural gas hydrates and covering relevant aspects of the exploitation process. It is focused on the thermodynamic principles and technological approaches for the exploitation. The effects occurring during natural gas production within hydrate filled sediment layers are identified and discussed by means of numerical simulation results. The behaviour of relevant process parameters such as pressure, temperature and phase saturations is described and compared for different strategies. The simulations are complemented by calculations for different safety relevant problems.

  13. Preservation of methane hydrate at 1 atm

    Science.gov (United States)

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

    2001-01-01

    A "pressure-release" method that enables reproducible bulk preservation of pure, porous, methane hydrate at conditions 50 to 75 K above its equilibrium T (193 K) at 1 atm is refined. The amount of hydrate preserved by this method appears to be greatly in excess of that reported in the previous citations, and is likely the result of a mechanism different from ice shielding.

  14. Multigait soft robot.

    Science.gov (United States)

    Shepherd, Robert F; Ilievski, Filip; Choi, Wonjae; Morin, Stephen A; Stokes, Adam A; Mazzeo, Aaron D; Chen, Xin; Wang, Michael; Whitesides, George M

    2011-12-20

    This manuscript describes a unique class of locomotive robot: A soft robot, composed exclusively of soft materials (elastomeric polymers), which is inspired by animals (e.g., squid, starfish, worms) that do not have hard internal skeletons. Soft lithography was used to fabricate a pneumatically actuated robot capable of sophisticated locomotion (e.g., fluid movement of limbs and multiple gaits). This robot is quadrupedal; it uses no sensors, only five actuators, and a simple pneumatic valving system that operates at low pressures (< 10 psi). A combination of crawling and undulation gaits allowed this robot to navigate a difficult obstacle. This demonstration illustrates an advantage of soft robotics: They are systems in which simple types of actuation produce complex motion.

  15. Soft bioelectronics using nanomaterials

    Science.gov (United States)

    Lee, Hyunjae; Kim, Dae-Hyeong

    2016-09-01

    Recently, soft bioelectronics has attracted significant attention because of its potential applications in biointegrated healthcare devices and minimally invasive surgical tools. Mechanical mismatch between conventional electronic/optoelectronic devices and soft human tissues/organs, however, causes many challenges in materials and device designs of bio-integrated devices. Intrinsically soft hybrid materials comprising twodimensional nanomaterials are utilized to solve these issues. In this paper, we describe soft bioelectronic devices based on graphene synthesized by a chemical vapor deposition process. These devices have unique advantages over rigid electronics, particularly in biomedical applications. The functionalized graphene is hybridized with other nanomaterials and fabricated into high-performance sensors and actuators toward wearable and minimally invasive healthcare devices. Integrated bioelectronic systems constructed using these devices solve pending issues in clinical medicine while providing new opportunities in personalized healthcare.

  16. Surfactant effects on SF6 hydrate formation.

    Science.gov (United States)

    Lee, Bo Ram; Lee, Ju Dong; Lee, Hyun Ju; Ryu, Young Bok; Lee, Man Sig; Kim, Young Seok; Englezos, Peter; Kim, Myung Hyun; Kim, Yang Do

    2009-03-01

    Sulfur hexafluoride (SF(6)) has been widely used in a variety of industrial processes, but it is one of the most potent greenhouse gases. For this reason, it is necessary to separate or collect it from waste gas streams. One separation method is through hydrate crystal formation. In this study, SF(6) hydrate was formed in aqueous surfactant solutions of 0.00, 0.01, 0.05, 0.15 and 0.20 wt% to investigate the effects of surfactants on the hydrate formation rates. Three surfactants, Tween 20 (Tween), sodium dodecyl sulfate (SDS) and linear alkyl benzene sulfonate (LABS), were tested in a semi-batch stirred vessel at the constant temperature and pressures of 276.2 K and 0.78 MPa, respectively. All surfactants showed kinetic promoter behavior for SF(6) hydrate formation. It was also found that SF(6) hydrate formation proceeded in two stages with the second stage being the most rapid. In situ Raman spectroscopy analysis revealed that the increased gas consumption rate with the addition of surfactant was possibly due to the increased gas filling rate in the hydrate cavity.

  17. Deployable Soft Composite Structures

    OpenAIRE

    Wei Wang; Hugo Rodrigue; Sung-Hoon Ahn

    2016-01-01

    Deployable structure composed of smart materials based actuators can reconcile its inherently conflicting requirements of low mass, good shape adaptability, and high load-bearing capability. This work describes the fabrication of deployable structures using smart soft composite actuators combining a soft matrix with variable stiffness properties and hinge-like movement through a rigid skeleton. The hinge actuator has the advantage of being simple to fabricate, inexpensive, lightweight and sim...

  18. Dynamics of Soft Matter

    CERN Document Server

    García Sakai, Victoria; Chen, Sow-Hsin

    2012-01-01

    Dynamics of Soft Matter: Neutron Applications provides an overview of neutron scattering techniques that measure temporal and spatial correlations simultaneously, at the microscopic and/or mesoscopic scale. These techniques offer answers to new questions arising at the interface of physics, chemistry, and biology. Knowledge of the dynamics at these levels is crucial to understanding the soft matter field, which includes colloids, polymers, membranes, biological macromolecules, foams, emulsions towards biological & biomimetic systems, and phenomena involving wetting, friction, adhesion, or micr

  19. Hard and Soft

    OpenAIRE

    Claes H. de Vreese; Boomgaarden, Hajo G.; Semetko, Holli A.

    2008-01-01

    Abstract Support for European integration is a function no longer only of `hard' economic and utilitarian predictors but also of `soft' predictors such as feelings of identity and attitudes towards immigrants. Focusing on the issue of the potential membership of Turkey in the European Union (EU), this study demonstrates that the importance of `soft' predictors outweighs the role of `hard' predictors in understanding public opinion about Turkish membership. The study draws on survey...

  20. Taxing Soft Drinks

    OpenAIRE

    Roy Bahl

    2011-01-01

    This paper reviews the practice of levying an excise tax on soft drinks in sub-saharan African countries, and evaluates this practice against theoretical norms for levying an excise tax. The question is whether such taxes are justified or whether they are discriminatory and impose a welfare cost on the country. The paper concludes that the sin tax justification does not hold for soft drinks, nor do income distribution justifications. Arguably the best reason for such a levy is revenue, but th...

  1. In Situ Raman Analyses of Natural Gas and Gas Hydrates at Hydrate Ridge, Oregon

    Science.gov (United States)

    Peltzer, E. T.; White, S. N.; Dunk, R. M.; Brewer, P. G.; Sherman, A. D.; Schmidt, K.; Hester, K. C.; Sloan, E. D.

    2004-12-01

    During a July 2004 cruise to Hydrate Ridge, Oregon, MBARI's sea-going laser Raman spectrometer was used to obtain in situ Raman spectra of natural gas hydrates and natural gas venting from the seafloor. This was the first in situ analysis of gas hydrates on the seafloor. The hydrate spectra were compared to laboratory analyses performed at the Center for Hydrate Research, Colorado School of Mines. The natural gas spectra were compared to MBARI gas chromatography (GC) analyses of gas samples collected at the same site. DORISS (Deep Ocean Raman In Situ Spectrometer) is a laboratory model laser Raman spectrometer from Kaiser Optical Systems, Inc modified at MBARI for deployment in the deep ocean. It has been successfully deployed to depths as great as 3600 m. Different sampling optics provide flexibility in adapting the instrument to a particular target of interest. An immersion optic was used to analyze natural gas venting from the seafloor at South Hydrate Ridge ( ˜780 m depth). An open-bottomed cube was placed over the vent to collect the gas. The immersion optic penetrated the side of the cube as did a small heater used to dissociate any hydrate formed during sample collection. To analyze solid hydrates at both South and North Hydrate Ridge ( ˜590 m depth), chunks of hydrate were excavated from the seafloor and collected in a glass cylinder with a mesh top. A stand-off optic was used to analyze the hydrate inside the cylinder. Due to the partial opacity of the hydrate and the small focal volume of the sampling optic, a precision underwater positioner (PUP) was used to focus the laser spot onto the hydrate. PUP is a stand-alone system with three degrees-of-freedom, capable of moving the DORISS probe head with a precision of 0.1 mm. In situ Raman analyses of the gas indicate that it is primarily methane. This is verified by GC analyses of samples collected from the same site. Other minor constituents (such as CO2 and higher hydrocarbons) are present but may be in

  2. Contact Dermatitis in Pediatrics.

    Science.gov (United States)

    Pelletier, Janice L; Perez, Caroline; Jacob, Sharon E

    2016-08-01

    Contact dermatitis is an umbrella term that describes the skin's reaction to contacted noxious or allergenic substances. The two main categories of contact dermatitis are irritant type and allergic type. This review discusses the signs, symptoms, causes, and complications of contact dermatitis. It addresses the testing, treatment, and prevention of contact dermatitis. Proper management of contact dermatitis includes avoidance measures for susceptible children. Implementation of a nickel directive (regulating the use of nickel in jewelry and other products that come into contact with the skin) could further reduce exposure to the most common allergens in the pediatric population. [Pediatr Ann. 2016;45(8):e287-e292.].

  3. Methane hydrate-bearing sediments in the Terrebonne basin, northern Gulf of Mexico

    Science.gov (United States)

    Meazell, K.; Flemings, P. B.

    2015-12-01

    We characterize the geological, geophysical, and thermodynamic state of three dipping, hydrate-bearing sands in the Terrebonne mini basin of the northern Gulf of Mexico, and describe three potential drilling locations to sample these hydrate reservoirs. Within the sand bodies, there is a prominent negative polarity seismic reflection (opposite phase to the seafloor reflector) that we interpret to record the boundary between gas hydrate above and free gas below. This anomaly is the Bottom Simulating Reflector (BSR) and the base of the Gas Hydrate Stability Zone (BGHSZ). Above the BSR, reflection seismic data record these reservoirs with a positive polarity while below it, they record the reservoirs with a negative polarity event. Within the sand bodies, seismic amplitudes are generally strongest immediately above and below the BSR and weaken in updip and downdip directions. Beneath the BSR, two of the reservoirs have a strong negative amplitude event that parallels structure that we interpret to record a gas-water contact, while the third reservoir does not clearly record this behavior. Much like the seafloor, the BSR is bowl-shaped, occurring at greatest depths in the northwest and rising near salt bodies in the south and east. In the north east area of previous exploration, the BSR is found at a depth of 2868 meters below sealevel, implying a geothermal gradient of 20.1oC/km for type I hydrates. Logging while drilling data reveal that the sands are composed of numerous thin, hydrocarbon-charged, coarse-grained sediments. Hydrate saturation in these sands is greatest near the BGHSZ. Pressure coring is proposed for three wells that will penetrate the reservoirs at different structural elevations in order to further elucidate reservoir conditions of the sands.

  4. Soft tissue infections and the diabetic foot.

    Science.gov (United States)

    Smith, A J; Daniels, T; Bohnen, J M

    1996-12-01

    Soft tissue infections are classified as local or spreading. Spreading soft tissue infections are potentially life-threatening conditions, requiring prompt diagnosis and treatment. The information presented is based on a literature review and the authors' clinical experience. Diagnosis of soft tissue infections is aimed at determining the level of infection (skin, fascia, muscle) and whether necrosis is present. The bacteriology of these infections is varied and is of secondary importance. Treatment of skin infections that have no dead tissue is with antibiotics alone. Infections at the fascial or muscle level and those with necrosis at any level require surgical debridement and adjuvant antibiotics. The feet of diabetic patients are prone to plantar forefoot ulcers associated with tissue destruction and infection. The vast majority are caused by mechanical factors. If local immune defenses are adequate, bacterial colonization occurs without infection. Most diabetic foot ulcers will respond to relief of pressure, which may require total contact casting. Antibiotics and debridement are required in infected or deep ulcers, or when the ulcer does not respond to total contact casting.

  5. Using magnetic resonance imaging to monitor CH4 hydrate formation and spontaneous conversion of CH4 hydrate to CO2 hydrate in porous media.

    Science.gov (United States)

    Baldwin, Bernard A; Stevens, Jim; Howard, James J; Graue, Arne; Kvamme, Bjorn; Aspenes, Erick; Ersland, Geir; Husebø, Jarle; Zornes, David R

    2009-06-01

    Magnetic resonance imaging was used to monitor and quantify methane hydrate formation and exchange in porous media. Conversion of methane hydrate to carbon dioxide hydrate, when exposed to liquid carbon dioxide at 8.27 MPa and approximately 4 degrees C, was experimentally demonstrated with MRI data and verified by mass balance calculations of consumed volumes of gases and liquids. No detectable dissociation of the hydrate was measured during the exchange process.

  6. Controls on Gas Hydrate Formation and Dissociation

    Energy Technology Data Exchange (ETDEWEB)

    Miriam Kastner; Ian MacDonald

    2006-03-03

    The main objectives of the project were to monitor, characterize, and quantify in situ the rates of formation and dissociation of methane hydrates at and near the seafloor in the northern Gulf of Mexico, with a focus on the Bush Hill seafloor hydrate mound; to record the linkages between physical and chemical parameters of the deposits over the course of one year, by emphasizing the response of the hydrate mound to temperature and chemical perturbations; and to document the seafloor and water column environmental impacts of hydrate formation and dissociation. For these, monitoring the dynamics of gas hydrate formation and dissociation was required. The objectives were achieved by an integrated field and laboratory scientific study, particularly by monitoring in situ formation and dissociation of the outcropping gas hydrate mound and of the associated gas-rich sediments. In addition to monitoring with the MOSQUITOs, fluid flow rates and temperature, continuously sampling in situ pore fluids for the chemistry, and imaging the hydrate mound, pore fluids from cores, peepers and gas hydrate samples from the mound were as well sampled and analyzed for chemical and isotopic compositions. In order to determine the impact of gas hydrate dissociation and/or methane venting across the seafloor on the ocean and atmosphere, the overlying seawater was sampled and thoroughly analyzed chemically and for methane C isotope ratios. At Bush hill the pore fluid chemistry varies significantly over short distances as well as within some of the specific sites monitored for 440 days, and gas venting is primarily focused. The pore fluid chemistry in the tub-warm and mussel shell fields clearly documented active gas hydrate and authigenic carbonate formation during the monitoring period. The advecting fluid is depleted in sulfate, Ca Mg, and Sr and is rich in methane; at the main vent sites the fluid is methane supersaturated, thus bubble plumes form. The subsurface hydrology exhibits both

  7. Solid state tungsten oxide hydrate/tin oxide hydrate electrochromic device prepared by electrochemical reactions

    Science.gov (United States)

    Nishiyama, Kentaro; Matsuo, Ryo; Sasano, Junji; Yokoyama, Seiji; Izaki, Masanobu

    2017-03-01

    The solid state electrochromic device composed of tungsten oxide hydrate (WO3(H2O)0.33) and tin oxide hydrate (Sn(O,OH)) has been constructed by anodic deposition of WO3(H2O)0.33 and Sn(O,OH) layers and showed the color change from clear to blue by applying voltage through an Au electrode.

  8. Kinetic studies of gas hydrate formation with low-dosage hydrate inhibitors

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Pipeline blockage by gas hydrates is a serious problem in the petroleum industry.Low-dosage inhibitors have been developed for its cost-effective and environmentally acceptable characteristics.In a 1.072-L reactor with methane,ethane and propane gas mixture under the pressure of about 8.5 MPa at 4 °C,hydrate formation was investigated with low-dosage hydrate inhibitors PVP and GHI1,the change of the compressibility factor and gas composition in the gas phase was analyzed,the gas contents in hydrates were compared with PVP and GHI1 added,and the inhibition mechanism of GHI1 was discussed.The results show that PVP and GHI1 could effectively inhibit the growth of gas hydrates but not nucleation.Under the experimental condition with PVP added,methane and ethane occupied the small cavities of the hydrate crystal unit and the ability of ethane entering into hydrate cavities was weaker than that of methane.GHI1 could effectively inhibit molecules which could more readily form hydrates.The ether and hydroxy group of diethylene glycol monobutyl ether have the responsibility for stronger inhibition ability of GHI1 than PVP.

  9. Kinetic inhibition of natural gas hydrates in offshore drilling, production, and processing operations. Annual report, January 1--December 31, 1992

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1992-12-31

    Natural gas hydrates are solid crystalline compounds which form when molecules smaller than n-butane contact molecules of water at elevated pressures and reduced temperatures, both above and below the ice point. Because these crystalline compounds plug flow channels, they are undesirable. In this project the authors proposed an alternate approach of controlling hydrate formation by preventing hydrate growth into a sizeable mass which could block a flow channel. The authors call this new technique kinetic inhibition, because while it allows the system to exist in the hydrate domain, it prevents the kinetic agglomeration of small hydrate crystals to the point of pluggage of a flow channel. In order to investigate the kinetic means of inhibiting hydrate formation, they held two consortium meetings, on June 1, 1990 and on August 31, 1990. At subsequent meetings, the authors determined the following four stages of the project, necessary to reach the goal of determining a new hydrate field inhibitor: (1) a rapid screening method was to be determined for testing the hydrate kinetic formation period of many surfactants and polymer candidates (both individually and combined), the present report presents the success of two screening apparatuses: a multi-reactor apparatus which is capable of rapid, high volume screening, and the backup screening method--a viscometer for testing with gas at high pressure; (2) the construction of two high, constant pressure cells were to experimentally confirm the success of the chemicals in the rapid screening apparatus; (3) in the third phase of the work, Exxon volunteered to evaluate the performance of the best chemicals from the previous two stages in their 4 inch I.D. Multiphase flow loop in Houston; (4) in the final phase of the work, the intention was to take the successful kinetic inhibition chemicals from the previous three stages and then test them in the field in gathering lines and wells from member companies.

  10. Experimental characterization of production behavior accompanying the hydrate reformation in methane hydrate bearing sediments

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, T.; Kang, J.M.; Nguyen, H.T. [Seoul National Univ., Seoul (Korea, Republic of); Park, C. [Kangwon National Univ., (Korea, Republic of); Lee, J. [Korea Inst., of Geoscience and Mineral Resources (Korea, Republic of)

    2010-07-01

    This study investigated the production behaviour associated with gas hydrate reformation in methane hydrate-bearing sediment by hot-brine injection. A range of different temperature and brine injection rates were used to analyze the pressure and temperature distribution, the gas production behaviour and the movement of the dissociation front. The study showed that hydrate reformation reduces the production rate considerably at an early time. However, gas production increases during the dissociation, near the outlet because the dissociated methane around the inlet is consumed in reforming the hydrate and increases the hydrate saturation around the outlet. Higher temperature also increases the gas production rate and the speed of the dissociation front. 12 refs., 2 tabs., 4 figs.

  11. International rigid contact lens prescribing.

    Science.gov (United States)

    Efron, Nathan; Morgan, Philip B; Helland, Magne; Itoi, Motozumi; Jones, Deborah; Nichols, Jason J; van der Worp, Eef; Woods, Craig A

    2010-06-01

    Rigid lenses have been fitted less since the introduction of soft lenses nearly 40 years ago. Data that we have gathered from annual contact lens fitting surveys conducted in Australia, Canada, Japan, the Netherlands, Norway, the UK and the USA between 2000 and 2008 facilitate an accurate characterization of the pattern of the decline of rigid lens fitting during the first decade of this century. There is a trend for rigid lenses to be utilized primarily for refitting those patients who are already successful rigid lens wearers-most typically older females being refit with higher Dk materials. Rigid lenses are generally fitted on a full-time basis (four or more days of wear per week) without a planned replacement schedule. Orthokeratology is especially popular in the Netherlands, but is seldom prescribed in the other countries surveyed.

  12. PMR Characterization of the Water Structure in Tibetan Milk Mushroom Zooglea: Influence of Medium Hydration and Hydrophobicity

    Science.gov (United States)

    Krupskaya, T. V.; Prylutskyy, Yu. I.; Evstigneev, M. P.; Tsapko, M. D.; Turov, V. V.

    2015-07-01

    The state of water in Tibetan milk mushroom zooglea with different degrees of hydration (h) was investigated using low-temperature PMR spectroscopy in air and in contact with the hydrophobic media polydimethylsiloxane PDMS-1000 and CHCl3 with added trifl uoroacetic acid (TFA). The maximum hydration of the zooglea amounted to h = 32 g/g (of dry matter). Water existed as polyassociates (clusters or domains) of strongly and weakly associated water. Bound water decomposed into clusters in the presence of TFA. The NMR spectra showed six types of bound water at h = 0.3 g/g.

  13. Authigenic gypsum found in gas hydrate-associated sediments from Hydrate Ridge, the eastern North Pacific

    Institute of Scientific and Technical Information of China (English)

    WANG; Jiasheng; Erwin; Suess; Dirk; Rickert

    2004-01-01

    Characteristic gypsum micro-sphere and granular mass were discovered by binocular microscope in the gas hydrate-associated sediments at cores SO143-221 and SO143/TVG40-2A respectively on Hydrate Ridge of Cascadia margin, the eastern North Pacific. XRD patterns and EPA analyses show both micro-sphere and granular mass of the crystals have the typical peaks and the typical main chemical compositions of gypsum, although their weight percents are slightly less than the others in the non-gas hydrate-associated marine regions. SEM pictures show that the gypsum crystals have clear crystal boundaries, planes, edges and cleavages of gypsum in form either of single crystal or of twin crystals. In view of the fact that there are meanwhile gas hydrate-associated authigenic carbonates and SO42(-rich pore water in the same sediment cores, it could be inferred reasonably that the gypsums formed also authigenically in the gas hydrate-associated environment too, most probably at the interface between the downward advecting sulfate-rich seawater and the below gas hydrate, which spilled calcium during its formation on Hydrate Ridge. The two distinct forms of crystal intergrowth, which are the granular mass of series single gypsum crystals at core SO143/TVG40-2A and the microsphere of gypsum crystals accompanied with detrital components at core SO143-221 respectively, indicate that they precipitated most likely in different interstitial water dynamic environments. So, the distinct authigenic gypsums found in gas hydrate-associated sediments on Hydrate Ridge could also be believed as one of the parameters which could be used to indicate the presence of gas hydrate in an unknown marine sediment cores.

  14. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Richard Sigal; Kent Newsham; Thomas Williams; Barry Freifeld; Timothy Kneafsey; Carl Sondergeld; Shandra Rai; Jonathan Kwan; Stephen Kirby; Robert Kleinberg; Doug Griffin

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. The work scope drilled and cored a well The Hot Ice No. 1 on Anadarko leases beginning in FY 2003 and completed in 2004. An on-site core analysis laboratory was built and utilized for determining the physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. The final efforts of the project are to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists developing reservoir models. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained in this report. The Hot Ice No. 1 well was drilled from the surface to a measured depth of 2300 ft. There was almost 100% core recovery from the bottom of surface casing at 107 ft to total depth. Based on the best estimate of the bottom of the methane hydrate stability zone (which used new data obtained from Hot Ice No. 1 and new analysis of data from adjacent wells), core was recovered over its complete range. Approximately 580 ft of porous, mostly frozen, sandstone and 155 of conglomerate were recovered in the Ugnu Formation and approximately 215 ft of porous sandstone were recovered in the West Sak Formation. There were gas shows in the bottom

  15. Experimental Determination of Refractive Index of Gas Hydrates

    DEFF Research Database (Denmark)

    Bylov, Martin; Rasmussen, Peter

    1997-01-01

    The refractive indexes of methane hydrate and natural gas hydrate have been experimentally determined. The refractive indexes were determined in an indirect manner making use of the fact that two non-absorbing materials will have the same refractive index if they cannot be distinguished visually....... For methane hydrate (structure I) the refractive index was found to be 1.346 and for natural gas hydrate (structure II) it was found to be 1.350. The measurements further suggest that the gas hydrate growth rate increases if the water has formed hydrates before. The induction time, on the other hand, seems...

  16. First-principles elasticity of monocarboaluminate hydrates

    KAUST Repository

    Moon, J.

    2014-07-01

    The elasticity of monocarboaluminate hydrates, 3CaO·Al2O3·CaCO3·xH2O (x = 11 or 8), has been investigated by first-principles calculations. Previous experimental study revealed that the fully hydrated monocarboaluminate (x = 11) exhibits exceptionally low compressibility compared to other reported calcium aluminate hydrates. This stiff hydration product can contribute to the strength of concrete made with Portland cements containing calcium carbonates. In this study, full elastic tensors and mechanical properties of the crystal structures with different water contents (x = 11 or 8) are computed by first-principles methods based on density functional theory. The results indicate that the compressibility of monocarboaluminate is highly dependent on the water content in the interlayer region. The structure also becomes more isotropic with the addition of water molecules in this region. Since the monocarboaluminate is a key hydration product of limestone added cement, elasticity of the crystal is important to understand its mechanical impact on concrete. Besides, it is put forth that this theoretical calculation will be useful in predicting the elastic properties of other complex cementitous materials and the influence of ion exchange on compressibility.

  17. Interfacial phenomena in gas hydrate systems.

    Science.gov (United States)

    Aman, Zachary M; Koh, Carolyn A

    2016-03-21

    Gas hydrates are crystalline inclusion compounds, where molecular cages of water trap lighter species under specific thermodynamic conditions. Hydrates play an essential role in global energy systems, as both a hinderance when formed in traditional fuel production and a substantial resource when formed by nature. In both traditional and unconventional fuel production, hydrates share interfaces with a tremendous diversity of materials, including hydrocarbons, aqueous solutions, and inorganic solids. This article presents a state-of-the-art understanding of hydrate interfacial thermodynamics and growth kinetics, and the physiochemical controls that may be exerted on both. Specific attention is paid to the molecular structure and interactions of water, guest molecules, and hetero-molecules (e.g., surfactants) near the interface. Gas hydrate nucleation and growth mechanics are also presented, based on studies using a combination of molecular modeling, vibrational spectroscopy, and X-ray and neutron diffraction. The fundamental physical and chemical knowledge and methods presented in this review may be of value in probing parallel systems of crystal growth in solid inclusion compounds, crystal growth modifiers, emulsion stabilization, and reactive particle flow in solid slurries.

  18. Soft and Ultra-soft Elastomers

    Science.gov (United States)

    Daniel, William; Burdynska, Joanna; Kirby, Sam; Zhou, Yang; Matyjaszewski, Krzysztof; Rubinstein, Michael; Sheiko, Sergei; UNC-MIRT Team

    2014-03-01

    Polymeric networks are attractive engineering materials utilized for various mechanically demanding applications. As such, much attention has been paid to reinforcement of polymer mechanical properties with little interest in how to make softer elastomers to address numerous biomedical applications including implants and cell differentiation. Without swelling in a solvent, it is challenging to obtain materials with a modulus below ca.105 Pa, which is dictated by chain entanglements. Here we present two methodologies for the creation of soft and ultra-soft dry elastomeric compounds. The first method utilizes polymer capsules as temperature responsive filler. Depending on volume fraction of microcapsules this method is capable of fine tuning modulus within an order of magnitude. The second technique uses the densely grafted molecular brush architecture to create solvent-free polymer melts and elastomers with plateau moduli in the range one hundred to ten hundred Pa. Such compounds may find uses in biomedical applications including reconstructive surgery and cell differentiation. National Science Foundation DMR-1122483.

  19. Stability evaluation of hydrate-bearing sediments during thermally-driven hydrate dissociation

    Science.gov (United States)

    Kwon, T.; Cho, G.; Santamarina, J.; Kim, H.; Lee, J.

    2009-12-01

    Hydrate-bearing sediments may destabilize spontaneously as part of geological processes, unavoidably during petroleum drilling/production operations, or intentionally as part of gas extraction from the hydrate itself. In all cases, high pore fluid pressure generation is anticipated during hydrate dissociation. This study examined how thermal changes destabilize gas hydrate-bearing sediments. First, an analytical formulation was derived for predicting fluid pressure evolution in hydrate-bearing sediments subjected to thermal stimulation without mass transfer. The formulation captures the self-preservation behavior, calculates the hydrate and free gas quantities during dissociation, considering effective stress-controlled sediment compressibility and gas solubility in aqueous phase. Pore fluid pressure generation is proportional to the initial hydrate fraction and the sediment bulk stiffness; is inversely proportional to the initial gas fraction and gas solubility; and is limited by changes in effective stress that cause the failure of the sediment. Second, the analytical formulation for hydrate dissociation was incorporated as a user-defined function into a verified finite difference code (FLAC2D). The underlying physical processes of hydrate-bearing sediments, including hydrate dissociation, self-preservation, pore pressure evolution, gas dissolution, and sediment volume expansion, were coupled with the thermal conduction, pore fluid flow, and mechanical response of sediments. We conducted the simulations for a duration of 20 years, assuming a constant-temperature wellbore transferred heat to the surrounding hydrate-bearing sediments, resulting in dissociation of methane hydrate in the well vicinity. The model predicted dissociation-induced excess pore fluid pressures which resulted in a large volume expansion and plastic deformation of the sediments. Furthermore, when the critical stress was reached, localized shear failure of the sediment around the borehole was

  20. Hard and Soft Governance

    DEFF Research Database (Denmark)

    Moos, Lejf

    2009-01-01

    and discusses governance forms at several levels. The first layer is the global: the methods of 'soft governance' that are being utilised by transnational agencies. The second layer is the national and local: the shift in national and local governance seen in many countries, but here demonstrated in the case......The governance and leadership at transnational, national and school level seem to be converging into a number of isomorphic forms as we see a tendency towards substituting 'hard' forms of governance, that are legally binding, with 'soft' forms based on persuasion and advice. This article analyses...... of Denmark, and finally the third layer: the leadership used in Danish schools. The use of 'soft governance' is shifting the focus of governance and leadership from decisions towards influence and power and thus shifting the focus of the processes from the decision-making itself towards more focus...

  1. Introductory physics going soft

    Science.gov (United States)

    Langbeheim, Elon; Livne, Shelly; Safran, Samuel A.; Yerushalmi, Edit

    2012-01-01

    We describe an elective course on soft matter at the level of introductory physics. Soft matter physics serves as a context that motivates the presentation of basic ideas in statistical thermodynamics and their applications. It also is an example of a contemporary field that is interdisciplinary and touches on chemistry, biology, and physics. We outline a curriculum that uses the lattice gas model as a quantitative and visual tool, initially to introduce entropy, and later to facilitate the calculation of interactions. We demonstrate how free energy minimization can be used to teach students to understand the properties of soft matter systems such as the phases of fluid mixtures, wetting of interfaces, self-assembly of surfactants, and polymers. We discuss several suggested activities in the form of inquiry projects which allow students to apply the concepts they have learned to experimental systems.

  2. Numerical analysis of elastic coated solids in line contact

    Institute of Scientific and Technical Information of China (English)

    王廷剑; 王黎钦; 古乐; 赵小力

    2015-01-01

    A line contact model of elastic coated solids is presented based on the influence coefficients (ICs) of surface displacement and stresses of coating−substrate system and the traditional contact model. The ICs of displacement and stresses are obtained from their corresponding frequency response functions (FRF) by using a conversion method based on fast Fourier transformation (FFT). The contact pressure and the stress field in the subsurface are obtained by employing conjugate gradient method (CGM) and discrete convolution fast Fourier transformation (DC-FFT). Comparison of the contact pressure and subsurface stresses obtained by the numerical method with the exact analytical solutions for Hertz contact is conducted, and the results show that the numerical solution has a very high accuracy and verify the validity of the contact model. The effect of the stiffness and thickness of coatings is further numerically studied. The result shows that the effects on contact pressure and contact width are opposite for hard and soft coatings and are intensified with the increase of coating thickness; the locations of crack initiation and propagation are different for soft and hard coatings; the risk of cracks and delaminations of coatings can be brought down by improving the lubrication condition or optimizing the non-dimensional parameterh/bh. This research offers a tool to numerically analyze the problem of elastic coated solids in line contact and make the blindness and randomness of trial-type coating design less.

  3. A novel method for single sample multi-axial nanoindentation of hydrated heterogeneous tissues based on testing great white shark jaws.

    Science.gov (United States)

    Ferrara, Toni L; Boughton, Philip; Slavich, Eve; Wroe, Stephen

    2013-01-01

    Nanomechanical testing methods that are suitable for a range of hydrated tissues are crucial for understanding biological systems. Nanoindentation of tissues can provide valuable insights into biology, tissue engineering and biomimetic design. However, testing hydrated biological samples still remains a significant challenge. Shark jaw cartilage is an ideal substrate for developing a method to test hydrated tissues because it is a unique heterogeneous composite of both mineralized (hard) and non-mineralized (soft) layers and possesses a jaw geometry that is challenging to test mechanically. The aim of this study is to develop a novel method for obtaining multidirectional nanomechanical properties for both layers of jaw cartilage from a single sample, taken from the great white shark (Carcharodon carcharias). A method for obtaining multidirectional data from a single sample is necessary for examining tissue mechanics in this shark because it is a protected species and hence samples may be difficult to obtain. Results show that this method maintains hydration of samples that would otherwise rapidly dehydrate. Our study is the first analysis of nanomechanical properties of great white shark jaw cartilage. Variation in nanomechanical properties were detected in different orthogonal directions for both layers of jaw cartilage in this species. The data further suggest that the mineralized layer of shark jaw cartilage is less stiff than previously posited. Our method allows multidirectional nanomechanical properties to be obtained from a single, small, hydrated heterogeneous sample. Our technique is therefore suitable for use when specimens are rare, valuable or limited in quantity, such as samples obtained from endangered species or pathological tissues. We also outline a method for tip-to-optic calibration that facilitates nanoindentation of soft biological tissues. Our technique may help address the critical need for a nanomechanical testing method that is applicable

  4. A novel method for single sample multi-axial nanoindentation of hydrated heterogeneous tissues based on testing great white shark jaws.

    Directory of Open Access Journals (Sweden)

    Toni L Ferrara

    Full Text Available Nanomechanical testing methods that are suitable for a range of hydrated tissues are crucial for understanding biological systems. Nanoindentation of tissues can provide valuable insights into biology, tissue engineering and biomimetic design. However, testing hydrated biological samples still remains a significant challenge. Shark jaw cartilage is an ideal substrate for developing a method to test hydrated tissues because it is a unique heterogeneous composite of both mineralized (hard and non-mineralized (soft layers and possesses a jaw geometry that is challenging to test mechanically. The aim of this study is to develop a novel method for obtaining multidirectional nanomechanical properties for both layers of jaw cartilage from a single sample, taken from the great white shark (Carcharodon carcharias. A method for obtaining multidirectional data from a single sample is necessary for examining tissue mechanics in this shark because it is a protected species and hence samples may be difficult to obtain. Results show that this method maintains hydration of samples that would otherwise rapidly dehydrate. Our study is the first analysis of nanomechanical properties of great white shark jaw cartilage. Variation in nanomechanical properties were detected in different orthogonal directions for both layers of jaw cartilage in this species. The data further suggest that the mineralized layer of shark jaw cartilage is less stiff than previously posited. Our method allows multidirectional nanomechanical properties to be obtained from a single, small, hydrated heterogeneous sample. Our technique is therefore suitable for use when specimens are rare, valuable or limited in quantity, such as samples obtained from endangered species or pathological tissues. We also outline a method for tip-to-optic calibration that facilitates nanoindentation of soft biological tissues. Our technique may help address the critical need for a nanomechanical testing method

  5. Mechanics of soft materials

    CERN Document Server

    Volokh, Konstantin

    2016-01-01

    This book provides a concise introduction to soft matter modelling. It offers an up-to-date review of continuum mechanical description of soft and biological materials from the basics to the latest scientific materials. It includes multi-physics descriptions, such as chemo-, thermo-, electro- mechanical coupling. It derives from a graduate course at Technion that has been established in recent years. It presents original explanations for some standard materials and features elaborated examples on all topics throughout the text. PowerPoint lecture notes can be provided to instructors. .

  6. Results on fuzzy soft topological spaces

    CERN Document Server

    Mahanta, J

    2012-01-01

    B. Tanay et. al. introduced and studied fuzzy soft topological spaces. Here we introduce fuzzy soft point and study the concept of neighborhood of a fuzzy soft point in a fuzzy soft topological space. We also study fuzzy soft closure and fuzzy soft interior. Separation axioms and connectedness are introduced and investigated for fuzzy soft topological spaces.

  7. Methane hydrates in nature - Current knowledge and challenges

    Science.gov (United States)

    Collett, Timothy S.

    2014-01-01

    Recognizing the importance of methane hydrate research and the need for a coordinated effort, the United States Congress enacted the Methane Hydrate Research and Development Act of 2000. At the same time, the Ministry of International Trade and Industry in Japan launched a research program to develop plans for a methane hydrate exploratory drilling project in the Nankai Trough. India, China, the Republic of Korea, and other nations also have established large methane hydrate research and development programs. Government-funded scientific research drilling expeditions and production test studies have provided a wealth of information on the occurrence of methane hydrates in nature. Numerous studies have shown that the amount of gas stored as methane hydrates in the world may exceed the volume of known organic carbon sources. However, methane hydrates represent both a scientific and technical challenge, and much remains to be learned about their characteristics and occurrence in nature. Methane hydrate research in recent years has mostly focused on: (1) documenting the geologic parameters that control the occurrence and stability of methane hydrates in nature, (2) assessing the volume of natural gas stored within various methane hydrate accumulations, (3) analyzing the production response and characteristics of methane hydrates, (4) identifying and predicting natural and induced environmental and climate impacts of natural methane hydrates, (5) analyzing the methane hydrate role as a geohazard, (6) establishing the means to detect and characterize methane hydrate accumulations using geologic and geophysical data, and (7) establishing the thermodynamic phase equilibrium properties of methane hydrates as a function of temperature, pressure, and gas composition. The U.S. Department of Energy (DOE) and the Consortium for Ocean Leadership (COL) combined their efforts in 2012 to assess the contributions that scientific drilling has made and could continue to make to advance

  8. Apparatus investigates geological aspects of gas hydrates

    Science.gov (United States)

    Booth, J.S.; Winters, W.J.; Dillon, William P.

    1999-01-01

    The US Geological Survey has developed a laboratory research system which allows the study of the creation and dissociation of gas hydrates under deepwater conditions and with different sediment types and pore fluids. The system called GHASTLI (gas hydrate and sediment test laboratory instrument) comprises a pressure chamber which holds a sediment specimen, and which can simulate water depths to 2,500m and different sediment overburden. Seawater and gas flow through a sediment specimen can be precisely controlled and monitored. It can simulate a wide range of geology and processes and help to improve understanding of gas hydrate processes and aid prediction of geohazards, their control and potential use as an energy source. This article describes GHASTLI and how it is able to simulate natural conditions, focusing on fluid volume, acoustic velocity-compressional and shear wave, electric resistance, temperature, pore pressure, shear strength, and permeability.

  9. Simulation of Methane Recovery from Gas Hydrates Combined with Storing Carbon Dioxide as Hydrates

    Directory of Open Access Journals (Sweden)

    Georg Janicki

    2011-01-01

    Full Text Available In the medium term, gas hydrate reservoirs in the subsea sediment are intended as deposits for carbon dioxide (CO2 from fossil fuel consumption. This idea is supported by the thermodynamics of CO2 and methane (CH4 hydrates and the fact that CO2 hydrates are more stable than CH4 hydrates in a certain P-T range. The potential of producing methane by depressurization and/or by injecting CO2 is numerically studied in the frame of the SUGAR project. Simulations are performed with the commercial code STARS from CMG and the newly developed code HyReS (hydrate reservoir simulator especially designed for hydrate processing in the subsea sediment. HyReS is a nonisothermal multiphase Darcy flow model combined with thermodynamics and rate kinetics suitable for gas hydrate calculations. Two scenarios are considered: the depressurization of an area 1,000 m in diameter and a one/two-well scenario with CO2 injection. Realistic rates for injection and production are estimated, and limitations of these processes are discussed.

  10. Soft n-Ary Subgroups

    Directory of Open Access Journals (Sweden)

    D.R. Prince Williams

    2015-09-01

    Full Text Available Soft set theory plays a vital role in solving many complicated problems with inherited uncertainty. An n-ary algebraic systems is a generalization of algebraic structures and it is the most natural way for the further development, deeper understanding of their properties. In this paper, we apply soft set theory to an n-ary algebraic systems and introduce the notions of soft n-ary groups and soft n-ary subgroups. Further, some operations on soft sets are extended to the former. Finally, we provide the characterization of soft n-ary subgroups over an n-ary group (G,f and study their related properties.

  11. The Adjunctive Soft-Tissue Diode Laser in Orthodontics.

    Science.gov (United States)

    Borzabadi-Farahani, Ali

    2017-04-01

    Lasers are a relatively new addition to the orthodontist's armamentarium. This article reviews the fundamental basic science of available soft-tissue lasers, with an emphasis on diode lasers, and discusses various adjunct applications of the diode laser for soft-tissue orthodontic procedures. Diode lasers function by cutting with an initiated hot tip and produce minimal to no interaction with healthy dental hard tissue, making them suitable for soft-tissue procedures. The contact cutting mode provides enhanced bloodless site visibility and facility to perform delicate soft tissue procedures, which is important in areas with difficult access. Such adjunctive uses include laser gingivectomy to improve oral hygiene or bracket positioning, esthetic laser gingival recontouring, and laser exposure of superficially impacted teeth. Selected cases treated with a 940-nm indium-gallium-arsenide-phosphide (InGaAsP) diode laser will be presented.

  12. Some properties of fuzzy soft proximity spaces.

    Science.gov (United States)

    Demir, İzzettin; Özbakır, Oya Bedre

    2015-01-01

    We study the fuzzy soft proximity spaces in Katsaras's sense. First, we show how a fuzzy soft topology is derived from a fuzzy soft proximity. Also, we define the notion of fuzzy soft δ-neighborhood in the fuzzy soft proximity space which offers an alternative approach to the study of fuzzy soft proximity spaces. Later, we obtain the initial fuzzy soft proximity determined by a family of fuzzy soft proximities. Finally, we investigate relationship between fuzzy soft proximities and proximities.

  13. Some Properties of Fuzzy Soft Proximity Spaces

    Science.gov (United States)

    Demir, İzzettin; Özbakır, Oya Bedre

    2015-01-01

    We study the fuzzy soft proximity spaces in Katsaras's sense. First, we show how a fuzzy soft topology is derived from a fuzzy soft proximity. Also, we define the notion of fuzzy soft δ-neighborhood in the fuzzy soft proximity space which offers an alternative approach to the study of fuzzy soft proximity spaces. Later, we obtain the initial fuzzy soft proximity determined by a family of fuzzy soft proximities. Finally, we investigate relationship between fuzzy soft proximities and proximities. PMID:25793224

  14. Contact Angle Goniometer

    Data.gov (United States)

    Federal Laboratory Consortium — Description:The FTA32 goniometer provides video-based contact angle and surface tension measurement. Contact angles are measured by fitting a mathematical expression...

  15. Corporate Consumer Contact API

    Data.gov (United States)

    General Services Administration — The data in the Corporate Consumer Contact API is based on the content you can find in the Corporate Consumer Contact listing in the Consumer Action Handbook (PDF)....

  16. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... lenses without a prescription in the United States. All contact lenses are medical devices that require a ... no such thing as a "one size fits all" contact lens. Lenses that are not properly fitted ...

  17. Dermatitis, contact (image)

    Science.gov (United States)

    This picture shows a skin inflammation (dermatitis) caused by contact with a material that causes an allergic reaction in this person. Contact dermatitis is a relatively common condition, and can be caused ...

  18. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... sell contacts without a prescription are breaking the law, and may be fined $11,000 per violation. " ... wear any kind of contact lens. In Butler's case, the lenses caused an infection and left her ...

  19. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... Contact Lenses Without a Prescription Sep. 26, 2013 It started as an impulsive buy from a souvenir ... Can Ruin Vision Eye Makeup Safety In fact, it is illegal to sell colored contact lenses without ...

  20. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... not require the same level of care or consideration as a standard contact lens because they can ... sell contacts without a prescription are breaking the law, and may be fined $11,000 per violation. " ...

  1. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... like a suction cup." Halloween is a popular time for people to use colored contact lenses to ... wear costume contact lenses for Halloween or any time of year, follow these guidelines: Get an eye ...

  2. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... glow-in-the-dark lizard lenses, costume contacts can certainly add a spooky, eye-popping touch. But ... consideration as a standard contact lens because they can be purchased over-the-counter or on the ...

  3. Contact Us about Asbestos

    Science.gov (United States)

    How to contact EPA for more information on asbestos, including state and regional contacts, EPA’s Asbestos Abatement/Management Ombudsman and the Toxic Substances Control Act (TSCA) Assistance Information Service (TSCA Hotline).

  4. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... popping touch. But colored contact lenses are popular year-round, not just at Halloween. But few know ... contact lenses for Halloween or any time of year, follow these guidelines: Get an eye exam from ...

  5. Simulating frictional contact in smoothed particle hydrodynamics

    Institute of Scientific and Technical Information of China (English)

    WANG; Jian; WU; Hao; GU; ChongShi; HUA; Hui

    2013-01-01

    Smoothed Particle Hydrodynamics (SPH) is a powerful tool for large deformation computation of soil flow. However, the method to simulate frictional contact in the framework of SPH is still absent and needs to be developed. This paper presents an algorithm to simulate frictional contact between soil and rigid or deformable structure in the framework of SPH. In this algo-rithm, the computational domain is divided into several sub-domains according to the existing contact boundaries, and contact forces are used as bridges of these sub-domains to fulfill problem solving. In the process of the SPH discretization for govern-ing equation of each sub-domain, the inherent problem of boundary deficiency of SPH is handled properly. Therefore, the par-ticles located at contact boundary can have precise acceleration, which is critical for contact detection. Then, based on the as-sumption that the SPH particle of soil can slightly penetrate into the structure, the contact forces along normal and tangential directions of the contact surface are computed by momentum principle, and the frictional force is modified if sliding occurs.Compared with previous methods, in which only particle-to-particle contact is considered or frictional sliding is just ignored,the method proposed in this study is more efficient and accurate, and is suitable for simulating interaction between soft materi-als and rigid or deformable structures, which are very common in geotechnical engineering. A number of numerical tests have been carried out to verify the accuracy and stability of the proposed algorithm, and the results have been compared with ana-lytical solutions or FEM results. The consistency obtained from these comparisons indicates that the algorithm is robust and can enhance the computing capability of SPH.

  6. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.

    2010-05-11

    Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. © 2010 The American Physical Society.

  7. Simulation of subsea gas hydrate exploitation

    Science.gov (United States)

    Janicki, Georg; Schlüter, Stefan; Hennig, Torsten; Deerberg, Görge

    2014-05-01

    The recovery of methane from gas hydrate layers that have been detected in several subsea sediments and permafrost regions around the world is a promising perspective to overcome future shortages in natural gas supply. Being aware that conventional natural gas resources are limited, research is going on to develop technologies for the production of natural gas from such new sources. Thus various research programs have started since the early 1990s in Japan, USA, Canada, India, and Germany to investigate hydrate deposits and develop required technologies. In recent years, intensive research has focussed on the capture and storage of CO2 from combustion processes to reduce climate impact. While different natural or man-made reservoirs like deep aquifers, exhausted oil and gas deposits or other geological formations are considered to store gaseous or liquid CO2, the storage of CO2 as hydrate in former methane hydrate fields is another promising alternative. Due to beneficial stability conditions, methane recovery may be well combined with CO2 storage in the form of hydrates. Regarding technological implementation many problems have to be overcome. Especially mixing, heat and mass transfer in the reservoir are limiting factors causing very long process times. Within the scope of the German research project »SUGAR« different technological approaches for the optimized exploitation of gas hydrate deposits are evaluated and compared by means of dynamic system simulations and analysis. Detailed mathematical models for the most relevant chemical and physical processes are developed. The basic mechanisms of gas hydrate formation/dissociation and heat and mass transport in porous media are considered and implemented into simulation programs. Simulations based on geological field data have been carried out. The studies focus on the potential of gas production from turbidites and their fitness for CO2 storage. The effects occurring during gas production and CO2 storage within

  8. GLASS TRANSITION OF HYDRATED WHEAT GLIADIN POWDERS

    Institute of Scientific and Technical Information of China (English)

    Shao-min Sun; Li Zhao; Yi-hu Song; Qiang Zheng

    2011-01-01

    Modulated-temperature differential scanning calorimetric and dynamic mechanical analyses and dielectric spectroscopy were used to investigate the glass transition of hydrated wheat gliadin powders with moisture absorption ranged from 2.30 db% to 18.21 db%. Glass transition temperature (Tg) of dry wheat gliadin was estimated according to the GordonTaylor equation. Structural heterogeneity at high degrees of hydration was revealed in dielectric temperature and frequency spectra. The activation energies (Ea) of the two relaxations were calculated from Arrhenius equation.

  9. Component analysis of the protein hydration entropy

    Science.gov (United States)

    Chong, Song-Ho; Ham, Sihyun

    2012-05-01

    We report the development of an atomic decomposition method of the protein solvation entropy in water, which allows us to understand global change in the solvation entropy in terms of local changes in protein conformation as well as in hydration structure. This method can be implemented via a combined approach based on molecular dynamics simulation and integral-equation theory of liquids. An illustrative application is made to 42-residue amyloid-beta protein in water. We demonstrate how this method enables one to elucidate the molecular origin for the hydration entropy change upon conformational transitions of protein.

  10. Buffering agents modify the hydration landscape at charged interfaces.

    Science.gov (United States)

    Trewby, William; Livesey, Duncan; Voïtchovsky, Kislon

    2016-03-07

    Buffering agents are widely used to stabilise the pH of solutions in soft matter and biological sciences. They are typically composed of weak acids and bases mixed in an aqueous solution, and can interact electrostatically with charged surfaces such as biomembranes. Buffers can induce protein aggregation and structural modification of soft interfaces, but a molecular-level picture is still lacking. Here we use high-resolution atomic force microscopy to investigate the effect of five commonly used buffers, namely 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES), 2-(N-morpholino)ethanesulfonic acid (MES), monosodium phosphate, saline sodium citrate (SSC) and tris(hydroxymethyl)aminomethane (Tris) on the hydration landscape of Muscovite mica in solution. Mica is an ideal model substrate due to its negative surface charge and identical lattice parameter when compared with gel-phase lipid bilayers. We show that buffer molecules can produce cohesive aggregates spanning over tens of nanometres of the interface. SSC, Tris and monosodium phosphate tend to create an amorphous mesh layer several molecules thick and with no preferential ordering. In contrast, MES and HEPES adopt epitaxial arrangements commensurate with the underlying mica lattice, suggesting that they offer the most suitable solution for high-resolution studies. To confirm that this effect persisted in biologically-relevant interfaces, the experiments were repeated on a silica-supported lipid bilayer. Similar trends were observed for this system using atomic force microscopy as well as ellipsometry. The effect of the buffering agents can be mitigated by the inclusion of salt which helps displace them from the interface.

  11. Soft, Embodied, Situated & Connected: enriching interactions with soft wearables

    DEFF Research Database (Denmark)

    Tomico, Oscar; Wilde, Danielle

    2016-01-01

    Soft wearables include clothing and textile-based accessories that incorporate smart textiles and soft electronic interfaces to enable responsive and interactive experiences. When designed well, soft wearables leverage the cultural, sociological and material qualities of textiles, fashion and dress...... approaches impact use. Finally, we reflect on how embodied and collocated interactions might extend understanding of how to frame wearables research and development to arrive at rich interactions that are soft, embodied, situated and connected....

  12. Gas hydrate of Lake Baikal: Discovery and varieties

    Science.gov (United States)

    Khlystov, Oleg; De Batist, Marc; Shoji, Hitoshi; Hachikubo, Akihiro; Nishio, Shinya; Naudts, Lieven; Poort, Jeffrey; Khabuev, Andrey; Belousov, Oleg; Manakov, Andrey; Kalmychkov, Gennаdy

    2013-01-01

    This paper summarizes the results of recent gas-hydrate studies in Lake Baikal, the only fresh-water lake in the world containing gas hydrates in its sedimentary infill. We provide a historical overview of the different investigations and discoveries and highlight some recent breakthroughs in our understanding of the Baikal hydrate system. So far, 21 sites of gas hydrate occurrence have been discovered. Gas hydrates are of structures I and II, which are of thermogenic, microbial, and mixed origin. At the 15 sites, gas hydrates were found in mud volcanoes, and the rest six - near gas discharges. Additionally, depending on type of discharge and gas hydrate structure, they were visually different. Investigations using MIR submersibles allowed finding of gas hydrates at the bottom surface of Lake Baikal at the three sites.

  13. Coral contact dermatitis

    OpenAIRE

    Jefferson, Julie; Thompson, Curtis; Hinshaw, Molly; Rich, Phoebe

    2015-01-01

    Corals can elicit both toxic and allergic reactions upon contact with the skin. Clinical presentations vary depending on whether the reaction is acute, delayed, or chronic. Literature concerning cutaneous reactions to corals and other Cnidarians is scarce. Herein we report a case of delayed contact hypersensitivity reaction to coral and review the clinical and histopathological features of coral contact dermatitis.

  14. Coral contact dermatitis.

    Science.gov (United States)

    Jefferson, Julie; Thompson, Curtis; Hinshaw, Molly; Rich, Phoebe

    2015-04-16

    Corals can elicit both toxic and allergic reactions upon contact with the skin. Clinical presentations vary depending on whether the reaction is acute, delayed, or chronic. Literature concerning cutaneous reactions to corals and other Cnidarians is scarce. Herein we report a case of delayed contact hypersensitivity reaction to coral and review the clinical and histopathological features of coral contact dermatitis.

  15. Contact urticaria : Present scenario

    Directory of Open Access Journals (Sweden)

    Bhatia Ruchi

    2009-01-01

    Full Text Available Immunological contact urticaria is a hypersensitivity reaction that appears on the skin following contact with an eliciting substance. Recent advances in our understanding of the molecular mechanism and pathogenesis of this reaction have altered its classification, diagnosis, and treatment. We discuss classification, epidemiology, diagnosis, testing, and treatment options that are available to patients with contact urticaria.

  16. Types of Contact Lenses

    Science.gov (United States)

    ... back to top ] Rigid Gas Permeable (RGP) Contact Lenses Rigid gas permeable contact lenses (RGPs) are more durable ... Ortho-K) Orthokeratology, or Ortho-K, is a lens fitting procedure that uses specially designed rigid gas permeable (RGP) contact lenses to change the ...

  17. Mixed lubricated line contacts

    OpenAIRE

    Faraon, Irinel Cosmin

    2005-01-01

    The present work deals with friction in mixed lubricated line contacts. Components in systems are becoming smaller and due to, for instance power transmitted, partial contact may occur. In industrial applications, friction between the moving contacting surfaces cannot be avoided, therefore it is essential that an engineer is able to predict friction.

  18. New Cosmetic Contact Allergens

    Directory of Open Access Journals (Sweden)

    An Goossens

    2015-02-01

    Full Text Available Allergic and photo-allergic contact dermatitis, and immunologic contact urticaria are potential immune-mediated adverse effects from cosmetics. Fragrance components and preservatives are certainly the most frequently observed allergens; however, all ingredients must be considered when investigating for contact allergy.

  19. The Soft Palate Friendly Speech Bulb for Velopharyngeal Insufficiency

    Science.gov (United States)

    Kahlon, Monaliza; Gupta, Shilpa; Dhingra, Parvinder Singh

    2016-01-01

    Velopharyngeal insufficiency is an anatomic defect of the soft palate making palatopharyngeal sphincter incomplete. It is an important concern to address in patients with bilateral cleft lip and palate. Speech aid prosthesis or speech bulbs are best choice in cases where surgically repaired soft palate is too short to contact pharyngeal walls during function but these prosthesis have been associated with inadequate marginal closure, ulcerations and patient discomfort. Here is a case report of untreated bilateral cleft lip and palate associated with palatal insufficiency treated by means of palate friendly innovative speech bulb. This modified speech bulb is a combination of hard acrylic and soft lining material. The hard self-curing acrylic resin covers only the hard palate area and a permanent soft silicone lining material covering the soft palate area. A claw-shaped wire component was extended backwards from acrylic and was embedded in soft silicone to aid in retention and approximation of two materials. The advantage of adding the soft lining material in posterior area helped in covering the adequate superior extension and margins for maximal pharyngeal activity. This also improved the hypernasality, speech, comfort and overall patient acceptance. PMID:27790589

  20. Nanobiotechnology: soft lithography.

    Science.gov (United States)

    Mele, Elisa; Pisignano, Dario

    2009-01-01

    An entirely new scientific and technological area has been born from the combination of nanotechnology and biology: nanobiotechnology. Such a field is primed especially by the strong potential synergy enabled by the integration of technologies, protocols, and investigation methods, since, while biomolecules represent functional nanosystems interesting for nanotechnology, micro- and nano-devices can be very useful instruments for studying biological materials. In particular, the research of new approaches for manipulating matter and fabricating structures with micrometre- and sub-micrometre resolution has determined the development of soft lithography, a new set of non-photolithographic patterning techniques applied to the realization of selective proteins and cells attachment, microfluidic circuits for protein and DNA chips, and 3D scaffolds for tissue engineering. Today, soft lithographies have become an asset of nanobiotechnology. This Chapter examines the biological applications of various soft lithographic techniques, with particular attention to the main general features of soft lithography and of materials commonly employed with these methods. We present approaches particularly suitable for biological materials, such as microcontact printing (muCP) and microfluidic lithography, and some key micro- and nanobiotechnology applications, such as the patterning of protein and DNA microarrays and the realization of microfluidic-based analytical devices.

  1. Optomechanical soft metamaterials

    Science.gov (United States)

    Peng, Xiangjun; He, Wei; Liu, Yifan; Xin, Fengxian; Lu, Tian Jian

    2017-06-01

    We present a new type of optomechanical soft metamaterials, which is different from conventional mechanical metamaterials, in that they are simple isotropic and homogenous materials without resorting to any complex nano/microstructures. This metamaterial is unique in the sense that its responses to uniaxial forcing can be tailored by programmed laser inputs to manifest different nonlinear constitutive behaviors, such as monotonic, S-shape, plateau, and non-monotonic snapping performance. To demonstrate the novel metamaterial, a thin sheet of soft material impinged by two counterpropagating lasers along its thickness direction and stretched by an in-plane tensile mechanical force is considered. A theoretical model is formulated to characterize the resulting optomechanical behavior of the thin sheet by combining the nonlinear elasticity theory of soft materials and the optical radiation stress theory. The optical radiation stresses predicted by the proposed model are validated by simulations based on the method of finite elements. Programmed optomechanical behaviors are subsequently explored using the validated model under different initial sheet thicknesses and different optical inputs, and the first- and second-order tangential stiffness of the metamaterial are used to plot the phase diagram of its nonlinear constitutive behaviors. The proposed optomechanical soft metamaterial shows great potential in biological medicine, microfluidic manipulation, and other fields.

  2. Soft condensed matter

    NARCIS (Netherlands)

    Frenkel, D.

    2002-01-01

    These lectures illustrate some of the concepts of soft-condensed matter physics, taking examples from colloid physics. Many of the theoretical concepts will be illustrated with the results of computer simulations. After a brief introduction describing interactions between colloids, the paper focuses

  3. On Soft Biometrics

    DEFF Research Database (Denmark)

    Nixon, Mark; Correia, Paulo; Nasrollahi, Kamal

    2015-01-01

    Innovation has formed much of the rich history in biometrics. The field of soft biometrics was originally aimed to augment the recognition process by fusion of metrics that were sufficient to discriminate populations rather than individuals. This was later refined to use measures that could be used...

  4. Evaluating six soft approaches

    DEFF Research Database (Denmark)

    Sørensen, Lene; Vidal, Rene Victor Valqui

    2006-01-01

    The paper introduces and evaluates six soft approaches used in strategy development and planning. We take a planner’s perspective on discussing the concepts of strategy development and planning. This means that we see strategy development and planning as learning processes based on Ackoff’s inter...

  5. Hard and Soft Governance

    DEFF Research Database (Denmark)

    Moos, Lejf

    2009-01-01

    The governance and leadership at transnational, national and school level seem to be converging into a number of isomorphic forms as we see a tendency towards substituting 'hard' forms of governance, that are legally binding, with 'soft' forms based on persuasion and advice. This article analyses...

  6. Soft Tissue Extramedullary Plasmacytoma

    Directory of Open Access Journals (Sweden)

    Fernando Ruiz Santiago

    2010-01-01

    Full Text Available We present the uncommon case of a subcutaneous fascia-based extramedullary plasmacytoma in the leg, which was confirmed by the pathology report and followed up until its remission. We report the differential diagnosis with other more common soft tissue masses. Imaging findings are nonspecific but are important to determine the tumour extension and to plan the biopsy.

  7. Soft Matter Characterization

    CERN Document Server

    Borsali, Redouane

    2008-01-01

    Progress in basic soft matter research is driven largely by the experimental techniques available. Much of the work is concerned with understanding them at the microscopic level, especially at the nanometer length scales that give soft matter studies a wide overlap with nanotechnology. This 2 volume reference work, split into 4 parts, presents detailed discussions of many of the major techniques commonly used as well as some of those in current development for studying and manipulating soft matter. The articles are intended to be accessible to the interdisciplinary audience (at the graduate student level and above) that is or will be engaged in soft matter studies or those in other disciplines who wish to view some of the research methods in this fascinating field. Part 1 contains articles with a largely (but, in most cases, not exclusively) theoretical content and/or that cover material relevant to more than one of the techniques covered in subsequent volumes. It includes an introductory chapter on some of t...

  8. Soft matrices on soft multisets in an optimal decision process

    Science.gov (United States)

    Coskun, Arzu Erdem; Aras, Cigdem Gunduz; Cakalli, Huseyin; Sonmez, Ayse

    2016-08-01

    In this paper, we introduce a concept of a soft matrix on a soft multiset, and investigate how to use soft matrices to solve decision making problems. An algorithm for a multiple choose selection problem is also provided. Finally, we demonstrate an illustrative example to show the decision making steps.

  9. Molecular properties of aqueous solutions: a focus on the collective dynamics of hydration water.

    Science.gov (United States)

    Comez, L; Paolantoni, M; Sassi, P; Corezzi, S; Morresi, A; Fioretto, D

    2016-07-07

    When a solute is dissolved in water, their mutual interactions determine the molecular properties of the solute on one hand, and the structure and dynamics of the surrounding water particles (the so-called hydration water) on the other. The very existence of soft matter and its peculiar properties are largely due to the wide variety of possible water-solute interactions. In this context, water is not an inert medium but rather an active component, and hydration water plays a crucial role in determining the structure, stability, dynamics, and function of matter. This review focuses on the collective dynamics of hydration water in terms of retardation with respect to the bulk, and of the number of molecules whose dynamics is perturbed. Since water environments are in a dynamic equilibrium, with molecules continuously exchanging from around the solute towards the bulk and vice versa, we examine the ability of different techniques to measure the water dynamics on the basis of the explored time scales and exchange rates. Special emphasis is given to the collective dynamics probed by extended depolarized light scattering and we discuss whether and to what extent the results obtained in aqueous solutions of small molecules can be extrapolated to the case of large biomacromolecules. In fact, recent experiments performed on solutions of increasing complexity clearly indicate that a reductionist approach is not adequate to describe their collective dynamics. We conclude this review by presenting current ideas that are being developed to describe the dynamics of water interacting with macromolecules.

  10. Impact of Wheat Bran Hydration Properties As Affected by Toasting and Degree of Milling on Optimal Dough Development in Bread Making.

    Science.gov (United States)

    Jacobs, Pieter J; Bogaerts, Silke; Hemdane, Sami; Delcour, Jan A; Courtin, Christophe M

    2016-05-11

    The impact of the hydration capacity and hydration rate of wheat bran on optimal bread dough development and loaf volume was investigated using coarse bran, both native as well as after toasting, milling, presoaking, and combinations of the latter. It was found that toasting reduces bran's hydration rate, which, during mixing, results in a temporary excess of water in which dough development takes place inefficiently and hence requires additional time. This mechanism was further substantiated by the observation that delayed dough development can be counteracted by the presoaking of bran. Milling of bran increases its hydration rate and results in faster optimal dough development. Presoaking of nonmilled bran, however, did not result in faster dough development. Smaller bran particles do lead to faster dough development, probably due to increased proper contacts between flour particles. Optimal loaf volumes did not change upon milling and toasting.

  11. Soft X-ray Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Seely, John

    1999-05-20

    The contents of this report cover the following: (1) design of the soft x-ray telescope; (2) fabrication and characterization of the soft x-ray telescope; and (3) experimental implementation at the OMEGA laser facility.

  12. Soft Decision Analyzer and Method

    Science.gov (United States)

    Steele, Glen F. (Inventor); Lansdowne, Chatwin (Inventor); Zucha, Joan P. (Inventor); Schlesinger, Adam M. (Inventor)

    2016-01-01

    A soft decision analyzer system is operable to interconnect soft decision communication equipment and analyze the operation thereof to detect symbol wise alignment between a test data stream and a reference data stream in a variety of operating conditions.

  13. Hydrate bearing clayey sediments: Formation and gas production concepts

    KAUST Repository

    Jang, Jaewon

    2016-06-20

    Hydro-thermo-chemo and mechanically coupled processes determine hydrate morphology and control gas production from hydrate-bearing sediments. Force balance, together with mass and energy conservation analyses anchored in published data provide robust asymptotic solutions that reflect governing processes in hydrate systems. Results demonstrate that hydrate segregation in clayey sediments results in a two-material system whereby hydrate lenses are surrounded by hydrate-free water-saturated clay. Hydrate saturation can reach ≈2% by concentrating the excess dissolved gas in the pore water and ≈20% from metabolizable carbon. Higher hydrate saturations are often found in natural sediments and imply methane transport by advection or diffusion processes. Hydrate dissociation is a strongly endothermic event; the available latent heat in a reservoir can sustain significant hydrate dissociation without triggering ice formation during depressurization. The volume of hydrate expands 2-to-4 times upon dissociation or CO2single bondCH4 replacement. Volume expansion can be controlled to maintain lenses open and to create new open mode discontinuities that favor gas recovery. Pore size is the most critical sediment parameter for hydrate formation and gas recovery and is controlled by the smallest grains in a sediment. Therefore any characterization must carefully consider the amount of fines and their associated mineralogy.

  14. Quantitative and simultaneous non-invasive measurement of skin hydration and sebum levels

    Science.gov (United States)

    Ezerskaia, Anna; Pereira, S. F.; Urbach, H. Paul; Verhagen, Rieko; Varghese, Babu

    2016-01-01

    We report a method on quantitative and simultaneous non-contact in-vivo hydration and sebum measurements of the skin using an infrared optical spectroscopic set-up. The method utilizes differential detection with three wavelengths 1720, 1750, and 1770 nm, corresponding to the lipid vibrational bands that lay “in between” the prominent water absorption bands. We have used an emulsifier containing hydro- and lipophilic components to mix water and sebum in various volume fractions which was applied to the skin to mimic different oily-dry skin conditions. We also measured the skin sebum and hydration values on the forehead under natural conditions and its variations to external stimuli. Good agreement was found between our experimental results and reference values measured using conventional biophysical methods such as Corneometer and Sebumeter. PMID:27375946

  15. Hole-doping of mechanically exfoliated graphene by confined hydration layers

    Institute of Scientific and Technical Information of China (English)

    Tjeerd R. J. Bollmann[1,2; Liubov Yu. Antipina[3,4; Matthias Temmen[2; Michael Reichling[2; Pavel B. Sorokin[5

    2015-01-01

    By the use of non-contact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM), we measure the local surface potential of mechanically exfoliated graphene on the prototypical insulating hydrophilic substrate of CAF2(111). Hydration layers confined between the graphene and the CaF2 substrate, resulting from the graphene's preparation under ambient conditions on the hydrophilic substrate surface, are found to electronically modify the graphene as the material's electron density transfers from graphene to the hydration layer. Density functional theory (DFT) calculations predict that the first 2 to 3 water layers adjacent to the graphene hole-dope the graphene by several percent of a unit charge per unit cell.

  16. Modeling Thermal Contact Resistance

    Science.gov (United States)

    Kittel, Peter; Sperans, Joel (Technical Monitor)

    1994-01-01

    One difficulty in using cryocoolers is making good thermal contact between the cooler and the instrument being cooled. The connection is often made through a bolted joint. The temperature drop associated with this joint has been the subject of many experimental and theoretical studies. The low temperature behavior of dry joints have shown some anomalous dependence on the surface condition of the mating parts. There is also some doubts on how well one can extrapolate from the test samples to predicting the performance of a real system. Both finite element and analytic models of a simple contact system have been developed. The model assumes (a) the contact is dry (contact limited to a small portion of the total available area and the spaces in-between the actual contact patches are perfect insulators), (b) contacts are clean (conductivity of the actual contact is the same as the bulk), (c) small temperature gradients (the bulk conductance may be assumed to be temperature independent), (d) the absolute temperature is low (thermal radiation effects are ignored), and (e) the dimensions of the nominal contact area are small compared to the thickness of the bulk material (the contact effects are localized near the contact). The models show that in the limit of actual contact area much less than the nominal area (a much less than A), that the excess temperature drop due to a single point of contact scales as a(exp -1/2). This disturbance only extends a distance approx. A(exp 1/2) into the bulk material. A group of identical contacts will result in an excess temperature drop that scales as n(exp -1/2), where n is the number of contacts and n dot a is constant. This implies that flat rough surfaces will have a lower excess temperature drop than flat polished surfaces.

  17. Possibility Intuitionistic Fuzzy Soft Set

    Directory of Open Access Journals (Sweden)

    Maruah Bashir

    2012-01-01

    Full Text Available Possibility intuitionistic fuzzy soft set and its operations are introduced, and a few of their properties are studied. An application of possibility intuitionistic fuzzy soft sets in decision making is investigated. A similarity measure of two possibility intuitionistic fuzzy soft sets has been discussed. An application of this similarity measure in medical diagnosis has been shown.

  18. Foam drilling in natural gas hydrate

    Directory of Open Access Journals (Sweden)

    Wei Na

    2015-01-01

    Full Text Available The key problem of foam drilling in natural gas hydrate is prediction of characteristic parameters of bottom hole. The simulation shows that when the well depth increases, the foam mass number reduces and the pressure increases. At the same depth, pressure in drill string is always higher than annulus. The research findings provide theoretical basis for safety control.

  19. Alkali binding in hydrated Portland cement paste

    NARCIS (Netherlands)

    Chen, W.; Brouwers, H.J.H.

    2010-01-01

    The alkali-binding capacity of C–S–H in hydrated Portland cement pastes is addressed in this study. The amount of bound alkalis in C–S–H is computed based on the alkali partition theories firstly proposed by Taylor (1987) and later further developed by Brouwers and Van Eijk (2003). Experimental data

  20. A positron annihilation study of hydrated DNA

    DEFF Research Database (Denmark)

    Warman, J. M.; Eldrup, Morten Mostgaard

    1986-01-01

    Positron annihilation measurements are reported for hydrated DNA as a function of water content and as a function of temperature (20 to -180.degree. C) for samples containing 10 and 50% wt of water. The ortho-positronium mean lifetime and its intensity show distinct variations with the degree...

  1. Hydration of protein–RNA recognition sites

    Science.gov (United States)

    Barik, Amita; Bahadur, Ranjit Prasad

    2014-01-01

    We investigate the role of water molecules in 89 protein–RNA complexes taken from the Protein Data Bank. Those with tRNA and single-stranded RNA are less hydrated than with duplex or ribosomal proteins. Protein–RNA interfaces are hydrated less than protein–DNA interfaces, but more than protein–protein interfaces. Majority of the waters at protein–RNA interfaces makes multiple H-bonds; however, a fraction do not make any. Those making H-bonds have preferences for the polar groups of RNA than its partner protein. The spatial distribution of waters makes interfaces with ribosomal proteins and single-stranded RNA relatively ‘dry’ than interfaces with tRNA and duplex RNA. In contrast to protein–DNA interfaces, mainly due to the presence of the 2′OH, the ribose in protein–RNA interfaces is hydrated more than the phosphate or the bases. The minor groove in protein–RNA interfaces is hydrated more than the major groove, while in protein–DNA interfaces it is reverse. The strands make the highest number of water-mediated H-bonds per unit interface area followed by the helices and the non-regular structures. The preserved waters at protein–RNA interfaces make higher number of H-bonds than the other waters. Preserved waters contribute toward the affinity in protein–RNA recognition and should be carefully treated while engineering protein–RNA interfaces. PMID:25114050

  2. Obsidian Hydration Dating in the Undergraduate Curriculum.

    Science.gov (United States)

    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)

  3. Obsidian Hydration Dating in the Undergraduate Curriculum.

    Science.gov (United States)

    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)

  4. [Terminal phase hydration, pain and delirium

    DEFF Research Database (Denmark)

    Heick, A.

    2009-01-01

    Hydration of the terminal patient may relieve confusion and complaints of "dry mouth". But it may worsen oedema of the brain, lungs, and extremities, worsen terminal rattling and cause a need for frequent changing of diapers. The decision of whether and how to treat a dying patient with fluids...

  5. Acoustic Determination of Methane Hydrate Disssociation Pressures

    Science.gov (United States)

    2011-07-01

    centered- cubic orientation which forms naturally in deep oceans from biogenic gases. It is worth not- ing that this molecular geometry can trap great...until January 2010. At that time, the hydrates were packed in a dewar with liquid nitrogen and shipped from the storage fa- cility at the Naval Research

  6. Hydration of Acetylene: A 125th Anniversary

    Science.gov (United States)

    Ponomarev, Dmitry A.; Shevchenko, Sergey M.

    2007-01-01

    The year 2006 is the 125th anniversary of a chemical reaction, the discovery of which by Mikhail Kucherov had a profound effect on the development of industrial chemistry in the 19-20th centuries. This was the hydration of alkynes catalyzed by mercury ions that made possible industrial production of acetaldehyde from acetylene. Historical…

  7. Hydration dynamics near a model protein surface

    Energy Technology Data Exchange (ETDEWEB)

    Russo, Daniela; Hura, Greg; Head-Gordon, Teresa

    2003-09-01

    The evolution of water dynamics from dilute to very high concentration solutions of a prototypical hydrophobic amino acid with its polar backbone, N-acetyl-leucine-methylamide (NALMA), is studied by quasi-elastic neutron scattering and molecular dynamics simulation for both the completely deuterated and completely hydrogenated leucine monomer. We observe several unexpected features in the dynamics of these biological solutions under ambient conditions. The NALMA dynamics shows evidence of de Gennes narrowing, an indication of coherent long timescale structural relaxation dynamics. The translational water dynamics are analyzed in a first approximation with a jump diffusion model. At the highest solute concentrations, the hydration water dynamics is significantly suppressed and characterized by a long residential time and a slow diffusion coefficient. The analysis of the more dilute concentration solutions takes into account the results of the 2.0M solution as a model of the first hydration shell. Subtracting the first hydration layer based on the 2.0M spectra, the translational diffusion dynamics is still suppressed, although the rotational relaxation time and residential time are converged to bulk-water values. Molecular dynamics analysis shows spatially heterogeneous dynamics at high concentration that becomes homogeneous at more dilute concentrations. We discuss the hydration dynamics results of this model protein system in the context of glassy systems, protein function, and protein-protein interfaces.

  8. Gas hydrates distribution in the Shenhu area, northern South China Sea: comparisons between the eight drilling sites with gashydrate petroleum system

    Energy Technology Data Exchange (ETDEWEB)

    Su, M.; Yang, R.; Wang, H.; Sha, Z.; Liang, J.; Wu, N.; Qiao, S.; Cong, X.

    2016-07-01

    The results of the first marine gas hydrate drilling expedition of Guangzhou Marine Geological Survey (GMGS-1) in northern continental slope of the South China Sea revealed a variable distribution of gas hydrates in the Shenhu area. In this study, comparisons between the eight sites with gas-hydrate petroleum system were used to analyze and re-examine hydrate potential. In the Shenhu gas hydrate drilling area, all the sites were located in a suitable low-temperature, high-pressure environment. Biogenic and thermogenic gases contributed to the formation of hydrates. Gas chimneys and some small-scale faults (or micro-scale fractures) compose the migration pathways for gas-bearing fluids. Between these sites, there are three key differences: the seafloor temperatures and pressures; geothermal gradient and sedimentary conditions. Variations of seafloor temperatures and pressures related to water depths and geothermal gradient would lead to changes in the thickness of gas hydrate stability zones. Although the lithology and grain size of the sediments were similar, two distinct sedimentary units were identified for the first time through seismic interpretation, analysis of deep-water sedimentary processes, and the Cm pattern (plotted one-percentile and median values from grain-size analyses), implying the heterogeneous sedimentary conditions above Bottom Simulating Reflectors (BSRs). Based on the analyses of forming mechanisms and sedimentary processes, these two fine-grained sedimentary units have different physical properties. Fine-grained turbidites (Unit I) with thin-bedded chaotic reflectors at the bottom acted as the host rocks for hydrates; whereas, finegrained sediments related to soft-sediment deformation (Unit II) characterized by thick continuous reflectors at the top would serve as regional homogeneous caprocks. Low-flux methane that migrated upwards along chimneys could be enriched preferentially in fine-grained turbidites, resulting in the formation of

  9. Biofilm formation of Achromobacter xylosoxidans on contact lens.

    Science.gov (United States)

    Konstantinović, Neda; Ćirković, Ivana; Đukić, Slobodanka; Marić, Vesna; Božić, Dragana D

    2017-02-20

    Achromobacter spp. may contaminate lenses, lens cases, and contact lens solutions and cause ocular infections. The aim of this study was to investigate the possibility of isolated strain of Achromobacter xylosoxidans to form biofilm on the surface of soft contact lenses (CL), to quantify the production of the formed biofilm, and compare it with the reference strains (Pseudomonas aeruginosa, Staphylococcus aureus, and Haemophilus influenzae). Bacterial strain isolated from one contact lens case was identified as A. xylosoxidans using Vitek2 Automated System. Biofilm forming capacity of isolated strain of A. xylosoxidans and reference strains of P. aeruginosa, S. aureus, and H. influenzae on soft CL were analyzed by commonly used microtitre plate method. Our results showed that isolated strain of A. xylosoxidans was capable to form biofilm on the surface of soft contact lens. A. xylosoxidans was strong biofilm producer while all examined reference strains were moderate biofilm producers. A. xylosoxidans appears to be superior biofilm producer on soft CL compared to reference strains.

  10. Anaerobic oxidation of methane above gas hydrates at Hydrate Ridge, NE Pacific Ocean

    DEFF Research Database (Denmark)

    Treude, T.; Boetius, A.; Knittel, K.;

    2003-01-01

    At Hydrate Ridge (HR), Cascadia convergent margin, surface sediments contain massive gas hydrates formed from methane that ascends together with fluids along faults from deeper reservoirs. Anaerobic oxidation of methane (AOM), mediated by a microbial consortium of archaea and sulfate-reducing...... bacteria, generates high concentrations of hydrogen sulfide in the surface sediments. The production of sulfide supports chemosynthetic communities that gain energy from sulfide oxidation. Depending on fluid flow, the surface communities are dominated either by the filamentous sulfur bacteria Beggiatoa...

  11. Modeling DNA hydration: comparison of calculated and experimental hydration properties of nuclic acid bases.

    Science.gov (United States)

    Poltev, V I; Malenkov, G G; Gonzalez, E J; Teplukhin, A V; Rein, R; Shibata, M; Miller, J H

    1996-02-01

    Hydration properties of individual nucleic acid bases were calculated and compared with the available experimental data. Three sets of classical potential functions (PF) used in simulations of nucleic acid hydration were juxtaposed: (i) the PF developed by Poltev and Malenkov (PM), (ii) the PF of Weiner and Kollman (WK), which together with Jorgensen's TIP3P water model are widely used in the AMBER program, and (iii) OPLS (optimized potentials for liquid simulations) developed by Jorgensen (J). The global minima of interaction energy of single water molecules with all the natural nucleic acid bases correspond to the formation of two water-base hydrogen bonds (water bridging of two hydrophilic atoms of the base). The energy values of these minima calculated via PM potentials are in somewhat better conformity with mass-spectrometric data than the values calculated via WK PF. OPLS gave much weaker water-base interactions for all compounds considered, thus these PF were not used in further computations. Monte Carlo simulations of the hydration of 9-methyladenine, 1-methyluracil and 1-methylthymine were performed in systems with 400 water molecules and periodic boundary conditions. Results of simulations with PM potentials give better agreement with experimental data on hydration energies than WK PF. Computations with PM PF of the hydration energy of keto and enol tautomers of 9-methylguanine can account for the shift in the tautomeric equilibrium of guanine in aqueous media to a dominance of the keto form in spite of nearly equal intrinsic stability of keto and enol tautomers. The results of guanine hydration computations are discussed in relation to mechanisms of base mispairing errors in nucleic acid biosynthesis. The data presented in this paper along with previous results on simulation of hydration shell structures in DNA duplex grooves provide ample evidence for the advantages of PM PF in studies of nucleic-acid hydration.

  12. Contact printed masks for 3D microfabrication in negative resists

    DEFF Research Database (Denmark)

    Häfliger, Daniel; Boisen, Anja

    2005-01-01

    We present a process based on contact printed shadow masks for three dimensional microfabrication of soft and sensitive overhanging membranes in SU-8. A metal mask is transferred onto unexposed SU-8 from an elastomer stamp made of polydimethylsiloxane. This mask is subsequently embedded into the ......We present a process based on contact printed shadow masks for three dimensional microfabrication of soft and sensitive overhanging membranes in SU-8. A metal mask is transferred onto unexposed SU-8 from an elastomer stamp made of polydimethylsiloxane. This mask is subsequently embedded...... into the negative resist to protect buried material from UV-exposure. Unlike direct evaporation-deposition of a mask onto the SU-8, printing avoids high stress and radiation, thus preventing resist wrinkling and prepolymerization. We demonstrate effective monolithic fabrication of soft, 4-μm thick and 100-μm long...

  13. Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates.

    Science.gov (United States)

    Krishnan, N M Anoop; Wang, Bu; Falzone, Gabriel; Le Pape, Yann; Neithalath, Narayanan; Pilon, Laurent; Bauchy, Mathieu; Sant, Gaurav

    2016-12-28

    Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development, and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C-S-H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C-S-H shows a sudden increase when the CaO/SiO2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C-S-H's nanostructure. We identify that confinement is dictated by the topology of the C-S-H's atomic network. Taken together, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.

  14. General Information about Childhood Soft Tissue Sarcoma

    Science.gov (United States)

    ... forms in soft tissues of the body, including muscle, tendons, fat, blood vessels, lymph vessels, nerves, and tissue around joints. Soft tissue sarcoma occurs in children and adults. Soft ... disorders can increase the risk of childhood soft tissue sarcoma. Anything ...

  15. Stages of Childhood Soft Tissue Sarcoma

    Science.gov (United States)

    ... forms in soft tissues of the body, including muscle, tendons, fat, blood vessels, lymph vessels, nerves, and tissue around joints. Soft tissue sarcoma occurs in children and adults. Soft ... disorders can increase the risk of childhood soft tissue sarcoma. Anything ...

  16. Treatment Options for Childhood Soft Tissue Sarcoma

    Science.gov (United States)

    ... forms in soft tissues of the body, including muscle, tendons, fat, blood vessels, lymph vessels, nerves, and tissue around joints. Soft tissue sarcoma occurs in children and adults. Soft ... disorders can increase the risk of childhood soft tissue sarcoma. Anything ...

  17. Treatment Option Overview (Childhood Soft Tissue Sarcoma)

    Science.gov (United States)

    ... forms in soft tissues of the body, including muscle, tendons, fat, blood vessels, lymph vessels, nerves, and tissue around joints. Soft tissue sarcoma occurs in children and adults. Soft ... disorders can increase the risk of childhood soft tissue sarcoma. Anything ...

  18. Direct measurement of methane hydrate composition along the hydrate equilibrium boundary

    Science.gov (United States)

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

    2005-01-01

    The composition of methane hydrate, namely nW for CH 4??nWH2O, was directly measured along the hydrate equilibrium boundary under conditions of excess methane gas. Pressure and temperature conditions ranged from 1.9 to 9.7 MPa and 263 to 285 K. Within experimental error, there is no change in hydrate composition with increasing pressure along the equilibrium boundary, but nW may show a slight systematic decrease away from this boundary. A hydrate stoichiometry of n W = 5.81-6.10 H2O describes the entire range of measured values, with an average composition of CH4??5.99(??0.07) H2O along the equilibrium boundary. These results, consistent with previously measured values, are discussed with respect to the widely ranging values obtained by thermodynamic analysis. The relatively constant composition of methane hydrate over the geologically relevant pressure and temperature range investigated suggests that in situ methane hydrate compositions may be estimated with some confidence. ?? 2005 American Chemical Society.

  19. Clathrate Hydrates for Thermal Energy Storage in Buildings: Overview of Proper Hydrate-Forming Compounds

    Directory of Open Access Journals (Sweden)

    Beatrice Castellani

    2014-09-01

    Full Text Available Increasing energy costs are at the origin of the great progress in the field of phase change materials (PCMs. The present work aims at studying the application of clathrate hydrates as PCMs in buildings. Clathrate hydrates are crystalline structures in which guest molecules are enclosed in the crystal lattice of water molecules. Clathrate hydrates can form also at ambient pressure and present a high latent heat, and for this reason, they are good candidates for being used as PCMs. The parameter that makes a PCM suitable to be used in buildings is, first of all, a melting temperature at about 25 °C. The paper provides an overview of groups of clathrate hydrates, whose physical and chemical characteristics could meet the requirements needed for their application in buildings. Simulations with a dynamic building simulation tool are carried out to evaluate the performance of clathrate hydrates in enhancing thermal comfort through the moderation of summer temperature swings and, therefore, in reducing energy consumption. Simulations suggest that clathrate hydrates have a potential in terms of improvement of indoor thermal comfort and a reduction of energy consumption for cooling. Cooling effects of 0.5 °C and reduced overheating hours of up to 1.1% are predicted.

  20. MORPHOLOGY OF METHANE HYDRATE HOST SEDIMENTS.

    Energy Technology Data Exchange (ETDEWEB)

    JONES,K.W.; FENG,H.; TOMOV,S.; WINTER,W.J.; EATON,M.; MAHAJAN,D.

    2004-12-01

    Results from simulated experiments in several laboratories show that host sediments influence hydrate formation in accord with known heterogeneity of host sediments at sites of gas hydrate occurrence (1). For example, in Mackenzie Delta, NWT Canada (Mallik 2L-38 well), coarser-grained units (pore-filling model) are found whereas in the Gulf of Mexico, the found hydrate samples do not appear to be lithologically controlled. We have initiated a systematic study of sediments, initially focusing on samples from various depths at a specific site, to establish a correlation with hydrate occurrence (or variations thereof) to establish differences in their microstructure, porosity, and other associated properties. The synchrotron computed microtomography (CMT) set-up at the X-27A tomography beam line at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory was used as a tool to study sediments from Blake Ridge at three sub bottom depths of 0.2, 50, and 667 meters. Results from the tomographic analysis of the deepest sample (667 m) are presented here to illustrate how tomography can be used to obtain new insights into the structures of methane hydrate host sediments. The investigation shows the internal grain/pore space resolution in the microstructure and a 3-D visualization of the connecting pathways obtained following data segmentation into pore space and grains within the sediment sample. The analysis gives the sample porosity, specific surface area, mean particle size, and tortuosity, as well. An earlier report on the experimental program has been given by Mahajan et al. (2).

  1. China's Research on Non-conventional Energy Resources- Gas Hydrate

    Institute of Scientific and Technical Information of China (English)

    Pu Ming; Ma Jianguo

    2002-01-01

    @@ Methane exists in ice-like formations called gas hydrate. Hydrate traps methane molecules inside a cage of frozen water. The magnitude of this previously unknown global storehouse of methane is truly staggering and has raised serious inquiry into the possibility of using methane hydrate as a substitute source of energy for oil and conventional natural gas. According to the estimation by PGC, gas hydrate deposits amount to 7.6 × 1018m3 and contain more than twice as much organic carbon as all the world's coal, oil and non-hydrate natural gas combined.

  2. Soft-Collinear Supersymmetry

    CERN Document Server

    Cohen, Timothy; Larkoski, Andrew J

    2016-01-01

    Soft-Collinear Effective Theory (SCET) is a framework for modeling the infrared structure of theories whose long distance behavior is dominated by soft and collinear divergences. This paper demonstrates that SCET can be made compatible with supersymmetry (SUSY). Explicitly, the effective theory for $\\mathcal{N} = 1$ SUSY Yang-Mills is constructed and shown to be consistent. For contrast, arguments are given that chiral SUSY theories with Yukawa couplings, specifically the single flavor Wess-Zumino model, are incompatible with the collinear expansion. SCET is formulated by expanding fields along a light-like direction and then subsequently integrating out degrees-of-freedom that are away from the light-cone. Defining the theory with respect to a specific frame obfuscates Lorentz invariance -- given that SUSY is a space-time symmetry, this presents a possible obstruction. The cleanest language with which to expose the congruence between SUSY and SCET requires exploring two novel formalisms: collinear fermions a...

  3. Biological Soft Robotics.

    Science.gov (United States)

    Feinberg, Adam W

    2015-01-01

    In nature, nanometer-scale molecular motors are used to generate force within cells for diverse processes from transcription and transport to muscle contraction. This adaptability and scalability across wide temporal, spatial, and force regimes have spurred the development of biological soft robotic systems that seek to mimic and extend these capabilities. This review describes how molecular motors are hierarchically organized into larger-scale structures in order to provide a basic understanding of how these systems work in nature and the complexity and functionality we hope to replicate in biological soft robotics. These span the subcellular scale to macroscale, and this article focuses on the integration of biological components with synthetic materials, coupled with bioinspired robotic design. Key examples include nanoscale molecular motor-powered actuators, microscale bacteria-controlled devices, and macroscale muscle-powered robots that grasp, walk, and swim. Finally, the current challenges and future opportunities in the field are addressed.

  4. Genital soft tissue tumors.

    Science.gov (United States)

    Schoolmeester, John K; Fritchie, Karen J

    2015-07-01

    Mesenchymal neoplasms of the vulvovaginal and inguinoscrotal regions are among the most diagnostically challenging specimens in the pathology laboratory owing largely to their unique intersection between general soft tissue tumors and relatively genital-specific mesenchymal tumors. Genital stromal tumors are a unique subset of soft tissue tumors encountered at this location, and this group includes fibroepithelial stromal polyp, superficial (cervicovaginal) myofibroblastoma, cellular angiofibroma, mammary-type myofibroblastoma, angiomyofibroblastoma and aggressive angiomyxoma. Aside from the striking morphologic and immunophenotypic similarity that is seen with these entities, there is evidence that a subset of genital stromal tumors may be linked genetically. This review will focus on simplifying this group of tumors and provide the pathologist or dermatopathologist with practical management information. Smooth muscle tumors of the external genitalia will also be discussed.

  5. Interaction of Drops on a Soft Substrate

    Science.gov (United States)

    Lubbers, Luuk A.; Weijs, Joost H.; Das, Siddhartha; Botto, Lorenzo; Andreotti, Bruno; Snoeijer, Jacco H.

    2013-11-01

    A sessile drop can elastically deform a substrate by the action of capillary forces. The typical size of the deformation is given by the ratio of surface tension and the elastic modulus, γ / E , which can reach up to 10-100 microns for soft elastomers. In this talk we theoretically show that the contact angles of drops on such a surface exhibit two transitions when increasing γ / E : (i) the microsocopic geometry of the contact line first develops a Neumann-like cusp when γ / E is of the order of few nanometers, (ii) the macroscopic angle of the drop is altered only when γ / E reaches the size of the drop. Using the same framework we then show that two neighboring drops exhibit an effective interaction, mediated by the deformation of the elastic medium. This is in analogy to the well-known Cheerios effect, where small particles at a liquid interface attract eachother due to the meniscus deformations. Here we reveal the nature of drop-drop interactions on a soft substrate by combining numerical and analytical calculations.

  6. Hypoelastic Soft Tissues

    Science.gov (United States)

    Freed, Alan D.; Einstein, Daniel R.; Sacks, Michael S.

    2010-01-01

    In Part I, a novel hypoelastic framework for soft-tissues was presented. One of the hallmarks of this new theory is that the well-known exponential behavior of soft-tissues arises consistently and spontaneously from the integration of a rate based formulation. In Part II, we examine the application of this framework to the problem of biaxial kinematics, which are common in experimental soft-tissue characterization. We confine our attention to an isotropic formulation in order to highlight the distinction between non-linearity and anisotropy. In order to provide a sound foundation for the membrane extension of our earlier hypoelastic framework, the kinematics and kinetics of in-plane biaxial extension are revisited, and some enhancements are provided. Specifically, the conventional stress-to-traction mapping for this boundary value problem is shown to violate the conservation of angular momentum. In response, we provide a corrected mapping. In addition, a novel means for applying loads to in-plane biaxial experiments is proposed. An isotropic, isochoric, hypoelastic, constitutive model is applied to an in-plane biaxial experiment done on glutaraldehyde treated bovine pericardium. The experiment is comprised of eight protocols that radially probe the biaxial plane. Considering its simplicity (two adjustable parameters) the model does a reasonably good job of describing the non-linear normal responses observed in these experimental data, which are more prevalent than are the anisotropic responses exhibited by this tissue. PMID:21394222

  7. Some Results on Fuzzy Soft Topological Spaces

    Directory of Open Access Journals (Sweden)

    Cigdem Gunduz (Aras

    2013-01-01

    Full Text Available We introduce some important properties of fuzzy soft topological spaces. Furthermore, fuzzy soft continuous mapping, fuzzy soft open and fuzzy soft closed mappings, and fuzzy soft homeomorphism for fuzzy soft topological spaces are given and structural characteristics are discussed and studied.

  8. Indian National Gas Hydrate Program Expedition 01 report

    Science.gov (United States)

    Collett, Timothy S.; Riedel, M.; Boswell, R.; Presley, J.; Kumar, P.; Sathe, A.; Sethi, A.; Lall, M.; ,

    2015-01-01

    Gas hydrate is a naturally occurring “ice-like” combination of natural gas and water that has the potential to serve as an immense resource of natural gas from the world’s oceans and polar regions. However, gas-hydrate recovery is both a scientific and a technical challenge and much remains to be learned about the geologic, engineering, and economic factors controlling the ultimate energy resource potential of gas hydrate. The amount of natural gas contained in the world’s gas-hydrate accumulations is enormous, but these estimates are speculative and range over three orders of magnitude from about 2,800 to 8,000,000 trillion cubic meters of gas. By comparison, conventional natural gas accumulations (reserves and undiscovered, technically recoverable resources) for the world are estimated at approximately 440 trillion cubic meters. Gas recovery from gas hydrate is hindered because the gas is in a solid form and because gas hydrate commonly occurs in remote Arctic and deep marine environments. Proposed methods of gas recovery from gas hydrate generally deal with disassociating or “melting” in situ gas hydrate by heating the reservoir beyond the temperature of gas-hydrate formation, or decreasing the reservoir pressure below hydrate equilibrium. The pace of energy-related gas hydrate assessment projects has accelerated over the past several years.

  9. Solid state interconversion between anhydrous norfloxacin and its hydrates.

    Science.gov (United States)

    Chongcharoen, Wanchai; Byrn, Stephen R; Sutanthavibul, Narueporn

    2008-01-01

    This work is focused on characterizing and evaluating the solid state interconversion of norfloxacin (NF) hydrates. Four stoichiometric NF hydrates, dihydrate, hemipentahydrate, trihydrate, pentahydrate and a disordered NF state, were generated by various methods and characterized by X-ray powder diffractometry (XRPD), thermal analysis and Karl Fisher titrimetry. XRPD patterns of all NF hydrates exhibited crystalline structures. NF hydrate conversion was studied with respect to mild elevated temperature and various degrees of moisture levels. NF hydrates transformed to anhydrous NF Form A after gentle heating at 60 degrees C for 48 h except dihydrate and trihydrate where mixture in XRPD patterns between anhydrous NF Form A and former structures existed. Desiccation of NF hydrates at 0% RH for 7 days resulted in only partial removal of water molecules from the hydrated structures. The hydrated transitional phase and the disordered NF state were obtained from the incomplete dehydration of NF hydrates after thermal treatment and pentahydrate NF after desiccation, respectively. Anhydrous NF Form A and NF hydrates transformed to pentahydrate NF when exposed to high moisture environment except dihydrate. In conclusion, surrounding moisture levels, temperatures and the duration of exposure strongly influenced the interconversion pathways and stoichiometry of anhydrous NF and its hydrates. (c) 2007 Wiley-Liss, Inc.

  10. When Coke Is Not Hydrating

    Directory of Open Access Journals (Sweden)

    Mohammed Bahaa Aldeen MD

    2014-09-01

    Full Text Available A 47-year-old African American man was admitted with 4 days of back pain, nausea and vomiting, and low urine output. There was no history of fever, dysuria, frequency, hesitancy, viral symptoms, trauma, rash, or constipation. Despite his past medical history of hypertension, diabetes mellitus, and hyperlipidemia he denied taking any medications for 18 months, including nonsteroidal anti-inflammatory drugs, acetaminophen, or antacids. He denied smoking and alcohol but admitted to cocaine use. No significant FH. Physical examination results were as follows: BP 235/125 mm Hg, heart rate 90 beats/min, temperature 98°F, O2 saturation normal; lungs and heart normal, abdomen soft but bilateral costovertebral angle tenderness. Neurological examination was normal. Laboratory tests yielded the following results: creatinine (Cr 10.5 mg/dL (1.2 mg/dL in 2010, blood urea nitrogen 63 mg/dL, glucose 151 mg/dL, Ca 9.4 mg/dL, PO4 6.1 mg/dL, Hgb 15 g/dL, white blood cells (WBC 9100, platelets 167 000, amylase/lipase normal, aspartate aminotransferase/alanine aminotransferase (AST/ALT normal, bilirubin 1.4 mg/dL, alkaline phosphatase 39 IU/L, creatine phosphokinase 127 µg/L. Hepatic panel, C- and P-ANCA (cytoplasmic– and perinuclear–antineutrophil cytoplasm antibodies, respectively, anti-GBM (anti–glomerular basement membrane, antimyeloperoxidase, antinuclear antibody, and Helicobacter pylori were all negative. C3, C4 normal, urinalysis: 2+ blood, no white blood cells or eosinophils, no casts, no albumin, negative for nitrate/leukocyte esterase and bacteria. Imaging: chest radiograph, abdominal radiograph, computed tomography of the abdomen, electrocardiography, and transthoracic echocardiography were all normal. Course. The patient’s urine output declined from 700 to 400 cm3/d and the on third day he required hemodialysis with Cr 14 mg/dL. Renal biopsy showed typical findings of interstitial nephritis. The patient was dialyzed for 10 days and responded

  11. Characterization of un-hydrated and hydrated BioAggregate™ and MTA Angelus™.

    Science.gov (United States)

    Camilleri, J; Sorrentino, F; Damidot, D

    2015-04-01

    BioAggregate™ is a novel material introduced for use as a root-end filling material. It is tricalcium silicate-based, free of aluminium and uses tantalum oxide as radiopacifier. BioAggregate contains additives to enhance the material performance. The purpose of this research was to characterize the un-hydrated and hydrated forms of BioAggregate using a combination of techniques, verify whether the additives if present affect the properties of the set material and compare these properties to those of MTA Angelus™. Un-hydrated and hydrated BioAggregate and MTA Angelus were assessed. Un-hydrated cement was tested for chemical composition, specific surface area, mineralogy and kinetics of hydration. The set material was investigated for mineralogy, microstructure and bioactivity. Scanning electron microscopy, X-ray energy dispersive spectroscopic analysis, X-ray fluorescence spectroscopy, X-ray diffraction and isothermal calorimetry were employed. The specific surface area was investigated using a gas adsorption method with nitrogen as the probe. BioAggregate was composed of tricalcium silicate, tantalum oxide, calcium phosphate and silicon dioxide and was free of aluminium. On hydration, the tricalcium silicate produced calcium silicate hydrate and calcium hydroxide. The former was deposited around the cement grains, while the latter reacted with the silicon dioxide to form additional calcium silicate hydrate. This resulted in reduction of calcium hydroxide in the aged cement. MTA Angelus reacted in a similar fashion; however, since it contained no additives, the calcium hydroxide was still present in the aged cement. Bioactivity was demonstrated by deposition of hydroxyapatite. BioAggregate exhibited a high specific surface area. Nevertheless, the reactivity determined by isothermal calorimetry appeared to be slow compared to MTA Angelus. The tantalum oxide as opposed to bismuth oxide was inert, and tantalum was not leached in solution. BioAggregate exhibited

  12. Natural Gas Evolution in a Gas Hydrate Melt: Effect of Thermodynamic Hydrate Inhibitors.

    Science.gov (United States)

    Sujith, K S; Ramachandran, C N

    2017-01-12

    Natural gas extraction from gas hydrate sediments by injection of hydrate inhibitors involves the decomposition of hydrates. The evolution of dissolved gas from the hydrate melt is an important step in the extraction process. Using classical molecular dynamics simulations, we study the evolution of dissolved methane from its hydrate melt in the presence of two thermodynamic hydrate inhibitors, NaCl and CH3OH. An increase in the concentration of hydrate inhibitors is found to promote the nucleation of methane nanobubbles in the hydrate melt. Whereas NaCl promotes bubble formation by enhancing the hydrophobic interaction between aqueous CH4 molecules, CH3OH molecules assist bubble formation by stabilizing CH4 bubble nuclei formed in the solution. The CH3OH molecules accumulate around the nuclei leading to a decrease in the surface tension at their interface with water. The nanobubbles formed are found to be highly dynamic with frequent exchange of CH4 molecules between the bubble and the surrounding liquid. A quantitative analysis of the dynamic behavior of the bubble is performed by introducing a unit step function whose value depends on the location of CH4 molecules with respect to the bubble. It is observed that an increase in the concentration of thermodynamic hydrate inhibitors reduces the exchange process, making the bubble less dynamic. It is also found that for a given concentration of the inhibitor, larger bubbles are less dynamic compared to smaller ones. The dependence of the dynamic nature of nanobubbles on bubble size and inhibitor concentration is correlated with the solubility of CH4 and the Laplace pressure within the bubble. The effect of CO2 on the formation of nanobubble in the CH4-CO2 mixed gas hydrate melt in the presence of inhibitors is also examined. The simulations show that the presence of CO2 molecules significantly reduces the induction time for methane nanobubble nucleation. The role of CO2 in the early nucleation of bubble is explained

  13. Towards a green hydrate inhibitor: imaging antifreeze proteins on clathrates.

    Directory of Open Access Journals (Sweden)

    Raimond Gordienko

    Full Text Available The formation of hydrate plugs in oil and gas pipelines is a serious industrial problem and recently there has been an increased interest in the use of alternative hydrate inhibitors as substitutes for thermodynamic inhibitors like methanol. We show here that antifreeze proteins (AFPs possess the ability to modify structure II (sII tetrahydrofuran (THF hydrate crystal morphologies by adhering to the hydrate surface and inhibiting growth in a similar fashion to the kinetic inhibitor poly-N-vinylpyrrolidone (PVP. The effects of AFPs on the formation and growth rate of high-pressure sII gas mix hydrate demonstrated that AFPs are superior hydrate inhibitors compared to PVP. These results indicate that AFPs may be suitable for the study of new inhibitor systems and represent an important step towards the development of biologically-based hydrate inhibitors.

  14. Water retention curve for hydrate-bearing sediments

    Science.gov (United States)

    Dai, Sheng; Santamarina, J. Carlos

    2013-11-01

    water retention curve plays a central role in numerical algorithms that model hydrate dissociation in sediments. The determination of the water retention curve for hydrate-bearing sediments faces experimental difficulties, and most studies assume constant water retention curves regardless of hydrate saturation. This study employs network model simulation to investigate the water retention curve for hydrate-bearing sediments. Results show that (1) hydrate in pores shifts the curve to higher capillary pressures and the air entry pressure increases as a power function of hydrate saturation; (2) the air entry pressure is lower in sediments with patchy rather than distributed hydrate, with higher pore size variation and pore connectivity or with lower specimen slenderness along the flow direction; and (3) smaller specimens render higher variance in computed water retention curves, especially at high water saturation Sw > 0.7. Results are relevant to other sediment pore processes such as bioclogging and mineral precipitation.

  15. Contact angle hysteresis explained.

    Science.gov (United States)

    Gao, Lichao; McCarthy, Thomas J

    2006-07-04

    A view of contact angle hysteresis from the perspectives of the three-phase contact line and of the kinetics of contact line motion is given. Arguments are made that advancing and receding are discrete events that have different activation energies. That hysteresis can be quantified as an activation energy by the changes in interfacial area is argued. That this is an appropriate way of viewing hysteresis is demonstrated with examples.

  16. Introduction to contact mechanics

    CERN Document Server

    Fischer-Cripps, Anthony C

    2000-01-01

    Contact mechanics deals with the elastic or plastic contact between two solid objects, and is thus intimately connected with such topics as fracture, hardness, and elasticity.This text, intended for advanced undergraduates, begins with an introduction to the mechanical properties of materials, general fracture mechanics, and fractures in brittle solids.This is followed by a detailed discussion of stresses and the nature of elastic and elastic-plastic contact.

  17. Forces Between a Permanent Magnet and a Soft Magnetic Plate

    DEFF Research Database (Denmark)

    Beleggia, Marco; Vokoun, David; De Graef, Marc

    2012-01-01

    Forces between a hard/permanent magnet of arbitrary shape and an ideally soft magnetic plate in close proximity are derived analytically from the image method applied to magnetostatics. We found that the contact force, defined as the force required to detach the hard magnet from the plate......, coincides with that between two identical touching permanent magnets. Furthermore, if the hard and the soft magnets are displaced by some amount, their attraction equals that between two identical permanent magnets displaced by twice that amount. Experimental results are presented that validate...

  18. Allergic Contact Dermatitis

    Directory of Open Access Journals (Sweden)

    Meltem Önder

    2009-03-01

    Full Text Available Allergic contact dermatitis is the delayed type hypersensitivity reaction to exogenous agents. Allergic contact dermatitis may clinically present acutely after allergen exposure and initial sensitization in a previously sensitized individual. Acute phase is characterized by erythematous, scaly plaques. In severe cases vesiculation and bullae in exposed areas are very characteristic. Repeated or continuous exposure of sensitized individual with allergen result in chronic dermatitis. Lichenification, erythematous plaques, hyperkeratosis and fissuring may develop in chronic patients. Allergic contact dermatitis is very common dermatologic problem in dermatology daily practice. A diagnosis of contact dermatitis requires the careful consideration of patient history, physical examination and patch testing. The knowledge of the clinical features of the skin reactions to various contactans is important to make a correct diagnosis of contact dermatitis. It can be seen in every age, in children textile product, accessories and touch products are common allergens, while in adults allergic contact dermatitis may be related with topical medicaments. The contact pattern of contact dermatitis depends on fashion and local traditions as well. The localization of allergic reaction should be evaluated and patients’ occupation and hobbies should be asked. The purpose of this review is to introduce to our collaques up dated allergic contact dermatitis literatures both in Turkey and in the World.

  19. Contact Quality in Participation

    DEFF Research Database (Denmark)

    Simonsen, Jesper; Jensen, Olav Storm

    2016-01-01

    We investigate the concept of participation from the perspective of quality of the contact in the communicative interactions between participants. We argue for the need for an academic-personal competence that qualifies the human contact central in all Participatory Design (PD) activities as a way...... to contribute to “an era of participation.” We describe a contact perspective in PD developed through a collaboration with body-oriented psychotherapeutic research that have specialized experiences in investigating open-minded contact and authentic meetings as body-related experiences....

  20. Colors and contact dermatitis.

    Science.gov (United States)

    Bonamonte, Domenico; Foti, Caterina; Romita, Paolo; Vestita, Michelangelo; Angelini, Gianni

    2014-01-01

    The diagnosis of skin diseases relies on several clinical signs, among which color is of paramount importance. In this review, we consider certain clinical presentations of both eczematous and noneczematous contact dermatitis in which color plays a peculiar role orientating toward the right diagnosis. The conditions that will be discussed include specific clinical-morphologic subtypes of eczematous contact dermatitis, primary melanocytic, and nonmelanocytic contact hyperchromia, black dermographism, contact chemical leukoderma, and others. Based on the physical, chemical, and biologic factors underlying a healthy skin color, the various skin shades drawing a disease picture are thoroughly debated, stressing their etiopathogenic origins and histopathologic aspects.