Atomic Scale Imaging of Nucleation and Growth Trajectories of an Interfacial Bismuth Nanodroplet.

Science.gov (United States)

Li, Yingxuan; Bunes, Benjamin R; Zang, Ling; Zhao, Jie; Li, Yan; Zhu, Yunqing; Wang, Chuanyi

2016-02-23

Because of the lack of experimental evidence, much confusion still exists on the nucleation and growth dynamics of a nanostructure, particularly of metal. The situation is even worse for nanodroplets because it is more difficult to induce the formation of a nanodroplet while imaging the dynamic process with atomic resolution. Here, taking advantage of an electron beam to induce the growth of Bi nanodroplets on a SrBi2Ta2O9 platelet under a high resolution transmission electron microscope (HRTEM), we directly observed the detailed growth pathways of Bi nanodroplets from the earliest stage of nucleation that were previously inaccessible. Atomic scale imaging reveals that the dynamics of nucleation involves a much more complex trajectory than previously predicted based on classical nucleation theory (CNT). The monatomic Bi layer was first formed in the nucleation process, which induced the formation of the prenucleated clusters. Following that, critical nuclei for the nanodroplets formed both directly from the addition of atoms to the prenucleated clusters by the classical growth process and indirectly through transformation of an intermediate liquid film based on the Stranski-Krastanov growth mode, in which the liquid film was induced by the self-assembly of the prenucleated clusters. Finally, the growth of the Bi nanodroplets advanced through the classical pathway and sudden droplet coalescence. This study allows us to visualize the critical steps in the nucleation process of an interfacial nanodroplet, which suggests a revision of the perspective of CNT.

Docetaxel-loaded multilayer nanoparticles with nanodroplets for cancer therapy

Directory of Open Access Journals (Sweden)

Oh KS

2016-03-01

Full Text Available Keun Sang Oh,1,* Kyungim Kim,1,* Byeong Deok Yoon,1 Hye Jin Lee,1 Dal Yong Park,1 Eun-yeong Kim,1 Kiho Lee,1 Jae Hong Seo,2 Soon Hong Yuk1,2 1College of Pharmacy, Korea University, Sejong, 2Biomedical Research Center, Korea University Guro Hospital, Guro-gu, Seoul, Republic of Korea *These authors contributed equally to this work Abstract: A mixture of docetaxel (DTX and Solutol® HS 15 (Solutol transiently formed nanodroplets when it was suspended in an aqueous medium. However, nanodroplets that comprised DTX and Solutol showed a rapid precipitation of DTX because of their unstable characteristics in the aqueous medium. The incorporation of nanodroplets that comprised DTX and Solutol through vesicle fusion and subsequent stabilization was designed to prepare multilayer nanoparticles (NPs with a DTX-loaded Solutol nanodroplet (as template NPs core for an efficient delivery of DTX as a chemotherapeutic drug. As a result, the DTX-loaded Solutol nanodroplets (~11.7 nm were observed to have an increased average diameter (from 11.7 nm to 156.1 nm and a good stability of the hydrated NPs without precipitation of DTX by vesicle fusion and multilayered structure, respectively. Also, a long circulation of the multilayer NPs was observed, and this was due to the presence of Pluronic F-68 on the surface of the multilayer NPs. This led to an improved antitumor efficacy based on the enhanced permeation and retention effect. Therefore, this study indicated that the multilayer NPs have a considerable potential as a drug delivery system with an enhanced therapeutic efficacy by blood circulation and with low side effects. Keywords: multilayer nanoparticles, Solutol, Pluronic F-68, docetaxel, cancer therapy

Crystallization in nano-confinement seeded by a nanocrystal—A molecular dynamics study

KAUST Repository

Pan, Heng; Grigoropoulos, Costas

2014-01-01

Seeded crystallization and solidification in nanoscale confinement volumes have become an important and complex topic. Due to the complexity and limitations in observing nanoscale crystallization, computer simulation can provide valuable details for supporting and interpreting experimental observations. In this article, seeded crystallization from nano-confined liquid, as represented by the crystallization of a suspended gold nano-droplet seeded by a pre-existing gold nanocrystal seed, was investigated using molecular dynamics simulations in canonical (NVT) ensemble. We found that the crystallization temperature depends on nano-confinement volume, crystal orientation, and seed size as explained by classical two-sphere model and Gibbs-Thomson effect. © 2014 AIP Publishing LLC.

Crystallization in nano-confinement seeded by a nanocrystal—A molecular dynamics study

KAUST Repository

Pan, Heng

2014-03-14

Seeded crystallization and solidification in nanoscale confinement volumes have become an important and complex topic. Due to the complexity and limitations in observing nanoscale crystallization, computer simulation can provide valuable details for supporting and interpreting experimental observations. In this article, seeded crystallization from nano-confined liquid, as represented by the crystallization of a suspended gold nano-droplet seeded by a pre-existing gold nanocrystal seed, was investigated using molecular dynamics simulations in canonical (NVT) ensemble. We found that the crystallization temperature depends on nano-confinement volume, crystal orientation, and seed size as explained by classical two-sphere model and Gibbs-Thomson effect. © 2014 AIP Publishing LLC.

Ejection of solvated ions from electrosprayed methanol/water nanodroplets studied by molecular dynamics simulations.

Science.gov (United States)

Ahadi, Elias; Konermann, Lars

2011-06-22

The ejection of solvated small ions from nanometer-sized droplets plays a central role during electrospray ionization (ESI). Molecular dynamics (MD) simulations can provide insights into the nanodroplet behavior. Earlier MD studies have largely focused on aqueous systems, whereas most practical ESI applications involve the use of organic cosolvents. We conduct simulations on mixed water/methanol droplets that carry excess NH(4)(+) ions. Methanol is found to compromise the H-bonding network, resulting in greatly increased rates of ion ejection and solvent evaporation. Considerable differences in the water and methanol escape rates cause time-dependent changes in droplet composition. Segregation occurs at low methanol concentration, such that layered droplets with a methanol-enriched periphery are formed. This phenomenon will enhance the partitioning of analyte molecules, with possible implications for their ESI efficiencies. Solvated ions are ejected from the tip of surface protrusions. Solvent bridging prior to ion secession is more extensive for methanol/water droplets than for purely aqueous systems. The ejection of solvated NH(4)(+) is visualized as diffusion-mediated escape from a metastable basin. The process involves thermally activated crossing of a ~30 kJ mol(-1) free energy barrier, in close agreement with the predictions of the classical ion evaporation model.

Novel ultrasound-responsive chitosan/perfluorohexane nanodroplets for image-guided smart delivery of an anticancer agent: Curcumin.

Science.gov (United States)

Baghbani, Fatemeh; Chegeni, Mahdieh; Moztarzadeh, Fathollah; Hadian-Ghazvini, Samaneh; Raz, Majid

2017-05-01

Ultrasound-responsive nanodroplets are a class of new emerging smart drug delivery systems which provide image-guided nano-therapy of various diseases, especially cancers. Here, we developed multifunctional smart curcumin-loaded chitosan/perfluorohexane nanodroplets for contrast-ultrasound imaging and on-demand drug delivery. The nanodroplets were synthesized via nanoemulsion process. The optimal formulation with the size of 101.2nm and 77.8% curcumin entrapment was chosen for release study and cytotoxicity evaluation. Sonication at the frequency of 1MHz, 2W/cm 2 for 4min triggered the release of 63.5% of curcumin from optimal formulation (Cur-NDs-2). Ultrasound aided release study indicated that the concentration of perfluorohexane and the degree of acoustic droplet vaporization play important role in ultrasound-active drug release. B-mode ultrasound imaging confirmed strong ultrasound contrast of chitosan nanodroplets even at low concentrations via droplet to bubble transition. Finally, cytotoxicity of the ultrasound-responsive nanodroplets in the presence of ultrasound was evaluated in-vitro on 4T1 human breast cancer cells. Cell growth inhibitory effects of curcumin-loaded nanodroplets significantly increased by ultrasound exposure. According to the obtained results, these ultrasound responsive curcumin-loaded chitosan/perfluorohexane nanodroplets have a great potential for imaged-guided cancer therapy. Copyright © 2016 Elsevier B.V. All rights reserved.

The Soft-Confined Method for Creating Molecular Models of Amorphous Polymer Surfaces

KAUST Repository

Liu, Hongyi; Li, Yan; Krause, Wendy E.; Rojas, Orlando J.; Pasquinelli, Melissa A.

2012-01-01

The goal of this work was to use molecular dynamics (MD) simulations to build amorphous surface layers of polypropylene (PP) and cellulose and to inspect their physical and interfacial properties. A new method to produce molecular models for these surfaces was developed, which involved the use of a "soft" confining layer comprised of a xenon crystal. This method compacts the polymers into a density distribution and a degree of molecular surface roughness that corresponds well to experimental values. In addition, calculated properties such as density, cohesive energy density, coefficient of thermal expansion, and the surface energy agree with experimental values and thus validate the use of soft confining layers. The method can be applied to polymers with a linear backbone such as PP as well as those whose backbones contain rings, such as cellulose. The developed PP and cellulose surfaces were characterized by their interactions with water. It was found that a water nanodroplet spreads on the amorphous cellulose surfaces, but there was no significant change in the dimension of the droplet on the PP surface; the resulting MD water contact angles on PP and amorphous cellulose surfaces were determined to be 106 and 33°, respectively. © 2012 American Chemical Society.

The Soft-Confined Method for Creating Molecular Models of Amorphous Polymer Surfaces

KAUST Repository

Liu, Hongyi

2012-02-09

The goal of this work was to use molecular dynamics (MD) simulations to build amorphous surface layers of polypropylene (PP) and cellulose and to inspect their physical and interfacial properties. A new method to produce molecular models for these surfaces was developed, which involved the use of a "soft" confining layer comprised of a xenon crystal. This method compacts the polymers into a density distribution and a degree of molecular surface roughness that corresponds well to experimental values. In addition, calculated properties such as density, cohesive energy density, coefficient of thermal expansion, and the surface energy agree with experimental values and thus validate the use of soft confining layers. The method can be applied to polymers with a linear backbone such as PP as well as those whose backbones contain rings, such as cellulose. The developed PP and cellulose surfaces were characterized by their interactions with water. It was found that a water nanodroplet spreads on the amorphous cellulose surfaces, but there was no significant change in the dimension of the droplet on the PP surface; the resulting MD water contact angles on PP and amorphous cellulose surfaces were determined to be 106 and 33°, respectively. © 2012 American Chemical Society.

Dynamics of water confined in clay minerals

International Nuclear Information System (INIS)

Le Caer, S.; Pommeret, S.; Renault, J.Ph.; Lima, M.; Righini, R.; Gosset, D.; Simeone, D.; Bergaya, F.

2012-01-01

Ultrafast infrared spectroscopy of the O-D stretching mode of dilute HOD in H 2 O probes the local environment and the hydrogen bond network of confined water. The dynamics of water molecules confined in the interlayer space of montmorillonites (Mt) and in interaction with two types of cations (Li + and Ca 2+ ) but also with the negatively charged siloxane surface are studied. The results evidence that the OD vibrational dynamics is significantly slowed down in confined media: it goes from 1.7 ps in neat water to 2.6 Ps in the case of Li + cations with two water pseudo-layers (2.2-2.3 ps in the case of Ca 2+ cations) and to 4.7 ps in the case of Li + cations with one water pseudo-layer. No significant difference between the two cations is noticed. In this 2D confined geometry (the interlayer space being about 0.6 nm for two water pseudo-layers), the relaxation time constants obtained are comparable to the ones measured in analogous concentrated salt solutions. Nevertheless, and in strong opposition to the observations performed in the liquid phase, anisotropy experiments evidence the absence of rotational motions on a 5 ps time scale, proving that the hydrogen bond network in the interlayer space of the clay mineral is locked at this time scale. (authors)

Two-pulse driving of D+D nuclear fusion within a single Coulomb exploding nanodroplet

International Nuclear Information System (INIS)

Last, Isidore; Jortner, Joshua; Peano, Fabio; Silva, Luis O.

2010-01-01

This paper presents a computational study of D+D fusion driven by Coulomb explosion (CE) within a single, homonuclear deuterium nanodroplet, subjected to double-pulse ultraintense laser irradiation. This irradiation scheme results in the attainment (by the first weaker pulse) of a transient inhomogeneous density profile, which serves as a target for the driving (by the second superintense pulse) of nonuniform CE that triggers overrun effects and induces intrananodroplet (INTRA) D+D fusion. Scaled electron and ion dynamics simulations were utilized to explore the INTRA D+D fusion yields for double-pulse, near-infrared laser irradiation of deuterium nanodroplets. The dependence of the INTRA yield on the nanodroplet size and on the parameters of the two laser pulses was determined, establishing the conditions for the prevalence of efficient INTRA fusion. The INTRA fusion yields are amenable to experimental observation within an assembly of nanodroplets. The INTRA D+D fusion can be distinguished from the concurrent internanodroplet D+D fusion reaction occurring in the macroscopic plasma filament and outside it in terms of the different energies of the neutrons produced in these two channels.

The effect of the molecular mass on the sputtering by electrosprayed nanodroplets

Energy Technology Data Exchange (ETDEWEB)

Borrajo-Pelaez, Rafael; Gamero-Castaño, Manuel, E-mail: mgameroc@uci.edu

2015-07-30

Highlights: • We study the effect of the molecular mass on nanodroplet sputtering of silicon. • The impact phenomenology is a strong function of the projectile’s molecular mass. • Nanodroplet sputtering intrinsically is a molecular scale phenomenon. - Abstract: Energetic bombardment of covalently bonded materials by electrosprayed nanodroplets causes sputtering and topographic changes on the surface of the target. This work investigates the influence of the projectile's molecular mass on these phenomena by sputtering single-crystal silicon wafers with a variety of liquids (molecular masses between 45.0 and 773.3 amu), and acceleration voltages. The electrosprays are characterized via time of flight to determine the charge to mass ratio of the nanodroplets which, together with the acceleration voltage, yield the impact velocity, the stagnation pressure, and the molecular kinetic energy of the projectile. The estimated range of droplet diameters is 20–79 nm, while the impact velocity, the stagnation pressure and the molecular kinetic energy range between 2.9–10 km/s, 4.7–63 GPa, and 2.1–98 eV. We find that the damage on the surface of the targets strongly depends on the molecular mass of the projectile: liquids with low molecular mass sputter significantly less and produce nanometric indentations and low surface roughness, the latter increasing moderately with stagnation pressure; in contrast, the roughness and sputtering caused by the impacts of droplets with larger molecular mass reach significantly higher values, and exhibit non-monotonic behaviors. The maximum sputtering yields for formamide, EAN, EMI-BF{sub 4}, EMI-Im, TES, and TPP are 0.20, 0.75, 1.20, 2.80, 4.00 and 2.90 silicon atoms per molecule in the projectile. These trends indicate that despite their rather large diameters, the sputtering by electrosprayed nanodroplets is intrinsically a molecular scale phenomenon.

Efficient and controllable thermal ablation induced by short-pulsed HIFU sequence assisted with perfluorohexane nanodroplets.

Science.gov (United States)

Chang, Nan; Lu, Shukuan; Qin, Dui; Xu, Tianqi; Han, Meng; Wang, Supin; Wan, Mingxi

2018-07-01

A HIFU sequence with extremely short pulse duration and high pulse repetition frequency can achieve thermal ablation at a low acoustic power using inertial cavitation. Because of its cavitation-dependent property, the therapeutic outcome is unreliable when the treatment zone lacks cavitation nuclei. To overcome this intrinsic limitation, we introduced perfluorocarbon nanodroplets as extra cavitation nuclei into short-pulsed HIFU-mediated thermal ablation. Two types of nanodroplets were used with perfluorohexane (PFH) as the core material coated with bovine serum albumin (BSA) or an anionic fluorosurfactant (FS) to demonstrate the feasibility of this study. The thermal ablation process was recorded by high-speed photography. The inertial cavitation activity during the ablation was revealed by sonoluminescence (SL). The high-speed photography results show that the thermal ablation volume increased by ∼643% and 596% with BSA-PFH and FS-PFH, respectively, than the short-pulsed HIFU alone at an acoustic power of 19.5 W. Using nanodroplets, much larger ablation volumes were created even at a much lower acoustic power. Meanwhile, the treatment time for ablating a desired volume significantly reduced in the presence of nanodroplets. Moreover, by adjusting the treatment time, lesion migration towards the HIFU transducer could also be avoided. The SL results show that the thermal lesion shape was significantly dependent on the inertial cavitation in this short-pulsed HIFU-mediated thermal ablation. The inertial cavitation activity became more predictable by using nanodroplets. Therefore, the introduction of PFH nanodroplets as extra cavitation nuclei made the short-pulsed HIFU thermal ablation more efficient by increasing the ablation volume and speed, and more controllable by reducing the acoustic power and preventing lesion migration. Copyright © 2018. Published by Elsevier B.V.

Simulations of water nano-confined between corrugated planes

Science.gov (United States)

Zubeltzu, Jon; Artacho, Emilio

2017-11-01

Water confined to nanoscale widths in two dimensions between ideal planar walls has been the subject of ample study, aiming at understanding the intrinsic response of water to confinement, avoiding the consideration of the chemistry of actual confining materials. In this work, we study the response of such nanoconfined water to the imposition of a periodicity in the confinement by means of computer simulations, both using empirical potentials and from first-principles. For that we propose a periodic confining potential emulating the atomistic oscillation of the confining walls, which allows varying the lattice parameter and amplitude of the oscillation. We do it for a triangular lattice, with several values of the lattice parameter: one which is ideal for commensuration with layers of Ih ice and other values that would correspond to more realistic substrates. For the former, the phase diagram shows an overall rise of the melting temperature. The liquid maintains a bi-layer triangular structure, however, despite the fact that it is not favoured by the external periodicity. The first-principles liquid is significantly affected by the modulation in its layering and stacking even at relatively small amplitudes of the confinement modulation. Beyond some critical modulation amplitude, the hexatic phase present in flat confinement is replaced by a trilayer crystalline phase unlike any of the phases encountered for flat confinement. For more realistic lattice parameters, the liquid does not display higher tendency to freeze, but it clearly shows inhomogeneous behaviour as the strength of the rugosity increases. In spite of this expected inhomogeneity, the structural and dynamical response of the liquid is surprisingly insensitive to the external modulation. Although the first-principles calculations give a more triangular liquid than the one observed with empirical potentials (TIP4P/2005), both agree remarkably well for the main conclusions of the study.

Structural and mechanical properties of glassy water in nanoscale confinement.

Science.gov (United States)

Lombardo, Thomas G; Giovambattista, Nicolás; Debenedetti, Pablo G

2009-01-01

We investigate the structure and mechanical properties of glassy water confined between silica-based surfaces with continuously tunable hydrophobicity and hydrophilicity by computing and analyzing minimum energy, mechanically stable configurations (inherent structures). The structured silica substrate imposes long-range order on the first layer of water molecules under hydrophobic confinement at high density (p > or = 1.0 g cm(-3)). This proximal layer is also structured in hydrophilic confinement at very low density (p approximately 0.4 g cm(-3)). The ordering of water next to the hydrophobic surface greatly enhances the mechanical strength of thin films (0.8 nm). This leads to a substantial stress anisotropy; the transverse strength of the film exceeds the normal strength by 500 MPa. The large transverse strength results in a minimum in the equation of state of the energy landscape that does not correspond to a mechanical instability, but represents disruption of the ordered layer of water next to the wall. In addition, we find that the mode of mechanical failure is dependent on the type of confinement. Under large lateral strain, water confined by hydrophilic surfaces preferentially forms voids in the middle of the film and fails cohesively. In contrast, water under hydrophobic confinement tends to form voids near the walls and fails by loss of adhesion.

A Nanodroplet Processor for Advanced Microencapsulated Drug Formulations, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — The objective of this proposal is to provide a demonstration of a nanodroplet synthesis of multifunctional liposomes for drug delivery based on immiscible...

A Nanodroplet Processor for Advanced Microencapsulated Drug Formulations, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — During this Phase II program we propose to build on the key aspects of the nanodroplet encapsulation technology to demonstrate optimized formulation and...

Application of quasi-elastic neutron scattering to dynamics study of confined water

International Nuclear Information System (INIS)

Li Hua; Zhang Lili; Yi Zhou

2014-01-01

Background: Quasi-elastic neutron scattering (QENS) is an important experiment for dynamics study of confined water. It is significant to study the dynamics of confined water in cement paste. Purpose: In this paper, we have two aims. One is to present a reviewer of QENS study on dynamics of confined water in cement paste in recent years. The other is to illustrate the QENS application to the study on dynamics of confined water based on cement paste. Method: Relaxing cage model (RCM) is specially introduced for the analyses of QENS spectra. Results: Based on RCM, several parameters for describing the dynamics of confined water in cement paste, can be obtained from the analyses of QENS spectra: a fraction of mobile 'glassy' water molecules embedded in amorphous gel region surrounding the hydration products, 1-p, the capture time of confined water molecule in some place-τ 0 , the average translational relaxation time-<τ>, the self-diffusion coefficient-D, and a phenomenological shape parameter describing the uniform of amorphous in cement paste-β. Conclusion: All these provide a practical method for QENS study on dynamics of confined water in cement paste. (authors)

Slow Dynamics and Structure of Supercooled Water in Confinement

Directory of Open Access Journals (Sweden)

Gaia Camisasca

2017-04-01

Full Text Available We review our simulation results on properties of supercooled confined water. We consider two situations: water confined in a hydrophilic pore that mimics an MCM-41 environment and water at interface with a protein. The behavior upon cooling of the α relaxation of water in both environments is well interpreted in terms of the Mode Coupling Theory of glassy dynamics. Moreover, we find a crossover from a fragile to a strong regime. We relate this crossover to the crossing of the Widom line emanating from the liquid-liquid critical point, and in confinement we connect this crossover also to a crossover of the two body excess entropy of water upon cooling. Hydration water exhibits a second, distinctly slower relaxation caused by its dynamical coupling with the protein. The crossover upon cooling of this long relaxation is related to the protein dynamics.

IL 14: Radiolysis of water confined in nano-porous materials

International Nuclear Information System (INIS)

Renault, J.P.; Pommeret, S.; Musat, R.; Le Caer, S.; Alam, M.; Mialocq, J.C.

2010-01-01

Radiolysis of water in nano-porous media has raised a lot of interest and involved research in the recent years, with respect to concerns arising from the storage of nuclear waste. In the civil nuclear industry, storing for a long time nuclear wastes requires safety evaluations in order to test the durability of the materials involved. Among these materials, concrete and clays are a complex heterogeneous material that traps important quantities of interstitial water. Irradiation that arises from the nuclear wastes stored in these materials may lead to the radiolysis of the interstitial water, and the formation of radiolytic products, such as H 2 , O 2 or H 2 O 2 that may cause the breaking or the corrosion of the confining matrix. This communication will describe the possible impacts of confinement on the radiolysis of water. We will especially discuss the current knowledge about the evolution of radiolytic yields of primary species (hydroxyl radical, dihydrogen, aqueous electron) as a function of the degree of confinement and of the nature of the confining material. SEM picture of a nano-porous gold sample used to study the radiolysis of confined water The yield enhancement observed in many cases revealed original energy and charge transfer phenomena that we tried to decipher. (authors)

Unusual buffer action of free-standing nanoscopically confined water.

Science.gov (United States)

Liao, Kylin; Xu, Xiaozhou; Du, Xuezhong

2010-01-15

The acid-base properties of nanoscopic water confined in the black soap films (BSFs), which were prepared from aqueous solutions of sodium dodecylsulphate (SDS) with the dye neutral red (NR) as a pH probe, were investigated using a combination of UV-vis and FTIR spectroscopy. For the SDS micellar solutions at pH 1.0-9.5 adjusted with HCl/NaOH solutions and at pH 9.4 with ammonium buffered solution, the aqueous core thicknesses in the corresponding BSFs ranged from 2.7 to 6.2 nm, and the nanoscopically confined water exhibits unusual buffer action resistant not only to acidic/alkaline solutions but also to standard buffer solution. In the heavily water-depleted confined zones, it is most likely that charge pairs in proton-transfer reactions could not be formed effectively and proton transfer was prohibited in the absence of sufficient solvating ability. Theoretical analyzes indicated that the buffer action of the nanoscopic water originated from the confinement effect of two charged surfaces of the BSFs. These results might inspire deeper understanding and further studies of biobuffering, enzyme superactivity, acid-catalyzed reactions, and Nafion fuel cell membranes.

Targeted drug delivery with focused ultrasound-induced blood-brain barrier opening using acoustically-activated nanodroplets.

Science.gov (United States)

Chen, Cherry C; Sheeran, Paul S; Wu, Shih-Ying; Olumolade, Oluyemi O; Dayton, Paul A; Konofagou, Elisa E

2013-12-28

Focused ultrasound (FUS) in the presence of systemically administered microbubbles has been shown to locally, transiently and reversibly increase the permeability of the blood-brain barrier (BBB), thus allowing targeted delivery of therapeutic agents in the brain for the treatment of central nervous system diseases. Currently, microbubbles are the only agents that have been used to facilitate the FUS-induced BBB opening. However, they are constrained within the intravascular space due to their micron-size diameters, limiting the delivery effect at or near the microvessels. In the present study, acoustically-activated nanodroplets were used as a new class of contrast agents to mediate FUS-induced BBB opening in order to study the feasibility of utilizing these nanoscale phase-shift particles for targeted drug delivery in the brain. Significant dextran delivery was achieved in the mouse hippocampus using nanodroplets at clinically relevant pressures. Passive cavitation detection was used in the attempt to establish a correlation between the amount of dextran delivered in the brain and the acoustic emission recorded during sonication. Conventional microbubbles with the same lipid shell composition and perfluorobutane core as the nanodroplets were also used to compare the efficiency of an FUS-induced dextran delivery. It was found that nanodroplets had a higher BBB opening pressure threshold but a lower stable cavitation threshold than microbubbles, suggesting that contrast agent-dependent acoustic emission monitoring was needed. A more homogeneous dextran delivery within the targeted hippocampus was achieved using nanodroplets without inducing inertial cavitation or compromising safety. Our results offered a new means of developing the FUS-induced BBB opening technology for potential extravascular targeted drug delivery in the brain, extending the potential drug delivery region beyond the cerebral vasculature. © 2013.

Finite size effects on hydrogen bonds in confined water

International Nuclear Information System (INIS)

Musat, R.; Renault, J.P.; Le Caer, S.; Pommeret, S.; Candelaresi, M.; Palmer, D.J.; Righini, R.

2008-01-01

Femtosecond IR spectroscopy was used to study water confined in 1-50 nm pores. The results show that even large pores induce significant changes (for example excited-state lifetimes) to the hydrogen-bond network, which are independent of pore diameter between 1 and 50 nm. Thus, the changes are not surface-induced but rather finite size effects, and suggest a confinement-induced enhancement of the acidic character of water. (authors)

Structural and dynamical properties of water confined between two hydrophilic surfaces

Energy Technology Data Exchange (ETDEWEB)

Di Napoli, Solange, E-mail: dinapoli@tandar.cnea.gov.a [Depto. de Fisica - CAC, Comision Nacional de Energia Atomica, Av. Gral Paz 1499, (1650) San Martin, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina); Gamba, Zulema, E-mail: gamba@tandar.cnea.gov.a [Depto. de Fisica - CAC, Comision Nacional de Energia Atomica, Av. Gral Paz 1499, (1650) San Martin, Buenos Aires (Argentina)

2009-10-01

The properties of water in the vicinity of surfaces and under confinement have been extensively studied because of the relevance of a quantitative understanding of many processes that not only take place in biological systems, like cells, membranes and microemulsions, but also in many others such as confined water in rocks, ionic channels and interestellar matter. In this work we perform molecular dynamic calculations of the nanoscopic structure of TIP5P model water confined between two hydrophilic surfaces. We calculate the diffusion coefficients and the atomic density profile of water molecules and polar ions in the system as a function of the number of water molecules per amphiphilic (n{sub W}). We also study the dependence of the water layer thickness and the profiles of water dipole orientation with this parameter.

Structural and dynamical properties of water confined between two hydrophilic surfaces

International Nuclear Information System (INIS)

Di Napoli, Solange; Gamba, Zulema

2009-01-01

The properties of water in the vicinity of surfaces and under confinement have been extensively studied because of the relevance of a quantitative understanding of many processes that not only take place in biological systems, like cells, membranes and microemulsions, but also in many others such as confined water in rocks, ionic channels and interestellar matter. In this work we perform molecular dynamic calculations of the nanoscopic structure of TIP5P model water confined between two hydrophilic surfaces. We calculate the diffusion coefficients and the atomic density profile of water molecules and polar ions in the system as a function of the number of water molecules per amphiphilic (n W ). We also study the dependence of the water layer thickness and the profiles of water dipole orientation with this parameter.

Femtochemistry of confined water

Science.gov (United States)

Douhal, A.; Carranza, M. A.; Sanz, M.; Organero, J. A.; Santos, L.

In this contribution, we applied ultrafast spectroscopy to study the H-bond network of water confined in nanostructures (Cyclodextrins and Micelles). We examine the effect of caging on ultrafast reaction dynamics and discuss the related processes under different experimental conditions. The results show an ultrafast dynamic giving birth to intermediates of the probe, which show femtosecond and picosecond dynamics leading to the final structure at the excited state. The results show the high sensitivity of the used technique in detecting small of water. This work was supported by the Ministry of Science and Technology (MCYT, Spain) and ``Conserjería de Ciencia y Tecnologia de la JCCM, Spain'' through projects MAT2002-01829 and PAI-02-004.

Layering of confined water between two graphene sheets and its liquid–liquid transition

International Nuclear Information System (INIS)

Zhou Xuyan; Duan Yunrui; Wang Long; Liu Sida; Li Tao; Li Yifan; Li Hui

2017-01-01

Molecular dynamics (MD) simulations are performed to explore the layering structure and liquid–liquid transition of liquid water confined between two graphene sheets with a varied distance at different pressures. Both the size of nanoslit and pressure could cause the layering and liquid–liquid transition of the confined water. With increase of pressure and the nanoslit’s size, the confined water could have a more obvious layering. In addition, the neighboring water molecules firstly form chain structure, then will transform into square structure, and finally become triangle with increase of pressure. These results throw light on layering and liquid–liquid transition of water confined between two graphene sheets. (paper)

Impulsive Laser Induced Alignment of Molecules Dissolved in Helium Nanodroplets

DEFF Research Database (Denmark)

Pentlehner, Dominik; H. Nielsen, Jens; Slenczka, Alkwin

2013-01-01

We show that a 450 fs nonresonant, moderately intense, linearly polarized laser pulse can induce field-free molecular axis alignment of methyliodide (CH3I) molecules dissolved in a helium nanodroplet. Time-resolved measurements reveal rotational dynamics much slower than that of isolated molecules...

Structure and dynamics of water confined in a graphene nanochannel under gigapascal high pressure: dependence of friction on pressure and confinement.

Science.gov (United States)

Yang, Lei; Guo, Yanjie; Diao, Dongfeng

2017-05-31

Recently, water flow confined in nanochannels has become an interesting topic due to its unique properties and potential applications in nanofluidic devices. The trapped water is predicted to experience high pressure in the gigapascal regime. Theoretical and experimental studies have reported various novel structures of the confined water under high pressure. However, the role of this high pressure on the dynamic properties of water has not been elucidated to date. In the present study, the structure evolution and interfacial friction behavior of water constrained in a graphene nanochannel were investigated via molecular dynamics simulations. Transitions of the confined water to different ice phases at room temperature were observed in the presence of lateral pressure at the gigapascal level. The friction coefficient at the water/graphene interface was found to be dependent on the lateral pressure and nanochannel height. Further theoretical analyses indicate that the pressure dependence of friction is related to the pressure-induced change in the structure of water and the confinement dependence results from the variation in the water/graphene interaction energy barrier. These findings provide a basic understanding of the dynamics of the nanoconfined water, which is crucial in both fundamental and applied science.

Electron induced formation and stability of molecular and cluster ions in gas phase and superfluid helium nanodroplets

International Nuclear Information System (INIS)

Aleem, M. A.

2010-01-01

-induced reactions of the molecules doped into superfluid helium nanodroplets. Pick up of more than one molecule has lead to the formation of ultracold neutral clusters inside the helium droplets. Electron attachment to He nanodroplets doped with ammonia has embarked a synthetic chemistry, forming hydrazine anions, followed by intermediate ion complexes at freezing temperature of 0.37 K of the helium environment. Also a concomitant solvation effect for hydrazine anions has been observed. Electron ionization of He droplets containing ammonia and water co-doped with fullerenes has shown unique sequence of the formation and fragmentation of cluster ions following electron-induced ionization processes. A novel ion-molecule reaction has been observed and established following electron ionization of water and fullerene co-doped into helium nanodroplets. (author)

Thermodynamic properties of bulk and confined water

Energy Technology Data Exchange (ETDEWEB)

Mallamace, Francesco, E-mail: francesco.mallamace@unime.it [Dipartimento di Fisica e Scienza 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 Scienza della Terra Università di Messina and CNISM, I-98168 Messina (Italy); Mallamace, Domenico [Dipartimento di Scienze dell' Ambiente, della Sicurezza, del Territorio, degli Alimenti e della Salute, Università di Messina, I-98166 Messina (Italy); Vasi, Sebastiano; Vasi, Cirino [IPCF-CNR, I-98166 Messina (Italy); Stanley, H. Eugene [Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States)

2014-11-14

The thermodynamic response functions of water display anomalous behaviors. We study these anomalous behaviors in bulk and confined water. We use nuclear magnetic resonance (NMR) to examine the configurational specific heat and the transport parameters in both the thermal stable and the metastable supercooled phases. The data we obtain suggest that there is a behavior common to both phases: that the dynamics of water exhibit two singular temperatures belonging to the supercooled and the stable phase, respectively. One is the dynamic fragile-to-strong crossover temperature (T{sub L} ≃ 225 K). The second, T{sup *} ∼ 315 ± 5 K, is a special locus of the isothermal compressibility K{sub T}(T, P) and the thermal expansion coefficient α{sub P}(T, P) in the P–T plane. In the case of water confined inside a protein, we observe that these two temperatures mark, respectively, the onset of protein flexibility from its low temperature glass state (T{sub L}) and the onset of the unfolding process (T{sup *})

Superstable Ultrathin Water Film Confined in a Hydrophilized Carbon Nanotube.

Science.gov (United States)

Tomo, Yoko; Askounis, Alexandros; Ikuta, Tatsuya; Takata, Yasuyuki; Sefiane, Khellil; Takahashi, Koji

2018-03-14

Fluids confined in a nanoscale space behave differently than in the bulk due to strong interactions between fluid molecules and solid atoms. Here, we observed water confined inside "open" hydrophilized carbon nanotubes (CNT), with diameter of tens of nanometers, using transmission electron microscopy (TEM). A 1-7 nm water film adhering to most of the inner wall surface was observed and remained stable in the high vacuum (order of 10 -5 Pa) of the TEM. The superstability of this film was attributed to a combination of curvature, nanoroughness, and confinement resulting in a lower vapor pressure for water and hence inhibiting its vaporization. Occasional, suspended ultrathin water film with thickness of 3-20 nm were found and remained stable inside the CNT. This film thickness is 1 order of magnitude smaller than the critical film thickness (about 40 nm) reported by the Derjaguin-Landau-Verwey-Overbeek theory and previous experimental investigations. The stability of the suspended ultrathin water film is attributed to the additional molecular interactions due to the extended water meniscus, which balances the rest of the disjoining pressures.

Can we describe graphene confined water structures as overlapping of approaching graphene-water interfacial structures?

Energy Technology Data Exchange (ETDEWEB)

Chialvo, Ariel A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Vlcek, Lukas [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2016-03-21

We investigate the microscopic mechanisms of the overlap of interfacial structures in confined fluids and attempt to answer the question whether the confined structures can be predicted from the original density profiles of individual solid-fluid interfaces. For that purpose we perform (globally) isobaricisothermal (locally, grand canonical) molecular dynamics simulations to extract not only the axial distribution functions of the water-sites for the uncoupled graphene-water interfaces, but also those corresponding to the confined aqueous environments over the interplate range 8 ≤ h(Å) ≤ 28 typically at ambient conditions. We have tested two (i.e., an arithmetic and a geometric) superposition approximations for the singlet density of confined water between flat graphene plates, as well as for a combination of flat and corrugated graphene plates. The outcome of this study suggests that the answer to the title’s question is a “yes”, provided that the interplate distance h is large enough to avoid fluid geometric packing frustration.

Focused ultrasound-facilitated brain drug delivery using optimized nanodroplets: vaporization efficiency dictates large molecular delivery

Science.gov (United States)

Wu, Shih-Ying; Fix, Samantha M.; Arena, Christopher B.; Chen, Cherry C.; Zheng, Wenlan; Olumolade, Oluyemi O.; Papadopoulou, Virginie; Novell, Anthony; Dayton, Paul A.; Konofagou, Elisa E.

2018-02-01

Focused ultrasound with nanodroplets could facilitate localized drug delivery after vaporization with potentially improved in vivo stability, drug payload, and minimal interference outside of the focal zone compared with microbubbles. While the feasibility of blood-brain barrier (BBB) opening using nanodroplets has been previously reported, characterization of the associated delivery has not been achieved. It was hypothesized that the outcome of drug delivery was associated with the droplet’s sensitivity to acoustic energy, and can be modulated with the boiling point of the liquid core. Therefore, in this study, octafluoropropane (OFP) and decafluorobutane (DFB) nanodroplets were used both in vitro for assessing their relative vaporization efficiency with high-speed microscopy, and in vivo for delivering molecules with a size relevant to proteins (40 kDa dextran) to the murine brain. It was found that at low pressures (300-450 kPa), OFP droplets vaporized into a greater number of microbubbles compared to DFB droplets at higher pressures (750-900 kPa) in the in vitro study. In the in vivo study, successful delivery was achieved with OFP droplets at 300 kPa and 450 kPa without evidence of cavitation damage using ¼ dosage, compared to DFB droplets at 900 kPa where histology indicated tissue damage due to inertial cavitation. In conclusion, the vaporization efficiency of nanodroplets positively impacted the amount of molecules delivered to the brain. The OFP droplets due to the higher vaporization efficiency served as better acoustic agents to deliver large molecules efficiently to the brain compared with the DFB droplets.

Anomalous Ground State of the Electrons in Nano-confined Water

Science.gov (United States)

2016-06-13

Anomalous ground state of the electrons in nano -confined water G. F. Reiter1*, Aniruddha Deb2*, Y. Sakurai3, M. Itou3, V. G. Krishnan4, S. J...electronic ground state of nano -confined water must be responsible for these anomalies but has so far not been investigated. We show here for the first time...using x-ray Compton scattering and a computational model, that the ground state configuration of the valence electrons in a particular nano

Phase diagram of supercooled water confined to hydrophilic nanopores

Science.gov (United States)

Limmer, David T.; Chandler, David

2012-07-01

We present a phase diagram for water confined to cylindrical silica nanopores in terms of pressure, temperature, and pore radius. The confining cylindrical wall is hydrophilic and disordered, which has a destabilizing effect on ordered water structure. The phase diagram for this class of systems is derived from general arguments, with parameters taken from experimental observations and computer simulations and with assumptions tested by computer simulation. Phase space divides into three regions: a single liquid, a crystal-like solid, and glass. For large pores, radii exceeding 1 nm, water exhibits liquid and crystal-like behaviors, with abrupt crossovers between these regimes. For small pore radii, crystal-like behavior is unstable and water remains amorphous for all non-zero temperatures. At low enough temperatures, these states are glasses. Several experimental results for supercooled water can be understood in terms of the phase diagram we present.

Temperature dependence of the evaporation lengthscale for water confined between two hydrophobic plates.

Science.gov (United States)

Djikaev, Yuri S; Ruckenstein, Eli

2015-07-01

Liquid water in a hydrophobic confinement is the object of high interest in physicochemical sciences. Confined between two macroscopic hydrophobic surfaces, liquid water transforms into vapor if the distance between surfaces is smaller than a critical separation, referred to as the evaporation lengthscale. To investigate the temperature dependence of the evaporation lengthscale of water confined between two hydrophobic parallel plates, we use the combination of the density functional theory (DFT) with the probabilistic hydrogen bond (PHB) model for water-water hydrogen bonding. The PHB model provides an analytic expression for the average number of hydrogen bonds per water molecule as a function of its distance to a hydrophobic surface and its curvature. Knowing this expression, one can implement the effect of hydrogen bonding between water molecules on their interaction with the hydrophobe into DFT, which is then employed to determine the distribution of water molecules between two macroscopic hydrophobic plates at various interplate distances and various temperatures. For water confined between hydrophobic plates, our results suggest the evaporation lengthscale to be of the order of several nanometers and a linearly increasing function of temperature from T=293 K to T=333 K, qualitatively consistent with previous results. Copyright © 2015 Elsevier Inc. All rights reserved.

Dipole moments of molecules solvated in helium nanodroplets

International Nuclear Information System (INIS)

Stiles, Paul L.; Nauta, Klaas; Miller, Roger E.

2003-01-01

Stark spectra are reported for hydrogen cyanide and cyanoacetylene solvated in helium nanodroplets. The goal of this study is to understand the influence of the helium solvent on measurements of the permanent electric dipole moment of a molecule. We find that the dipole moments of the helium solvated molecules, calculated assuming the electric field is the same as in vacuum, are slightly smaller than the well-known gas-phase dipole moments of HCN and HCCCN. A simple elliptical cavity model quantitatively accounts for this difference, which arises from the dipole-induced polarization of the helium

Helium nanodroplets. Pump-probe ionization of alkali dopings and spin-echo scattering on undoped drops

International Nuclear Information System (INIS)

Droppelmann, G.

2005-09-01

In the framework of this thesis several aspects of the properties of helium nanodroplets and their dopings. The formation of the exciplexes RbHe and KHe on helium droplets was studied by means of pump-probe ionization in real time, whereby the main interest lied on the influence of the applied helium isotopes. The experiments with cesium atoms on the droplet surface aimed on the elucidation of the relaxation dynamics of the surface under regardment both of isotope and size effects. From the pump-probe measurements on the formation of the exciplex RbHe on helium nanodroplets performed in the framework of this thesis formation times of 8.5 ps for Rb 4 He and 11.6 ps for Rb 3 He resulted

Effect of surface hydrophobicity on the dynamics of water at the nanoscale confinement: A molecular dynamics simulation study

International Nuclear Information System (INIS)

Choudhury, Niharendu

2013-01-01

Highlights: • We present atomistic MD simulation of water confined between two paraffin-like plates. • Effect of plate hydrophobicity on the confined water dynamics is investigated. • Diffusivity of confined water is calculated from mean squared displacements. • Rotational dynamics of the confined water has bimodal nature of relaxation. • Monotonic dependence of translational and rotational dynamics on hydrophobicity. - Abstract: We present detailed molecular dynamics simulations of water in and around a pair of plates immersed in water to investigate the effect of degree of hydrophobicity or hydrophilicity of the plates on dynamics of water confined between the two plates. The nature of the plate has been tuned from hydrophobic to hydrophilic and vice versa by varying plate-water dispersion interaction. Analyses of the translational dynamics as performed by calculating mean squared displacements of the confined water reveal a monotonically decreasing trend of the diffusivity with increasing hydrophilicity of the plates. Orientational dynamics of the confined water also follows the same monotonic trend. Although orientational time constant almost does not change with the increase of plate-water dispersion interaction in the hydrophobic regime corresponding to the smaller plate-water attraction, it changes considerably in the hydrophilic regime corresponding to larger plate-water dispersion interactions

The physics of confined flow and its application to water leaks, water permeation and water nanoflows: a review.

Science.gov (United States)

Lei, Wenwen; Rigozzi, Michelle K; McKenzie, David R

2016-02-01

This review assesses the current state of understanding of the calculation of the rate of flow of gases, vapours and liquids confined in channels, in porous media and in permeable materials with an emphasis on the flow of water and its vapour. One motivation is to investigate the relation between the permeation rate of moisture and that of a noncondensable test gas such as helium, another is to assist in unifying theory and experiment across disparate fields. Available theories of single component ideal gas flows in channels of defined geometry (cylindrical, rectangular and elliptical) are described and their predictions compared with measurement over a wide range of conditions defined by the Knudsen number. Theory for two phase flows is assembled in order to understand the behaviour of four standard water leak configurations: vapour, slug, Washburn and liquid flow, distinguished by the number and location of phase boundaries (menisci). Air may or may not be present as a background gas. Slip length is an important parameter that greatly affects leak rates. Measurements of water vapour flows confirm that water vapour shows ideal gas behaviour. Results on carbon nanotubes show that smooth walls may lead to anomalously high slip lengths arising from the properties of 'confined' water. In porous media, behaviour can be matched to the four standard leaks. Traditional membrane permeation models consider that the permeant dissolves, diffuses and evaporates at the outlet side, ideas we align with those from channel flow. Recent results on graphite oxide membranes show examples where helium which does not permeate while at the same time moisture is almost unimpeded, again a result of confined water. We conclude that while there is no a priori relation between a noncondensable gas flow and a moisture flow, measurements using helium will give results within two orders of magnitude of the moisture flow rate, except in the case where there is anomalous slip or confined water

Electron attachment and electron ionization of acetic acid clusters embedded in helium nanodroplets

NARCIS (Netherlands)

da Silva, F. Ferreira; Jaksch, S.; Martins, G.; Dang, H. M.; Dampc, M.; Denifl, S.; Maerk, T. D.; Limao-Vieira, P.; Liu, J.; Yang, S.; Ellis, A. M.; Scheier, P.

2009-01-01

The effect of incident electrons on acetic acid clusters is explored for the first time. The acetic acid clusters are formed inside liquid helium nanodroplets and both cationic and anionic products ejected into the gas phase are detected by mass spectrometry. The cation chemistry (induced by

Structural and dynamic properties of confined water in nanometric model porous materials (8 A≤diameter≤40 A)

International Nuclear Information System (INIS)

Floquet, N.; Coulomb, J.P.; Dufau, N.; Andre, G.; Kahn, R.

2004-01-01

Structural and dynamic properties of confined water have been investigated by 'in situ' neutron-scattering experiments. In the medium confinement regime (for MCM-41 host materials: 20 A≤diameter≤40 A) confined water has rather similar properties to bulk (3d) water. The major difference concerns the solidification phase transition. Strong triple-point depression ΔT 3t is observed and ΔT 3t increases when decreasing the pore diameter (213 K≤ΔT 3t ≤233 K). Such a confined water behaves as a supercooled liquid phase. The ultra-confinement (AlPO 4 -N zeolites: 8 A≤diameter≤12 A), is seen to induce the structuration of the confined water and its stability at room temperature T=300 K due to commensurability effect with the AlPO 4 -5 inner surface. No wetting phenomena are observed for both host materials, the silicic MCM-41 samples and the AlPO 4 -N zeolite family

Confined methane-water interfacial layers and thickness measurements using in situ Raman spectroscopy.

Science.gov (United States)

Pinho, Bruno; Liu, Yukun; Rizkin, Benjamin; Hartman, Ryan L

2017-11-07

Gas-liquid interfaces broadly impact our planet, yet confined interfaces behave differently than unconfined ones. We report the role of tangential fluid motion in confined methane-water interfaces. The interfaces are created using microfluidics and investigated by in situ 1D, 2D and 3D Raman spectroscopy. The apparent CH 4 and H 2 O concentrations are reported for Reynolds numbers (Re), ranging from 0.17 to 8.55. Remarkably, the interfaces are comprised of distinct layers of thicknesses varying from 23 to 57 μm. We found that rarefaction, mixture, thin film, and shockwave layers together form the interfaces. The results indicate that the mixture layer thickness (δ) increases with Re (δ ∝ Re), and traditional transport theory for unconfined interfaces does not explain the confined interfaces. A comparison of our results with thin film theory of air-water interfaces (from mass transfer experiments in capillary microfluidics) supports that the hydrophobicity of CH 4 could decrease the strength of water-water interactions, resulting in larger interfacial thicknesses. Our findings help explain molecular transport in confined gas-liquid interfaces, which are common in a broad range of societal applications.

Quantum Electric Dipole Lattice - Water Molecules Confined to Nanocavities in Beryl

Science.gov (United States)

Dressel, Martin; Zhukova, Elena S.; Thomas, Victor G.; Gorshunov, Boris P.

2018-02-01

Water is subject to intense investigations due to its importance in biological matter but keeps many of its secrets. Here, we unveil an even other aspect by confining H2O molecules to nanosize cages. Our THz and infrared spectra of water in the gemstone beryl evidence quantum tunneling of H2O molecules in the crystal lattice. The water molecules are spread out when confined in a nanocage. In combination with low-frequency dielectric measurements, we were also able to show that dipolar coupling among the H2O molecules leads towards a ferroelectric state at low temperatures. Upon cooling, a ferroelectric soft mode shifts through the THz range. Only quantum fluctuations prevent perfect macroscopic order to be fully achieved. Beside the significance to life science and possible application, nanoconfined water may become the prime example of a quantum electric dipolar lattice.

Anomalous water dynamics at surfaces and interfaces: synergistic effects of confinement and surface interactions

Science.gov (United States)

Biswas, Rajib; Bagchi, Biman

2018-01-01

In nature, water is often found in contact with surfaces that are extended on the scale of molecule size but small on a macroscopic scale. Examples include lipid bilayers and reverse micelles as well as biomolecules like proteins, DNA and zeolites, to name a few. While the presence of surfaces and interfaces interrupts the continuous hydrogen bond network of liquid water, confinement on a mesoscopic scale introduces new features. Even when extended on a molecular scale, natural and biological surfaces often have features (like charge, hydrophobicity) that vary on the scale of the molecular diameter of water. As a result, many new and exotic features, which are not seen in the bulk, appear in the dynamics of water close to the surface. These different behaviors bear the signature of both water-surface interactions and of confinement. In other words, the altered properties are the result of the synergistic effects of surface-water interactions and confinement. Ultrafast spectroscopy, theoretical modeling and computer simulations together form powerful synergistic approaches towards an understanding of the properties of confined water in such systems as nanocavities, reverse micelles (RMs), water inside and outside biomolecules like proteins and DNA, and also between two hydrophobic walls. We shall review the experimental results and place them in the context of theory and simulations. For water confined within RMs, we discuss the possible interference effects propagating from opposite surfaces. Similar interference is found to give rise to an effective attractive force between two hydrophobic surfaces immersed and kept fixed at a separation of d, with the force showing an exponential dependence on this distance. For protein and DNA hydration, we shall examine a multitude of timescales that arise from frustration effects due to the inherent heterogeneity of these surfaces. We pay particular attention to the role of orientational correlations and modification of the

Dynamics of supercooled confined water measured by deep inelastic neutron scattering

Science.gov (United States)

De Michele, Vincenzo; Romanelli, Giovanni; Cupane, Antonio

2018-02-01

In this paper, we present the results of deep inelastic neutron scattering (DINS) measurements on supercooled water confined within the pores (average pore diameter 20 Å) of a disordered hydrophilic silica matrix obtained through hydrolysis and polycondensation of the alkoxide precursor Tetra-Methyl-Ortho-Silicate via the sol-gel method. Experiments were performed at two temperatures (250 K and 210 K, i.e., before and after the putative liquid-liquid transition of supercooled confined water) on a "wet" sample with hydration h 40% w/w, which is high enough to have water-filled pores but low enough to avoid water crystallization. A virtually "dry" sample at h 7% was also investigated to measure the contribution of the silica matrix to the neutron scattering signal. As is well known, DINS measurements allow the determination of the mean kinetic energy and the momentum distribution of the hydrogen atoms in the system and therefore, allow researchers to probe the local structure of supercooled confined water. The main result obtained is that at 210 K the hydrogen mean kinetic energy is equal or even slightly higher than at 250 K. This is at odds with the predictions of a semiempirical harmonic model recently proposed to describe the temperature dependence of the kinetic energy of hydrogen in water. This is a new and very interesting result, which suggests that at 210 K, the water hydrogens experience a stiffer intermolecular potential than at 250 K. This is in agreement with the liquid-liquid transition hypothesis.

Docetaxel-loaded multilayer nanoparticles with nanodroplets for cancer therapy

OpenAIRE

Oh, Keun Sang; Kim, Kyungim; Yoon, Byeong Deok; Lee, Hye Jin; Park, Dal Yong; Kim, Eun-yeong; Lee, Kiho; Seo, Jae Hong; Yuk, Soon Hong

2016-01-01

Keun Sang Oh,1,* Kyungim Kim,1,* Byeong Deok Yoon,1 Hye Jin Lee,1 Dal Yong Park,1 Eun-yeong Kim,1 Kiho Lee,1 Jae Hong Seo,2 Soon Hong Yuk1,2 1College of Pharmacy, Korea University, Sejong, 2Biomedical Research Center, Korea University Guro Hospital, Guro-gu, Seoul, Republic of Korea *These authors contributed equally to this work Abstract: A mixture of docetaxel (DTX) and Solutol® HS 15 (Solutol) transiently formed nanodroplets when it was suspended in an aqueous medium. However, n...

Communication: Relationship between local structure and the stability of water in hydrophobic confinement

Science.gov (United States)

Altabet, Y. Elia; Debenedetti, Pablo G.

2017-12-01

Liquid water confined between nanoscale hydrophobic objects can become metastable with respect to its vapor at nanoscale separations. While the separations are only several molecular diameters, macroscopic theories are often invoked to interpret the thermodynamics and kinetics of water under confinement. We perform detailed rate and free energy calculations via molecular simulations in order to assess the dependence of the rate of evaporation, free energy barriers, and free energy differences between confined liquid and vapor upon object separation and compare them to the relevant macroscopic theories. At small enough separations, the rate of evaporation appears to deviate significantly from the predictions of classical nucleation theory, and we attribute such deviations to changes in the structure of the confined liquid film. However, the free energy difference between the confined liquid and vapor phases agrees quantitatively with macroscopic theory, and the free energy barrier to condensation displays qualitative agreement. Overall, the present work suggests that theories attempting to capture the kinetic behavior of nanoscale systems should incorporate structural details rather than treating it as a continuum.

Glass transition and relaxation dynamics of propylene glycol-water solutions confined in clay

Science.gov (United States)

Elamin, Khalid; Björklund, Jimmy; Nyhlén, Fredrik; Yttergren, Madeleine; Mârtensson, Lena; Swenson, Jan

2014-07-01

The molecular dynamics of aqueous solutions of propylene glycol (PG) and propylene glycol methylether (PGME) confined in a two-dimensional layer-structured Na-vermiculite clay has been studied by broadband dielectric spectroscopy and differential scanning calorimetry. As typical for liquids in confined geometries the intensity of the cooperative α-relaxation becomes considerably more suppressed than the more local β-like relaxation processes. In fact, at high water contents the calorimetric glass transition and related structural α-relaxation cannot even be observed, due to the confinement. Thus, the intensity of the viscosity related α-relaxation is dramatically reduced, but its time scale as well as the related glass transition temperature Tg are for both systems only weakly influenced by the confinement. In the case of the PGME-water solutions it is an important finding since in the corresponding bulk system a pronounced non-monotonic concentration dependence of the glass transition related dynamics has been observed due to the growth of hydrogen bonded relaxing entities of water bridging between PGME molecules [J. Sjöström, J. Mattsson, R. Bergman, and J. Swenson, Phys. Chem. B 115, 10013 (2011)]. The present results suggest that the same type of structural entities are formed in the quasi-two-dimensional space between the clay platelets. It is also observed that the main water relaxation cannot be distinguished from the β-relaxation of PG or PGME in the concentration range up to intermediate water contents. This suggests that these two processes are coupled and that the water molecules affect the time scale of the β-relaxation. However, this is most likely true also for the corresponding bulk solutions, which exhibit similar time scales of this combined relaxation process below Tg. Finally, it is found that at higher water contents the water relaxation does not merge with, or follow, the α-relaxation above Tg, but instead crosses the �

Multi-scale experimental and numerical study of the structure and the dynamics of water confined in clay minerals

International Nuclear Information System (INIS)

Guillaud, Emmanuel Bertrand

2017-01-01

Clay are complex minerals with a multi-scale porosity and a remarkable ability to swell under humid atmosphere. These materials have many applications in catalysis, waste management, construction industry... However, the properties of confined water are still not fully understood, due in particular to the complexity of water itself. The aim of this work is, using mainly molecular simulations and vibrational spectroscopy, to understand the structure and the dynamics of water confined in clay minerals. To evaluate the accuracy of numerical models to describe water confined in clay minerals, and to understand the origin of its structural and dynamical properties, a large part of the work was devoted to the building blocks of clays: pure bulk water, water at the surface of a solid, and salt water. To this extent, the viscoelastic properties of water from the deeply supercooled regime to the boiling temperature were investigated using classical molecular dynamics. The evolution of the friction properties of water on a prototypical solid surface was also analyzed, and the accuracy of ab initio approaches and empirical salt models was studied. In a second part, those results were confronted to the properties of water confined in clay minerals at low and room temperature, studied both experimentally and numerically. Experimental work consisted mostly in extensive far- and -mid infrared absorption spectrometry measurements, whereas numerical work mainly consisted in empirical molecular dynamics simulations. Especially, the existence of confinement- or temperature-induced phase transitions of confined water was investigated. (author)

Deuteron-NMR investigation on the dynamics of supercooled, confined water

Energy Technology Data Exchange (ETDEWEB)

Sattig, Matthias; Vogel, Michael [TU Darmstadt, Institut fuer Festkoerperphysik (Germany)

2013-07-01

The dynamical behaviour of water in the regime of the supercooled liquid is a topic of large interest. In particular, the existence of a fragile-to-strong transition (FST) at T=225K related to the transition between two distinct phases of liquid water is controversially discussed. Due to crystallization the temperature range proposed for the FST is hardly accessible in bulk water. Therefore, we confine heavy water to narrow pores in the mesoporous silicate MCM-41. This suppresses the freezing of a substantial fraction of water, enabling direct investigation of the interesting temperatures. Deuteron-NMR methods are utilised to determine the rotational correlation times τ of water on time scales from ns up to s. The spin-lattice-relaxation time T{sub 1} exhibits a typical minimum at about T = 230 K. Above this minimum the correlation times follow a Vogel-Fulcher-Tammann law. Below the minimum, two relaxation processes could be observed. The low-temperature processes show a different temperature dependence, where the curves τ(T) of all processes intersect at about T = 230 K. A comparison with literature data from neutron scattering and dielectric spectroscopy gives rise to the idea that the observed crossover is due to this intersection of processes rather than to a FST. To test this idea studies on water confined to MCM-41 with different pore sizes and fillings are in progress.

An Inelastic Neutron Scattering Study of Confined Surface Water on Rutile Nanoparticles

International Nuclear Information System (INIS)

Spencer, Elinor; Levchenko, Andrey; Ross, Nancy; Kolesnikov, Alexander I.; Boerio-Goates, Juliana; Woodfield, Brian; Navrotsky, Alexandra; Li, Guangshe

2009-01-01

The vibrational density of states (VDOS) for water confined on the surface of rutile-TiO2 nanoparticles has been extracted from low temperature inelastic neutron scattering spectra. Two rutile-TiO2 nanoparticle samples that differ in their respective levels of hydration, namely TiO2 0.37H2O (1) and TiO2 0.22H2O (2) have been studied. The temperature dependency of the heat capacities for the two samples has been quantified from the VDOS. The results from this study are compared with previously reported data for water confined on anatase-TiO2 nanoparticles.

Preliminary analysis of some waters from the confined aquifers underlying the Hanford site

International Nuclear Information System (INIS)

Deju, R.A.

1978-09-01

This report presents results of analyses available at this time from waters from some wells sampled in or near the Hanford Site. The analyses of these wells were done for various purposes and are consolidated to help define the nature of the waters found within the Columbia Plateau basaltic sequence. Results of the analyses show the waters from the unconfined aquifers underlying the Hanford Site are characterized by a high calcium--magnesium content. These waters can be described as calcium--magnesium--bicarbonate-type. Waters from deeper basaltic confined aquifers are primarily of the sodium bicarbonate type. Two waters sampled from the Grande Ronde Formation from Rattlesnake Hills Exploratory Well Number 1 are slightly different and can be described as sodium--calcium--bicarbonate--sulfate--chloride-type. Age-dating results for these water samples lead to the conclusions that waters from the confined aquifers were entrapped 15,000 to 23,000 years ago

Cavitation in confined water: ultra-fast bubble dynamics

Science.gov (United States)

Vincent, Olivier; Marmottant, Philippe

2012-02-01

In the hydraulic vessels of trees, water can be found at negative pressure. This metastable state, corresponding to mechanical tension, is achieved by evaporation through a porous medium. It can be relaxed by cavitation, i.e. the sudden nucleation of vapor bubbles. Harmful for the tree due to the subsequent emboli of sap vessels, cavitation is on the contrary used by ferns to eject spores very swiftly. We will focus here on the dynamics of the cavitation bubble, which is of primary importance to explain the previously cited natural phenomena. We use the recently developed method of artificial tress, using transparent hydrogels as the porous medium. Our experiments, on water confined in micrometric hydrogel cavities, show an extremely fast dynamics: bubbles are nucleated at the microsecond timescale. For cavities larger than 100 microns, the bubble ``rings'' with damped oscillations at MHz frequencies, whereas for smaller cavities the oscillations become overdamped. This rich dynamics can be accounted for by a model we developed, leading to a modified Rayleigh-Plesset equation. Interestingly, this model predicts the impossibility to nucleate bubbles above a critical confinement that depends on liquid negative pressure and corresponds to approximately 100 nm for 20 MPa tensions.

Communication: X-ray coherent diffractive imaging by immersion in nanodroplets

Directory of Open Access Journals (Sweden)

Rico Mayro P. Tanyag

2015-09-01

Full Text Available Lensless x-ray microscopy requires the recovery of the phase of the radiation scattered from a specimen. Here, we demonstrate a de novo phase retrieval technique by encapsulating an object in a superfluid helium nanodroplet, which provides both a physical support and an approximate scattering phase for the iterative image reconstruction. The technique is robust, fast-converging, and yields the complex density of the immersed object. Images of xenon clusters embedded in superfluid helium droplets reveal transient configurations of quantum vortices in this fragile system.

Dynamics of confined reactive water in smectite clay-zeolite composites.

Science.gov (United States)

Pitman, Michael C; van Duin, Adri C T

2012-02-15

The dynamics of water confined to mesoporous regions in minerals such as swelling clays and zeolites is fundamental to a wide range of resource management issues impacting many processes on a global scale, including radioactive waste containment, desalination, and enhanced oil recovery. Large-scale atomic models of freely diffusing multilayer smectite particles at low hydration confined in a silicalite cage are used to investigate water dynamics in the composite environment with the ReaxFF reactive force field over a temperature range of 300-647 K. The reactive capability of the force field enabled a range of relevant surface chemistry to emerge, including acid/base equilibria in the interlayer calcium hydrates and silanol formation on the edges of the clay and inner surface of the zeolite housing. After annealing, the resulting clay models exhibit both mono- and bilayer hydration structures. Clay surface hydration redistributed markedly and yielded to silicalite water loading. We find that the absolute rates and temperature dependence of water dynamics compare well to neutron scattering data and pulse field gradient measures from relevant samples of Ca-montmorillonite and silicalite, respectively. Within an atomistic, reactive context, our results distinguish water dynamics in the interlayer Ca(OH)(2)·nH(2)O environment from water flowing over the clay surface, and from water diffusing within silicalite. We find that the diffusion of water when complexed to Ca hydrates is considerably slower than freely diffusing water over the clay surface, and the reduced mobility is well described by a difference in the Arrhenius pre-exponential factor rather than a change in activation energy.

The physics of confined flow and its application to water leaks, water permeation and water nanoflows: a review

International Nuclear Information System (INIS)

Lei, Wenwen; Rigozzi, Michelle K; McKenzie, David R

2016-01-01

This review assesses the current state of understanding of the calculation of the rate of flow of gases, vapours and liquids confined in channels, in porous media and in permeable materials with an emphasis on the flow of water and its vapour. One motivation is to investigate the relation between the permeation rate of moisture and that of a noncondensable test gas such as helium, another is to assist in unifying theory and experiment across disparate fields. Available theories of single component ideal gas flows in channels of defined geometry (cylindrical, rectangular and elliptical) are described and their predictions compared with measurement over a wide range of conditions defined by the Knudsen number. Theory for two phase flows is assembled in order to understand the behaviour of four standard water leak configurations: vapour, slug, Washburn and liquid flow, distinguished by the number and location of phase boundaries (menisci). Air may or may not be present as a background gas. Slip length is an important parameter that greatly affects leak rates. Measurements of water vapour flows confirm that water vapour shows ideal gas behaviour. Results on carbon nanotubes show that smooth walls may lead to anomalously high slip lengths arising from the properties of ‘confined’ water. In porous media, behaviour can be matched to the four standard leaks. Traditional membrane permeation models consider that the permeant dissolves, diffuses and evaporates at the outlet side, ideas we align with those from channel flow. Recent results on graphite oxide membranes show examples where helium which does not permeate while at the same time moisture is almost unimpeded, again a result of confined water. We conclude that while there is no a priori relation between a noncondensable gas flow and a moisture flow, measurements using helium will give results within two orders of magnitude of the moisture flow rate, except in the case where there is anomalous slip or confined

A GASFLOW analysis of a steam explosion accident in a typical light-water reactor confinement building

International Nuclear Information System (INIS)

Travis, J.R.; Wilson, T.L.; Spore, J.W.; Lam, K.L.; Rao, D.V.

1994-01-01

Steam over-pressurization resulting from ex-vessel steam explosion (fuel-coolant interaction) may pose a serious challenge to the integrity of a typical light-water reactor confinement building. If the steam generation rate exceeds the removal capacity of the Airborne Activity Confinement System, confinement overpressurization occurs. Thus, there is a large potential for an uncontrolled and unfiltered release of fission products from the confinement atmosphere to the environment at the time of the steam explosion. The GASFLOW computer code was used to analyze the effects of a hypothetical steam explosion and the transport of steam and hydrogen throughout a typical light-water reactor confinement building. The effects of rapid pressurization and the resulting forces on the internal structures and the heat exchanger service bay hatch covers were calculated. Pressurization of the ventilation system and the potential damage to the ventilation fans and high-efficiency particulate air filters were assessed. Because of buoyancy forces and the calculated confinement velocity field, the hydrogen diffuses and mixes in the confinement atmosphere but tends to be transported to its upper region. (author). 2 refs., 14 figs

A GASFLOW analysis of a steam explosion accident in a typical light-water reactor confinement building

International Nuclear Information System (INIS)

Travis, J.R.; Wilson, T.L.; Spore, J.W.; Lam, K.L.; Rao, D.V.

1994-01-01

Steam over-pressurization resulting from ex-vessel steam explosion (fuel-coolant interaction) may pose a serious challenge to the integrity of a typical light-water reactor confinement building. If the steam generation rate exceeds the removal capacity of the Airborne Activity Confinement System, confinement over pressurization occurs. Thus, there is a large potential for an uncontrolled and unfiltered release of fission products from the confinement atmosphere to the environment at the time of the steam explosion. The GASFLOW computer code was used to analyze the effects of a hypothetical steam explosion and the transport of steam and hydrogen throughout a typical light-water reactor confinement building. The effects of rapid pressurization and the resulting forces on the internal structures and the heat exchanger service bay hatch covers were calculated. Pressurization of the ventilation system and the potential damage to the ventilation fans and high-efficiency particulate air filters were assessed. Because of buoyancy forces and the calculated confinement velocity field, the hydrogen diffuses and mixes in the confinement atmosphere but tends to be transported to its upper region

Evaporation rate of water in hydrophobic confinement.

Science.gov (United States)

Sharma, Sumit; Debenedetti, Pablo G

2012-03-20

The drying of hydrophobic cavities is believed to play an important role in biophysical phenomena such as the folding of globular proteins, the opening and closing of ligand-gated ion channels, and ligand binding to hydrophobic pockets. We use forward flux sampling, a molecular simulation technique, to compute the rate of capillary evaporation of water confined between two hydrophobic surfaces separated by nanoscopic gaps, as a function of gap, surface size, and temperature. Over the range of conditions investigated (gaps between 9 and 14 Å and surface areas between 1 and 9 nm(2)), the free energy barrier to evaporation scales linearly with the gap between hydrophobic surfaces, suggesting that line tension makes the predominant contribution to the free energy barrier. The exponential dependence of the evaporation rate on the gap between confining surfaces causes a 10 order-of-magnitude decrease in the rate when the gap increases from 9 to 14 Å. The computed free energy barriers are of the order of 50 kT and are predominantly enthalpic. Evaporation rates per unit area are found to be two orders of magnitude faster in confinement by the larger (9 nm(2)) than by the smaller (1 nm(2)) surfaces considered here, at otherwise identical conditions. We show that this rate enhancement is a consequence of the dependence of hydrophobic hydration on the size of solvated objects. For sufficiently large surfaces, the critical nucleus for the evaporation process is a gap-spanning vapor tube.

Effect of Short-Circuit Pathways on Water Quality in Selected Confined Aquifers (Invited)

Science.gov (United States)

McMahon, P. B.

2010-12-01

Confined aquifers in the United States generally contain fewer anthropogenic contaminants than unconfined aquifers because confined aquifers often contain water recharged prior to substantial human development and redox conditions are more reducing, which favors degradation of common contaminants like nitrate and chlorinated solvents. Groundwater in a confined part of the High Plains aquifer near York, Nebraska had an adjusted radiocarbon age of about 2,000 years, and groundwater in a confined part of the Floridan aquifer near Tampa, Florida had apparent ages greater than 60 years on the basis of tritium measurements. Yet compounds introduced more recently into the environment (anthropogenic nitrate and volatile organic compounds) were detected in selected public-supply wells completed in both aquifers. Depth-dependent measurements of flow and chemistry in the pumping supply wells, groundwater age dating, numerical modeling of groundwater flow, and other monitoring data indicated that the confined aquifers sampled by the supply wells were connected to contaminated unconfined aquifers by short-circuit pathways. In the High Plains aquifer, the primary pathways appeared to be inactive irrigation wells screened in both the unconfined and confined aquifers. In the Floridan aquifer, the primary pathways were karst sinkholes and conduits. Heavy pumping in both confined systems exacerbated the problem by reducing the potentiometric surface and increasing groundwater velocities, thus enhancing downward gradients and reducing reaction times for processes like denitrification. From a broader perspective, several confined aquifers in the U.S. have experienced large declines in their potentiometric surfaces because of groundwater pumping and this could increase the potential for contamination in those aquifers, particularly where short-circuit pathways connect them to shallower, contaminated sources of water, such as was observed in York and Tampa.

Characterizing hydrophobicity of amino acid side chains in a protein environment via measuring contact angle of a water nanodroplet on planar peptide network.

Science.gov (United States)

Zhu, Chongqin; Gao, Yurui; Li, Hui; Meng, Sheng; Li, Lei; Francisco, Joseph S; Zeng, Xiao Cheng

2016-11-15

Hydrophobicity of macroscopic planar surface is conventionally characterized by the contact angle of water droplets. However, this engineering measurement cannot be directly extended to surfaces of proteins, due to the nanometer scale of amino acids and inherent nonplanar structures. To measure the hydrophobicity of side chains of proteins quantitatively, numerous parameters were developed to characterize behavior of hydrophobic solvation. However, consistency among these parameters is not always apparent. Herein, we demonstrate an alternative way of characterizing hydrophobicity of amino acid side chains in a protein environment by constructing a monolayer of amino acids (i.e., artificial planar peptide network) according to the primary and the β-sheet secondary structures of protein so that the conventional engineering measurement of the contact angle of a water droplet can be brought to bear. Using molecular dynamics simulations, contact angles θ of a water nanodroplet on the planar peptide network, together with excess chemical potentials of purely repulsive methane-sized Weeks-Chandler-Andersen solute, are computed. All of the 20 types of amino acids and the corresponding planar peptide networks are studied. Expectedly, all of the planar peptide networks with nonpolar amino acids are hydrophobic due to θ [Formula: see text] 90°, whereas all of the planar peptide networks of the polar and charged amino acids are hydrophilic due to θ [Formula: see text] 90°. Planar peptide networks of the charged amino acids exhibit complete-wetting behavior due to θ [Formula: see text] 0°. This computational approach for characterization of hydrophobicity can be extended to artificial planar networks of other soft matter.

Analysis of confinement effects for in-water seismic tests on PWR fuel assemblies

International Nuclear Information System (INIS)

Broc, Daniel; Queval, Jean-Claude; Rigaudeau, J.; Viallet, E.

2001-01-01

In the framework of a comprehensive program on the seismic behaviour of the PWR reactor cores, tests have been performed on a row of six PWR fuel assemblies, with two confinement configurations in water. Global fluid motion along the row is not allowed in the 'full confinement configuration', and is allowed in the 'lateral confinement configuration'. The seismic test results show that the impact forces at assembly grid levels are significantly smaller with the full confinement. This is due to damping, which is found to be larger in this configuration where the average fluid velocity inside the assembly (around the rods) is itself larger. We present analyses of these phenomena from theoretical and experimental standpoint. This involves both fluid models and structural models of the assembly row. (author)

Effects of confinement on the dielectric response of water extends up to mesoscale dimensions

DEFF Research Database (Denmark)

De Luca, Sergio; Kannam, Sridhar Kumar; Todd, B.D.

2016-01-01

of confined water under the influence of external electric fields along with the dipolar fluctuations at equilibrium. The confinement induces a strong anisotropic effect which is evident up to 100 nm channel width, and may extend to macroscopic dimensions. The root-mean-square fluctuations of the total...... dimensions. Consistent with dipole moment fluctuations, the effect of confinement on the dielectric response also persists up to channel widths considerably beyond 100 nm. When an electric field is applied in the perpendicular direction, the orientational relaxation is 3 orders of magnitude faster than...

Crystallization kinetics of Ga metallic nano-droplets under As flux

International Nuclear Information System (INIS)

Bietti, S; Somaschini, C; Sanguinetti, S

2013-01-01

We present an experimental investigation of the crystallization dynamics of Ga nano-droplets under As flux. The transformation of the metallic Ga contained in the droplets into a GaAs nano-island proceeds by increasing the size of a tiny ring of GaAs which is formed just after the Ga deposition at the rim of a droplet. The GaAs crystallization rate depends linearly on the liquid–solid interface area. The maximum growth rate is set by the As flux impinging on the droplet, thus showing an efficient As incorporation and transport despite the predicted low solubility of the As in metallic Ga at the crystallization temperatures. (paper)

Controlling Chemical Reactions in Confined Environments: Water Dissociation in MOF-74

Directory of Open Access Journals (Sweden)

Erika M. A. Fuentes-Fernandez

2018-02-01

Full Text Available The confined porous environment of metal organic frameworks (MOFs is an attractive system for studying reaction mechanisms. Compared to flat oxide surfaces, MOFs have the key advantage that they exhibit a well-defined structure and present significantly fewer challenges in experimental characterization. As an example of an important reaction, we study here the dissociation of water—which plays a critical role in biology, chemistry, and materials science—in MOFs and show how the knowledge of the structure in this confined environment allows for an unprecedented level of understanding and control. In particular, combining in-situ infrared spectroscopy and first-principles calculations, we show that the water dissociation reaction can be selectively controlled inside Zn-MOF-74 by alcohol, through both chemical and physical interactions. Methanol is observed to speed up water dissociation by 25% to 100%, depending on the alcohol partial pressure. On the other hand, co-adsorption of isopropanol reduces the speed of the water reaction, due mostly to steric interactions. In addition, we also investigate the stability of the product state after the water dissociation has occurred and find that the presence of additional water significantly stabilizes the dissociated state. Our results show that precise control of reactions within nano-porous materials is possible, opening the way for advances in fields ranging from catalysis to electrochemistry and sensors.

Multiscale Simulations Using Particles

DEFF Research Database (Denmark)

Walther, Jens Honore

vortex methods for problems in continuum fluid dynamics, dissipative particle dynamics for flow at the meso scale, and atomistic molecular dynamics simulations of nanofluidic systems. We employ multiscale techniques to breach the atomistic and continuum scales to study fundamental problems in fluid...... dynamics. Recent work on the thermophoretic motion of water nanodroplets confined inside carbon nanotubes, and multiscale techniques for polar liquids will be discussed in detail at the symposium....

Technique to measure contact angle of micro/nanodroplets using atomic force microscopy

International Nuclear Information System (INIS)

Jung, Yong Chae; Bhushan, Bharat

2008-01-01

Contact angle is the primary parameter that characterizes wetting; however, the measurement techniques have been limited to droplets with a diameter as low as about 50 μm. The authors developed an atomic force microscopy-based technique to measure the contact angle of micro- and nanodroplets deposited using a modified nanoscale dispensing tip. The obtained contact angle results were compared with those of a macrodroplet (2.1 mm diameter). It was found that the contact angle on various surfaces decreases with decreasing the droplet size

Femtosecond vibrational dynamics in water nano-droplets

NARCIS (Netherlands)

Cringus, Gheorghe Dan

2008-01-01

Water is probably the most researched substance on Earth. The interest in water, and redominantly in liquid water, is due to its importance on both macro- and microscopic scales. Although people have been trying to understand water for centuries, this ubiquitous liquid is still surrounded by mystery

Alignment and Imaging of the CS2 Dimer Inside Helium Nanodroplets

Science.gov (United States)

Pickering, James D.; Shepperson, Benjamin; Hübschmann, Bjarke A. K.; Thorning, Frederik; Stapelfeldt, Henrik

2018-03-01

The carbon disulphide (CS2) dimer is formed inside He nanodroplets and identified using fs laser-induced Coulomb explosion, by observing the CS2+ ion recoil velocity. It is then shown that a 160 ps moderately intense laser pulse can align the dimer in advantageous spatial orientations which allow us to determine the cross-shaped structure of the dimer by analysis of the correlations between the emission angles of the nascent CS2+ and S+ ions, following the explosion process. Our method will enable fs time-resolved structural imaging of weakly bound molecular complexes during conformational isomerization, including formation of exciplexes.

Transport properties of supercooled confined water

International Nuclear Information System (INIS)

Mallamace, F.; Baglioni, P.; Corsaro, C.; Spooren, J.; Stanley, H.E.; Chen, S.-H.

2011-01-01

We present an overview of recent experiments performed on water in the deeply supercooled region, a temperature region of fundamental importance in the science of water. We examine data generated by nuclear magnetic resonance, quasi-elastic neutron scattering, Fourier-transform infrared spectroscopy, and Raman spectroscopy, and study water confined in nanometer-scale environments. When contained within small pores, water does not crystallize and can be supercooled well below its homogeneous nucleation temperature T H. On this basis, it is possible to carry out a careful analysis of the well-known thermodynamic anomalies of water. Studying the temperature and pressure dependencies of water dynamics, we show that the liquid-liquid phase transition (LLPT) hypothesis represents a reliable model for describing liquid water. In this model, liquid water is a mixture of two different local structures: a low density liquid (LDL) and a high-density liquid (HDL). The LLPT line terminates at a low-T liquid-liquid critical point. We discuss the following experimental findings: 1.) the crossover from non-Arrhenius behavior at high T to Arrhenius behavior at low T in transport parameters; 2.) the breakdown of the Stokes-Einstein relation; 3.) the existence of a Widom line, which is the locus of points corresponding to a maximum correlation length in the P-T phase diagram and which ends in the liquid-liquid critical point; 4.) the direct observation of the LDL phase; and 5.) the minimum in the density at approximately 70 K below the temperature of the density maximum. In our opinion these results strongly support the LLPT hypothesis. All of the basic science and technology community should be impressed by the fact that, although the few ideas (apparently elementary) developed concerning water approximately 27 centuries ago have changed very little up to now, because of the current expansion in our knowledge in this area, they can begin to change in the near future.

Microviscosity of supercooled water confined within aminopropyl-modified mesoporous silica as studied by time-resolved fluorescence spectroscopy.

Science.gov (United States)

Yamaguchi, Akira; Namekawa, Manato; Itoh, Tetsuji; Teramae, Norio

2012-01-01

The fluorescence dynamics of rhodamine B (RhB) immobilized on the pore surface of aminopropyl (AP)-modified mesoporous silica (diameter of the silica framework, 3.1 nm) was examined at temperatures between 293 and 193 K to study the microviscosity of supercooled water confined inside the pores. The mesoporous silica specimen with a dense AP layer (2.1 molecules nm(-2)) was prepared, and RhB isothiocyanate was covalently bound to part of the surface AP groups. The fluorescence lifetime of the surface RhB increased with decreasing temperature from 293 to 223 K, indicating that freezing of the confined water did not occur in this temperature range. The microviscosity of the supercooled confined water was evaluated from an analysis of the lifetime data based on a frequency-dependent friction model.

Milking liquid nano-droplets by an IR laser: a new modality for the visualization of electric field lines

International Nuclear Information System (INIS)

Vespini, Veronica; Coppola, Sara; Grilli, Simonetta; Paturzo, Melania; Ferraro, Pietro

2013-01-01

Liquid handling at micron- and nano-scale is of paramount importance in many fields of application such as biotechnology and biochemistry. In fact, the microfluidics technologies play an important role in lab-on-a-chip devices and, in particular, the dispensing of liquid droplets is a required functionality. Different approaches have been developed for manipulating, dispensing and controlling nano-droplets under a wide variety of configurations. Here we demonstrate that nano-droplets can be drawn from liquid drop or film reservoirs through a sort of milking effect achieved by the absorption of IR laser radiation into a pyroelectric crystal. The generation of the pyroelectric field induced by the IR laser is calculated numerically and a specific experiment has been designed to visualize the electric field stream lines that are responsible for the liquid milking effect. The experiments performed are expected to open a new route for the visualization, measure and characterization procedures in the case of electrohydrodynamic applications. (paper)

Free energy barriers to evaporation of water in hydrophobic confinement.

Science.gov (United States)

Sharma, Sumit; Debenedetti, Pablo G

2012-11-08

We use umbrella sampling Monte Carlo and forward and reverse forward flux sampling (FFS) simulation techniques to compute the free energy barriers to evaporation of water confined between two hydrophobic surfaces separated by nanoscopic gaps, as a function of the gap width, at 1 bar and 298 K. The evaporation mechanism for small (1 × 1 nm(2)) surfaces is found to be fundamentally different from that for large (3 × 3 nm(2)) surfaces. In the latter case, the evaporation proceeds via the formation of a gap-spanning tubular cavity. The 1 × 1 nm(2) surfaces, in contrast, are too small to accommodate a stable vapor cavity. Accordingly, the associated free energy barriers correspond to the formation of a critical-sized cavity for sufficiently large confining surfaces, and to complete emptying of the gap region for small confining surfaces. The free energy barriers to evaporation were found to be of O(20kT) for 14 Å gaps, and to increase by approximately ~5kT with every 1 Å increase in the gap width. The entropy contribution to the free energy of evaporation was found to be independent of the gap width.

Quantum Behavior of Water Molecules Confined to Nanocavities in Gemstones.

Science.gov (United States)

Gorshunov, Boris P; Zhukova, Elena S; Torgashev, Victor I; Lebedev, Vladimir V; Shakurov, Gil'man S; Kremer, Reinhard K; Pestrjakov, Efim V; Thomas, Victor G; Fursenko, Dimitry A; Dressel, Martin

2013-06-20

When water is confined to nanocavities, its quantum mechanical behavior can be revealed by terahertz spectroscopy. We place H2O molecules in the nanopores of a beryl crystal lattice and observe a rich and highly anisotropic set of absorption lines in the terahertz spectral range. Two bands can be identified, which originate from translational and librational motions of the water molecule isolated within the cage; they correspond to the analogous broad bands in liquid water and ice. In the present case of well-defined and highly symmetric nanocavities, the observed fine structure can be explained by macroscopic tunneling of the H2O molecules within a six-fold potential caused by the interaction of the molecule with the cavity walls.

The 1-ethyl-3-methylimidazolium bis(trifluoro-methylsulfonyl)-imide ionic liquid nanodroplets on solid surfaces and in electric field: A molecular dynamics simulation study

Science.gov (United States)

Dong, Dengpan; Vatamanu, Jenel P.; Wei, Xiaoyu; Bedrov, Dmitry

2018-05-01

Atomistic molecular dynamics simulations were conducted to study the wetting states of 1-ethyl-3-methylimidazolium bis(trifluoro-methylsulfonyl)-imide ionic liquid (IL) nanodroplets on surfaces with different strengths of van der Waals (VDW) interactions and in the presence of an electric field. By adjusting the depth of Lennard-Jones potential, the van der Waals interaction between the solid surface and ionic liquid was systematically varied. The shape of the droplets was analyzed to extract the corresponding contact angle utilized to characterize wetting states of the nanodroplets. The explored range of surface-IL interactions allowed contact angles ranging from complete IL spreading on the surface to poor wettability. The effect of the external electrical field was explored by adding point charges to the surface atoms. Systems with two charge densities (±0.002 e/atom and ±0.004 e/atom) that correspond to 1.36 V/nm and 2.72 V/nm electric fields were investigated. Asymmetrical wetting states were observed for both cases. At 1.36 V/nm electric field, contributions of IL-surface VDW interactions and Coulombic interactions to the wetting state were competitive. At 2.72 V/nm field, electrostatic interactions dominate the interaction between the nanodroplet and surface, leading to enhanced wettability on all surfaces.

Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates

International Nuclear Information System (INIS)

Krishnan, N. M. Anoop; Wang, Bu; Falzone, Gabriel; Le Pape, Yann; Neithalath, Narayanan

2016-01-01

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/SiO_2 (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. Altogether, 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.

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/SiO 2 (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.

Experimental Assessment of Water Sprays Utilization for Controlling Hydrogen Sulfide Releases in Confined Space

Directory of Open Access Journals (Sweden)

Dongfeng Zhao

2015-01-01

Full Text Available This paper reported the utilization of water spray for controlling H2S release in a confined space, which is especially important in industry. A typical spray tower was modified to simulate the confined space for people's enterable routine operation (e.g., pump room, in which the dilution capacity of water sprays can also be evaluated. This work consists of two parts: the first part focuses on the influences of different operating conditions on chemical dilution capacities of water sprays in mechanisms; the second one is comparison between two nozzle configurations for evaluating their feasibilities of practical application. Water sprays express eligible performance for H2S release control even though their dilution capacity was weakened at high gaseous concentrations and rates of releases. The presence of Na2CO3 can significantly improve absorption effectiveness of H2S in water and the optimal Na2CO3 additive was found to be 1.0 g·L−1 in this test. Compared with Na2CO3, adjusting water flow rate may be an effective strategy in enhancing dilution capacity of water sprays due to the fact that larger flow rate led to both less dilution time (TD and dilution concentration (CD. Furthermore, multinozzle configuration is more efficient than single-nozzle configuration under the same water consumption.

Crumpling of graphene oxide through evaporative confinement in nanodroplets produced by electrohydrodynamic aerosolization

Energy Technology Data Exchange (ETDEWEB)

Kavadiya, Shalinee; Raliya, Ramesh; Schrock, Michael; Biswas, Pratim, E-mail: pbiswas@wustl.edu [Washington University in St. Louis, Aerosol and Air Quality Research Laboratory, Department of Energy, Environmental and Chemical Engineering (United States)

2017-02-15

Restacking of graphene oxide (GO) nanosheets results in loss of surface area and creates limitations in its widespread use for applications. Previously, two-dimensional (2D) GO sheets have been crumpled into 3D structures to prevent restacking using different techniques. However, synthesis of nanometer size crumpled graphene particles and their direct deposition onto a substrate have not been demonstrated under room temperature condition so far. In this work, the evaporative crumpling of GO sheets into very small size (<100 nm) crumpled structures using an electrohydrodynamic atomization technique is described. Systematic study of the effect of different electrohydrodynamic atomization parameters, such as (1) substrate-to-needle distance, (2) GO concentration in the precursor solution, and (3) flow rate (droplet size) on the GO crumpling, is explored. Crumpled GO (CGO) particles are characterized online using a scanning mobility particle sizer (SMPS) and off-line using electron microscopy. The relation between the confinement force and the factors affecting the crumpled structure is established. Furthermore, to expand the application horizons of the structure, crumpled GO–TiO{sub 2} nanocomposites are synthesized. The method described here allows a simple and controlled production of graphene-based particles/composites with direct deposition onto any kind of substrate for a variety of applications.

Dynamics of solvation and desolvation of rubidium attached to He nanodroplets

International Nuclear Information System (INIS)

Vangerow, J. von; John, O.; Stienkemeier, F.; Mudrich, M.

2015-01-01

The real-time dynamics of photoexcited and photoionized rubidium (Rb) atoms attached to helium (He) nanodroplets is studied by femtosecond pump-probe mass spectrometry. While excited Rb atoms in the perturbed 6p-state (Rb * ) desorb off the He droplets, Rb + photoions tend to sink into the droplet interior when created near the droplet surface. The transition from Rb + solvation to full Rb * desorption is found to occur at a delay time τ ∼ 600 fs for Rb * in the 6pΣ-state and τ ∼ 1200 fs for the 6pΠ-state. Rb + He ions are found to be created by directly exciting bound Rb * He exciplex states as well as by populating bound Rb + He-states in a photoassociative ionization process

Dynamics of solvation and desolvation of rubidium attached to He nanodroplets

Science.gov (United States)

von Vangerow, J.; John, O.; Stienkemeier, F.; Mudrich, M.

2015-07-01

The real-time dynamics of photoexcited and photoionized rubidium (Rb) atoms attached to helium (He) nanodroplets is studied by femtosecond pump-probe mass spectrometry. While excited Rb atoms in the perturbed 6p-state (Rb*) desorb off the He droplets, Rb+ photoions tend to sink into the droplet interior when created near the droplet surface. The transition from Rb+ solvation to full Rb* desorption is found to occur at a delay time τ ˜ 600 fs for Rb* in the 6pΣ-state and τ ˜ 1200 fs for the 6pΠ-state. Rb+He ions are found to be created by directly exciting bound Rb*He exciplex states as well as by populating bound Rb+He-states in a photoassociative ionization process.

Laser absorption spectroscopy of water vapor confined in nanoporous alumina: wall collision line broadening and gas diffusion dynamics.

Science.gov (United States)

Svensson, Tomas; Lewander, Märta; Svanberg, Sune

2010-08-02

We demonstrate high-resolution tunable diode laser absorption spectroscopy (TDLAS) of water vapor confined in nanoporous alumina. Strong multiple light scattering results in long photon pathlengths (1 m through a 6 mm sample). We report on strong line broadening due to frequent wall collisions (gas-surface interactions). For the water vapor line at 935.685 nm, the HWHM of confined molecules are about 4.3 GHz as compared to 2.9 GHz for free molecules (atmospheric pressure). Gas diffusion is also investigated, and in contrast to molecular oxygen (that moves rapidly in and out of the alumina), the exchange of water vapor is found very slow.

Mesoscale simulations of confined Nafion thin films

Science.gov (United States)

Vanya, P.; Sharman, J.; Elliott, J. A.

2017-12-01

The morphology and transport properties of thin films of the ionomer Nafion, with thicknesses on the order of the bulk cluster size, have been investigated as a model system to explain the anomalous behaviour of catalyst/electrode-polymer interfaces in membrane electrode assemblies. We have employed dissipative particle dynamics (DPD) to investigate the interaction of water and fluorocarbon chains, with carbon and quartz as confining materials, for a wide range of operational water contents and film thicknesses. We found confinement-induced clustering of water perpendicular to the thin film. Hydrophobic carbon forms a water depletion zone near the film interface, whereas hydrophilic quartz results in a zone with excess water. There are, on average, oscillating water-rich and fluorocarbon-rich regions, in agreement with experimental results from neutron reflectometry. Water diffusivity shows increasing directional anisotropy of up to 30% with decreasing film thickness, depending on the hydrophilicity of the confining material. A percolation analysis revealed significant differences in water clustering and connectivity with the confining material. These findings indicate the fundamentally different nature of ionomer thin films, compared to membranes, and suggest explanations for increased ionic resistances observed in the catalyst layer.

Water confinement effects on fuel assembly motion and damping

International Nuclear Information System (INIS)

Brenneman, B.; Shah, S.J.; Williams, G.T.; Strumpell, J.H.

2003-01-01

It has been established by other authors that the accelerations of the water confined by the reactor core baffle plates has a significant effect on the responses of all the fuel assemblies during LOCA or seismic transients. This particular effect is a consequence of the water being essentially incompressible, and thus experiencing the same horizontal accelerations as the imposed baffle plate motions. These horizontal accelerations of the fluid induce lateral pressure gradients that cause horizontal buoyancy forces on any submerged structures. These forces are in the same direction as the baffle accelerations and, for certain frequencies at least, tend to reduce the relative displacements between the fuel and baffle plates. But there is another confinement effect - the imposed baffle plate velocities must also be transmitted to the water. If the fuel assembly grid strips are treated as simple hydro-foils, these horizontal velocity components change the fluid angle of attack on each strip, and thus may induce large horizontal lift forces on each grid in the same direction as the baffle plate velocity. There is a similar horizontal lift due to inclined flow over the rods when axial flow is present. These combined forces appear to always reduce the relative displacements between the fuel and baffle plates for any significant axial flow velocity. Modeling this effect is very simple. It was shown in previous papers that the mechanism for the large fuel assembly damping due to axial flow may be the hydrodynamic forces on the grid strips, and that this is very well represented by discrete viscous dampers at each grid elevation. To include the imposed horizontal water velocity effects, on both the grids and rods, these dampers are simply attached to the baffle plate rather than 'ground'. The large flow-induced damping really acts in a relative reference frame rather than an absolute or inertial reference frame, and thus it becomes a flow-induced coupling between the fuel

Dynamics of photoexcited Ba+ cations in 4He nanodroplets

International Nuclear Information System (INIS)

2UB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain))" data-affiliation=" (Departament ECM, Facultat de Física, and IN2UB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain))" >Leal, Antonio; 2UB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain))" data-affiliation=" (Departament ECM, Facultat de Física, and IN2UB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain))" >Pi, Martí; Zhang, Xiaohang; Drabbels, Marcel; 2UB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain); Laboratoire des Collisions, Agrégats, Réactivité, IRSAMC, UMR 5589, CNRS et Université Paul Sabatier-Toulouse 3, 118 route de Narbonne, F-31062 Toulouse Cedex 09 (France))" data-affiliation=" (Departament ECM, Facultat de Física, and IN2UB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain); Laboratoire des Collisions, Agrégats, Réactivité, IRSAMC, UMR 5589, CNRS et Université Paul Sabatier-Toulouse 3, 118 route de Narbonne, F-31062 Toulouse Cedex 09 (France))" >Barranco, Manuel; Cargnoni, Fausto; Hernando, Alberto; Mateo, David; Mella, Massimo

2016-01-01

We present a joint experimental and theoretical study on the desolvation of Ba + cations in 4 He nanodroplets excited via the 6p ← 6s transition. The experiments reveal an efficient desolvation process yielding mainly bare Ba + cations and Ba + He n exciplexes with n = 1 and 2. The speed distributions of the ions are well described by Maxwell-Boltzmann distributions with temperatures ranging from 60 to 178 K depending on the excitation frequency and Ba + He n exciplex size. These results have been analyzed by calculations based on a time-dependent density functional description for the helium droplet combined with classical dynamics for the Ba + . In agreement with experiment, the calculations reveal the dynamical formation of exciplexes following excitation of the Ba + cation. In contrast to experimental observation, the calculations do not reveal desolvation of excited Ba + cations or exciplexes, even when relaxation pathways to lower lying states are included.

Chitosan-shelled oxygen-loaded nanodroplets abrogate hypoxia dysregulation of human keratinocyte gelatinases and inhibitors: New insights for chronic wound healing

Energy Technology Data Exchange (ETDEWEB)

Khadjavi, Amina [Dipartimento di Neuroscienze, Università di Torino, Torino (Italy); Magnetto, Chiara [Istituto Nazionale di Ricerca Metrologica (INRIM), Torino (Italy); Panariti, Alice [Dipartimento di Scienze della Salute, Università di Milano Bicocca, Monza (Italy); Argenziano, Monica [Dipartimento di Scienza e Tecnologia del Farmaco, Università di Torino, Torino (Italy); Gulino, Giulia Rossana [Dipartimento di Oncologia, Università di Torino, Torino (Italy); Rivolta, Ilaria [Dipartimento di Scienze della Salute, Università di Milano Bicocca, Monza (Italy); Cavalli, Roberta [Dipartimento di Scienza e Tecnologia del Farmaco, Università di Torino, Torino (Italy); Giribaldi, Giuliana [Dipartimento di Oncologia, Università di Torino, Torino (Italy); Guiot, Caterina [Dipartimento di Neuroscienze, Università di Torino, Torino (Italy); Prato, Mauro, E-mail: mauro.prato@unito.it [Dipartimento di Neuroscienze, Università di Torino, Torino (Italy); Dipartimento di Scienze della Sanità Pubblica e Pediatriche, Università di Torino, Torino (Italy)

2015-08-01

Background: : In chronic wounds, efficient epithelial tissue repair is hampered by hypoxia, and balances between the molecules involved in matrix turn-over such as matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are seriously impaired. Intriguingly, new oxygenating nanocarriers such as 2H,3H-decafluoropentane-based oxygen-loaded nanodroplets (OLNs) might effectively target chronic wounds. Objective: : To investigate hypoxia and chitosan-shelled OLN effects on MMP/TIMP production by human keratinocytes. Methods: : HaCaT cells were treated for 24 h with 10% v/v OLNs both in normoxia or hypoxia. Cytotoxicity and cell viability were measured through biochemical assays; cellular uptake by confocal microscopy; and MMP and TIMP production by enzyme-linked immunosorbent assay or gelatin zymography. Results: : Normoxic HaCaT cells constitutively released MMP-2, MMP-9, TIMP-1 and TIMP-2. Hypoxia strongly impaired MMP/TIMP balances by reducing MMP-2, MMP-9, and TIMP-2, without affecting TIMP-1 release. After cellular uptake by keratinocytes, nontoxic OLNs abrogated all hypoxia effects on MMP/TIMP secretion, restoring physiological balances. OLN abilities were specifically dependent on time-sustained oxygen diffusion from OLN core. Conclusion: : Chitosan-shelled OLNs effectively counteract hypoxia-dependent dysregulation of MMP/TIMP balances in human keratinocytes. Therefore, topical administration of exogenous oxygen, properly encapsulated in nanodroplet formulations, might be a promising adjuvant approach to promote healing processes in hypoxic wounds. - Highlights: • Hypoxia impairs MMP9/TIMP1 and MMP2/TIMP2 balances in HaCaT human keratinocytes. • Chitosan-shelled oxygen-loaded nanodroplets (OLNs) are internalised by HaCaT cells. • OLNs are not toxic to HaCaT cells. • OLNs effectively counteract hypoxia effects on MMP/TIMP balances in HaCaT cells. • OLNs appear as promising and cost-effective therapeutic tools for hypoxic

Chitosan-shelled oxygen-loaded nanodroplets abrogate hypoxia dysregulation of human keratinocyte gelatinases and inhibitors: New insights for chronic wound healing

International Nuclear Information System (INIS)

Khadjavi, Amina; Magnetto, Chiara; Panariti, Alice; Argenziano, Monica; Gulino, Giulia Rossana; Rivolta, Ilaria; Cavalli, Roberta; Giribaldi, Giuliana; Guiot, Caterina; Prato, Mauro

2015-01-01

Background: : In chronic wounds, efficient epithelial tissue repair is hampered by hypoxia, and balances between the molecules involved in matrix turn-over such as matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are seriously impaired. Intriguingly, new oxygenating nanocarriers such as 2H,3H-decafluoropentane-based oxygen-loaded nanodroplets (OLNs) might effectively target chronic wounds. Objective: : To investigate hypoxia and chitosan-shelled OLN effects on MMP/TIMP production by human keratinocytes. Methods: : HaCaT cells were treated for 24 h with 10% v/v OLNs both in normoxia or hypoxia. Cytotoxicity and cell viability were measured through biochemical assays; cellular uptake by confocal microscopy; and MMP and TIMP production by enzyme-linked immunosorbent assay or gelatin zymography. Results: : Normoxic HaCaT cells constitutively released MMP-2, MMP-9, TIMP-1 and TIMP-2. Hypoxia strongly impaired MMP/TIMP balances by reducing MMP-2, MMP-9, and TIMP-2, without affecting TIMP-1 release. After cellular uptake by keratinocytes, nontoxic OLNs abrogated all hypoxia effects on MMP/TIMP secretion, restoring physiological balances. OLN abilities were specifically dependent on time-sustained oxygen diffusion from OLN core. Conclusion: : Chitosan-shelled OLNs effectively counteract hypoxia-dependent dysregulation of MMP/TIMP balances in human keratinocytes. Therefore, topical administration of exogenous oxygen, properly encapsulated in nanodroplet formulations, might be a promising adjuvant approach to promote healing processes in hypoxic wounds. - Highlights: • Hypoxia impairs MMP9/TIMP1 and MMP2/TIMP2 balances in HaCaT human keratinocytes. • Chitosan-shelled oxygen-loaded nanodroplets (OLNs) are internalised by HaCaT cells. • OLNs are not toxic to HaCaT cells. • OLNs effectively counteract hypoxia effects on MMP/TIMP balances in HaCaT cells. • OLNs appear as promising and cost-effective therapeutic tools for hypoxic

Experimental characterization of the concrete behaviour under high confinement: influence of the saturation ratio and of the water/cement ratio

International Nuclear Information System (INIS)

Vu, X.H.

2007-08-01

The objective of this thesis is to experimentally characterize the influence of the saturation ratio and of the water/cement ratio of concrete on its behaviour under high confinement. This thesis lies within a more general scope of the understanding of concrete behaviour under severe loading situations (near field detonation or ballistic impacts). A near field detonation or an impact on a concrete structure generate very high levels of stress associated with complex loading paths in the concrete material. To validate concrete behaviour models, experimental results are required. The work presented in this thesis concerns tests conducted using a static triaxial press that allows to obtain stress levels of the order of the giga Pascal. The porous character of concrete and the high confinement required on the one hand, a development of a specimen protection device, and on the other hand, a development of an instrumentation with strain gauges, which is unprecedented for such high confinements. Hydrostatic and triaxial tests, conducted on the one hand on model materials and on the other hand on concrete, allowed to validate the developed experimental procedures as well as the technique of strain and stress measurements. The studies concerning the influence of the saturation ratio and of the water/cement ratio of concrete on its behaviour required the formulation of a plain baseline concrete and of two modified concretes with different water/cement ratios. The analysis of triaxial tests performed on the baseline concrete shows that the saturation ratio of concrete has a major influence on its static behaviour under high confinement. This influence is particularly marked for the concrete loading capacity and for the shape of limit state curves for saturation ratios greater than 50%. The concrete loading capacity increases with the confinement pressure for tests on dry concrete whereas beyond a given confinement pressure, it remains limited for wet or saturated concrete

Dynamics of solvation and desolvation of rubidium attached to He nanodroplets

Energy Technology Data Exchange (ETDEWEB)

Vangerow, J. von; John, O.; Stienkemeier, F.; Mudrich, M., E-mail: mudrich@physik.uni-freiburg.de [Physikalisches Institut, Universität Freiburg, 79104 Freiburg (Germany)

2015-07-21

The real-time dynamics of photoexcited and photoionized rubidium (Rb) atoms attached to helium (He) nanodroplets is studied by femtosecond pump-probe mass spectrometry. While excited Rb atoms in the perturbed 6p-state (Rb{sup *}) desorb off the He droplets, Rb{sup +} photoions tend to sink into the droplet interior when created near the droplet surface. The transition from Rb{sup +} solvation to full Rb{sup *} desorption is found to occur at a delay time τ ∼ 600 fs for Rb{sup *} in the 6pΣ-state and τ ∼ 1200 fs for the 6pΠ-state. Rb{sup +}He ions are found to be created by directly exciting bound Rb{sup *}He exciplex states as well as by populating bound Rb{sup +}He-states in a photoassociative ionization process.

Helium nanodroplets. Pump-probe ionization of alkali dopings and spin-echo scattering on undoped drops; Helium-Nanotroepfchen. Pump-Probe-Ionisation von Alkalidotierungen und Spinechostreuung an undotierten Tropfen

Energy Technology Data Exchange (ETDEWEB)

Droppelmann, G.

2005-09-15

In the framework of this thesis several aspects of the properties of helium nanodroplets and their dopings. The formation of the exciplexes RbHe and KHe on helium droplets was studied by means of pump-probe ionization in real time, whereby the main interest lied on the influence of the applied helium isotopes. The experiments with cesium atoms on the droplet surface aimed on the elucidation of the relaxation dynamics of the surface under regardment both of isotope and size effects. From the pump-probe measurements on the formation of the exciplex RbHe on helium nanodroplets performed in the framework of this thesis formation times of 8.5 ps for Rb{sup 4}He and 11.6 ps for Rb{sup 3}He resulted.

Aquifer Storage Recovery (ASR) of chlorinated municipal drinking water in a confined aquifer

Science.gov (United States)

Izbicki, John A.; Petersen, Christen E.; Glotzbach, Kenneth J.; Metzger, Loren F.; Christensen, Allen H.; Smith, Gregory A.; O'Leary, David R.; Fram, Miranda S.; Joseph, Trevor; Shannon, Heather

2010-01-01

About 1.02 x 106 m3 of chlorinated municipal drinking water was injected into a confined aquifer, 94-137 m below Roseville, California, between December 2005 and April 2006. The water was stored in the aquifer for 438 days, and 2.64 x 106 m3 of water were extracted between July 2007 and February 2008. On the basis of Cl data, 35% of the injected water was recovered and 65% of the injected water and associated disinfection by-products (DBPs) remained in the aquifer at the end of extraction. About 46.3 kg of total trihalomethanes (TTHM) entered the aquifer with the injected water and 37.6 kg of TTHM were extracted. As much as 44 kg of TTHMs remained in the aquifer at the end of extraction because of incomplete recovery of injected water and formation of THMs within the aquifer by reactions with freechlorine in the injected water. Well-bore velocity log data collected from the Aquifer Storage Recovery (ASR) well show as much as 60% of the injected water entered the aquifer through a 9 m thick, high-permeability layer within the confined aquifer near the top of the screened interval. Model simulations of ground-water flow near the ASR well indicate that (1) aquifer heterogeneity allowed injected water to move rapidly through the aquifer to nearby monitoring wells, (2) aquifer heterogeneity caused injected water to move further than expected assuming uniform aquifer properties, and (3) physical clogging of high-permeability layers is the probable cause for the observed change in the distribution of borehole flow. Aquifer heterogeneity also enhanced mixing of native anoxic ground water with oxic injected water, promoting removal of THMs primarily through sorption. A 3 to 4-fold reduction in TTHM concentrations was observed in the furthest monitoring well 427 m downgradient from the ASR well, and similar magnitude reductions were observed in depth-dependent water samples collected from the upper part of the screened interval in the ASR well near the end of the extraction

Fragmentation dynamics of ionized neon trimer inside helium nanodroplets: a theoretical study.

Science.gov (United States)

Bonhommeau, David; Viel, Alexandra; Halberstadt, Nadine

2004-06-22

We report a theoretical study of the fragmentation dynamics of Ne(3) (+) inside helium nanodroplets, following vertical ionization of the neutral neon trimer. The motion of the neon atoms is treated classically, while transitions between the electronic states of the ionic cluster are treated quantum mechanically. A diatomics-in-molecules description of the potential energy surfaces is used, in a minimal basis set consisting of three effective p orbitals on each neon atom for the missing electron. The helium environment is modeled by a friction force acting on the neon atoms when their speed exceeds the Landau velocity. A reasonable range of values for the corresponding friction coefficient is obtained by comparison with existing experimental measurements. (c) 2004 American Institute of Physics.

Effects of acute temperature change, confinement and housing on plasma corticosterone in water snakes, Nerodia sipedon (Colubridae: Natricinae).

Science.gov (United States)

Sykes, Kyle Lea; Klukowski, Matthew

2009-03-01

Body temperature affects many aspects of reptilian behavior and physiology, but its effect on hormonal secretion has been little studied, especially in snakes. Major objectives of this study were to determine if acute changes in body temperature during confinement influenced plasma corticosterone levels and if initial body temperatures upon capture in the field were related to baseline corticosterone levels in water snakes (Nerodia sipedon). Water snakes were bled upon capture in the field and after one hour of confinement in a cooled, control, or heated incubator. Since little is known about the potential metabolic changes in response to stress in reptiles, plasma triglyceride levels were also measured. Upon completion of the field study, snakes were housed for 5-8 days without food to determine the effect of chronic stress on both corticosterone and triglyceride levels. Plasma corticosterone concentrations were measured using enzyme-linked immunosorbant assay (ELISA) and plasma triglycerides were determined enzymatically. In the field, experimental alterations of body temperature during confinement had no effect on corticosterone levels. Similarly, there was no correlation between initial body temperature and baseline plasma corticosterone concentrations. However, post-confinement corticosterone levels were approximately three-times greater in females than males. Plasma triglyceride levels were not affected by temperature treatment, confinement, or sex. Compared to field values, both baseline and post-confinement corticosterone levels were elevated after the chronic stress of short-term laboratory housing but triglyceride levels decreased. Overall, these results indicate that sex but not body temperature has a major influence on the adrenocortical stress response in Nerodia sipedon.

The Quantum Mechanics of Nano-Confined Water: New Cooperative Effects Revealed with Neutron and X-Ray Compton Scattering

International Nuclear Information System (INIS)

Reiter, G F; Deb, Aniruddha

2014-01-01

Neutron Compton scattering(NCS) measurements of the momentum distribution of light ions using the Vesuvio instrument at ISIS provide a sensitive local probe of the environment of those ions. NCS measurements of the proton momentum distribution in bulk water show only small deviations from the usual picture of water as a collection of molecules, with the protons covalently bonded to an oxygen and interacting weakly, primarily electrostatically, with nearby molecules. However, a series of measurements of the proton momentum distribution in carbon nanotubes, xerogel, and Nafion show that the proton delocalizes over distances of 0.2-0.3Å when water is confined on the scale of 20Å. This delocalization must be the result of changes in the Born-Oppenheimer surface for the protons, which would imply that there are large deviations in the electron distribution from that of a collection of weakly interacting molecules. This has been observed at Spring-8 using x-ray Compton scattering. The observed deviation in the valence electron momentum distribution from that of bulk water is more than an order of magnitude larger than the change observed in bulk water as the water is heated from just above melting to just below boiling. We conclude that the protons and electrons in nano-confined water are in a qualitatively different ground state from that of bulk water. Since the properties of this state persist at room temperature, and the confinement distance necessary to observe it is comparable to the distance between the elements of biological cells, this state presumably plays a role in the functioning of those cells

Fragmentation dynamics of ionized neon clusters (Ne(n), n=3-14) embedded in helium nanodroplets.

Science.gov (United States)

Bonhommeau, David; Halberstadt, Nadine; Viel, Alexandra

2006-01-14

We report a theoretical study of the nonadiabatic fragmentation dynamics of ionized neon clusters embedded in helium nanodroplets for cluster sizes up to n=14 atoms. The dynamics of the neon atoms is modeled using the molecular dynamics with quantum transitions method of Tully [J. Chem. Phys. 93, 1061 (1990)] with the nuclei treated classically and transitions between electronic states quantum mechanically. The potential-energy surfaces are derived from a diatomics-in-molecules model to which induced dipole-induced dipole interactions are added. The effect of the spin-orbit interaction is also discussed. The helium environment is modeled by a friction force acting on charged atoms whose speed exceeds the critical Landau velocity. The dependence of the fragment size distribution on the friction strength and on the initial nanodroplet size is investigated. By comparing with the available experimental data obtained for Ne3+ and Ne4+, a reasonable value for the friction coefficient, the only parameter of the model, is deduced. This value is then used to predict the effect of the helium environment on the dissociation dynamics of larger neon clusters, n=5-14. The results show stabilization of larger fragments than in the gas phase, but fragmentation is not completely caged. In addition, two types of dynamics are characterized for Ne4+: fast and explosive, therefore leaving no time for friction to cool down the process when dynamics starts on one of the highest electronic states, and slower, therefore leading to some stabilization by helium when it starts on one of the lowest electronic states.

Structure and phase behavior of a confined nanodroplet composed of the flexible chain molecules.

Science.gov (United States)

Kim, Soon-Chul; Kim, Eun-Young; Seong, Baek-Seok

2011-04-28

A polymer density functional theory has been employed for investigating the structure and phase behaviors of the chain polymer, which is modelled as the tangentially connected sphere chain with an attractive interaction, inside the nanosized pores. The excess free energy of the chain polymer has been approximated as the modified fundamental measure-theory for the hard spheres, the Wertheim's first-order perturbation for the chain connectivity, and the mean-field approximation for the van der Waals contribution. For the value of the chemical potential corresponding to a stable liquid phase in the bulk system and a metastable vapor phase, the flexible chain molecules undergo the liquid-vapor transition as the pore size is reduced; the vapor is the stable phase at small volume, whereas the liquid is the stable phase at large volume. The wide liquid-vapor coexistence curve, which explains the wide range of metastable liquid-vapor states, is observed at low temperature. The increase of temperature and decrease of pore size result in a narrowing of liquid-vapor coexistence curves. The increase of chain length leads to a shift of the liquid-vapor coexistence curve towards lower values of chemical potential. The coexistence curves for the confined phase diagram are contained within the corresponding bulk liquid-vapor coexistence curve. The equilibrium capillary phase transition occurs at a higher chemical potential than in the bulk phase.

Studies on chemical phenomena of high concentration tritium water and organic compounds of tritium from viewpoint of the tritium confinement

International Nuclear Information System (INIS)

Yamanishi, Toshihiko; Hayashi, Takumi; Iwai, Yasunori; Isobe, Kanetsugu; Hara, Masanori; Sugiyama, Takahiko; Okuno, Kenji

2009-01-01

As a part of the grant-in-aid for scientific research on priority areas entitled 'frontiers of tritium researches toward fusion reactors', coordinated two research programs on chemical phenomena of high concentration tritium water and organic compounds of tritium from view point of the tritium confinement have been conducted by the C01 team. The results are summarized as follows: (1) Chemical effects of the high concentration tritium water on stainless steels as structural materials of fusion reactors were investigated. Basic data on tritium behaviors at the metal-water interface and corrosion of metal in tritium water were obtained. (2) Development of the tritium confinement and extraction system for the circulating cooling water in the fusion reactor was studied. Improvement was obtained in the performance of a chemical exchange column and catalysts as major components of the water processing system. (J.P.N.)

Molecular dynamics simulations of proton-ordered water confined in low-diameter carbon nanotubes.

Science.gov (United States)

Li, Shujuan; Schmidt, Burkhard

2015-03-21

The present work deals with molecular dynamics simulations of water confined in single-walled carbon nanotubes (CNTs), with emphasis on the proton-ordering of water and its polarization. First, the water occupancy of open-ended armchair and zigzag CNTs immersed in water under ambient NPT conditions is calculated for various water models, and for varying Lennard-Jones parameters of the water-carbon interaction. As a function of the CNT diameter, the water density displays several oscillations before converging to the bulk value. Based on these results, the water structures encapsulated in 10 nm long armchair CNTs (n,n) with 5 ≤ n ≤ 10, are investigated under NVT conditions. Inside the smallest nanotubes (n = 5, 6) highly ferroelectric (FE), quasi-one-dimensional water chains are found while inside the other CNTs water molecules assemble into single-walled ice nanotubes (INTs). There are several, near-degenerate minimum energy INT structures: single helical structures were found for 7 ≤ n ≤ 10, in all cases in FE arrangement. In addition, a double helical INT structure was found for n = 8 with an even higher polarization. Prism-like structures were found only for 8 ≤ n ≤ 10 with various FE, ferrielectric (FI), and antiferroelectric (AF, n = 9, 10) proton ordering. The coexistence of the nearly iso-energetic FE, FI, and AF INT structures separated by high barriers renders the molecular dynamics highly metastable, typically with nanosecond timescales at room temperature. Hence, the replica exchange simulation method is used to obtain populations of different INT states at finite temperatures. Many of the FE INT structures confined in low-diameter CNTs are still prevalent at room temperature. Both helix-helix and helix-prism structural transitions are detected which can be either continuous (around 470 K for n = 8) or discontinuous (at 218 K for n = 9). Also melting-like transitions are found in which the INT structures are disrupted leading to a loss of FE

Wet scrubber technology for tritium confinement at ITER

Energy Technology Data Exchange (ETDEWEB)

Perevezentsev, A.N., E-mail: alexander.perevezentsev@iter.org [ITER Organization, CS 90 046, 13067 St Paul lez Durance Cedex (France); Andreev, B.M.; Rozenkevich, M.B.; Pak, Yu.S.; Ovcharov, A.V.; Marunich, S.A. [Mendeleev University of Chemical Technology, 125047 Miusskaya Sq. 9, Moscow (Russian Federation)

2010-12-15

Operation of the ITER machine with tritium plasma requires tritium confinement systems to protect workers and the environment. Tritium confinement at ITER is based on multistage approach. The final stage provides tritium confinement in building sectors and consists of building's walls as physical barriers and control of sub-atmospheric pressure in those volumes as a dynamic barrier. The dynamic part of the confinement function shall be provided by safety important components that are available all the time when required. Detritiation of air prior to its release to the environment is based on catalytic conversion of tritium containing gaseous species to water vapour followed by their isotopic exchange with liquid water in scrubber column of packed bed type. Wet scrubber technology has been selected because of its advantages over conventional air detritiation technique based on gas drying by water adsorption. The most important design target of system availability was very difficult to meet with conventional water adsorption driers. This paper presents results of experimental trial for validation of wet scrubber technology application in the ITER tritium confinement system and process evaluation using developed simulation computer code.

Dextran-shelled oxygen-loaded nanodroplets reestablish a normoxia-like pro-angiogenic phenotype and behavior in hypoxic human dermal microvascular endothelium

International Nuclear Information System (INIS)

Basilico, Nicoletta; Magnetto, Chiara; D'Alessandro, Sarah; Panariti, Alice; Rivolta, Ilaria; Genova, Tullio; Khadjavi, Amina; Gulino, Giulia Rossana; Argenziano, Monica; Soster, Marco

2015-01-01

In chronic wounds, hypoxia seriously undermines tissue repair processes by altering the balances between pro-angiogenic proteolytic enzymes (matrix metalloproteinases, MMPs) and their inhibitors (tissue inhibitors of metalloproteinases, TIMPs) released from surrounding cells. Recently, we have shown that in human monocytes hypoxia reduces MMP-9 and increases TIMP-1 without affecting TIMP-2 secretion, whereas in human keratinocytes it reduces MMP-2, MMP-9, and TIMP-2, without affecting TIMP-1 release. Provided that the phenotype of the cellular environment is better understood, chronic wounds might be targeted by new oxygenating compounds such as chitosan- or dextran-shelled and 2H,3H-decafluoropentane-cored oxygen-loaded nanodroplets (OLNs). Here, we investigated the effects of hypoxia and dextran-shelled OLNs on the pro-angiogenic phenotype and behavior of human dermal microvascular endothelium (HMEC-1 cell line), another cell population playing key roles during wound healing. Normoxic HMEC-1 constitutively released MMP-2, TIMP-1 and TIMP-2 proteins, but not MMP-9. Hypoxia enhanced MMP-2 and reduced TIMP-1 secretion, without affecting TIMP-2 levels, and compromised cell ability to migrate and invade the extracellular matrix. When taken up by HMEC-1, nontoxic OLNs abrogated the effects of hypoxia, restoring normoxic MMP/TIMP levels and promoting cell migration, matrix invasion, and formation of microvessels. These effects were specifically dependent on time-sustained oxygen diffusion from OLN core, since they were not achieved by oxygen-free nanodroplets or oxygen-saturated solution. Collectively, these data provide new information on the effects of hypoxia on dermal endothelium and support the hypothesis that OLNs might be used as effective adjuvant tools to promote chronic wound healing processes. - Highlights: • Hypoxia enhances MMP-2 and reduces TIMP-1 secretion by dermal HMEC-1 cell line. • Hypoxia compromises migration and matrix invasion abilities of

Dextran-shelled oxygen-loaded nanodroplets reestablish a normoxia-like pro-angiogenic phenotype and behavior in hypoxic human dermal microvascular endothelium

Energy Technology Data Exchange (ETDEWEB)

Basilico, Nicoletta, E-mail: nicoletta.basilico@unimi.it [Dipartimento di Scienze Biomediche, Chirurgiche e Odontoiatriche, Università di Milano, via Pascal 36, 20133 Milano (Italy); Magnetto, Chiara, E-mail: c.magnetto@inrim.it [Istituto Nazionale di Ricerca Metrologica (INRIM), Strada delle Cacce, 91, 10135 Torino (Italy); D' Alessandro, Sarah, E-mail: sarah.dalessandro@unimi.it [Dipartimento di Scienze Farmacologiche e Biomolecolari, Università di Milano, via Pascal 36, 20133 Milano (Italy); Panariti, Alice, E-mail: alice.panariti@mail.mcgill.ca [Dipartimento di Scienze della Salute, Università di Milano Bicocca, Via Cadore 48, 20900 Monza (Italy); Rivolta, Ilaria, E-mail: ilaria.rivolta@unimib.it [Dipartimento di Scienze della Salute, Università di Milano Bicocca, Via Cadore 48, 20900 Monza (Italy); Genova, Tullio, E-mail: tullio.genova@unito.it [Dipartimento di Scienze della Vita e Biologia dei Sistemi, Via Accademia Albertina 13, 10123 Torino (Italy); Khadjavi, Amina, E-mail: amina.khadjavi@unito.it [Dipartimento di Neuroscienze, Università di Torino, Corso Raffaello 30, 10125 Torino (Italy); Gulino, Giulia Rossana, E-mail: giuliarossana.gulino@unito.it [Dipartimento di Oncologia, Università di Torino, Via Santena 5 bis, 10126 Torino (Italy); Argenziano, Monica, E-mail: monica.argenziano@unito.it [Dipartimento di Scienza e Tecnologia del Farmaco, Università di Torino, Via Giuria, 9, 10125 Torino (Italy); Soster, Marco, E-mail: marco.soster@unito.it [Dipartimento di Scienza e Tecnologia del Farmaco, Università di Torino, Via Giuria, 9, 10125 Torino (Italy); and others

2015-11-01

In chronic wounds, hypoxia seriously undermines tissue repair processes by altering the balances between pro-angiogenic proteolytic enzymes (matrix metalloproteinases, MMPs) and their inhibitors (tissue inhibitors of metalloproteinases, TIMPs) released from surrounding cells. Recently, we have shown that in human monocytes hypoxia reduces MMP-9 and increases TIMP-1 without affecting TIMP-2 secretion, whereas in human keratinocytes it reduces MMP-2, MMP-9, and TIMP-2, without affecting TIMP-1 release. Provided that the phenotype of the cellular environment is better understood, chronic wounds might be targeted by new oxygenating compounds such as chitosan- or dextran-shelled and 2H,3H-decafluoropentane-cored oxygen-loaded nanodroplets (OLNs). Here, we investigated the effects of hypoxia and dextran-shelled OLNs on the pro-angiogenic phenotype and behavior of human dermal microvascular endothelium (HMEC-1 cell line), another cell population playing key roles during wound healing. Normoxic HMEC-1 constitutively released MMP-2, TIMP-1 and TIMP-2 proteins, but not MMP-9. Hypoxia enhanced MMP-2 and reduced TIMP-1 secretion, without affecting TIMP-2 levels, and compromised cell ability to migrate and invade the extracellular matrix. When taken up by HMEC-1, nontoxic OLNs abrogated the effects of hypoxia, restoring normoxic MMP/TIMP levels and promoting cell migration, matrix invasion, and formation of microvessels. These effects were specifically dependent on time-sustained oxygen diffusion from OLN core, since they were not achieved by oxygen-free nanodroplets or oxygen-saturated solution. Collectively, these data provide new information on the effects of hypoxia on dermal endothelium and support the hypothesis that OLNs might be used as effective adjuvant tools to promote chronic wound healing processes. - Highlights: • Hypoxia enhances MMP-2 and reduces TIMP-1 secretion by dermal HMEC-1 cell line. • Hypoxia compromises migration and matrix invasion abilities of

Interaction of 3D dewetting nanodroplets on homogeneous and chemically heterogeneous substrates

International Nuclear Information System (INIS)

Asgari, M; Moosavi, A

2014-01-01

Long-time interaction of dewetting nanodroplets is investigated using a long-wave approximation method. Although three-dimensional (3D) droplets evolution dynamics exhibits qualitative behavior analogous to two-dimensional (2D) dynamics, there is an extensive quantitative difference between them. 3D dynamics is substantially faster than 2D dynamics. This can be related to the larger curvature and, as a consequence, the larger Laplace pressure difference between the droplets in 3D systems. The influence of various chemical heterogeneities on the behavior of droplets has also been studied. In the case of gradient surfaces, it is shown how the gradient direction could change the dynamics. For a chemical step located between the droplets, the dynamics is enhanced or weakened depending on the initial configuration of the system. (paper)

Experimental and theoretical total neutron scattering cross-section of water confined in silica microspheres

Energy Technology Data Exchange (ETDEWEB)

Muhrer, G., E-mail: muhrer@lanl.gov [Los Alamos National Laboratory, Los Alamos, 87545 NM (United States); Hartl, M.; Mocko, M.; Tovesson, F.; Daemen, L. [Los Alamos National Laboratory, Los Alamos, 87545 NM (United States)

2012-07-21

In the search for moderator materials encapsulated materials have been discussed, but very little is known regarding the effect of encapsulation on neutron moderation properties. As a first step toward a better understanding, we present the measured total neutron cross-section of water confined in silica microspheres and compare the measured data to the predicted theoretical cross-section.

Application of Confined Blasting in Water-Filled Deep Holes to Control Strong Rock Pressure in Hard Rock Mines

Directory of Open Access Journals (Sweden)

Jingxuan Yang

2017-11-01

Full Text Available In extra-thick coal seams, mining operations can lead to large-scale disturbances, complex overburden structures, and frequent and strong strata behavior in the stope, which are serious threats to mine safety. This study analyzed the overburden structure and strata behavior and proposed the technique of confined blasting in water-filled deep holes as a measure to prevent strong rock pressure. It found that there are two primary reasons for the high effectiveness of the proposed technique in presplitting hard coal and rock. First, the fracture water enables much more efficient transfer of dynamic load due to its incompressibility. Second, the subsequent expansion of water can further split the rock by compression. A mechanical model was used to reveal how the process of confined blasting in water-filled deep holes presplit roof. Moreover, practical implementation of this technique was found to improve the structure of hard, thick roof and prevent strong rock pressure, demonstrating its effectiveness in roof control.

Molecular Dynamics Simulations of Water Nanodroplets on Silica Surfaces

DEFF Research Database (Denmark)

Zambrano, Harvey A; Walther, Jens Honore; Jaffe, Richard L.

2009-01-01

and DNA microarrays technologies.4,5,6,7,8 Although extensive experimental, theoretical and computational work has been devoted to study the nature of the interaction between silica and water,2,9-16 at the molecular level a complete understanding of silica-water systems has not been reached. Contact angle...... computations of water droplets on silica surfaces offers a useful fundamental and quantitative measurement in order to study chemical and physical properties of water-silica systems.3,16,17,18 For hydrophobic systems the static and dynamic properties of the fluid-solid interface are influenced by the presence...

Communication: Fourier-transform infrared probing of remarkable quantities of gas trapped in cold homogeneously nucleated nanodroplets

Science.gov (United States)

Uras-Aytemiz, Nevin; Devlin, J. Paul

2013-07-01

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

Nanodroplet processing platform for deep and quantitative proteome profiling of 10-100 mammalian cells.

Science.gov (United States)

Zhu, Ying; Piehowski, Paul D; Zhao, Rui; Chen, Jing; Shen, Yufeng; Moore, Ronald J; Shukla, Anil K; Petyuk, Vladislav A; Campbell-Thompson, Martha; Mathews, Clayton E; Smith, Richard D; Qian, Wei-Jun; Kelly, Ryan T

2018-02-28

Nanoscale or single-cell technologies are critical for biomedical applications. However, current mass spectrometry (MS)-based proteomic approaches require samples comprising a minimum of thousands of cells to provide in-depth profiling. Here, we report the development of a nanoPOTS (nanodroplet processing in one pot for trace samples) platform for small cell population proteomics analysis. NanoPOTS enhances the efficiency and recovery of sample processing by downscaling processing volumes to 3000 proteins are consistently identified from as few as 10 cells. Furthermore, we demonstrate quantification of ~2400 proteins from single human pancreatic islet thin sections from type 1 diabetic and control donors, illustrating the application of nanoPOTS for spatially resolved proteome measurements from clinical tissues.

Dynamics of photoexcited Ba{sup +} cations in {sup 4}He nanodroplets

Energy Technology Data Exchange (ETDEWEB)

Leal, Antonio; Pi, Martí [Departament ECM, Facultat de Física, and IN" 2UB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain); Zhang, Xiaohang; Drabbels, Marcel [Laboratoire de Chimie Physique Moléculaire, Swiss Federal Institute of Technology Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Barranco, Manuel [Departament ECM, Facultat de Física, and IN" 2UB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain); Laboratoire des Collisions, Agrégats, Réactivité, IRSAMC, UMR 5589, CNRS et Université Paul Sabatier-Toulouse 3, 118 route de Narbonne, F-31062 Toulouse Cedex 09 (France); Cargnoni, Fausto [Istituto di Scienze e Tecnologie Molecolari (ISTM), Consiglio Nazionale delle Ricerche, via Golgi 19, 20133 Milano (Italy); Hernando, Alberto [Social Thermodynamics Applied Research (SThAR), EPFL Innovation Park, Bâtiment C, CH-1015 Lausanne (Switzerland); Mateo, David [Department of Chemistry and Biochemistry, California State University at Northridge, Northridge, California 91330 (United States); Mella, Massimo [Dipartimento di Scienza ed Alta Tecnologia, Università degli Studi dell’Insubria, via Valleggio 11, 22100 Como (Italy)

2016-03-07

We present a joint experimental and theoretical study on the desolvation of Ba{sup +} cations in {sup 4}He nanodroplets excited via the 6p ← 6s transition. The experiments reveal an efficient desolvation process yielding mainly bare Ba{sup +} cations and Ba{sup +}He{sub n} exciplexes with n = 1 and 2. The speed distributions of the ions are well described by Maxwell-Boltzmann distributions with temperatures ranging from 60 to 178 K depending on the excitation frequency and Ba{sup +} He{sub n} exciplex size. These results have been analyzed by calculations based on a time-dependent density functional description for the helium droplet combined with classical dynamics for the Ba{sup +}. In agreement with experiment, the calculations reveal the dynamical formation of exciplexes following excitation of the Ba{sup +} cation. In contrast to experimental observation, the calculations do not reveal desolvation of excited Ba{sup +} cations or exciplexes, even when relaxation pathways to lower lying states are included.

Confinement dependence of electro-catalysts for hydrogen evolution from water splitting

Directory of Open Access Journals (Sweden)

Mikaela Lindgren

2014-02-01

Full Text Available Density functional theory is utilized to articulate a particular generic deconstruction of the electrode/electro-catalyst assembly for the cathode process during water splitting. A computational model was designed to determine how alloying elements control the fraction of H2 released during zirconium oxidation by water relative to the amount of hydrogen picked up by the corroding alloy. This model is utilized to determine the efficiencies of transition metals decorated with hydroxide interfaces in facilitating the electro-catalytic hydrogen evolution reaction. A computational strategy is developed to select an electro-catalyst for hydrogen evolution (HE, where the choice of a transition metal catalyst is guided by the confining environment. The latter may be recast into a nominal pressure experienced by the evolving H2 molecule. We arrived at a novel perspective on the uniqueness of oxide supported atomic Pt as a HE catalyst under ambient conditions.

Biomechanical ordering and buckling due to microbial growth confined at oil-water interfaces

Science.gov (United States)

Juarez, Gabriel; Stocker, Roman

2015-11-01

Bacteria are unicellular organisms that often exist as densely populated, surface-associated communities. Bacteria are also environmental colloids and spontaneously attach and self-assemble at liquid-liquid interfaces. Here, we present results on the growth dynamics of individual rod-shaped bacteria confined to finite oil-water interfaces of varying curvature. Through experiments using microfluidic chambers and time-lapse microscopy, we study the formation of macroscopic structures observed as adsorbed bacteria grow, divide, and self-assemble in a nematic phase due to biomechanical interactions. The continued growth at the interface leads to a jammed monolayer of cells, which then causes the interface to buckle and undergo large deformations including wrinkling and tubulation. These observations highlight the interplay between physical environment, such as confinement and interface curvature, and active biological processes, such as growth, at the scale of individual agents and shape our understanding of macroscale processes such as microbial degradation of oil in the ocean.

Dynamics of water clusters confined in proteins: a molecular dynamics simulation study of interfacial waters in a dimeric hemoglobin.

Science.gov (United States)

Gnanasekaran, Ramachandran; Xu, Yao; Leitner, David M

2010-12-23

Water confined in proteins exhibits dynamics distinct from the dynamics of water in the bulk or near the surface of a biomolecule. We examine the water dynamics at the interface of the two globules of the homodimeric hemoglobin from Scapharca inaequivalvis (HbI) by molecular dynamics (MD) simulations, with focus on water-protein hydrogen bond lifetimes and rotational anisotropy of the interfacial waters. We find that relaxation of the waters at the interface of both deoxy- and oxy-HbI, which contain a cluster of 17 and 11 interfacial waters, respectively, is well described by stretched exponentials with exponents from 0.1 to 0.6 and relaxation times of tens to thousands of picoseconds. The interfacial water molecules of oxy-HbI exhibit slower rotational relaxation and hydrogen bond rearrangement than those of deoxy-HbI, consistent with an allosteric transition from unliganded to liganded conformers involving the expulsion of several water molecules from the interface. Though the interfacial waters are translationally and rotationally static on the picosecond time scale, they contribute to fast communication between the globules via vibrations. We find that the interfacial waters enhance vibrational energy transport across the interface by ≈10%.

Effect of laser peening with glycerol as plasma confinement layer

Science.gov (United States)

Tsuyama, Miho; Ehara, Naoya; Yamashita, Kazuma; Heya, Manabu; Nakano, Hitoshi

2018-03-01

The effects of controlling the plasma confinement layer on laser peening were investigated by measuring the hardness and residual stress of laser-peened stainless steels. The plasma confinement layer contributes to increasing the pressure of shock waves by suppressing the expansion of the laser-produced plasma. Most previous studies on laser peening have employed water as the plasma confinement layer. In this study, a glycerol solution is used in the context of a large acoustic impedance. It is found that this glycerol solution is superior to water in its ability to confine plasma and that suitable conditions exist for the glycerol solution to act as a plasma confinement layer to achieve efficient laser peening.

Oil Contact Angles in a Water-Decane-Silicon Dioxide System: Effects of Surface Charge.

Science.gov (United States)

Xu, Shijing; Wang, Jingyao; Wu, Jiazhong; Liu, Qingjie; Sun, Chengzhen; Bai, Bofeng

2018-04-19

Oil wettability in the water-oil-rock systems is very sensitive to the evolution of surface charges on the rock surfaces induced by the adsorption of ions and other chemical agents in water flooding. Through a set of large-scale molecular dynamics simulations, we reveal the effects of surface charge on the oil contact angles in an ideal water-decane-silicon dioxide system. The results show that the contact angles of oil nano-droplets have a great dependence on the surface charges. As the surface charge density exceeds a critical value of 0.992 e/nm 2 , the contact angle reaches up to 78.8° and the water-wet state is very apparent. The variation of contact angles can be confirmed from the number density distributions of oil molecules. With increasing the surface charge density, the adsorption of oil molecules weakens and the contact areas between nano-droplets and silicon dioxide surface are reduced. In addition, the number density distributions, RDF distributions, and molecular orientations indicate that the oil molecules are adsorbed on the silicon dioxide surface layer-by-layer with an orientation parallel to the surface. However, the layered structure of oil molecules near the silicon dioxide surface becomes more and more obscure at higher surface charge densities.

Confinement Effects on Chemical Equilibria: Pentacyano(PyrazineFerrate(II Stability Changes within Nanosized Droplets of Water

Directory of Open Access Journals (Sweden)

Teofilo Borunda

2018-04-01

Full Text Available Nanoscale confinement is known to impact properties of molecules and we observed changes in the reactivity of an iron coordination complex, pentacyano(pyrazineferrate(II. The confinement of two coordination complexes in a sodium AOT/isooctane reverse micellar (RM water droplet was found to dramatically increase the hydrolysis rate of [Fe(CN5pyz]3− and change the monomer-dimer equilibria between [Fe(CN5pyz]3− and [Fe2(CN10pyz]6−. Combined UV-Vis and 1H-NMR spectra of these complexes in RMs were analyzed and the position of the monomer-dimer equilibrium and the relative reaction times were determined at three different RM sizes. The data show that the hydrolysis rates (loss of pyrazine are dramatically enhanced in RMs over bulk water and increase as the size of the RM decreases. Likewise, the monomer-dimer equilibrium changes to favor the formation of dimer as the RM size decreases. We conclude that the effects of the [Fe(CN5pyz]3− stability is related to its solvation within the RM.

Dynamics of metal nanodroplets; Dynamik metallischer Nanotroepfchen

Energy Technology Data Exchange (ETDEWEB)

Habenicht, Anja

2007-11-12

In this work flat metal nanostructures on inert substrates like glass, silicon or graphite have been illuminated by single intensive laser pulses with fluences above the melting threshold. The liquid structures produced in this way are far from their equilibrium shape and a dewetting process starts. On a timescale of a few nanoseconds, the liquid but still flat nanostructure transforms toward a sphere. During this deformation the center of mass moves upward, which can lead to detachment of droplets from the surface due to inertia. The velocity of the detaching nanodroplets is measured with a light barrier technique. The experiment shows that the velocity of the detached droplet is constant over a large range of laser energy densities. This supports the model of a dewetting driven process: The droplet gains surface energy by transforming toward a sphere which is then converted into kinetic energy. Loss mechanisms like excitation of droplet oscillations and dissipation due to viscous friction are discussed. With this model the escape velocity was predicted for nanostructures of different materials and forms, hence other material parameters like surface tension or density and has been confirmed experimentally. The droplets are landed on another surface. Two scenarios are found: There are spheres with a similar shape as the droplet or heavily deformed structures. These structures of splashing and rebounding are identical to the structures which can be observed in the macroscopic impact of liquids. The two scenarios can be explained by different temperatures of the droplets when reaching the substrate. (orig.)

The hydrophobic effect: Molecular dynamics simulations of water confined between extended hydrophobic and hydrophilic surfaces

DEFF Research Database (Denmark)

Jensen, Morten Østergaard; Mouritsen, Ole G.; Peters, Günther H.J.

2004-01-01

Structural and dynamic properties of water confined between two parallel, extended, either hydrophobic or hydrophilic crystalline surfaces of n-alkane C36H74 or n-alcohol C35H71OH, are studied by molecular dynamics simulations. Electron density profiles, directly compared with corresponding......-correlation functions reveal that water molecules have characteristic diffusive behavior and orientational ordering due to the lack of hydrogen bonding interactions with the surface. These observations suggest that the altered dynamical properties of water in contact with extended hydrophobic surfaces together...... at both surfaces. The ordering is characteristically different between the surfaces and of longer range at the hydrophilic surface. Furthermore, the dynamic properties of water are different at the two surfaces and different from the bulk behavior. In particular, at the hydrophobic surface, time...

Enhanced ionic liquid mobility induced by confinement in 1D CNT membranes

Science.gov (United States)

Berrod, Q.; Ferdeghini, F.; Judeinstein, P.; Genevaz, N.; Ramos, R.; Fournier, A.; Dijon, J.; Ollivier, J.; Rols, S.; Yu, D.; Mole, R. A.; Zanotti, J.-M.

2016-04-01

Water confined within carbon nanotubes (CNT) exhibits tremendous enhanced transport properties. Here, we extend this result to ionic liquids (IL) confined in vertically aligned CNT membranes. Under confinement, the IL self-diffusion coefficient is increased by a factor 3 compared to its bulk reference. This could lead to high power battery separators.Water confined within carbon nanotubes (CNT) exhibits tremendous enhanced transport properties. Here, we extend this result to ionic liquids (IL) confined in vertically aligned CNT membranes. Under confinement, the IL self-diffusion coefficient is increased by a factor 3 compared to its bulk reference. This could lead to high power battery separators. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01445c

Dynamically slow processes in supercooled water confined between hydrophobic plates

Energy Technology Data Exchange (ETDEWEB)

Franzese, Giancarlo [Departamento de Fisica Fundamental, Universidad de Barcelona, Diagonal 647, Barcelona 08028 (Spain); Santos, Francisco de los, E-mail: gfranzese@ub.ed, E-mail: fdlsant@ugr.e [Departamento de Electromagnetismo y Fisica de la Materia, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain)

2009-12-16

We study the dynamics of water confined between hydrophobic flat surfaces at low temperature. At different pressures, we observe different behaviors that we understand in terms of the hydrogen bond dynamics. At high pressure, the formation of the open structure of the hydrogen bond network is inhibited and the surfaces can be rapidly dried (dewetted) by formation of a large cavity with decreasing temperature. At lower pressure we observe strong non-exponential behavior of the correlation function, but with no strong increase of the correlation time. This behavior can be associated, on the one hand, to the rapid ordering of the hydrogen bonds that generates heterogeneities and, on the other hand, to the lack of a single timescale as a consequence of the cooperativity in the vicinity of the liquid-liquid critical point that characterizes the phase diagram at low temperature of the water model considered here. At very low pressures, the gradual formation of the hydrogen bond network is responsible for the large increase of the correlation time and, eventually, the dynamical arrest of the system, with a strikingly different dewetting process, characterized by the formation of many small cavities.

Dynamically slow processes in supercooled water confined between hydrophobic plates

International Nuclear Information System (INIS)

Franzese, Giancarlo; Santos, Francisco de los

2009-01-01

We study the dynamics of water confined between hydrophobic flat surfaces at low temperature. At different pressures, we observe different behaviors that we understand in terms of the hydrogen bond dynamics. At high pressure, the formation of the open structure of the hydrogen bond network is inhibited and the surfaces can be rapidly dried (dewetted) by formation of a large cavity with decreasing temperature. At lower pressure we observe strong non-exponential behavior of the correlation function, but with no strong increase of the correlation time. This behavior can be associated, on the one hand, to the rapid ordering of the hydrogen bonds that generates heterogeneities and, on the other hand, to the lack of a single timescale as a consequence of the cooperativity in the vicinity of the liquid-liquid critical point that characterizes the phase diagram at low temperature of the water model considered here. At very low pressures, the gradual formation of the hydrogen bond network is responsible for the large increase of the correlation time and, eventually, the dynamical arrest of the system, with a strikingly different dewetting process, characterized by the formation of many small cavities.

Water confinement effects in response of fuel assembly to faulted condition loads

International Nuclear Information System (INIS)

Shah, S.J.; Brenneman, B.; Williams, G.T.; Strumpel, J.H.

2004-01-01

It has been established by other authors that the accelerations of the water confined by the reactor core baffle plates has a significant effect on the responses of all the fuel assemblies during LOCA (loss of coolant accident) or seismic transients. This particular effect is a consequence of the water being essentially incompressible, and thus experiencing the same horizontal accelerations as the imposed baffle plate motions. These horizontal accelerations of the fluid induce lateral pressure gradients that cause horizontal buoyancy forces on any submerged structures. These forces are in the same direction as the baffle accelerations and, for certain frequencies at least, tend to reduce the relative displacements between the fuel and baffle plates. But there is another confinement effect: the imposed baffle plate velocities must also be transmitted to the water. If the fuel assembly grid strips are treated as simple hydro-foils, these horizontal velocity components change the fluid angle of attack on each strip, and thus may induce large horizontal lift forces on each grid in the same direction as the baffle plate velocity. There is a similar horizontal lift due to inclined flow over the rods when axial flow is present. These combined forces appear to reduce the relative displacements between the fuel and baffle plates for any significant axial flow velocity. Modeling this effect is very simple. It was shown in previous papers that the mechanism for the large fuel assembly damping due to axial flow may be the hydrodynamic forces on the grid strips, and that this is very well represented by discrete viscous dampers at each grid elevation. To include the imposed horizontal water velocity effects, on both the grids and rods, these dampers are simply attached to the baffle plate rather than 'ground'. The large flow-induced damping really acts in a relative reference frame rather than an inertial reference frame, and thus it becomes a flow-induced coupling between the

Molecular dynamics simulations of ultrathin water film confined between flat diamond plates

Directory of Open Access Journals (Sweden)

A.V. Khomenko

2008-12-01

Full Text Available Molecular dynamics simulations of ultrathin water film confined between atomically flat rigid diamond plates are described. Films with thickness of one and two molecular diameters are concerned and TIP4P model is used for water molecules. Dynamical and equilibrium characteristics of the system for different values of the external load and shear force are investigated. An increase of the external load causes the transition of the film to a solidlike state. This is manifested in a decrease of the diffusion constant and in the ordering of the liquid molecules into quasidiscrete layers. For two-layer film under high loads, the molecules also become ordered parallel to the surfaces. Time dependencies of the friction force and the changes of its average value with the load are obtained. In general, the behaviour of the studied model is consistent with the experimental results obtained for simple liquids with spherical molecules.

Dynamic light scattering of nano-gels of xanthan gum biopolymer in colloidal dispersion

Directory of Open Access Journals (Sweden)

Abbas Rahdar

2016-09-01

Full Text Available The dynamical properties of nanogels of xanthan gum (XG with hydrodynamic radius controlled in a size range from 5 nm to 35 nm, were studied at the different XG concentrations in water/sodium bis-2-ethylhexyl-sulfosuccinate (AOT/decane reverse micelles (RMs vs. mass fraction of nano-droplet (MFD at W = 40, using dynamic light scattering (DLS. The diffusion study of nanometer-sized droplets by DLS technique indicated that enhancing concentration of the XG polysaccharide resulted in exchanging the attractive interaction between nano-gels to repulsive interaction, as the mass fraction of nano-droplets increased. The reorientation time (τr of water nanodroplets decreased with MFD for water-in-oil AOT micro-emulsion comprising high concentration (0.0000625 of XG. On the other hand, decreasing concentration of biopolymer led to increasing the rotational correlation time of water nanodroplets with MFD. In conclusion, a single relaxation curve was observed for AOT inverse microemulsions containing different XG concentrations. Furthermore, the interaction between nanogels was changed from attractive to repulsive versus concentration of XG in the AOT RMs.

Poly(styrene-co-butadiene) random copolymer thin films and nanostructures on a mica surface: morphology and contact angles of nanodroplets.

Science.gov (United States)

McClements, Jake; Buffone, Cosimo; Shaver, Michael P; Sefiane, Khellil; Koutsos, Vasileios

2017-09-20

The self-assembly of poly(styrene-co-butadiene) random copolymers on mica surfaces was studied by varying solution concentrations and polymer molecular weights. Toluene solutions of the poly(styrene-co-butadiene) samples were spin coated onto a mica surface and the resulting polymer morphology was investigated by atomic force microscopy. At higher concentrations, thin films formed with varying thicknesses; some dewetting was observed which depended on the molecular weight. Total dewetting did not occur despite the polymer's low glass transition temperature. Instead, partial dewetting was observed suggesting that the polymer was in a metastable equilibrium state. At lower concentrations, spherical cap shaped nanodroplets formed with varying sizes from single polymer chains to aggregates containing millions of chains. As the molecular weight was increased, fewer aggregates were observed on the surface, albeit with larger sizes resulting from increased solution viscosities and more chain entanglements at higher molecular weights. The contact angles of the nanodroplets were shown to be size dependent. A minimum contact angle occurs for droplets with radii of 100-250 nm at each molecular weight. Droplets smaller than 100 nm showed a sharp increase in contact angle; attributed to an increase in the elastic modulus of the droplets, in addition, to a positive line tension value. Droplets larger than 250 nm also showed an increased contact angle due to surface heterogeneities which cannot be avoided for larger droplets. This increase in contact angle plateaus as the droplet size reaches the macroscopic scale.

Hydrogeologic characteristics and water quality of a confined sand unit in the surficial aquifer system, Hunter Army Airfield, Chatham County, Georgia

Science.gov (United States)

Gonthier, Gerard

2012-01-01

An 80-foot-deep well (36Q397, U.S. Geological Survey site identification 320146081073701) was constructed at Hunter Army Airfield to assess the potential of using the surficial aquifer system as a water source to irrigate a ballfield complex. A 300-foot-deep test hole was drilled beneath the ballfield complex to characterize the lithology and water-bearing characteristics of sediments above the Upper Floridan aquifer. The test hole was then completed as well 36Q397 open to a 19-foot-thick shallow, confined sand unit contained within the surficial aquifer system. A single-well, 24-hour aquifer test was performed by pumping well 36Q397 at a rate of 50 gallons per minute during July 13-14, 2011, to characterize the hydrologic properties of the shallow, confined sand unit. Two pumping events prior to the aquifer test affected water levels. Drawdown during all three pumping events and residual drawdown during recovery periods were simulated using the Theis formula on multiple changes in discharge rate. Simulated drawdown and residual drawdown match well with measured drawdown and residual drawdown using values of horizontal hydraulic conductivity and specific storage, which are typical for a confined sand aquifer. Based on the hydrologic parameters used to match simulated drawdown and residual drawdown to measured drawdown and residual drawdown, the transmissivity of the sand was determined to be about 400 feet squared per day. The horizontal hydraulic conductivity of the sand was determined to be about 20 feet per day. Analysis of a water-quality sample indicated that the water is suitable for irrigation. Sample analysis indicated a calcium-carbonate type water having a total dissolved solids concentration of 39 milligrams per liter. Specific conductance and concentrations of all analyzed constituents were below those that would be a concern for irrigation, and were below primary and secondary water-quality criteria levels.

Effect of micellar collisions and polyvinylpyrrolidone confinement on the electrical conductivity percolation parameters of water/AOT/isooctane reverse micelles

Science.gov (United States)

Guettari, Moez; Aferni, Ahmed E. L.; Tajouri, Tahar

2017-12-01

The main aim of this paper is the analysis of micellar collisions and polymer confinement effects on the electrical conductivity percolative behavior of water/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelles. Firstly, we have performed conductance measurements of the system for three AOT to isooctane volume ratio, φm = 0.1 , 0.15 and 0.2 to examine the influence of micellar collisions on the percolation parameters. All the measurements were carried out over the 298.15 K-333.15 K temperature range at a fixed water to AOT molar ratio, W0 = 45 . We have assessed that the rise of micellar collisions frequency enhances the conductance percolation. Secondly, the confinement effect of a water-soluble polymer, polyvinylpyrrolidone (PVP), on the reverse micelles conductance behavior was investigated. Temperature-induced percolation, Tp , have shown a dependence on the polymer concentration, CPVP . It was also observed that for various PVP concentrations, the activation energy of percolation decreases. Finally, the values of the critical exponents determined in the presence and absence of PVP prove that the polymer affects the dynamic of percolation.

Accounting for pore water pressure and confined aquifers in assessing the stability of slopes: a Limit Equilibrium analysis carried out through the Minimum Lithostatic Deviation method

Science.gov (United States)

Ausilia Paparo, Maria; Tinti, Stefano

2015-04-01

The model we introduce is an implementation of the Minimum Lithostatic Deviation (MLD) method, developed by Tinti and Manucci (Tinti and Manucci 2006; 2008), that makes use of the limit equilibrium (LE) theory to estimate the stability of a slope. The main purpose here is to analyse the role of a confined aquifer on the value of the Safety Factor (F), the parameter that in the LE is used to determine if a slope is stable or unstable. The classical LE methods treat unconfined aquifers by including the water pore pressure in the Mohr-Coulomb failure formula: since the water decreases the friction shear strength, the soil above the sliding surface turns out to be more prone to instability. In case of a confined aquifer, however, due to a presence of impermeable layers, the water is not free to flow into the matrix of the overlying soil. We consider here the assumption of a permeable soil sliding over an impermeable layer, which is an occurrence that is found in several known landslide cases (e.g. Person, 2008; Strout and Tjeltja, 2008; Morgan et al., 2010 for offshore slides; and Palladino and Peck, 1972; Miller and Sias, 1998; Jiao et al. 2005; Paparo et al., 2013 for slopes in proximity of artificial or natural water basins) where clay beds form the potential sliding surface: the water, confined below, pushes along these layers and acts on the sliding body as an external bottom load. We modify the MLD method equations in order to take into account the load due to a confined aquifer and apply the new model to the Vajont case, where many have hypothesised the contribution of a confined aquifer to the failure. Our calculations show that the rain load i) infiltrating directly into the soil body and ii) penetrating into the confined aquifer below the clay layers, in addition with the lowering of the reservoir level, were key factors of destabilization of the Mt Toc flank and caused the disastrous landslide.

Studies of the viscoelastic properties of water confined between surfaces of specified chemical nature.

Energy Technology Data Exchange (ETDEWEB)

Houston, Jack E.; Grest, Gary Stephen; Moore, Nathan W.; Feibelman, Peter J.

2010-09-01

This report summarizes the work completed under the Laboratory Directed Research and Development (LDRD) project 10-0973 of the same title. Understanding the molecular origin of the no-slip boundary condition remains vitally important for understanding molecular transport in biological, environmental and energy-related processes, with broad technological implications. Moreover, the viscoelastic properties of fluids in nanoconfinement or near surfaces are not well-understood. We have critically reviewed progress in this area, evaluated key experimental and theoretical methods, and made unique and important discoveries addressing these and related scientific questions. Thematically, the discoveries include insight into the orientation of water molecules on metal surfaces, the premelting of ice, the nucleation of water and alcohol vapors between surface asperities and the lubricity of these molecules when confined inside nanopores, the influence of water nucleation on adhesion to salts and silicates, and the growth and superplasticity of NaCl nanowires.

Fast-switching optically isotropic liquid crystal nano-droplets with improved depolarization and Kerr effect by doping high k nanoparticles.

Science.gov (United States)

Kim, Byeonggon; Kim, Hyun Gyu; Shim, Gyu-Yeop; Park, Ji-Sub; Joo, Kyung-Il; Lee, Dong-Jin; Lee, Joun-Ho; Baek, Ji-Ho; Kim, Byeong Koo; Choi, Yoonseuk; Kim, Hak-Rin

2018-01-10

We proposed and analyzed an optically isotropic nano-droplet liquid crystal (LC) doped with high k nanoparticles (NPs), exhibiting enhanced Kerr effects, which could be operated with reduced driving voltages. For enhancing the contrast ratio together with the light efficiencies, the LC droplet sizes were adjusted to be shorter than the wavelength of visible light to reduce depolarization effects by optical scattering of the LC droplets. Based on the optical analysis of the depolarization effects, the influence of the relationship between the LC droplet size and the NP doping ratio on the Kerr effect change was investigated.

Formation times of RbHe exciplexes on the surface of superfluid versus normal fluid helium nanodroplets

International Nuclear Information System (INIS)

Droppelmann, G.; Buenermann, O.; Stienkemeier, F.; Schulz, C.P.

2004-01-01

Nanodroplets of either superfluid He 4 or normal fluid He 3 are doped with Rb atoms that are bound to the surface of the droplets. The formation of RbHe exciplexes upon 5P 3/2 excitation is monitored in real time by femtosecond pump-probe techniques. We find formation times of 8.5 and 11.6 ps for Rb He 4 and Rb He 3 , respectively. A comparison to calculations based on a tunneling model introduced for these systems by Reho et al. [J. Chem. Phys. 113, 9694 (2000)] shows that the proposed mechanism cannot account for our findings. Apparently, a different relaxation dynamics of the superfluid opposed to the normal fluid surface is responsible for the observed formation times

Final Technical Report: Vibrational Spectroscopy of Transient Combustion Intermediates Trapped in Helium Nanodroplets

Energy Technology Data Exchange (ETDEWEB)

Douberly, Gary Elliott [Univ. of Georgia, Athens, GA (United States)

2017-11-16

The objective of our experimental research program is to isolate and stabilize transient intermediates and products of prototype combustion reactions. This will be accomplished by Helium Nanodroplet Isolation, a novel technique where liquid helium droplets freeze out high energy metastable configurations of a reacting system, permitting infrared spectroscopic characterizations of products and intermediates that result from hydrocarbon radical reactions with molecular oxygen and other small molecules relevant to combustion environments. The low temperature (0.4 K) and rapid cooling associated with He droplets provides a perfectly suited medium to isolate and probe a broad range of molecular radical and carbene systems important to combustion chemistry. The sequential addition of molecular species to He droplets often leads to the stabilization of high-energy, metastable cluster configurations that represent regions of the potential energy surface far from the global minimum. Single and double resonance IR laser spectroscopy techniques, along with Stark and Zeeman capabilities, are being used to probe the structural and dynamical properties of these systems.

Stimulated phase-shift acoustic nanodroplets enhance vancomycin efficacy against methicillin-resistant Staphylococcus aureus biofilms

Directory of Open Access Journals (Sweden)

Guo H

2017-06-01

Full Text Available Hao Guo,1 Ziming Wang,1 Quanyin Du,1 Pan Li,2 Zhigang Wang,2 Aimin Wang1 1Department of Orthopedics, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing, China; 2Chongqing Key Laboratory of Ultrasound Molecular Imaging, Institute of Ultrasound Imaging, Second Affiliated Hospital of Chongqing Medical University, Chongqing, China Purpose: Bacterial biofilms on the surface of prostheses are becoming a rising concern in managing prosthetic joint infections. The inherent resistant features of biofilms render traditional antimicrobial therapy unproductive and revision surgery outcomes uncertain. This situation has prompted the exploration of novel antimicrobial strategies. The synergy of ultrasound microbubbles and vancomycin has been proposed as an efficient alternative for biofilm eradication. The purpose of this study was to evaluate the anti-biofilm effect of stimulated phase-shift acoustic nanodroplets (NDs combined with vancomycin.Materials and methods: We fabricated lipid phase-shift NDs with a core of liquid perfluoropentane. A new phase change mode for NDs incorporating an initial unfocused low-intensity pulsed ultrasound for 5 minutes and a subsequent incubation at 37°C into a 24-hour duration was developed. Methicillin-resistant Staphylococcus aureus (MRSA biofilms were incubated with vancomycin and NDs under the hybrid stimulation. Biofilm morphology following treatment was determined using confocal laser scanning microscopy and scanning electron microscopy. Resazurin assay was used to quantify bactericidal efficacy against MRSA biofilm bacteria.Results: NDs treated sequentially with ultrasound and heating at 37°C achieved gradual and substantial ND vaporization and cavitation in a successive process. NDs after stimulation were capable of generating stronger destruction on biofilm structure which was best characterized by residual circular arc margins and more dead bacteria. Furthermore, NDs

Cracks and nanodroplets produced on tungsten surface samples by dense plasma jets

Science.gov (United States)

Ticoş, C. M.; Galaţanu, M.; Galaţanu, A.; Luculescu, C.; Scurtu, A.; Udrea, N.; Ticoş, D.; Dumitru, M.

2018-03-01

Small samples of 12.5 mm in diameter made from pure tungsten were exposed to a dense plasma jet produced by a coaxial plasma gun operated at 2 kJ. The surface of the samples was analyzed using a scanning electron microscope (SEM) before and after applying consecutive plasma shots. Cracks and craters were produced in the surface due to surface tensions during plasma heating. Nanodroplets and micron size droplets could be observed on the samples surface. An energy-dispersive spectroscopy (EDS) analysis revealed that the composition of these droplets coincided with that of the gun electrode material. Four types of samples were prepared by spark plasma sintering from powders with the average particle size ranging from 70 nanometers up to 80 μm. The plasma power load to the sample surface was estimated to be ≈4.7 MJ m-2 s-1/2 per shot. The electron temperature and density in the plasma jet had peak values 17 eV and 1.6 × 1022 m-3, respectively.

Nano-confined water in the interlayers of hydrocalumite: Reorientational dynamics probed by neutron spectroscopy and molecular dynamics computer simulations

Science.gov (United States)

Kalinichev, A. G.; Faraone, A.; Udovic, T.; Kolesnikov, A. I.; de Souza, N. R.; Reinholdt, M. X.; Kirkpatrick, R.

2008-12-01

Layered double hydroxides (LDHs, anionic clays) represent excellent model systems for detailed molecular- level studies of the structure, dynamics, and energetics of nano-confined water in mineral interlayers and nano-pores, because LDH interlayers can have a well-defined structures and contain H2O molecules and a wide variety of anions in structurally well-defined positions and coordinations. [Ca2Al(OH)6]Cl·2H2O, also known as hydrocalumite or Friedel's salt, has a well- ordered Ca,Al distribution in the hydroxide layer and a very high degree of H2O,Cl ordering in the interlayer. It is also one of the only LDH phase for which a single crystal structure refinement is available. Thus, it is currently the best model compound for understanding the structure and dynamical behavior of interlayer and surface species in other, less-ordered, LDHs. We investigated the structural and dynamic behavior of water in the interlayers of hydrocalumite using inelastic (INS) and quasielastic (QENS) neutron scattering and molecular dynamics computer simulations. The comperehensive neutron scattering studies were performed for one fully hydrated and one dehydrated sample of hydrocalumite using several complementary instruments (HFBS, DCS and FANS at NCNR; HRMECS and QENS at IPNS) at temperatures above and below the previously discovered order-disorder interlayer phase transition. Together the experimental and molecular modeling results capture the important details of the dynamics of nano-confined water and the effects of the orientational ordering of H2O molecules above and below the phase transition. They provide otherwise unobtainable experimental information about the transformation of H2O librational and diffusional modes across the order-disorder phase transition and significantly add to our current understanding of the structure and dynamics of water in LDH phases based on the earlier NMR, IR, X-ray, and calorimetric measurements. The approach can now be extended to probe the

A Cascade Disaster Caused by Geological and Coupled Hydro-Mechanical Factors—Water Inrush Mechanism from Karst Collapse Column under Confining Pressure

Directory of Open Access Journals (Sweden)

Hao Li

2017-11-01

Full Text Available The water inrush from karst collapse column (KCC is a cascading, vicious cycle disaster caused by geological and mining activities, that can cause serious casualties and property losses. The key to preventing this risk is to study the mechanism of water inrush under confining pressure. Aiming at the investigationg the characteristics of the KCC named X1 in Chensilou mine, a series of methods, including connectivity experiments, water pressure monitoring tests in two side-walls, and numerical simulations based on plastic damage-seepage (PD-S theory have been developed. The methods are used to test the security of the 2519 mining area, the damage thickness, pore water pressure, and seepage vector in the X1. The results indicate that the X1 has a certain water blocking capacity. In addition, with the decrease of confining pressure and increase of shear stress, deviatoric stress could cause the increase of permeability, the reduction of strength, and the reduction of pore water pressure in KCC. Therefore the increased effective stress in the rock will force the rock to become more fractured. Conversely, the broken rock could cause the change of stress, and further initiate new plastic strains, damage and pore water pressure until a new equilibrium is reached. This cascading water inrush mechanism will contribute to the exploitation of deep coal resources in complex geological and hydrogeological conditions.

Pathways to dewetting in hydrophobic confinement.

Science.gov (United States)

Remsing, Richard C; Xi, Erte; Vembanur, Srivathsan; Sharma, Sumit; Debenedetti, Pablo G; Garde, Shekhar; Patel, Amish J

2015-07-07

Liquid water can become metastable with respect to its vapor in hydrophobic confinement. The resulting dewetting transitions are often impeded by large kinetic barriers. According to macroscopic theory, such barriers arise from the free energy required to nucleate a critical vapor tube that spans the region between two hydrophobic surfaces--tubes with smaller radii collapse, whereas larger ones grow to dry the entire confined region. Using extensive molecular simulations of water between two nanoscopic hydrophobic surfaces, in conjunction with advanced sampling techniques, here we show that for intersurface separations that thermodynamically favor dewetting, the barrier to dewetting does not correspond to the formation of a (classical) critical vapor tube. Instead, it corresponds to an abrupt transition from an isolated cavity adjacent to one of the confining surfaces to a gap-spanning vapor tube that is already larger than the critical vapor tube anticipated by macroscopic theory. Correspondingly, the barrier to dewetting is also smaller than the classical expectation. We show that the peculiar nature of water density fluctuations adjacent to extended hydrophobic surfaces--namely, the enhanced likelihood of observing low-density fluctuations relative to Gaussian statistics--facilitates this nonclassical behavior. By stabilizing isolated cavities relative to vapor tubes, enhanced water density fluctuations thus stabilize novel pathways, which circumvent the classical barriers and offer diminished resistance to dewetting. Our results thus suggest a key role for fluctuations in speeding up the kinetics of numerous phenomena ranging from Cassie-Wenzel transitions on superhydrophobic surfaces, to hydrophobically driven biomolecular folding and assembly.

Electrospinning of poly(vinyl alcohol) nanofibers loaded with hexadecane nanodroplets.

Science.gov (United States)

Arecchi, A; Mannino, S; Weiss, J

2010-08-01

The feasibility of producing poly(vinyl alcohol) (PVA) nanofibers containing fine-disperse hexadecane droplets by electrospinning a blend of hexadecane-in-water emulsions and PVA was investigated. Hexadecane oil-in-water nanoemulsions (d(10)= 181.2 +/- 0.1 nm) were mixed with PVA at pH 4.5 to yield polymer-emulsion blends containing 0.5 to 1.5 wt% oil droplets and 8-wt% PVA. The solution properties of emulsions and emulsion-PVA blends (viscosity, conductivity, surface tension) were determined. Solutions were electrospun and the morphology and thermal properties of deposited fiber mats characterized by scanning electron microscopy and differential scanning calorimetry. Fiber mats were dissolved in buffer to liberate incorporated hexadecane droplets and the buffer solutions analyzed by optical microscopy, UV-spectroscopy, and light scattering. Analysis of dry fiber mats and their solutions showed that emulsion droplets were indeed part of the electrospun fiber structures. Depending on the concentration of hexadecane in the initial emulsion-polymer blends, droplets were dispersed in the fibers as individual droplets or in form of aggregated flocs of hexadecane droplets. Nanofibers with spindle-like perturbations or nanofibers containing bead-like structures with approximately 5 times larger than the size of droplets in the original nanoemulsion were obtained. Remarkably, incorporation of hexadecane droplets in fibers did not alter size of individual droplets, that is, no coalescence occurred. The manufacture of solid matrix containing nanodroplets could be of substantial interest for manufacturers wishing to develop encapsulation system for lipophilic functional compounds such as lipid-soluble flavors, antimicrobials, antioxidants, and bioactives with tailored release kinetics. Practical Applications: The paper describes the formation of electrospun nanofibers from hydrophilic polymers that contain fine-disperse emulsion droplets. By incorporating emulsion droplets, a

Nuclear Quantum Effects in H(+) and OH(-) Diffusion along Confined Water Wires.

Science.gov (United States)

Rossi, Mariana; Ceriotti, Michele; Manolopoulos, David E

2016-08-04

The diffusion of protons and hydroxide ions along water wires provides an efficient mechanism for charge transport that is exploited by biological membrane channels and shows promise for technological applications such as fuel cells. However, what is lacking for a better control and design of these systems is a thorough theoretical understanding of the diffusion process at the atomic scale. Here we focus on two aspects of this process that are often disregarded because of their high computational cost: the use of first-principles potential energy surfaces and the treatment of the nuclei as quantum particles. We consider proton and hydroxide ions in finite water wires using density functional theory augmented with an apolar cylindrical confining potential. We employ machine learning techniques to identify the charged species, thus obtaining an agnostic definition that takes explicitly into account the delocalization of the charge in the Grotthus-like mechanism. We include nuclear quantum effects (NQEs) through the thermostated ring polymer molecular dynamics method and model finite system size effects by considering Langevin dynamics on the potential of mean force of the charged species, allowing us to extract the same "universal" diffusion coefficient from simulations with different wire sizes. In the classical case, diffusion coefficients depend significantly on the potential energy surface, in particular on how dispersion forces modulate water-water distances. NQEs, however, make the diffusion less sensitive to the underlying potential and geometry of the wire.

Lithium atoms on helium nanodroplets: Rydberg series and ionization dynamics

Science.gov (United States)

Lackner, Florian; Krois, Günter; Ernst, Wolfgang E.

2017-11-01

The electronic excitation spectrum of lithium atoms residing on the surface of helium nanodroplets is presented and analyzed employing a Rydberg-Ritz approach. Utilizing resonant two-photon ionization spectroscopy, two different Rydberg series have been identified: one assigned to the nS(Σ) series and the other with predominantly nP(Π) character. For high Rydberg states, which have been resolved up to n = 13, the surrounding helium effectively screens the valence electron from the Li ion core, as indicated by the apparent red-shift of Li transitions and lowered quantum defects on the droplet with respect to their free atom counterparts. For low n states, the screening effect is weakened and the prevailing repulsive interaction gives rise to strongly broadened and blue-shifted transitions. The red-shifts originate from the polarization of nearby He atoms by the positive Li ion core. As a consequence of this effect, the ionization threshold is lowered by 116 ± 10 cm-1 for Li on helium droplets with a radius of about 40 Å. Upon single-photon ionization, heavy complexes corresponding to Li ions attached to intact helium droplets are detected. We conclude that ionization close to the on-droplet ionization threshold triggers a dynamic process in which the Li ion core undergoes a transition from a surface site into the droplet.

Photoacoustics of single laser-trapped nanodroplets for the direct observation of nanofocusing in aerosol photokinetics

Science.gov (United States)

Cremer, Johannes W.; Thaler, Klemens M.; Haisch, Christoph; Signorell, Ruth

2016-03-01

Photochemistry taking place in atmospheric aerosol droplets has a significant impact on the Earth's climate. Nanofocusing of electromagnetic radiation inside aerosols plays a crucial role in their absorption behaviour, since the radiation flux inside the droplet strongly affects the activation rate of photochemically active species. However, size-dependent nanofocusing effects in the photokinetics of small aerosols have escaped direct observation due to the inability to measure absorption signatures from single droplets. Here we show that photoacoustic measurements on optically trapped single nanodroplets provide a direct, broadly applicable method to measure absorption with attolitre sensitivity. We demonstrate for a model aerosol that the photolysis is accelerated by an order of magnitude in the sub-micron to micron size range, compared with larger droplets. The versatility of our technique promises broad applicability to absorption studies of aerosol particles, such as atmospheric aerosols where quantitative photokinetic data are critical for climate predictions.

Wave excited motion of a body floating on water confined between two semi-infinite ice sheets

Science.gov (United States)

Ren, K.; Wu, G. X.; Thomas, G. A.

2016-12-01

The wave excited motion of a body floating on water confined between two semi-infinite ice sheets is investigated. The ice sheet is treated as an elastic thin plate and water is treated as an ideal and incompressible fluid. The linearized velocity potential theory is adopted in the frequency domain and problems are solved by the method of matched eigenfunctions expansion. The fluid domain is divided into sub-regions and in each sub-region the velocity potential is expanded into a series of eigenfunctions satisfying the governing equation and the boundary conditions on horizontal planes including the free surface and ice sheets. Matching is conducted at the interfaces of two neighbouring regions to ensure the continuity of the pressure and velocity, and the unknown coefficients in the expressions are obtained as a result. The behaviour of the added mass and damping coefficients of the floating body with the effect of the ice sheets and the excitation force are analysed. They are found to vary oscillatorily with the wave number, which is different from that for a floating body in the open sea. The motion of the body confined between ice sheets is investigated, in particular its resonant behaviour with extremely large motion found to be possible under certain conditions. Standing waves within the polynya are also observed.

DEVELOPMENT OF A METHODOLOGY FOR REGIONAL EVALUATION OF CONFINING BED INTEGRITY

Science.gov (United States)

For safe underground injection of liquid waste, confining formations must be thick, extensive, and have low permeability. Recognition of faults that extend from the potential injection zone to underground sources of drinking water is critical for evaluation of confining-bed integ...

Reinforced confinement in a nuclear reactor

International Nuclear Information System (INIS)

Norman, H.

1988-01-01

The present invention concerns a nuclear reactor containing a reactor core, a swimming pool space that is filled and pressurized with a neutron-absorbing solution, a reactor tank, at least one heat exchanger, at least one inlet line, at least one return line and at least one circulation pump, where the said reactor tank is confined in the said swimming pool space and designed to be cooled with the aid of relatively pure water, which is fed by means of the said at least one circulating pump to the said reactor tank from the said heat exchanger via the said at least one inlet line and is returned to the heat exchanger via the said at least one return line. The problem that is to be solved by the invention is to design a reactor of the above type in such a way that a complete confinement of the primary circuit of the reactor is achieved at relatively low extra cost. This problem is solved by providing the reactor with a special confinement space that confines the heat exchanger, but not the reactor tank, with the confinement space and the swimming pool space being fashioned in the same concrete body

Evaluation of Confining Layer Integrity Beneath the South District Wastewater Treatment Plant, Miami-Dade Water and Sewer Department, Dade County, Florida

Energy Technology Data Exchange (ETDEWEB)

Starr, Robert Charles; Green, Timothy Scott; Hull, Laurence Charles

2001-02-01

A review has been performed of existing information that describes geology, hydrogeology, and geochemistry at the South District Wastewater Treatment Plant, which is operated by the Miami-Dade Water and Sewer Department, in Dade County, Florida. Treated sanitary wastewater is injected into a saline aquifer beneath the plant. Detection of contaminants commonly associated with treated sanitary wastewater in the freshwater aquifer that overlies the saline aquifer has indicated a need for a reevaluation of the ability of the confining layer above the saline aquifer to prevent fluid migration into the overlying freshwater aquifer. Review of the available data shows that the geologic data set is not sufficient to demonstrate that a competent confining layer is present between the saline and freshwater aquifers. The hydrogeologic data also do not indicate that a competent confining layer is present. The geochemical data show that the freshwater aquifer is contaminated with treated wastewater, and the spatial patterns of contamination are consistent with upward migration through localized conduits through the Middle Confining Unit, such as leaking wells or natural features. Recommendations for collection and interpretation of additional site characterization data are provided.

Nanodroplet processing platform for deep and quantitative proteome profiling of 10–100 mammalian cells

Energy Technology Data Exchange (ETDEWEB)

Zhu, Ying; Piehowski, Paul D.; Zhao, Rui; Chen, Jing; Shen, Yufeng; Moore, Ronald J.; Shukla, Anil K.; Petyuk, Vladislav A.; Campbell-Thompson, Martha; Mathews, Clayton E.; Smith, Richard D.; Qian, Wei-Jun; Kelly, Ryan T.

2018-02-28

Nanoscale or single cell technologies are critical for biomedical applications. However, current mass spectrometry (MS)-based proteomic approaches require samples comprising a minimum of thousands of cells to provide in-depth profiling. Here, we report the development of a nanoPOTS (Nanodroplet Processing in One pot for Trace Samples) platform as a major advance in overall sensitivity. NanoPOTS dramatically enhances the efficiency and recovery of sample processing by downscaling processing volumes to <200 nL to minimize surface losses. When combined with ultrasensitive LC-MS, nanoPOTS allows identification of ~1500 to ~3,000 proteins from ~10 to ~140 cells, respectively. By incorporating the Match Between Runs algorithm of MaxQuant, >3000 proteins were consistently identified from as few as 10 cells. Furthermore, we demonstrate robust quantification of ~2400 proteins from single human pancreatic islet thin sections from type 1 diabetic and control donors, illustrating the application of nanoPOTS for spatially resolved proteome measurements from clinical tissues.

Spectroscopy of Cold LiCa Molecules Formed on Helium Nanodroplets

Science.gov (United States)

2013-01-01

We report on the formation of mixed alkali–alkaline earth molecules (LiCa) on helium nanodroplets and present a comprehensive experimental and theoretical study of the ground and excited states of LiCa. Resonance enhanced multiphoton ionization time-of-flight (REMPI-TOF) spectroscopy and laser induced fluorescence (LIF) spectroscopy were used for the experimental investigation of LiCa from 15000 to 25500 cm–1. The 42Σ+ and 32Π states show a vibrational structure accompanied by distinct phonon wings, which allows us to determine molecular parameters as well as to study the interaction of the molecule with the helium droplet. Higher excited states (42Π, 52Σ+, 52Π, and 62Σ+) are not vibrationally resolved and vibronic transitions start to overlap. The experimental spectrum is well reproduced by high-level ab initio calculations. By using a multireference configuration interaction (MRCI) approach, we calculated the 19 lowest lying potential energy curves (PECs) of the LiCa molecule. On the basis of these calculations, we could identify previously unobserved transitions. Our results demonstrate that the helium droplet isolation approach is a powerful method for the characterization of tailor-made alkali–alkaline earth molecules. In this way, important contributions can be made to the search for optimal pathways toward the creation of ultracold alkali–alkaline earth ground state molecules from the corresponding atomic species. Furthermore, a test for PECs calculated by ab initio methods is provided. PMID:24028555

Study of the confined solutions properties: case of gel formed during nuclear glass alteration

International Nuclear Information System (INIS)

Matar-Briman, I.

2012-01-01

In this study, we have investigated the thermodynamic properties, the structure and the dynamics of confined solutions in model gels and in a gel coming from glass alteration. The first step was to determine the structure and the dynamics of pure confined water in porous materials by using nuclear magnetic resonance and neutron scattering. Meso-porous silica was elaborated and grafted by sol-gel route to decrease the pore sizes from 2.7 to 2 nm and to modify pore surfaces to have Si-OH, Zr-OH and Al-OH. The second step involved determining the dynamics of water in leachate confined in the model gels and in the gel of altered glass by using neutron scattering. In the model gels and at a 10 -12 -10 -9 second timescale, two kinds of waters were highlighted: first, an interfacial water linked to the pore surfaces and second, a free water in the pore core. Their ratio depends on the pore size and pore surface composition. Whatever the pore surface, when the pore size decreases the free water ratio in the pore center also decreases. For pores smaller than 2.3 nm and pore surfaces with Zr-OH or Al-OH surfaces, water is strongly linked to the surface and few water molecules are mobile. This is due to the ability of alumina and zirconia to immobilize water molecules through chemical coordination bonds stronger than the physical bonds established between silica and water. The result also highlight that pore surface composition could be the predominant parameter affecting the fixed proton content. Moreover, the mobility of water confined in a leachate is not modified. The study of the water dynamics in a gel formed during alteration of glass constituted of SiO 2 , Al 2 O 3 and CaO, and having a porosity between 2 and 7 nm showed the same behavior as water confined in pores presenting an Al-OH surface. (author) [fr

SAR interferometry monitoring of subsidence in a detritic basin related to water depletion in the underlying confined carbonate aquifer (Torremolinos, southern Spain).

Science.gov (United States)

Ruiz-Constán, A; Ruiz-Armenteros, A M; Martos-Rosillo, S; Galindo-Zaldívar, J; Lazecky, M; García, M; Sousa, J J; Sanz de Galdeano, C; Delgado-Blasco, J M; Jiménez-Gavilán, P; Caro-Cuenca, M; Luque-Espinar, J A

2018-04-30

This research underlines the need to improve water management policies for areas linked to confined karstic aquifers subjected to intensive exploitation, and to develop additional efforts towards monitoring their subsidence evolution. We analyze subsidence related to intensive use of groundwater in a confined karstic aquifer, through the use of the InSAR technique, by the southern coast of Spain (Costa del Sol). Carbonates are overlain by an unconfined detritic aquifer with interlayered high transmissivity rocks, in connection with the Mediterranean Sea, where the water level is rather stable. Despite this, an accumulated deformation in the line-of-sight (LOS) direction greater than -100 mm was observed by means of the ERS-1/2 (1992-2000) and Envisat (2003-2009) satellite SAR sensors. During this period, the Costa del Sol experienced a major population increase due to the expansion of the tourism industry, with the consequent increase in groundwater exploitation. The maximum LOS displacement rates recorded during both time spans are respectively -6 mm/yr and -11 mm/yr, respectively. During the entire period, there was an accumulated descent of the confined water level of 140 m, and several fluctuations of more than 80 m correlating with the subsidence trend observed for the whole area. Main sedimentary depocenters (up to 800 m), revealed by gravity prospecting, partly coincide with areas of subsidence maxima; yet ground deformation is also influenced by other factors, the main ones being the fine-grained facies distribution and rapid urbanization due to high touristic pressure. Copyright © 2018 Elsevier B.V. All rights reserved.

Phase separation of acetonitrile-water mixtures and minimizing of ice crystallites from there in confinement of MCM-41.

Science.gov (United States)

Kittaka, Shigeharu; Kuranishi, Miki; Ishimaru, Shinji; Umahara, Osamu

2007-03-07

The effect of confinement of an acetonitrile-water mixture, whose correlation length was comparable to the pore size of the mesopores of MCM-41 (d=2.4-3.6 nm), on the phase changes was studied. Used techniques were low temperature differential scanning calorimetry and Fourier transform infrared spectroscopy, where the phase separation, lowering of the freezing and melting temperatures, and phase transitions of the acetonitrile were detected. The latter occurred in the mesopores at temperatures similar to that of the pure liquid, while the melting temperature of the water in the mesopores<3.1 nm decreased markedly at higher acetonitrile contents, suggesting a marked lowering of ice crystallite size.

Investigation of the mid-infrared emission of a floating water bridge

International Nuclear Information System (INIS)

Fuchs, Elmar C; Paulitsch-Fuchs, Astrid H; Agostinho, Luewton L F; Wexler, Adam D; Cherukupally, Anvesh; Woisetschläger, Jakob; Freund, Friedemann T

2012-01-01

We report on the infrared emission of aqueous bridges under the application of high dc voltage (‘floating water bridge’) over the range between 400 and 2500 cm -1 (4.0-10.3 µm). Comparison with bulk water of the same temperature reveals an additional broad peak at ∼2200 cm -1 as well as water vapour emission lines. Two complementary explanations are presented for the broad peak: first, a cooperative proton transfer comprising an orientational motion along the direction of conduction is suggested. Second, the electrolysis-less current flow is explained by a proton/defect-proton band mechanism, which is in line with the cooperative proton transfer. The water vapour emissions occur due to collision ionization of space charges with micro- and nano-droplets which are electrosprayed from the liquid/gas interface.

Investigation of the mid-infrared emission of a floating water bridge

Science.gov (United States)

Fuchs, Elmar C.; Cherukupally, Anvesh; Paulitsch-Fuchs, Astrid H.; Agostinho, Luewton L. F.; Wexler, Adam D.; Woisetschläger, Jakob; Freund, Friedemann T.

2012-11-01

We report on the infrared emission of aqueous bridges under the application of high dc voltage (‘floating water bridge’) over the range between 400 and 2500 cm-1 (4.0-10.3 µm). Comparison with bulk water of the same temperature reveals an additional broad peak at ˜2200 cm-1 as well as water vapour emission lines. Two complementary explanations are presented for the broad peak: first, a cooperative proton transfer comprising an orientational motion along the direction of conduction is suggested. Second, the electrolysis-less current flow is explained by a proton/defect-proton band mechanism, which is in line with the cooperative proton transfer. The water vapour emissions occur due to collision ionization of space charges with micro- and nano-droplets which are electrosprayed from the liquid/gas interface.

Application of Ultrasound to Selectively Localize Nanodroplets for Targeted Imaging and Therapy

Directory of Open Access Journals (Sweden)

Paul A. Dayton

2006-07-01

Full Text Available Lipid-coated perfluorocarbon nanodroplets are submicrometer-diameter liquid-filled droplets with proposed applications in molecularly targeted therapeutics and ultrasound (US imaging. Ultrasonic molecular imaging is unique in that the optimal application of these agents depends not only on the surface chemistry, but also on the applied US field, which can increase receptor-ligand binding and membrane fusion. Theory and experiments are combined to demonstrate the displacement of perfluorocarbon nanoparticles in the direction of US propagation, where a traveling US wave with a peak pressure on the order of megapascals and frequency in the megahertz range produces a particle translational velocity that is proportional to acoustic intensity and increases with increasing center frequency. Within a vessel with a diameter on the order of hundreds of micrometers or larger, particle velocity on the order of hundreds of micrometers per second is produced and the dominant mechanism for droplet displacement is shown to be bulk fluid streaming. A model for radiation force displacement of particles is developed and demonstrates that effective particle displacement should be feasible in the microvasculature. In a flowing system, acoustic manipulation of targeted droplets increases droplet retention. Additionally, we demonstrate the feasibility of US-enhanced particle internalization and therapeutic delivery.

EPR Evidence of Liquid Water in Ice: An Intrinsic Property of Water or a Self-Confinement Effect?

Science.gov (United States)

Thangswamy, Muthulakshmi; Maheshwari, Priya; Dutta, Dhanadeep; Rane, Vinayak; Pujari, Pradeep K

2018-06-01

Liquid water (LW) existence in pure ice below 273 K has been a controversial aspect primarily because of the lack of experimental evidence. Recently, electron paramagnetic resonance (EPR) has been used to study deeply supercooled water in a rapidly frozen polycrystalline ice. The same technique can also be used to probe the presence of LW in polycrystalline ice that has formed through a more conventional, slow cooling one. In this context, the present study aims to emphasize that in case of an external probe involving techniques such as EPR, the results are influenced by the binary phase (BP) diagram of the probe-water system, which also predicts the existence of LW domains in ice, up to the eutectic point. Here we report the results of our such EPR spin-probe studies on water, which demonstrate that smaller the concentration of the probe stronger is the EPR evidence of liquid domains in polycrystalline ice. We used computer simulations based on stochastic Liouville theory to analyze the lineshapes of the EPR spectra. We show that the presence of the spin probe modifies the BP diagram of water, at very low concentrations of the spin probe. The spin probe thus acts, not like a passive reporter of the behavior of the solvent and its environment, but as an active impurity to influence the solvent. We show that there exists a lower critical concentration, below which BP diagram needs to be modified, by incorporating the effect of confinement of the spin probe. With this approach, we demonstrate that the observed EPR evidence of LW domains in ice can be accounted for by the modified BP diagram of the probe-water system. The present work highlights the importance of taking cognizance of the possibility of spin probes affecting the host systems, when interpreting the EPR (or any other probe based spectroscopic) results of phase transitions of host, as its ignorance may lead to serious misinterpretations.

Characterization of geo-polymer porosity: temporal evolution and study of the confined water

International Nuclear Information System (INIS)

Benavent, Virginie

2016-01-01

In this study, we have investigated the porous network of geo-polymers. The first step consisted in characterizing the structure of the porous network by the means of both intrusive experimental techniques (water porosimetry, gas sorption and mercury intrusion) and non-intrusive techniques (small-angle X-ray and neutron scattering). By the same time, the evolutions of the porous structure as well as the mechanical properties were followed over time. The second step was to determine the structure, the thermodynamics and the dynamics of water confined in the porosity by differential scanning calorimetry, quasi-elastic neutron scattering and migration tests. Geo-polymer pore structure is a complex multi-scale porosity, a meso- and macroporous network, essentially open and connected. It consists in a vermicular meso-porous network which connects the macro-pores. The meso-pore characteristic size depends on the formulation of the geo-polymer paste and is ranged between about 4 and 10 nm. Geo-polymer have a total pore volume comprised between 40 and 50 %, the meso-porous volume represents between 7 and 15 % of the material global volume. The majority of the pore volume is then attributed to macro-pores. a slight closure of porosity was observed with time and was attributed to a dissolution-precipitation mechanism occurring at pore wall interfaces. The mechanical properties reach a maximum within 10 days, and then are stable over time when the samples were kept from drying and carbonation and at the temperature of 20 C. Besides, three kinds of water were highlighted inside the porosity: (i) an interfacial water linked at the pore surfaces, (ii) free water inside the meso-pores and (iii) free water inside macro-pores. at local time scale, the mobility of water was found close to the one of free water, and at the macroscopic scale, a decrease in diffusion coefficient of one order of magnitude was observed, together with an effect of meso-pore size. (author) [fr

Fractional governing equations of transient groundwater flow in confined aquifers with multi-fractional dimensions in fractional time

Directory of Open Access Journals (Sweden)

M. L. Kavvas

2017-10-01

Full Text Available Using fractional calculus, a dimensionally consistent governing equation of transient, saturated groundwater flow in fractional time in a multi-fractional confined aquifer is developed. First, a dimensionally consistent continuity equation for transient saturated groundwater flow in fractional time and in a multi-fractional, multidimensional confined aquifer is developed. For the equation of water flux within a multi-fractional multidimensional confined aquifer, a dimensionally consistent equation is also developed. The governing equation of transient saturated groundwater flow in a multi-fractional, multidimensional confined aquifer in fractional time is then obtained by combining the fractional continuity and water flux equations. To illustrate the capability of the proposed governing equation of groundwater flow in a confined aquifer, a numerical application of the fractional governing equation to a confined aquifer groundwater flow problem was also performed.

Study of confinement and sliding friction of fluids using sum frequency generation spectroscopy

Science.gov (United States)

Nanjundiah, Kumar

2007-12-01

Friction and wear are important technologically. Tires on wet roads, windshield wipers and human joints are examples where nanometer-thick liquids are confined between flexible-rigid contact interfaces. Fundamental understanding of the structure of these liquids can assist in the design of products such as artificial joints and lubricants for Micro-electromechanical systems [MEMS]. Prior force measurements have suggested an increase in apparent viscosity of confined liquid and sometimes solid-like responses. But, these have not given the state of molecules under confinement. In the present study, we have used a surface sensitive, non-linear optical technique (infrared-visible sum frequency generation spectroscopy [SFG]) to investigate molecular structure at hidden interfaces. SFG can identify chemical groups, concentration and orientation of molecules at an interface. A friction cell was developed to study sliding of a smooth elastomeric lens against a sapphire surface. Experiments were done with dry sliding as well as lubricated sliding in the presence of linear alkane liquids. SFG spectra at the alkane/sapphire interface revealed ordering of the confined alkane molecules. These were more ordered than alkane liquid, but less ordered than alkane crystal. Cooling of the confined alkane below its melting temperature [TM] led to molecular orientation that was different from that of bulk crystal next to a sapphire surface. Molecules were oriented with their symmetry axis parallel to the surface normal. In addition, the melting temperature [Tconf] under confinement for a series of linear alkanes (n =15--27) showed a surprising trend. Intermediate molecular weights showed melting point depression. The T conf values suggested that melting started at the alkane/sapphire interface. In another investigation, confinement of water between an elastomeric PDMS lens and sapphire was studied. SFG spectra at the sapphire/water/PDMS interface revealed a heterogeneous morphology. The

Graphene oxide-based efficient and scalable solar desalination under one sun with a confined 2D water path.

Science.gov (United States)

Li, Xiuqiang; Xu, Weichao; Tang, Mingyao; Zhou, Lin; Zhu, Bin; Zhu, Shining; Zhu, Jia

2016-12-06

Because it is able to produce desalinated water directly using solar energy with minimum carbon footprint, solar steam generation and desalination is considered one of the most important technologies to address the increasingly pressing global water scarcity. Despite tremendous progress in the past few years, efficient solar steam generation and desalination can only be achieved for rather limited water quantity with the assistance of concentrators and thermal insulation, not feasible for large-scale applications. The fundamental paradox is that the conventional design of direct absorber-bulk water contact ensures efficient energy transfer and water supply but also has intrinsic thermal loss through bulk water. Here, enabled by a confined 2D water path, we report an efficient (80% under one-sun illumination) and effective (four orders salinity decrement) solar desalination device. More strikingly, because of minimized heat loss, high efficiency of solar desalination is independent of the water quantity and can be maintained without thermal insulation of the container. A foldable graphene oxide film, fabricated by a scalable process, serves as efficient solar absorbers (>94%), vapor channels, and thermal insulators. With unique structure designs fabricated by scalable processes and high and stable efficiency achieved under normal solar illumination independent of water quantity without any supporting systems, our device represents a concrete step for solar desalination to emerge as a complementary portable and personalized clean water solution.

Accurate calculation of conformational free energy differences in explicit water: the confinement-solvation free energy approach.

Science.gov (United States)

Esque, Jeremy; Cecchini, Marco

2015-04-23

The calculation of the free energy of conformation is key to understanding the function of biomolecules and has attracted significant interest in recent years. Here, we present an improvement of the confinement method that was designed for use in the context of explicit solvent MD simulations. The development involves an additional step in which the solvation free energy of the harmonically restrained conformers is accurately determined by multistage free energy perturbation simulations. As a test-case application, the newly introduced confinement/solvation free energy (CSF) approach was used to compute differences in free energy between conformers of the alanine dipeptide in explicit water. The results are in excellent agreement with reference calculations based on both converged molecular dynamics and umbrella sampling. To illustrate the general applicability of the method, conformational equilibria of met-enkephalin (5 aa) and deca-alanine (10 aa) in solution were also analyzed. In both cases, smoothly converged free-energy results were obtained in agreement with equilibrium sampling or literature calculations. These results demonstrate that the CSF method may provide conformational free-energy differences of biomolecules with small statistical errors (below 0.5 kcal/mol) and at a moderate computational cost even with a full representation of the solvent.

Fusion, magnetic confinement

International Nuclear Information System (INIS)

Berk, H.L.

1992-01-01

An overview is presented of the principles of magnetic confinement of plasmas for the purpose of achieving controlled fusion conditions. Sec. 1 discusses the different nuclear fusion reactions which can be exploited in prospective fusion reactors and explains why special technologies need to be developed for the supply of tritium or 3 He, the probable fuels. In Sec. 2 the Lawson condition, a criterion that is a measure of the quality of confinement relative to achieving fusion conditions, is explained. In Sec. 3 fluid equations are used to describe plasma confinement. Specific confinement configurations are considered. In Sec. 4 the orbits of particle sin magneti and electric fields are discussed. In Sec. 5 stability considerations are discussed. It is noted that confinement systems usually need to satisfy stability constraints imposed by ideal magnetohydrodynamic (MHD) theory. The paper culminates with a summary of experimental progress in magnetic confinement. Present experiments in tokamaks have reached the point that the conditions necessary to achieve fusion are being satisfied

Initial assessment of MHTGR confinement releases

International Nuclear Information System (INIS)

Maneke, J.L.; Lanning, D.D.; Lidsky, L.M.

1986-01-01

Initial investigation of Modular High Temperature Gas-Cooled Reactor (MHTGR) designs suggest that source terms during postulated accidents will be considerably lower than Light Water Reactor (LWR) source term estimates. These lower postulated accident releases are not only a safety incentive, but also an economic incentive for the development of this reactor type. For example, it is hoped that a filtered confinement building, rather than a more expensive LWR-like containment building, would adequately protect the public from radiological releases. The ability of a confinement building to satisfy safety requirements for the MHTGR depends on several reactor parameters, such as fuel quality, reactor design, and the design of the reactor building. SCIMCA, a Simple Code for Initial MHTGR Confinement Assessment has been developed for preliminary MHTGR building requirement calculations. The code is capable of modeling a decay chain with a maximum of five regions. Phenomena such as fission product decay and buildup, natural deposition, building filtration, and intercompartmental transport are incorporated. SCIMCA models reduction mechanisms, such as dispersion and decay, occurring as radioactivity is transported through the environment. A subroutine for calculating doses at specified distances has also been included

煤层底板承压水导升带影响因素正交模拟试验%Orthogonal test of the influential factors of confined water-conducting zone in coal floor

Institute of Scientific and Technical Information of China (English)

边凯; 杨志斌

2016-01-01

Confined water-conducting zone is an important factor for mining safety assessment in mining under water pressure, in order to study the role of the influential factors, based on the fluid-solid coupling theory, the hydrogeological conceptual model and numerical model of coal floor water inrush was established, then orthogonal simulation test of five factors and five levels was carried out by using numerical simulation software FLAC3D. The results show that confined water-conducting height is closely related to water pressure of aquifer and permeability coefficient of aquiclude, the greater the confined water pressure and permeability coefficient, the higher the initial water-conducting height. The influential order of the factors for the experimental results isE>C>D>B>A,E (permeability coefficient of aquiclude) andC (confined water pressure) significantly affect the result of the experiment. Different initial head pressure cause different head pressure attenuation rate during the process of confined water conduction. The greater the initial head pressure, the greater the head decay rate, this will increase with the conducting height. The fact that the change of the influencial factors leads to the changes of confined water pressure reveals the law of coal floor confined water conductivity in coal mining process, provides the theoretical basis for the safe mining of coal under pressure.%承压水导升带是煤层带压开采安全评价的重要因素。为了综合研究其影响因素的作用，基于流–固耦合理论，建立了煤层底板突水的水文地质物理概念模型和数值模型，采用FLAC3D数值模拟软件开展了工作面宽度(A)、隔水层厚度(B)、承压水压力(C)、煤层埋深(D)、隔水层渗透系数(E)5个因素5水平的有空列正交模拟试验。结果表明：煤层底板承压水导升高度与底板含水层水压和隔水层渗透性关系密切；各因素对试验结果的影响程度强弱顺序是 E

Confinement models for gluons

International Nuclear Information System (INIS)

Khadkikar, S.B.; Vinodkumar, P.C.

1987-04-01

Confinement model for gluons using a 'colour super current' is formulated. An attempt has been made to derive a suitable dielectric function corresponding to the current confinement model. A simple inhomogeneous dielectric confinement model for gluons is studied for comparison. The model Hamiltonians are second quantized and the glueball states are constructed. The spurious motion of the centre of confinement is accounted for. The results of the current confinement scheme are found to be in good agreement with the experimental candidates for glueballs. (author). 16 refs, 3 tabs

Comments on confinement criteria

International Nuclear Information System (INIS)

Kurak, V.; Schroer, B.; Swieca, J.A.

1977-01-01

For a QED 2 model with SU(n) flavour, the nature of the physical states space is more subtle than one expects on the basis of the loop criterion for confinement. One may have colour confinement without confinement of the fundamental flavour representation. Attempts to formulate confinement criteria in which the quark fields play a more fundamental role are discussed [pt

Development of compact tritium confinement system using gas separation membrane

International Nuclear Information System (INIS)

Hayashi, Takumi; Okuno, Kenji

1994-01-01

In order to develop more compact and cost-effective tritium confinement system for fusion reactor, a new system using gas separation membranes has been studied at the Tritium Process Laboratory in the Japan Atomic Energy Research Institute. The preliminary result showed that the gas separation membrane system could reduce processing volume of tritium contaminated gas to more than one order of magnitude compared with the conventional system, and that most of tritiated water vapor (humidity) could be directly recovered by water condenser before passing through dryer such as molecular sieves. More detail investigations of gas separation characteristics of membrane were started to design ITER Atmospheric Detritiation System (ADS). Furthermore, a scaled polyimide membrane module (hollow-filament type) loop was just installed to investigate the actual tritium confinement performance under various ITER-ADS conditions. (author)

Molecular rotation and dynamics in superfluid helium-4 nanodroplets

Science.gov (United States)

Callegari, Carlo

2000-11-01

Cavity-enhanced laser radiation, coupled to molecular- beam bolometric detection has been used to study the spectroscopy of acetylenic molecules embedded in helium nanodroplets. The 2ν1 transition (CH stretch overtone) of HCN, DCCH, NCCCH, CH3CCH, CF3CCH, (CH 3)3CCCH, (CH3)3SiCCH, has been investigated in the 1.5 μm spectral region by means of a color center laser coupled to a resonant build-up cavity, which enhances the laser power experienced by the molecules in the beam by up to a factor of 400, thus overcoming the weakness of the (dipole forbidden) transitions. All molecules are observed to rotate freely in the liquid cluster environment, with strongly enhanced moments of inertia, but with negligible matrix induced shifts (less than 1 cm-1). We show that this enhancement is largely accounted for by hydrodynamic effects, which we have modeled and numerically calculated. While in the gas phase the rotational lines have instrument-limited widths (a few MHZ), in the droplets we have observed linewidths ranging from 600 MHz for (CH3)3SiCCH to 2.8GHz for (CH3) 3CCCH. To investigate the nature of the broadening (which was widely believed to be homogeneous), we have performed a series of infrared (IR) saturation experiments on the 2ν1 transition. We have also thoroughly investigated NCCCH by means of microwave (MW) single-resonance experiments (on rotational transitions) and double-resonance (MW-MW and MW-IR) experiments. The results demonstrate that the spectral features of molecules in He droplets are inhomogeneously broadened, and allow an estimate of the importance of the different broadening contributions. In particular, MW-IR measurements show that the size of the cluster greatly affects the way rotational energy is relaxed. Large clusters seem to follow a ``strong collision model'' where memory of the initial rotational state is completely lost after each ``relaxation'' event, while for smaller clusters relaxation rates are probably affected by the lower

Molecular rotation and dynamics in superfluid ^4He nanodroplets

Science.gov (United States)

Callegari, Carlo

2001-05-01

Cavity-enhanced laser radiation, coupled to molecular-beam bolometric detection has been used to study the spectroscopy of acetylenic molecules embedded in helium nanodroplets. The 2ν1 transition (CH stretch overtone) of HCN, DCCH, NCCCH, CH_3CCH, CF_3CCH, (CH_3)_3CCCH, (CH_3)_3SiCCH, has been investigated in the 1.5 μm spectral region by means of a color center laser coupled to a resonant buildup cavity, which enhances the laser power experienced by the molecules in the beam by up to a factor of 400, thus overcoming the weakness of the (harmonically forbidden) transitions. All molecules are observed to rotate freely in the liquid cluster environment, with strongly enhanced moments of inertia, but with negligible matrix induced shifts (less than 1 cm-1). We show that this enhancement is largely accounted for by hydrodynamic effects, which we have modeled and numerically calculated. While in the gas phase the rotational lines have instrument-limited widths (a few MHz), in the droplets we have observed linewidths ranging from 600 MHz for (CH_3)_3SiCCH to 2.8 GHz for (CH_3)_3CCCH. To investigate the nature of the broadening (which was widely believed to be homogeneous), we have performed a series of infrared (IR) saturation experiments on the 2ν1 transition. We have also thoroughly investigated NCCCH by means of microwave (MW) single-resonance experiments (on rotational transitions) and double-resonance (MW-MW and MW-IR) experiments. The results demonstrate that the spectral features of molecules in He droplets are inhomogeneously broadened, and allow an estimate of the importance of the different broadening contributions. In particular, MW-IR measurements show that the size of the cluster greatly affects the way rotational energy is relaxed. Large clusters seem to follow a ``strong collision model'' where memory of the initial rotational state is completely lost after each ``relaxation'' event, while for smaller clusters relaxation rates are probably affected by

Gluon confinement

International Nuclear Information System (INIS)

Novello, M.; Lorenci, V.A. de; Elbaz, E.

1997-02-01

In this paper we present a new model for a gauge field theory such that self-interacting spin-one particles can be confined in a compact domain. The necessary conditions to produce the confining potential appear already in the properties of the eikonal structure generated by the particular choice of the dynamics. (author)

Development of Interfacial Structure in a Confined Air-Water Cap-Turbulent and Churn-Turbulent Flow

International Nuclear Information System (INIS)

Sun, X.; Kim, S.; Cheng, L.; Ishii, M.; Beus, S.G.

2001-01-01

The objective of the present work is to study and model the interfacial structure development of air-water two-phase flow in a confined test section. Experiments of a total of 9 flow conditions in a cap-turbulent and churn-turbulent flow regimes are carried out in a vertical air-water upward two-phase flow experimental loop with a test section of 20-cm in width and 1-cm in gap. The miniaturized four-sensor conductivity probes are used to measure local two-phase parameters at three different elevations for each flow condition. The bubbles captured by the probes are categorized into two groups in view of the two-group interfacial area transport equation, i.e., spherical/distorted bubbles as Group 1 and cap/churn-turbulent bubbles as Group 2. The acquired parameters are time-averaged local void fraction, interfacial velocity, bubble number frequency, interfacial area concentration, and bubble Sauter mean diameter for both groups of bubbles. Also, the line-averaged and area-averaged data are presented and discussed. The comparisons of these parameters at different elevations demonstrate the development of interfacial structure along the flow direction due to bubble interactions

Development of Interfacial Structure in a Confined Air-Water Cap-Turbulent and Churn-Turbulent Flow

International Nuclear Information System (INIS)

Xiaodong Sun; Seungjin Kim; Ling Cheng; Mamoru Ishii; Beus, Stephen G.

2002-01-01

The objective of the present work is to study and model the interfacial structure development of air-water two-phase flow in a confined test section. Experiments of a total of 9 flow conditions in cap-turbulent and churn-turbulent flow regimes are carried out in a vertical air-water upward two-phase flow experimental loop with a test section of 200-mm in width and 10-mm in gap. Miniaturized four-sensor conductivity probes are used to measure local two-phase parameters at three different elevations for each flow condition. The bubbles captured by the probes are categorized into two groups in view of the two-group interfacial area transport equation, i.e., spherical/distorted bubbles as Group 1 and cap/churn-turbulent bubbles as Group 2. The acquired parameters are time-averaged local void fraction, interfacial velocity, bubble number frequency, interfacial area concentration, and bubble Sauter mean diameter for both groups of bubbles. Also, the line-averaged and area-averaged data are presented and discussed. The comparisons of these parameters at different elevations demonstrate the development of interfacial structure along the flow direction due to bubble interactions. (authors)

Building solids inside nano-space: from confined amorphous through confined solvate to confined 'metastable' polymorph.

Science.gov (United States)

Nartowski, K P; Tedder, J; Braun, D E; Fábián, L; Khimyak, Y Z

2015-10-14

The nanocrystallisation of complex molecules inside mesoporous hosts and control over the resulting structure is a significant challenge. To date the largest organic molecule crystallised inside the nano-pores is a known pharmaceutical intermediate - ROY (259.3 g mol(-1)). In this work we demonstrate smart manipulation of the phase of a larger confined pharmaceutical - indomethacin (IMC, 357.8 g mol(-1)), a substance with known conformational flexibility and complex polymorphic behaviour. We show the detailed structural analysis and the control of solid state transformations of encapsulated molecules inside the pores of mesoscopic cellular foam (MCF, pore size ca. 29 nm) and controlled pore glass (CPG, pore size ca. 55 nm). Starting from confined amorphous IMC we drive crystallisation into a confined methanol solvate, which upon vacuum drying leads to the stabilised rare form V of IMC inside the MCF host. In contrast to the pure form, encapsulated form V does not transform into a more stable polymorph upon heating. The size of the constraining pores and the drug concentration within the pores determine whether the amorphous state of the drug is stabilised or it recrystallises into confined nanocrystals. The work presents, in a critical manner, an application of complementary techniques (DSC, PXRD, solid-state NMR, N2 adsorption) to confirm unambiguously the phase transitions under confinement and offers a comprehensive strategy towards the formation and control of nano-crystalline encapsulated organic solids.

Fractional governing equations of transient groundwater flow in confined aquifers with multi-fractional dimensions in fractional time

OpenAIRE

M. L. Kavvas; T. Tu; A. Ercan; J. Polsinelli

2017-01-01

Using fractional calculus, a dimensionally consistent governing equation of transient, saturated groundwater flow in fractional time in a multi-fractional confined aquifer is developed. First, a dimensionally consistent continuity equation for transient saturated groundwater flow in fractional time and in a multi-fractional, multidimensional confined aquifer is developed. For the equation of water flux within a multi-fractional multidimensional confined aquifer, a dimensionally...

Confinement of Reinforced-Concrete Columns with Non-Code Compliant Confining Reinforcement plus Supplemental Pen-Binder

Directory of Open Access Journals (Sweden)

Anang Kristianto

2012-11-01

Full Text Available One of the important requirements for earthquake resistant building related to confinement is the use of seismic hooks in the hoop or confining reinforcement of reinforced-concrete column elements. However, installation of a confining reinforcement with a 135-degree hook is not easy. Therefore, in practice, many construction workers apply a confining reinforcement with a 90-degreehook (non-code compliant. Based on research and records of recent earthquakes in Indonesia, the use of a non-code compliant confining reinforcement for concrete columns produces structures with poor seismic performance. This paper presents a study that introduces an additional element that is expected to improve the effectiveness of concrete columns confined with a non-code compliant confining reinforcement. The additional element, named a pen-binder, is used to keep the non-code compliant confining reinforcement in place. The effectiveness of this element under pure axial concentric loading was investigatedcomprehensively.The specimens tested in this study were 18 concrete columns,with a cross-section of 170 mm x 170 mm and a height of 480 mm. The main test variables were the material type of the pen-binder, the angle of the hook, and the confining reinforcement configuration.The test results indicate that adding pen-binders can effectively improve the strength and ductility of the column specimens confined with a non-code compliant confining reinforcement

Plasma confinement

CERN Document Server

Hazeltine, R D

2003-01-01

Detailed and authoritative, this volume examines the essential physics underlying international research in magnetic confinement fusion. It offers readable, thorough accounts of the fundamental concepts behind methods of confining plasma at or near thermonuclear conditions. Designed for a one- or two-semester graduate-level course in plasma physics, it also represents a valuable reference for professional physicists in controlled fusion and related disciplines.

Molecular dynamics of nanodroplet impact: The effect of the projectile’s molecular mass on sputtering

Energy Technology Data Exchange (ETDEWEB)

Saiz, Fernan [Department of Chemistry, Imperial College of Science, Technology and Medicine, South Kensington, London, SW7 2A7 (United Kingdom); Gamero-Castaño, Manuel, E-mail: mgameroc@uci.edu [Department of Mechanical and Aerospace Engineering, University of California, Irvine, California, 92697 (United States)

2016-06-15

The impact of electrosprayed nanodroplets on ceramics at several km/s alters the atomic order of the target, causing sputtering, surface amorphization and cratering. The molecular mass of the projectile is known to have a strong effect on the impact phenomenology, and this article aims to rationalize this dependency using molecular dynamics. To achieve this goal, the article models the impact of four projectiles with molecular masses between 45 and 391 amu, and identical diameters and kinetic energies, 10 nm and 63 keV, striking a silicon target. In agreement with experiments, the simulations show that the number of sputtered atoms strongly increases with molecular mass. This is due to the increasing intensity of collision cascades with molecular mass: when the fixed kinetic energy of the projectile is distributed among fewer, more massive molecules, their collisions with the target produce knock-on atoms with higher energies, which in turn generate more energetic and larger numbers of secondary and tertiary knock-on atoms. The more energetic collision cascades intensify both knock-on sputtering and, upon thermalization, thermal sputtering. Besides enhancing sputtering, heavier molecules also increase the fraction of the projectile’s energy that is transferred to the target, as well as the fraction of this energy that is dissipated.

Molecular dynamics of nanodroplet impact: The effect of the projectile’s molecular mass on sputtering

International Nuclear Information System (INIS)

Saiz, Fernan; Gamero-Castaño, Manuel

2016-01-01

The impact of electrosprayed nanodroplets on ceramics at several km/s alters the atomic order of the target, causing sputtering, surface amorphization and cratering. The molecular mass of the projectile is known to have a strong effect on the impact phenomenology, and this article aims to rationalize this dependency using molecular dynamics. To achieve this goal, the article models the impact of four projectiles with molecular masses between 45 and 391 amu, and identical diameters and kinetic energies, 10 nm and 63 keV, striking a silicon target. In agreement with experiments, the simulations show that the number of sputtered atoms strongly increases with molecular mass. This is due to the increasing intensity of collision cascades with molecular mass: when the fixed kinetic energy of the projectile is distributed among fewer, more massive molecules, their collisions with the target produce knock-on atoms with higher energies, which in turn generate more energetic and larger numbers of secondary and tertiary knock-on atoms. The more energetic collision cascades intensify both knock-on sputtering and, upon thermalization, thermal sputtering. Besides enhancing sputtering, heavier molecules also increase the fraction of the projectile’s energy that is transferred to the target, as well as the fraction of this energy that is dissipated.

A GIS-based, confined aquifer, hypothetical model of ground-water seepage into a former mining open pit

International Nuclear Information System (INIS)

Salama, A; Negeed, E.R.

2010-01-01

Groundwater seepage into a former mining site in Egypt is proposed for simulation. This site was used for basalt extraction. After the mining activities had stopped a large open pit was left over and groundwater seeped into the pit forming a lake. The pit has a dimension of approximately 1200 x 600 x 30 m. Because of the lack of field data, several scenarios may be hypothesized to explain the filling of these open pits with water. In this paper, one of these scenarios is studied. It is suggested that this water comes from an underneath confined aquifer. Through fractures in the host rock, water seeped upwards into the open pit. To estimate the rate at which water seeps into the lake, numerical study based on the finite element method is performed. Firstly, geo-referencing of the site was performed using GIS. The boundary of the lake was then digitized and elevation contours was defined. These data was then imported into grid-builder software to generate a two-dimensional triangular mesh which was then used by hydro-geosphere software to build the three-dimensional mesh and solve the problem. It was found that the set of discrete fractures was insufficient to fill the lake in the time span that was actually elapsed to fill up the lake which is on the order of two to three years.

Quark confinement

International Nuclear Information System (INIS)

Joos, H.

1976-07-01

The main topics of these lectures are: phenomenological approach to quark confinement, standard Lagrangian of hadrondynamics, Lagrangian field theory and quark confinement, classical soliton solutions in a simple model, quantization of extended systems, colour charge screening and quantization on a lattice and remarks on applications. A survey of the scientific publications listed according to the topics until 26 March 1976 is supplemented. (BJ) [de

Hydrophobic Ice Confined between Graphene and MoS2

NARCIS (Netherlands)

Bampoulis, Pantelis; Teernstra, V.J.; Lohse, Detlef; Zandvliet, Henricus J.W.; Poelsema, Bene

2016-01-01

The structure and nature of water confined between hydrophobic molybdenum disulfide (MoS2) and graphene (Gr) are investigated at room temperature by means of atomic force microscopy. We find the formation of two-dimensional (2D) crystalline ice layers. In contrast to the hexagonal ice “bilayers” of

Single-particle and collective dynamics of methanol confined in carbon nanotubes: a computer simulation study

International Nuclear Information System (INIS)

Garberoglio, Giovanni

2010-01-01

We present the results of computer simulations of methanol confined in carbon nanotubes. Different levels of confinement were identified as a function of the nanotube radius and characterized using a pair-distribution function adapted to the cylindrical geometry of these systems. Dynamical properties of methanol were also analysed as a function of the nanotube size, both at the level of single-particle and collective properties. We found that confinement in narrow carbon nanotubes strongly affects the dynamical properties of methanol with respect to the bulk phase, due to the strong interaction with the carbon nanotube. In the other cases, confined methanol shows properties quite similar to those of the bulk phase. These phenomena are related to the peculiar hydrogen bonded network of methanol and are compared to the behaviour of water confined in similar conditions. The effect of nanotube flexibility on the dynamical properties of confined methanol is also discussed.

Chernobyl new safe confinement

International Nuclear Information System (INIS)

Dodd, L.

2011-01-01

The author presents the new safe confinement that will be commissioned at Unit 4 of the Chernobyl NPP in 2015. The confinement will ensure that Chernobyl Unit 4 will be placed in an environmentally safe condition for at least next 100 years. The article highlights the current work status, future perspectives and the feasibility of confinement concept [ru

Procedure for the reversible confinement of gases or vapours in a natural or synthetic zeolite

International Nuclear Information System (INIS)

1980-01-01

The zeolite is treated with silane at a temperature of 100-140 0 C to silanise it in the H-form. This narrows the pores in the zeolite and the grains bind together creating cavities. The silanised zeolite and the material to be confined are brought into contact at high pressure, for example at an excess pressure of 0.5 atm. Contact is continued until the required quantity of gas or vapour has been adsorbed by the zeolite. Under the same high pressure water is added to the system which causes further narrowing of the pores. Preferably the process of silanising and treating with water is then repeated one or more times to close the pores and ensure confinement. The process is reversed by heating the product above 300 0 C. The bonds formed by silanising are then broken and the confined material is liberated. This process has applications in the confinement of valuable gases such as enriched isotopes, and of dangerous gases such as radioactive waste gases. (Th.W.P.)

Tokamak confinement scaling laws

International Nuclear Information System (INIS)

Connor, J.

1998-01-01

The scaling of energy confinement with engineering parameters, such as plasma current and major radius, is important for establishing the size of an ignited fusion device. Tokamaks exhibit a variety of modes of operation with different confinement properties. At present there is no adequate first principles theory to predict tokamak energy confinement and the empirical scaling method is the preferred approach to designing next step tokamaks. This paper reviews a number of robust theoretical concepts, such as dimensional analysis and stability boundaries, which provide a framework for characterising and understanding tokamak confinement and, therefore, generate more confidence in using empirical laws for extrapolation to future devices. (author)

Self-Assembly of Diblock Molecular Polymer Brushes in the Spherical Confinement of Nanoemulsion Droplets.

Science.gov (United States)

Steinhaus, Andrea; Pelras, Théophile; Chakroun, Ramzi; Gröschel, André H; Müllner, Markus

2018-05-02

Understanding the self-assembly behavior of polymers of various topologies is key to a reliable design of functional polymer materials. Self-assembly under confinement conditions emerges as a versatile avenue to design polymer particles with complex internal morphologies while simultaneously facilitating scale-up. However, only linear block copolymers have been studied to date, despite the increasing control over macromolecule composition and architecture available. This study extends the investigation of polymer self-assembly in confinement from regular diblock copolymers to diblock molecular polymer brushes (MPBs). Block-type MPBs with polystyrene (PS) and polylactide (PLA) compartments of different sizes are incorporated into surfactant-stabilized oil-in-water (chloroform/water) emulsions. The increasing confinement in the nanoemulsion droplets during solvent evaporation directs the MPBs to form solid nano/microparticles. Microscopy studies reveal an intricate internal particle structure, including interpenetrating networks and axially stacked lamellae of PS and PLA, depending on the PS/PLA ratio of the brushes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Role of Confined Water in Underwater Adhesion

Science.gov (United States)

Dhinojwala, Ali

Surface bound water is a strong deterrent for forming strong bonds between two surfaces underwater and expelling that bound water is important for strong adhesion. I will discuss examples of different strategies used by geckos, spiders, and mussels to handle this last layer of bound water. Recent results using infrared-visible sum frequency generation spectroscopy to probe the structure of this bound water will be discussed. National Science Foundation.

The confinement problem

International Nuclear Information System (INIS)

Seiler, E.

1985-01-01

Confinement of quarks is sometimes taken as some kind of dogma in the contemporary theory of strong interactions - quantum chromo-dynamics (QCD). Scientists should not be content with that. What is meant by ''permanent confinement'' should be formulated more precisely to see whether the theory has this property or not. The author looks at some possible interpretations of ''confinement'' and their shortcomings and then turns to the most widely used rather pragmatic definition based on the somewhat unphysical notion of infinitely heavy external sources. He describes what is known about the problem and tries to bring into focus some aspects that are insufficiently understood in his opinion

Pattern replication by confined dewetting

NARCIS (Netherlands)

Harkema, S.; Schäffer, E.; Morariu, M.D.; Steiner, U

2003-01-01

The dewetting of a polymer film in a confined geometry was employed in a pattern-replication process. The instability of dewetting films is pinned by a structured confining surface, thereby replicating its topographic pattern. Depending on the surface energy of the confining surface, two different

Clays in natural and engineered barriers for radioactive waste confinement

International Nuclear Information System (INIS)

2007-01-01

The meeting covers all topics concerning natural argillaceous geological barriers and the clay material based engineered barrier systems, investigated by means of: laboratory experiments on clay samples (new analytical developments), in situ experiments in underground research laboratories, mock-up demonstrations, natural analogues, as well as numerical modelling and global integration approaches (including up-scaling processes and treatment of uncertainties). The works presented deal with: examples of broad research programs (national or international) on the role of natural and artificial clay barriers for radionuclide confinement; clay-based repository concepts: repository designs, including technological and safety issues related to the use of clay for nuclear waste confinement; geology and clay characterisation: mineralogy, sedimentology, paleo-environment, diagenesis, dating techniques, discontinuities in rock clay, fracturing, self sealing processes, role of organic matter and microbiological processes; geochemistry: pore water geochemistry, clay thermodynamics, chemical retention, geochemical modelling, advanced isotopic geochemistry; mass transfer: water status and hydraulic properties in low permeability media, pore space geometry, water, solute and gas transfer processes, colloid mediated transport, large scale movements, long-term diffusion; alteration processes: oxidation effects, hydration-dehydration processes, response to thermal stress, iron-clay interactions, alkaline perturbation; geomechanics: thermo-hydro-mechanical behaviour of clay, rheological models, EDZ characterisation and evolution, coupled behaviour and models (HM, THM, THMC). A particular interest is given to potential contributions coming from fields of activities other than radioactive waste management, which take advantage of the confinement properties of the clay barrier (oil and gas industries, gas geological storage, CO 2 geological sequestration, chemical waste isolation

Clays in natural and engineered barriers for radioactive waste confinement

Energy Technology Data Exchange (ETDEWEB)

NONE

2007-07-01

The meeting covers all topics concerning natural argillaceous geological barriers and the clay material based engineered barrier systems, investigated by means of: laboratory experiments on clay samples (new analytical developments), in situ experiments in underground research laboratories, mock-up demonstrations, natural analogues, as well as numerical modelling and global integration approaches (including up-scaling processes and treatment of uncertainties). The works presented deal with: examples of broad research programs (national or international) on the role of natural and artificial clay barriers for radionuclide confinement; clay-based repository concepts: repository designs, including technological and safety issues related to the use of clay for nuclear waste confinement; geology and clay characterisation: mineralogy, sedimentology, paleo-environment, diagenesis, dating techniques, discontinuities in rock clay, fracturing, self sealing processes, role of organic matter and microbiological processes; geochemistry: pore water geochemistry, clay thermodynamics, chemical retention, geochemical modelling, advanced isotopic geochemistry; mass transfer: water status and hydraulic properties in low permeability media, pore space geometry, water, solute and gas transfer processes, colloid mediated transport, large scale movements, long-term diffusion; alteration processes: oxidation effects, hydration-dehydration processes, response to thermal stress, iron-clay interactions, alkaline perturbation; geomechanics: thermo-hydro-mechanical behaviour of clay, rheological models, EDZ characterisation and evolution, coupled behaviour and models (HM, THM, THMC). A particular interest is given to potential contributions coming from fields of activities other than radioactive waste management, which take advantage of the confinement properties of the clay barrier (oil and gas industries, gas geological storage, CO{sub 2} geological sequestration, chemical waste isolation

Dielectric Properties of Water in Butter and Water-AOT-Heptane Systems Measured using Terahertz Time-Domain Spectroscopy

DEFF Research Database (Denmark)

Møller, Uffe; Folkenberg, Jacob Riis; Jepsen, Peter Uhd

2010-01-01

We investigate the dielectric properties of water confined in nanometer-sized inverse micelles in mixtures of water, AOT, and heptane. We show that the dielectric properties of the confined water are dependent on the water pool size and different from those of bulk water. We also discuss...... the dielectric properties of different vegetable oils, lard, and butter, and use these properties to deduce the dielectric properties of water in butter, which are shown to deviate significantly from the dielectric properties of bulk water....

Morphometry and distribution of isolated caves as a guide for phreatic and confined paleohydrological conditions

Science.gov (United States)

Frumkin, Amos; Fischhendler, Itay

2005-04-01

Isolated caves are a special cave type common in most karst terrains, formed by prolonged slow water flow where aggressivity is locally boosted. The morphometry and distribution of isolated caves are used here to reconstruct the paleohydrology of a karstic mountain range. Within a homogenous karstic rock sequence, two main types of isolated caves are distinguished, and each is associated with a special hydrogeologic setting: maze caves form by rising water in the confined zone of the aquifer, under the Mt. Scopus Group (Israel) confinement, while chamber caves are formed in phreatic conditions, apparently by lateral flow mixing with a vadose input from above.

Capillary evaporation of the ionic liquid [EMIM][BF4] in nanoscale solvophobic confinement

Science.gov (United States)

Shrivastav, Gourav; Remsing, Richard C.; Kashyap, Hemant K.

2018-05-01

Solvent density fluctuations play a crucial role in liquid-vapor transitions in solvophobic confinement and can also be important for understanding solvation of polar and apolar solutes. In the case of ionic liquids (ILs), density fluctuations can be used to understand important processes in the context of nanoscale aggregation and colloidal self-assemblies. In this article, we explore the nature of density fluctuations associated with capillary evaporation of the IL 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) in the confined region of model solvophobic nanoscale sheets by using molecular dynamics simulations combined with non-Boltzmann sampling techniques. We demonstrate that density fluctuations of the confined IL play an important role in capillary evaporation, suggesting analogies to dewetting transitions involving water. Significant changes in the interfacial structure of the IL are also detailed and suggested to underlie a non-classical (non-parabolic) dependence of the free energy barrier to evaporation on the degree of confinement.

Conference summary: Experiments in confinement and plasma-wall interaction and innovative confinement concept

International Nuclear Information System (INIS)

Ninomiya, H.

2005-01-01

This paper summarizes the results presented at the 20th IAEA Fusion Energy Conference 2004 in the sessions of confinement, plasma-wall interaction and innovative confinement concept. The highlights of the presentations are as follows. Long pulse operation with high beta and high bootstrap fraction much longer than the current diffusion time has been achieved. The discharge scenario optimization and its extrapolation towards ITER have progressed remarkably. Significant progress has been made in understanding of global confinement and transport physics. (author)

Communication: energy benchmarking with quantum Monte Carlo for water nano-droplets and bulk liquid water.

Science.gov (United States)

Alfè, D; Bartók, A P; Csányi, G; Gillan, M J

2013-06-14

We show the feasibility of using quantum Monte Carlo (QMC) to compute benchmark energies for configuration samples of thermal-equilibrium water clusters and the bulk liquid containing up to 64 molecules. Evidence that the accuracy of these benchmarks approaches that of basis-set converged coupled-cluster calculations is noted. We illustrate the usefulness of the benchmarks by using them to analyze the errors of the popular BLYP approximation of density functional theory (DFT). The results indicate the possibility of using QMC as a routine tool for analyzing DFT errors for non-covalent bonding in many types of condensed-phase molecular system.

The confining trailing string

CERN Document Server

Kiritsis, E; Nitti, F

2014-01-01

We extend the holographic trailing string picture of a heavy quark to the case of a bulk geometry dual to a confining gauge theory. We compute the classical trailing confining string solution for a static as well as a uniformly moving quark. The trailing string is infinitely extended and approaches a confining horizon, situated at a critical value of the radial coordinate, along one of the space-time directions, breaking boundary rotational invariance. We compute the equations for the fluctuations around the classical solutions, which are used to obtain boundary force correlators controlling the Langevin dynamics of the quark. The imaginary part of the correlators has a non-trivial low-frequency limit, which gives rise to a viscous friction coefficient induced by the confining vacuum. The vacuum correlators are used to define finite-temperature dressed Langevin correlators with an appropriate high-frequency behavior.

A Review of Quantum Confinement

Science.gov (United States)

Connerade, Jean-Patrick

2009-12-01

A succinct history of the Confined Atom problem is presented. The hydrogen atom confined to the centre of an impenetrable sphere counts amongst the exactly soluble problems of physics, alongside much more noted exact solutions such as Black Body Radiation and the free Hydrogen atom in absence of any radiation field. It shares with them the disadvantage of being an idealisation, while at the same time encapsulating in a simple way particular aspects of physical reality. The problem was first formulated by Sommerfeld and Welker [1]—henceforth cited as SW—in connection with the behaviour of atoms at very high pressures, and the solution was published on the occasion of Pauli's 60th birthday celebration. At the time, it seemed that there was not much other connection with physical reality beyond a few simple aspects connected to the properties of atoms in solids, for which more appropriate models were soon developed. Thus, confined atoms attracted little attention until the advent of the metallofullerene, which provided the first example of a confined atom with properties quite closely related to those originally considered by SW. Since then, the problem has received much more attention, and many more new features of quantum confinement, quantum compression, the quantum Faraday cage, electronic reorganisation, cavity resonances, etc have been described, which are relevant to real systems. Also, a number of other situations have been uncovered experimentally to which quantum confinement is relevant. Thus, studies of the confined atom are now more numerous, and have been extended both in terms of the models used and the systems to which they can be applied. Connections to thermodynamics are explored through the properties of a confined two-level atom adapted from Einstein's celebrated model, and issues of dynamical screening of electromagnetic radiation by the confining shell are discussed in connection with the Faraday cage produced by a confining conducting shell

A Review of Quantum Confinement

International Nuclear Information System (INIS)

Connerade, Jean-Patrick

2009-01-01

A succinct history of the Confined Atom problem is presented. The hydrogen atom confined to the centre of an impenetrable sphere counts amongst the exactly soluble problems of physics, alongside much more noted exact solutions such as Black Body Radiation and the free Hydrogen atom in absence of any radiation field. It shares with them the disadvantage of being an idealisation, while at the same time encapsulating in a simple way particular aspects of physical reality. The problem was first formulated by Sommerfeld and Welker - henceforth cited as SW - in connection with the behaviour of atoms at very high pressures, and the solution was published on the occasion of Pauli's 60th birthday celebration. At the time, it seemed that there was not much other connection with physical reality beyond a few simple aspects connected to the properties of atoms in solids, for which more appropriate models were soon developed. Thus, confined atoms attracted little attention until the advent of the metallofullerene, which provided the first example of a confined atom with properties quite closely related to those originally considered by SW. Since then, the problem has received much more attention, and many more new features of quantum confinement, quantum compression, the quantum Faraday cage, electronic reorganisation, cavity resonances, etc have been described, which are relevant to real systems. Also, a number of other situations have been uncovered experimentally to which quantum confinement is relevant. Thus, studies of the confined atom are now more numerous, and have been extended both in terms of the models used and the systems to which they can be applied. Connections to thermodynamics are explored through the properties of a confined two-level atom adapted from Einstein's celebrated model, and issues of dynamical screening of electromagnetic radiation by the confining shell are discussed in connection with the Faraday cage produced by a confining conducting shell. The

PREFACE: Water at interfaces Water at interfaces

Science.gov (United States)

Gallo, P.; Rovere, M.

2010-07-01

This special issue is devoted to illustrating important aspects and significant results in the field of modeling and simulation of water at interfaces with solutes or with confining substrates, focusing on a range of temperatures from ambient to supercooled. Understanding the behavior of water, in contact with different substrates and/or in solutions, is of pivotal importance for a wide range of applications in physics, chemistry and biochemistry. Simulations of confined and/or interfacial water are also relevant for testing how different its behavior is with respect to bulk water. Simulations and modeling in this field are of particular importance when studying supercooled regions where water shows anomalous properties. These considerations motivated the organization of a workshop at CECAM in the summer of 2009 which aimed to bring together scientists working with computer simulations on the properties of water in various environments with different methodologies. In this special issue, we collected a variety of interesting contributions from some of the speakers of the workshop. We have roughly classified the contributions into four groups. The papers of the first group address the properties of interfacial and confined water upon supercooling in an effort to understand the relation with anomalous behavior of supercooled bulk water. The second group deals with the specific problem of solvation. The next group deals with water in different environments by considering problems of great importance in technological and biological applications. Finally, the last group deals with quantum mechanical calculations related to the role of water in chemical processes. The first group of papers is introduced by the general paper of Stanley et al. The authors discuss recent progress in understanding the anomalies of water in bulk, nanoconfined, and biological environments. They present evidence that liquid water may display 'polymorphism', a property that can be present in

Confinement at large-N

International Nuclear Information System (INIS)

Klinkhamer, F.R.

1985-06-01

Recent numerical results indicate that QCD in the limit of an infinite number (N) of colors also has confinement and moreover that it looks rather similar to normal QCD with N = 3 colors. This imposes severe restrictions on what the mechanism of confinement can be

Block copolymer morphologies confined by square-shaped particle: Hard and soft confinement

International Nuclear Information System (INIS)

Zhang Qiyi; Yang Wenyan; Hu Kaiyan

2016-01-01

The self-assembly of diblock copolymers confined around one square-shaped particle is studied systematically within two-dimensional self-consistent field theory (SCFT). In this model, we assume that the thin block copolymer film is confined in the vicinity of a square-shaped particle by a homopolymer melt, which is equivalent to the poor solvents. Multiple sequences of square-shaped particle-induced copolymer aggregates with different shapes and self-assembled internal morphologies are predicted as functions of the particle size, the structural portion of the copolymer, and the volume fraction of the copolymer. A rich variety of aggregates are found with complex internal self-assembled morphologies including complex structures of the vesicle, with one or several inverted micelle surrounded by the outer monolayer with the particle confined in the core. These results demonstrate that the assemblies of diblock copolymers formed around the square-shaped particle in poor solvents are of immediate interest to the assembly of copolymer and the morphology of biomembrane in the confined environment, as well as to the transitions of vesicles to micelles. (paper)

Helium induced fine structure in the electronic spectra of anthracene derivatives doped into superfluid helium nanodroplets

International Nuclear Information System (INIS)

Pentlehner, D.; Slenczka, A.

2015-01-01

Electronic spectra of organic molecules doped into superfluid helium nanodroplets show characteristic features induced by the helium environment. Besides a solvent induced shift of the electronic transition frequency, in many cases, a spectral fine structure can be resolved for electronic and vibronic transitions which goes beyond the expected feature of a zero phonon line accompanied by a phonon wing as known from matrix isolation spectroscopy. The spectral shape of the zero phonon line and the helium induced phonon wing depends strongly on the dopant species. Phonon wings, for example, are reported ranging from single or multiple sharp transitions to broad (Δν > 100 cm −1 ) diffuse signals. Despite the large number of example spectra in the literature, a quantitative understanding of the helium induced fine structure of the zero phonon line and the phonon wing is missing. Our approach is a systematic investigation of related molecular compounds, which may help to shed light on this key feature of microsolvation in superfluid helium droplets. This paper is part of a comparative study of the helium induced fine structure observed in electronic spectra of anthracene derivatives with particular emphasis on a spectrally sharp multiplet splitting at the electronic origin. In addition to previously discussed species, 9-cyanoanthracene and 9-chloroanthracene will be presented in this study for the first time

Alternate fusion -- continuous inertial confinement

International Nuclear Information System (INIS)

Barnes, D.C.; Turner, L.; Nebel, R.A.

1993-01-01

The authors argue that alternate approaches to large tokamak confinement are appropriate for fusion applications if: (1) They do not require magnetic confinement of a much higher quality than demonstrated in tokamaks; (2) Their physics basis may be succinctly stated and experimentally tested; (3) They offer near-term applications to important technical problems; and (4) Their cost to proof-of-principle is low enough to be consistent with current budget realities. An approach satisfying all of these criteria is presented. Fusion systems based on continuous inertial confinement are described. In these approaches, the inertia of a nonequilibrium plasma is used to produce local concentrations of plasma density in space and/or time. One implementation (inertial electrostatic confinement) which has been investigated both experimentally and theoretically uses a system of electrostatic grids to accelerate plasma ions toward a spherical focus. This system produced a steady 2 x 10 10 D-T neutrons/second with an overall fusion gain of 10 -5 in a sphere of about 9 cm radius. Recent theoretical developments show how to raise the fusion gain to order unity or greater by replacing the internal grids by a combination of applied magnetic and electrostatic fields. In these approaches, useful thermonuclear conditions may be produced in a system as small as a few mm radius. Confinement is that of a nonneutralized plasma. A pure electron plasma with a radial beam velocity distribution is absolutely confined by an applied Penning trap field. Spherical convergence of the confined electrons forms a deep virtual cathode near r = 0, in which thermonuclear ions are absolutely confined at useful densities. The authors have examined the equilibrium, stability, and classical relaxation of such systems, and obtained many positive physics results. Equilibria exist for both pure electron and partially charge-neutralized systems with arbitrarily high core-plasma densities

Transition from confined to phreatic conditions as the factor controlling salinization and change in redox state, Upper subaquifer of the Judea Group, Israel

Science.gov (United States)

Gavrieli, Ittai; Burg, Avi; Guttman, Joseph

2002-08-01

An increase in salinity and change from oxic to anoxic conditions are observed in the Upper subaquifer of the Judea Group in the Kefar Uriyya pumping field at the western foothills of the Judea Mountains, Israel. Hydrogeological data indicate that the change, which occurs over a distance of only a few kilometers, coincides with a transition from confined to phreatic conditions in the aquifer. The deterioration in the water quality is explained as a result of seepage of more saline, organic-rich water from above, into the phreatic "roofed" part of the aquifer. The latter is derived from the bituminous chalky rocks of the Mount Scopus Group, which confine the aquifer in its southeastern part. In this confined part, water in perched horizons within the Mount Scopus Group cannot leak down and flow westward while leaching organic matter and accumulating salts. However, upon reaching the transition area from confined to phreatic conditions, seepage to the Judea Upper subaquifer is possible, thereby allowing it to be defined as a leaky aquifer. The incoming organic matter consumes the dissolved oxygen and allows bacterial sulfate reduction. The latter accounts for the H2S in the aquifer, as indicated by sulfur isotopic analyses of coexisting sulfate and sulfide. Thus, from an aquifer management point of view, in order to maintain the high quality of the water in the confined southeastern part of the Kefar Uriyya field, care should be taken not to draw the confined-roofed transition area further east by over pumping.

Enhanced ordering reduces electric susceptibility of liquids confined to graphene slit pores

Science.gov (United States)

Terrones, Jeronimo; Kiley, Patrick J.; Elliott, James A.

2016-01-01

The behaviours of a range of polar and non-polar organic liquids (acetone, ethanol, methanol, N-methyl-2-pyrrolidone (NMP), carbon tetrachloride and water) confined to 2D graphene nanochannels with thicknesses in the range of 4.5 Å to 40 Å were studied using classical molecular dynamics and hybrid density functional theory. All liquids were found to organise spontaneously into ordered layers parallel to the confining surfaces, with those containing polar molecules having their electric dipoles aligned parallel to such surfaces. In particular, monolayers of NMP showed remarkable in-plane ordering and low molecular mobility, suggesting the existence of a previously unknown 2D solid-like phase. Calculations for polar liquids showed dramatically reduced static permittivities normal to the confining surfaces; these changes are expected to improve electron tunnelling across the liquid films, modifying the DC electrical properties of immersed assemblies of carbon nanomaterials. PMID:27265098

Elmo bumpy square plasma confinement device

Science.gov (United States)

Owen, L.W.

1985-01-01

The invention is an Elmo bumpy type plasma confinement device having a polygonal configuration of closed magnet field lines for improved plasma confinement. In the preferred embodiment, the device is of a square configuration which is referred to as an Elmo bumpy square (EBS). The EBS is formed by four linear magnetic mirror sections each comprising a plurality of axisymmetric assemblies connected in series and linked by 90/sup 0/ sections of a high magnetic field toroidal solenoid type field generating coils. These coils provide corner confinement with a minimum of radial dispersion of the confined plasma to minimize the detrimental effects of the toroidal curvature of the magnetic field. Each corner is formed by a plurality of circular or elliptical coils aligned about the corner radius to provide maximum continuity in the closing of the magnetic field lines about the square configuration confining the plasma within a vacuum vessel located within the various coils forming the square configuration confinement geometry.

Summary and evaluation of hydraulic property data available for the Hanford Site upper basalt confined aquifer system

International Nuclear Information System (INIS)

Spane, F.A. Jr.; Vermeul, V.R.

1994-09-01

Pacific Northwest Laboratory, as part of the Hanford Site Ground-Water Surveillance Project, examines the potential for offsite migration of contamination within the upper basalt confined aquifer system. For the past 40 years, hydrologic testing of the upper basalt confined aquifer has been conducted by a number of Hanford Site programs. Hydraulic property estimates are important for evaluating aquifer flow characteristics (i.e., ground-water flow patterns, flow velocity, transport travel time). Presented are the first comprehensive Hanford Site-wide summary of hydraulic properties for the upper basalt confined aquifer system (i.e., the upper Saddle Mountains Basalt). Available hydrologic test data were reevaluated using recently developed diagnostic test analysis methods. A comparison of calculated transmissivity estimates indicates that, for most test results, a general correspondence within a factor of two between reanalysis and previously reported test values was obtained. For a majority of the tests, previously reported values are greater than reanalysis estimates. This overestimation is attributed to a number of factors, including, in many cases, a misapplication of nonleaky confined aquifer analysis methods in previous analysis reports to tests that exhibit leaky confined aquifer response behavior. Results of the test analyses indicate a similar range for transmissivity values for the various hydro-geologic units making up the upper basalt confined aquifer. Approximately 90% of the calculated transmissivity values for upper basalt confined aquifer hydrogeologic units occur within the range of 10 0 to 10 2 m 2 /d, with 65% of the calculated estimate values occurring between 10 1 to 10 2 m 2 d. These summary findings are consistent with the general range of values previously reported for basalt interflow contact zones and sedimentary interbeds within the Saddle Mountains Basalt

Anomalous water expulsion from carbon-based rods at high humidity

Science.gov (United States)

Nune, Satish K.; Lao, David B.; Heldebrant, David J.; Liu, Jian; Olszta, Matthew J.; Kukkadapu, Ravi K.; Gordon, Lyle M.; Nandasiri, Manjula I.; Whyatt, Greg; Clayton, Chris; Gotthold, David W.; Engelhard, Mark H.; Schaef, Herbert T.

2016-09-01

Three water adsorption-desorption mechanisms are common in inorganic materials: chemisorption, which can lead to the modification of the first coordination sphere; simple adsorption, which is reversible; and condensation, which is irreversible. Regardless of the sorption mechanism, all known materials exhibit an isotherm in which the quantity of water adsorbed increases with an increase in relative humidity. Here, we show that carbon-based rods can adsorb water at low humidity and spontaneously expel about half of the adsorbed water when the relative humidity exceeds a 50-80% threshold. The water expulsion is reversible, and is attributed to the interfacial forces between the confined rod surfaces. At wide rod spacings, a monolayer of water can form on the surface of the carbon-based rods, which subsequently leads to condensation in the confined space between adjacent rods. As the relative humidity increases, adjacent rods (confining surfaces) in the bundles are drawn closer together via capillary forces. At high relative humidity, and once the size of the confining surfaces has decreased to a critical length, a surface-induced evaporation phenomenon known as solvent cavitation occurs and water that had condensed inside the confined area is released as a vapour.

Diffusion of water adsorbed in hydrotalcite: neutron scattering Study

Energy Technology Data Exchange (ETDEWEB)

Mitra, S [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai (India); Pramanik, A [Unilever Research India, Bangalore 500 066 (India); Chakrabarty, D [Godrej Sara Lee Limited, Research and Development Centre, Mumbai 400 079 (India); Juranyi, F [Laboratory for Neutron Scattering, ETHZ and PSI, CH-5232 Villigen PSI (Switzerland); Gautam, S [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai (India); Mukhopadhyay, R [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai (India)

2007-12-15

Layered double hydroxides (LDH) are a class of ionic lamellar solids with positively charged layers of two kinds of metallic cations and exchangeable hydrated anions. Quasi-elastic neutron scattering (QENS) measurements are performed in this type of LDH structured hydrated hydrotalcite sample to study the dynamical behaviour of the water in geometric confinement within the layers. Dynamical parameters correspond to the confined water molecules revealed that depending on the amount of excess water present, behaves differently and approaches bulk values at high concentration. Both translational and rotational dynamical parameters showed that at very low concentration of excess water, water molecules are attached to the surfaces and show the confinement effect.

Generating equilateral random polygons in confinement III

International Nuclear Information System (INIS)

Diao, Y; Ernst, C; Montemayor, A; Ziegler, U

2012-01-01

In this paper we continue our earlier studies (Diao et al 2011 J. Phys. A: Math. Theor. 44 405202, Diao et al J. Phys. A: Math. Theor. 45 275203) on the generation methods of random equilateral polygons confined in a sphere. The first half of this paper is concerned with the generation of confined equilateral random walks. We show that if the selection of a vertex is uniform subject to the position of its previous vertex and the confining condition, then the distributions of the vertices are not uniform, although there exists a distribution such that if the initial vertex is selected following this distribution, then all vertices of the random walk follow this same distribution. Thus in order to generate a confined equilateral random walk, the selection of a vertex cannot be uniform subject to the position of its previous vertex and the confining condition. We provide a simple algorithm capable of generating confined equilateral random walks whose vertex distribution is almost uniform in the confinement sphere. In the second half of this paper we show that any process generating confined equilateral random walks can be turned into a process generating confined equilateral random polygons with the property that the vertex distribution of the polygons approaches the vertex distribution of the walks as the polygons get longer and longer. In our earlier studies, the starting point of the confined polygon is fixed at the center of the sphere. The new approach here allows us to move the starting point of the confined polygon off the center of the sphere. (paper)

Phenomenology and theory of confinement

International Nuclear Information System (INIS)

Pervushin, V.N.

1987-01-01

Phenomenological and theoretical arguments of the separation of the hadronization dynamics from confinement and the idea of the ''kinematic'' confinement are discussed. The recent theory contains results which point out that the Wilson criterion and the confinement potentials are not sufficient for explaining the phenomenological confinement in the sense of zero color amplitudes or Green functions. However, these potentials well explain the hadron spectrum and spontaneous breaking of chiral symmetry, i.e., the hadronization dynamics. The ''kinematic'' confinement can be explained by the topological degeneration of all color-particle physical states in QCD. This degeneration arises if the theory is quantized by explicitly solving the gauge and dynamic constraints: all color states are defined up to gauge(phase) factors describing the map of the three-dimensional space onto SU(3) c -group (π 3 (SU(3) c =Z). The total probability of the color particle generation is equal to zero due to the destructive interference of these phase factors. As a result, in QCD there remains only a hadron sector used in the phenomenology

On confinement and duality

Energy Technology Data Exchange (ETDEWEB)

Strassler, M J [University of Pennsylvania, Philadelphia, PA (United States)

2002-05-15

Confinement in four-dimensional gauge theories is considered from several points of view. General features are discussed, and the mechanism of confinement is investigated. Dualities between field theories, and duality between field theory and string theory, are both put to use. In these lectures I have given an overview of some of the key ideas underlying confinement as a property of field theory, and now, of string theory as well. This is a tiny fraction of what field theory (and now string theory) is capable of, and we are still uncovering new features on a monthly basis. In fact, most field theories do not have confinement, for reasons entirely different from those of QCD. Many become nontrivial conformal field theories at low energy. Others become composite, weakly-coupled gauge theories. Dualities of many stripes are found everywhere. Ordinary dimensional analysis in string theory is totally wrong in the regime where it looks like weakly-coupled field theory, and ordinary dimensional analysis in field theory is totally wrong in the regime where it looks like weakly-coupled supergravity.

ATR confinement leakage determination

International Nuclear Information System (INIS)

Kuan, P.; Buescher, B.J.

1998-01-01

The air leakage rate from the Advanced Test Reactor (ATR) confinement is an important parameter in estimating hypothesized accidental releases of radiation to the environment. The leakage rate must be determined periodically to assure that the confinement has not degraded with time and such determination is one of the technical safety requirements of ATR operation. This paper reviews the methods of confinement leakage determination and presents an analysis of leakage determination under windy conditions, which can complicate the interpretation of the determined leakage rates. The paper also presents results of analyses of building air exchange under windy conditions. High wind can enhance air exchange and this could increase the release rates of radioisotopes following an accident

Generating equilateral random polygons in confinement

International Nuclear Information System (INIS)

Diao, Y; Ernst, C; Montemayor, A; Ziegler, U

2011-01-01

One challenging problem in biology is to understand the mechanism of DNA packing in a confined volume such as a cell. It is known that confined circular DNA is often knotted and hence the topology of the extracted (and relaxed) circular DNA can be used as a probe of the DNA packing mechanism. However, in order to properly estimate the topological properties of the confined circular DNA structures using mathematical models, it is necessary to generate large ensembles of simulated closed chains (i.e. polygons) of equal edge lengths that are confined in a volume such as a sphere of certain fixed radius. Finding efficient algorithms that properly sample the space of such confined equilateral random polygons is a difficult problem. In this paper, we propose a method that generates confined equilateral random polygons based on their probability distribution. This method requires the creation of a large database initially. However, once the database has been created, a confined equilateral random polygon of length n can be generated in linear time in terms of n. The errors introduced by the method can be controlled and reduced by the refinement of the database. Furthermore, our numerical simulations indicate that these errors are unbiased and tend to cancel each other in a long polygon. (paper)

Global confinement characteristics of Jet limiter plasmas

International Nuclear Information System (INIS)

Campbell, D.J.; Christiansen, J.P.; Cordey, J.G.; Thomas, P.R.; Thomsen, K.

1989-01-01

Data from a wide variety of plasma pulses on JET (aux. heating, current, field, minority species, plasma shape, etc) are analysed in order to assess the characteristics of global confinement. The scaling of confinement in ohmically and auxiliary heated discharges is examined. The ohmic confinement in the present new JET configuration (Belt Limiter) is essentially the same as previously. Confinement in auxiliary heated discharges shows presently a slight improvement since 1986. Both ohmic and non-ohmic data is used in a set of confinement time regression analyses and certain constraints derived from theory are imposed

Phase transitions and quark confinement

International Nuclear Information System (INIS)

Polyakov, A.M.; Gava, E.

1978-02-01

The publication collects six lectures on the following themes: quantum field theory and classical statistical mechanics, continuous symmetries, lattice gauge theories, the nature of confinement, a criterion for confinement and non-abelian Yang-Mills theories

Confined Space Evaluation Student Manual, #19613

Energy Technology Data Exchange (ETDEWEB)

Wilmot, David Ezekiel [Los Alamos National Laboratory

2016-08-29

Many workplaces contain spaces that are considered to be “confined” because their configuration hinders the activities of employees who must enter into, work in, and exit from them. In general, the permit-required confined spaces (PRCSs) Occupational Safety and Health Administration (OSHA) standard requires that Los Alamos National Laboratory (LANL) evaluate the workplace to determine if any spaces are PRCSs. The standard specifies strict procedures for the evaluation and atmospheric testing of a space before and during an entry by workers. The OSHA PRCS standard provides for alternative (less stringent than full-permit) entry procedures in cases where the only hazard in a space is atmospheric and the hazard can be controlled by forced air. At LANL, all confined spaces or potential confined spaces on LANL-owned or -operated property must be identified and evaluated by a confined space evaluator accompanied by a knowledgeable person. This course provides the information needed by confined space evaluators to make judgements about whether a space is a confined space, and if so, whether the space will require a permit for entry.

Three-dimensional semi-analytical solution to groundwater flow in confined and unconfined wedge-shaped aquifers

Science.gov (United States)

Sedghi, Mohammad Mahdi; Samani, Nozar; Sleep, Brent

2009-06-01

The Laplace domain solutions have been obtained for three-dimensional groundwater flow to a well in confined and unconfined wedge-shaped aquifers. The solutions take into account partial penetration effects, instantaneous drainage or delayed yield, vertical anisotropy and the water table boundary condition. As a basis, the Laplace domain solutions for drawdown created by a point source in uniform, anisotropic confined and unconfined wedge-shaped aquifers are first derived. Then, by the principle of superposition the point source solutions are extended to the cases of partially and fully penetrating wells. Unlike the previous solution for the confined aquifer that contains improper integrals arising from the Hankel transform [Yeh HD, Chang YC. New analytical solutions for groundwater flow in wedge-shaped aquifers with various topographic boundary conditions. Adv Water Resour 2006;26:471-80], numerical evaluation of our solution is relatively easy using well known numerical Laplace inversion methods. The effects of wedge angle, pumping well location and observation point location on drawdown and the effects of partial penetration, screen location and delay index on the wedge boundary hydraulic gradient in unconfined aquifers have also been investigated. The results are presented in the form of dimensionless drawdown-time and boundary gradient-time type curves. The curves are useful for parameter identification, calculation of stream depletion rates and the assessment of water budgets in river basins.

Don't Fence Me In: Free Meanders in a Confined River Valley

Science.gov (United States)

Eke, E. C.; Wilcock, P. R.

2015-12-01

The interaction between meandering river channels and inerodible valley walls provides a useful test of our ability to understand meander dynamics. In some cases, river meanders confined between valley walls display distinctive angular bends in a dynamic equilibrium such that their size and shape persist as the meander migrates. In other cases, meander geometry is more varied and changes as the meander migrates. The ratio of channel to valley width has been identified as a useful parameter for defining confined meanders, but is not sufficient to distinguish cases in which sharp angular bends are able to migrate with little change in geometry. Here, we examine the effect of water and sediment supply on the geometry of confined rivers in order to identify conditions under which meander geometry reaches a persistent dynamic equilibrium. Because channel width and meander geometry are closely related, we use a numerical meander model that allows for independent migration of both banks, thereby allowing channel width to vary in space and time. We hypothesize that confined meanders with persistent angular bends have smaller transport rates of bed material and that their migration is driven by erosion of the cutbank (bank-pull migration). When bed material supply is sufficiently large that point bar deposition drives meander migration (bar-push migration), confined meander bends have a larger radius of curvature and a geometry that varies as the meander migrates. We test this hypothesis using historical patterns of confined meander migration for rivers with different rates of sediment supply and bed material transport. Interpretation of the meander migration pattern is provided by the free-width meander migration model.

Atom-atom scattering under cylindrical harmonic confinement: Numerical and analytic studies of the confinement induced resonance

International Nuclear Information System (INIS)

Bergeman, T.; Moore, M.G.; Olshanii, M.

2003-01-01

It was recently predicted [Phys. Rev. Lett. 81, 938 (1998)10.1103/PhysRevLett.81.938] that atom-atom scattering under transverse harmonic confinement is subject to a 'confinement-induced resonance' where the effective one-dimensional coupling strength diverges at a particular ratio of the confinement and scattering lengths. As the initial prediction made use of the zero-range pseudopotential approximation, we now report numerical results for finite-range interaction potentials that corroborate this resonance. In addition, we now present a physical interpretation of this effect as a novel type of Feshbach resonance in which the transverse modes of the confining potential assume the roles of 'open' and 'closed' scattering channels

Study of water radiolysis in porous media

International Nuclear Information System (INIS)

Rotureau, Patricia

2001-08-01

The understanding of the production of H 2 in the radiolysis of water confined into pores of concrete is important for the disposal of radioactive waste. In order to describe the mechanisms of water radiolysis in such heterogeneous porous systems we have studied the behaviour under gamma radiation of water confined in porous silica glasses with pores going from 8 to 300 nm of diameter and meso-porous molecular sieves (MCM-41). The radiolytic yields of hydroxyl radicals, hydrated electron and dihydrogen, have been determined with respect to the pore size of materials. The increase of these radiolytic yields compared to those of free water allowed us to show a charge transfer from silica to confined water. On the other hand the kinetics of hydrated electron reactions measured by pulse radiolysis are not modified. (author) [fr

Confinement effects and mechanistic aspects for montmorillonite nanopores.

Science.gov (United States)

Li, Xiong; Zhu, Chang; Jia, Zengqiang; Yang, Gang

2018-08-01

Owing to the ubiquity, critical importance and special properties, confined microenvironments have recently triggered overwhelming interest. In this work, all-atom molecular dynamics simulations have been conducted to address the confinement effects and ion-specific effects for electrolyte solutions within montmorillonite nanopores, where the pore widths vary with a wide range. The adsorption number, structure, dynamics and stability of inner- and outer-sphere metal ions are affected by the change of pore widths (confinement effects), while the extents are significantly dependent on the type of adsorbed species. The type of adsorbed species is, however, not altered by the magnitude of confinement effects, and confinement effects are similar for different electrolyte concentrations. Ion-specific effects are pronounced for all magnitudes of confinement effects (from non- to strong confined conditions), and Hofmeister sequences of outer-sphere species are closely associated with the magnitude of confinement effects while those of inner-sphere species remain consistent. In addition, mechanistic aspects of confinement have been posed using the electrical double layer theories, and the results can be generalized to other confined systems that are ubiquitous in biology, chemistry, geology and nanotechnology. Copyright © 2018 Elsevier Inc. All rights reserved.

Confinement-Dependent Friction in Peptide Bundles

Science.gov (United States)

Erbaş, Aykut; Netz, Roland R.

2013-01-01

Friction within globular proteins or between adhering macromolecules crucially determines the kinetics of protein folding, the formation, and the relaxation of self-assembled molecular systems. One fundamental question is how these friction effects depend on the local environment and in particular on the presence of water. In this model study, we use fully atomistic MD simulations with explicit water to obtain friction forces as a single polyglycine peptide chain is pulled out of a bundle of k adhering parallel polyglycine peptide chains. The whole system is periodically replicated along the peptide axes, so a stationary state at prescribed mean sliding velocity V is achieved. The aggregation number is varied between k = 2 (two peptide chains adhering to each other with plenty of water present at the adhesion sites) and k = 7 (one peptide chain pulled out from a close-packed cylindrical array of six neighboring peptide chains with no water inside the bundle). The friction coefficient per hydrogen bond, extrapolated to the viscous limit of vanishing pulling velocity V → 0, exhibits an increase by five orders of magnitude when going from k = 2 to k = 7. This dramatic confinement-induced friction enhancement we argue to be due to a combination of water depletion and increased hydrogen-bond cooperativity. PMID:23528088

Pattern recognition in probability spaces for visualization and identification of plasma confinement regimes and confinement time scaling

International Nuclear Information System (INIS)

Verdoolaege, G; Karagounis, G; Oost, G Van; Tendler, M

2012-01-01

Pattern recognition is becoming an increasingly important tool for making inferences from the massive amounts of data produced in fusion experiments. The purpose is to contribute to physics studies and plasma control. In this work, we address the visualization of plasma confinement data, the (real-time) identification of confinement regimes and the establishment of a scaling law for the energy confinement time. We take an intrinsically probabilistic approach, modeling data from the International Global H-mode Confinement Database with Gaussian distributions. We show that pattern recognition operations working in the associated probability space are considerably more powerful than their counterparts in a Euclidean data space. This opens up new possibilities for analyzing confinement data and for fusion data processing in general. We hence advocate the essential role played by measurement uncertainty for data interpretation in fusion experiments. (paper)

Ductility of reinforced concrete columns confined with stapled strips

International Nuclear Information System (INIS)

Tahir, M.F.; Khan, Q.U.Z.; Shabbir, F.; Sharif, M.B.; Ijaz, N.

2015-01-01

Response of three 150x150x450mm short reinforced concrete (RC) columns confined with different types of confining steel was investigated. Standard stirrups, strips and stapled strips, each having same cross-sectional area, were employed as confining steel around four comer column bars. Experimental work was aimed at probing into the affect of stapled strip confinement on post elastic behavior and ductility level under cyclic axial load. Ductility ratios, strength enhancement factor and core concrete strengths were compared to study the affect of confinement. Results indicate that strength enhancement in RC columns due to strip and stapled strip confinement was not remarkable as compared to stirrup confined column. It was found that as compared to stirrup confined column, stapled strip confinement enhanced the ductility of RC column by 183% and observed axial capacity of stapled strip confined columns was 41 % higher than the strip confined columns. (author)

Global energy confinement in TORE SUPRA

International Nuclear Information System (INIS)

Hoang, G.T.; Bizarro, J.P.; Genile, B. de; Hutter, Th.; Laurent, L.; Litaudon, X.; Moreau, D.; Peysson, Y.; Tonon, G.; Houtte, D. van

1992-01-01

The global energy confinement behaviour of mixed Ohmic/Lower Hybrid driven Tore Supra plasmas has been analysed at various densities. In contradiction with L-mode ITER scaling law, this analysis indicates that the global energy confinement time depends strongly on the plasma density and the isotopic dependence seems not to be observed. The thermal electron energy content of steady-state discharges is in good agreement with the offset linear Rebut-Lallia scaling law. During current ramp experiments, the global energy confinement time was found to depend on the internal self-inductance (li). Improved confinement has been obtained for a steady-state 0.8 MA plasma where the plasma current profile is peaked by LH waves (li ∼1.8). In this case, the global confinement time is found to be about 40% higher than the value predicted by the Rebut-Lallia scaling law. (author) 3 refs., 6 figs

An introduction to the confinement problem

International Nuclear Information System (INIS)

Greensite, Jeff

2011-01-01

This book addresses the confinement problem, which quite generally deals with the behavior of non-abelian gauge theories, and the force which is mediated by gauge fields, at large distances.The word ''confinement'' in the context of hadronic physics originally referred to the fact that quarks and gluons appear to be trapped inside mesons and baryons, from which they cannot escape. There are other, and possibly deeper meanings that can be attached to the term, and these will be explored in this book. Although the confinement problem is far from solved, much is now known about the general features of the confining force, and there are a number of very well motivated theories of confinement which are under active investigation. This volume gives a both pedagogical and concise introduction and overview of the main ideas in this field, their attractive features, and, as appropriate, their shortcomings. (orig.)

Enhanced gas absorption in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf2N]) confined in silica slit pores: a molecular simulation study.

Science.gov (United States)

Shi, Wei; Luebke, David R

2013-05-07

Two-dimensional NPxyT and isostress-osmotic (N2PxyTf1) Monte Carlo simulations were used to compute the density and gas absorption properties of the ionic liquid (IL) 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf2N]) confined in silica slit pores (25-45 Å). Self-diffusivity values for both gas and IL were calculated from NVE molecular dynamics simulations using both smooth and atomistic potential models for silica. The simulations showed that the molar volume of [hmim][Tf2N] confined in 25-45-Å silica slit pores is 12-31% larger than that of the bulk IL at 313-573 K and 1 bar. The amounts of CO2, H2, and N2 absorbed in the confined IL are 1.1-3 times larger than those in the bulk IL because of the larger molar volume of the confined IL compared to the bulk IL. The CO2, N2, and H2 molecules are generally absorbed close to the silica wall where the IL density is very low. This arrangement causes the self-diffusivities of these gases in the confined IL to be 2-8 times larger than those in the bulk IL at 298-573 K. The solubilities of water in the confined and bulk ILs are similar, which is likely due to strong water interactions with [hmim][Tf2N] through hydrogen bonding, so that the molar volume of the confined IL plays a less important role in determining the H2O solubility. Water molecules are largely absorbed in the IL-rich region rather than close to the silica wall. The self-diffusivities of water correlate with those of the confined IL. The confined IL exhibits self-diffusivities larger than those of the bulk IL at lower temperatures, but smaller than those of the bulk IL at higher temperatures. The findings from our simulations are consistent with available experimental data for similar confined IL systems.

Confinement dynamics in the reversed field pinch

International Nuclear Information System (INIS)

Schoenberg, K.F.

1988-01-01

The study of basic transport and confinement dynamics is central to the development of the reversed field pinch (RFP) as a confinement concept. Thus, the goal of RFP research is to understand the connection between processes that sustain the RFP configuration and related transport/confinement properties. Recently, new insights into confinement have emerged from a detailed investigation of RFP electron and ion physics. These insights derive from the recognition that both magnetohydrodynamic (MHD) and electron kinetic effects play an important and strongly coupled role in RFP sustainment and confinement dynamics. In this paper, we summarize the results of these studies on the ZT-40M experiment. 8 refs

From Pauli's birthday to 'Confinement Resonances' – a potted history of Quantum Confinement

International Nuclear Information System (INIS)

Connerade, J P

2013-01-01

Quantum Confinement is in some sense a new subject. International meetings dedicated to Quantum Confinement have occurred only recently in Mexico City (the first in 2010 and the second, in September 2011). However, at least in principle, the subject has existed since a very long time. Surprisingly perhaps, it lay dormant for many years, for want of suitable experimental examples. However, when one looks carefully at its origin, it turns out to have a long and distinguished history. In fact, the problem of quantum confinement raises a number of very interesting issues concerning boundary conditions in elementary quantum mechanics and how they should be applied to real problems. Some of these issues were missed in the earliest papers, but are implicit in the structure of quantum mechanics, and lead to the notion of Confinement Resonances, the existence of which was predicted theoretically more than ten years ago. Although, for several reasons, these resonances remained elusive for a very long time, they have now been observed experimentally, which puts the whole subject in much better shape and, together with the advent of metallofullerenes, has contributed to its revival.

Momentum confinement at low torque

Energy Technology Data Exchange (ETDEWEB)

Solomon, W M [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Burrell, K H [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); De Grassie, J S [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Budny, R [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Groebner, R J [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Kinsey, J E [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Kramer, G J [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Luce, T C [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Makowski, M A [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Mikkelsen, D [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Nazikian, R [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Petty, C C [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Politzer, P A [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Scott, S D [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Zeeland, M A Van [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Zarnstorff, M C [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States)

2007-12-15

Momentum confinement was investigated on DIII-D as a function of applied neutral beam torque at constant normalized beta {beta}{sub N}, by varying the mix of co (parallel to the plasma current) and counter neutral beams. Under balanced neutral beam injection (i.e. zero total torque to the plasma), the plasma maintains a significant rotation in the co-direction. This 'intrinsic' rotation can be modeled as being due to an offset in the applied torque (i.e. an 'anomalous torque'). This anomalous torque appears to have a magnitude comparable to one co neutral beam source. The presence of such an anomalous torque source must be taken into account to obtain meaningful quantities describing momentum transport, such as the global momentum confinement time and local diffusivities. Studies of the mechanical angular momentum in ELMing H-mode plasmas with elevated q{sub min} show that the momentum confinement time improves as the torque is reduced. In hybrid plasmas, the opposite effect is observed, namely that momentum confinement improves at high torque/rotation. GLF23 modeling suggests that the role of E x B shearing is quite different between the two plasmas, which may help to explain the different dependence of the momentum confinement on torque.

Confinement-induced resonances in anharmonic waveguides

Energy Technology Data Exchange (ETDEWEB)

Peng Shiguo [Department of Physics, Tsinghua University, Beijing 100084 (China); Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia); Hu Hui; Liu Xiaji; Drummond, Peter D. [Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia)

2011-10-15

We develop the theory of anharmonic confinement-induced resonances (ACIRs). These are caused by anharmonic excitation of the transverse motion of the center of mass (c.m.) of two bound atoms in a waveguide. As the transverse confinement becomes anisotropic, we find that the c.m. resonant solutions split for a quasi-one-dimensional (1D) system, in agreement with recent experiments. This is not found in harmonic confinement theories. A new resonance appears for repulsive couplings (a{sub 3D}>0) for a quasi-two-dimensional (2D) system, which is also not seen with harmonic confinement. After inclusion of anharmonic energy corrections within perturbation theory, we find that these ACIRs agree extremely well with anomalous 1D and 2D confinement-induced resonance positions observed in recent experiments. Multiple even- and odd-order transverse ACIRs are identified in experimental data, including up to N=4 transverse c.m. quantum numbers.

Identification of palaeo-seawater intrusion in groundwater using minor ions in a semi-confined aquifer of the Río de la Plata littoral (Argentina)

Energy Technology Data Exchange (ETDEWEB)

Santucci, L., E-mail: eleocarol@fcnym.unlp.edu.ar [Centro de Investigaciones Geológicas (CIG), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Universidad Nacional de La Plata - UNLP, Calle 64 y Diag. 113, 1900 La Plata, Buenos Aires (Argentina); Carol, E. [Centro de Investigaciones Geológicas (CIG), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Universidad Nacional de La Plata - UNLP, Calle 64 y Diag. 113, 1900 La Plata, Buenos Aires (Argentina); Kruse, E. [Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Cátedra de Hidrología General de la Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata (UNLP), Calle 64 #3, 1900 La Plata, Buenos Aires (Argentina)

2016-10-01

The hydrochemistry of minor elements and traces such as bromide, lithium, strontium, uranium and selenium, together with the chemical analysis of major ions, has been used in the study of salinization process. This process occurs in a semi-confined aquifer that corresponds to a Pliocene–Pleistocene fluvial environment. The semi-confined aquifer is located in the littoral of the cities of Ensenada and Berisso, in the region of the middle Río de la Plata estuary, Argentina. Groundwater salinization was detected in the semi-confined aquifer in the coastal plain area, with salt contents that increase from the loess plain towards the river. The content of major ions that predominate in sea water (Cl{sup −}, Na{sup +} and Mg{sup 2+}), as well as the Cl{sup −}/Br{sup −} and U vs. Cl{sup −} ratios, demonstrates that such salinization is related to sea water, which shows no correspondence with estuary water. In the salinized area, Li, Sr and Se enrichments occur, and are used as tracers of the average time that a substance remains in solution in sea water in the aquifer. The study of such minor ions together with the geological evolution of the area made it possible to recognize that the salt water in the semi-confined aquifer corresponds to a palaeo-intrusion of sea water associated with the Pleistocene–Holocene ingressions caused by the climate changes occurring during the Quaternary. - Highlights: • The semi-confined aquifer in a sector of the Río de la Plata estuary is salinized. • Saline content is higher in the aquifer than in the estuary. • Minor elements indicate the occurrence of palaeo-seawater intrusion. • Palaeo-seawater intrusion may be associated with interglacial fluctuations.

Identification of palaeo-seawater intrusion in groundwater using minor ions in a semi-confined aquifer of the Río de la Plata littoral (Argentina)

International Nuclear Information System (INIS)

Santucci, L.; Carol, E.; Kruse, E.

2016-01-01

The hydrochemistry of minor elements and traces such as bromide, lithium, strontium, uranium and selenium, together with the chemical analysis of major ions, has been used in the study of salinization process. This process occurs in a semi-confined aquifer that corresponds to a Pliocene–Pleistocene fluvial environment. The semi-confined aquifer is located in the littoral of the cities of Ensenada and Berisso, in the region of the middle Río de la Plata estuary, Argentina. Groundwater salinization was detected in the semi-confined aquifer in the coastal plain area, with salt contents that increase from the loess plain towards the river. The content of major ions that predominate in sea water (Cl"−, Na"+ and Mg"2"+), as well as the Cl"−/Br"− and U vs. Cl"− ratios, demonstrates that such salinization is related to sea water, which shows no correspondence with estuary water. In the salinized area, Li, Sr and Se enrichments occur, and are used as tracers of the average time that a substance remains in solution in sea water in the aquifer. The study of such minor ions together with the geological evolution of the area made it possible to recognize that the salt water in the semi-confined aquifer corresponds to a palaeo-intrusion of sea water associated with the Pleistocene–Holocene ingressions caused by the climate changes occurring during the Quaternary. - Highlights: • The semi-confined aquifer in a sector of the Río de la Plata estuary is salinized. • Saline content is higher in the aquifer than in the estuary. • Minor elements indicate the occurrence of palaeo-seawater intrusion. • Palaeo-seawater intrusion may be associated with interglacial fluctuations.

The Physics Basis of ITER Confinement

International Nuclear Information System (INIS)

Wagner, F.

2009-01-01

ITER will be the first fusion reactor and the 50 year old dream of fusion scientists will become reality. The quality of magnetic confinement will decide about the success of ITER, directly in the form of the confinement time and indirectly because it decides about the plasma parameters and the fluxes, which cross the separatrix and have to be handled externally by technical means. This lecture portrays some of the basic principles which govern plasma confinement, uses dimensionless scaling to set the limits for the predictions for ITER, an approach which also shows the limitations of the predictions, and describes briefly the major characteristics and physics behind the H-mode--the preferred confinement regime of ITER.

On the implications of confinement

International Nuclear Information System (INIS)

Roberts, C.D.

1992-01-01

In this paper, the authors consider some implications of confinement starting from the basic observation that cross-sections for the production of colored asymptotic states, such as free quarks and gluons, from color singlet initial states must be zero if QCD is to be confining. The authors discuss two pictures of confinement: the failure of the cluster decomposition property and the absence of a pole at timelike momenta in the propagator of a confined particle. The authors use QCD-based models as a framework to relate the failure of the cluster decomposition property to other ideas, such as the role of a nonzero gluon condensate. The authors' primary interest is to address the question of the absence of a mass pole through a study of model Schwinger-Dyson equations. These equations contain some of the dynamical information that is present in the study of the cluster decomposition property. The authors discuss the problems within this idea and its study using the Schwinger-Dyson equations

Supramolecular 1-D polymerization of DNA origami through a dynamic process at the 2-dimensionally confined air-water interface.

Science.gov (United States)

Yonamine, Yusuke; Cervantes-Salguero, Keitel; Minami, Kosuke; Kawamata, Ibuki; Nakanishi, Waka; Hill, Jonathan P; Murata, Satoshi; Ariga, Katsuhiko

2016-05-14

In this study, a Langmuir-Blodgett (LB) system has been utilized for the regulation of polymerization of a DNA origami structure at the air-water interface as a two-dimensionally confined medium, which enables dynamic condensation of DNA origami units through variation of the film area at the macroscopic level (ca. 10-100 cm(2)). DNA origami sheets were conjugated with a cationic lipid (dioctadecyldimethylammonium bromide, 2C18N(+)) by electrostatic interaction and the corresponding LB-film was prepared. By applying dynamic pressure variation through compression-expansion processes, the lipid-modified DNA origami sheets underwent anisotropic polymerization forming a one-dimensionally assembled belt-shaped structure of a high aspect ratio although the thickness of the polymerized DNA origami was maintained at the unimolecular level. This approach opens up a new field of mechanical induction of the self-assembly of DNA origami structures.

Mechanical collapse of confined fluid membrane vesicles.

Science.gov (United States)

Rim, Jee E; Purohit, Prashant K; Klug, William S

2014-11-01

Compact cylindrical and spherical invaginations are common structural motifs found in cellular and developmental biology. To understand the basic physical mechanisms that produce and maintain such structures, we present here a simple model of vesicles in confinement, in which mechanical equilibrium configurations are computed by energy minimization, balancing the effects of curvature elasticity, contact of the membrane with itself and the confining geometry, and adhesion. For cylindrical confinement, the shape equations are solved both analytically and numerically by finite element analysis. For spherical confinement, axisymmetric configurations are obtained numerically. We find that the geometry of invaginations is controlled by a dimensionless ratio of the adhesion strength to the bending energy of an equal area spherical vesicle. Larger adhesion produces more concentrated curvatures, which are mainly localized to the "neck" region where the invagination breaks away from its confining container. Under spherical confinement, axisymmetric invaginations are approximately spherical. For extreme confinement, multiple invaginations may form, bifurcating along multiple equilibrium branches. The results of the model are useful for understanding the physical mechanisms controlling the structure of lipid membranes of cells and their organelles, and developing tissue membranes.

Ice nucleation rates near ˜225 K

Science.gov (United States)

Amaya, Andrew J.; Wyslouzil, Barbara E.

2018-02-01

We have measured the ice nucleation rates, Jice, in supercooled nano-droplets with radii ranging from 6.6 nm to 10 nm and droplet temperatures, Td, ranging from 225 K to 204 K. The initial temperature of the 10 nm water droplets is ˜250 K, i.e., well above the homogeneous nucleation temperature for micron sized water droplets, TH ˜235 K. The nucleation rates increase systematically from ˜1021 cm-3 s-1 to ˜1022 cm-3 s-1 in this temperature range, overlap with the nucleation rates of Manka et al. [Phys. Chem. Chem. Phys. 14, 4505 (2012)], and suggest that experiments with larger droplets would extrapolate smoothly the rates of Hagen et al. [J. Atmos. Sci. 38, 1236 (1981)]. The sharp corner in the rate data as temperature drops is, however, difficult to match with available theory even if we correct classical nucleation theory and the physical properties of water for the high internal pressure of the nanodroplets.

Applications of a general random-walk theory for confined diffusion.

Science.gov (United States)

Calvo-Muñoz, Elisa M; Selvan, Myvizhi Esai; Xiong, Ruichang; Ojha, Madhusudan; Keffer, David J; Nicholson, Donald M; Egami, Takeshi

2011-01-01

A general random walk theory for diffusion in the presence of nanoscale confinement is developed and applied. The random-walk theory contains two parameters describing confinement: a cage size and a cage-to-cage hopping probability. The theory captures the correct nonlinear dependence of the mean square displacement (MSD) on observation time for intermediate times. Because of its simplicity, the theory also requires modest computational requirements and is thus able to simulate systems with very low diffusivities for sufficiently long time to reach the infinite-time-limit regime where the Einstein relation can be used to extract the self-diffusivity. The theory is applied to three practical cases in which the degree of order in confinement varies. The three systems include diffusion of (i) polyatomic molecules in metal organic frameworks, (ii) water in proton exchange membranes, and (iii) liquid and glassy iron. For all three cases, the comparison between theory and the results of molecular dynamics (MD) simulations indicates that the theory can describe the observed diffusion behavior with a small fraction of the computational expense. The confined-random-walk theory fit to the MSDs of very short MD simulations is capable of accurately reproducing the MSDs of much longer MD simulations. Furthermore, the values of the parameter for cage size correspond to the physical dimensions of the systems and the cage-to-cage hopping probability corresponds to the activation barrier for diffusion, indicating that the two parameters in the theory are not simply fitted values but correspond to real properties of the physical system.

Confinement and the Pomeron

International Nuclear Information System (INIS)

White, A.R.

1989-01-01

The importance of confinement for obtaining a unitary high-energy limit for QCD is discussed. ''Minijets'' are argued to build up non-unitary behavior endash when k T > Λ is imposed. For minijets to mix with low k T Pomeron Field Theory describing confinement, and give consistent asymptotic behavior, new ''quarks'' must enter the theory above the minijet transverse momentum scale. The Critical Pomeron is the resulting high-energy limit. 22 refs

FRP confined smart concrete/mortar

Science.gov (United States)

Xiao, Y.; Zhu, P. S.; Choi, K. G.; Wu, Y. T.; Huang, Z. Y.; Shan, B.

2006-03-01

In this study, fiber reinforced polymer (FRP) confined smart concrete/mortar sensors were invented and validated for significantly improved measurement range. Several trial mixes were made using cement mortar and micron-phase graphite powders at different mix proportions. Compressive loading tests were conducted on smart mortar cylinder specimens with or without FRP confinement. Two-probe method was used to detect the electrical resistance of the smart cement mortar specimens. Strong correlation was recognized between the stress and electric resistance of the smart mortar. The test results indicated that the FRP wrapping could significantly enlarge the range of such self-sensing property as a consequence of confinement.

Novel Technique for Quantitative Fast Scanning Calorimetry on Electrospun Fibers

Science.gov (United States)

Thomas, David; Govinna, Nelaka; Schick, Christoph; Cebe, Peggy

Fast scanning chip calorimetry allows for the study of polymers which have rapid nucleation and/or crystallization kinetics, or degrade within their melting range. Heating rates used, up to 4000 K/s, allow studies of hetero and homogeneous nucleation at time scales inaccessible with conventional calorimeters, whose rates are typically alcohol (PVA) were chosen in the development of a new methodology to obtain quantitative fast scanning thermal data from electrospun nanofibers using a Flash DSC1. The structure of nanofibers requires special methods to load nanogram-sized samples onto a UFSC1 sensor. Fibers were directly spun onto TEM grids which provide a durable substrate to support bundles of nanofibers and possess excellent thermal conductivity allowing for a strong, repeatable signal and ensure good sample to sensor contact. As spun samples were held isothermally at temperatures ranging from Tg to Tm then heated at 2,000 K/s to assess as-spun crystallinity and cold crystallization behaviors. Above Tm the fibers break up into micro- and nano-droplets. On these samples, melt crystallization experiments were performed to study nucleation and crystallization of polymer confined to nanodroplet morphology. NSF DMR-1608125.

Acceleration{endash}deceleration process of thin foils confined in water and submitted to laser driven shocks

Energy Technology Data Exchange (ETDEWEB)

Romain, J.P.; Auroux, E. [Laboratoire de Combustion et de Detonique (UPR 9028 CNRS), ENSMA, BP 109, Teleport 2, Chasseneuil du Poitou, 86960 Futuroscope Cedex (France)

1997-08-01

An experimental, numerical, and analytical study of the acceleration and deceleration process of thin metallic foils immersed in water and submitted to laser driven shocks is presented. Aluminum and copper foils of 20 to 120 {mu}m thickness, confined on both sides by water, have been irradiated at 1.06 {mu}m wavelength by laser pulses of {approximately}20ns duration, {approximately}17J energy, and {approximately}4GW/cm{sup 2} incident intensity. Time resolved velocity measurements have been made, using an electromagnetic velocity gauge. The recorded velocity profiles reveal an acceleration{endash}deceleration process, with a peak velocity up to 650 m/s. Predicted profiles from numerical simulations reproduce all experimental features, such as wave reverberations, rate of increase and decrease of velocity, peak velocity, effects of nature, and thickness of the foils. A shock pressure of about 2.5 GPa is inferred from the velocity measurements. Experimental points on the evolution of plasma pressure are derived from the measurements of peak velocities. An analytical description of the acceleration{endash}deceleration process, involving multiple shock and release waves reflecting on both sides of the foils, is presented. The space{endash}time diagrams of waves propagation and the successive pressure{endash}particle velocity states are determined, from which theoretical velocity profiles are constructed. All characteristics of experimental records and numerical simulations are well reproduced. The role of foil nature and thickness, in relation with the shock impedance of the materials, appears explicitly. {copyright} {ital 1997 American Institute of Physics.}

Confinement of quarks

International Nuclear Information System (INIS)

Nambu, J.

1978-01-01

Three quark models of hadron structure, which suggest an explanation of quarks confinement mechanism in hadrons are considered. Quark classifications, quark flawors and colours, symmetry model of hadron structure based on the colour theory of strong interaction are discussed. Diagrams of colour combinations of quarks and antiquarks, exchange of gluons, binding quarks in hadron. Quark confinement models based on the field theory, string model rotating and bag model are discussed. Diagrams of the colour charge distribution explaining the phenomena of infrared ''slavery'' and ultraviolet ''freedom'' are given. The models considered explain but some quark properties, creating prerequisites for the development of the consequent theory of hadron structure

Universality classes and critical phenomena in confined liquid systems

Directory of Open Access Journals (Sweden)

A.V. Chalyi

2013-06-01

Full Text Available It is well known that the similar universal behavior of infinite-size (bulk systems of different nature requires the same basic conditions: space dimensionality; number components of order parameter; the type (short- or long-range of the intermolecular interaction; symmetry of the fluctuation part of thermodynamical potential. Basic conditions of similar universal behavior of confined systems needs the same supplementary conditions such as the number of monolayers for a system confinement; low crossover dimensionality, i.e., geometric form of restricted volume; boundary conditions on limiting surfaces; physical properties under consideration. This review paper is aimed at studying all these conditions of similar universal behavior for diffusion processes in confined liquid systems. Special attention was paid to the effects of spatial dispersion and low crossover dimensionality. This allowed us to receive receiving correct nonzero expressions for the diffusion coefficient at the critical point and to take into account the specific geometric form of the confined liquid volume. The problem of 3D⇔2D dimensional crossover was analyzed. To receive a smooth crossover for critical exponents, the Kawasaki-like approach from the theory of mode coupling in critical dynamics was proposed. This ensured a good agreement between data of computer experiment and theoretical calculations of the size dependence of the critical temperature Tc(H of water in slitlike pores. The width of the quasi-elastic scattering peak of slow neutrons near the structural phase transition in the aquatic suspensions of plasmatic membranes (mesostructures with the typical thickness up to 10 nm was studied. It was shown that the width of quasi-elastic peak of neutron scattering decreases due to the process of cell proliferation, i.e., with an increase of the membrane size (including the membrane thickness. Thus, neutron studies could serve as an additional diagnostic test for the

Combined confinement system applied to tokamaks

International Nuclear Information System (INIS)

Ohkawa, Tihiro

1986-01-01

From particle orbit point of view, a tokamak is a combined confinement configuration where a closed toroidal volume is surrounded by an open confinement system like a magnetic mirror. By eliminating a cold halo plasma, the energy loss from the plasma becomes convective. The H-mode in diverted tokamaks is an example. Because of the favorable scaling of the energy confinement time with temperature, the performance of the tokamak may be significantly improved by taking advantage of this effect. (author)

Instability of confined water films between elastic surfaces

NARCIS (Netherlands)

de Beer, Sissi; 't Mannetje, Dieter; Zantema, Sietske; Mugele, Friedrich

2010-01-01

We investigated the dynamics of nanometer thin water films at controlled ambient humidity adsorbed onto two atomically smooth mica sheets upon rapidly bringing the surfaces into contact. Using a surface forces apparatus (SFA) in imaging mode, we found that the water films break up into a

Water self-diffusion through narrow oxygenated carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Striolo, Alberto [School of Chemical Biological and Materials Engineering, University of Oklahoma, Norman, OK 73019 (United States)

2007-11-28

The hydrophobic interior of carbon nanotubes, which is reminiscent of ion channels in cellular membranes, has inspired scientific research directed towards the production of, for example, membranes for water desalination, drug-delivery devices, and nanosyringes. To develop these technologies it is crucial to understand and predict the equilibrium and transport properties of confined water. We present here a series of molecular dynamics simulation results conducted to understand the extent to which the presence of a few oxygenated active sites, modeled as carbonyls, affects the transport properties of confined water. The model for the carbon nanotube is not intended to be realistic. Its only purpose is to allow us to understand the effect of a few oxygenated sites on the transport properties of water confined in a narrow cylindrical pore, which is otherwise hydrophobic. At low hydration levels we found little, if any, water diffusion. The diffusion, which appears to be of the Fickian type for sufficiently large hydration levels, becomes faster as the number of confined water molecules increases, reaches a maximum, and slows as water fills the carbon nanotubes. We explain our findings on the basis of two collective motion mechanisms observed from the analysis of sequences of simulation snapshots. We term the two mechanisms 'cluster-breakage' and 'cluster-libration' mechanisms. We observe that the cluster-breakage mechanism produces longer displacements for the confined water molecules than the cluster-libration one, but deactivates as water fills the carbon nanotube. From a practical point of view, our results are particularly important for two reasons: (1) at low hydration levels the presence of only eight carbonyl groups can prevent the diffusion of water through (8, 8) carbon nanotubes; and (2) the extremely fast self-diffusion coefficients observed for water within narrow carbon nanotubes are significantly decreased in the presence of only a

Water self-diffusion through narrow oxygenated carbon nanotubes

International Nuclear Information System (INIS)

Striolo, Alberto

2007-01-01

The hydrophobic interior of carbon nanotubes, which is reminiscent of ion channels in cellular membranes, has inspired scientific research directed towards the production of, for example, membranes for water desalination, drug-delivery devices, and nanosyringes. To develop these technologies it is crucial to understand and predict the equilibrium and transport properties of confined water. We present here a series of molecular dynamics simulation results conducted to understand the extent to which the presence of a few oxygenated active sites, modeled as carbonyls, affects the transport properties of confined water. The model for the carbon nanotube is not intended to be realistic. Its only purpose is to allow us to understand the effect of a few oxygenated sites on the transport properties of water confined in a narrow cylindrical pore, which is otherwise hydrophobic. At low hydration levels we found little, if any, water diffusion. The diffusion, which appears to be of the Fickian type for sufficiently large hydration levels, becomes faster as the number of confined water molecules increases, reaches a maximum, and slows as water fills the carbon nanotubes. We explain our findings on the basis of two collective motion mechanisms observed from the analysis of sequences of simulation snapshots. We term the two mechanisms 'cluster-breakage' and 'cluster-libration' mechanisms. We observe that the cluster-breakage mechanism produces longer displacements for the confined water molecules than the cluster-libration one, but deactivates as water fills the carbon nanotube. From a practical point of view, our results are particularly important for two reasons: (1) at low hydration levels the presence of only eight carbonyl groups can prevent the diffusion of water through (8, 8) carbon nanotubes; and (2) the extremely fast self-diffusion coefficients observed for water within narrow carbon nanotubes are significantly decreased in the presence of only a few oxygenated active

Dimensional crossover in fluids under nanometer-scale confinement.

Science.gov (United States)

Das, Amit; Chakrabarti, J

2012-05-01

Several earlier studies have shown signatures of crossover in various static and dynamics properties of a confined fluid when the confining dimension decreases to about a nanometer. The density fluctuations govern the majority of such properties of a fluid. Here, we illustrate the crossover in density fluctuation in a confined fluid, to provide a generic understanding of confinement-induced crossover of fluid properties, using computer simulations. The crossover can be understood as a manifestation of changes in the long-wavelength behavior of fluctuation in density due to geometrical constraints. We further show that the confining potential significantly affects the crossover behavior.

Ice crystallization in ultrafine water-salt aerosols: nucleation, ice-solution equilibrium, and internal structure.

Science.gov (United States)

Hudait, Arpa; Molinero, Valeria

2014-06-04

Atmospheric aerosols have a strong influence on Earth's climate. Elucidating the physical state and internal structure of atmospheric aqueous aerosols is essential to predict their gas and water uptake, and the locus and rate of atmospherically important heterogeneous reactions. Ultrafine aerosols with sizes between 3 and 15 nm have been detected in large numbers in the troposphere and tropopause. Nanoscopic aerosols arising from bubble bursting of natural and artificial seawater have been identified in laboratory and field experiments. The internal structure and phase state of these aerosols, however, cannot yet be determined in experiments. Here we use molecular simulations to investigate the phase behavior and internal structure of liquid, vitrified, and crystallized water-salt ultrafine aerosols with radii from 2.5 to 9.5 nm and with up to 10% moles of ions. We find that both ice crystallization and vitrification of the nanodroplets lead to demixing of pure water from the solutions. Vitrification of aqueous nanodroplets yields nanodomains of pure low-density amorphous ice in coexistence with vitrified solute rich aqueous glass. The melting temperature of ice in the aerosols decreases monotonically with an increase of solute fraction and decrease of radius. The simulations reveal that nucleation of ice occurs homogeneously at the subsurface of the water-salt nanoparticles. Subsequent ice growth yields phase-segregated, internally mixed, aerosols with two phases in equilibrium: a concentrated water-salt amorphous mixture and a spherical cap-like ice nanophase. The surface of the crystallized aerosols is heterogeneous, with ice and solution exposed to the vapor. Free energy calculations indicate that as the concentration of salt in the particles, the advance of the crystallization, or the size of the particles increase, the stability of the spherical cap structure increases with respect to the alternative structure in which a core of ice is fully surrounded by

Insignificant influence of the matrix on the melting of ice confined in decorated mesoporous silica

Science.gov (United States)

Xu, Yunbo; Zhao, Zhenyan; Wang, Lianwen

2018-01-01

For a critical examination of matrix effect on the melting of confined ice, mesoporous silica (SBA-15) are synthesised and decorated with n-Alkyl and aminopropyl groups to tune the surface hydrophobicity. Water contact angle to these decorated surfaces are estimated to be about 100° and 60°, respectively. By examining the melting of ice confined in these decorated samples, we find that the influence of the matrix is indeed not significant. The reported apparent matrix effect is more likely method effect in the determination of pore diameters as was demonstrated in our previous studies (Philos. Mag. 93 (2013), p. 1827).

Plasma confinement in a magnetic dipole

International Nuclear Information System (INIS)

Kesner, J.; Bromberg, L.; Garnier, D.; Mauel, M.

1999-01-01

A dipole fusion confinement device is stable to MHD interchange and ballooning modes when the pressure profile is sufficiently gentle. The plasma can be confined at high beta, is steady state and disruption free. Theory indicates that when the pressure gradient is sufficiently gentle to satisfy MHD requirements drift waves will also be stable. The dipole approach is particularly applicable for advanced fuels. A new experimental facility is presently being built to test the stability and transport properties of a dipole-confined plasma. (author)

Plasma confinement in a magnetic dipole

International Nuclear Information System (INIS)

Kesner, J.; Bromberg, L.; Garnier, D.; Mauel, M.

2001-01-01

A dipole fusion confinement device is stable to MHD interchange and ballooning modes when the pressure profile is sufficiently gentle. The plasma can be confined at high beta, is steady state and disruption free. Theory indicates that when the pressure gradient is sufficiently gentle to satisfy MHD requirements drift waves will also be stable. The dipole approach is particularly applicable for advanced fuels. A new experimental facility is presently being built to test the stability and transport properties of a dipole-confined plasma. (author)

Bifurcated equilibria in centrifugally confined plasma

International Nuclear Information System (INIS)

Shamim, I.; Teodorescu, C.; Guzdar, P. N.; Hassam, A. B.; Clary, R.; Ellis, R.; Lunsford, R.

2008-01-01

A bifurcation theory and associated computational model are developed to account for abrupt transitions observed recently on the Maryland Centrifugal eXperiment (MCX) [R. F. Ellis et al. Phys. Plasmas 8, 2057 (2001)], a supersonically rotating magnetized plasma that relies on centrifugal forces to prevent thermal expansion of plasma along the magnetic field. The observed transitions are from a well-confined, high-rotation state (HR-mode) to a lower-rotation, lesser-confined state (O-mode). A two-dimensional time-dependent magnetohydrodynamics code is used to simulate the dynamical equilibrium states of the MCX configuration. In addition to the expected viscous drag on the core plasma rotation, a momentum loss term is added that models the friction of plasma on the enhanced level of neutrals expected in the vicinity of the insulators at the throats of the magnetic mirror geometry. At small values of the external rotation drive, the plasma is not well-centrifugally confined and hence experiences the drag from near the insulators. Beyond a critical value of the external drive, the system makes an abrupt transition to a well-centrifugally confined state in which the plasma has pulled away from the end insulator plates; more effective centrifugal confinement lowers the plasma mass near the insulators allowing runaway increases in the rotation speed. The well-confined steady state is reached when the external drive is balanced by only the viscosity of the core plasma. A clear hysteresis phenomenon is shown.

Study of the radiolysis of water in porous media

International Nuclear Information System (INIS)

Rotureau, P.

2004-01-01

The understanding of the production of H 2 in the radiolysis of water confined into pores of concrete is important for the disposal of radioactive waste. In order to describe the mechanisms of water radiolysis in such heterogeneous porous systems we have studied the behaviour under gamma radiation of water confined in porous silica glasses with pores going from 8 to 300 nm of diameter and meso-porous molecular sieves (MCM-41). The radiolytic yields of hydroxyl radicals, hydrated electron and dihydrogen, have been determined with respect to the pore size of materials. The increase of these radiolytic yields compared to those of free water allowed us to show a charge transfer from silica to confined water. On the other hand the kinetics of hydrated electron reactions measured by pulse radiolysis are not modified. (author) [fr

A Study of Confined Helium Atom

International Nuclear Information System (INIS)

Xie Wenfang

2007-01-01

The helium atom confined by a spherical parabolic potential well is studied employing the adiabatic hyperspherical approach method. Total energies of the ground and three low-excited states are obtained as a function of the confined potential radii. We find that the energies of a spherical parabolic potential well are in good agreement with those of an impenetrable spherical box for the larger confined potential radius. We find also that the confinement may cause accidental degeneracies between levels with different low-excited states and the inversion of the energy values. The results for the three-dimensional spherical potential well and the two-dimensional disc-like potential well are compared with each other. We find that the energy difference between states in a two-dimensional parabolic potential is also obviously larger than the corresponding levels for a spherical parabolic potential.

Topology of polymer chains under nanoscale confinement.

Science.gov (United States)

Satarifard, Vahid; Heidari, Maziar; Mashaghi, Samaneh; Tans, Sander J; Ejtehadi, Mohammad Reza; Mashaghi, Alireza

2017-08-24

Spatial confinement limits the conformational space accessible to biomolecules but the implications for bimolecular topology are not yet known. Folded linear biopolymers can be seen as molecular circuits formed by intramolecular contacts. The pairwise arrangement of intra-chain contacts can be categorized as parallel, series or cross, and has been identified as a topological property. Using molecular dynamics simulations, we determine the contact order distributions and topological circuits of short semi-flexible linear and ring polymer chains with a persistence length of l p under a spherical confinement of radius R c . At low values of l p /R c , the entropy of the linear chain leads to the formation of independent contacts along the chain and accordingly, increases the fraction of series topology with respect to other topologies. However, at high l p /R c , the fraction of cross and parallel topologies are enhanced in the chain topological circuits with cross becoming predominant. At an intermediate confining regime, we identify a critical value of l p /R c , at which all topological states have equal probability. Confinement thus equalizes the probability of more complex cross and parallel topologies to the level of the more simple, non-cooperative series topology. Moreover, our topology analysis reveals distinct behaviours for ring- and linear polymers under weak confinement; however, we find no difference between ring- and linear polymers under strong confinement. Under weak confinement, ring polymers adopt parallel and series topologies with equal likelihood, while linear polymers show a higher tendency for series arrangement. The radial distribution analysis of the topology reveals a non-uniform effect of confinement on the topology of polymer chains, thereby imposing more pronounced effects on the core region than on the confinement surface. Additionally, our results reveal that over a wide range of confining radii, loops arranged in parallel and cross

Energy confinement scaling from the international stellarator database

Energy Technology Data Exchange (ETDEWEB)

Stroth, U [Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Murakami, M; Dory, R A; Yamada, H; Okamura, S; Sano, F; Obiki, T

1995-09-01

An international stellarator database on global energy confinement is presented comprising data from the ATF, CHS and Heliotron E heliotron/torsatrons and the W7-A and W7-AS shearless stellarators. Regression expressions for the energy confinement time are given for the individual devices and the combined dataset. A comparison with tokamak L mode confinement is discussed on the basis of various scaling expressions. In order to make this database available to interested colleagues, the structure of the database and the parameter list are explained in detail. More recent confinement results incorporating data from enhanced confinement regimes such as H mode are reported elsewhere. (author).

Analysis of a turbulent buoyant confined jet modeled using realizable k-ε model

KAUST Repository

El-Amin, Mohamed

2010-06-13

Through this paper, analyses of components of the unheated/heated turbulent confined jet are introduced and some models to describe them are developed. Turbulence realizable k-ε model is used to model the turbulence of this problem. Numerical simulations of 2D axisymmetric vertical hot water confined jet into a cylindrical tank have been done. Solutions are obtained for unsteady flow while velocity, pressure, temperature and turbulence distributions inside the water tank are analyzed. For seeking verification, an experiment was conducted for measuring of the temperature of the same system, and comparison between the measured and simulated temperature shows a good agreement. Using the simulated results, some models are developed to describe axial velocity, centerline velocity, radial velocity, dynamic pressure, mass flux, momentum flux and buoyancy flux for both unheated (non-buoyant) and heated (buoyant) jet. Finally, the dynamics of the heated jet in terms of the plume function which is a universal quantity and the source parameter are studied and therefore the maximum velocity can be predicted theoretically. © 2010 Springer-Verlag.

Quark confinement in a constituent quark model

International Nuclear Information System (INIS)

Langfeld, K.; Rho, M.

1995-01-01

On the level of an effective quark theory, we define confinement by the absence of quark anti-quark thresholds in correlation function. We then propose a confining Nambu-Jona-Lasinio-type model. The confinement is implemented in analogy to Anderson localization in condensed matter systems. We study the model's phase structure as well as its behavior under extreme conditions, i.e. high temperature and/or high density

Momentum Confinement at Low Torque

International Nuclear Information System (INIS)

Solomon, W.M.; Burrell, K.H.; deGrassie, J.S.; Budny, R.; Groebner, R.J.; Heidbrink, W.W.; Kinsey, J.E.; Kramer, G.J.; Makowski, M.A.; Mikkelsen, D.; Nazikian, R.; Petty, C.C.; Politzer, P.A.; Scott, S.D.; Van Zeeland, M.A.; Zarnstorff, M.C.

2007-01-01

Momentum confinement was investigated on DIII-D as a function of applied neutral beam torque at constant normalized β N , by varying the mix of co (parallel to the plasma current) and counter neutral beams. Under balanced neutral beam injection (i.e. zero total torque to the plasma), the plasma maintains a significant rotation in the co-direction. This 'intrinsic' rotation can be modeled as being due to an offset in the applied torque (i.e. an 'anomalous torque'). This anomalous torque appears to have a magnitude comparable to one co-neutral beam source. The presence of such an anomalous torque source must be taken into account to obtain meaningful quantities describing momentum transport, such as the global momentum confinement time and local diffusivities. Studies of the mechanical angular momentum in ELMing H-mode plasmas with elevated q min show that the momentum confinement time improves as the torque is reduced. In hybrid plasmas, the opposite effect is observed, namely that momentum confinement improves at high torque/rotation. The relative importance of E x B shearing between the two is modeled using GLF23 and may suggest a possible explanation.

Hydrogeologic framework and geologic structure of the Floridan aquifer system and intermediate confining unit in the Lake Okeechobee area, Florida

Science.gov (United States)

Reese, Ronald S.

2014-01-01

The successful implementation of aquifer storage and recovery (ASR) as a water-management tool requires detailed information on the hydrologic and hydraulic properties of the potential water storage zones. This report presents stratigraphic and hydrogeologic sections of the upper part of the Floridan aquifer system and the overlying confining unit or aquifer system in the Lake Okeechobee area, and contour maps of the upper contacts of the Ocala Limestone and the Arcadia Formation, which are represented in the sections. The sections and maps illustrate hydrogeologic factors such as confinement of potential storage zones, the distribution of permeability within the zones, and geologic features that may control the efficiency of injection, storage, and recovery of water, and thus may influence decisions on ASR activities in areas of interest to the Comprehensive Everglades Restoration Plan.

Innovative technology summary report: Confined sluicing end effector

International Nuclear Information System (INIS)

1998-09-01

A Confined Sluicing End-Effector (CSEE) was field tested during the summer of 1997 in Tank W-3, one of the Gunite and Associated Tanks (GAAT) at the Oak Ridge Reservation (ORR). It should be noted that the specific device used at the Oak Ridge Reservation demonstration was the Sludge Retrieval End-Effector (SREE), although in common usage it is referred to as the CSEE. Deployed by the Modified Light-Duty Utility Arm (MLDUA) and the Houdini remotely operated vehicle (ROV), the CSEE was used to mobilize and retrieve waste from the tank. After removing the waste, the CSEE was used to scarify the gunite walls of Tank W-3, removing approximately 0.1 in of material. The CSEE uses three rotating water-jets to direct a short-range pressurized jet of water to effectively mobilize the waste. Simultaneously, the water and dislodged tank waste, or scarified materials, are aspirated using a water-jet pump-driven conveyance system. The material is then pumped outside of the tank, where it can be stored for treatment. The technology, its performance, uses, cost, and regulatory issues are discussed

Infrared slavery and quark confinement

CERN Document Server

Alabiso, C

1976-01-01

The question is considered of whether the so-called infrared slavery mechanism as, e.g., being manifest in non-Abelian gauge theories, necessarily confines quarks. Making a specific ansatz for the long- range forces, the Schwinger-Dyson equation is solved for the quark Green function. Besides having a confining solution, it appears that quarks may by-pass the long-range forces and be produced. (20 refs).

Infrared slavery and quark confinement

International Nuclear Information System (INIS)

Alabiso, C.; Schierholz, G.

1976-01-01

The question of whether the so-called infrared slavery mechanism as, e.g., being manifest in non-Abelian gauge theories, necessarily confines quarks is posed. Making a specific ansatz for the long-range forces, the Schwinger-Dyson equation is solved for the quark Green function. Besides having a confining solution, it appears that quarks may by-pass the long-range forces and be produced. (Auth.)

Vortex Ring Dynamics in Radially Confined Domains

Science.gov (United States)

Stewart, Kelley; Niebel, Casandra; Jung, Sunghwan; Vlachos, Pavlos

2010-11-01

Vortex ring dynamics have been studied extensively in semi-infinite quiescent volumes. However, very little is known about vortex-ring formation in wall-bounded domains where vortex wall interaction will affect both the vortex ring pinch-off and propagation velocity. This study addresses this limitation and studies vortex formation in radially confined domains to analyze the affect of vortex-ring wall interaction on the formation and propagation of the vortex ring. Vortex rings were produced using a pneumatically driven piston cylinder arrangement and were ejected into a long cylindrical tube which defined the confined downstream domain. A range of confinement domains were studied with varying confinement diameters Velocity field measurements were performed using planar Time Resolved Digital Particle Image Velocimetry (TRDPIV) and were processed using an in-house developed cross-correlation PIV algorithm. The experimental analysis was used to facilitate the development of a theoretical model to predict the variations in vortex ring circulation over time within confined domains.

Interfacial structures in confined cap-turbulent and churn-turbulent flows

International Nuclear Information System (INIS)

Sun Xiaodong; Kim, Seungjin; Cheng Ling; Ishii, Mamoru; Beus, Stephen G.

2004-01-01

The objective of the present work is to study and model the interfacial structure development of air-water two-phase flow in a confined flow passage. Experiments of a total of 13 flow conditions in cap-turbulent and churn-turbulent flow regimes are carried out in a vertical air-water upward two-phase flow experimental loop with a test section of 200 mm in width and 10 mm in gap. Miniaturized four-sensor conductivity probes are used to measure local two-phase parameters at three different elevations for each flow condition. Bubble characteristics captured by the probes are categorized into two groups in view of the two-group interfacial area transport equation, i.e., spherical/distorted bubbles as Group 1 and cap/churn-turbulent bubbles as Group 2. The acquired local parameters are time-averaged void fraction, interfacial velocity, bubble number frequency, interfacial area concentration, and bubble Sauter mean diameter for each group of bubbles. Also, the line-averaged and area-averaged data are presented and discussed in detail. The comparisons of these parameters at different elevations demonstrate the development of interfacial structures along the flow direction due to bubble interactions and the hydrodynamic effects. Furthermore, these data can serve as one part of the experimental data for investigation of the interfacial area transport in a confined two-phase flow

A new and effective method for thermostatting confined fluids

DEFF Research Database (Denmark)

De Luca, Sergio; Billy, Todd; Hansen, Jesper Schmidt

2014-01-01

not interact with wall atoms or each other, thus behaving as virtual particles. Their displacements violate the Lindemann criterion for melting, in such a way that the net effect would not amount to an additional confining surface. One advantage over standard techniques is the reduced computational cost......, particularly for large walls, since they can be kept rigid. Another advantage over accepted strategies is the opportunity to freeze complex charged walls such as β-cristobalite. The method furthermore overcomes the problem with polar fluids such as water, as thermalized charged surfaces require higher spring...

Correlations In Confined Quantum Plasmas

International Nuclear Information System (INIS)

Dufty, J.W.

2012-01-01

This is the final report for the project 'Correlations in Confined Quantum Plasmas', NSF-DOE Partnership Grant DE FG02 07ER54946, 8/1/2007 - 7/30/2010. The research was performed in collaboration with a group at Christian Albrechts University (CAU), Kiel, Germany. That collaboration, almost 15 years old, was formalized during the past four years under this NSF-DOE Partnership Grant to support graduate students at the two institutions and to facilitate frequent exchange visits. The research was focused on exploring the frontiers of charged particle physics evolving from new experimental access to unusual states associated with confinement. Particular attention was paid to combined effects of quantum mechanics and confinement. A suite of analytical and numerical tools tailored to the specific inquiry has been developed and employed

Cylindrical fabric-confined soil structures

Science.gov (United States)

Harrison, Richard A.

A cylindrical fabric-soil structural concept for implementation on the moon and Mars which provides many advantages is proposed. The most efficient use of fabric is to fashion it into cylindrical tubes, creating cylindrical fabric-confined soil structures. The length, diameter, and curvature of the tubes will depend on the intended application. The cylindrical hoop forces provide radial confinement while end caps provide axial confinement. One of the ends is designed to allow passage of the soil into the fabric tube before sealing. Transportation requirements are reduced due to the low mass and volume of the fabric. Construction requirements are reduced due to the self-erection capability via the pneumatic exoskeleton. Maintenance requirements are reduced due to the passive nature of the concept. The structure's natural ductility is well suited for any seismic activity.

Exceptional confinement in G(2) gauge theory

International Nuclear Information System (INIS)

Holland, K.; Minkowski, P.; Pepe, M.; Wiese, U.-J.

2003-01-01

We study theories with the exceptional gauge group G(2). The 14 adjoint 'gluons' of a G(2) gauge theory transform as {3}, {3-bar} and {8} under the subgroup SU(3), and hence have the color quantum numbers of ordinary quarks, anti-quarks and gluons in QCD. Since G(2) has a trivial center, a 'quark' in the {7} representation of G(2) can be screened by 'gluons'. As a result, in G(2) Yang-Mills theory the string between a pair of static 'quarks' can break. In G(2) QCD there is a hybrid consisting of one 'quark' and three 'gluons'. In supersymmetric G(2) Yang-Mills theory with a {14} Majorana 'gluino' the chiral symmetry is Z(4) χ . Chiral symmetry breaking gives rise to distinct confined phases separated by confined-confined domain walls. A scalar Higgs field in the {7} representation breaks G(2) to SU(3) and allows us to interpolate between theories with exceptional and ordinary confinement. We also present strong coupling lattice calculations that reveal basic features of G(2) confinement. Just as in QCD, where dynamical quarks break the Z(3) symmetry explicitly, G(2) gauge theories confine even without a center. However, there is not necessarily a deconfinement phase transition at finite temperature

Enhanced cavitation and heating of flowing polymer- and lipid-shelled microbubbles and phase-shift nanodroplets during focused ultrasound exposures

Science.gov (United States)

Zhang, Siyuan; Cui, Zhiwei; Li, Chong; Zhou, Fanyu; Zong, Yujin; Wang, Supin; Wan, Mingxi

2017-03-01

Cavitation and heating are the primary mechanisms of numerous therapeutic applications of ultrasound. Various encapsulated microbubbles (MBs) and phase-shift nanodroplets (NDs) have been used to enhance local cavitation and heating, creating interests in developing ultrasound therapy using these encapsulated MBs and NDs. This work compared the efficiency of flowing polymer- and lipid-shelled MBs and phase-shift NDs in cavitation and heating during focused ultrasound (FUS) exposures. Cavitation activity and temperature were investigated when the solution of polymer- and lipid-shelled MBs and NDs flowed through the vessel in a tissue-mimicking phantom with varying flow velocities when exposed to FUS at various acoustic power levels. The inertial cavitation dose (ICD) for the encapsulated MBs and NDs were higher than those for the saline. Temperature initially increased with increasing flow velocities of the encapsulated MBs, followed by a decrease of the temperature with increasing flow velocities when the velocity was much higher. Meanwhile, ICD showed a trend of increases with increasing flow velocity. For the phase-shift NDs, ICD after the first FUS exposure was lower than those after the second FUS exposure. For the encapsulated MBs, ICD after the first FUS exposure was higher than those after the second FUS exposure. Further studies are necessary to investigate the treatment efficiency of different encapsulated MBs and phase-shift NDs in cavitation and heating.

Energy Confinement of both Ohmic and LHW Plasma on EAST

International Nuclear Information System (INIS)

Yang Yao; Gao Xiang

2011-01-01

Study on the characters of energy confinement in both Ohmic and lower hybrid wave (LHW) discharges on EAST is conducted and the linear Ohmic confinement (LOC), saturated ohmic confinement (SOC) and improved Ohmic confinement (IOC) regimes are investigated in this paper. It is observed that an improved confinement mode characterized by both a drop of D α line intensity and an increase in line average density can be triggered by a gas puffing pulse. (magnetically confined plasma)

Energy confinement in Doublet III with high-Z limiters

Energy Technology Data Exchange (ETDEWEB)

Marcus, F.B.; Adcock, S.J.; Baker, D.R.; Blau, F.P.; Brooks, N.H.; Chase, R.P.; DeBoo, J.C.; Ejima, S.; Fairbanks, E.S.; Fisher, R.K.

1980-02-01

This report describes the experimental measurements and data analysis techniques used to evaluate the energy confinement in noncircular plasmas produced in Doublet III. Major aspects of the confinement measurements and analysis techniques are summarized. Machine parameters, diagnostic systems and discharge parameters relavent to the confinement measurements are given. Magnetic analysis techniques used to determine the plasma shape are reviewed. Scaling of the on-axis values of electron temperature, confinement time and Z/sub eff/ with plasma density is presented. Comparison with scaling results from other circular tokamaks is discussed. Numerical and analytic techniques developed for calculating the plasma energy confinement time and self-consistent profiles of density, temperature, current, and flux in non-circular geometries are described. These techniques are applied to the data and used to determine the central and global electron energy confinement time for a typical doublet plasma. Additional aspects of the confinement such as the radial dependence of the electron thermal conductivity and the estimated ion temperature are explored with the aid of a non-circular transport simulation code. The results of the confinement measurements are summarized and discussed. A brief summary of the theoretically expected effects of noncircularity on plasma confinement is included for reference as Appendix I.

Monopole current dynamics and color confinement

International Nuclear Information System (INIS)

Ichie, H.; Suganuma, H.; Tanaka, A.

1998-01-01

Color confinement can be understood by the dual Higgs theory, where monopole condensation leads to the exclusion of the electric flux from the QCD vacuum. We study the role of the monopole for color confinement by investigating the monopole current system. When the self-energy of the monopole current is small enough, long and complicated monopole world-lines appear, which is a signal of monopole condensation. In the dense monopole system, the Wilson loop obeys the area-law, and the string tension and the monopole density have similar behavior as the function of the self-energy, which seems that monopole condensation leads to color confinement. On the long-distance physics, the monopole current system almost reproduces essential features of confinement properties in lattice QCD. In the short-distance physics, however, the monopole-current theory would become nonlocal and complicated due to the monopole size effect. This monopole size would provide a critical scale of QCD in terms of the dual Higgs mechanism. (orig.)

Extended BRS algebra and color confinement

International Nuclear Information System (INIS)

Shintani, Meiun.

1984-02-01

We examine the color confinement scheme and its realizations proposed by Kugo and Ojima. Using the Nakanishi's theorem, we obtain a representation of the extended BRS algebra compatible with the so-called K-O condition of their confinement criteria. However, it turns out that the representation is not physically acceptable, and thus their scheme lacks self-consistency at the level of realizations. We also clarify what kind of ghost structures are suggested by the well-definedness or ill-definedness of the charge operator Nsup(a) constituting a part of the global color charge operator. It is shown that there are four possible cancellation mechanisms of ghosts. In particular, it turns out that the octet of ghosts suggested by Nishijima in his confinement theory arises from the well-definedness of the Nsup(a) charge, whereas the elementary quartet arises from the ill-definedness of the Nsup(a). Moreover, from the octet structures, we deduce the confinement condition which replaces the K-O condition. (author)

Physics of inertial confinement pellets

International Nuclear Information System (INIS)

Mead, W.C.

1979-01-01

An overview of inertial confinement fusion pellet physics is given. A discussion is presented of current estimated ICF driver requirements and a couple of pellet examples. The physics of driver/plasma coupling for two drivers which are being considered, namely a laser driver and a heavy ion accelerator driver, is described. Progress towards inertial confinement fusion that has been made using laser drivers in target experiments to date is discussed

On the structure and dynamics of water associated with single-supported zwitterionic and anionic membranes

DEFF Research Database (Denmark)

Miskowiec, A.; Buck, Z. N.; Hansen, Flemming Yssing

2017-01-01

We have used high-resolution quasielastic neutron scattering (QENS) to investigate the dynamics of water molecules (time scale of motion similar to ∼10-11- 10-9 s) in proximity to single-supported bilayers of the zwitterionic lipid DMPC (1,2-dimyristoyl-sn-glycero-3-phosphorylcholine) and the ani......We have used high-resolution quasielastic neutron scattering (QENS) to investigate the dynamics of water molecules (time scale of motion similar to ∼10-11- 10-9 s) in proximity to single-supported bilayers of the zwitterionic lipid DMPC (1,2-dimyristoyl-sn-glycero-3-phosphorylcholine......) and the anionic lipid DMPG (1,2-dimyristoyl-sn-glycero-3-phosphoglycerol) in the temperature range 160-295 K. For both membranes, the temperature dependence of the intensity of neutrons scattered elastically and incoherently from these samples indicates a series of freezing/melting transitions...... the membrane and two types of confined water in closer proximity to the lipids. Specifically, we propose a water type termed "confined 2" located within and just above the lipid head groups of the membrane and confined 1 water that lies between the bulk-like and confined 2 water. Confined 1 water is only...

Radiolysis of water confined in zeolites 4A: application to tritiated water storage

International Nuclear Information System (INIS)

Frances, Laetitia

2014-01-01

Self-radiolysis of tritiated water (HTO) adsorbed in zeolites 4A shows differences compared to free-bulk water radiolysis. We studied the roles of zeolites on that. We took special care with the influence of water loading ratio. We first exposed zeolites to external irradiations, reproducing selectively the dose or the dose rate measured in the case of tritiated water storage. This strategy enables the characterising of the samples after their irradiation since they are not contaminated by tritium. Those experiments revealed the high stability of zeolites 4A. We used a second approach which consisted in studying the precise case of self-radiolysis of tritiated water, in order to obtain radiolytic yields representative of HTO storage. The comparison between the quantities of gas released when zeolites are exposed to the three different sources that we used (electrons accelerated at 10 MeV, γ released by radioactive decay of 137 Cs and β - released by radioactive decay of tritium) revealed the strong influence of the dose rate. Moreover, whatever the irradiation source, zeolites 4A first favour hydrogen release and secondarily oxygen release too. On the contrary, zeolites favour next a recombination between those radiolytic products, with a dependence on their water loading ratio. Several processes are discussed to explain such a phenomena, not noticed during the free-bulk water radiolysis. (author) [fr

Structure and Barrier Properties of Multinanolayered Biodegradable PLA/PBSA Films: Confinement Effect via Forced Assembly Coextrusion.

Science.gov (United States)

Messin, Tiphaine; Follain, Nadège; Guinault, Alain; Sollogoub, Cyrille; Gaucher, Valérie; Delpouve, Nicolas; Marais, Stéphane

2017-08-30

Multilayer coextrusion processing was applied to produce 2049-layer film of poly(butylene succinate-co-butylene adipate) (PBSA) confined against poly(lactic acid) (PLA) using forced assembly, where the PBSA layer thickness was about 60 nm. This unique technology allowed to process semicrystalline PBSA as confined polymer and amorphous PLA as confining polymer in a continuous manner. The continuity of PBSA layers within the 80/20 wt % PLA/PBSA layered films was clearly evidenced by atomic force microscopy (AFM). Similar thermal events to the reference films were revealed by thermal studies; indicating no diffusion of polymers during the melt-processing. Mechanical properties were measured for the multilayer film and the obtained results were those expected considering the fraction of each polymer, revealing the absence of delamination in the PLA/PBSA multinanolayer film. The confinement effect induced by PLA led to a slight orientation of the crystals, an increase of the rigid amorphous fraction (RAF) in PBSA with a densification of this fraction without changing film crystallinity. These structural changes allowed to strongly improve the water vapor and gas barrier properties of the PBSA layer into the multilayer film up to two decades in the case of CO 2 gas. By confining the PBSA structure in very thin and continuous layers, it was then possible to improve the barrier performances of a biodegradable system and the resulting barrier properties were successfully correlated to the effect of confinement on the microstructure and the chain segment mobility of the amorphous phase. Such investigation on these multinanolayers of PLA/PBSA with the aim of evidencing relationships between microstructure implying RAF and barrier performances has never been performed yet. Besides, gas and water permeation results have shown that the barrier improvement obtained from the multilayer was mainly due to the reduction of solubility linked to the reduction of the free volume while

Climate conditions in bedded confinement buildings

Science.gov (United States)

Confinement buildings are utilized for finishing cattle to allow more efficient collection of animal waste and to buffer animals against adverse climatic conditions. Environmental data were obtained from a 29 m wide x 318 m long bedded confinement building with the long axis oriented east to west. T...

Quark propagators and correlators in a confining vacuum

International Nuclear Information System (INIS)

Simonov, Yu.A.

1987-01-01

Quark propagators, quark-antiquark Green functions and photon selfenergy operator Π (2) (k) are considered in the background (anti)selfdual field. The cases of a homogeneous selfdual field in d=4 and magnetic field in d=2 are studied in detail. Isolated quarks and quark-antiquark pairs are shown to be confined in those cases with the quadratic form of confining potential. In the space filled with domains of the homogeneous field with random directions the confining potential is of linear form, and the colorless qq-bar pair is not confined

Plasma confinement system and methods for use

Science.gov (United States)

Jarboe, Thomas R.; Sutherland, Derek

2017-09-05

A plasma confinement system is provided that includes a confinement chamber that includes one or more enclosures of respective helicity injectors. The one or more enclosures are coupled to ports at an outer radius of the confinement chamber. The system further includes one or more conductive coils aligned substantially parallel to the one or more enclosures and a further set of one or more conductive coils respectively surrounding portions of the one or more enclosures. Currents may be provided to the sets of conductive coils to energize a gas within the confinement chamber into a plasma. Further, a heat-exchange system is provided that includes an inner wall, an intermediate wall, an outer wall, and pipe sections configured to carry coolant through cavities formed by the walls.

Experimental Studies on Permeability of Intact and Singly Jointed Meta-Sedimentary Rocks Under Confining Pressure

Science.gov (United States)

Wong, Louis Ngai Yuen; Li, Diyuan; Liu, Gang

2013-01-01

Three different types of permeability tests were conducted on 23 intact and singly jointed rock specimens, which were cored from rock blocks collected from a rock cavern under construction in Singapore. The studied rock types belong to inter-bedded meta-sandstone and meta-siltstone with very low porosity and high uniaxial compressive strength. The transient pulse water flow method was employed to measure the permeability of intact meta-sandstone under a confining pressure up to 30 MPa. It showed that the magnitude order of meta-sandstone's intrinsic permeability is about 10-18 m2. The steady-state gas flow method was used to measure the permeability of both intact meta-siltstone and meta-sandstone in a triaxial cell under different confining pressures spanning from 2.5 to 10 MPa. The measured permeability of both rock types ranged from 10-21 to 10-20 m2. The influence of a single natural joint on the permeability of both rock types was studied by using the steady-state water flow method under different confining pressures spanning from 1.25 to 5.0 MPa, including loading and unloading phases. The measured permeability of both jointed rocks ranged from 10-13 to 10-11 m2, where the permeability of jointed meta-siltstone was usually slightly lower than that of jointed meta-sandstone. The permeability of jointed rocks decreases with increasing confining pressure, which can be well fitted by an empirical power law relationship between the permeability and confining pressure or effective pressure. The permeability of partly open cracked specimens is lower than that of open cracked specimens, but it is higher than that of the specimen with a dominant vein for the meta-sandstone under the same confining pressure. The permeability of open cracked rock specimens will partially recover during the unloading confining pressure process. The equivalent crack (joint) aperture is as narrow as a magnitude order of 10-6 m (1 μm) in the rock specimens under confining pressures

A compliant mechanism for inspecting extremely confined spaces

Science.gov (United States)

Mascareñas, David; Moreu, Fernando; Cantu, Precious; Shields, Daniel; Wadden, Jack; El Hadedy, Mohamed; Farrar, Charles

2017-11-01

We present a novel, compliant mechanism that provides the capability to navigate extremely confined spaces for the purpose of infrastructure inspection. Extremely confined spaces are commonly encountered during infrastructure inspection. Examples of such spaces can include pipes, conduits, and ventilation ducts. Often these infrastructure features go uninspected simply because there is no viable way to access their interior. In addition, it is not uncommon for extremely confined spaces to possess a maze-like architecture that must be selectively navigated in order to properly perform an inspection. Efforts by the imaging sensor community have resulted in the development of imaging sensors on the millimeter length scale. Due to their compact size, they are able to inspect many extremely confined spaces of interest, however, the means to deliver these sensors to the proper location to obtain the desired images are lacking. To address this problem, we draw inspiration from the field of endoscopic surgery. Specifically we consider the work that has already been done to create long flexible needles that are capable of being steered through the human body. These devices are typically referred to as ‘steerable needles.’ Steerable needle technology is not directly applicable to the problem of navigating maze-like arrangements of extremely confined spaces, but it does provide guidance on how this problem should be approached. Specifically, the super-elastic nitinol tubing material that allows steerable needles to operate is also appropriate for the problem of navigating maze-like arrangements of extremely confined spaces. Furthermore, the portion of the mechanism that enters the extremely confined space is completely mechanical in nature. The mechanical nature of the device is an advantage when the extremely confined space features environmental hazards such as radiation that could degrade an electromechanically operated mechanism. Here, we present a compliant mechanism

Density and Phase State of a Confined Nonpolar Fluid

Science.gov (United States)

Kienle, Daniel F.; Kuhl, Tonya L.

2016-07-01

Measurements of the mean refractive index of a spherelike nonpolar fluid, octamethytetracylclosiloxane (OMCTS), confined between mica sheets, demonstrate direct and conclusive experimental evidence of the absence of a first-order liquid-to-solid phase transition in the fluid when confined, which has been suggested to occur from previous experimental and simulation results. The results also show that the density remains constant throughout confinement, and that the fluid is incompressible. This, along with the observation of very large increases (many orders of magnitude) in viscosity during confinement from the literature, demonstrate that the molecular motion is limited by the confining wall and not the molecular packing. In addition, the recently developed refractive index profile correction method, which enables the structural perturbation inherent at a solid-liquid interface and that of a liquid in confinement to be determined independently, was used to show that there was no measurable excess or depleted mass of OMCTS near the mica surface in bulk films or confined films of only two molecular layers.

Diffusion of Finite-Size Particles in Confined Geometries

KAUST Repository

Bruna, Maria; Chapman, S. Jonathan

2013-01-01

The diffusion of finite-size hard-core interacting particles in two- or three-dimensional confined domains is considered in the limit that the confinement dimensions become comparable to the particle's dimensions. The result is a nonlinear diffusion equation for the one-particle probability density function, with an overall collective diffusion that depends on both the excluded-volume and the narrow confinement. By including both these effects, the equation is able to interpolate between severe confinement (for example, single-file diffusion) and unconfined diffusion. Numerical solutions of both the effective nonlinear diffusion equation and the stochastic particle system are presented and compared. As an application, the case of diffusion under a ratchet potential is considered, and the change in transport properties due to excluded-volume and confinement effects is examined. © 2013 Society for Mathematical Biology.

Impurity confinement and transport in high confinement regimes without edge localized modes on DIII-D

Energy Technology Data Exchange (ETDEWEB)

Grierson, B. A., E-mail: bgriers@pppl.gov; Nazikian, R. M.; Solomon, W. M. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Burrell, K. H.; Garofalo, A. M.; Belli, E. A.; Staebler, G. M.; Evans, T. E.; Smith, S. P.; Chrobak, C. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Fenstermacher, M. E. [Lawerence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States); McKee, G. R. [Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53796 (United States); Orlov, D. M. [Center for Energy Research, University of California San Diego, 9500 Gilman Dr., La Jolla, California 92093-0417 (United States); Chrystal, C. [University of California San Diego, 9500 Gilman Dr., La Jolla, California 92093-0417 (United States)

2015-05-15

Impurity transport in the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] is investigated in stationary high confinement (H-mode) regimes without edge localized modes (ELMs). In plasmas maintained by resonant magnetic perturbation (RMP), ELM-suppression, and QH-mode, the confinement time of fluorine (Z = 9) is equivalent to that in ELMing discharges with 40 Hz ELMs. For selected discharges with impurity injection, the impurity particle confinement time compared to the energy confinement time is in the range of τ{sub p}/τ{sub e}≈2−3. In QH-mode operation, the impurity confinement time is shown to be smaller for intense, coherent magnetic, and density fluctuations of the edge harmonic oscillation than weaker fluctuations. Transport coefficients are derived from the time evolution of the impurity density profile and compared to neoclassical and turbulent transport models NEO and TGLF. Neoclassical transport of fluorine is found to be small compared to the experimental values. In the ELMing and RMP ELM-suppressed plasma, the impurity transport is affected by the presence of tearing modes. For radii larger than the mode radius, the TGLF diffusion coefficient is smaller than the experimental value by a factor of 2–3, while the convective velocity is within error estimates. Low levels of diffusion are observed for radii smaller than the tearing mode radius. In the QH-mode plasma investigated, the TGLF diffusion coefficient is higher inside of ρ=0.4 and lower outside of 0.4 than the experiment, and the TGLF convective velocity is more negative by a factor of approximately 1.7.

How to Recharge a Confined Aquifer: An Exploration of Geologic Controls on Groundwater Storage.

Science.gov (United States)

Maples, S.; Fogg, G. E.; Maxwell, R. M.; Liu, Y.

2017-12-01

Decreased snowpack storage and groundwater overdraft in California has increased interest in managed aquifer recharge (MAR) of excess winter runoff to the Central Valley aquifer system, which has unused storage capacity that far exceeds the state's surface reservoirs. Recharge to the productive, confined aquifer system remains a challenge due to the presence of nearly-ubiquitous, multiple silt and clay confining units that limit recharge pathways. However, previous studies have identified interconnected networks of sand and gravel deposits that bypass the confining units and accommodate rapid, high-volume recharge to the confined aquifer system in select locations. We use the variably-saturated, fully-integrated groundwater/surface-water flow code, ParFlow, in combination with a high-resolution, transition probability Markov-chain geostatistical model of the subsurface geologic heterogeneity of the east side of the Sacramento Valley, CA, to characterize recharge potential across a landscape that includes these geologic features. Multiple 180-day MAR simulations show that recharge potential is highly dependent on subsurface geologic structure, with a several order-of-magnitude range of recharge rates and volumes across the landscape. Where there are recharge pathways to the productive confined-aquifer system, pressure propagation in the confined system is widespread and rapid, with multi-kilometer lateral pressure propagation. Although widespread pressure propagation occurs in the confined system, only a small fraction of recharge volume is accommodated there. Instead, the majority of recharge occurs by filling unsaturated pore spaces. Where they outcrop at land surface, high-K recharge pathways fill rapidly, accommodating the majority of recharge during early time. However, these features become saturated quickly, and somewhat counterintuitively, the low-K silt and clay facies accommodate the majority of recharge volume during most of the simulation. These findings

Cockroaches traverse crevices, crawl rapidly in confined spaces, and inspire a soft, legged robot

Science.gov (United States)

Jayaram, Kaushik; Full, Robert J.

2016-01-01

Jointed exoskeletons permit rapid appendage-driven locomotion but retain the soft-bodied, shape-changing ability to explore confined environments. We challenged cockroaches with horizontal crevices smaller than a quarter of their standing body height. Cockroaches rapidly traversed crevices in 300–800 ms by compressing their body 40–60%. High-speed videography revealed crevice negotiation to be a complex, discontinuous maneuver. After traversing horizontal crevices to enter a vertically confined space, cockroaches crawled at velocities approaching 60 cm⋅s−1, despite body compression and postural changes. Running velocity, stride length, and stride period only decreased at the smallest crevice height (4 mm), whereas slipping and the probability of zigzag paths increased. To explain confined-space running performance limits, we altered ceiling and ground friction. Increased ceiling friction decreased velocity by decreasing stride length and increasing slipping. Increased ground friction resulted in velocity and stride length attaining a maximum at intermediate friction levels. These data support a model of an unexplored mode of locomotion—“body-friction legged crawling” with body drag, friction-dominated leg thrust, but no media flow as in air, water, or sand. To define the limits of body compression in confined spaces, we conducted dynamic compressive cycle tests on living animals. Exoskeletal strength allowed cockroaches to withstand forces 300 times body weight when traversing the smallest crevices and up to nearly 900 times body weight without injury. Cockroach exoskeletons provided biological inspiration for the manufacture of an origami-style, soft, legged robot that can locomote rapidly in both open and confined spaces. PMID:26858443

Random walks and polygons in tight confinement

International Nuclear Information System (INIS)

Diao, Y; Ernst, C; Ziegler, U

2014-01-01

We discuss the effect of confinement on the topology and geometry of tightly confined random walks and polygons. Here the walks and polygons are confined in a sphere of radius R ≥ 1/2 and the polygons are equilateral with n edges of unit length. We illustrate numerically that for a fixed length of random polygons the knotting probability increases to one as the radius decreases to 1/2. We also demonstrate that for random polygons (walks) the curvature increases to πn (π(n – 1)) as the radius approaches 1/2 and that the torsion decreases to ≈ πn/3 (≈ π(n – 1)/3). In addition we show the effect of length and confinement on the average crossing number of a random polygon

The cruel and unusual phenomenology of solitary confinement.

Science.gov (United States)

Gallagher, Shaun

2014-01-01

What happens when subjects are deprived of intersubjective contact? This paper looks closely at the phenomenology and psychology of one example of that deprivation: solitary confinement. It also puts the phenomenology and psychology of solitary confinement to use in the legal context. Not only is there no consensus on whether solitary confinement is a "cruel and unusual punishment," there is no consensus on the definition of the term "cruel" in the use of that legal phrase. I argue that we can find a moral consensus on the meaning of "cruelty" by looking specifically at the phenomenology and psychology of solitary confinement.

Higher representations: Confinement and large N

International Nuclear Information System (INIS)

Sannino, Francesco

2005-01-01

We investigate the confining phase transition as a function of temperature for theories with dynamical fermions in the two index symmetric and antisymmetric representation of the gauge group. By studying the properties of the center of the gauge group we predict for an even number of colors a confining phase transition, if second order, to be in the universality class of Ising in three dimensions. This is due to the fact that the center group symmetry does not break completely for an even number of colors. For an odd number of colors the center group symmetry breaks completely. This pattern remains unaltered at a large number of colors. The confining/deconfining phase transition in these theories at large and finite N is not mapped in the one of super Yang-Mills theory. We extend the Polyakov loop effective theory to describe the confining phase transition of the theories studied here for a generic number of colors. Our results are not modified when adding matter in the same higher dimensional representations of the gauge group. We comment on the interplay between confinement and chiral symmetry in these theories and suggest that they are ideal laboratories to shed light on this issue also for ordinary QCD. We compare the free energy as a function of temperature for different theories. We find that the conjectured thermal inequality between the infrared and ultraviolet degrees of freedom computed using the free energy does not lead to new constraints on asymptotically free theories with fermions in higher dimensional representations of the gauge group. Since the center of the gauge group is an important quantity for the confinement properties at zero temperature our results are relevant here as well

Magnetic well for plasma confinement

International Nuclear Information System (INIS)

Valfells, A.; Chiu, Y.C.

1977-01-01

A multipole magnetic well for plasma confinement includes a plurality of current-carrying coils placed on planes corresponding to the facets of a regular polyhedron that can be symmetrically circumscribed about a sphere. The direction of current in the coils is such as to minimize the flux density at the center of the polyhedron, thereby providing a confinement well with three-dimensional symmetry having an increasing flux density in all directions from the center. 16 claims, 18 figures

Neutron spectroscopy for confinement studies

International Nuclear Information System (INIS)

Zorn, R.

2010-01-01

Neutron spectroscopy is an important method for the study of microscopic dynamics because it captures the spatial as well as the temporal aspects of the atomic or molecular motion. In this article techniques will be presented which are of special importance for the study of confined systems. Many of these are based on the fact that neutron scattering is isotope-dependent. Possible sources of systematic errors in measurements of confined systems will be pointed out. (author)

Diffusion of Finite-Size Particles in Confined Geometries

KAUST Repository

Bruna, Maria

2013-05-10

The diffusion of finite-size hard-core interacting particles in two- or three-dimensional confined domains is considered in the limit that the confinement dimensions become comparable to the particle\\'s dimensions. The result is a nonlinear diffusion equation for the one-particle probability density function, with an overall collective diffusion that depends on both the excluded-volume and the narrow confinement. By including both these effects, the equation is able to interpolate between severe confinement (for example, single-file diffusion) and unconfined diffusion. Numerical solutions of both the effective nonlinear diffusion equation and the stochastic particle system are presented and compared. As an application, the case of diffusion under a ratchet potential is considered, and the change in transport properties due to excluded-volume and confinement effects is examined. © 2013 Society for Mathematical Biology.

Perspectives on confinement in helical systems

International Nuclear Information System (INIS)

Itoh, Kimitaka; Itoh, Sanae

1989-01-01

A review on recent experimental results and theoretical models on anomalous transport and density limit in toroidal helical devices is presented. Importance of transport problems is discussed. Experiments on Heliotron-E, Wendelstein-VIIA and new devices, i.e., ATF, Wendelstein-VIIAS and CHS, are reviewed and an overview on confinement property is given. From recent experimental results one sees that there are anomalous transport, which increases with temperature, and density limit, and that they limit the energy confinement time as well as the attainable beta value. The confinement characteristics of the scrape off layer plasma and loss cone loss are discussed, and perspectives on the high temperature plasma are given. These anomalous transport and density limit will be difficult obstacles in realizing a reactor grade plasma in helical systems. It is an urgent task to draw a realistic picture of the confinement based on the present data base. The relevant knowledge now would be critically essential for the successful development of the research in 1990's. (author) 102 refs

Comments on experimental results of energy confinement of tokamak plasmas

International Nuclear Information System (INIS)

Chu, T.K.

1989-04-01

The results of energy-confinement experiments on steady-state tokamak plasmas are examined. For plasmas with auxiliary heating, an analysis based on the heat diffusion equation is used to define heat confinement time (the incremental energy confinement time). For ohmically sustained plasmas, experiments show that the onset of the saturation regime of energy confinement, marfeing, detachment, and disruption are marked by distinct values of the parameter /bar n//sub e///bar j/. The confinement results of the two types of experiments can be described by a single surface in 3-dimensional space spanned by the plasma energy, the heating power, and the plasma density: the incremental energy confinement time /tau//sub inc/ = ΔW/ΔP is the correct concept for describing results of heat confinement in a heating experiment; the commonly used energy confinement time defined by /tau//sub E/ = W/P is not. A further examination shows that the change of edge parameters, as characterized by the change of the effective collision frequency ν/sub e/*, governs the change of confinement properties. The totality of the results of tokamak experiments on energy confinement appears to support a hypothesis that energy transport is determined by the preservation of the pressure gradient scale length. 70 refs., 6 figs., 1 tab

Helical Confinement Concepts

Energy Technology Data Exchange (ETDEWEB)

Beidler, C; Brakel, R; Burhenn, R; Dinklage, A; Erckmann, V; Feng, Y; Geiger, J; Hartmann, D; Hirsch, M; Jaenicke, R; Koenig, R; Laqua, H P; Maassberg, H; Wagner, F; Weller, A; Wobig, H [Max-Planck Institut fuer Plasmaphysik, EURATOM Association, Greifswald (Germany)

2012-09-15

Stellarators, conceived 1951 by Lyman Spitzer in Princeton, are toroidal devices that confine a plasma in a magnetic field which originates from currents in coils outside the plasma. A plasma current driven by external means, for example by an ohmic transformer, is not required for confinement. Supplying the desired poloidal field component by external coils leads to a helically structured plasma topology. Thus stellarators - or helical confinement devices - are fully three-dimensional in contrast to the toroidal (rotational) symmetry of tokamaks. As stellarators can be free of an inductive current, whose radial distribution depends on the plasma parameters, their equilibrium must not be established via the evolving plasma itself, but to a first order already given by the vacuum magnetic field. They do not need an active control (like positional feedback) and therefore cannot suffer from its failure. The outstanding conceptual advantage of stellarators is the potential of steady state plasma operation without current drive. As there is no need for current drive, the recirculating power is expected to be smaller than in equivalent tokamaks. The lack of a net current avoids current driven instabilities; specifically, no disruptions, no resistive wall modes and no conventional or neoclassical tearing modes appear. Second order pressure-driven currents (Pfirsch-Schlueter, bootstrap) exist but they can be modified and even minimized by the magnetic design. The magnetic configuration of helical devices naturally possesses a separatrix, which allows the implementation of a helically structured divertor for exhaust and impurity control. (author)

Confinement and quark structure of light hadrons

International Nuclear Information System (INIS)

Efimov, G.V.; Ivanov, M.A.

1988-01-01

We present a quark confinement model (QCM) for the description of the low-energy physics of light hadrons (mesons and baryons). The model is based on two hypotheses. First, the quark confinement is realized as averaging over vacuum gluon fields which are believed to provide the confinement of any colour objects. Second, hadrons are treated as collective colourless excitations of quark-gluon interactions. The description of strong, electromagnetic and weak interactions of mesons and baryons at the low energy is given from a unique point of view

High temperature L- and H-mode confinement in JET

International Nuclear Information System (INIS)

Balet, B.; Boyd, D.A.; Campbell, D.J.

1990-01-01

The energy confinement properties of low density, high ion temperature L- and H-mode plasmas are investigated. For L-mode plasmas it is shown that, although the global confinement is independent of density, the energy confinement in the central region is significantly better at low densities than at higher densities. The improved confinement appears to be associated with the steepness of the density gradient. For the H-mode phase, although the confinement at the edge is dramatically improved, which is once again associated with the steep density gradient in the edge region, the central confinement properties are essentially the same as for the standard L-mode. The results are compared in a qualitative manner with the predictions of the ion temperature gradient instability theory and appear to be in disagreement with some aspects of this theory. (author). 13 refs, 15 figs

Solitons and confinement

International Nuclear Information System (INIS)

Swieca, J.A.

1976-01-01

Some aspects of two recent developments in quantum field theory are discussed. First, related with 'extended particles' such as soliton, kink and the 't Hooft monopole. Second, with confinement of particles which are realized in the Schwinger model [pt

Evaluation of the confinement option for LMRs

International Nuclear Information System (INIS)

Himes, D.A.; Stepnewski, D.D.; Franz, G.R.

1985-12-01

The coolant in liquid metal cooled reactors operates at low pressures and therefore contains relatively little stored energy compared to LWR systems. This presents the possibility of using a more conventional building for containment coupled with a confinement system which vents the internal volume of the building through a filter/scrubber. The confinement system would be designed to keep the internal pressure in the containment near atmospheric thereby minimizing unfiltered leakage. The principal benefits of such an arrangement would be lower capital cost and less stringent leaktightness requirements permitting simpler and less disruptive testing. In conclusion, the confinement system assumed here would reduce consequences to the public of an LMR HCDA to acceptable levels. However control room doses are unacceptable due to the noble gas concentration inside the control room. A confinement system is therefore a viable design option for LMR's provided means are included for keeping noble gases out of the control room. Such means are readily available including, for example, selectable remote air intakes, an exhaust stack, or a noble gas filter. Probably the most satisfactory alternative would be a large cryogenic filter on the confinement system exhaust

Generating equilateral random polygons in confinement II

International Nuclear Information System (INIS)

Diao, Y; Ernst, C; Montemayor, A; Ziegler, U

2012-01-01

In this paper we continue an earlier study (Diao et al 2011 J. Phys. A: Math. Theor. 44 405202) on the generation algorithms of random equilateral polygons confined in a sphere. Here, the equilateral random polygons are rooted at the center of the confining sphere and the confining sphere behaves like an absorbing boundary. One way to generate such a random polygon is the accept/reject method in which an unconditioned equilateral random polygon rooted at origin is generated. The polygon is accepted if it is within the confining sphere, otherwise it is rejected and the process is repeated. The algorithm proposed in this paper offers an alternative to the accept/reject method, yielding a faster generation process when the confining sphere is small. In order to use this algorithm effectively, a large, reusable data set needs to be pre-computed only once. We derive the theoretical distribution of the given random polygon model and demonstrate, with strong numerical evidence, that our implementation of the algorithm follows this distribution. A run time analysis and a numerical error estimate are given at the end of the paper. (paper)

Packing frustration in dense confined fluids.

Science.gov (United States)

Nygård, Kim; Sarman, Sten; Kjellander, Roland

2014-09-07

Packing frustration for confined fluids, i.e., the incompatibility between the preferred packing of the fluid particles and the packing constraints imposed by the confining surfaces, is studied for a dense hard-sphere fluid confined between planar hard surfaces at short separations. The detailed mechanism for the frustration is investigated via an analysis of the anisotropic pair distributions of the confined fluid, as obtained from integral equation theory for inhomogeneous fluids at pair correlation level within the anisotropic Percus-Yevick approximation. By examining the mean forces that arise from interparticle collisions around the periphery of each particle in the slit, we calculate the principal components of the mean force for the density profile--each component being the sum of collisional forces on a particle's hemisphere facing either surface. The variations of these components with the slit width give rise to rather intricate changes in the layer structure between the surfaces, but, as shown in this paper, the basis of these variations can be easily understood qualitatively and often also semi-quantitatively. It is found that the ordering of the fluid is in essence governed locally by the packing constraints at each single solid-fluid interface. A simple superposition of forces due to the presence of each surface gives surprisingly good estimates of the density profiles, but there remain nontrivial confinement effects that cannot be explained by superposition, most notably the magnitude of the excess adsorption of particles in the slit relative to bulk.

Dancing droplets: Contact angle, drag, and confinement

Science.gov (United States)

Benusiglio, Adrien; Cira, Nate; Prakash, Manu

2015-11-01

When deposited on a clean glass slide, a mixture of water and propylene glycol forms a droplet of given contact angle, when both pure liquids spread. (Cira, Benusiglio, Prakash: Nature, 2015). The droplet is stabilized by a gradient of surface tension due to evaporation that induces a Marangoni flow from the border to the apex of the droplets. The apparent contact angle of the droplets depends on both their composition and the external humidity as captured by simple models. These droplets present remarkable properties such as lack of a large pinning force. We discuss the drag on these droplets as a function of various parameters. We show theoretical and experimental results of how various confinement geometries change the vapor gradient and the dynamics of droplet attraction.

Colloid chemical aspects of the ''confined bentonite concept''

International Nuclear Information System (INIS)

Bell, J.C. Le

1978-03-01

Measurements of the amount of particles released from a bentonite gel by light scattering and visual inspection show that while particles are released in distilled water, the gel will be coagulated if in contact with ground water and consequently the release of particles is negligibly small. Studies of sedimentation volumes by ultracentrifugation also clearly indicate that the bentonite in contact with ground water under the repository pressure will form a completely stable coagulated gel. The swelling of confined bentonite was studied in an ''artificial crack'' of width 0.5 mm. The bentonite flowed readily into this crack and into the much narrower crack formed when the cell was broken. The swelling properties of the bentonite at the repository depth are discussed. It is argued that the gel, if sufficient volume is available, will swell spontaneously to a volume that is approximately 30 % larger than the initial one and then form a stable, coagulated gel containing 30-35 % water in equilibrium with the ground water. Investigations of the diffusion of colloidal matter (sodium lignosulphonate molecules of mean diameter 6 nm) and calcium ions into a dilute bentonite gel show that colloidal matter very probably will have a negligible rate of diffusion while the calcium ions diffuse rapidly. This implies that the initial bentonite gel which is partially in its sodium form will be completely exchanged to its calcium form when brought into contact with ground water which ensures that it will remain coagulated even in its swollen state

Plasma confinement in the TMX tandem mirror

International Nuclear Information System (INIS)

Hooper, E.B. Jr.; Allen, S.L.; Casper, T.A.

1981-01-01

Plasma confinement in the Tandem Mirror Experiment (TMX) is described. Axially confining potentials are shown to exist throughout the central 20-cm core of TMX. Axial electron-confinement time is up to 100 times that of single-cell mirror machines. Radial transport of ions is smaller than axial transport near the axis. It has two parts at large radii: nonambipolar, in rough agreement with predictions from resonant-neoclassical transport theory, and ambipolar, observed near the plasma edge under certain conditions, accompanied by a low-frequency, m = 1 instability or strong turbulence

The cruel and unusual phenomenology of solitary confinement

Directory of Open Access Journals (Sweden)

Shaun eGallagher

2014-06-01

Full Text Available What happens when subjects are deprived of intersubjective contact? This paper looks closely at the phenomenology and psychology of one example of that deprivation: solitary confinement. It also puts the phenomenology and psychology of solitary confinement to use in the legal context. Not only is there no consensus on whether solitary confinement is a cruel and unusual punishment, there is no consensus on the definition of the term ‘cruel’ in the use of that legal phrase. I argue that we can find a moral consensus on the meaning of ‘cruelty’ by looking specifically at the phenomenology and psychology of solitary confinement.

ABWR3. Passive double confinement and SA population dose evaluation for the innovative ABWR

International Nuclear Information System (INIS)

Matsumoto, Keiji; Hosomi, Kenji; Sato, Takashi

2015-01-01

iB1350 stands for an innovative, intelligent and inexpensive BWR 1350. It is the first Generation III.7 reactor after the Fukushima Daiichi accident. The iB1350 uses the Mark W containment and the in-containment filtered venting system (IFVS). The Mark W containment is made of reinforced concrete and has double cylinder FP barriers. There are also IC/PCCS pools, a fuel pool and a dryer separator (DS) pool on the top slab of the containment. These pools work as water seal for FP leakage through the top slab. Most FP such as CsI are scrubbed in the pools. The containment head is also submerged in the reactor well pool. The pool water works as shielding for radiation from the reactor core during normal operation and water seal for FP scrubbing dining a severe accident. The base mat concrete is covered with the S/P and the core catcher that is also submerged with corium flooding water during an accident. Therefore, the Mark W containment has passive double confinement barriers for FP. Moreover, the IFVS works as in-containment filtered venting system that scrubs FP from the wet well (WW) and the dry well (DW). The filtered venting tank is arranged in the outer well (OW) of the Mark W containment. Even noble gases and organic iodine going through the filtered venting system are still confined inside the containment and never released directly to the environment. The IFVS uses the innovative passive containment cooling system (iPCCS) as the pre-stage heat removal system. The iPCCS has a normal open suction line from the WW. Therefore, FP are scrubbed in the S/P at first and then vented into the filtered venting tank. After the DW suction line of the iPCCS is opened all the steam is cooled and condensed in the heat exchanger. Most FP are trapped in the condensate and returned into the WW through the condensate return line of the iPCCS. Therefore, the Mark W containment has excellent FP double confinement barriers and the in-containment filtered venting system that enable

Fluctuations and confinement in ATF

International Nuclear Information System (INIS)

Isler, R.C.; Harris, J.H.; Murakami, M.

1993-01-01

In the period immediately prior to the suspension of ATF operation in November, 1991, a great deal of emphasis was palced on investigations of the fundamental mechanisms controlling confinement in this device. At that time, measurements of the density fluctuations throughout the plasma volume indicated the existence of theoretically predicted dissipative trapped electron and resistive interchange instabilities. These identifications were supported by results of dynamic configuration scans of the magnetic fields during which the extent of the magnetic well, shear, and fraction of confined trapped particles were changed continuously. Interpretation of the data from these experiments has been an ongoing exercise. Most recently, analysis of discharges employing strong gas puffing to change density gradients and fluctuation levels have strengthened the view that dissipative trapped electron modes may be present but do not play a significant direct role in energy transport. The present paper summarizes the current understanding concerning the identification of instabilities and their relationship to confinement in ATF

Confinement and strings in MQCD

International Nuclear Information System (INIS)

Hanany, A.; Strassler, M.J.; Zaffaroni, A.

1998-01-01

We study aspects of confinement in the M-theory fivebrane version of QCD (MQCD). We show heavy quarks are confined in hadrons (which take the form of membrane-fivebrane bound states) for N=1 and softly broken N=2 SU(N) MQCD. We explore and clarify the transition from the exotic physics of the latter to the standard physics of the former. In particular, the many strings and quark-antiquark mesons found in N=2 field theory by Douglas and Shenker are reproduced. It is seen that in the N=1 limit all but one such meson disappears while all of the strings survive. The strings of softly broken N=2, N=1, and even non-supersymmetric SU(N) MQCD have a common ratio for their tensions as a function of the amount of flux they carry. We also comment on the almost BPS properties of the Douglas-Shenker strings and discuss the brane picture for monopole confinement on N=2 QCD Higgs branches. (orig.)

Critical quench dynamics in confined systems.

Science.gov (United States)

Collura, Mario; Karevski, Dragi

2010-05-21

We analyze the coherent quantum evolution of a many-particle system after slowly sweeping a power-law confining potential. The amplitude of the confining potential is varied in time along a power-law ramp such that the many-particle system finally reaches or crosses a critical point. Under this protocol we derive general scaling laws for the density of excitations created during the nonadiabatic sweep of the confining potential. It is found that the mean excitation density follows an algebraic law as a function of the sweeping rate with an exponent that depends on the space-time properties of the potential. We confirm our scaling laws by first order adiabatic calculation and exact results on the Ising quantum chain with a varying transverse field.

A novel method for estimating soil precompression stress from uniaxial confined compression tests

DEFF Research Database (Denmark)

Lamandé, Mathieu; Schjønning, Per; Labouriau, Rodrigo

2017-01-01

. Stress-strain curves were obtained by performing uniaxial, confined compression tests on undisturbed soil cores for three soil types at three soil water potentials. The new method performed better than the Gompertz fitting method in estimating precompression stress. The values of precompression stress...... obtained from the new method were linearly related to the maximum stress experienced by the soil samples prior to the uniaxial, confined compression test at each soil condition with a slope close to 1. Precompression stress determined with the new method was not related to soil type or dry bulk density......The concept of precompression stress is used for estimating soil strength of relevance to fieldtraffic. It represents the maximum stress experienced by the soil. The most recently developed fitting method to estimate precompression stress (Gompertz) is based on the assumption of an S-shape stress...

Enhancement of confinement in tokamaks

International Nuclear Information System (INIS)

Furth, H.P.

1986-05-01

A plausible interpretation of the experimental evidence is that energy confinement in tokamaks is governed by two separate considerations: (1) the need for resistive MHD kink-stability, which limits the permissible range of current profiles - and therefore normally also the range of temperature profiles; and (2) the presence of strongly anomalous microscopic energy transport near the plasma edge, which calibrates the amplitude of the global temperature profile, thus determining the energy confinement time tau/sub E/. Correspondingly, there are two main paths towards the enhancement of tokamak confinement: (1) Configurational optimization, to increase the MHD-stable energy content of the plasma core, can evidently be pursued by varying the cross-sectional shape of the plasma and/or finding stable radial profiles with central q-values substantially below unity - but crossing from ''first'' to ''second'' stability within the peak-pressure region would have the greatest ultimate potential. (2) Suppression of edge turbulence, so as to improve the heat insulation in the outer plasma shell, can be pursued by various local stabilizing techniques, such as use of a poloidal divertor. The present confinement model and initial TFTR pellet-injection results suggest that the introduction of a super-high-density region within the plasma core should be particularly valuable for enhancing ntau/subE/. In D-T operation, a centrally peaked plasma pressure profile could possibly lend itself to alpha-particle-driven entry into the second-stability regime

Fluorescence Microscopy of Nanochannel-Confined DNA.

Science.gov (United States)

Westerlund, Fredrik; Persson, Fredrik; Fritzsche, Joachim; Beech, Jason P; Tegenfeldt, Jonas O

2018-01-01

Stretching of DNA in nanoscale confinement allows for several important studies. The genetic contents of the DNA can be visualized on the single DNA molecule level and both the polymer physics of confined DNA and also DNA/protein and other DNA/DNA-binding molecule interactions can be explored. This chapter describes the basic steps to fabricate the nanostructures, perform the experiments and analyze the data.

Ground-water flow and saline water in the shallow aquifer system of the southern watersheds of Virginia Beach, Virginia

Science.gov (United States)

Smith, Barry S.

2003-01-01

Population and tourism continues to grow in Virginia Beach, Virginia, but the supply of freshwater is limited. A pipeline from Lake Gaston supplies water for northern Virginia Beach, but ground water is widely used to water lawns in the north, and most southern areas of the city rely solely on ground water. Water from depths greater than 60 meters generally is too saline to drink. Concentrations of chloride, iron, and manganese exceed drinking-water standards in some areas. The U.S. Geological Survey, in cooperation with the city of Virginia Beach, Department of Public Utilities, investigated the shallow aquifer system of the southern watersheds to determine the distribution of fresh ground water, its potential uses, and its susceptibility to contamination. Aquifers and confining units of the southern watersheds were delineated and chloride concentrations in the aquifers and confining units were contoured. A ground-water-flow and solute-transport model of the shallow aquifer system reached steady state with regard to measured chloride concentrations after 31,550 years of freshwater recharge. Model simulations indicate that if freshwater is found in permeable sediments of the Yorktown-Eastover aquifer, such a well field could supply freshwater, possibly for decades, but eventually the water would become more saline. The rate of saline-water intrusion toward the well field would depend on the rate of pumping, aquifer properties, and on the proximity of the well field to saline water sources. The steady-state, ground-water-flow model also was used to simulate drawdowns around two hypothetical well fields and drawdowns around two hypothetical open-pit mines. The chloride concentrations simulated in the model did not approximate the measured concentrations for some wells, indicating sites where local hydrogeologic units or unit properties do not conform to the simple hydrogeology of the model. The Columbia aquifer, the Yorktown confining unit, and the Yorktown

Behaviour of FRP confined concrete in square columns

OpenAIRE

Diego Villalón, Ana de; Arteaga Iriarte, Ángel; Fernandez Gomez, Jaime Antonio; Perera Velamazán, Ricardo; Cisneros, Daniel

2015-01-01

A significant amount of research has been conducted on FRP-confined circular columns, but much less is known about rectangular/square columns in which the effectiveness of confinement is much reduced. This paper presents the results of experimental investigations on low strength square concrete columns confined with FRP. Axial compression tests were performed on ten intermediate size columns. The tests results indicate that FRP composites can significantly improve the bearing capacity and duc...

Hermitian relativity, chromodynamics and confinement

International Nuclear Information System (INIS)

Treder, H.J.

1983-01-01

The extension of the Riemann metrics of General Relativity to the complex domain (substitution of the symmetry conditions for the fundamental tensor, the affinity and the Ricci curvature by the conditions of hermicity) leads to a 'Generalized Theory of Gravity' (Einstein) describing the Newton-Einstein gravodynamics combined with the chromodynamics of quarks. The interaction of gravodynamics and chromodynamics implied by the Einstein-Schroedinger field equations of the hermitian relativity theory enforces the 'confinement'. The 'confinement' prevents the gravitational potential from divergence which would result in the lack of a Riemann space-time metric

Finite temperature approach to confinement

International Nuclear Information System (INIS)

Gave, E.; Jengo, R.; Omero, C.

1980-06-01

The finite temperature treatment of gauge theories, formulated in terms of a gauge invariant variable as in a Polyakov method, is used as a device for obtaining an effective theory where the confinement test takes the form of a correlation function. The formalism is discussed for the abelian CPsup(n-1) model in various dimensionalities and for the pure Yang-Mills theory in the limit of zero temperature. In the latter case a class of vortex like configurations of the effective theory which induce confinement correspond in particular to the instanton solutions. (author)

Pellet injection and toroidal confinement

International Nuclear Information System (INIS)

1989-12-01

The proceedings of a technical committee meeting on pellet injection and toroidal confinement, held in Gut Ising, Federal Republic of Germany, 24-26 October, 1988, are given in this report. Most of the major fusion experiments are using pellet injectors; these were reported at this meeting. Studies of confinement, which is favorably affected, impurity transport, radiative energy losses, and affects on the ion temperature gradient instability were given. Studies of pellet ablation and effects on plasma profiles were presented. Finally, several papers described present and proposed injection guns. Refs, figs and tabs

INERT Atmosphere confinement operability test procedure

International Nuclear Information System (INIS)

RISENMAY, H.R.

1999-01-01

This Operability Test Procedure (OTP) provides instructions for testing operability of the Inert Atmosphere Confinement (IAC). The Inert Atmosphere Confinement was designed and built for opening cans of metal items that might have hydrided surfaces. Unreviewed Safety Question (USQ) PFP-97-005 addresses the discovery of suspected plutonium hydride forming on plutonium metal currently stored in the Plutonium Finishing Plant vaults. Plutonium hydride reacts quickly with air, liberating energy. The Inert Atmosphere Confinement was designed to prevent this sudden liberation of energy by opening the material in an inert argon atmosphere instead of the normal glovebox atmosphere. The IAC is located in glovebox HC-21A, room 230B of the 234-5Z Building at the Plutonium Finishing Plant (PFP) in the 200-West Area of the Hanford Site

Anomalous response of supported few-layer hexagonal boron nitride to DC electric fields: a confined water effect?

Science.gov (United States)

Oliveira, Camilla; Matos, Matheus; Mazzoni, Mário; Chacham, Hélio; Neves, Bernardo

2013-03-01

Hexagonal boron nitride (h-BN) is a two-dimensional compound from III-V family, with the atoms of boron and nitrogen arranged in a honeycomb lattice, similar to graphene. Unlike graphene though, h-BN is an insulator material, with a gap larger than 5 eV. Here, we use Electric Force Microscopy (EFM) to study the electrical response of mono and few-layers of h-BN to an electric field applied by the EFM tip. Our results show an anomalous behavior in the dielectric response for h-BN for different bias orientation: for a positive bias applied to the tip, h-BN layers respond with a larger dielectric constant than the dielectric constant of the silicon dioxide substrate; while for a negative bias, the h-BN dielectric constant is smaller than the dielectric constant of the substrate. Based on first-principles calculations, we showed that this anomalous response may be interpreted as a macroscopic consequence of confinement of a thin water layer between h-BN and substrate. These results were confirmed by sample annealing and also also by a comparative analysis with h-BN on a non-polar substrate. All the authors acknowledge financial support from CNPq, Fapemig, Rede Nacional de Pesquisa em Nanotubos de Carbono and INCT-Nano-Carbono.

Deep processes in non-relativistic confining potentials

International Nuclear Information System (INIS)

Fishbane, P.M.; Grisaru, M.T.

1978-01-01

The authors study deep inelastic and hard scattering processes for non-relativistic particles confined in deep potentials. The mechanisms by which the effects of confinement disappear and the particles scatter as if free are useful in understanding the analogous results for a relativistic field theory. (Auth.)

Potential Role of Inorganic Confined Environments in Prebiotic Phosphorylation.

Science.gov (United States)

Dass, Avinash Vicholous; Jaber, Maguy; Brack, André; Foucher, Frédéric; Kee, Terence P; Georgelin, Thomas; Westall, Frances

2018-03-05

A concise outlook on the potential role of confinement in phosphorylation and phosphate condensation pertaining to prebiotic chemistry is presented. Inorganic confinement is a relatively uncharted domain in studies concerning prebiotic chemistry, and even more so in terms of experimentation. However, molecular crowding within confined dimensions is central to the functioning of contemporary biology. There are numerous advantages to confined environments and an attempt to highlight this fact, within this article, has been undertaken, keeping in context the limitations of aqueous phase chemistry in phosphorylation and, to a certain extent, traditional approaches in prebiotic chemistry.

Interaction between confined phonons and photons in periodic silicon resonators

Science.gov (United States)

Iskandar, A.; Gwiazda, A.; Younes, J.; Kazan, M.; Bruyant, A.; Tabbal, M.; Lerondel, G.

2018-03-01

In this paper, we demonstrate that phonons and photons of different momenta can be confined and interact with each other within the same nanostructure. The interaction between confined phonons and confined photons in silicon resonator arrays is observed by means of Raman scattering. The Raman spectra from large arrays of dielectric silicon resonators exhibited Raman enhancement accompanied with a downshift and broadening. The analysis of the Raman intensity and line shape using finite-difference time-domain simulations and a spatial correlation model demonstrated an interaction between photons confined in the resonators and phonons confined in highly defective regions prompted by the structuring process. It was shown that the Raman enhancement is due to collective lattice resonance inducing field confinement in the resonators, while the spectra downshift and broadening are signatures of the relaxation of the phonon wave vector due to phonon confinement in defective regions located in the surface layer of the Si resonators. We found that as the resonators increase in height and their shape becomes cylindrical, the amplitude of their coherent oscillation increases and hence their ability to confine the incoming electric field increases.

Improved confinement in L-mode JET plasmas

International Nuclear Information System (INIS)

Jones, T.T.C.; Balet, B.; Bhatnagar, V.; Bures, M.; Campbell, D.J.; Christiansen, J.P.; Cordey, J.G.; Core, W.F.; Corti, S.; Costley, A.E.; Cottrell, G.A.; Edwards, A.; Ehrenberg, J.; Jacquinot, J.; Lallia, P.; Lomas, P.J.; Lowry, C.; Malacarne, M.; Muir, D.G.; Nave, M.F.; Nielsen, P.; Sack, C.; Sadler, G.; Start, D.F.H.; Taroni, A.; Thomas, P.R.; Thomsen, K.

1989-01-01

The JET confinement data show considerable variations of stored plasma energy W (thermal + fast ions) at fixed input power P, plasma current I, toroidal field B and plasma configuration C. The data on confinement properties, e.g. the confinement time τ E or its incremental value τ E (inc), derived from variations of P at fixed I, B, C thus exhibit scatter which makes the scaling of τ E with P, I, B, C difficult to establish. The effects from sawteeth, from variations in the power deposition profiles and from plasma edge physics on confinement do not depend on P, I, B, C in any simple way which would permit a deduced scaling law to be identified with a single (or more) physics loss mechanism(s). In this paper we examine the response of confinement to variations in plasma configuration at fixed I and B (3 MA and 3 T). Results from global and local transport analysis are discussed in sections 2 and 3; section 4 describes the role of fast ions produced by ICRF and NBI heating. High confinement in the L-mode regime at increased plasma currents up to 6 MA is also studied, in particular the effects from sawteeth on stored energy W. Such effects increase with current and presently only predictive transport studies (section 5) can estimate what may be achieved at high current without sawteeth effects. The predictive studies also assess the benefits which may arise from an increase of the neutral beam energy at high plasma currents (section 6). The conclusions are based on extensive study of data from JET pulses with up to 14 MW of ICRH, 21 MW of NBI and 6 MW of ohmic power. None of the pulses included in the study show the sudden reduction of D α emission characteristic of the L to H mode transition of confinement. 7 refs., 4 figs

Ground-Water Flow Direction, Water Quality, Recharge Sources, and Age, Great Sand Dunes National Monument, South-Central Colorado, 2000-2001

Science.gov (United States)

Rupert, Michael G.; Plummer, Niel

2004-01-01

Great Sand Dunes National Monument is located in south-central Colorado along the eastern edge of the San Luis Valley. The Great Sand Dunes National Monument contains the tallest sand dunes in North America; some rise up to750 feet. Important ecological features of the Great Sand Dunes National Monument are palustrine wetlands associated with interdunal ponds and depressions along the western edge of the dune field. The existence and natural maintenance of the dune field and the interdunal ponds are dependent on maintaining ground-water levels at historic elevations. To address these concerns, the U.S. Geological Survey conducted a study, in collaboration with the National Park Service, of ground-water flow direction, water quality, recharge sources, and age at the Great Sand Dunes National Monument. A shallow unconfined aquifer and a deeper confined aquifer are the two principal aquifers at the Great Sand Dunes National Monument. Ground water in the unconfined aquifer is recharged from Medano and Sand Creeks near the Sangre de Cristo Mountain front, flows underneath the main dune field, and discharges to Big and Little Spring Creeks. The percentage of calcium in ground water in the unconfined aquifer decreases and the percentage of sodium increases because of ionic exchange with clay minerals as the ground water flows underneath the dune field. It takes more than 60 years for the ground water to flow from Medano and Sand Creeks to Big and Little Spring Creeks. During this time, ground water in the upper part of the unconfined aquifer is recharged by numerous precipitation events. Evaporation of precipitation during recharge prior to reaching the water table causes enrichment in deuterium (2H) and oxygen-18 (18O) relative to waters that are not evaporated. This recharge from precipitation events causes the apparent ages determined using chlorofluorocarbons and tritium to become younger, because relatively young precipitation water is mixing with older waters

Qualitative quark confinement

International Nuclear Information System (INIS)

Jackson, T.L.

1976-01-01

The infrared limit in asymptotically free non-abelian gauge theories using recently developed non-perturbative methods which allow derivation of zero momentum theorems for Green's functions and vertices is described. These low-energy theorems are compared to the infrared behavior predicted from the renormalization group equation when the existence of an infrared fixed point is assumed. A set of objects is exhibited whose low energy theorems violate the scaling behavior predicted by the renormalization group. This shows that the assumed fixed point cannot exist and that in the Landau gauge the effective charge becomes infinite in the infrared. Qualitatively this implies that as an attempt is made to separate elementary quanta the interaction between the quanta becomes arbitrarily strong. This indicates at least that the theories studied are capable of color confinement. Results are true only for theories with large numbers of quarks. This opens the possibility that large numbers of quarks are actually necessary for confinement

Greater-confinement disposal

International Nuclear Information System (INIS)

Trevorrow, L.E.; Schubert, J.P.

1989-01-01

Greater-confinement disposal (GCD) is a general term for low-level waste (LLW) disposal technologies that employ natural and/or engineered barriers and provide a degree of confinement greater than that of shallow-land burial (SLB) but possibly less than that of a geologic repository. Thus GCD is associated with lower risk/hazard ratios than SLB. Although any number of disposal technologies might satisfy the definition of GCD, eight have been selected for consideration in this discussion. These technologies include: (1) earth-covered tumuli, (2) concrete structures, both above and below grade, (3) deep trenches, (4) augered shafts, (5) rock cavities, (6) abandoned mines, (7) high-integrity containers, and (8) hydrofracture. Each of these technologies employ several operations that are mature,however, some are at more advanced stages of development and demonstration than others. Each is defined and further described by information on design, advantages and disadvantages, special equipment requirements, and characteristic operations such as construction, waste emplacement, and closure

Stellarator approach to toroidal plasma confinement

International Nuclear Information System (INIS)

Johnson, J.L.

1981-12-01

An overview is presented of the development and current status of the stellarator approach to controlled thermonuclear confinement. Recent experimental, theoretical, and systems developments have made this concept a viable option for the evolution of the toroidal confinement program. Some experimental study of specific problems associated with departure from two-dimensional symmetry must be undertaken before the full advantages and opportunities of steady-state, net-current-free operation can be realized

Soft matter in hard confinement: phase transition thermodynamics, structure, texture, diffusion and flow in nanoporous media

Science.gov (United States)

Huber, Patrick

2015-03-01

Spatial confinement in nanoporous media affects the structure, thermodynamics and mobility of molecular soft matter often markedly. This article reviews thermodynamic equilibrium phenomena, such as physisorption, capillary condensation, crystallisation, self-diffusion, and structural phase transitions as well as selected aspects of the emerging field of spatially confined, non-equilibrium physics, i.e. the rheology of liquids, capillarity-driven flow phenomena, and imbibition front broadening in nanoporous materials. The observations in the nanoscale systems are related to the corresponding bulk phenomenologies. The complexity of the confined molecular species is varied from simple building blocks, like noble gas atoms, normal alkanes and alcohols to liquid crystals, polymers, ionic liquids, proteins and water. Mostly, experiments with mesoporous solids of alumina, gold, carbon, silica, and silicon with pore diameters ranging from a few up to 50 nm are presented. The observed peculiarities of nanopore-confined condensed matter are also discussed with regard to applications. A particular emphasis is put on texture formation upon crystallisation in nanoporous media, a topic both of high fundamental interest and of increasing nanotechnological importance, e.g. for the synthesis of organic/inorganic hybrid materials by melt infiltration, the usage of nanoporous solids in crystal nucleation or in template-assisted electrochemical deposition of nano structures.

Single Pt Atoms Confined into a Metal-Organic Framework for Efficient Photocatalysis.

Science.gov (United States)

Fang, Xinzuo; Shang, Qichao; Wang, Yu; Jiao, Long; Yao, Tao; Li, Yafei; Zhang, Qun; Luo, Yi; Jiang, Hai-Long

2018-02-01

It is highly desirable yet remains challenging to improve the dispersion and usage of noble metal cocatalysts, beneficial to charge transfer in photocatalysis. Herein, for the first time, single Pt atoms are successfully confined into a metal-organic framework (MOF), in which electrons transfer from the MOF photosensitizer to the Pt acceptor for hydrogen production by water splitting under visible-light irradiation. Remarkably, the single Pt atoms exhibit a superb activity, giving a turnover frequency of 35 h -1 , ≈30 times that of Pt nanoparticles stabilized by the same MOF. Ultrafast transient absorption spectroscopy further unveils that the single Pt atoms confined into the MOF provide highly efficient electron transfer channels and density functional theory calculations indicate that the introduction of single Pt atoms into the MOF improves the hydrogen binding energy, thus greatly boosting the photocatalytic H 2 production activity. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Curvature of random walks and random polygons in confinement

International Nuclear Information System (INIS)

Diao, Y; Ernst, C; Montemayor, A; Ziegler, U

2013-01-01

The purpose of this paper is to study the curvature of equilateral random walks and polygons that are confined in a sphere. Curvature is one of several basic geometric properties that can be used to describe random walks and polygons. We show that confinement affects curvature quite strongly, and in the limit case where the confinement diameter equals the edge length the unconfined expected curvature value doubles from π/2 to π. To study curvature a simple model of an equilateral random walk in spherical confinement in dimensions 2 and 3 is introduced. For this simple model we derive explicit integral expressions for the expected value of the total curvature in both dimensions. These expressions are functions that depend only on the radius R of the confinement sphere. We then show that the values obtained by numeric integration of these expressions agrees with numerical average curvature estimates obtained from simulations of random walks. Finally, we compare the confinement effect on curvature of random walks with random polygons. (paper)

Hydrochemistry and hydrogeologic conditions within the Hanford Site upper basalt confined aquifer system

International Nuclear Information System (INIS)

Spane, F.A. Jr.; Webber, W.D.

1995-09-01

As part of the Hanford Site Ground-Water Surveillance Project, Flow System Characterization Task. Pacific Northwest Laboratory examines the potential for offsite migration of contamination within the upper basalt confined aquifer system for the US Department of Energy (DOE). As part of this activity, groundwater samples were collected over the past 2 years from selected wells completed in the upper Saddle Mountains Basalt. The hydrochemical and isotopic information obtained from these groundwater samples provides hydrologic information concerning the aquifer-flow system. Ideally, when combined with other hydrologic property information, hydrochemical and isotopic data can be used to evaluate the origin and source of groundwater, areal groundwater-flow patterns, residence and groundwater travel time, rock/groundwater reactions, and aquifer intercommunication for the upper basalt confined aquifer system. This report presents the first comprehensive Hanford Site-wide summary of hydrochemical properties for the upper basalt confined aquifer system. This report provides the hydrogeologic characteristics (Section 2.0) and hydrochemical properties (Section 3.0) for groundwater within this system. A detailed description of the range of the identified hydrochemical parameter subgroups for groundwater in the upper basalt confined aquifer system is also presented in Section 3.0. Evidence that is indicative of aquifer contamination/aquifer intercommunication and an assessment of the potential for offsite migration of contaminants in groundwater within the upper basalt aquifer is provided in Section 4.0. The references cited throughout the report are given in Section 5.0. Tables that summarize groundwater sample analysis results for individual test interval/well sites are included in the Appendix

Water on graphene surfaces

Energy Technology Data Exchange (ETDEWEB)

Gordillo, M C [Departamento de Sistemas Fisicos, Quimicos y Naturales, Facultad de Ciencias Experimentales, Universidad Pablo de Olavide, Carretera de Utrera, km 1, E-41013 Sevilla (Spain); Marti, J, E-mail: cgorbar@upo.e, E-mail: jordi.marti@upc.ed [Departament de Fisica i Enginyeria Nuclear, Universitat Politecnica de Catalunya, B4-B5 Campus Nord, E-08034 Barcelona, Catalonia (Spain)

2010-07-21

In this paper, we summarize the main results obtained in our group about the behavior of water confined inside or close to different graphene surfaces by means of molecular dynamics simulations. These include the inside and outside of carbon nanotubes, and the confinement inside a slit pore or a single graphene sheet. We paid special attention to some thermodynamical (binding energies), structural (hydrogen-bond distributions) and dynamic (infrared spectra) properties, and their comparison to their bulk counterparts.

Percolating cluster of center vortices and confinement

International Nuclear Information System (INIS)

Gliozzi, Ferdinando; Panero, Marco; Provero, Paolo

2003-01-01

We study the role of percolating clusters of center vortices in configurations of an Ising gauge theory in 3D. It is known that low energy features of gauge theories can be described in terms of an 'effective string picture', and that confinement properties are associated with topologically non-trivial configurations. We focus our attention upon percolating clusters of center vortices, and present numerical evidence for the fact that these objects play a preminent role in confinement phenomenon, since their removal sweeps off confinement altogether. Moreover, numerical simulations show that the string fluctuations, and in particular the Mischer term, are completely encoded in the percolating cluster

Laser drivers for inertial confinement fusion

International Nuclear Information System (INIS)

Holzrichter, J.F.

1983-01-01

Inertial Confinement Fusion (ICF) is the technology that we are developing to access the vast stored energy potential of deuterium fuel located in the world's water supply. This form of fusion is accomplished by compressing and heating small volumes of D-T fuel to very high temperatures (greater than 100M 0 C) and to very high densities (greater than 1000 times the normal liquid density). Under these fuel conditions, a thermonuclear reaction can occur, leading to a net energy release compared to the energy used to heat the fuel initially. To accomplish the condition where fusion reactions begin, effective drivers are required. These are lasers or particle beam accelerators which can provide greater than 10 14 W/cm 2 over millimeter scale targets with an appropriately programmed intensity vs time. At present, we are using research lasers to obtain an understanding of the physics and engineering of fuel compression

FRP-Confined Recycled Coarse Aggregate Concrete: Experimental Investigation and Model Comparison

Directory of Open Access Journals (Sweden)

Yingwu Zhou

2016-10-01

Full Text Available The in situ application of recycled aggregate concrete (RAC is of great significance in environmental protection and construction resources sustainability. However, it has been limited to nonstructural purposes due to its poor mechanical performance. External confinement using steel tubes and fiber-reinforced polymer (FRP can significantly improve the mechanical performance of RAC and thus the first-ever study on the axial compressive behavior of glass FRP (GFRP-confined RAC was recently reported. To have a full understanding of FRP-confined RAC, this paper has extended the type of FRP and presents a systematic experimental study on the axial compressive performance of carbon FRP (CFRP-confined RAC. The mechanical properties of CFRP-confined RAC from the perspective of the failure mode, ultimate strength and strain, and stress–strain relationship responses were analyzed. Integrated with existing experimental data of FRP-confined RAC, the paper compiles a database for the mechanical properties of FRP-confined RAC. Based on the database, the effects of FRP type (i.e., GFRP and CFRP and the replacement ratio of recycled coarse aggregate were investigated. The results indicated that the stress–stain behavior of FRP-confined RAC depended heavily on the unconfined concrete strength and the FRP confining pressure instead of the replacement ratio. Therefore, this study adopted eleven high-performance ultimate strength and strain models developed for FRP-confined normal aggregate concrete (NAC to predict the mechanical properties of FRP-confined RAC. All the predictions had good agreement with the test results, which further confirmed similar roles played by FRP confinement in improving the mechanical properties of RAC and improving those of NAC. On this basis, this paper finally recommended a stress–strain relationship model for FRP-confined RAC.

Structure and spectra of a confined HeH molecule

International Nuclear Information System (INIS)

Lo, J M H; Klobukowski, M; Bielinska-Wacz, D; Schreiner, E W S; Diercksen, G H F

2006-01-01

The influence of spatial confinement on the structure and spectra of the Rydberg HeH molecule is analysed at the level of the variational full configuration interaction approach. The confining potential is assumed to have cylindrical symmetry, with the symmetry axis of the potential overlapping with the molecular bond. In the direction perpendicular to the axis quadratic dependence of the potential on the electron coordinates is assumed. The influence of the confining potential on the form of the potential energy curves (in particular on the bond lengths), on the electronic spectra and on the ionization due to the confinement is studied in detail

The cruel and unusual phenomenology of solitary confinement

OpenAIRE

Shaun eGallagher; Shaun eGallagher; Shaun eGallagher

2014-01-01

What happens when subjects are deprived of intersubjective contact? This paper looks closely at the phenomenology and psychology of one example of that deprivation: solitary confinement. It also puts the phenomenology and psychology of solitary confinement to use in the legal context. Not only is there no consensus on whether solitary confinement is a cruel and unusual punishment, there is no consensus on the definition of the term ‘cruel’ in the use of that legal phrase. I argue that we ...

Masonry Columns Confined by Steel Fiber Composite Wraps

Directory of Open Access Journals (Sweden)

Marco Corradi

2011-01-01

Full Text Available The application of steel fiber reinforced polymer (SRP as a means of increasing the capacity of masonry columns is investigated in this study. The behavior of 23 solid-brick specimens that are externally wrapped by SRP sheets in low volumetric ratios is presented. The specimens are subjected to axial monotonic load until failure occurs. Two widely used types of masonry columns of differing square cross-sections were tested in compression (square and octagonal cross-sections. It is concluded that SRP-confined masonry behaves very much like fiber reinforced polymers (FRP-confined masonry. Confinement increases both the load-carrying capacity and the deformability of masonry almost linearly with average confining stress. A comparative analysis between experimental and theoretical values computed in compliance with the Italian Council of Research (CNR was also developed.

Confined catalysis under two-dimensional materials

OpenAIRE

Li, Haobo; Xiao, Jianping; Fu, Qiang; Bao, Xinhe

2017-01-01

Small spaces in nanoreactors may have big implications in chemistry, because the chemical nature of molecules and reactions within the nanospaces can be changed significantly due to the nanoconfinement effect. Two-dimensional (2D) nanoreactor formed under 2D materials can provide a well-defined model system to explore the confined catalysis. We demonstrate a general tendency for weakened surface adsorption under the confinement of graphene overlayer, illustrating the feasible modulation of su...

Chiral symmetry breaking and confinement - solutions of relativistic wave equations

International Nuclear Information System (INIS)

Murugesan, P.

1983-01-01

In this thesis, an attempt is made to explore the question whether confinement automatically leads to chiral symmetry breaking. While it should be accepted that chiral symmetry breaking manifests in nature in the absence of scalar partners of pseudoscalar mesons, it does not necessarily follow that confinement should lead to chiral symmetry breaking. If chiral conserving forces give rise to observed spectrum of hadrons, then the conjuncture that confinement is responsible for chiral symmetry breaking is not valid. The method employed to answer the question whether confinement leads to chiral symmetry breaking or not is to solve relativistic wave equations by introducing chiral conserving as well as chiral breaking confining potentials and compare the results with experimental observations. It is concluded that even though chiral symmetry is broken in nature, confinement of quarks need not be the cause of it

Shearing of saturated clays in rock joints at high confining pressures

International Nuclear Information System (INIS)

Wang, C.; Mao, N.

1979-01-01

Saturated clays are sheared between rock joints at various pore water pressures and at confining pressures up to 3 kb (300 Mpa). Sliding on these joints is stable. For a given clay, the shear stress required to initiate sliding increases linearly with the effective normal stress across the sliding surface, with a slope of 0.08 +- 0.01 for joints filled with saturated montmorillonite, 0.12 +- 0.01 with saturated chlorite, 0.15 +- 0.01 with saturated kaolinite, and 0.22 +- 0.02 with saturated silty illite. Thus at high confining pressures the shear stress required to initiate sliding on joints filled with saturated clays are very much smaller than that required to initiate sliding on clean rock joints or on joints filled with dry gouge materials. In the crust, saturation of gouge materials along active faults would greatly lower the frictional resistance to faulting and would stabilize fault movement. Different fault behaviors such as stable creep along some faults and intermittent but sudden slip along others may reflect in part different degrees of saturation of fault zones at depth

CONFINEMENT OF HIGH TEMPERATURE PLASMA

Science.gov (United States)

Koenig, H.R.

1963-05-01

The confinement of a high temperature plasma in a stellarator in which the magnetic confinement has tended to shift the plasma from the center of the curved, U-shaped end loops is described. Magnetic means are provided for counteracting this tendency of the plasma to be shifted away from the center of the end loops, and in one embodiment this magnetic means is a longitudinally extending magnetic field such as is provided by two sets of parallel conductors bent to follow the U-shaped curvature of the end loops and energized oppositely on the inside and outside of this curvature. (AEC)

Water supply in the long term: a risk assessment

NARCIS (Netherlands)

Hoekstra, Arjen Ysbert

2000-01-01

Integrated water assessment studies are often confined to a study of physical aspects, considering the relation between surface and groundwater, water quantity and water quality, and between water, land and climate. The interaction between changes in the water system and socio-economic development

The cruel and unusual phenomenology of solitary confinement

OpenAIRE

Gallagher, Shaun

2014-01-01

What happens when subjects are deprived of intersubjective contact? This paper looks closely at the phenomenology and psychology of one example of that deprivation: solitary confinement. It also puts the phenomenology and psychology of solitary confinement to use in the legal context. Not only is there no consensus on whether solitary confinement is a “cruel and unusual punishment,” there is no consensus on the definition of the term “cruel” in the use of that legal phrase. I argue that we ca...

Measurement of suprathermal electron confinement by cyclotron transmission

International Nuclear Information System (INIS)

Kirkwood, R.; Hutchinson, I.H.; Luckhardt, S.C.; Porkolab, M.; Squire, J.P.

1990-01-01

The confinement time of suprathermal electrons is determined experimentally from the distribution function determined via wave transmission measurements. Measurements of the lowest moment of the distribution perpendicular to the B field as a function of the parallel electron momentum as well as the global input power allow the suprathermal electron confinement time (τ se ) to be calculated during lower-hybrid and inductive current drive. Finite particle confinement is found to be the dominant energy loss term for the suprathermals and improves with plasma current and density

Search for the first-order liquid-to-liquid phase transition in low-temperature confined water by neutron scattering

Science.gov (United States)

Chen, Sow-Hsin; Wang, Zhe; Kolesnikov, Alexander I.; Zhang, Yang; Liu, Kao-Hsiang

2013-02-01

It has been conjectured that a 1st order liquid-to-liquid (L-L) phase transition (LLPT) between high density liquid (HDL) and low density liquid (LDL) in supercooled water may exist, as a thermodynamic extension to the liquid phase of the 1st order transition established between the two bulk solid phases of amorphous ice, the high density amorphous ice (HDA) and the low density amorphous ice (LDA). In this paper, we first recall our previous attempts to establish the existence of the 1st order L-L phase transition through the use of two neutron scattering techniques: a constant Q elastic diffraction study of isobaric temperature scan of the D2O density, namely, the equation of state (EOS) measurements. A pronounced density hysteresis phenomenon in the temperature scan of the density above P = 1500 bar is observed which gives a plausible evidence of crossing the 1st order L-L phase transition line above this pressure; an incoherent quasi-elastic scattering measurements of temperature-dependence of the α-relaxation time of H2O at a series of pressures, namely, the study of the Fragile-to-Strong dynamic crossover (FSC) phenomenon as a function of pressure which we interpreted as the results of crossing the Widom line in the one-phase region. In this new experiment, we used incoherent inelastic neutron scattering (INS) to measure the density of states (DOS) of H atoms in H2O molecules in confined water as function of temperature and pressure, through which we may be able to follow the emergence of the LDL and HDL phases at supercooled temperature and high pressures. We here report for the first time the differences of librational and translational DOSs between the hypothetical HDL and LDL phases, which are similar to the corresponding differences between the well-established HDA and LDA ices. This is plausible evidence that the HDL and LDL phases are the thermodynamic extensions of the corresponding amorphous solid water HDA and LDA ices.

Electrostatically confined quantum rings in bilayer graphene.

Science.gov (United States)

Zarenia, M; Pereira, J M; Peeters, F M; Farias, G A

2009-12-01

We propose a new system where electron and hole states are electrostatically confined into a quantum ring in bilayer graphene. These structures can be created by tuning the gap of the graphene bilayer using nanostructured gates or by position-dependent doping. The energy levels have a magnetic field (B(0)) dependence that is strikingly distinct from that of usual semiconductor quantum rings. In particular, the eigenvalues are not invariant under a B(0) --> -B(0) transformation and, for a fixed total angular momentum index m, their field dependence is not parabolic, but displays two minima separated by a saddle point. The spectra also display several anticrossings, which arise due to the overlap of gate-confined and magnetically confined states.

Holographic repulsion and confinement in gauge theory

Science.gov (United States)

Husain, Viqar; Kothawala, Dawood

2013-02-01

We show that for asymptotically anti-de Sitter (AdS) backgrounds with negative energy, such as the AdS soliton and regulated negative-mass AdS-Schwarzshild metrics, the Wilson loop expectation value in the AdS/CFT conjecture exhibits a Coulomb to confinement transition. We also show that the quark-antiquark (q \\bar{q}) potential can be interpreted as affine time along null geodesics on the minimal string worldsheet and that its intrinsic curvature provides a signature of transition to confinement phase. Our results suggest a generic (holographic) relationship between confinement in gauge theory and repulsive gravity, which in turn is connected with singularity avoidance in quantum gravity. Communicated by P R L V Moniz

Progress in toroidal confinement and fusion research

International Nuclear Information System (INIS)

Furth, H.P.

1987-10-01

During the past 30 years, the characteristic T/sub i/n tau/sub E/-value of toroidal-confinement experiments has advanced by more than seven orders of magnitude. Part of this advance has been due to an increase of gross machine parameters. Most of this advance has been due to an increase of gross machine parameters. Most of the advance is associated with improvements in the ''quality of plasma confinement.'' The combined evidence of spherator and tokamak research clarifies the role of magnetic-field geometry in determining confinement and points to the importance of shielding out plasma edge effects. A true physical understanding of anomalous transport remains to be achieved. 39 refs., 11 figs., 1 tab

Theory of plasma confinement in non-axisymmetric magnetic fields.

Science.gov (United States)

Helander, Per

2014-08-01

The theory of plasma confinement by non-axisymmetric magnetic fields is reviewed. Such fields are used to confine fusion plasmas in stellarators, where in contrast to tokamaks and reversed-field pinches the magnetic field generally does not possess any continuous symmetry. The discussion is focussed on magnetohydrodynamic equilibrium conditions, collisionless particle orbits, and the kinetic theory of equilbrium and transport. Each of these topics is fundamentally affected by the absence of symmetry in the magnetic field: the field lines need not trace out nested flux surfaces, the particle orbits may not be confined, and the cross-field transport can be very large. Nevertheless, by tailoring the magnetic field appropriately, well-behaved equilibria with good confinement can be constructed, potentially offering an attractive route to magnetic fusion. In this article, the mathematical apparatus to describe stellarator plasmas is developed from first principles and basic elements underlying confinement optimization are introduced.

Probing the conformational dynamics of photosystem I in unconfined and confined spaces.

Science.gov (United States)

Das, Gaurav; Chattoraj, Shyamtanu; Nandi, Somen; Mondal, Prasenjit; Saha, Abhijit; Bhattacharyya, Kankan; Ghosh, Surajit

2017-12-20

The fluorescence dynamics of Photosystem I (PSI) in bulk water and inside a confined environment like a liposome have been investigated using time resolved confocal microscopy. In bulk water, PSI exhibits a major emission peak at ∼680 nm, while in the liposome it exhibits a markedly blue shifted emission maximum at ∼485 nm. This is indicative of conformational changes due to entrapment and emergence of a stressed conformation of PSI inside the liposome. The observed time constants for the fluorescence lifetime of PSI inside the liposome are significantly high as opposed to PSI in bulk water. More interestingly, the fluorescence intensity of PSI in bulk water exhibits strong fluctuations with many high intensity jumps and these are anti-correlated with the fluorescence lifetime of PSI. In contrast, inside the liposome, no such anti-correlated behaviour is observed. We further demonstrated that PSI exhibits at least two conformational states in bulk water, whereas a single conformation is observed inside the liposome, indicating the conformational rigidity and locking of the PSI complex inside a liposome.

Particle-confinement criteria for axisymmetric field-reversed magnetic configurations

International Nuclear Information System (INIS)

Hsiao, M.Y.; Miley, G.H.

1984-01-01

Based on two constants of motion, H and Psub(theta), where H is the total energy of a particle and Psub(theta) is its canonical angular momentum, particle confinement criteria are derived which impose constraints on H and Psub(theta). With no electric field at the ends of field-reversed magnetic configurations, confinement criteria for closed-field and absolute confinements are obtained explicitly, including both lower and upper bounds of Psub(theta)/q, where q is the charge of the species considered, for a class of Hill's vortex field-reversed magnetic configurations. The commonly used criterion for the Hamiltonian, H 0 Psub(theta), where ω 0 is identical to qB 0 /mc, is deduced from a more general form as a special case. In this special case, it is found necessary to impose a new criterion, -B 0 R 2 sub(w)/2c 0 is the vacuum field, which reduces the confinement region in (H,Psub(theta)) space. With the presence of electric fields at the ends of field-reversed magnetic configurations, confinement criteria are obtained for two interesting cases. In addition to lower and upper bounds of H, both lower and upper bounds of Psub(theta)/q are found. For axially confined particles, the lower bound of Psub(theta)/q reduces the confinement region in (H,Psub(theta)) space and represents a new criterion. These results can be applied to calculations for field-reversed mirrors and field-reversed theta pinches. (author)

Quantum-confined nanowires as vehicles for enhanced electrical transport

International Nuclear Information System (INIS)

Mohammad, S Noor

2012-01-01

Electrical transport in semiconductor nanowires taking quantum confinement and dielectric confinement into account has been studied. A distinctly new route has been employed for the study. The fundamental science underlying the model is based on a relationship between the quantum confinement and the structural disorder of the nanowire surface. The role of surface energy and thermodynamic imbalance in nanowire structural disorder has been described. A model for the diameter dependence of energy bandgap of nanowires has been developed. Ionized impurity scattering, dislocation scattering and acoustic phonon scattering have been taken into account to study carrier mobility. A series of calculations on silicon nanowires show that carrier mobility in nanowires can be greatly enhanced by quantum confinement and dielectric confinement. The electron mobility can, for example, be a factor of 2–10 higher at room temperature than the mobility in a free-standing silicon nanowire. The calculated results agree well with almost all experimental and theoretical results available in the literature. They successfully explain experimental observations not understood before. The model is general and applicable to nanowires from all possible semiconductors. It is perhaps the first physical model highlighting the impact of both quantum confinement and dielectric confinement on carrier transport. It underscores the basic causes of thin, lowly doped nanowires in the temperature range 200 K ≤ T ≤ 500 K yielding very high carrier mobility. It suggests that the scattering by dislocations (stacking faults) can be very detrimental for carrier mobility. (paper)

Fusion radioactivity confinement and application to postulated ITER accidents

International Nuclear Information System (INIS)

Piet, S.J.; Brereton, S.J.

1991-01-01

An assessment of the ITER radioactivity confinement shows reduction of potential accidental releases to the environment by two orders of magnitude. Important credits are the 1% volume/day confinement leakage rate, radioactivity decay for short-lived isotopes, resumption of detritiation/negative pressure within seven days of the accident, and wind meander during the slow confinement leakage. Achieving this two order of magnitude credit in practice requires appropriate design details, especially the leakage rate and detritiation/negative pressure equipment, and research to validate some key assumptions. The confinement maximizes dependence on passive safety features, thereby working toward using fusion's potential safety advantages. The confinement includes several confinement zones with varying human access allowances. Some confinement areas are normally isolated from the environment, the closed ventilation zone. Some areas have an inert cover gas to inhibit combustion. If future assessments of accidental overpressure show the need, we propose a filter/vent system. This report documents our work for the ITER Conceptual Design Activity (CDA). The report is consistent with the final CDA design reports and descriptions, except that our analysis includes a filter/vent. For gaseous or vapor tritium and for most activated aerosols, the reference release fraction is about 2%. For short-lived tungsten-rhenium aerosols, the reference release fraction is somewhat lower, as low as 0.5% for some accident scenarios. Even without resumption of detritiation/decontamination or negative pressure within seven days of the accident, the release fraction for stays below 4%

Electrostatic-Dipole (ED) Fusion Confinement Studies

Science.gov (United States)

Miley, George H.; Shrestha, Prajakti J.; Yang, Yang; Thomas, Robert

2004-11-01

The Electrostatic-Dipole (ED) concept significantly differs from a "pure" dipole confinement device [1] in that the charged particles are preferentially confined to the high-pressure region interior of the dipole coil by the assistance of a surrounding spherical electrostatic grid. In present ED experiments, a current carrying coil is embedded inside the grid of an IEC such as to produce a magnetic dipole field. Charged particles are injected axisymmetrically from an ion gun (or duo-plasmatron) into the center of the ED confinement grid/dipole ring where they oscillate along the magnetic field lines and pass the peak field region at the center of the dipole region. As particles begin accelerating away from the center region towards the outer electrostatic grid region, they encounter a strong electrostatic potential (order of 10's of kilovolts) retarding force. The particles then decelerate, reverse direction and re-enter the dipole field region where again magnetic confinement dominates. This process continues, emulating a complex harmonic oscillator motion. The resulting pressure profile averaged over the field curvature offers good plasma stability in the ED configuration. The basic concept and results from preliminary experiments will be described. [1] M.E. Mauel, et al. "Dipole Equilibrium and Stability," 18th IAEA Conference of Plasma Phys. and Control. Nuclear Fusion, Varenna, Italy 2000, IAEA-F1-CN-70/TH

THz–IR spectroscopy of single H.sub.2./sub.O molecules confined in nanocage of beryl crystal lattice

Czech Academy of Sciences Publication Activity Database

Gorshunov, B. P.; Zhukova, E.S.; Torgashev, V. I.; Motovilova, E.A.; Lebedev, V.V.; Prokhorov, A. S.; Shakurov, G.S.; Kremer, R. K.; Uskov, V.V.; Pestrjakov, E.V.; Thomas, V.G.; Fursenko, D.A.; Kadlec, Christelle; Kadlec, Filip; Dressel, M.

2014-01-01

Roč. 87, 10-11 (2014), s. 966-972 ISSN 0141-1594 R&D Projects: GA ČR(CZ) GA14-25639S Institutional support: RVO:68378271 Keywords : terahertz spectroscopy * nano-confined water molecule Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.954, year: 2014

Experimental Study of Damage Evolution in Circular Stirrup-Confined Concrete.

Science.gov (United States)

Li, Zuohua; Peng, Zhihan; Teng, Jun; Wang, Ying

2016-04-08

This paper presents an experimental study on circular stirrup-confined concrete specimens under uniaxial and monotonic load. The effects of stirrup volume ratio, stirrup yield strength and concrete strength on damage evolution of stirrup-confined concrete were investigated. The experimental results showed that the strength and ductility of concrete are improved by appropriate arrangement of the stirrup confinement. Firstly, the concrete damage evolution can be relatively restrained with the increase of the stirrup volume ratio. Secondly, higher stirrup yield strength usually causes larger confining pressures and slower concrete damage evolution. In contrast, higher concrete strength leads to higher brittleness, which accelerates the concrete damage evolution. A plastic strain expression is obtained through curve fitting, and a damage evolution equation for circular stirrup-confined concrete is proposed by introducing a confinement factor ( C ) based on the experimental data. The comparison results demonstrate that the proposed damage evolution model can accurately describe the experimental results.

Experimental Study of Damage Evolution in Circular Stirrup-Confined Concrete

Science.gov (United States)

Li, Zuohua; Peng, Zhihan; Teng, Jun; Wang, Ying

2016-01-01

This paper presents an experimental study on circular stirrup-confined concrete specimens under uniaxial and monotonic load. The effects of stirrup volume ratio, stirrup yield strength and concrete strength on damage evolution of stirrup-confined concrete were investigated. The experimental results showed that the strength and ductility of concrete are improved by appropriate arrangement of the stirrup confinement. Firstly, the concrete damage evolution can be relatively restrained with the increase of the stirrup volume ratio. Secondly, higher stirrup yield strength usually causes larger confining pressures and slower concrete damage evolution. In contrast, higher concrete strength leads to higher brittleness, which accelerates the concrete damage evolution. A plastic strain expression is obtained through curve fitting, and a damage evolution equation for circular stirrup-confined concrete is proposed by introducing a confinement factor (C) based on the experimental data. The comparison results demonstrate that the proposed damage evolution model can accurately describe the experimental results. PMID:28773402

Microencapsulation of nanoemulsions: novel Trojan particles for bioactive lipid molecule delivery.

Science.gov (United States)

Li, Xiang; Anton, Nicolas; Ta, Thi Minh Chau; Zhao, Minjie; Messaddeq, Nadia; Vandamme, Thierry F

2011-01-01

Nanoemulsions consist of very stable nanodroplets of oil dispersed in an aqueous phase, typically below 300 nm in size. They can be used to obtain a very fine, homogeneous dispersion of lipophilic compounds in water, thus facilitating their handling and use in nanomedicine. However, the drawback is that they are suspended in an aqueous media. This study proposes a novel technique for drying lipid nanoemulsion suspensions to create so-called Trojan particles, ie, polymer microparticles (around 2 μm) which very homogeneously "entrap" the nano-oil droplets (around 150 nm) in their core. Microencapsulation of the nanoemulsions was performed using a spray-drying process and resulted in a dried powder of microparticles. By using a low-energy nanoemulsification method and relatively gentle spray-drying, the process was well suited to sensitive molecules. The model lipophilic molecule tested was vitamin E acetate, encapsulated at around 20% in dried powder. We showed that the presence of nanoemulsions in solution before spray-drying had a significant impact on microparticle size, distribution, and morphology. However, the process itself did not destroy the oil nanodroplets, which could easily be redispersed when the powder was put back in contact with water. High-performance liquid chromatography follow-up of the integrity of the vitamin E acetate showed that the molecules were intact throughout the process, as well as when conserved in their dried form. This study proposes a novel technique using a spray-drying process to microencapsulate nanoemulsions. The multiscale object formed, so-called Trojan microparticles, were shown to successfully encapsulate, protect, and release the lipid nanodroplets.

Issues in tokamak/stellarator transport and confinement enhancement mechanisms

International Nuclear Information System (INIS)

Perkins, F.W.

1990-08-01

At present, the mechanism for anomalous energy transport in low-β toroidal plasmas -- tokamaks and stellarators -- remains unclear, although transport by turbulent E x B velocities associated with nonlinear, fine-scale microinstabilities is a leading candidate. This article discusses basic theoretical concepts of various transport and confinement enhancement mechanisms as well as experimental ramifications which would enable one to distinguish among them and hence identify a dominant transport mechanism. While many of the predictions of fine-scale turbulence are born out by experiment, notable contradictions exist. Projections of ignition margin rest both on the scaling properties of the confinement mechanism and on the criteria for entering enhanced confinement regimes. At present, the greatest uncertainties lie with the basis for scaling confinement enhancement criteria. A series of questions, to be answered by new experimental/theoretical work, is posed to resolve these outstanding contradictions (or refute the fine-scale turbulence model) and to establish confinement enhancement criteria. 73 refs., 4 figs., 5 tabs

Large Eddy Simulation of the spray formation in confinements

International Nuclear Information System (INIS)

Lampa, A.; Fritsching, U.

2013-01-01

Highlights: • Process stability of confined spray processes is affected by the geometric design of the spray confinement. • LES simulations of confined spray flow have been performed successfully. • Clustering processes of droplets is predicted in simulations and validated with experiments. • Criteria for specific coherent gas flow patterns and droplet clustering behaviour are found. -- Abstract: The particle and powder properties produced within spray drying processes are influenced by various unsteady transport phenomena in the dispersed multiphase spray flow in a confined spray chamber. In this context differently scaled spray structures in a confined spray environment have been analyzed in experiments and numerical simulations. The experimental investigations have been carried out with Particle-Image-Velocimetry to determine the velocity of the gas and the discrete phase. Large-Eddy-Simulations have been set up to predict the transient behaviour of the spray process and have given more insight into the sensitivity of the spray flow structures in dependency from the spray chamber design

Some aspects of geometrical confinement

Energy Technology Data Exchange (ETDEWEB)

Novello, M.; De Lorenci, V.A. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Elbaz, E. [Lyon-1 Univ., 69 - Villeurbanne (France)

1998-04-01

In this paper we present a toy model for the dynamics of a gauge field theory in such way that spin-one particles can be confined in a compact domain. We show that the property of confinement can be associated to the formation of a null surface identified to a horizon. This is due to the presence of an effective geometry generated by the self-interaction of the gauge field that guides the wave propagation of the field. This phenomenon has a striking analogy to the gravitational black hole in Einstein general theory of relativity, separating two domains of spacetime that can be trespassed only into one direction. (author) 4 refs.

Unconfined versus confined speleogenetic settings: variations of solution porosity.

Directory of Open Access Journals (Sweden)

Klimchouk Alexander

2006-01-01

Full Text Available Speleogenesis in confined settings generates cave morphologies that differ much from those formed in unconfined settings. Cavesdeveloped in unconfined settings are characterised by broadly dendritic patterns of channels due to highly competing development.In contrast, caves originated under confined conditions tend to form two- or three-dimensional mazes with densely packed conduits.This paper illustrates variations of solution (channel porosity resulted from speleogenesis in unconfined and confined settings by theanalysis of morphometric parameters of typical cave patterns. Two samples of typical cave systems formed in the respective settingsare compared. The sample that represents unconfined speleogenesis consists of solely limestone caves, whereas gypsum cavesof this type tend to be less dendritic and more linear. The sample that represents confined speleogenesis consists of both limestoneand gypsum maze caves. The comparison shows considerable differences in average values of some parameters between thesettings. Passage network density (the ratio of the cave length to the area of the cave field, km/km2 is one order of magnitudegreater in confined settings than in unconfined (average 167.3 km/km2 versus 16.6 km/km2. Similarly, an order of magnitudedifference is observed in cave porosity (a fraction of the volume of a cave block, occupied by mapped cavities; 5.0 % versus 0.4 %.This illustrates that storage in maturely karstified confined aquifers is generally much greater than in unconfined. The average areal coverage (a fraction of the area of the cave field occupied by passages in a plan view is about 5 times greater in confined settingsthan in unconfined (29.7 % versus 6.4 %. This indicates that conduit permeability in confined aquifers is appreciably easier to targetwith drilling than the widely spaced conduits in unconfined aquifers.

Effects of confinement in meso-porous silica and carbon nano-structures; Etude des effets de confinement dans la silice mesoporeuse et dans certaines nanostructures carbonees

Energy Technology Data Exchange (ETDEWEB)

Leon, V

2006-07-15

Physico-chemical properties of materials can be strongly modified by confinement because of the quantum effects that appear at such small length scales and also because of the effects of the confinement itself. The aim of this thesis is to show that both the nature of the confining material and the size of the pores and cavities have a strong impact on the confined material. We first show the effect of the pore size of the host meso-porous silica on the temperature of the solid-solid phase transition of silver selenide, a semiconducting material with enhanced magnetoresistive properties under non-stoichiometric conditions. Narrowing the pores from 20 nm to 2 nm raises the phase transition temperature from 139 C to 146 C. This result can be explained by considering the interaction between the confining and confined materials as a driving force. The effects of confinement are also studied in the case of hydrogen and deuterium inside cavities of organized carbon nano-structures. The effects that appear in the adsorption/desorption cycles are much stronger with carbon nano-horns as the host material than with C60 pea-pods and single-walled carbon nano-tubes. (author)

Quark confinement potential and color Van der Waals force

International Nuclear Information System (INIS)

Zheng Yuming; Hua Daping; Liu Zuhua

1985-01-01

The color-analog Van der Waals force between two hadrons is studied by use of the coupling channel resonating group method in the framework of the Gaussian-type quark confinement potential. The problem of the boundary values for the two channel coupling differential equations is changed to the problem of the initial values. The equations are solved numerically by use of the Gear mehtod. The calculated results show that there is no color Van der Waals force between hadrons in the confinement potential model. This indicates that the confinement potential model not only can describe the internal structure of hadrons but also can be used to calculate the hadron-hadron interactions if the quark confinement potential is chosen properly

Subsurface imaging reveals a confined aquifer beneath an ice-sealed Antarctic lake

DEFF Research Database (Denmark)

Dugan, H. A.; Doran, P. T.; Tulaczyk, S.

2015-01-01

Liquid water oases are rare under extreme cold desert conditions found in the Antarctic McMurdo Dry Valleys. Here we report geophysical results that indicate that Lake Vida, one of the largest lakes in the region, is nearly frozen and underlain by widespread cryoconcentrated brine. A ground...... this zone to be a confined aquifer situated in sediments with a porosity of 23-42%. Discovery of this aquifer suggests that subsurface liquid water may be more pervasive in regions of continuous permafrost than previously thought and may represent an extensive habitat for microbial populations. Key Points...... Geophysical survey finds low resistivities beneath a lake in Antarctic Dry Valleys Liquid brine abundant beneath Antarctic lake Aquifer provides microbial refugium in cold desert environment...

An experiment to test centrifugal confinement for fusion

International Nuclear Information System (INIS)

Ellis, R.F.; Hassam, A.B.; Messer, S.; Osborn, B.R.

2001-01-01

The basic idea of centrifugal confinement is to use centrifugal forces from supersonic rotation to augment conventional magnetic confinement. Optimizing this 'knob' results in a fusion device that features four advantages: steady state, no disruptions, superior cross-field confinement, and a simpler coil configuration. The idea rests on two prongs: first, centrifugal forces can confine plasmas to desired regions of shaped magnetic fields; second, the accompanying large velocity shear can stabilize even magnetohydrodynamic (MHD) instabilities. A third feature is that the velocity shear also viscously heats the plasma; no auxiliary heating is necessary to reach fusion temperatures. Regarding transport, the velocity shear can also quell microturbulence, leading to fully classical confinement, as there are no neoclassical effects. Classical parallel electron transport then sets the confinement time. These losses are minimized by a large Pastukhov factor resulting from the deep centrifugal potential well: at Mach 4-5, the Lawson criterion is accessible. One key issue is whether velocity shear will be sufficient by itself to stabilize MHD interchanges. Numerical simulations indicate that laminar equilibria can be obtained at Mach numbers of 4-5 but that the progression toward laminarity with increasing Mach number is accompanied by residual convection from the interchanges. The central goal of the Maryland Centrifugal Torus (MCT) [R. F. Ellis et al., Bull. Am. Phys. Soc. 44, 48 (1998)] is to obtain MHD stability from velocity shear. As an assist to accessing laminarity, MCT will incorporate two unique features: plasma elongation and toroidal magnetic field. The former raises velocity shear efficiency, and modest magnetic shear should suppress residual convection

Influence of error fields on the plasma confining field and the plasma confinement in tokamak

International Nuclear Information System (INIS)

Matsuda, Shinzaburo

1977-05-01

Influence of error fields on the plasma confining field and the plasma confinement is treated in the standpoint of design. In the initial breakdown phase before formation of the closed magnetic surfaces, the vertical field properly applied is the most important. Once the magnetic surfaces are formed, the non-axisymmetric error field is important. Effect of the shell gap associated with iron core and with pulsed vertical coils is thus studied. The formation of magnetic islands due to the external non-axisymmetric error field is studied with a simple model. A method of suppressing the islands by choosing the minor periodicity is proposed. (auth.)

Confinement and Tritium Stripping Systems for APT Tritium Processing

Energy Technology Data Exchange (ETDEWEB)

Hsu, R.H. [Westinghouse Savannah River Company, AIKEN, SC (United States); Heung, L.K.

1997-10-20

This report identifies functions and requirements for the tritium process confinement and clean-up system (PCCS) and provides supporting technical information for the selection and design of tritium confinement, clean-up (stripping) and recovery technologies for new tritium processing facilities in the Accelerator for the Production of Tritium (APT). The results of a survey of tritium confinement and clean-up systems for large-scale tritium handling facilities and recommendations for the APT are also presented.

Confinement and Tritium Stripping Systems for APT Tritium Processing

International Nuclear Information System (INIS)

Hsu, R.H.; Heung, L.K.

1997-01-01

This report identifies functions and requirements for the tritium process confinement and clean-up system (PCCS) and provides supporting technical information for the selection and design of tritium confinement, clean-up (stripping) and recovery technologies for new tritium processing facilities in the Accelerator for the Production of Tritium (APT). The results of a survey of tritium confinement and clean-up systems for large-scale tritium handling facilities and recommendations for the APT are also presented

Cluster Analysis of the International Stellarator Confinement Database

International Nuclear Information System (INIS)

Kus, A.; Dinklage, A.; Preuss, R.; Ascasibar, E.; Harris, J. H.; Okamura, S.; Yamada, H.; Sano, F.; Stroth, U.; Talmadge, J.

2008-01-01

Heterogeneous structure of collected data is one of the problems that occur during derivation of scalings for energy confinement time, and whose analysis tourns out to be wide and complicated matter. The International Stellarator Confinement Database [1], shortly ISCDB, comprises in its latest version 21 a total of 3647 observations from 8 experimental devices, 2067 therefrom beeing so far completed for upcoming analyses. For confinement scaling studies 1933 observation were chosen as the standard dataset. Here we describe a statistical method of cluster analysis for identification of possible cohesive substructures in ISDCB and present some preliminary results

High efficiency confinement mode by electron cyclotron heating

International Nuclear Information System (INIS)

Funahashi, Akimasa

1987-01-01

In the medium size nuclear fusion experiment facility JFT-2M in the Japan Atomic Energy Research Institute, the research on the high efficiency plasma confinement mode has been advanced, and in the experiment in June, 1987, the formation of a high efficiency confinement mode was successfully controlled by electron cyclotron heating, for the first time in the world. This result further advanced the control of the formation of a high efficiency plasma confinement mode and the elucidation of the physical mechanism of that mode, and promoted the research and development of the plasma heating by electron cyclotron heating. In this paper, the recent results of the research on a high efficiency confinement mode at the JFT-2M are reported, and the role of the JFT-2M and the experiment on the improvement of core plasma performance are outlined. Now the plasma temperature exceeding 100 million deg C has been attained in large tokamaks, and in medium size facilities, the various measures for improving confinement performance are to be brought forth and their scientific basis is elucidated to assist large facilities. The JFT-2M started the operation in April, 1983, and has accumulated the results smoothly since then. (Kako, I.)

Surface-Activated Coupling Reactions Confined on a Surface.

Science.gov (United States)

Dong, Lei; Liu, Pei Nian; Lin, Nian

2015-10-20

Chemical reactions may take place in a pure phase of gas or liquid or at the interface of two phases (gas-solid or liquid-solid). Recently, the emerging field of "surface-confined coupling reactions" has attracted intensive attention. In this process, reactants, intermediates, and products of a coupling reaction are adsorbed on a solid-vacuum or a solid-liquid interface. The solid surface restricts all reaction steps on the interface, in other words, the reaction takes place within a lower-dimensional, for example, two-dimensional, space. Surface atoms that are fixed in the surface and adatoms that move on the surface often activate the surface-confined coupling reactions. The synergy of surface morphology and activity allow some reactions that are inefficient or prohibited in the gas or liquid phase to proceed efficiently when the reactions are confined on a surface. Over the past decade, dozens of well-known "textbook" coupling reactions have been shown to proceed as surface-confined coupling reactions. In most cases, the surface-confined coupling reactions were discovered by trial and error, and the reaction pathways are largely unknown. It is thus highly desirable to unravel the mechanisms, mechanisms of surface activation in particular, of the surface-confined coupling reactions. Because the reactions take place on surfaces, advanced surface science techniques can be applied to study the surface-confined coupling reactions. Among them, scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) are the two most extensively used experimental tools. The former resolves submolecular structures of individual reactants, intermediates, and products in real space, while the latter monitors the chemical states during the reactions in real time. Combination of the two methods provides unprecedented spatial and temporal information on the reaction pathways. The experimental findings are complemented by theoretical modeling. In particular, density

Sources of trends in water-quality data for selected streams in Texas, 1975-89 water years

Science.gov (United States)

Schertz, T.L.; Wells, F.C.; Ohe, D.J.

1994-01-01

Sources of trends in water-quality data for selected streams in Texas for the 1975-89 water years were investigated in this study. The investigation of sources was confined to distinct geographic patterns in the trend indicators for one constituent or for a group of related constituents.

3D-CFD Simulation of Confined Cross-Flow Injection Process Using Single Piston Pump

Directory of Open Access Journals (Sweden)

M. Elashmawy

2017-12-01

Full Text Available Injection process into a confined cross flow is quite important for many applications including chemical engineering and water desalination technology. The aim of this study is to investigate the performance of the injection process into a confined cross-flow of a round pipe using a single piston injection pump. A computational fluid dynamics (CFD analysis has been carried out to investigate the effect of the locations of the maximum velocity and minimum pressure on the confined cross-flow process. The jet trajectory is analyzed and related to the injection pump shaft angle of rotation during the injection duty cycle by focusing on the maximum instant injection flow of the piston action. Results indicate a low effect of the jet trajectory within the range related to the injection pump operational conditions. Constant cross-flow was used and injection flow is altered to vary the jet to line flow ratio (QR. The maximum jet trajectory exhibits low penetration inside the cross-flow. The results showed three regions of the flow ratio effect zones with different behaviors. Results also showed that getting closer to the injection port causes a significant decrease on the locations of the maximum velocity and minimum pressure.

Waste-acceptance criteria for greater confinement disposal

International Nuclear Information System (INIS)

Gilbert, T.L.; Meshkov, N.K.

1987-01-01

A methodology for establishing waste-acceptance criteria based on quantitative performance factors that characterize the confinement capabilities of a waste disposal site and facility has been developed. The methodology starts from the basic objective of protecting public health and safety by providing assurance that disposal of the waste will not result in a radiation dose to any member of the general public, in either the short or long term, in excess of an established basic dose limit. The method is based on an explicit, straight-forward, and quantitative relationship among individual risk, confinement capabilities, and waste characteristics. A key aspect of the methodology is introduction of a confinement factor that characterizes the overall confinement capability of a particular facility and can be used for quantitative assessments of the performance of different disposal sites and facilities, as well as for establishing site-specific waste acceptance criteria. Confinement factors are derived by means of site-specific pathway analyses. They make possible a direct and simple conversion of a basic dose limit into waste-acceptance criteria, specified as concentration limits on radionuclides in the waste streams and expressed in quantitative form as a function of parameters that characterize the site, facility design, waste containers, and waste form. Waste acceptance criteria can be represented visually as activity/time plots for various waste streams. These plots show the concentrations of radionuclides in a waste stream as a function of time and permit a visual, quantitative assessment of long-term performance, relative risks from different radionuclides in the waste stream, and contributions from ingrowth. 13 references, 7 figures

Waste-acceptance criteria for greater-confinement disposal

International Nuclear Information System (INIS)

Gilbert, T.L.; Meshkov, N.K.

1986-01-01

A methodology for establishing waste-acceptance criteria based on quantitative performance factors that characterize the confinement capabilities of a waste-disposal site and facility has been developed. The methodology starts from the basic objective of protecting public health and safety by providing assurance that dispsoal of the waste will not result in a radiation dose to any member of the general public, in either the short or long term, in excess of an established basic dose limit. The method is based on an explicit, straightforward, and quantitative relationship among individual risk, confinement capabilities, and waste characteristics. A key aspect of the methodology is the introduction of a confinement factor that characterizes the overall confinement capability of a particular facility and can be used for quantitative assessments of the performance of different disposal sites and facilities, as well as for establishing site-specific waste-acceptance criteria. Confinement factors are derived by means of site-specific pathway analyses. They make possible a direct and simple conversion of a basic dose limit into waste-acceptance criteria, specified as concentration limits on radionuclides in the waste streams and expressed in quantitative form as a function of parameters that characterize the site, facility design, waste containers, and waste form. Waste-acceptance criteria can be represented visually as activity/time plots for various waste streams. These plots show the concentrations of radionuclides in a waste stream as a function of time and permit a visual, quantitative assessment of long-term performance, relative risks from different radionuclides in the waste stream, and contributions from ingrowth. 13 refs

Static dielectric constant of water within a bilayer using recent water models: a molecular dynamics study

Science.gov (United States)

Meneses-Juárez, Efrain; Rivas-Silva, Juan Francisco; González-Melchor, Minerva

2018-05-01

The water confined within a surfactant bilayer is studied using different water models via molecular dynamics simulations. We considered four representative rigid models of water: the SPC/E and the TIP4P/2005, which are commonly used in numerical calculations and the more recent TIP4Q and SPC/ε models, developed to reproduce the dielectric behaviour of pure water. The static dielectric constant of the confined water was analyzed as a function of the temperature for the four models. In all cases it decreases as the temperature increases. Additionally, the static dielectric constant of the bilayer-water system was estimated through its expression in terms of the fluctuations in the total dipole moment, usually applied for isotropic systems. The estimated dielectric was compared with the available experimental data. We found that the TIP4Q and the SPC/ε produce closer values to the experimental data than the other models, particularly at room temperature. It was found that the probability of finding the sodium ion close to the head of the surfactant decreases as the temperature increases, thus the head of the surfactant is more exposed to the interaction with water when the temperature is higher.

Hydrogeology and chemical quality of water and soil at Carroll Island, Aberdeen Proving Ground, Maryland

Science.gov (United States)

Tenbus, F.J.; Phillips, S.W.

1996-01-01

Carroll Island was used for open-air testing of chemical warfare agents from the late 1940's until 1971. Testing and disposal activities weresuspected of causing environmental contamination at 16 sites on the island. The hydrogeology and chemical quality of ground water, surface water, and soil at these sites were investigated with borehole logs, environmental samples, water-level measurements, and hydrologic tests. A surficial aquifer, upper confining unit, and upper confined aquifer were defined. Ground water in the surficial aquifer generally flows from the east-central part of the island toward the surface-water bodies, butgradient reversals caused by evapotranspiration can occur during dry seasons. In the confined aquifer, hydraulic gradients are low, and hydraulic head is affected by tidal loading and by seasonal pumpage from the west. Inorganic chemistry in the aquifers is affected by brackish-water intrusion from gradient reversals and by dissolution ofcarboniferous shell material in the confining unit.The concentrations of most inorganic constituents probably resulted from natural processes, but some concentrations exceeded Federal water-quality regulations and criteria. Organic compounds were detected in water and soil samples at maximum concentrations of 138 micrograms per liter (thiodiglycol in surface water) and 12 micrograms per gram (octadecanoic acid in soil).Concentrations of organic compounds in ground water exceeded Federal drinking-water regulations at two sites. The organic compounds that weredetected in environmental samples were variously attributed to natural processes, laboratory or field- sampling contamination, fallout from industrial air pollution, and historical military activities.

Isotope effect on confinement in DT plasmas

International Nuclear Information System (INIS)

Fukuyama, A.; Itoh, K.; Itoh, S.; Yagi, M.; Azumi, M.

1994-03-01

Isotope effect on the energy confinement time is discussed for the DT plasma. The transport theory which is based on the ballooning mode turbulence is applied. When the DT plasma is produced under the condition of β p >1, the energy confinement time of DT plasma (50% mixture) is expected to be about 1.2 times better than the D plasma with the same operation condition. (author)

Tritium burning in inertial electrostatic confinement fusion facility

Energy Technology Data Exchange (ETDEWEB)

Ohnishi, Masami, E-mail: onishi@kansai-u.ac.jp [Department of Science and Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan); Yamamoto, Yasushi; Osawa, Hodaka [Department of Science and Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan); Hatano, Yuji; Torikai, Yuji [Hydrogen Isotope Science Center, University of Toyama, Gofuku, Toyama 930-8555 (Japan); Murata, Isao [Faculty of Engineering Environment and Energy Department, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Kamakura, Keita; Onishi, Masaaki; Miyamoto, Keiji; Konda, Hiroki [Department of Science and Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan); Masuda, Kai [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Hotta, Eiki [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuda-cho, Midori-ku, Yokohama 226-8503 (Japan)

2016-11-01

Highlights: • An experiment on tritium burning is conducted in an inertial electrostatic confinement fusion (IECF) facility. • A deuterium–tritium gas mixture with 93% deuterium and 7% tritium is used. • The neutron production rate is measured to be 5–8 times more than that of pure deuterium gas. • The neutron production rate of the D–T gas mixture in 1:1 ratio is expected to be more than 10{sup 8}(1/sec) in the present D–T experiment. - Abstract: An experiment on tritium burning is conducted to investigate the enhancement in the neutron production rate in an inertial electrostatic confinement fusion (IECF) facility. The facility is designed such that it is shielded from the outside for safety against tritium and a getter pump is used for evacuating the vacuum chamber and feeding the fuel gas. A deuterium–tritium gas mixture with 93% deuterium and 7% tritium is used, and its neutron production rate is measured to be 5–8 times more than that of pure deuterium gas. Moreover, the results show good agreement with those of a simplified theoretical estimation of the neutron production rate. After tritium burning, the exhausted fuel gas undergoes a tritium recovery procedure through a water bubbler device. The amount of gaseous tritium released by the developed IECF facility after tritium burning is verified to be much less than the threshold set by regulations.

Tritium burning in inertial electrostatic confinement fusion facility

International Nuclear Information System (INIS)

Ohnishi, Masami; Yamamoto, Yasushi; Osawa, Hodaka; Hatano, Yuji; Torikai, Yuji; Murata, Isao; Kamakura, Keita; Onishi, Masaaki; Miyamoto, Keiji; Konda, Hiroki; Masuda, Kai; Hotta, Eiki

2016-01-01

Highlights: • An experiment on tritium burning is conducted in an inertial electrostatic confinement fusion (IECF) facility. • A deuterium–tritium gas mixture with 93% deuterium and 7% tritium is used. • The neutron production rate is measured to be 5–8 times more than that of pure deuterium gas. • The neutron production rate of the D–T gas mixture in 1:1 ratio is expected to be more than 10"8(1/sec) in the present D–T experiment. - Abstract: An experiment on tritium burning is conducted to investigate the enhancement in the neutron production rate in an inertial electrostatic confinement fusion (IECF) facility. The facility is designed such that it is shielded from the outside for safety against tritium and a getter pump is used for evacuating the vacuum chamber and feeding the fuel gas. A deuterium–tritium gas mixture with 93% deuterium and 7% tritium is used, and its neutron production rate is measured to be 5–8 times more than that of pure deuterium gas. Moreover, the results show good agreement with those of a simplified theoretical estimation of the neutron production rate. After tritium burning, the exhausted fuel gas undergoes a tritium recovery procedure through a water bubbler device. The amount of gaseous tritium released by the developed IECF facility after tritium burning is verified to be much less than the threshold set by regulations.

Confinement of hydrogen at high pressure in carbon nanotubes

Science.gov (United States)

Lassila, David H [Aptos, CA; Bonner, Brian P [Livermore, CA

2011-12-13

A high pressure hydrogen confinement apparatus according to one embodiment includes carbon nanotubes capped at one or both ends thereof with a hydrogen-permeable membrane to enable the high pressure confinement of hydrogen and release of the hydrogen therethrough. A hydrogen confinement apparatus according to another embodiment includes an array of multi-walled carbon nanotubes each having first and second ends, the second ends being capped with palladium (Pd) to enable the high pressure confinement of hydrogen and release of the hydrogen therethrough as a function of palladium temperature, wherein the array of carbon nanotubes is capable of storing hydrogen gas at a pressure of at least 1 GPa for greater than 24 hours. Additional apparatuses and methods are also presented.

Confined-but-Connected Quantum Solids via Controlled Ligand Displacement

KAUST Repository

Baumgardner, William J.

2013-07-10

Confined-but-connected quantum dot solids (QDS) combine the advantages of tunable, quantum-confined energy levels with efficient charge transport through enhanced electronic interdot coupling. We report the fabrication of QDS by treating self-assembled films of colloidal PbSe quantum dots with polar nonsolvents. Treatment with dimethylformamide balances the rates of self-assembly and ligand displacement to yield confined-but-connected QDS structures with cubic ordering and quasi-epitaxial interdot connections through facets of neighboring dots. The QDS structure was analyzed by a combination of transmission electron microscopy and wide-angle and small-angle X-ray scattering. Excitonic absorption signatures in optical spectroscopy confirm that quantum confinement is preserved. Transport measurements show significantly enhanced conductivity in treated films. © 2013 American Chemical Society.

Static and Dynamic Properties of DNA Confined in Nanochannels

Science.gov (United States)

Gupta, Damini

Next-generation sequencing (NGS) techniques have considerably reduced the cost of high-throughput DNA sequencing. However, it is challenging to detect large-scale genomic variations by NGS due to short read lengths. Genome mapping can easily detect large-scale structural variations because it operates on extremely large intact molecules of DNA with adequate resolution. One of the promising methods of genome mapping is based on confining large DNA molecules inside a nanochannel whose cross-sectional dimensions are approximately 50 nm. Even though this genome mapping technology has been commercialized, the current understanding of the polymer physics of DNA in nanochannel confinement is based on theories and lacks much needed experimental support. The results of this dissertation are aimed at providing a detailed experimental understanding of equilibrium properties of nanochannel-confined DNA molecules. The results are divided into three parts. In first part, we evaluate the role of channel shape on thermodynamic properties of channel confined DNA molecules using a combination of fluorescence microscopy and simulations. Specifically, we show that high aspect ratio of rectangular channels significantly alters the chain statistics as compared to an equivalent square channel with same cross-sectional area. In the second part, we present experimental evidence that weak excluded volume effects arise in DNA nanochannel confinement, which form the physical basis for the extended de Gennes regime. We also show how confinement spectroscopy and simulations can be combined to reduce molecular weight dispersity effects arising from shearing, photo-cleavage, and nonuniform staining of DNA. Finally, the third part of the thesis concerns the dynamic properties of nanochannel confined DNA. We directly measure the center-of-mass diffusivity of single DNA molecules in confinement and show that that it is necessary to modify the classical results of de Gennes to account for local chain

Confinement studies of ohmically heated plasmas in TFTR

International Nuclear Information System (INIS)

Efthimion, P.C.; Bretz, N.L.; Bell, M.G.

1985-03-01

Systematic scans of density in large deuterium plasmas (a = 0.83 m) at several values of plasma current and toroidal magnetic field strength indicate that the total energy confinement time, tau/sub E/, is proportional to the line-average density anti n/sub e/ and the limiter q. Confinement times of approx. 0.3 s have been observed for anti n/sub e/ = 2.8 x 10 19 m -3 . Plasma size scaling experiments with plasmas of minor radii a = 0.83, 0.69, 0.55, and 0.41 m at constant limiter q reveal a confinement dependence on minor radius. The major-radius dependence of tau/sub E/, based on a comparison between TFTR and PLT results, is consistent with R 2 scaling. From the power balance, the thermal diffusivity chi/sub e/ is found to be significantly less than the INTOR value. In the a = 0.41 m plasmas, saturation of confinement is due to neoclassical ion conduction (chi/sub i/ neoclassical >> chi/sub e/)

Universal evaporation dynamics of a confined sessile droplet

Science.gov (United States)

Bansal, Lalit; Hatte, Sandeep; Basu, Saptarshi; Chakraborty, Suman

2017-09-01

Droplet evaporation under confinement is ubiquitous to multitude of applications such as microfluidics, surface patterning, and ink-jet printing. However, the rich physics governing the universality in the underlying dynamics remains grossly elusive. Here, we bring out hitherto unexplored universal features of the evaporation dynamics of a sessile droplet entrapped in a 3D confined fluidic environment. We show, through extensive set of experiments and theoretical formulations, that the evaporation timescale for such a droplet can be represented by a unique function of the initial conditions. Moreover, using same theoretical considerations, we are able to trace and universally merge the volume evolution history of the droplets along with evaporation lifetimes, irrespective of the extent of confinement. We also showcase the internal flow transitions caused by spatio-temporal variation of evaporation flux due to confinement. These findings may be of profound importance in designing functionalized droplet evaporation devices for emerging engineering and biomedical applications.

Core electron-root confinement (CERC) in helical plasmas

International Nuclear Information System (INIS)

Yokoyama, M.; Ida, K.; Maassbcrg, H.

2006-10-01

The improvement of core electron heat confinement has been realized in a wide range of helical devices such as CHS, LHD, TJ-II and W7-AS. Strongly peaked electron temperature profiles and large positive radial electric field, E r , in the core region are common fractures for this improved confinement. Such observations are consistent with a transition to the electron-root' solution of the ambipolarity condition for E r in the context of the neoclassical transport, which is unique to non-axisymmetric configurations. Based on this background, this improved confinement has been collectively dubbed 'core electron-root confinement' (CERC). The electron heat diffusivity is much reduced due to the electron-root E r compared to that with E r =0 assumed, which clearly demonstrates that 1/v ripple diffusion (ν being the collision frequency) in low-collisional helical plasmas could be overcome. The magnetic configuration properties play important roles in this transition, and thresholds are found for the collisionality and electron cyclotron heating (ECH) power. (author)

Topological superconductivity, topological confinement, and the vortex quantum Hall effect

International Nuclear Information System (INIS)

Diamantini, M. Cristina; Trugenberger, Carlo A.

2011-01-01

Topological matter is characterized by the presence of a topological BF term in its long-distance effective action. Topological defects due to the compactness of the U(1) gauge fields induce quantum phase transitions between topological insulators, topological superconductors, and topological confinement. In conventional superconductivity, because of spontaneous symmetry breaking, the photon acquires a mass due to the Anderson-Higgs mechanism. In this paper we derive the corresponding effective actions for the electromagnetic field in topological superconductors and topological confinement phases. In topological superconductors magnetic flux is confined and the photon acquires a topological mass through the BF mechanism: no symmetry breaking is involved, the ground state has topological order, and the transition is induced by quantum fluctuations. In topological confinement, instead, electric charge is linearly confined and the photon becomes a massive antisymmetric tensor via the Stueckelberg mechanism. Oblique confinement phases arise when the string condensate carries both magnetic and electric flux (dyonic strings). Such phases are characterized by a vortex quantum Hall effect potentially relevant for the dissipationless transport of information stored on vortices.

Hydrogeochemical surveillance of La Soufriere de Guadeloupe volcano (F. W. I. ), 1979-1985: activity decrease or confining

Energy Technology Data Exchange (ETDEWEB)

Bigot, S.; Hammouya, G.

1987-04-07

Since the 1975-1977 crisis, changes in physico-chemical characters of La Soufriere's hot springs are observed. These variations have dual origin: - decrease in exchanges between volatile compounds from deep origin and phreatic waters, because of fissures filling by hydrothermal deposits in the whole dome that involves progresive confining: - decrease of volcanic activity.

Porous shaped photonic crystal fiber with strong confinement field in sensing applications: Design and analysis

Directory of Open Access Journals (Sweden)

Sawrab Chowdhury

2017-04-01

Full Text Available In this article, porous core porous cladding photonic crystal fiber (P-PCF has been proposed for aqueous analytes sensing applications. Guiding properties of the proposed P-PCF has been numerically investigated by utilizing the full vectorial finite element method (FEM. The relative sensitivity and confinement loss are obtained by varying distinct geometrical parameters like the diameter of air holes, a pitch of the core and cladding region over a wider range of wavelength. The proposed P-PCF is organized with five rings air hole in the cladding and two rings air hole in a core territory which maximizes the relative sensitivity expressively and minimizes confinement loss depressively compare with the prior-PCF structures. After completing all investigations, it is also visualized that the relative sensitivity is increasing with the increment of the wavelength of communication band (O + E + S + C + L + U. Higher sensitivity is gained by using higher band for all applied liquids. Finally the investigating effects of different structural parameters of the proposed P-PCF are optimized which shows the sensitivity of 60.57%, 61.45% and 61.82%; the confinement loss of 8.71 × 10−08 dB/m, 1.41 × 10−10 dB/m and 6.51 × 10−10 dB/m for Water (n = 1.33, Ethanol (n = 1.354 and Benzene (n = 1.366 respectively at 1.33 μm wavelength. The optimized P-PCF with higher sensitivity and lower confinement loss has high impact in the area of the chemical as well as gas sensing purposes. Keywords: Porous shaped PCF, Sensitivity, Optical sensing, Liquid sensor, Confinement loss

Water in the presence of inert Lennard-Jones obstacles

Science.gov (United States)

Kurtjak, Mario; Urbic, Tomaz

2014-04-01

Water confined by the presence of a 'sea' of inert obstacles was examined. In the article, freely mobile two-dimensional Mercedes-Benz (MB) water put to a disordered, but fixed, matrix of Lennard-Jones disks was studied by the Monte Carlo computer simulations. For the MB water molecules in the matrix of Lennard-Jones disks, we explored the structures, hydrogen-bond-network formation and thermodynamics as a function of temperature and size and density of matrix particles. We found that the structure of model water is perturbed by the presence of the obstacles. Density of confined water, which was in equilibrium with the bulk water, was smaller than the density of the bulk water and the temperature dependence of the density of absorbed water did not show the density anomaly in the studied temperature range. The behaviour observed as a consequence of confinement is similar to that of increasing temperature, which can for a matrix lead to a process similar to capillary evaporation. At the same occupancy of space, smaller matrix molecules cause higher destruction effect on the absorbed water molecules than the bigger ones. We have also tested the hypothesis that at low matrix densities the obstacles induce an increased ordering and 'hydrogen bonding' of the MB model molecules, relative to pure fluid, while at high densities the obstacles reduce MB water structuring, as they prevent the fluid to form good 'hydrogen-bonding' networks. However, for the size of matrix molecules similar to that of water, we did not observe this effect.

Confined aquifer vulnerability induced by a pumping well in a leakage area

Directory of Open Access Journals (Sweden)

X. Meng

2015-05-01

Full Text Available Due to the pollution of shallow groundwater and the rapid development of society and economy which consume more freshwater, the exploitation of confined groundwater is steadily increasing in north China. Therefore, the rapid decline of the confined groundwater head increases the risk of confined aquifer pollution by leaky recharge from shallow aquifers. In this paper, a quantitative method for assessing confined aquifer vulnerability to contamination due to pumping has been developed. This method is based on the shallow and confined groundwater flow model and the advection and dispersion in the aquitard, including sorption. The cumulative time for the pollutant concentration at the top boundary of confined aquifer exceeding the maximum allowable level is defined as the confined aquifer vulnerability index, which can be obtained by numerically solving the solute transport equation. A hypothetical example is chosen as a case study to illustrate the whole process. The results indicate that the proposed method is a practical and reasonable assessment method of confined aquifer vulnerability.

Synthesis of Polyimides in Molecular-Scale Confinement for Low-Density Hybrid Nanocomposites.

Science.gov (United States)

Isaacson, Scott G; Fostvedt, Jade I; Koerner, Hilmar; Baur, Jeffery W; Lionti, Krystelle; Volksen, Willi; Dubois, Geraud; Dauskardt, Reinhold H

2017-11-08

In this work, we exploit a confinement-induced molecular synthesis and a resulting bridging mechanism to create confined polyimide thermoset nanocomposites that couple molecular confinement-enhanced toughening with an unprecedented combination of high-temperature properties at low density. We describe a synthesis strategy that involves the infiltration of individual polymer chains through a nanoscale porous network while simultaneous imidization reactions increase the molecular backbone stiffness. In the extreme limit where the confinement length scale is much smaller than the polymer's molecular size, confinement-induced molecular mechanisms give rise to exceptional mechanical properties. We find that polyimide oligomers can undergo cross-linking reactions even in such molecular-scale confinement, increasing the molecular weight of the organic phase and toughening the nanocomposite through a confinement-induced energy dissipation mechanism. This work demonstrates that the confinement-induced molecular bridging mechanism can be extended to thermoset polymers with multifunctional properties, such as excellent thermo-oxidative stability and high service temperatures (>350 °C).

Neutron Assay System for Confinement Vessel Disposition

International Nuclear Information System (INIS)

Frame, Katherine C.; Bourne, Mark M.; Crooks, William J.; Evans, Louise; Mayo, Douglas R.; Miko, David K.; Salazar, William R.; Stange, Sy; Valdez, Jose I.; Vigil, Georgiana M.

2012-01-01

Los Alamos National Laboratory has a number of spherical confinement vessels (CVs) remaining from tests involving nuclear materials. These vessels have an inner diameter of 6 feet with 1-inch thick steel walls. The goal of the Confinement Vessel Disposition (CVD) project is to remove debris and reduce contamination inside the CVs. The Confinement Vessel Assay System (CVAS) was developed to measure the amount of special nuclear material (SNM) in CVs before and after cleanout. Prior to cleanout, the system will be used to perform a verification measurement of each vessel. After cleanout, the system will be used to perform safeguards-quality assays of (le)100-g 239 Pu equivalent in a vessel for safeguards termination. The CVAS has been tested and calibrated in preparation for verification and safeguards measurements.

Studies on the quark confinement in a non-relativistic quark model

International Nuclear Information System (INIS)

Pfenninger, T.

1988-01-01

In the framework of the non-relativistic quark model we have studied several aspects of the description of the confinement by a confinement potential. A first consideration applied to the effects of the long-range color van-der-Waals forces on the nucleon-nucleon scattering. Regarding color dipole states as an additional closed channel in a dynamical and nonlocal resonating-group calculation we found a strong attraction. Additionally it was possible by means of the RGM kernels to derive an against earlier calculations improved color van-der-Waals potential in adiabatic approximation which regards correctly the internal kinetic and the confinement energy of the color octet states. This potential is not confined to large NN distances and shows asymptotically a 1/R 2 behaviour if it is based on a harmonic confinement. A further study applied to the question how far a possible vector character of the confinement, which is suggested by the elementary quark-gluon vertex, has effects on baryon properties and the NN interaction. Here it resulted that the vector confinement reacts in view of the model parameters very sensitively in the baryon properties whereas the scalar confinement did not show this dependence. In the NN scattering this vector confinement however plays a more secondary role. Because of the difficulties of the usual confinement potential with long-range color van-der-Waals forces we proposed in the last part a new potential and additional orthogonality relations for the quark wave functions in order to accomodate in the potential model to the string degrees of freedom. In scattering calculations we again studied the effects of the modification on the NN interaction. (orig./HSI) [de

Confined exciton spectroscopy

International Nuclear Information System (INIS)

Torres, Clivia M.S.

1998-01-01

Full text: In this work, the exciton is considered as a sensor of the electronic and optical properties of materials such as semiconductors, which have size compared to the exciton De Broglie wavelength, approximately 20 nm, depending on the semiconductor. Examples of electron-phonon, electron-electron, photon-electron, exciton-polariton, phonon-plasmon, are presented, under different confinement conditions such as quantum wells, superlattices

Thermostating highly confined fluids.

Science.gov (United States)

Bernardi, Stefano; Todd, B D; Searles, Debra J

2010-06-28

In this work we show how different use of thermostating devices and modeling of walls influence the mechanical and dynamical properties of confined nanofluids. We consider a two dimensional fluid undergoing Couette flow using nonequilibrium molecular dynamics simulations. Because the system is highly inhomogeneous, the density shows strong fluctuations across the channel. We compare the dynamics produced by applying a thermostating device directly to the fluid with that obtained when the wall is thermostated, considering also the effects of using rigid walls. This comparison involves an analysis of the chaoticity of the fluid and evaluation of mechanical properties across the channel. We look at two thermostating devices with either rigid or vibrating atomic walls and compare them with a system only thermostated by conduction through vibrating atomic walls. Sensitive changes are observed in the xy component of the pressure tensor, streaming velocity, and density across the pore and the Lyapunov localization of the fluid. We also find that the fluid slip can be significantly reduced by rigid walls. Our results suggest caution in interpreting the results of systems in which fluid atoms are thermostated and/or wall atoms are constrained to be rigid, such as, for example, water inside carbon nanotubes.

Alternative lines with magnetic plasma confinement

International Nuclear Information System (INIS)

Wobig, H.

1981-01-01

Plasma confinement with the aid of a magnetic field is the most common and also the most frequently investigated principle on the way to controlled nuclear fusion. Apart from the Tokamak principle, which is the most advanced principle as far as fusion-relevant plasma parameters are concerned, also other approaches are being investigated, e.g. the mirror device, the bumpy tons, and the stellarator. In principle, all three concepts permit 'stationary' plasma confinement in a stationary fusion reactor. Compared with the pulsed Tokamak reactor, this is a considerable advantage. (orig./GG) [de

Magnetic properties of confined electron gas

International Nuclear Information System (INIS)

Felicio, J.R.D. de.

1977-04-01

The effects of confinement by a two or three-dimensional harmonic potential on the magnetic properties of a free electron gas are investigated using the grand-canonical ensemble framework. At high temperatures an extension of Darwin's, Felderhof and Raval's works is made taking into account spin effects at low temperature. A comprehensive description of the magnetic properties of a free electron gas is given. The system is regarded as finite, but the boundary condition psi=0 is not introduced. The limits of weak and strong confinement are also analysed [pt

Surface motion and confinement potential for a microwave confined corona

International Nuclear Information System (INIS)

Ensley, D.L.

1979-07-01

Approximate time dependent solutions for surface velocities and potentials are given for a plane polarized microwave field confining a hot, over-dense plasma corona. Steady state solutions to Poissons' equation can be applied to the time dependent case, provided transit time effects are included. The product of ion pressure and potential wave (surface) velocity gives an average heating rate approx. 7/32 NKT 0 V/sub theta/ directly to the ions

Energy confinement in JT-60 lower hybrid current driven plasmas

International Nuclear Information System (INIS)

Ushigusa, K.; Imai, T.; Naito, O.; Ikeda, Y.; Tsuji, S.; Uehara, K.

1990-01-01

The energy confinement in high power lower hybrid current driven (LHCD) plasmas has been studied in the JT-60 tokamak. At a plasma current of 1 MA, the diamagnetically estimated energy confinement time in LHCD plasmas has almost the same value as the confinement time in ohmically heated plasmas at n-bar e ∼ 1.0x10 19 m -3 . The confinement time of high power LHCD plasmas (P LH E varies as to P LH α n e β I p 0 with α + β ∼ -0.3. (author). Letter-to-the-editor. 12 refs, 5 figs

Characteristics of confining ohm-heated plasma in TRIAM-IM

International Nuclear Information System (INIS)

Hatae, Takaki; Yamagajyo, Takashi; Kawasaki, Shoji; Jotaki, Eriko; Fujita, Takaaki; Nakamura, Kazuo; Nakamura, Yukio; Ito, Satoshi

1994-01-01

In the initial experiment after the increase of the power of ohm heating power source for the superconducting strong magnetic field tokamak, TRIAM-IM, the measurement of the electron temperature distribution, ion temperature distribution and beam average electron density of ohm-heated plasma was carried out. By analyzing the experimental results, the dependence of the accumulated energy obtained from the temperature distribution and the time of energy confinement of beam average electron density became clear. Especially the time of energy confinement increased in proportion to the increase of beam average electron density when it is 6.5 x 10 12 /m 2 , and it was found that the time of energy confinement conforms to the Neo-Alcator proportional law. Moreover, by solving the heat transport equation for ions, the radial distribution of thermal diffusion coefficient for ions was calculated, and compared with that obtained by the new classic theory. As the result, it was found that the TRIAM-IM has ion confinement characteristics equivalent to those of other medium tokamaks. The experiment of producing ohm-heated plasma, the fitting of electron temperature and ion temperature, the density dependence of temperature, accumulated energy and the time of energy confinement, the time of energy confinement and the Neo-Alcator proportional law, the energy balance of ions and so on are reported. (K.I.)

Impact of hydrogen fuelling on confinement properties in radiative improved mode

International Nuclear Information System (INIS)

Kalupin, D; Dumortier, P; Messiaen, A; Tokar, M Z; Unterberg, B; Verdoolaege, Geert; Wassenhove, G Van; Weynants, R

2003-01-01

The radiative improved (RI) mode at TEXTOR is a high confinement regime, which is obtained by the seeding of neon into deuterium plasmas. Recent experiments were aimed to study the influence of external gas fuelling on the confinement properties of the RI mode. In particular, it was found that a hydrogen puff into such plasmas leads to lower confinement compared with the discharges fuelled with the same amount of deuterium gas. This paper attempts to explain the reduction of confinement in RI plasmas with an external hydrogen puff and its relation to the level of impurity concentration, which is a critical parameter for RI mode confinement

Modèle de confinement pour les colonnes de section circulaire en béton armé confiné avec des enveloppes en polymère renforcé de fibres de carbone Confinement model for circular RC columns wrapped with CFRP composite

Directory of Open Access Journals (Sweden)

Benzaid R.

2012-09-01

Full Text Available Un programme experimental comprenant des essais sur 30 cylindres 160×320 mm a ete mene en vue de determiner le gain de resistance et de ductilite du beton confine par collage externe de tissu de polymere renforce de fibres de carbone (PRFC. Les variables etudiees sont la resistance a la compression du beton non confine f’co, le niveau de confinement, exprime par le nombre de plis de PRFC applique aux eprouvettes. La deformation circonferentielle a la rupture du composite PRF et l’feffet de la pression de confinement laterale effective de l’fenveloppe composite ont ete egalement etudies. Pour l’fensemble des specimens testes, l’faugmentation de la rigidite du confinement entraine a la fois une augmentation significative de la resistance a la compression axiale et de la ductilite des specimens en beton confine avec des PRFC par rapport aux specimens en beton non confine. Base sur les resultats experimentaux, un modele de confinement pratique est propose pour predire la resistance a la compression maximale du beton confine avec des materiaux composites (f’cc et la deformation axiale correspondante (εcc. The present paper deals with the analysis of experimental results, in terms of load carrying capacity and strains, obtained from tests on plain- and reinforced- concrete (RC cylinder, strengthened with external carbon-fiber-reinforced polymer (CFRP. The parameters considered are the number of composite layers, the compressive strength of unconfined concrete. The effective circumferential FRP failure strain and the effect of the effective lateral confining pressure were investigated. Totally thirty cylinders (160×320 mm were subjected to axial compression which includes control specimens. All the test specimens were loaded to failure in axial compression and the behaviour of the specimens in the axial and transverse directions was investigated. Test results shown that the CFRP wrap increases the strength and ductility of reinforced

Low-Resolution Modeling of Dense Drainage Networks in Confining Layers.

Science.gov (United States)

Pauw, P S; Van der Zee, S E A T M; Leijnse, A; Delsman, J R; De Louw, P G B; De Lange, W J; Oude Essink, G H P

2015-01-01

Groundwater-surface water (GW-SW) interaction in numerical groundwater flow models is generally simulated using a Cauchy boundary condition, which relates the flow between the surface water and the groundwater to the product of the head difference between the node and the surface water level, and a coefficient, often referred to as the "conductance." Previous studies have shown that in models with a low grid resolution, the resistance to GW-SW interaction below the surface water bed should often be accounted for in the parameterization of the conductance, in addition to the resistance across the surface water bed. Three conductance expressions that take this resistance into account were investigated: two that were presented by Mehl and Hill (2010) and the one that was presented by De Lange (1999). Their accuracy in low-resolution models regarding salt and water fluxes to a dense drainage network in a confined aquifer system was determined. For a wide range of hydrogeological conditions, the influence of (1) variable groundwater density; (2) vertical grid discretization; and (3) simulation of both ditches and tile drains in a single model cell was investigated. The results indicate that the conductance expression of De Lange (1999) should be used in similar hydrogeological conditions as considered in this paper, as it is better taking into account the resistance to flow below the surface water bed. For the cases that were considered, the influence of variable groundwater density and vertical grid discretization on the accuracy of the conductance expression of De Lange (1999) is small. © 2014, National GroundWater Association.

General approach to polymer chains confined by interacting boundaries.

Science.gov (United States)

Freed, Karl F; Dudowicz, Jacek; Stukalin, Evgeny B; Douglas, Jack F

2010-09-07

Polymer chains, confined to cavities or polymer layers with dimensions less than the chain radius of gyration, appear in many phenomena, such as gel chromatography, rubber elasticity, viscolelasticity of high molar mass polymer melts, the translocation of polymers through nanopores and nanotubes, polymer adsorption, etc. Thus, the description of how the constraints alter polymer thermodynamic properties is a recurrent theoretical problem. A realistic treatment requires the incorporation of impenetrable interacting (attractive or repulsive) boundaries, a process that introduces significant mathematical complications. The standard approach involves developing the generalized diffusion equation description of the interaction of flexible polymers with impenetrable confining surfaces into a discrete eigenfunction expansion, where the solutions are normally truncated at the first mode (the "ground state dominance" approximation). This approximation is mathematically well justified under conditions of strong confinement, i.e., a confinement length scale much smaller than the chain radius of gyration, but becomes unreliable when the polymers are confined to dimensions comparable to their typically nanoscale size. We extend a general approach to describe polymers under conditions of weak to moderate confinement and apply this semianalytic method specifically to determine the thermodynamics and static structure factor for a flexible polymer confined between impenetrable interacting parallel plate boundaries. The method is first illustrated by analyzing chain partitioning between a pore and a large external reservoir, a model system with application to chromatography. Improved agreement is found for the partition coefficients of a polymer chain in the pore geometry. An expression is derived for the structure factor S(k) in a slit geometry to assist in more accurately estimating chain dimensions from scattering measurements for thin polymer films.

Thermodynamics of partially confined Fermi gases at low temperature

International Nuclear Information System (INIS)

Toms, David J

2004-01-01

We examine the behaviour of non-interacting Fermi gases at low temperature. If there is a confining potential present the thermodynamic behaviour is altered from the familiar results for the unconfined gas. The role of de Haas-van Alphen type oscillations that are a consequence of the confining potential is considered. Attention is concentrated on the behaviour of the chemical potential and the specific heat. Results are compared and contrasted with those for an unconfined and a totally confined gas

Instability of confined water films between elastic surfaces.

Science.gov (United States)

de Beer, Sissi; 't Mannetje, Dieter; Zantema, Sietske; Mugele, Frieder

2010-03-02

We investigated the dynamics of nanometer thin water films at controlled ambient humidity adsorbed onto two atomically smooth mica sheets upon rapidly bringing the surfaces into contact. Using a surface forces apparatus (SFA) in imaging mode, we found that the water films break up into a distribution of drops with a typical thickness of a few nanometers and a characteristic lateral size and spacing of several micrometers. Whereas the characteristic length is found to be independent of the ambient humidity, the characteristic time of the breakup decreases from approximately 1 to 0.01 s with increasing humidity. The existence of characteristic length and time scales shows that this breakup is controlled by an instability rather than a conventional nucleation and growth mechanism for SFA experiments. These findings cannot be explained by a dispersion-driven instability mechanism. In contrast, a model involving the elastic energies for the deformation of both the mica sheets and the underlying glue layer correctly reproduces the scaling of the characteristic length and time with humidity.

Confined-but-Connected Quantum Solids via Controlled Ligand Displacement

KAUST Repository

Baumgardner, William J.; Whitham, Kevin; Hanrath, Tobias

2013-01-01

Confined-but-connected quantum dot solids (QDS) combine the advantages of tunable, quantum-confined energy levels with efficient charge transport through enhanced electronic interdot coupling. We report the fabrication of QDS by treating self

CCSD(T) calculations of stabilities and properties of confined systems

Energy Technology Data Exchange (ETDEWEB)

Holka, F.; Urban, M. [Slovak University of Technology in Bratislava, Faculty of Materials Science and Technology in Trnava, Institute of Materials Science, Bottova 25, SK-917 24 Trnava (Slovakia); Melicherčík, M.; Neogrády, P. [Department of Physical and Theoretical Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina, SK-842 15 Bratislava (Slovakia); Paldus, J. [Department of Applied Mathematics, University of Waterloo, N2L 3G1, Ontario (Canada)

2015-01-22

We analyze energies, electron affinities and polarizabilities of small anions exposed to an external confinement. The second electron in free O{sup 2−} and S{sup 2−} anions is unbound. We investigate the stabilizing effect of the spherical harmonic-oscillator confining potential ω. on these anions employing the Hartree-Fock stability analysis as introduced by Čížek and Paldus. With increasing strength of the external harmonic-oscillator confinement potential ω the broken symmetry (BS) solutions are systematically eliminated. For ω larger than 0.1 all BS solutions for O{sup 2−} disappear. For ω larger than 0.13 the CCSD(T) energy of O{sup 2−} becomes more negative than the energy of the singly charged O{sup −} anion. We relate the harmonic-oscillator confining potential to a crystalline environment in which the O{sup 2−} and S{sup 2−} anions are stable. We also present a model allowing calculations of the in-crystal polarizabilities of anions. The model is based on CCSD(T) calculations of static polarizabilities of selected anions exposed to the spherical harmonic-oscillator confining potential ω This artificial confinement potential ω is then related to the ionic radii of the cation in representative crystal lattices. We investigate the polarizability of O{sup 2−} and S{sup 2−} anions in MgO, MgS, CaO, CaS, SrO, SrS, BaO and BaS crystals. We compare our results with alternative models for in-crystal polarizabilities. External confinement also stabilizes the uracil anion U{sup −}, as is shown by calculations with a stepwise micro-hydration of U{sup −}. Upon hydration is the CCSD(T) adiabatic electron affinity (AEA) of uracil enhanced by about 250 up to 570 meV in comparison with AEA of the isolated molecule, depending on the geometry of the hydrated uracil anion complex. We tried to find an analogy of the stabilization effect of the external confinement on the otherwise unstable anions. In uracil and its anion is the external

Field reversal experiments (FRX). [Equilibrium, confinement, and stability

Energy Technology Data Exchange (ETDEWEB)

Linford, R.K.; Armstrong, W.T.; Platts, D.A.; Sherwood, E.G.

1978-01-01

The equilibrium, confinement, and stability properties of the reversed-field configuration (RFC) are being studied in two theta-pinch facilities. The RFC is an elongated toroidal plasma confined in a purely poloidal field geometry. The open field lines of the linear theta pinch support the closed-field RFC much like the vertical field centers the toroidal plasma in a tokamak. Depending on stability and confinement properties, the RFC might be used to greatly reduce the axial losses in linear fusion devices such as mirrors, theta pinches, and liners. The FRX systems produce RFC's with a major radius R = 2-6 cm, minor radius a approximately 2 cm, and a total length l approximately 35 cm. The observed temperatures are T/sub e/ approximately 100 eV and T/sub i/ = 150-350 eV with a peak density n approximately 2 x 10/sup 15/ cm/sup -3/. After the plasma reaches equilibrium, the RFC remains stable for up to 30 ..mu..s followed by the rapid growth of the rotational m = 2 instability, which terminates the confinement. During the stable equilibrium, the particle and energy confinement times are more than 10 times longer than in an open-field system. The behavior of the m = 2 mode qualitatively agrees with the theoretically predicted instability for rotational velocities exceeding some critical value.

Gate-defined Quantum Confinement in Suspended Bilayer Graphene

Science.gov (United States)

Allen, Monica

2013-03-01

Quantum confined devices in carbon-based materials offer unique possibilities for applications ranging from quantum computation to sensing. In particular, nanostructured carbon is a promising candidate for spin-based quantum computation due to the ability to suppress hyperfine coupling to nuclear spins, a dominant source of spin decoherence. Yet graphene lacks an intrinsic bandgap, which poses a serious challenge for the creation of such devices. We present a novel approach to quantum confinement utilizing tunnel barriers defined by local electric fields that break sublattice symmetry in suspended bilayer graphene. This technique electrostatically confines charges via band structure control, thereby eliminating the edge and substrate disorder that hinders on-chip etched nanostructures to date. We report clean single electron tunneling through gate-defined quantum dots in two regimes: at zero magnetic field using the energy gap induced by a perpendicular electric field and at finite magnetic fields using Landau level confinement. The observed Coulomb blockade periodicity agrees with electrostatic simulations based on local top-gate geometry, a direct demonstration of local control over the band structure of graphene. This technology integrates quantum confinement with pristine device quality and access to vibrational modes, enabling wide applications from electromechanical sensors to quantum bits. More broadly, the ability to externally tailor the graphene bandgap over nanometer scales opens a new unexplored avenue for creating quantum devices.

Computer simulation of confined liquid crystal dynamics

International Nuclear Information System (INIS)

Webster, R.E.

2001-11-01

Results are presented from a series of simulations undertaken to determine whether dynamic processes observed in device-scale liquid crystal cells confined between aligning substrates can be simulated in a molecular system using parallel molecular dynamics of the Gay-Berne model. In a nematic cell, on removal of an aligning field, initial near-surface director relaxation can induce flow, termed 'backflow' in the liquid. This, in turn, can cause director rotation, termed 'orientational kickback', in the centre of the cell. Simulations are performed of the relaxation in nematic systems confined between substrates with a common alignment on removal of an aligning field. Results show /that relaxation timescales of medium sized systems are accessible. Following this, simulations are performed of relaxation in hybrid aligned nematic systems, where each surface induces a different alignment. Flow patterns associated with director reorientation are observed. The damped oscillatory nature of the relaxation process suggests that the behaviour of these systems is dominated by orientational elastic forces and that the observed director motion and flow do not correspond to the macroscopic processes of backflow and kickback. Chevron structures can occur in confined smectic cells which develop two domains of equal and opposite layer tilt on cooling. Layer lilting is thought to be caused by a need to reconcile a mismatch between bulk and surface smectic layer spacing. Here, simulations are performed of the formation of structures in confined smectic systems where layer tilt is induced by an imposed surface pretilt. Results show that bookshelf, chevron and tilled layer structures are observable in a confined Gay-Berne system. The formation and stability of the chevron structure are shown to be influenced by surface slip. (author)

Pressure Dependence of the Liquid-Liquid Phase Transition of Nanopore Water Doped Slightly with Hydroxylamine, and a Phase Behavior Predicted for Pure Water

Science.gov (United States)

Nagoe, Atsushi; Iwaki, Shinji; Oguni, Masaharu; Tôzaki, Ken-ichi

2014-09-01

Phase transition behaviors of confined pure water and confined water doped with a small amount of hydroxylamine (HA) with a mole fraction of xHA = 0.03 were examined by high-pressure differential thermal analyses at 0.1, 50, 100, and 150 MPa; the average diameters of silica pores used were 2.0 and 2.5 nm. A liquid-liquid phase transition (LLPT) of the confined HA-doped water was clearly observed and its pressurization effect could be evaluated, unlike in the experiments on undoped water. It was found that pressurization causes the transition temperature (Ttrs) to linearly decrease, indicating that the low-temperature phase has a lower density than the high-temperature one. Transition enthalpy (ΔtrsH) decreased steeply with increasing pressure. Considering the linear decrease in Ttrs with increasing pressure, the steep decrease in ΔtrsH indicates that the LLPT effect of the HA-doped water attenuates with pressure. We present a new scenario of the phase behavior concerning the LLPT of pure water based on the analogy from the behavior of slightly HA-doped water, where a liquid-liquid critical point (LLCP) and a coexistence line are located in a negative-pressure regime but not in a positive-pressure one. It is reasonably understood that doping a small amount of HA into water results in negative chemical pressurization and causes the LLPT to occur even at ambient pressure.

Somersault of Paramecium in extremely confined environments

Science.gov (United States)

Jana, Saikat; Eddins, Aja; Spoon, Corrie; Jung, Sunghwan

2015-08-01

We investigate various swimming modes of Paramecium in geometric confinements and a non-swimming self-bending behavior like a somersault, which is quite different from the previously reported behaviors. We observe that Paramecia execute directional sinusoidal trajectories in thick fluid films, whereas Paramecia meander around a localized region and execute frequent turns due to collisions with adjacent walls in thin fluid films. When Paramecia are further constrained in rectangular channels narrower than the length of the cell body, a fraction of meandering Paramecia buckle their body by pushing on the channel walls. The bucking (self-bending) of the cell body allows the Paramecium to reorient its anterior end and explore a completely new direction in extremely confined spaces. Using force deflection method, we quantify the Young’s modulus of the cell and estimate the swimming and bending powers exerted by Paramecium. The analysis shows that Paramecia can utilize a fraction of its swimming power to execute the self-bending maneuver within the confined channel and no extra power may be required for this new kind of self-bending behavior. This investigation sheds light on how micro-organisms can use the flexibility of the body to actively navigate within confined spaces.

How proteins modify water dynamics

Science.gov (United States)

Persson, Filip; Söderhjelm, Pär; Halle, Bertil

2018-06-01

Much of biology happens at the protein-water interface, so all dynamical processes in this region are of fundamental importance. Local structural fluctuations in the hydration layer can be probed by 17O magnetic relaxation dispersion (MRD), which, at high frequencies, measures the integral of a biaxial rotational time correlation function (TCF)—the integral rotational correlation time. Numerous 17O MRD studies have demonstrated that this correlation time, when averaged over the first hydration shell, is longer than in bulk water by a factor 3-5. This rotational perturbation factor (RPF) has been corroborated by molecular dynamics simulations, which can also reveal the underlying molecular mechanisms. Here, we address several outstanding problems in this area by analyzing an extensive set of molecular dynamics data, including four globular proteins and three water models. The vexed issue of polarity versus topography as the primary determinant of hydration water dynamics is resolved by establishing a protein-invariant exponential dependence of the RPF on a simple confinement index. We conclude that the previously observed correlation of the RPF with surface polarity is a secondary effect of the correlation between polarity and confinement. Water rotation interpolates between a perturbed but bulk-like collective mechanism at low confinement and an exchange-mediated orientational randomization (EMOR) mechanism at high confinement. The EMOR process, which accounts for about half of the RPF, was not recognized in previous simulation studies, where only the early part of the TCF was examined. Based on the analysis of the experimentally relevant TCF over its full time course, we compare simulated and measured RPFs, finding a 30% discrepancy attributable to force field imperfections. We also compute the full 17O MRD profile, including the low-frequency dispersion produced by buried water molecules. Computing a local RPF for each hydration shell, we find that the

Chemical reactions confined within carbon nanotubes.

Science.gov (United States)

Miners, Scott A; Rance, Graham A; Khlobystov, Andrei N

2016-08-22

In this critical review, we survey the wide range of chemical reactions that have been confined within carbon nanotubes, particularly emphasising how the pairwise interactions between the catalysts, reactants, transition states and products of a particular molecular transformation with the host nanotube can be used to control the yields and distributions of products of chemical reactions. We demonstrate that nanoscale confinement within carbon nanotubes enables the control of catalyst activity, morphology and stability, influences the local concentration of reactants and products thus affecting equilibria, rates and selectivity, pre-arranges the reactants for desired reactions and alters the relative stability of isomeric products. We critically evaluate the relative advantages and disadvantages of the confinement of chemical reactions inside carbon nanotubes from a chemical perspective and describe how further developments in the controlled synthesis of carbon nanotubes and the incorporation of multifunctionality are essential for the development of this ever-expanding field, ultimately leading to the effective control of the pathways of chemical reactions through the rational design of multi-functional carbon nanoreactors.

Status of global energy confinement studies

International Nuclear Information System (INIS)

Kaye, S.M.; Bell, M.G.; DeBoo, J.C.; Waltz, R.; Greenwald, M.; Sigmar, D.

1990-02-01

Empirical scaling expressions, reflecting the parametric dependence of the L-mode energy confinement time, have been used not only as benchmarks for tokamak operation and theories of energy transport, but for predicting the performance of proposed tokamak devices. Several scaling expressions based on data from small-and medium-sized devices have done well in predicting performance in larger devices, although great uncertainty exists in extrapolating yet farther, into the ignition regime. Several approaches exist for developing higher confidence scaling expressions. These include reducing the statistical uncertainty by identifying and filling in gaps in the present database, making use of more sophisticated statistical techniques, and developing scalings for confinement regimes within which future devices will operate. Confidence in the scaling expressions will be increased still if the expressions can be more directly tied to transport physics theory. This can be done through the use of dimensionless parameters, better describing the edge and core confinement regimes separately, and by incorporating transport models directly into the scaling expressions. 50 refs., 5 figs., 3 tabs

Operational technology for greater confinement disposal

International Nuclear Information System (INIS)

Dickman, P.T.; Vollmer, A.T.; Hunter, P.H.

1984-12-01

Procedures and methods for the design and operation of a greater confinement disposal facility using large-diameter boreholes are discussed. It is assumed that the facility would be located at an operating low-level waste disposal site and that only a small portion of the wastes received at the site would require greater confinement disposal. The document is organized into sections addressing: facility planning process; facility construction; waste loading and handling; radiological safety planning; operations procedures; and engineering cost studies. While primarily written for low-level waste management site operators and managers, a detailed economic assessment section is included that should assist planners in performing cost analyses. Economic assessments for both commercial and US government greater confinement disposal facilities are included. The estimated disposal costs range from $27 to $104 per cubic foot for a commercial facility and from $17 to $60 per cubic foot for a government facility. These costs are based on average site preparation, construction, and waste loading costs for both contact- and remote-handled wastes. 14 figures, 22 tables

Results from deuterium-tritium tokamak confinement experiments

International Nuclear Information System (INIS)

Hawryluk, R.J.

1997-02-01

Recent scientific and technical progress in magnetic fusion experiments has resulted in the achievement of plasma parameters (density and temperature) which enabled the production of significant bursts of fusion power from deuterium-tritium fuels and the first studies of the physics of burning plasmas. The key scientific issues in the reacting plasma core are plasma confinement, magnetohydrodynamic (MHD) stability, and the confinement and loss of energetic fusion products from the reacting fuel ions. Progress in the development of regimes of operation which have both good confinement and are MHD stable have enabled a broad study of burning plasma physics issues. A review of the technical and scientific results from the deuterium-tritium experiments on the Joint European Torus (JET) and the Tokamak Fusion Test Reactor (TFTR) is given with particular emphasis on alpha-particle physics issues

Confinement and related transport in Extrap geometry

International Nuclear Information System (INIS)

Tendler, M.

1983-01-01

The properties of the plasma dynamic equilibrium are investigated for the Extrap magnetic confinement geometry. The temperatures achieved so far in the high-#betta# pinches are much lower than the predicted values. Here, it is shown that the particle containment in Extrap may be improved as compared to the other pinches due to the electrostatic confinement. An analytic solution for the profiles of the plasma parameters are found under the assumption that the energy is lost primarily in the radial direction by heat conduction and convection. An estimate of the radial particle confinement time is given, showing favourable scaling with plasma density and temperature. The conventional assumption of a uniform current density is shown to be unjustified in the case of an inhomogeneous electron temperature. An analytical expression is found for the pinch radius at different mechanisms of the heat transport. (orig.)

System and method of operating toroidal magnetic confinement devices

Science.gov (United States)

Chance, M.S.; Jardin, S.C.; Stix, T.H.; Grimm, R.C.; Manickam, J.; Okabayashi, M.

1984-08-30

This invention pertains to methods and arrangements for attaining high beta values in plasma confinement devices. More specifically, this invention pertains to methods for accessing the second stability region of operation in toroidal magnetic confinement devices.

Investigation of stress–strain models for confined high strength ...

Indian Academy of Sciences (India)

High strength concrete; confined concrete; stress–strain models; ... One of its advantages is the lessening column cross-sectional areas. It was ..... Ahmad S H, Shah S P 1982 Stress–strain curves of concrete confined by spiral reinforcement.

Hydric transfer in swelling clayey soils: influence of confinement; Transfert hydrique dans des sols argileux gonflants: influence du confinement

Energy Technology Data Exchange (ETDEWEB)

Rolland, S

2002-01-01

Description of imbibition and swelling mechanisms in clayey soils represents an important stake in different scientific domains such as agronomy, geotechnics or petroleum industry. The aim of the present work is to show the effects of hydro-mechanical couplings during imbibition in a swelling clayey medium, under different confinement conditions. Our material is a bentonite-silt mixture, prepared with a known water content and compacted with a double-piston technique. This method allows us to produce uniform soil samples, in terms of humidity and bulk density. Experiments related to bottom imbibition are then carried out for three types of mechanical boundary conditions (free, oedometric, fixed volume). The non-intrusive dual-energy gamma-ray technique is used to assess the local variation of bulk density and humidity. Finally, the three imbibition kinetics are compared for each experiment in terms of hydraulic diffusivity, described in a Lagrangian way. (author)

Effects of confinement in meso-porous silica and carbon nano-structures

International Nuclear Information System (INIS)

Leon, V.

2006-07-01

Physico-chemical properties of materials can be strongly modified by confinement because of the quantum effects that appear at such small length scales and also because of the effects of the confinement itself. The aim of this thesis is to show that both the nature of the confining material and the size of the pores and cavities have a strong impact on the confined material. We first show the effect of the pore size of the host meso-porous silica on the temperature of the solid-solid phase transition of silver selenide, a semiconducting material with enhanced magnetoresistive properties under non-stoichiometric conditions. Narrowing the pores from 20 nm to 2 nm raises the phase transition temperature from 139 C to 146 C. This result can be explained by considering the interaction between the confining and confined materials as a driving force. The effects of confinement are also studied in the case of hydrogen and deuterium inside cavities of organized carbon nano-structures. The effects that appear in the adsorption/desorption cycles are much stronger with carbon nano-horns as the host material than with C60 pea-pods and single-walled carbon nano-tubes. (author)

Confining but chirally symmetric dense and cold matter

International Nuclear Information System (INIS)

Glozman, L. Ya.

2012-01-01

The possibility for existence of cold, dense chirally symmetric matter with confinement is reviewed. The answer to this question crucially depends on the mechanism of mass generation in QCD and interconnection of confinement and chiral symmetry breaking. This question can be clarified from spectroscopy of hadrons and their axial properties. Almost systematical parity doubling of highly excited hadrons suggests that their mass is not related to chiral symmetry breaking in the vacuum and is approximately chirally symmetric. Then there is a possibility for existence of confining but chirally symmetric matter. We clarify a possible mechanism underlying such a phase at low temperatures and large density. Namely, at large density the Pauli blocking prevents the gap equation to generate a solution with broken chiral symmetry. However, the chirally symmetric part of the quark Green function as well as all color non-singlet quantities are still infrared divergent, meaning that the system is with confinement. A possible phase transition to such a matter is most probably of the first order. This is because there are no chiral partners to the lowest lying hadrons.

Molecular modeling in confined polymer and biomembrane systems

Directory of Open Access Journals (Sweden)

Jayeeta Ghosh

2009-07-01

Full Text Available The computational study of soft materials under confinement for bio- and nanotechnology still poses significantchallenges but has come a long way in the last decade. It is possible to realistically model and understand the fundamentalmechanisms which are at play if soft materials are confined to nanometer dimensions. Here, we present several recentexamples of such studies. Thin polymer films are abundantly used as friction modifiers or steric stabilizers. We show howsystematic modeling can shed light on the interplay between entropic and energetic interactions. Thin glassy films arecritical for the success of nanolithography. For that we have to understand the effect of confinement on the glass transitionbehavior in order to guarantee the stability and integrity of the lithographic masks. Simulations aim to understand the fundamental differences in the densities of states of glass formers in bulk and under confinement. With the advent of bionanotechnology the structure and phase behavior of lipid membranes as models for cellular membranes at the nano scale length is of importance due to implications in understanding the role of the lipids in biochemical membrane processes.

Quantum cascade laser spectroscopy of OCS isotopologues in 4He nanodroplets: A test of adiabatic following for a heavy rotor

Science.gov (United States)

Faulkner, Ty; Miller, Isaac; Raston, Paul L.

2018-01-01

We report high-resolution infrared spectra of OCS isotopologues embedded in helium nanodroplets that were recorded with a newly built spectrometer. For the normal isotopologue, we observed the relatively weak third bending overtone band, in addition to new high J transitions in the C-O stretching fundamental, which has previously been investigated by diode laser spectroscopy [S. Grebenev et al., J. Chem. Phys. 112, 4485 (2000)]. Similar to the gas phase, the overtone band is (only) 45 cm-1 higher in energy than the fundamental, and this leads to additional broadening due to rapid vibrational relaxation that is accompanied by the creation of real/virtual phonon excitations. We also observed spectra in the C-O stretching fundamental for several minor isotopologues of OCS, including 18OCS, O13CS, and OC33S, in addition to some new peaks for OC34S. A rovibrational analysis allowed for determination of the moment of inertia of helium (ΔIHe) that couples to the rotation of OCS for each isotopologue. In the context of the adiabatic following approximation, the helium density structure that follows the rotation of OCS should essentially remain unchanged between the isotopologues, i.e., there should be no dependence of ΔIHe on the gas phase moment of inertia of OCS (IG). While this behavior was expected for the "heavy" OCS rotor investigated here, we instead found an approximately linear 1:1 relation between ΔIHe and IG, which suggests partial breakdown of the adiabatic following approximation, making OCS the heaviest molecule for which evidence for this effect has been obtained.

Confinement improvement with magnetic levitation of a superconducting dipole

International Nuclear Information System (INIS)

Garnier, D.T.; Mauel, M.E.; Boxer, A.C.; Ellsworth, J.L.; Kesner, J.

2009-01-01

We report the first production of high beta plasma confined in a fully levitated laboratory dipole using neutral gas fuelling and electron cyclotron resonance heating. As compared with previous studies in which the internal coil was supported, levitation results in improved confinement that allows higher-density, higher-beta discharges to be maintained at significantly reduced gas fuelling. Contrary to previous supported dipole plasma results which had the stored energy consisting in a hot electron population, a significant plasma stored energy is shown to reside in the bulk plasma. By eliminating supports used in previous studies, cross-field transport becomes the main loss channel for both the hot and the background species. This leads to a significant improvement in bulk plasma confinement and a dramatic peaking of the density profile. Improved particle confinement assures stability of the hot electron component at reduced neutral pressure.

Behavior of FRP-Confined Concrete-Filled Steel Tube Columns

Directory of Open Access Journals (Sweden)

Yiyan Lu

2014-05-01

Full Text Available This paper presents the results of an experimental study into the behavior of concrete-filled steel tube columns confined by fiber-reinforced polymer (FRP. Eleven columns were tested to investigate the effects of the FRP layer number, the thickness of the steel tube and concrete strength on their load capacity and axial deformation capacity. The experimental results indicated that the FRP wrap can effectively confine the concrete expansion and delay the local buckling of the steel tube. Both the load capacity and the axial deformation capacity of concrete-filled steel tube columns can be substantially enhanced with FRP confinement. A model is proposed to predict the load capacity of the FRP-confined concrete-filled steel tube columns. The predicted results are generally in good agreement with the experimental ones obtained in this study and in the literature.

Shape and 'gap' effects on the behavior of variably confined concrete

International Nuclear Information System (INIS)

Harries, Kent A.; Carey, Shawn A.

2003-01-01

Factors affecting the behavior of variably confined concrete are presented. The effect of debonding the fiber-reinforced polymer (FRP) jacket to the concrete substrate and providing a gap between the concrete and confining jacket is investigated. A second parameter--the shape of the cross section--is also investigated. An experimental program involving the compression testing of standard cylinders and similarly sized square specimens having external FRP jackets providing passive confinement is presented. Factors affecting jacket efficiency and the appropriateness of factors accounting for specimen shape are determined experimentally and discussed. The provision of a gap affected the axial stress at which the confining jacket was engaged, resulting in a reduced maximum attainable concrete strength. The jacket efficiency was not affected by the provision of the gap. The shape of the specimens was observed to affect the level of confinement generated. Square specimens exhibit lower confinement levels than circular specimens having the same jacket

Automated entry technologies for confined space work activities: A survey.

Science.gov (United States)

Botti, Lucia; Ferrari, Emilio; Mora, Cristina

2017-04-01

Work in confined spaces poses a significant risk to workers and rescuers involved in the emergency response when an accident occurs. Despite several standards and regulations define the safety requirements for such activities, injuries, and fatalities still occur. Furthermore, the on-site inspections after accidents often reveal that both employers and employees fail to implement safe entry procedures. Removing the risk is possible by avoiding the worker entry, but many activities require the presence of the operator inside the confined space to perform manual tasks. The following study investigates the available technologies for hazardous confined space work activities, e.g., cleaning, inspecting, and maintenance tasks. The aim is to provide a systematic review of the automated solutions for high-risk activities in confined spaces, considering the non-man entry as the most effective confined space safety strategy. Second, this survey aims to provide suggestions for future research addressing the design of new technologies. The survey consists of about 60 papers concerning innovative technologies for confined space work activities. The document review shows that several solutions have been developed and automation can replace the workers for a limited number of hazardous tasks. Several activities still require the manual intervention due to the complex characteristics of confined spaces, e.g., to remove the remains of the automatic cleaning process from the bottom of a tank. The results show that available technologies require more flexibility to adapt to such occupational environments and further research is needed.