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Sample records for adiabatic decompression melting

  1. A metastable liquid melted from a crystalline solid under decompression

    DOE PAGES

    Lin, Chuanlong; Smith, Jesse S.; Sinogeikin, Stanislav V.; ...

    2017-01-23

    A metastable liquid may exist under supercooling, sustaining the liquid below the melting point such as supercooled water and silicon. It may also exist as a transient state in solid–solid transitions, as demonstrated in recent studies of colloidal particles and glass-forming metallic systems. One important question is whether a crystalline solid may directly melt into a sustainable metastable liquid. By thermal heating, a crystalline solid will always melt into a liquid above the melting point. Here we report that a high-pressure crystalline phase of bismuth can melt into a metastable liquid below the melting line through a decompression process. Themore » decompression-induced metastable liquid can be maintained for hours in static conditions, and transform to crystalline phases when external perturbations, such as heating and cooling, are applied. It occurs in the pressure–temperature region similar to where the supercooled liquid Bi is observed. Finally, akin to supercooled liquid, the pressure-induced metastable liquid may be more ubiquitous than we thought.« less

  2. A metastable liquid melted from a crystalline solid under decompression

    NASA Astrophysics Data System (ADS)

    Lin, Chuanlong; Smith, Jesse S.; Sinogeikin, Stanislav V.; Kono, Yoshio; Park, Changyong; Kenney-Benson, Curtis; Shen, Guoyin

    2017-01-01

    A metastable liquid may exist under supercooling, sustaining the liquid below the melting point such as supercooled water and silicon. It may also exist as a transient state in solid-solid transitions, as demonstrated in recent studies of colloidal particles and glass-forming metallic systems. One important question is whether a crystalline solid may directly melt into a sustainable metastable liquid. By thermal heating, a crystalline solid will always melt into a liquid above the melting point. Here we report that a high-pressure crystalline phase of bismuth can melt into a metastable liquid below the melting line through a decompression process. The decompression-induced metastable liquid can be maintained for hours in static conditions, and transform to crystalline phases when external perturbations, such as heating and cooling, are applied. It occurs in the pressure-temperature region similar to where the supercooled liquid Bi is observed. Akin to supercooled liquid, the pressure-induced metastable liquid may be more ubiquitous than we thought.

  3. A metastable liquid melted from a crystalline solid under decompression

    PubMed Central

    Lin, Chuanlong; Smith, Jesse S.; Sinogeikin, Stanislav V.; Kono, Yoshio; Park, Changyong; Kenney-Benson, Curtis; Shen, Guoyin

    2017-01-01

    A metastable liquid may exist under supercooling, sustaining the liquid below the melting point such as supercooled water and silicon. It may also exist as a transient state in solid–solid transitions, as demonstrated in recent studies of colloidal particles and glass-forming metallic systems. One important question is whether a crystalline solid may directly melt into a sustainable metastable liquid. By thermal heating, a crystalline solid will always melt into a liquid above the melting point. Here we report that a high-pressure crystalline phase of bismuth can melt into a metastable liquid below the melting line through a decompression process. The decompression-induced metastable liquid can be maintained for hours in static conditions, and transform to crystalline phases when external perturbations, such as heating and cooling, are applied. It occurs in the pressure–temperature region similar to where the supercooled liquid Bi is observed. Akin to supercooled liquid, the pressure-induced metastable liquid may be more ubiquitous than we thought. PMID:28112152

  4. Rapid decompression of seeded melts for materials processing

    NASA Astrophysics Data System (ADS)

    Qiu, Ning; Apfel, Robert E.

    1995-05-01

    A novel processing approach and experimental design to achieve as-cast bulk amorphous materials are investigated. By sudden decompression of a melt that is seeded with a volatile liquid, the dispersed ``foaming'' liquid vaporizes, taking its latent heat of vaporization from the melt, thereby homogeneously cooling the melt. Due to a high decompression rate, a sufficient cooling rate may be produced to yield an amorphous solid foam. The resulting ``foam glass'' is expected to be an open solid bulk structure that may possess glass properties and low density. These foam glass materials should be free of structural defects, and may have many potential applications. The ultimate goal for this form glass processing is to produce bulk amorphous metallic solids. This approach differs from other processes used in the production of metals with a porous structure. A description of the approach, the processing design and techniques, as well as some evaluation of foam processing with the organic p-terphenyl as a sample material are presented. Foam (p-terphenyl) is an open, porous, and yet interconnected structure, and can be made with a density as low as 12% of the original density of p-terphenyl. Extension of this principle to foam metallic glass processing is anticipated. Design of a more sophisticated apparatus for metal processing, currently in progress, is discussed.

  5. Measurements of the Effect of Adiabat on Shell Decompression in Direct-Drive Implosions on OMEGA

    NASA Astrophysics Data System (ADS)

    Michel, D. T.; Hu, S. X.; Radha, P. B.; Davis, A. K.; Craxton, R. S.; Glebov, V. Yu.; Goncharov, V. N.; Igumenshchev, I. V.; Stoeckl, C.; Froula, D. H.

    2016-10-01

    Measurements of the effect of adiabat (α) on the shell thickness were performed in direct-drive implosions. The maximum in-flight shell thickness was obtained using a novel technique where the outer and inner surfaces of the shell were simultaneously measured using self-emission images of the imploding target. When reducing the shell's adiabat from α = 6 to α = 4.5 , the shell thickness was measured to decrease from 75 μm to 60 μm, but when decreasing the adiabat further (α = 1.8), the shell thickness was measured to increase to 75 μm. The measured shell thickness, shell trajectories, neutron bang time, and neutron yield were reproduced by two-dimensional simulations that include laser imprint, nonlocal thermal transport, cross-beam energy transfer, and first-principles equation-of-state models. These results show that the decompression of the shell measured for low-adiabat implosions was a result of laser imprint. Additional information on the evolution of the density profile was obtained using x-ray radiography. The backlighter was created with six of the 60 OMEGA laser beams, with the pointings and energies of other beams adjusted to maintain a uniform implosion. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  6. Degassing of H2O in a phonolitic melt: A closer look at decompression experiments

    NASA Astrophysics Data System (ADS)

    Marxer, Holger; Bellucci, Philipp; Nowak, Marcus

    2015-05-01

    Melt degassing during magma ascent is controlled by the decompression rate and can be simulated in decompression experiments. H2O-bearing phonolitic melts were decompressed at a super-liquidus T of 1323 K in an internally heated argon pressure vessel, applying continuous decompression (CD) as well as to date commonly used step-wise decompression (SD) techniques to investigate the effect of decompression method on melt degassing. The hydrous melts were decompressed from 200 MPa at nominal decompression rates of 0.0028-1.7 MPa·s- 1. At final pressure (Pfinal), the samples were quenched rapidly at isobaric conditions with ~ 150 K·s- 1. The bubbles in the quenched samples are often deformed and dented. Flow textures in the glass indicate melt transport at high viscosity. We suggest that this observation is due to bubble shrinkage during quench. This general problem was mostly overlooked in the interpretation of experimentally degassed samples to date. Bubble shrinkage due to decreasing molar volume (Vm) of the exsolved H2O in the bubbles occurs during isobaric rapid quench until the melt is too viscous too relax. The decrease of Vm(H2O) during cooling at Pfinal of the experiments results in a decrease of the bubble volume by a shrinking factor Bs: At nominal decompression rates > 0.17 MPa·s- 1 and a Pfinal of 75 MPa, the decompression method has only minor influence on melt degassing. SD and CD result in high bubble number densities of 104-105 mm- 3. Fast P drop leads to immediate supersaturation with H2O in the melt. At such high nominal decompression rates, the diffusional transport of H2O is limited and therefore bubble nucleation is the predominant degassing process. The residual H2O contents in the melts decompressed to 75 MPa increase with nominal decompression rate. After homogeneous nucleation is triggered, CD rates ≤ 0.024 MPa·s- 1 facilitate continuous reduction of the supersaturation by H2O diffusion into previously nucleated bubbles. Bubble number

  7. Magma decompression rates during explosive eruptions of Kīlauea volcano, Hawaii, recorded by melt embayments

    NASA Astrophysics Data System (ADS)

    Ferguson, David J.; Gonnermann, Helge M.; Ruprecht, Philipp; Plank, Terry; Hauri, Erik H.; Houghton, Bruce F.; Swanson, Donald A.

    2016-10-01

    The decompression rate of magma as it ascends during volcanic eruptions is an important but poorly constrained parameter that controls many of the processes that influence eruptive behavior. In this study, we quantify decompression rates for basaltic magmas using volatile diffusion in olivine-hosted melt tubes (embayments) for three contrasting eruptions of Kīlauea volcano, Hawaii. Incomplete exsolution of H2O, CO2, and S from the embayment melts during eruptive ascent creates diffusion profiles that can be measured using microanalytical techniques, and then modeled to infer the average decompression rate. We obtain average rates of ~0.05-0.45 MPa s-1 for eruptions ranging from Hawaiian style fountains to basaltic subplinian, with the more intense eruptions having higher rates. The ascent timescales for these magmas vary from around ~5 to ~36 min from depths of ~2 to ~4 km, respectively. Decompression-exsolution models based on the embayment data also allow for an estimate of the mass fraction of pre-existing exsolved volatiles within the magma body. In the eruptions studied, this varies from 0.1 to 3.2 wt% but does not appear to be the key control on eruptive intensity. Our results do not support a direct link between the concentration of pre-eruptive volatiles and eruptive intensity; rather, they suggest that for these eruptions, decompression rates are proportional to independent estimates of mass discharge rate. Although the intensity of eruptions is defined by the discharge rate, based on the currently available dataset of embayment analyses, it does not appear to scale linearly with average decompression rate. This study demonstrates the utility of the embayment method for providing quantitative constraints on magma ascent during explosive basaltic eruptions.

  8. The fate of sulfide during decompression melting of peridotite - implications for sulfur inventory of the MORB-source depleted upper mantle

    NASA Astrophysics Data System (ADS)

    Ding, Shuo; Dasgupta, Rajdeep

    2017-02-01

    Magmatism at mid ocean ridges is one of the main pathways of S outflux from deep Earth to the surface reservoirs and is a critical step in the global sulfur cycle, yet our understanding of the behavior of sulfide during decompression melting of the upper mantle is incomplete. In order to constrain the sulfur budget of the mantle and reconcile the sulfur and chalcophile element budget of mantle partial melts parental to primitive mid-ocean ridge basalts (MORBs), here we developed a model to describe the behavior of sulfide and Cu during decompression melting by combining the pMELTS thermodynamic model and empirical sulfur contents at sulfide concentration (SCSS) models, taking into account the effect of the presence of Ni and Cu in sulfides on SCSS of mantle-derived melts. Calculation of SCSS along melting adiabat at mantle potential temperature of 1380 °C with variable initial S content in the mantle indicates that the complete consumption or partial survival of sulfide in the melting residue depends on initial S content and degree of melting. Primitive MORBs (Mg# > 60) with S and Cu mostly concentrated in 800-1000 ppm and 80-120 ppm are likely mixture of sulfide undersaturated high degree melts and sulfide saturated low degree melts derived from depleted peridotite containing 100-200 ppm S. Model calculations to capture the effects of variable mantle potential temperatures (1280-1420 °C) indicate that for a given abundance of sulfide in the mantle, hotter mantle consumes sulfide more efficiently than colder mantle owing to the effect of temperature in enhancing sulfide solubility in silicate melt, and higher mantle temperature stabilizing partial melt with higher FeO* and lower SiO2 and Al2O3, all of which generally enhance sulfide solubility. However, sulfide can still be exhausted by ∼ 10- 15% melting with bulk S of 100-150 ppm in the mantle when TP is as low as 1300 °C. We also show that although variation of DCuperidotite/ melt and initial Cu in the

  9. Timescales of bubble coalescence, outgassing, and foam collapse in decompressed rhyolitic melts

    NASA Astrophysics Data System (ADS)

    Martel, Caroline; Iacono-Marziano, Giada

    2016-04-01

    The timescale of degassing and outgassing in hydrous rhyolitic melts is investigated in a wide range of conditions by means of decompression experiments. The evolution of vesicularity, bubble diameter, and number density is characterized as a function of time either of decompression or spent at final pressure, in order to determine the effect of final pressure, temperature, syn- versus post-decompression degassing, melt composition, and microlites, on the timescale of bubble growth, coalescence, and outgassing. The result suggest that different bubble evolution and degassing-outgassing timescale corresponding to explosive and effusive eruption regimes can be cast in bulk viscosity (melt + bubbles; nbulk) versus decompression time (rather than path) space. The nbulk-time relationships defines three domains of (i) bubble nucleation and growth, restricted to short durations and high nbulk (< ˜0.03 h for nbulk ˜105-6Pa.s), (ii) equilibrium degassing with coalescence increasing from negligible (permeability > 10-13 m2) to extensive (permeability ˜10-11-12 m2), and (iii) outgassing, restricted to long durations and low nbulk(> ˜10 h for nbulk < 106 Pa.s; permeability >10-10 m2) that eventually leads to foam collapse. These findings are applied to the case studies of Mt Pelée and Mt Pinatubo to infer the transition from pumice to dense pyroclasts in volcanic eruptions and the possibility of evolving from an explosive Plinian eruption to an effusive dome-growth event by giving the vesicular magma enough time to outgas and collapse (i.e. hundreds to tens of hours for nbulk ˜105 to 104 Pa.s, respectively). We also show the drastic effect of microlites on re-arranging preexistent bubbles and potentially triggering a late nucleation event.

  10. Timescales of bubble coalescence, outgassing, and foam collapse in decompressed rhyolitic melts

    NASA Astrophysics Data System (ADS)

    Martel, Caroline; Iacono-Marziano, Giada

    2015-02-01

    The timescale of degassing and outgassing in hydrous rhyolitic melts is investigated in a wide range of conditions by means of decompression experiments. The evolution of vesicularity, bubble diameter, and number density is characterized as a function of time either of decompression or spent at final pressure, in order to determine the effect of final pressure, temperature, syn- versus post-decompression degassing, melt composition, and microlites, on the timescale of bubble growth, coalescence, and outgassing. The result suggests that different bubble evolution and degassing-outgassing timescale corresponding to explosive and effusive eruption regimes can be cast in bulk viscosity (melt + bubbles; ηbulk) versus decompression time (rather than path) space. The ηbulk-time relationship defines three domains of (i) bubble nucleation and growth, restricted to short durations and high ηbulk (< ∼ 0.03 h for ηbulk ∼105-6 Pas), (ii) equilibrium degassing with coalescence increasing from negligible (permeability >10-13m2) to extensive (permeability ∼10 - 11- 12m2), and (iii) outgassing, restricted to long durations and low ηbulk (> ∼ 10 h for ηbulk <106 Pas; permeability >10-10m2) that eventually leads to foam collapse. These findings are applied to the case studies of Mt Pelée and Mt Pinatubo to infer the transition from pumice to dense pyroclasts in volcanic eruptions and the possibility of evolving from an explosive Plinian eruption to an effusive dome-growth event by giving the vesicular magma enough time to outgas and collapse (i.e. hundreds to tens of hours for ηbulk ∼105 to 104 Pas, respectively). We also show the drastic effect of microlites on re-arranging preexistent bubbles and potentially triggering a late nucleation event.

  11. Cenozoic magmatism in the South China Basin: Decompression melting and implications of an enriched mantle source

    SciTech Connect

    Flower, M.F.J.; Kan Tu; Ming Zhang ); Guanghong Xie )

    1990-06-01

    A widespread eposide of interplate volcanism followed the cessation of seafloor spreading in the South China Basin (SCB), affecting the South China Sea, and fringing areas of southern China and Indochina. Geochemical data for basalts from South China Sea islands and seamounts, Hainan Island, and Taiwan define an enriched (Dupal-like) mantle domain yielding oceanic island basalt (OIB) suites with {Delta}7/4Pb = 2-13, {Delta}8/4Pb = 45-73, {sup 87}Sr/{sup 86}Sr > {approximately}0.70325, Th/Ta > 2, and Th/Ba > 0.02. Opening of the SCB resulted from disaggregation of the South China block in response to the Indo-Eurasian collision, a process involving at least one seafloor spreading episode, terminated by collision of microcontinents with the Philippines and Borneo. The lack of precursive flood basalt suggests that active mantle upwelling was not involved and that melting was a passive effect of lithosphere stretching. However, while mantle decompression at ambient stretching factors ({approximately}1.7-2.5) appears to permit melting on the observed scale, the enriched source may preclude such a simple mantle dynamic. Three alternatives are considered: (1) passive melting of a mature metasomatised boundary layer, (2) active melting of thermally eroded subcontinental lithosphere (deep enrichment) or metasomatised boundary layer (shallow enrichment), and (3) relict diapirs of pre-SCB and/or Java trench subduction slabs (intermediate/deep enrichment). These models are evaluated in terms of chemical and isotopic mass balances associated with the generation and movement of small melt fractions in depleted, nondepleted, and enriched mantle.

  12. Crystallization kinetics of alkali feldspars in cooling and decompression-induced crystallization experiments in trachytic melt

    NASA Astrophysics Data System (ADS)

    Arzilli, Fabio; Carroll, Michael R.

    2013-10-01

    Cooling and decompression experiments have been carried out on trachytic melts in order to investigate crystallization kinetics of alkali feldspar, the effect of the degree of undercooling ( ΔT = T liquidus - T experimental) and time on nucleation and crystal growth process. This experimental work gives us new data about crystallization kinetics of trachytic melts, and it that will be useful to better understand the natural system of Campi Flegrei volcanoes. Experiments have been conducted using cold seal pressure vessel apparatus, at pressure between 30 and 200 MPa, temperature between 750 and 855 °C, time between 7,200 and 57,600 s and redox condition close to the NNO +0.8 buffer. These conditions are ideal to reproducing pre- and syn-eruptive conditions of the Campi Flegrei volcanoes, where the "conditions" pertain to the complete range of pressures, temperatures and time at which the experiments were performed. Alkali feldspar is the main phase present in this trachyte, and its abundance can strongly vary with small changes in pressure, temperature and water content in the melt, implying appreciable variations in the textures and in the crystallization kinetics. The obtained results show that crystallization kinetics are strictly related to ΔT, time, final pressure, superheating (- ΔT) and water content in the melt. ΔT is the driving force of the crystallization, and it has a strong influence on nucleation and growth processes. In fact, the growth process dominates crystallization at small ΔT, whereas the nucleation dominates crystallization at large ΔT. Time also is an important variable during crystallization process, because long experiment durations involve more nucleation events of alkali feldspar than short experiment durations. This is an important aspect to understand magma evolution in the magma chamber and in the conduit, which in turn has strong effects on magma rheology.

  13. Bubble nucleation in H2O-CO2 bearing basaltic melts: results of high temperature decompression experiments

    NASA Astrophysics Data System (ADS)

    Le Gall, N.; Pichavant, M.; Burgisser, A.

    2012-12-01

    Previous experiments have shown that mechanisms of basalt degassing are strongly contrasted when gas bubbles are present or when they are absent. Thus, experimental information on the kinetics of bubble nucleation in basaltic melts is needed, and high temperature decompression experiments have been investigated. All experiments used PST-9 basaltic pumice from Stromboli as starting material. The sample was fused in air at 1400°C for 3h and then cylinders (l up to 10mm, d 2.5 and 5mm) were cored. Synthesis experiments were performed to produce the volatile-bearing melts to be used in the decompression experiments. Glass cores, distilled H2O and Ag2C2O4 were loaded in AuPd capsules. Three different H2O/CO2 were introduced, corresponding to XH2Oin=1 (#1: only H2O dissolved in glass), 0.55 (#2: high dissolved H2O/CO2), 0 (#3: low dissolved H2O/CO2). The synthesis experiments were ran at 1200°C during about 40h in an internally heated vessel pressurized with Ar-H2. The synthesized crystal- and bubble-free glasses were cut in 2 parts: one for the decompression experiments and the other for the analysis. Decompression experiments were conducted at a fast rate of 39kPa/s, exceptionally of 77.8kPa/s, at 1200°C from an initial pressure (Pin) of 200MPa and to final pressures (Pf) of 200, 150, 100 and 50MPa. Experiments to 25MPa are in progress. Each run included 3 capsules, corresponding to the 3 XH2Oin conditions of glass synthesis, allowing results for the 3 H2O/CO2 to be directly compared. Charges were rapid-quenched immediately after attainment of Pf. Textures were analyzed by X-ray microtomography, and volatile concentrations and spatial distributions in pre- and post-decompression glasses were determined by FTIR. Pre-decompression glasses have homogeneous volatile contents and distributions. They divide into 3 compositional groups consistent with their XH2Oin conditions of synthesis: group #1 (average H2O content=4.82wt%, average CO2 content=0ppm), group #2 (2.15wt

  14. Dependency of continental crustal rupture, decompression melt initiation and OCT architecture on lithosphere deformation modes during continental breakup: Numerical experiments

    NASA Astrophysics Data System (ADS)

    Jeanniot, L.; Kusznir, N. J.; Manatschal, G.

    2012-12-01

    During the continental breakup process, the initiation of sea-floor spreading requires both the rupture of the continental crust and the initiation of decompression melting. Using numerical experiments, we investigate how the deformation mode of continental lithosphere thinning and stretching controls the rupture of continental crust and lithospheric mantle, the onset of decompression melting and their relative timing. We use a two dimensional finite element viscous flow model to describe lithosphere and asthenosphere deformation. This flow field is used to advect lithosphere and asthenosphere material and temperature. Decompression melting is predicted using the parameterization scheme of Katz et al. (2003). Consistent with the observations of deformation processes occurring at slow spreading ocean ridges (Cannat, 1996), we assume that the topmost continental and oceanic lithosphere, corresponding to the cooler brittle seismogenic layer, deforms by extensional faulting (which we approximate to pure-shear deformation) and magmatic intrusion. Beneath this topmost lithosphere layer approximately 15-20 km thick, we assume that deformation occurs in response to passive upwelling and thermal and melt buoyancy driven small-scale convection. The relative contribution of these deformation components is parameterised by the ratio Vz/Vx, where Vx is the half spreading rate applied to the topmost lithosphere deformation and Vz is the upwelling velocity associated with the small scale convection. We use a series of numerical experiments to investigate the dependency of continental crust and lithosphere rupture, decompression melt initiation, rifted margin ocean-continent transition architecture and subsidence history on the half-spreading rate Vx, buoyancy driven upwelling rate Vz, the ratio Vz/Vx and upper lithosphere pure-shear width W. Based on the numerical experiment results we explore a polyphase evolution of deformation modes leading to continental breakup, sea

  15. Ocean Basalt Simulator version 1 (OBS1): Trace element mass balance in adiabatic melting of a pyroxenite-bearing peridotite

    NASA Astrophysics Data System (ADS)

    Kimura, Jun-Ichi; Kawabata, Hiroshi

    2015-01-01

    present a new numerical trace element mass balance model for adiabatic melting of a pyroxenite-bearing peridotite for estimating mantle potential temperature, depth of melting column, and pyroxenite fraction in the source mantle for a primary ocean basalt/picrite. The Ocean Basalt Simulator version 1 (OBS1) uses a thermodynamic model of adiabatic melting of a pyroxenite-bearing peridotite with experimentally/thermodynamically parameterized liquidus-solidus intervals and source mineralogy. OBS1 can be used to calculate a sequence of adiabatic melting with two melting models, including (1) melting of peridotite and pyroxenite sources with simple mixing of their fractional melts (melt-melt mixing model), and (2) pyroxenite melting, melt metasomatism in the host peridotite, and melting of the metasomatized peridotite (source-metasomatism model). OBS1 can be used to explore (1) the fractions of peridotite and pyroxenite, (2) mantle potential temperature, (3) pressure of termination of melting, (4) degree of melting, and (5) residual mode of the sources. In order to constrain these parameters, the model calculates a mass balance for 26 incompatible trace elements in the sources and in the generated basalt/picrite. OBS1 is coded in an Excel spreadsheet and runs with VBA macros. Using OBS1, we examine the source compositions and conditions of the mid-oceanic ridge basalts, Loihi-Koolau basalts in the Hawaiian hot spot, and Jurassic Shatsky Rise and Mikabu oceanic plateau basalts and picrites. The OBS1 model shows the physical conditions, chemical mass balance, and amount of pyroxenite in the source peridotite, which are keys to global mantle recycling.

  16. Ocean Basalt Simulator version 1 (OBS1): Trace element mass balance in adiabatic melting of a pyroxenite-bearing peridotite

    NASA Astrophysics Data System (ADS)

    Kimura, J. I.; Kawabata, H.

    2014-12-01

    We present a new numerical mass balance model for estimating the source conditions of a primary ocean basalt from adiabatic melting of a pyroxenite-bearing peridotite. The Ocean Basalt Simulator version 1 (OBS1) uses a thermodynamic model of adiabatic melting of a pyroxenite-bearing peridotite with experimentally parameterized liquidus-solidus and melting intervals and thermodynamically/experimentally parameterized source mineralogy of pyroxenite and peridotite. OBS1 uses a sequence of adiabatic melting with pyroxenite melting, melt metasomatism in the host peridotite, and melting of the metasomatized peridotite. OBS1 explores (1) the fractions of peridotite and pyroxenite, (2) mantle potential temperature Tp, (3) depth of termination of melting Pmt, (4) degree of melting F, and (5) residual mode Xa of the sources. The model also examines the mass balance of 26 incompatible trace elements in the sources and in the generated basalt. OBS1 can also calculate Sr-Nd-Hf-Pb isotope compositions in the sources and in the melt. OBS1 is coded in an Excel spreadsheet and runs with VBA macros. Using OBS1, we examine the source conditions of the mid oceanic ridge basalts (MORBs), plume-influenced ocean ridge basalts in Galápagos, Loihi-Loa-Koolau basalts in the Hawaiian hotspot, high-mu (HIMU) basalt from the St. Helena hotspot, and Shatsky Rise and Jurassic Mikabu oceanic plateau basalts and picrites. OBS1 is a unique model that provides an opportunity to examine the source mantle conditions using incompatible trace elements and relevant isotopes, which are key factors in global mantle recycling.

  17. Effect of water on mantle melting and magma differentiation, as modeled using Adiabat_1ph 3.0

    NASA Astrophysics Data System (ADS)

    Antoshechkina, P. M.; Asimow, P. D.; Hauri, E. H.; Luffi, P. I.

    2010-12-01

    MELTS [1] and pMELTS [2] are widely used for modeling hydrous magma differentiation and water-saturated mantle melting, respectively. In pHMELTS [3] the water species can partition into melt, pure vapor, and hydrous or nominally anhydrous minerals so that phase relations for water-undersaturated systems may also be constructed. Adiabat_1ph is a text-based front end to the (pH)MELTS algorithms; in version 3.0 (Antoshechkina and Asimow, this meeting) we have added tools to further explore the effect of water on melting and fractional crystallization. Asimow and coworkers developed two schemes for fractionation-correction of major and trace elements: a forward model that considers the effects of water, pressure, and fO2 on the liquid line of descent (LLD) [3] and a hybrid back- and forward-fractionation model that may be used for individual samples when trends are poorly defined [4]. An extensive melt inclusion dataset for the Mariana Trough [5] shows evidence for simultaneous fractionation and degassing, so we have adapted routines from [4] to cope with hydrous conditions. For H2O < 1.5 wt% the path predicted by the ‘reverse-fractionation’ algorithm passes from cotectic assimilation to olivine accumulation as MgO increases. Higher water contents lend themselves to the ‘amoeba’ routine that, given an initial estimate, varies the parental melt composition until isobaric forward fractionation yields a specified target [4]. The adiabat_1ph version is flexible in the choice of varied oxides and fO2 constraint, and offers optional fitting to the LLD of a whole suite. In test runs, using glass compositions from the 9N region of the East Pacific Rise, we optimize the primary melt composition for fixed initial H2O. A grid search gives the quality of LLD fit as a function of initial H2O and pressure of crystallization. The overall best-fit LLD model and our preferred LLD model (H2O-CO2 vapor saturation pressure and maximum measured H2O) are in excellent agreement

  18. Investigating Disequilibrium Degassing of H2O and CO2 in Rhyolitic Melts: New Insights from Cold-Seal Decompression Experiments

    NASA Astrophysics Data System (ADS)

    Johnson, E. R.; Wallace, P. J.

    2012-12-01

    Magmatic degassing, or the diffusion of volatiles once dissolved in the melt into a vapor phase, is a critical process that influences eruption explosivity and is in turn affected by magma ascent rate. Experimental research has demonstrated that rapid magma decompression rates can result in delayed, disequilibrium degassing of H2O when diffusion of H2O to bubbles is slow compared to the decompression rate (e.g., Mangan and Sisson, 2000). Although disequilibrium degassing has been documented through previous experimental work, much of the previous work has focused on single volatile (H2O-only) systems, with an emphasis on the effect of rapid ascent on bubble nucleation. Our research investigates disequilibrium degassing of multiple volatile components (CO2 and H2O) and the effects on water speciation (molecular H2O and hydroxyl) during decompression using cold-seal decompression experiments. Our experiments are on rhyolitic melts, though the results have implications for other magma types. The starting material is a powdered sample of Bishop Tuff high-silica rhyolite, to which 6 wt% H2O has been added along with varying amounts of CO2. Samples are held at high pressure and temperature (200 MPa and ~780 C) for at least 24 hours to ensure homogenization above the liquidus. Some samples are quenched after this time period (solubility experiments), and will serve as comparison for the decompression runs. In other experiments, after homogenization the pressure will be decreased at a range of decompression rates that correspond to rates expected for effusive, dome-forming eruptions to highly explosive eruptions, where disequilibrium degassing is most likely to occur. The quenched end-products of the experiments will be analyzed using Fourier Transform Infrared (FTIR) spectroscopy, allowing us to constrain not only the total H2O and CO2 contents, but also H2O speciation (H2O and OH-). In decompression experiments, glasses will be analyzed in transects with distance from

  19. Homogeneous bubble nucleation in H2O- and H2O-CO2-bearing basaltic melts: Results of high temperature decompression experiments

    NASA Astrophysics Data System (ADS)

    Le Gall, Nolwenn; Pichavant, Michel

    2016-11-01

    High pressure and temperature decompression experiments were conducted to provide experimental information on the conditions of homogeneous bubble nucleation in basaltic melts. Experiments were performed on H2O- and H2O-CO2-bearing natural melts from Stromboli. Three starting volatile compositions were investigated: series #1 (4.91 wt% H2O, no CO2), series #2 (2.37-2.45 wt% H2O, 901-1011 ppm CO2) and series #3 (0.80-1.09 wt% H2O, 840-923 ppm CO2). The volatile-bearing glasses were first synthesized at 1200 °C and 200 MPa, and second continuously decompressed in the pressure range 150-25 MPa and rapidly quenched. A fast decompression rate of 78 kPa/s (or 3 m/s) was applied to limit the water loss from the glass cylinder and the formation of a H2O-depleted rim. Post-decompression glasses were characterized texturally by X-ray microtomography. The results demonstrate that homogenous bubble nucleation requires supersaturation pressures (difference between saturation pressure and pressure at which homogeneous bubble nucleation is observed, ∆ PHoN) ≤ 50-100 MPa. ∆ PHoN varies with the dissolved CO2 concentration, from ≪ 50 MPa (no CO2, series #1) to ≤ 50 MPa (872 ± 45 ppm CO2, series #3) to < 100 MPa (973 ± 63 ppm CO2, series #2). In series #1 melts, homogeneous bubble nucleation occurs as two distinct events, the first at high pressure (200 < P < 150 MPa) and the second at low pressure (50 < P < 25 MPa), just below the fragmentation level. In contrast, homogenous nucleation in series #2 and #3 melts is a continuous process. As well, chemical near-equilibrium degassing occurs in the series #1 melts, unlike in the series #2 and #3 melts which retain high CO2 concentrations even for higher vesicularities (up to 23% at 25 MPa). Thus, our experimental observations underline a significant effect of CO2 on the physical mechanisms of bubble vesiculation in basaltic melts. Our experimental decompression textures either reproduce or approach the characteristics of

  20. The Fate of Sulfur during Decompression Melting of Peridotite and Crystallization of Basalts - Implications for Sulfur Geochemistry of MORB and the Earth's Upper Mantle

    NASA Astrophysics Data System (ADS)

    Ding, S.; Dasgupta, R.

    2014-12-01

    Magmatism in mid-ocean ridges is the main pathway of sulfur (S) from the Earth's mantle to the surficial reservoir. MORB is generally considered sulfide saturated due to the positive correlation between S and FeOT concentration (e.g., [1]). However, most MORBs are differentiated, and both S content and sulfur concentration at sulfide saturation (SCSS) change with P, T, and magma composition (e.g., [2]). Therefore, it remains uncertain, from the MORB chemistry alone, whether mantle melts parental to MORB are sulfide saturated. In this study, we modeled the behavior of S during isentropic partial melting of a fertile peridotite using pMELTS [3] and an SCSS parameterization [4]. Our results show that during decompression melting, at a fixed mantle potential temperature, TP (e.g., 1300 °C), SCSS of aggregate melt first slightly increases then decreases at shallower depth with total variation <200 ppm. However, an increase of TP results in a significant increase of SCSS of primitive melts. Our model shows that at 15% melting (F), sulfide in the residue is exhausted for a mantle with <200 ppm S. The resulted sulfide-undersaturated partial melts contain <1000 ppm S and are 4-6 times enriched in Cu compared to the source. In order to compare our modeled results directly to the differentiated basalts, isobaric crystallization calculation was performed on 5, 10, and 15% aggregate melts. SCSS changes along liquid line of descent with a decrease in T and increase in FeOT. Comparison of S contents between the model results and MORB glasses [5] reveals that many MORBs derive from sulfide undersaturated melts. Further, for a TP of 1300-1350 °C and F of 10-15 wt.%, reproduction of self-consistent S, and Cu budget of many MORB glasses requires that S of their mantle source be ~25-200 ppm. We will discuss the interplay of TP, average F, and the conditions of differentiation to bracket the S geochemistry of MORB and MORB source mantle and develop similar systematics for OIBs and

  1. Rapid Ascent of Aphyric Mantle Melts through the Overriding Crust in Subduction Zones: Evidence from Variable Uranium-Series Disequilibria, Amorphous Hydrous Alteration Microtextures in Crystal Rims, and Two-Pyroxene Pseudo-Decompression Paths

    NASA Astrophysics Data System (ADS)

    Zellmer, G. F.; Freymuth, H.; Hsieh, H. H.; Hwang, S. L.; Iizuka, Y.; Miller, C. A.; Rubin, K. H.; Sakamoto, N.; Yurimoto, H.

    2014-12-01

    Volcanic hazard mitigation at subduction zones critically depends on knowledge of magma generation and ascent processes and timescales. Two diametrically opposite scenarios are presently debated: One paradigm is the generation of low-silica (basaltic) melts in the mantle wedge, followed by protracted sub-liquidus magma ascent and evolution through crystal growth and fractionation in crustal reservoirs, which are tapped during volcanic eruptions. In contrast, a diametrically opposite model favours the generation of higher silica melts in the mantle or in a lower crustal hot zone, followed by rapid decompression to the surface under super-liquidus conditions. In the latter case, crystals are picked up during magma ascent, and are in the process of dissolving. We present multiple lines of evidence that point to crystal uptake as the principal processes by which arc melts acquire their crystal cargo: (i) variable 234U-238U disequilibria in mineral separates; (ii) hydrous mineral rims with amorphous alteration textures; and (iii) two-pyroxene pseudo-decompression paths; cf. Zellmer et al. (2014a,b,c), doi: 10.1144/SP385.3 and 10.1144/SP385.9 and 10.1144/SP410.1. These observations point to a scarcity of true phenocrysts in many arc magmas, and thus to decompression of aphyric melts that take up their crystal cargo during ascent. The data imply that many hydrous wedge melts are more silica-rich than basalts and achieve super-liquidus conditions during rapid ascent from great depth.

  2. Magmas with slab fluid and decompression melting signatures coexisting in the Gulf of Fonseca: Evidence from Isla El Tigre volcano (Honduras, Central America)

    NASA Astrophysics Data System (ADS)

    Mattioli, Michele; Renzulli, Alberto; Agostini, Samuele; Lucidi, Roberto

    2016-01-01

    Isla El Tigre volcano is located in the Gulf of Fonseca (Honduras) along the Central America volcanic front, where a significant change in the strike of the volcanic chain is observed. The studied samples of this poorly investigated volcano are mainly subalkaline basic to intermediate lavas (basalts and basaltic andesites) and subordinate subalkaline/alkaline transitional basalts, both having the typical mineralogical and geochemical characteristics of arc volcanic rocks. On the basis of petrographic and geochemical features, two groups of rocks have been distinguished. Lavas from the main volcanic edifice are highly porphyritic and hy-qz normative, and have lower MgO contents (< 5 wt.%). They show significant LILE and LREE enrichments and Nb-Ta depletions, and have a strong slab signature as well as incompatible element contents similar to those of the main front of the adjacent volcanoes in El Salvador and Nicaragua (e.g., Ba/La up to 80). In contrast, lavas from the parasitic cones have higher MgO contents (> 5 wt.%), are ol-hy normative and show lower HFSE depletions relative to LILE and LREE, with lower Ba/La, Ba/Nb and Zr/Nb ratios. This suggests that mantle-derived magmas were not produced by the same process throughout the activity of the volcano. The bulk rock geochemistry and 87Sr/86Sr (0.70373-0.70382), 143Nd/144Nd (0.51298-0.51301), 206Pb/204Pb (18.55-18.58), 207Pb/204Pb (15.54-15.56) and 208Pb/204Pb (38.23-38.26) isotopic data of Isla El Tigre compared with the other volcanoes of the Gulf of Fonseca and all available literature data for Central America suggests that this stratovolcano was mainly built by mantle-derived melts driven by slab-derived fluid-flux melting, while magmas erupted through its parasitic cones have a clear signature of decompression melting with minor slab contribution. The coexistence of these two different mantle melting generation processes is likely related to the complex geodynamic setting of the Gulf of Fonseca, where the

  3. Abrupt change in magma generation processes across the Central American arc in southeastern Guatemala: flux-dominated melting near the base of the wedge to decompression melting near the top of the wedge

    NASA Astrophysics Data System (ADS)

    Walker, J. A.; Carr, M. J.; Patino, L. C.; Johnson, C. M.; Feigenson, M. D.; Ward, R. L.

    1995-07-01

    Lavas erupted behind the volcanic front in southeastern Guatemala have many important distinctions from lavas erupted on the volcanic front. These include: generally higher MgO, Nb, Sr, TiO2, and rare earth element concentrations; higher La/Yb and Nb/Y ratios; and lower Ba/La, La/Nb, Ba/Zr and Zr/Nb ratios. These major and trace element distinctions are caused by reduced fractionation during ascent and storage in the crust, lower degrees of melting in the source, and greatly reduced contributions from the subducted Cocos plate in the source. In addition, because all of these important distinctions are even borne in lavas erupted within 20 km of the front, there is little apparent petrogenetic continuity between front and behind-the-front magmas. What little geochemical continuity exists is in radiogenic isotopes: 143Nd/144Nd falls across the arc, Pb isotopic ratios (except 206Pb/204Pb) rise across the arc, and 87Sr/86Sr rise across the arc after an initial discontinuity within 20 km of the front. These continuous across-arc changes in radiogenic isotopes are caused by increased contamination with older, more isotopically disparate rocks, away from the front. Once the effects of crustal contamination are removed, the remaining isotopic variability behind the front is non-systematic and reflects the inherent isotopic heterogeneity of the source, the mantle wedge. Geochemical disconnection in southeastern Guatemala suggests that behind-the-front magmas are produced by decompression melting near the top of the wedge, not by flux-dominated melting near the base of the wedge.

  4. Optic Nerve Decompression

    MedlinePlus

    ... Nerve Decompression Dacryocystorhinostomy (DCR) Disclosure Statement Printer Friendly Optic Nerve Decompression John Lee, MD Introduction Optic nerve decompression is a surgical procedure aimed at ...

  5. Geochemical variations in Japan Sea back-arc basin basalts formed by high-temperature adiabatic melting of mantle metasomatized by sediment subduction components

    NASA Astrophysics Data System (ADS)

    Hirahara, Yuka; Kimura, Jun-Ichi; Senda, Ryoko; Miyazaki, Takashi; Kawabata, Hiroshi; Takahashi, Toshiro; Chang, Qing; Vaglarov, Bogdan S.; Sato, Takeshi; Kodaira, Shuichi

    2015-05-01

    The Yamato Basin in the Japan Sea is a back-arc basin characterized by basaltic oceanic crust that is twice as thick as typical oceanic crust. Two types of ocean floor basalts, formed during the opening of the Japan Sea in the Middle Miocene, were recovered from the Yamato Basin during Ocean Drilling Program Legs 127/128. These can be considered as depleted (D-type) and enriched (E-type) basalts based on their incompatible trace element and Sr-Nd-Pb-Hf isotopic compositions. Both types of basalts plot along a common mixing array drawn between depleted mantle and slab sediment represented by a sand-rich turbidite on the Pacific Plate in the NE Japan fore arc. The depleted nature of the D-type basalts suggests that the slab sediment component is nil to minor relative to the dominant mantle component, whereas the enrichment of all incompatible elements in the E-type basalts was likely caused by a large contribution of bulk slab sediment in the source. The results of forward model calculations using adiabatic melting of a hydrous mantle with sediment flux indicate that the melting conditions of the source mantle for the D-type basalts are deeper and hotter than those for the E-type basalts, which appear to have formed under conditions hotter than those of normal mid-oceanic ridge basalts (MORB). These results suggest that the thicker oceanic crust was formed by greater degrees of melting of a hydrous metasomatized mantle source at unusually high mantle potential temperature during the opening of the Japan Sea.

  6. Sub-diffraction Imaging via Surface Plasmon Decompression

    DTIC Science & Technology

    2014-06-08

    of the local wavelength of a surface plasmon polariton supported by two adjoining curved metal surfaces. The views, opinions and/or findings...adiabatic decompression of the local wavelength of a surface plasmon polariton supported by two adjoining curved metal surfaces. Conference Name...diffraction imaging based on a process of adiabatic decompression of the local wavelength of a surface plasmon polariton supported by two adjoining curved

  7. The Evolution of Crystal Textures along Varied Degassing Paths: Insights from Experimental Decompression of Rhyodacite Melt Saturated with H2O and H2O-CO2 Fluids

    NASA Astrophysics Data System (ADS)

    Riker, J.; Blundy, J.; Rust, A.; Cashman, K. V.

    2013-12-01

    Magma ascent is intimately linked to the style of volcanic eruptions. The reasons for this are largely kinetic: timescales of decompression-driven vesiculation and crystallization strongly influence the ease of gas escape from viscous melts. The interplay between gas loss and crystallization is therefore relevant to a wide spectrum of eruptive behaviour, from explosive to effusive, and to the transitions between endmember eruptive styles. Experiments simulating magmatic decompression provide a means of calibrating the textures and compositions of erupted products against known ascent conditions. A key theme arising from the growing cache of experimental data is that decompression path - not simply decompression rate - dramatically affects the time evolution of crystal abundances and textures. Here we present the results of high-temperature, high-pressure decompression experiments designed to assess the effect of degassing path on progressive crystallisation of Mount St. Helens rhyodacite. Three families of experiments were employed to simulate varied PH2O-t trajectories: single-step, water-saturated ascent; continuous, water-saturated ascent; and continuous, H2O-CO2 saturated ascent. Experimental decompression rates range from 1 to >1000 MPa hr-1. Quantitative textural data (abundance, number density, and size) have been used to calculate time-averaged plagioclase nucleation (10-2-101 mm-3 s-1) and growth (10-8-10-6 mm s-1) rates in run products. As anticipated, instantaneous decompressions yield higher nucleation rates than slower decompressions; however, the presence of CO2 also increases nucleation rates relative to the pure water case. These early-formed textural distinctions persist even at the lowest pressures examined, suggesting that deep H2O-CO2 fluids leave a lasting textural 'fingerprint' on magmas that ascend to shallower portions of the magmatic plumbing system. Growth on pre-existing crystals contributes significantly to added crystallization at a

  8. Decompression Theory.

    DTIC Science & Technology

    1980-06-25

    new experiments at 30 m ( 4 ATA) is appropriate for comparing N2 and He with respect to half times and surfacing ratios. Table 4 demonstrates the...THEORY C4 i t44 4 ’I9 41-*1 ai4 p80 7 10 009 UM"tUBNC*nm N4MDOf 29WS (DT) 6-25-80 The Seventeenth Undersea Medical Society Workshop DECOMPRESSION...Hamilton, Jr., Ph.D. Edward L Beckman, M.D. Hamilton Research Ltd. University of Hawaii 80 Grove Street School of Medicine Tarrytown, New York 10591

  9. Contrasting compositional trends of rocks and olivine-hosted melt inclusions from Cerro Negro volcano (Central America): implications for decompression-driven fractionation of hydrous magmas

    NASA Astrophysics Data System (ADS)

    Portnyagin, Maxim V.; Hoernle, Kaj; Mironov, Nikita L.

    2014-10-01

    Melt inclusions in olivine Fo83-72 from tephras of 1867, 1971 and 1992 eruptions of Cerro Negro volcano represent a series of basaltic to andesitic melts of narrow range of MgO (5.6-8 wt %) formed by ~46 wt % fractional crystallization of olivine (~6 wt %), plagioclase (~27 wt %), pyroxene (~13 wt %) and magnetite (<1 wt %) from primitive basaltic melt (average SiO2 = 49 wt %, MgO = 7.6 wt %, H2O = 6 wt %) as it ascended to the surface from the depth of about 14 km. The crystallization occurred at increasing liquidus temperature from 1,050 to 1,090 °C in the pressure range from 400 to 50 MPa and was induced by release of mixed H2O-CO2 fluid from the melt at decreasing pressure. Matrix glass compositions fall at the high-Si end of the melt inclusion trend and represent the final stage of melt crystallization during and after eruption. The bulk compositions of erupted Cerro Negro magmas (tephras and lavas) range from high- to low-MgO (3-10 wt %) basalts, which form a compositional array crossing the trend of melt inclusions so that virtually no rock from Cerro Negro has composition akin to true melt represented by the inclusions. The variations of the bulk magma (rocks) and melt (melt inclusions) compositions can be generated in a dyke connecting a deep primitive magma reservoir with the Cerro Negro edifice. While the melt inclusions represent the compositional trend of instantaneous melts along the magma pathway at decreasing pressure and H2O content, occurrence of low-Mg to high-Mg basalts reflects the process of phenocryst re-distribution in progressively evolving melt. The crystallization scenario is anticipated to operate everywhere in dykes feeding basaltic volcanoes and can explain the predominance of plagioclase-rich high-Al basalts in island arc as well as typical compositional variations of magmas during single eruptions.

  10. Constraints on Mantle Plume Melting Conditions in the Martian Mantle Based on Improved Melting Phase Relationships of Olivine-Phyric Shergottite Yamato 980459

    NASA Technical Reports Server (NTRS)

    Kiefer, Walter S.; Rapp, Jennifer F.; Usui, Tomohiro; Draper, David S.; Filiberto, Justin

    2016-01-01

    Martian meteorite Yamato 980459 (hereafter Y98) is an olivine-phyric shergottite that has been interpreted as closely approximating a martian mantle melt [1-4], making it an important constraint on adiabatic decompression melting models. It has long been recognized that low pressure melting of the Y98 composition occurs at extremely high temperatures relative to martian basalts (1430 degC at 1 bar), which caused great difficulties in a previous attempt to explain Y98 magma generation via a mantle plume model [2]. However, previous studies of the phase diagram were limited to pressures of 2 GPa and less [2, 5], whereas decompression melting in the present-day martian mantle occurs at pressures of 3-7 GPa, with the shallow boundary of the melt production zone occurring just below the base of the thermal lithosphere [6]. Recent experimental work has now extended our knowledge of the Y98 melting phase relationships to 8 GPa. In light of this improved petrological knowledge, we are therefore reassessing the constraints that Y98 imposes on melting conditions in martian mantle plumes. Two recently discovered olivine- phyric shergottites, Northwest Africa (NWA) 5789 and NWA 6234, may also be primary melts from the martian mantle [7, 8]. However, these latter meteorites have not been the subject of detailed experimental petrology studies, so we focus here on Y98.

  11. Receiver function imaging of the onset of melting, implications for volcanism beneath the Afar Rift in contrast to hotspot environments

    NASA Astrophysics Data System (ADS)

    Rychert, C. A.; Harmon, N.; Hammond, J. O.; Laske, G.; Kendall, J.; Ebinger, C. J.; Shearer, P. M.; Bastow, I. D.; Keir, D.; Ayele, A.; Belachew, M.; Stuart, G. W.

    2012-12-01

    Heating, melting, and stretching destroy continents at volcanic rifts. Mantle plumes are often invoked to thermally weaken the continental lithosphere and accommodate rifting through the influx of magma. However the relative effects of mechanical stretching vs. melt infiltration and weakening are not well quantified during the evolution of rifting. S-to-p (Sp) imaging beneath the Afar Rift and hotspot regions such as Hawaii provides additional constraints. We use data from the Ethiopia/Kenya Broadband Seismic Experiment (EKBSE), the Ethiopia Afar Geophysical Lithospheric Experiment (EAGLE), a new UK/US led deployment of 46 stations in the Afar depression and surrounding area, and the PLUME experiment. We use two methodologies to investigate structure and locate robust features: 1) binning by conversion point and then simultaneous deconvolution in the frequency domain, and 2) extended multitaper followed by migration and stacking. We image a lithosphere-asthenosphere boundary at ~75 km beneath the flank of the Afar Rift vs. its complete absence beneath the rift, where the mantle lithosphere has been totally destroyed. Instead a strong velocity increase with depth at ~75 km depth matches geodynamic model predictions for a drop in melt percentage at the onset of decompression melting. The shallow depth of the onset of melting is consistent with a mantle potential temperature = 1350 - 1400°C, i.e., typical for adiabatic decompression melting. Therefore although a plume initially destroyed the mantle lithosphere, its influence directly beneath Afar today is minimal. Volcanism continues via adiabatic decompression melting assisted by strong melt buoyancy effects. This contrasts with a similar feature at much deeper depth, ~150 km, just west of Hawaii, where a deep thermal plume is hypothesized to impinge on the lithosphere. Improved high resolution imaging of rifting, ridges, and hotspots in a variety of stages and tectonic settings will increase constraints on the

  12. Pathway from subducting slab to surface for melt and fluids beneath Mount Rainier.

    PubMed

    McGary, R Shane; Evans, Rob L; Wannamaker, Philip E; Elsenbeck, Jimmy; Rondenay, Stéphane

    2014-07-17

    Convergent margin volcanism originates with partial melting, primarily of the upper mantle, into which the subducting slab descends. Melting of this material can occur in one of two ways. The flow induced in the mantle by the slab can result in upwelling and melting through adiabatic decompression. Alternatively, fluids released from the descending slab through dehydration reactions can migrate into the hot mantle wedge, inducing melting by lowering the solidus temperature. The two mechanisms are not mutually exclusive. In either case, the buoyant melts make their way towards the surface to reside in the crust or to be extruded as lava. Here we use magnetotelluric data collected across the central state of Washington, USA, to image the complete pathway for the fluid-melt phase. By incorporating constraints from a collocated seismic study into the magnetotelluric inversion process, we obtain superior constraints on the fluids and melt in a subduction setting. Specifically, we are able to identify and connect fluid release at or near the top of the slab, migration of fluids into the overlying mantle wedge, melting in the wedge, and transport of the melt/fluid phase to a reservoir in the crust beneath Mt Rainier.

  13. Pathway from subducting slab to surface for melt and fluids beneath Mount Rainier

    NASA Astrophysics Data System (ADS)

    McGary, R. Shane; Evans, Rob L.; Wannamaker, Philip E.; Elsenbeck, Jimmy; Rondenay, Stéphane

    2014-07-01

    Convergent margin volcanism originates with partial melting, primarily of the upper mantle, into which the subducting slab descends. Melting of this material can occur in one of two ways. The flow induced in the mantle by the slab can result in upwelling and melting through adiabatic decompression. Alternatively, fluids released from the descending slab through dehydration reactions can migrate into the hot mantle wedge, inducing melting by lowering the solidus temperature. The two mechanisms are not mutually exclusive. In either case, the buoyant melts make their way towards the surface to reside in the crust or to be extruded as lava. Here we use magnetotelluric data collected across the central state of Washington, USA, to image the complete pathway for the fluid-melt phase. By incorporating constraints from a collocated seismic study into the magnetotelluric inversion process, we obtain superior constraints on the fluids and melt in a subduction setting. Specifically, we are able to identify and connect fluid release at or near the top of the slab, migration of fluids into the overlying mantle wedge, melting in the wedge, and transport of the melt/fluid phase to a reservoir in the crust beneath Mt Rainier.

  14. Endoscopic Intermetatarsal Ligament Decompression.

    PubMed

    Lui, Tun Hing

    2015-12-01

    Morton neuroma is an entrapment of the intermetatarsal nerve by the deep intermetatarsal ligament. It is usually treated conservatively. Surgery is considered if there is recalcitrant pain that is resistant to conservative treatment. The surgical options include resection of the neuroma or decompression of the involved nerve. Decompression of the nerve by release of the intermetatarsal ligament can be performed by either an open or minimally invasive approach. We describe 2-portal endoscopic decompression of the intermetatarsal nerve. The ligament is released by a retrograde knife through the toe-web portal under arthroscopic guidance through the plantar portal.

  15. Adiabat_1ph 3.0 and the MAGMA website: educational and research tools for studying the petrology and geochemistry of plate margins

    NASA Astrophysics Data System (ADS)

    Antoshechkina, P. M.; Asimow, P. D.

    2010-12-01

    features to be incorporated into adiabat_1ph after its release was the ability to simulate flux melting, in which a metasomatic fluid or melt, of fixed composition, was added to the system before each equilibration step. This idea was further developed in the coupled dynamic and petrological subduction zone model GyPSM, so that fluid flux into the wedge was controlled by the location of dehydration reactions in the slab. The adiabat_1ph release candidate includes a similar option so that the user may specify assimilated compositions, which evolve as the calculation proceeds. This added flexibility opens up a number of possibilities, such as more realistic simulations of melt-rock reactions at mid-ocean ridges. Adiabat_1ph files may be downloaded from the MAGMA website at http://magmasource.caltech.edu/ and feedback is welcomed at a dedicated forum, especially ideas for new software features. MAGMA is an online resource for the study of mantle melting and magma evolution, hosted by Caltech. As well as MELTS-related resources, there are tools for visualization of binary and ternary phase diagrams. Flash movies of phase diagrams for adiabatic decompression melting of peridotite and pyroxenite sources can be played in a web browser or downloaded from a server.

  16. Receiver function imaging of the lithosphere-asthenosphere boundary and melt beneath the Afar Rift in comparison to other systems

    NASA Astrophysics Data System (ADS)

    Rychert, Catherine A.; Harmon, Nicholas

    2015-04-01

    Heating, melting, and stretching destroy continents at volcanic rifts. Mantle plumes are often invoked to thermally weaken the continental lithosphere and accommodate rifting through the influx of magma. However the relative effects of mechanical stretching vs. melt infiltration and weakening are not well quantified during the evolution of rifting. S-to-p (Sp) imaging beneath the Afar Rift provides additional constraints. We use two methodologies to investigate structure and locate robust features: 1) binning by conversion point and then simultaneous deconvolution in the frequency domain, and 2) extended multitaper followed by migration and stacking. We image a lithosphere-asthenosphere boundary at ~75 km beneath the flank of the Afar Rift vs. its complete absence beneath the rift. Instead, a strong velocity increase with depth at ~75 km depth is imaged. Beneath the rift axis waveform modeling suggests the lack of a mantle lithosphere with a velocity increase at ~75 km depth. Geodynamic models that include high melt retention and suppress thermal convection easily match the required velocity-depth profile, the velocity increase arising from a drop in melt percentage at the onset of decompression melting. Whereas, models with conservative melt retention that include thermal buoyancy effects cannot reproduce the strong velocity increase. The shallow depth of the onset of melting is consistent with a mantle potential temperature = 1350 - 1400°C, i.e., typical for adiabatic decompression melting. Trace element signatures and geochemical modeling have been used to argue for a thick lithosphere beneath the rift and slightly higher mantle potential temperatures ~1450°C, although overall, given modeling assumptions, the results are not in disagreement. Therefore, although a plume initially destroyed the mantle lithosphere, its influence directly beneath Afar today is not strong. Volcanism continues via adiabatic decompression melting assisted by strong melt buoyancy

  17. Adiabatic temperature changes of magma-gas mixtures during ascent and eruption

    USGS Publications Warehouse

    Mastin, L.G.; Ghiorso, M.S.

    2001-01-01

    Most quantitative studies of flow dynamics in eruptive conduits during volcanic eruptions use a simplified energy equation that ignores either temperature changes, or the thermal effects of gas exsolution. In this paper we assess the effects of those simplifications by analyzing the influence of equilibrium gas exsolution and expansion on final temperatures, velocities, and liquid viscosities of magma-gas mixtures during adiabatic decompression. For a given initial pressure (p1), temperature (T1) and melt composition, the final temperature (Tf) and velocity (Umax) will vary depending on the degree to which friction and other irreversible processes reduce mechanical energy within the conduit. The final conditions range between two thermodynamic end members: (1) Constant enthalpy (dh=0), in which Tf is maximal and no energy goes into lifting or acceleration; and (2) constant entropy (ds=0), in which Tf is minimal and maximum energy goes into lifting and acceleration. For ds=0, T1=900 ??C and p1=200 MPa, a water-saturated albitic melt cools by ???200 ??C during decompression, but only about 250 ??C of this temperature decrease can be attributed to the energy of gas exsolution per se: The remainder results from expansion of gas that has already exsolved. For the same T1 and p1, and dh=0, Tf is 10-15 ??C hotter than T1 but is about 10-25 ??C cooler than Tf in similar calculations that ignore the energy of gas exsolution. For ds=0, p1=200 MPa and T1= 9,000 ??C, assuming that all the enthalpy change of decompression goes into kinetic energy, a water-saturated albitic mixture can theoretically accelerate to ???800 m/s. Similar calculations that ignore gas exsolution (but take into account gas expansion) give velocities about 10-15% higher. For the same T1, p1 = 200 MPa, and ds = 0, the cooling associated with gas expansion and exsolution increases final melt viscosity more than 2.5 orders of magnitude. For dh = 0, isenthalpic heating decreases final melt viscosity by about

  18. Optimizing Adiabaticity in NMR

    NASA Astrophysics Data System (ADS)

    Vandermause, Jonathan; Ramanathan, Chandrasekhar

    We demonstrate the utility of Berry's superadiabatic formalism for numerically finding control sequences that implement quasi-adiabatic unitary transformations. Using an iterative interaction picture, we design a shortcut to adiabaticity that reduces the time required to perform an adiabatic inversion pulse in liquid state NMR. We also show that it is possible to extend our scheme to two or more qubits to find adiabatic quantum transformations that are allowed by the control algebra, and demonstrate a two-qubit entangling operation in liquid state NMR. We examine the pulse lengths at which the fidelity of these adiabatic transitions break down and compare with the quantum speed limit.

  19. Adiabatic far-field sub-diffraction imaging.

    PubMed

    Cang, Hu; Salandrino, Alessandro; Wang, Yuan; Zhang, Xiang

    2015-08-10

    The limited resolution of a conventional optical imaging system stems from the fact that the fine feature information of an object is carried by evanescent waves, which exponentially decays in space and thus cannot reach the imaging plane. We introduce here an adiabatic lens, which utilizes a geometrically conformal surface to mediate the interference of slowly decompressed electromagnetic waves at far field to form images. The decompression is satisfying an adiabatic condition, and by bridging the gap between far field and near field, it allows far-field optical systems to project an image of the near-field features directly. Using these designs, we demonstrated the magnification can be up to 20 times and it is possible to achieve sub-50 nm imaging resolution in visible. Our approach provides a means to extend the domain of geometrical optics to a deep sub-wavelength scale.

  20. Adiabatic far-field sub-diffraction imaging

    PubMed Central

    Cang, Hu; Salandrino, Alessandro; Wang, Yuan; Zhang, Xiang

    2015-01-01

    The limited resolution of a conventional optical imaging system stems from the fact that the fine feature information of an object is carried by evanescent waves, which exponentially decays in space and thus cannot reach the imaging plane. We introduce here an adiabatic lens, which utilizes a geometrically conformal surface to mediate the interference of slowly decompressed electromagnetic waves at far field to form images. The decompression is satisfying an adiabatic condition, and by bridging the gap between far field and near field, it allows far-field optical systems to project an image of the near-field features directly. Using these designs, we demonstrated the magnification can be up to 20 times and it is possible to achieve sub-50 nm imaging resolution in visible. Our approach provides a means to extend the domain of geometrical optics to a deep sub-wavelength scale. PMID:26258769

  1. Crystallization kinetics in magmas during decompression

    NASA Astrophysics Data System (ADS)

    Arzilli, Fabio; Burton, Mike; Carroll, Michael R.

    2016-04-01

    Many variables play a role during magma crystallization at depth or in a volcanic conduit, and through experimentally derived constraints we can better understand pre- and syn-eruptive magma crystallization behavior. The thermodynamic properties of magmas have been extensively investigated as a function of T, P, fO2 and magma composition [1], and this allows estimation of the stability of equilibrium phases and physical parameters (e.g., density, viscosity). However, many natural igneous rocks contain geochemical, mineralogical and textural evidence of disequilibrium, suggesting that magmas frequently follow non-equilibrium, time-dependent pathways that are recorded in the geochemical and petrographic characteristics of the rocks. There are currently no suitable theoretical models capable of calculating nucleation and growth rates in disequilibrium conditions without experimental constraints. The aim of this contribution is provide quantitative data on growth and nucleation rates of feldspar crystals in silicate melts obtained through decompression experiments, in order to determine the magma evolution in pre- and sin-eruptive conditions. Decompression is one of the main processes that induce the crystallization of feldspar during the magma ascent in the volcanic conduit. Decompression experiments have been carried out on trachytic and basaltic melts to investigate crystallization kinetics of feldspar as a function of the effect of the degassing, undercooling and time on nucleation and crystal growth process [2; 3]. Furthermore, feldspar is the main crystals phase present in magmas, and its abundance can strongly vary with small changes in pressure, temperature and water content in the melt, implying appreciable variations in the textures and in the crystallization kinetics. Crystallization kinetics of trachytic melts show that long experiment durations involve more nucleation events of alkali feldspar than short experiment durations [2]. This is an important

  2. Decompression experiments identify kinetic controls on explosive silicic eruptions

    USGS Publications Warehouse

    Mangan, M.T.; Sisson, T.W.; Hankins, W.B.

    2004-01-01

    Eruption intensity is largely controlled by decompression-induced release of water-rich gas dissolved in magma. It is not simply the amount of gas that dictates how forcefully magma is propelled upwards during an eruption, but also the rate of degassing, which is partly a function of the supersaturation pressure (??Pcritical) triggering gas bubble nucleation. High temperature and pressure decompression experiments using rhyolite and dacite melt reveal compositionally-dependent differences in the ??Pcritical of degassing that may explain why rhyolites have fueled some of the most explosive eruptions on record.

  3. Wireless adiabatic power transfer

    SciTech Connect

    Rangelov, A.A.; Suchowski, H.; Silberberg, Y.; Vitanov, N.V.

    2011-03-15

    Research Highlights: > Efficient and robust mid-range wireless energy transfer between two coils. > The adiabatic energy transfer is analogous to adiabatic passage in quantum optics. > Wireless energy transfer is insensitive to any resonant constraints. > Wireless energy transfer is insensitive to noise in the neighborhood of the coils. - Abstract: We propose a technique for efficient mid-range wireless power transfer between two coils, by adapting the process of adiabatic passage for a coherently driven two-state quantum system to the realm of wireless energy transfer. The proposed technique is shown to be robust to noise, resonant constraints, and other interferences that exist in the neighborhood of the coils.

  4. THE AMELIORATIVE EFFECTS OF HEPARIN AND DEPOLYMERIZED HYALURONATE ON DECOMPRESSION SICKNESS IN RATS,

    DTIC Science & Technology

    DECOMPRESSION SICKNESS, DRUGS), (* MUCOPOLYSACCHARIDES , DECOMPRESSION SICKNESS), (*HEPARIN, DECOMPRESSION SICKNESS), (*ANTICOAGULANTS, DECOMPRESSION SICKNESS), RATS, COUMARINS, BLOOD COAGULATION, DOSAGE, LIPIDS, CANADA

  5. Dynamic Heating and Decompression Experiments on Dacite and Rhyolite Magmas

    NASA Astrophysics Data System (ADS)

    Andrews, B. J.; Waters, L.; Grocke, S. B.

    2015-12-01

    Mineral reaction rims, zoned crystals, and myriad growth or dissolution textures provide evidence for changes in magma pressure, temperature, or composition. Quantifying the magnitudes, timescales and length scales of those variations is a fundamental challenge of volcanology and igneous petrology; experiments provide quantitative insights into how magmas react to changes in pressure and temperature that can be used to address that challenge. We use single-step and dynamic experiments conducted in cold seal pressure vessels to study the responses of dacite and rhyolite magmas to heating and decompression events. During single-step decompression (or heating) experiments, conditions are changed nearly instantaneously from the initial to final state in one step, or several smaller steps, whereas "dynamic experiments" have continuous variation in pressure and/or temperature. These two types of experiments yield useful and complementary information describing crystal nucleation, growth, and reaction rates in response to changing (as opposed to steady state) conditions. Here we discuss isothermal decompression experiments that show substantial path-dependence for runs with equivalent time-averaged decompression rates as slow as 0.27 MPa/h for >500 h. Continuous decompression experiments often contain fewer but larger plagioclase crystals than are present in single-step runs, and those new crystals often show complex growth textures. Our results suggest that even slow changes in storage conditions can disrupt melt structure and greatly retard nucleation provided the changes are steady. We hypothesize that if the decompression path remains steady and continuous (absent a stall on and/or rapid decompression), the magma can remain in a growth-dominated regime even though it is far from equilibrium.

  6. Parallelizable adiabatic gate teleportation

    NASA Astrophysics Data System (ADS)

    Nakago, Kosuke; Hajdušek, Michal; Nakayama, Shojun; Murao, Mio

    2015-12-01

    To investigate how a temporally ordered gate sequence can be parallelized in adiabatic implementations of quantum computation, we modify adiabatic gate teleportation, a model of quantum computation proposed by Bacon and Flammia [Phys. Rev. Lett. 103, 120504 (2009), 10.1103/PhysRevLett.103.120504], to a form deterministically simulating parallelized gate teleportation, which is achievable only by postselection. We introduce a twisted Heisenberg-type interaction Hamiltonian, a Heisenberg-type spin interaction where the coordinates of the second qubit are twisted according to a unitary gate. We develop parallelizable adiabatic gate teleportation (PAGT) where a sequence of unitary gates is performed in a single step of the adiabatic process. In PAGT, numeric calculations suggest the necessary time for the adiabatic evolution implementing a sequence of L unitary gates increases at most as O (L5) . However, we show that it has the interesting property that it can map the temporal order of gates to the spatial order of interactions specified by the final Hamiltonian. Using this property, we present a controlled-PAGT scheme to manipulate the order of gates by a control qubit. In the controlled-PAGT scheme, two differently ordered sequential unitary gates F G and G F are coherently performed depending on the state of a control qubit by simultaneously applying the twisted Heisenberg-type interaction Hamiltonians implementing unitary gates F and G . We investigate why the twisted Heisenberg-type interaction Hamiltonian allows PAGT. We show that the twisted Heisenberg-type interaction Hamiltonian has an ability to perform a transposed unitary gate by just modifying the space ordering of the final Hamiltonian implementing a unitary gate in adiabatic gate teleportation. The dynamics generated by the time-reversed Hamiltonian represented by the transposed unitary gate enables deterministic simulation of a postselected event of parallelized gate teleportation in adiabatic

  7. Decompression apparatus for engines

    SciTech Connect

    Harada, M.

    1987-09-29

    In a decompression apparatus for an engine having a camshaft, a cam gear is described having a longitudinal bore along a central axis thereof, and a tappet engaging with an actuating cam on the camshaft. The improvement comprises: a releasing lever comprising a shaft and a weight secured to the shaft; the shaft forming a semicircular cam at one end; the camshaft having a first recess in a longitudinal direction; the cam gear having a second recess adjacent the bore; a bearing member for engaging with the first and second recesses and for rotatably supporting the shaft; a flat bottom notch for supporting the semicircular cam and being provided on the camshaft lose to the actuating cam; and the semicircular cam being arranged to project beyond a periphery of the actuating cam when engine operation is stopped.

  8. Quantum adiabatic machine learning

    NASA Astrophysics Data System (ADS)

    Pudenz, Kristen L.; Lidar, Daniel A.

    2013-05-01

    We develop an approach to machine learning and anomaly detection via quantum adiabatic evolution. This approach consists of two quantum phases, with some amount of classical preprocessing to set up the quantum problems. In the training phase we identify an optimal set of weak classifiers, to form a single strong classifier. In the testing phase we adiabatically evolve one or more strong classifiers on a superposition of inputs in order to find certain anomalous elements in the classification space. Both the training and testing phases are executed via quantum adiabatic evolution. All quantum processing is strictly limited to two-qubit interactions so as to ensure physical feasibility. We apply and illustrate this approach in detail to the problem of software verification and validation, with a specific example of the learning phase applied to a problem of interest in flight control systems. Beyond this example, the algorithm can be used to attack a broad class of anomaly detection problems.

  9. Adiabatic capture and debunching

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2012-03-01

    In the study of beam preparation for the g-2 experiment, adiabatic debunching and adiabatic capture are revisited. The voltage programs for these adiabbatic processes are derived and their properties discussed. Comparison is made with some other form of adiabatic capture program. The muon g-2 experiment at Fermilab calls for intense proton bunches for the creation of muons. A booster batch of 84 bunches is injected into the Recycler Ring, where it is debunched and captured into 4 intense bunches with the 2.5-MHz rf. The experiment requires short bunches with total width less than 100 ns. The transport line from the Recycler to the muon-production target has a low momentum aperture of {approx} {+-}22 MeV. Thus each of the 4 intense proton bunches required to have an emittance less than {approx} 3.46 eVs. The incoming booster bunches have total emittance {approx} 8.4 eVs, or each one with an emittance {approx} 0.1 eVs. However, there is always emittance increase when the 84 booster bunches are debunched. There will be even larger emittance increase during adiabatic capture into the buckets of the 2.5-MHz rf. In addition, the incoming booster bunches may have emittances larger than 0.1 eVs. In this article, we will concentrate on the analysis of the adiabatic capture process with the intention of preserving the beam emittance as much as possible. At this moment, beam preparation experiment is being performed at the Main Injector. Since the Main Injector and the Recycler Ring have roughly the same lattice properties, we are referring to adiabatic capture in the Main Injector instead in our discussions.

  10. Adiabatic gate teleportation.

    PubMed

    Bacon, Dave; Flammia, Steven T

    2009-09-18

    The difficulty in producing precisely timed and controlled quantum gates is a significant source of error in many physical implementations of quantum computers. Here we introduce a simple universal primitive, adiabatic gate teleportation, which is robust to timing errors and many control errors and maintains a constant energy gap throughout the computation above a degenerate ground state space. This construction allows for geometric robustness based upon the control of two independent qubit interactions. Further, our piecewise adiabatic evolution easily relates to the quantum circuit model, enabling the use of standard methods from fault-tolerance theory for establishing thresholds.

  11. REEBOX PRO: A forward model simulating melting of thermally and lithologically variable upwelling mantle

    NASA Astrophysics Data System (ADS)

    Brown, Eric L.; Lesher, Charles E.

    2016-10-01

    The compositions and volumes of basalts erupted in divergent margin environments provide a record of the thermal, chemical, and dynamical state of their mantle source regions. To relate basalt compositions and volumes to the underlying thermochemical and dynamical state of their mantle source regions, we have developed REEBOX PRO, a compiled stand-alone application that simulates adiabatic decompression melting of passively or actively upwelling mantle containing up to five distinct lithologies. The model calculates melt compositions using thermodynamic and experimental constraints on the melting behaviors and mineral-melt partitioning behavior of homogeneous and lithologically heterogeneous mantle sources containing anhydrous peridotite, hydrous peridotite, harzburgite, and/or silica-saturated/-undersaturated pyroxenite. Key model outputs include the mean composition and crustal thickness for the bulk basaltic crust, calculated for passive and active upwelling scenarios. Here, we present the mathematical formulations underlying the model and benchmark it against existing hydrous melting models and models for mid-ocean ridge basalt formation. We show that the hydrous and anhydrous peridotite melting models incorporated in REEBOX PRO capture the essential differences in basalt composition and volume demonstrated by previous models, and constrain the ambient mantle beneath the global spreading ridge system to be between 1319 and 1366°C, depending on the relative fertility and/or water content of the mid-ocean ridge mantle source. We also show how model outputs may be manipulated outside of the modeling program to calculate nontraditional melt mixing scenarios. These examples highlight the flexibility of REEBOX PRO for simulating melt generation within a range of geodynamical contexts.

  12. Eruptive dynamics during magma decompression: a laboratory approach

    NASA Astrophysics Data System (ADS)

    Spina, L.; Cimarelli, C.; Scheu, B.; Wadsworth, F.; Dingwell, D. B.

    2013-12-01

    A variety of eruptive styles characterizes the activity of a given volcano. Indeed, eruptive styles can range from effusive phenomena to explosive eruptions, with related implications for hazard management. Rapid changes in eruptive style can occur during an ongoing eruption. These changes are, amongst other, related to variations in the magma ascent rate, a key parameter affecting the eruptive style. Ascent rate is in turn dependent on several factors such as the pressure in the magma chamber, the physical properties of the magma and the rate at which these properties change. According to the high number of involved parameters, laboratory decompression experiments are the best way to achieve quantitative information on the interplay of each of those factors and the related impact on the eruption style, i.e. by analyzing the flow and deformation behavior of the transparent volatile-bearing analogue fluid. We carried out decompression experiments following different decompression paths and using silicone oil as an analogue for the melt, with which we can simulate a range of melt viscosity values. For a set of experiments we added rigid particles to simulate the presence of crystals in the magma. The pure liquid or suspension was mounted into a transparent autoclave and pressurized to different final pressures. Then the sample was saturated with argon for a fixed amount of time. The decompression path consists of a slow decompression from the initial pressure to the atmospheric condition. Alternatively, samples were decompressed almost instantaneously, after established steps of slow decompression. The decompression path was monitored with pressure transducers and a high-speed video camera. Image analysis of the videos gives quantitative information on the bubble distribution with respect to depth in the liquid, pressure and time of nucleation and on their characteristics and behavior during the ongoing magma ascent. Furthermore, we also monitored the evolution of

  13. Adiabatically implementing quantum gates

    SciTech Connect

    Sun, Jie; Lu, Songfeng Liu, Fang

    2014-06-14

    We show that, through the approach of quantum adiabatic evolution, all of the usual quantum gates can be implemented efficiently, yielding running time of order O(1). This may be considered as a useful alternative to the standard quantum computing approach, which involves quantum gates transforming quantum states during the computing process.

  14. Semiconductor adiabatic qubits

    DOEpatents

    Carroll, Malcolm S.; Witzel, Wayne; Jacobson, Noah Tobias; Ganti, Anand; Landahl, Andrew J.; Lilly, Michael; Nguyen, Khoi Thi; Bishop, Nathaniel; Carr, Stephen M.; Bussmann, Ezra; Nielsen, Erik; Levy, James Ewers; Blume-Kohout, Robin J.; Rahman, Rajib

    2016-12-27

    A quantum computing device that includes a plurality of semiconductor adiabatic qubits is described herein. The qubits are programmed with local biases and coupling terms between qubits that represent a problem of interest. The qubits are initialized by way of a tuneable parameter, a local tunnel coupling within each qubit, such that the qubits remain in a ground energy state, and that initial state is represented by the qubits being in a superposition of |0> and |1> states. The parameter is altered over time adiabatically or such that relaxation mechanisms maintain a large fraction of ground state occupation through decreasing the tunnel coupling barrier within each qubit with the appropriate schedule. The final state when tunnel coupling is effectively zero represents the solution state to the problem represented in the |0> and |1> basis, which can be accurately read at each qubit location.

  15. A Start Toward Micronucleus-Based Decompression Models; Altitude Decompression

    NASA Technical Reports Server (NTRS)

    Van Liew, H. D.; Conkin, Johnny

    2007-01-01

    Do gaseous micronuclei trigger the formation of bubbles in decompression sickness (DCS)? Most previous instructions for DCS prevention have been oriented toward supersaturated gas in tissue. We are developing a mathematical model that is oriented toward the expected behavior of micronuclei. The issue is simplified in altitude decompressions because the aviator or astronaut is exposed only to decompression, whereas in diving there is a compression before the decompression. The model deals with four variables: duration of breathing of 100% oxygen before going to altitude (O2 prebreathing), altitude of the exposure, exposure duration, and rate of ascent. Assumptions: a) there is a population of micronuclei of various sizes having a range of characteristics, b) micronuclei are stable until they grow to a certain critical nucleation radius, c) it takes time for gas to diffuse in or out of micronuclei, and d) all other variables being equal, growth of micronuclei upon decompression is more rapid at high altitude because of the rarified gas in the micronuclei. To estimate parameters, we use a dataset of 4,756 men in altitude chambers exposed to various combinations of the model s variables. The model predicts occurrence of DCS symptoms quite well. It is notable that both the altitude chamber data and the model show little effect of O2 prebreathing until it lasts more than 60 minutes; this is in contrast to a conventional idea that the benefit of prebreathing is directly due to exponential washout of tissue nitrogen. The delay in response to O2 prebreathing can be interpreted as time required for outward diffusion of nitrogen; when the micronuclei become small enough, they are disabled, either by crushing or because they cannot expand to a critical nucleation size when the subject ascends to altitude.

  16. Melt Generation in Heterogeneous Mantle Sources: A Three-Legged Stool Approach

    NASA Astrophysics Data System (ADS)

    Brown, E. L.; Lesher, C. E.

    2009-05-01

    The compositions and volumes of basalts generated by adiabatic decompression melting are primarily a function of three factors: mantle potential temperature, the style of mantle upwelling, and source composition. Attempts to use basalts to infer the relative importance of these three factors in specific localities are made difficult because even for homogeneous mantle sources, basalts are aggregates of melts generated over a range of pressures and temperatures within the melting regime. When source heterogeneity and differences in the melting behavior of source lithologies are accounted for, the complexity of relating basalts to the conditions of melt generation increases substantially. Advances in our understanding of mid - ocean ridge basalt petrogenesis have demonstrated the utility of creating geochemical models for melt generation that are constrained by experimental petrology [e.g. 1]. To better relate basalt compositions to the melting processes within a heterogeneous mantle source, we have developed a forward polybaric melting model that simulates the melting of a source comprised of pyroxenite and peridotite. The model uses thermodynamically - derived polybaric melting functions based on parameterizations of pyroxenite and peridotite melting [2, 3]. The model takes into account mantle potential temperature, style of mantle upwelling and variable amounts of pyroxenite, and outputs the isotopic and trace element compositions and volumes of pooled melts using the residual mantle column method [4]. We propagate uncertainties in model input parameters to assess robustness and compare our results with previous models [5-7]. We apply our model to ocean island and large igneous province environments to constrain potential temperature, upwelling rate and abundance of pyroxenite in the mantle source from observed basalt compositions and volumes. [1] Longhi 2002, G-cubed, doi:10.1029/2001/GC000204; [2] Katz et al. 2003, G-cubed, doi:10.1029/2002GC000433; [3

  17. On Adiabatic Pair Creation

    NASA Astrophysics Data System (ADS)

    Pickl, Peter; Dürr, Detlef

    2008-08-01

    We give here a rigorous proof of the well known prediction of pair creation as it arises from the Dirac equation with an external time dependent potential. Pair creation happens with probability one if the potential changes adiabatically in time and becomes overcritical, which means that an eigenvalue curve (as a function of time) bridges the gap between the negative and positive spectral continuum. The potential can be thought of as being zero at large negative and large positive times. The rigorous treatment of this effect has been lacking since the pioneering work of Beck, Steinwedel and Süßmann [1] in 1963 and Gershtein and Zeldovich [8] in 1970.

  18. Geometry of the Adiabatic Theorem

    ERIC Educational Resources Information Center

    Lobo, Augusto Cesar; Ribeiro, Rafael Antunes; Ribeiro, Clyffe de Assis; Dieguez, Pedro Ruas

    2012-01-01

    We present a simple and pedagogical derivation of the quantum adiabatic theorem for two-level systems (a single qubit) based on geometrical structures of quantum mechanics developed by Anandan and Aharonov, among others. We have chosen to use only the minimum geometric structure needed for the understanding of the adiabatic theorem for this case.…

  19. Spaceflight Decompression Sickness Contingency Plan

    NASA Technical Reports Server (NTRS)

    Dervay, Joseph P.

    2007-01-01

    A viewgraph presentation on the Decompression Sickness (DCS) Contingency Plan for manned spaceflight is shown. The topics include: 1) Approach; 2) DCS Contingency Plan Overview; 3) Extravehicular Activity (EVA) Cuff Classifications; 4) On-orbit Treatment Philosophy; 5) Long Form Malfunction Procedure (MAL); 6) Medical Checklist; 7) Flight Rules; 8) Crew Training; 9) Flight Surgeon / Biomedical Engineer (BME) Training; and 10) DCS Emergency Landing Site.

  20. Cardiopulmonary Changes with Moderate Decompression in Rats

    NASA Technical Reports Server (NTRS)

    Robinson, R.; Little, T.; Doursout, M.-F.; Butler, B. D.; Chelly, J. E.

    1996-01-01

    Sprague-Dawley rats were compressed to 616 kPa for 120 min then decompressed at 38 kPa/min to assess the cardiovascular and pulmonary responses to moderate decompression stress. In one series of experiments the rats were chronically instrumented with Doppler ultrasonic probes for simultaneous measurement of blood pressure, cardiac output, heart rate, left and right ventricular wall thickening fraction, and venous bubble detection. Data were collected at base-line, throughout the compression/decompression protocol, and for 120 min post decompression. In a second series of experiments the pulmonary responses to the decompression protocol were evaluated in non-instrumented rats. Analyses included blood gases, pleural and bronchoalveolar lavage (BAL) protein and hemoglobin concentration, pulmonary edema, BAL and lung tissue phospholipids, lung compliance, and cell counts. Venous bubbles were directly observed in 90% of the rats where immediate post-decompression autopsy was performed and in 37% using implanted Doppler monitors. Cardiac output, stroke volume, and right ventricular wall thickening fractions were significantly decreased post decompression, whereas systemic vascular resistance was increased suggesting a decrease in venous return. BAL Hb and total protein levels were increased 0 and 60 min post decompression, pleural and plasma levels were unchanged. BAL white blood cells and neutrophil percentages were increased 0 and 60 min post decompression and pulmonary edema was detected. Venous bubbles produced with moderate decompression profiles give detectable cardiovascular and pulmonary responses in the rat.

  1. European EVA decompression sickness risks

    NASA Astrophysics Data System (ADS)

    Vogt, Lorenz; Wenzel, Jürgen; Skoog, A. I.; Luck, S.; Svensson, Bengt

    For the first manned flight of Hermes there will be a capability of performing EVA. The European EVA Space Suit will be an anthropomorphic system with an internal pressure of 500 hPa of pure oxygen. The pressure reduction from the Hermes cabin pressure of 1013 hPa will induce a risk for Decompression Sickness (DCS) for the EVA crewmember if no adequate protective procedures are implemented. Specific decompression procedures have to be developed. From a critical review of the literature and by using knowledge gained from research conducted in the past in the fields of diving and aerospace medicine safe protective procedures are proposed for the European EVA scenario. An R factor of 1.2 and a tissue half-time ( t1/2) of 360 minutes in a single-tissue model have been identified as appropriate operational values. On the basis of an acceptable risk level of approximately 1%, oxygen prebreathing times are proposed for (a) direct pressure reduction from 1013 hPa to a suit pressure of 500 hPa, and (b) staged decompression using a 700 hPa intermediate stage in the spacecraft cabin. In addition, factors which influence individual susceptibility to DCS are identified. Recommendations are also given in the areas of crew selection and medical monitoring requirements together with therapeutic measures that can be implemented in the Hermes scenario. A method for demonstration of the validity of proposed risks and procedures is proposed.

  2. A melting model for variably depleted and enriched lherzolite in the plagioclase and spinel stability fields

    NASA Astrophysics Data System (ADS)

    Till, Christy B.; Grove, Timothy L.; Krawczynski, Michael J.

    2012-06-01

    Here we develop a lherzolite melting model and explore the effects of variations in mantle composition, pressure, temperature, and H2O content on melt composition. New experiments and a compilation of experimental liquids saturated with all of the mantle minerals (olivine, orthopyroxene, clinopyroxene, plagioclase and/or spinel) are used to calibrate a model that predicts the temperature and major element composition of a broad spectrum of primary basalt types produced under anhydrous to low H2O-content conditions at upper mantle pressures. The model can also be used to calculate the temperature and pressure at which primary magmas were produced in the mantle, as well as to model both near-fractional adiabatic decompression and batch melting. Our experimental compilation locates the pressure interval of the plagioclase to spinel transition on the solidus and shows that it is narrow (˜0.1 GPa) for melting of natural peridotite compositions. The multiple saturation boundaries determined by our model provide a method for assessing the appropriate mineral assemblage, as well as the extent of the fractional crystallization correction required to return a relatively primitive liquid to equilibrium with the mantle source. We demonstrate that an inaccurate fractionation correction can overestimate temperature and depths of melting by hundreds of degrees and tens of kilometers, respectively. This model is particularly well suited to examining the temperature and pressure of origin for intraplate basaltic volcanism and is used to examine the petrogenesis of a suite of Holocene basaltic lavas from Diamond Crater in Oregon's High Lava Plains (HLP).

  3. Sulfur Saturation Limits in Silicate Melts and their Implications for Core Formation Scenarios for Terrestrial Planets

    NASA Technical Reports Server (NTRS)

    Holzheid, Astrid; Grove, Timothy L.

    2002-01-01

    This study explores the controls of temperature, pressure, and silicate melt composition on S solubility in silicate liquids. The solubility of S in FeO-containing silicate melts in equilibrium with metal sulfide increases significantly with increasing temperature but decreases with increasing pressure. The silicate melt structure also exercises a control on S solubility. Increasing the degree of polymerization of the silicate melt structure lowers the S solubility in the silicate liquid. The new set of experimental data is used to expand the model of Mavrogenes and O'Neill(1999) for S solubility in silicate liquids by incorporating the influence of the silicate melt structure. The expected S solubility in the ascending magma is calculated using the expanded model. Because the negative pressure dependence of S solubility is more influential than the positive temperature dependence, decompression and adiabatic ascent of a formerly S-saturated silicate magma will lead to S undersaturation. A primitive magma that is S-saturated in its source region will, therefore, become S-undersaturated as it ascends to shallower depth. In order to precipitate magmatic sulfides, the magma must first cool and undergo fractional crystallization to reach S saturation. The S content in a metallic liquid that is in equilibrium with a magma ocean that contains approx. 200 ppm S (i.e., Earth's bulk mantle S content) ranges from 5.5 to 12 wt% S. This range of S values encompasses the amount of S (9 to 12 wt%) that would be present in the outer core if S is the light element. Thus, the Earth's proto-mantle could be in equilibrium (in terms of the preserved S abundance) with a core-forming metallic phase.

  4. Investigating degassing dynamics into the shallow conduit through decompression experiments

    NASA Astrophysics Data System (ADS)

    Spina, Laura; Scheu, Bettina; Cimarelli, Corrado; Dingwell, Donald

    2014-05-01

    The history of bubbles' growth and interaction, as well as their spatial distribution in the shallow conduit, is deeply interconnected with the style of the eruptions. According to the fundamental role played by volatiles in the eruptive process, more effort is required in determining how the key factors of volcanic systems (i.e., magma properties, decompression rate) influence the dynamics of degassing. Therefore, our aim is to provide, through the analysis of decompression experiments on analogue materials, insights on such relations. We performed several decompression experiments with a shock-tube apparatus, and using silicon oil as laboratory-analogue for the magmatic melt. The sample was placed in a transparent autoclave, saturated with Argon for an established amount of time under a fixed pressure (up to a maximum of 10 MPa). Successively it was decompressed to atmospheric conditions, by releasing gas through a control valve. The dynamics of gas exsolution processes were recorded by using pressure sensors and a high speed camera. A range of viscosity values (1, 10, 100, 1000 Pa s) was investigated, for the same decompression path. Furthermore, some experiments were carried out with the addition of glass beads, as analogue to crystals, to the pure liquid. The height of the expanding column was monitored, in conjunction with images recorded during the experiments, and the growth rate of bubbles was measured at different times and depth. Finally, bubble size distribution has been evaluated at various stages for some experiments, in order to achieve a spatial map of the ongoing degassing phenomena. Results allowed us to define different regimes occurring during the decompression, whose features and characteristics are strongly affected by fluid viscosity. Indeed, several degassing phases were observed, from bubbly fluid to the eventual buildup of a more or less "foamy" phase, which ultimately experiences periodical oscillations around an average equilibrium level

  5. Subatmospheric Decompression Sickness in Man,

    DTIC Science & Technology

    1969-04-01

    ashtray instead of an adjacent cup. spilling tea when pouring it owing to tremor and he lay down on his bed. He felt very thirsty. When he went to...duties to perform, he went back to the mess, ate his tea at about 4 p. m. and retired to bed, where he had severe nau- sea. frontal headache, pain...1907. Hall, A. L., 1955A. ’Some effects of explosive decompression on albino rats: preliminary studies’. U.S. Navy School Aviat. Med., Res. Proj. NM

  6. Thalmann Algorithm Decompression Table Generation Software Design Document

    DTIC Science & Technology

    2010-09-01

    Decompression Table Generation Software Design Document Navy Experimental Diving Unit Author...TITLE (Include Security Classification) (U) THALMANN ALGORITHM DECOMPRESSION TABLE GENERATION SOFTWARE DESIGN DOCUMENT 12. PERSONAL AUTHOR(S...1 2. Decompression Table Generator (TBLP7R

  7. Graphics processing unit-assisted lossless decompression

    DOEpatents

    Loughry, Thomas A.

    2016-04-12

    Systems and methods for decompressing compressed data that has been compressed by way of a lossless compression algorithm are described herein. In a general embodiment, a graphics processing unit (GPU) is programmed to receive compressed data packets and decompress such packets in parallel. The compressed data packets are compressed representations of an image, and the lossless compression algorithm is a Rice compression algorithm.

  8. SEROTONIN AND OTHER VASOACTIVE AGENTS IN EXPERIMENTAL DECOMPRESSION SICKNESS,

    DTIC Science & Technology

    SEROTONIN, DECOMPRESSION SICKNESS), (*VASOACTIVE AGENTS, DECOMPRESSION SICKNESS), RATS, EXERCISE(PHYSIOLOGY), DOSAGE, CHEMOTHERAPEUTIC AGENTS, BLOOD ANALYSIS, TOXICITY, BLOOD CIRCULATION, MORTALITY RATES , CANADA

  9. Pressureless Orbital Decompression for Myopic Proptosis.

    PubMed

    Rajak, Saul N; McGovern, Richard A; Selva, Dinesh

    2017-01-01

    Orbital decompression surgery increases the orbital volume. It has rarely been used for proptosis of the large highly myopic globe. However, external decompression surgery carries significant risks because of the large thin-walled globe. The authors report the first use of endoscopic medial wall orbital decompression surgery in this setting to obviate the risk of globe pressure.Endoscopic medial wall decompression brought about a 4 mm reduction of proptosis, correction of exotropia and elimination of retrobulbar ache providing good symmetry with the fellow eye.Endoscopic medial wall orbital decompression can be very effective for correcting the proptosis of high myopia and minimizes the risk of damage to the very large, thin-walled globe.

  10. Xenon Blocks Neuronal Injury Associated with Decompression.

    PubMed

    Blatteau, Jean-Eric; David, Hélène N; Vallée, Nicolas; Meckler, Cedric; Demaistre, Sebastien; Lambrechts, Kate; Risso, Jean-Jacques; Abraini, Jacques H

    2015-10-15

    Despite state-of-the-art hyperbaric oxygen (HBO) treatment, about 30% of patients suffering neurologic decompression sickness (DCS) exhibit incomplete recovery. Since the mechanisms of neurologic DCS involve ischemic processes which result in excitotoxicity, it is likely that HBO in combination with an anti-excitotoxic treatment would improve the outcome in patients being treated for DCS. Therefore, in the present study, we investigated the effect of the noble gas xenon in an ex vivo model of neurologic DCS. Xenon has been shown to provide neuroprotection in multiple models of acute ischemic insults. Fast decompression compared to slow decompression induced an increase in lactate dehydrogenase (LDH), a well-known marker of sub-lethal cell injury. Post-decompression administration of xenon blocked the increase in LDH release induced by fast decompression. These data suggest that xenon could be an efficient additional treatment to HBO for the treatment of neurologic DCS.

  11. [Classification of altitude decompression sickness].

    PubMed

    Katuntsev, V P

    2000-01-01

    The article is devoted to the discussion of principles of and approaches to classification of altitude decompression sickness (DCS), one of the most methodically formidable aspects of the problem. Based on his own multiyear experience in altitude DCS investigations and critical review of literature, the author reasons his concept of clinical classification of altitude DCS. The author's concept places emphasis on obligatory consideration of three stages in DCS development: A--pre-disease (the premorbid syndrome), B--uncomplicated (light) and C--complicated (severe) forms. The objective sign of the premorbid state is "silent" gas bubbles in organism detectable by ultrasonic devices. Signs of uncomplicated altitude DCS are musculoarticular pains, local edema and skin itching. Complicated altitude DCS is diagnosed by systemic (respiratory, neurological and cardiovascular) disorders.

  12. libpolycomp: Compression/decompression library

    NASA Astrophysics Data System (ADS)

    Tomasi, Maurizio

    2016-04-01

    Libpolycomp compresses and decompresses one-dimensional streams of numbers by means of several algorithms. It is well-suited for time-ordered data acquired by astronomical instruments or simulations. One of the algorithms, called "polynomial compression", combines two widely-used ideas (namely, polynomial approximation and filtering of Fourier series) to achieve substantial compression ratios for datasets characterized by smoothness and lack of noise. Notable examples are the ephemerides of astronomical objects and the pointing information of astronomical telescopes. Other algorithms implemented in this C library are well known and already widely used, e.g., RLE, quantization, deflate (via libz) and Burrows-Wheeler transform (via libbzip2). Libpolycomp can compress the timelines acquired by the Planck/LFI instrument with an overall compression ratio of ~9, while other widely known programs (gzip, bzip2) reach compression ratios less than 1.5.

  13. The Floquet Adiabatic Theorem revisited

    NASA Astrophysics Data System (ADS)

    Weinberg, Phillip; Bukov, Marin; D'Alessio, Luca; Kolodrubetz, Michael; Davidson, Shainen; Polkovnikov, Anatoli

    2015-03-01

    The existance of the adiabatic theorem for Floquet systems has been the subject of an active debate with different articles reaching opposite conclusions over the years. In this talk we clarify the situation by deriving a systematic expansion in the time-derivatives of a slow parameter for the occupation probabilities of the Floque states. Our analysis shows that the in a certain limit the transition between Floquet eigenstates are suppressed and it is possible to define an adiabatic theorem for Floquet systems. Crucially we observe however that the conditions for adiabaticity in ordinary and Floquet systems are different and that this difference can become important when the amplitude of the periodic driving is large. We illustrate our results with specific examples of a periodically driven harmonic oscillator and cold atoms in optical lattices which are relevant in current experiments.

  14. Adiabatic losses in Stirling refrigerators

    SciTech Connect

    Bauwens, L.

    1996-06-01

    The Stirling cycle has been used very effectively in cryocoolers; but efficiencies relative to the Carnot limit are typically observed to peak for absolute temperature ratios of about two, which makes it less suitable for low-life refrigeration. The adiabatic loss appears to be responsible for poor performance at small temperature differences. In this paper, adiabatic losses are evaluated, for a temperature ratio of 2/3, taking into account the effect of phase angle between pistons, of volume ratio, of the distribution of the dead volume necessary to reduce the volume ratio, and of the distribution of displacement between expansion and compression spaces. The study is carried out numerically, using an adiabatic Stirling engine model in which cylinder flow is assumed to be stratified. Results show that the best location for the cylinder dead volume is on the compression side. Otherwise, all strategies used to trade off refrigeration for coefficient of performance are found to be roughly equivalent.

  15. Adiabatic evolution of plasma equilibrium

    PubMed Central

    Grad, H.; Hu, P. N.; Stevens, D. C.

    1975-01-01

    A new theory of plasma equilibrium is introduced in which adiabatic constraints are specified. This leads to a mathematically nonstandard structure, as compared to the usual equilibrium theory, in which prescription of pressure and current profiles leads to an elliptic partial differential equation. Topologically complex configurations require further generalization of the concept of adiabaticity to allow irreversible mixing of plasma and magnetic flux among islands. Matching conditions across a boundary layer at the separatrix are obtained from appropriate conservation laws. Applications are made to configurations with planned islands (as in Doublet) and accidental islands (as in Tokamaks). Two-dimensional, axially symmetric, helically symmetric, and closed line equilibria are included. PMID:16578729

  16. Is carpal tunnel decompression warranted for HNPP?

    PubMed

    Earle, Nicholas; Zochodne, Douglas W

    2013-12-01

    The role of carpal tunnel decompression surgery for patients that have hereditary neuropathy with liability to pressure palsy (HNPP) is currently unknown. Since recovery from carpal tunnel compression is often associated with remyelination or nodal reconstruction rather than axonal regeneration, it is uncertain whether the PMP22 deletion associated with HNPP interrupts myelin or nodal reconstitution. We describe two patients with genetically confirmed HNPP and symptomatic carpal tunnel syndrome that had clinical and electrophysiological improvement after surgical decompression. The findings indicate a capacity for conduction repair in HNPP. They also suggest a need for further investigation and discussion around whether to offer carpal tunnel decompression to symptomatic HNPP patients.

  17. Segment-Scale Melt Extraction at Mid-Ocean Ridges: A Play in Three Acts

    NASA Astrophysics Data System (ADS)

    Montesi, L. G.; Hebert, L. B.; Behn, M. D.

    2011-12-01

    At mid-ocean ridges, the lithosphere is created through a combination of melt extraction, metasomatism, and cooling, and the oceanic crust forms as melt collects near the surface. As the presence of melt also has rheological and geochemical consequences, a better understanding of the mechanisms that control melt migration and extraction at mid-ocean ridges is necessary to constrain the processes that form oceanic lithosphere and plate boundaries. Melt migration is described rigorously by two-phase transport equations in porous or fractured media. However, scaling considerations and geological constraints typically lead to certain simplifications when incorporated into geodynamical models. It is possible to capture the essence of melt migration and extraction by considering three principal stages: Stage 1. Vertical migration: Melt is generated by adiabatic decompression and rises nearly vertically from the zone of melt production to a melt-impermeable boundary, or permeability barrier, at the base of the thermal lithosphere. Stage 2. Focusing: Melt travels along a permeability barrier. The barrier is associated with a crystallization front and is slightly inclined toward the ridge axis following the thermal structure of the plate. At this stage melt focusing occurs toward and along the strike of the ridge. Stage 3. Extraction: Melt enters a melt extraction zone (MEZ) and is extracted to the surface. The MEZ represents the combined effect of faults and/or dikes that promote rapid lateral and vertical melt migration and eventual eruption on the seafloor. Stage 1 is expected based on scaling arguments of buoyancy and permeability [e.g., Zhu et al., Science, 2011]. Stages 2 and 3 are directly influenced by the structure of the lithosphere, which is itself controlled by the segmentation of the ridge axis, spreading rate, and mantle potential temperature. Thus, it is possible to use along-strike variations in melt delivery in well-studied geological settings to constrain

  18. Pressure Oscillations in Adiabatic Compression

    ERIC Educational Resources Information Center

    Stout, Roland

    2011-01-01

    After finding Moloney and McGarvey's modified adiabatic compression apparatus, I decided to insert this experiment into my physical chemistry laboratory at the last minute, replacing a problematic experiment. With insufficient time to build the apparatus, we placed a bottle between two thick textbooks and compressed it with a third textbook forced…

  19. Transitionless driving on adiabatic search algorithm

    SciTech Connect

    Oh, Sangchul; Kais, Sabre

    2014-12-14

    We study quantum dynamics of the adiabatic search algorithm with the equivalent two-level system. Its adiabatic and non-adiabatic evolution is studied and visualized as trajectories of Bloch vectors on a Bloch sphere. We find the change in the non-adiabatic transition probability from exponential decay for the short running time to inverse-square decay in asymptotic running time. The scaling of the critical running time is expressed in terms of the Lambert W function. We derive the transitionless driving Hamiltonian for the adiabatic search algorithm, which makes a quantum state follow the adiabatic path. We demonstrate that a uniform transitionless driving Hamiltonian, approximate to the exact time-dependent driving Hamiltonian, can alter the non-adiabatic transition probability from the inverse square decay to the inverse fourth power decay with the running time. This may open up a new but simple way of speeding up adiabatic quantum dynamics.

  20. Transitionless driving on adiabatic search algorithm

    NASA Astrophysics Data System (ADS)

    Oh, Sangchul; Kais, Sabre

    2014-12-01

    We study quantum dynamics of the adiabatic search algorithm with the equivalent two-level system. Its adiabatic and non-adiabatic evolution is studied and visualized as trajectories of Bloch vectors on a Bloch sphere. We find the change in the non-adiabatic transition probability from exponential decay for the short running time to inverse-square decay in asymptotic running time. The scaling of the critical running time is expressed in terms of the Lambert W function. We derive the transitionless driving Hamiltonian for the adiabatic search algorithm, which makes a quantum state follow the adiabatic path. We demonstrate that a uniform transitionless driving Hamiltonian, approximate to the exact time-dependent driving Hamiltonian, can alter the non-adiabatic transition probability from the inverse square decay to the inverse fourth power decay with the running time. This may open up a new but simple way of speeding up adiabatic quantum dynamics.

  1. Transitionless driving on adiabatic search algorithm.

    PubMed

    Oh, Sangchul; Kais, Sabre

    2014-12-14

    We study quantum dynamics of the adiabatic search algorithm with the equivalent two-level system. Its adiabatic and non-adiabatic evolution is studied and visualized as trajectories of Bloch vectors on a Bloch sphere. We find the change in the non-adiabatic transition probability from exponential decay for the short running time to inverse-square decay in asymptotic running time. The scaling of the critical running time is expressed in terms of the Lambert W function. We derive the transitionless driving Hamiltonian for the adiabatic search algorithm, which makes a quantum state follow the adiabatic path. We demonstrate that a uniform transitionless driving Hamiltonian, approximate to the exact time-dependent driving Hamiltonian, can alter the non-adiabatic transition probability from the inverse square decay to the inverse fourth power decay with the running time. This may open up a new but simple way of speeding up adiabatic quantum dynamics.

  2. Digital waveguide adiabatic passage part 1: theory

    NASA Astrophysics Data System (ADS)

    Vaitkus, Jesse A.; Steel, M. J.; Greentree, Andrew D.

    2017-03-01

    Spatial adiabatic passage represents a new way to design integrated photonic devices. In conventional adiabatic passage designs require smoothly varying waveguide separations. Here we show modelling of adiabatic passage devices where the waveguide separation is varied digitally. Despite digitisation, our designs show robustness against variations in the input wavelength and refractive index contrast of the waveguides relative to the cladding. This approach to spatial adiabatic passage opens new design strategies and hence the potential for new photonics devices.

  3. Auto-decompression system for engines

    SciTech Connect

    Onda, T.

    1988-12-13

    This patent describes a valve control device for an engine having a combustion chamber, a valve controlling communication with the chamber, a camshaft rotatably mounted in the engine, a valve motion cam fixed to the camshaft for rotation therewith, and a valve actuation mechanism including a cam follower engageable with the valve motion cam, the valve control device comprising: a decompression cam carried by the camshaft axially adjacent the valve motion cam, the decompression cam including a base circle portion defining an outer peripheral surface smaller in radial extent than the outer peripheral surface of the valve motion cam and having an inner bore to loosely encircle the camshaft; means for adjusting the position of the decomposition cam with respect to the camshaft between two locations including a first location on which the outer peripheral surface of the decompression cam extends radially outwardly from the axis of the camshaft to an extent greater than that of the valve motion cam to engage the cam follower for decompression operation of the valve, and a second location at which the outer peripheral surface of the decompression cam extends radially outwardly from the axis of the camshaft to an extent less than that of the valve motion cam whereby the valve motion cam engages the cam follower for normal operation of the valve; and means responsive to the rotational speed of the camshaft for automatically moving the decompression cam between the first and second locations.

  4. Acclimation to decompression sickness in rats.

    PubMed

    Montcalm-Smith, E A; McCarron, R M; Porter, W R; Lillo, R S; Thomas, J T; Auker, C R

    2010-03-01

    Protection against decompression sickness (DCS) by acclimation to hyperbaric decompression has been hypothesized but never proven. We exposed rats to acclimation dives followed by a stressful "test" dive to determine whether acclimation occurred. Experiments were divided into two phases. Phase 1 rats were exposed to daily acclimation dives of hyperbaric air for 30 min followed by rapid decompression on one of the following regimens: 70 ft of seawater (fsw) for 9 days (L70), 70 fsw for 4 days (S70), 40 fsw for 9 days (L40), 40 fsw for 4 days (S40), or unpressurized sham exposure for 9 days (Control). On the day following the last exposure, all were subjected to a "test" dive (175 fsw, 60 min, rapid decompression). Both L70 and S70 rats had significantly lower incidences of DCS than Control rats (36% and 41% vs. 62%, respectively). DCS incidences for the other regimens were lower than in Control rats but without statistical significance. Phase 2 used the most protective regimen from phase 1 (L70); rats were exposed to L70 or a similar regimen with a less stressful staged decompression. Another group was exposed to a single acclimation dive (70 fsw/30 min) on the day before the test dive. We observed a nonsignificant trend for the rapidly decompressed L70 dives to be more protective than staged decompression dives (44% vs. 51% DCS incidence). The single acclimation dive regimen did not provide protection. We conclude that protection against DCS can be attained with acclimating exposures that do not themselves cause DCS. The deeper acclimation dive regimens (70 fsw) provided the most protection.

  5. Delayed facial nerve decompression for Bell's palsy.

    PubMed

    Kim, Sang Hoon; Jung, Junyang; Lee, Jong Ha; Byun, Jae Yong; Park, Moon Suh; Yeo, Seung Geun

    2016-07-01

    Incomplete recovery of facial motor function continues to be long-term sequelae in some patients with Bell's palsy. The purpose of this study was to investigate the efficacy of transmastoid facial nerve decompression after steroid and antiviral treatment in patients with late stage Bell's palsy. Twelve patients underwent surgical decompression for Bell's palsy 21-70 days after onset, whereas 22 patients were followed up after steroid and antiviral therapy without decompression. Surgical criteria included greater than 90 % degeneration on electroneuronography and no voluntary electromyography potentials. This study was a retrospective study of electrodiagnostic data and medical chart review between 2006 and 2013. Recovery from facial palsy was assessed using the House-Brackmann grading system. Final recovery rate did not differ significantly in the two groups; however, all patients in the decompression group recovered to at least House-Brackmann grade III at final follow-up. Although postoperative hearing threshold was increased in both groups, there was no significant between group difference in hearing threshold. Transmastoid decompression of the facial nerve in patients with severe late stage Bell's palsy at risk for a poor facial nerve outcome reduced severe complications of facial palsy with minimal morbidity.

  6. Invalidity of the quantitative adiabatic condition and general conditions for adiabatic approximations

    NASA Astrophysics Data System (ADS)

    Li, Dafa

    2016-05-01

    The adiabatic theorem was proposed about 90 years ago and has played an important role in quantum physics. The quantitative adiabatic condition constructed from eigenstates and eigenvalues of a Hamiltonian is a traditional tool to estimate adiabaticity and has proven to be the necessary and sufficient condition for adiabaticity. However, recently the condition has become a controversial subject. In this paper, we list some expressions to estimate the validity of the adiabatic approximation. We show that the quantitative adiabatic condition is invalid for the adiabatic approximation via the Euclidean distance between the adiabatic state and the evolution state. Furthermore, we deduce general necessary and sufficient conditions for the validity of the adiabatic approximation by different definitions.

  7. The U.S. Navy decompression computer.

    PubMed

    Butler, F K; Southerland, D

    2001-01-01

    The U.S. Navy has recently approved the Cochran NAVY decompression computer (DC) for use in Naval Special Warfare diving. This action represents the first approval of a diver-worn DC for use in the U.S. Navy. This paper reviews the development and testing of both the decompression algorithm and the hardware chosen for the Navy's DC. The decompression software in the Cochran NAVY is the VVAL 18 algorithm developed at the Navy Experimental Diving Unit (NEDU) by Captain Ed Thalmann. A discussion of the relative conservatism of the VVAL18 algorithm in comparison to the U.S. Navy Standard Air Tables and the basis for the differences between the two is provided. The initial guidelines establishing DC diving practice for the Navy SEAL community are outlined as are plans for future research efforts in U.S. Navy DC diving.

  8. Decompressive laparotomy for abdominal compartment syndrome

    PubMed Central

    Kimball, E.; Malbrain, M.; Nesbitt, I.; Cohen, J.; Kaloiani, V.; Ivatury, R.; Mone, M.; Debergh, D.; Björck, M.

    2016-01-01

    Background The effect of decompressive laparotomy on outcomes in patients with abdominal compartment syndrome has been poorly investigated. The aim of this prospective cohort study was to describe the effect of decompressive laparotomy for abdominal compartment syndrome on organ function and outcomes. Methods This was a prospective cohort study in adult patients who underwent decompressive laparotomy for abdominal compartment syndrome. The primary endpoints were 28‐day and 1‐year all‐cause mortality. Changes in intra‐abdominal pressure (IAP) and organ function, and laparotomy‐related morbidity were secondary endpoints. Results Thirty‐three patients were included in the study (20 men). Twenty‐seven patients were surgical admissions treated for abdominal conditions. The median (i.q.r.) Acute Physiology And Chronic Health Evaluation (APACHE) II score was 26 (20–32). Median IAP was 23 (21–27) mmHg before decompressive laparotomy, decreasing to 12 (9–15), 13 (8–17), 12 (9–15) and 12 (9–14) mmHg after 2, 6, 24 and 72 h. Decompressive laparotomy significantly improved oxygenation and urinary output. Survivors showed improvement in organ function scores, but non‐survivors did not. Fourteen complications related to the procedure developed in eight of the 33 patients. The abdomen could be closed primarily in 18 patients. The overall 28‐day mortality rate was 36 per cent (12 of 33), which increased to 55 per cent (18 patients) at 1 year. Non‐survivors were no different from survivors, except that they tended to be older and on mechanical ventilation. Conclusion Decompressive laparotomy reduced IAP and had an immediate effect on organ function. It should be considered in patients with abdominal compartment syndrome. PMID:26891380

  9. Experimental results on decompression crystallization in an Aleutian basaltic-andesite

    NASA Astrophysics Data System (ADS)

    Larsen, J. F.; Gardner, J. E.

    2005-12-01

    In 1991-92, Westdahl volcano in the Aleutians erupted basaltic andesitic magma, producing lava fountaining and ash clouds to 2 km asl, resulting in a lava flow that extended about 7 km from vent. In order to understand the magmatic ascent rates during that relatively non-explosive eruption, this study compares plagioclase and orthopyroxene microlite textures in the basaltic andesite to crystallization kinetics of plagioclase and pyroxene in laboratory experiments. The experiments used melt-rich basaltic andesite that was hydrated at 150 MPa, 1000° C, and an oxygen fugacity of NNO. Before decompression, the starting material was mainly water-saturated melt that contained a few percent of Fe-Ti oxides and pargasite. Pieces of the starting material were then decompressed rapidly to 25 MPa, and held for various times. Preliminary results show that when held at low pressure for less than 1 hour no crystallization occurred, except for some growth around existing pargasite and oxides. In runs held for about an hour both enstatite and plagioclase nucleate and grow, and are skeletal. In runs held from 4 to 24 hours, plagioclase growth dominates, as enstatite remains a minor phase. The single-step decompressions will be compared with runs using multiple steps to examine how the kinetics change. We can then compare the results with observed crystallization textures in the Westdahl lava and tephra to infer the path and rate of magma ascent during that eruption.

  10. Hypobaric decompression prebreathe requirements and breathing environment

    NASA Technical Reports Server (NTRS)

    Webb, James T.; Pilmanis, Andrew A.

    1993-01-01

    To reduce incidence of decompression sickness (DCS), prebreathing 100 percent oxygen to denitrogenate is required prior to hypobaric decompressions from a sea level pressure breathing environment to pressures lower than 350 mm Hg (20,000 ft; 6.8 psia). The tissue ratio (TR) of such exposures equals or exceeds 1.7; TR being the tissue nitrogen pressure prior to decompression divided by the total pressure after decompression (((0.781)(14.697))/6.758). Designing pressure suits capable of greater pressure differentials, lower TR's, and procedures which limit the potential for DCS occurrence would enhance operational efficiency. The current 10.2 psia stage decompression prior to extravehicular activity (EVA) from the Shuttle in the 100 percent oxygen, 4.3 psia suit, results in a TR of 1.65 and has proven to be relatively free of DCS. Our recent study of zero-prebreathe decompressions to 6.8 psia breathing 100 percent oxygen (TR = 1.66) also resulted in no DCS (N = 10). The level of severe, Spencer Grades 3 or 4, venous gas emboli (VGE) increased from 0 percent at 9.5 psia to 40 percent at 6.8 psia yielding a Probit curve of VGE risk for the 51 male subjects who participated in these recent studies. Earlier, analogous decompressions using a 50 percent oxygen, 50 percent nitrogen breathing mixture resulted in one case of DCS and significantly higher levels of severe VGE, e.g., at 7.8 psia, the mixed gas breathing environment resulted in a 56 percent incidence of severe VGE versus 10 percent with use of 100 percent oxygen. The report of this study recommended use of 100 percent oxygen during zero-prebreathe exposure to 6.8 psia if such a suit could be developed. For future, long-term missions, we suggest study of the effects of decompression over several days to a breathing environment of 150 mmHg O2 and approximately 52 mmHg He as a means of eliminating DCS and VGE hazards during subsequent excursions. Once physiologically adapted to a 4 psia vehicle, base, or space

  11. Evidence Report: Risk of Decompression Sickness (DCS)

    NASA Technical Reports Server (NTRS)

    Conkin, Johnny; Norcross, Jason R.; Wessel, James H. III; Abercromby, Andrew F. J.; Klein, Jill S.; Dervay, Joseph P.; Gernhardt, Michael L.

    2013-01-01

    The Risk of Decompression Sickness (DCS) is identified by the NASA Human Research Program (HRP) as a recognized risk to human health and performance in space, as defined in the HRP Program Requirements Document (PRD). This Evidence Report provides a summary of the evidence that has been used to identify and characterize this risk. Given that tissue inert gas partial pressure is often greater than ambient pressure during phases of a mission, primarily during extravehicular activity (EVA), there is a possibility that decompression sickness may occur.

  12. Orbital decompression for severe dysthyroid eye disease.

    PubMed Central

    Fells, P

    1987-01-01

    Current methods of medical treatment of this difficult condition are briefly reviewed, with comments on the generally unsatisfactory response. Attention is therefore directed to surgical methods and a short history given of the various routes used for orbital decompression. The author's own results of transantral, and more recently ethmoidal, decompression are given, with a detailed description of the technique for the latter approach. An interesting frequent consequence of postoperative A pattern to the ocular movements is discussed in the light of Koornneef's concept of orbital fascial anatomy, and suggestions are made for its avoidance. Images PMID:3828262

  13. Theory of Adiabatic Fountain Resonance

    NASA Astrophysics Data System (ADS)

    Williams, Gary A.

    2017-01-01

    The theory of "Adiabatic Fountain Resonance" with superfluid ^4{He} is clarified. In this geometry a film region between two silicon wafers bonded at their outer edge opens up to a central region with a free surface. We find that the resonance in this system is not a Helmholtz resonance as claimed by Gasparini et al., but in fact is a fourth sound resonance. We postulate that it occurs at relatively low frequency because the thin silicon wafers flex appreciably from the pressure oscillations of the sound wave.

  14. Adiabatic Wankel type rotary engine

    NASA Technical Reports Server (NTRS)

    Kamo, R.; Badgley, P.; Doup, D.

    1988-01-01

    This SBIR Phase program accomplished the objective of advancing the technology of the Wankel type rotary engine for aircraft applications through the use of adiabatic engine technology. Based on the results of this program, technology is in place to provide a rotor and side and intermediate housings with thermal barrier coatings. A detailed cycle analysis of the NASA 1007R Direct Injection Stratified Charge (DISC) rotary engine was performed which concluded that applying thermal barrier coatings to the rotor should be successful and that it was unlikely that the rotor housing could be successfully run with thermal barrier coatings as the thermal stresses were extensive.

  15. Magnetite Nucleation in Mantle Xenoliths During Quasi-Adiabatic Ascent

    NASA Astrophysics Data System (ADS)

    Walsh, K. B., Jr.; Filiberto, J.; Friedman, S. A.; Knafelc, J.; Conder, J. A.; Ferre, E. C.; Khakhalova, E.; Feinberg, J. M.; Neal, C. R.; Ionov, D. A.; Hernandez, F. M.

    2014-12-01

    Can magnetite be a stable phase in the lithospheric mantle? Equilibrium-based thermodynamic calculations and petrologic models predict that it should not be stable. Studies of mantle xenoliths during the 1980s concluded that even though there were rare exceptions, mantle rocks do not host sufficient concentrations of ferromagnetic minerals and are too hot to allow any magnetic remanence. Thus, conventional wisdom dictates that the Moho constitutes a fundamental magnetic boundary. Yet, growing evidence from a more complete global mantle xenolith survey indicates the presence of ferromagnetic minerals in mantle materials. Examination of mantle xenoliths devoid of serpentinization and meteoric alteration show the presence of ferromagnetic minerals within primary silicate mineral phases, including olivine, pyroxene, and spinel. Nucleation of these magnetic minerals could occur at three different stages: in-situ in the mantle, upon ascent, and at the surface. This study reports the results of laboratory-based quasi-adiabatic decompression experiments that aim to simulate the ascent of mantle xenoliths through the lithosphere and test if magnetite growth is promoted during the process. The starting material for these experiments is San Carlos olivine, which holds a magnetic remanence of less than ~10-10 A/m2-1kg2 (the detection limit of the vibrating sample magnetometer). This low starting remanence will allow us to identify whether new magnetic minerals are formed during the decompression experiments using either vibrating sample magnetometry or SQUID-based rock magnetometers. All olivine grains in these experiments were hand-picked under a light microscope in an effort to avoid the inclusion of grains with spurious magnetic minerals. Olivine powders from these carefully selected grains will be used to represent average mantle olivine compositions (Fo90-Fo92). Experiments will start at 1 GPa and be decompressed to 0.3 GPa over 60 hrs at constant temperature (1200° C

  16. Ultrafast adiabatic second harmonic generation

    NASA Astrophysics Data System (ADS)

    Dahan, Asaf; Levanon, Assaf; Katz, Mordechai; Suchowski, Haim

    2017-03-01

    We introduce a generalization of the adiabatic frequency conversion method for an efficient conversion of ultrashort pulses in the full nonlinear regime. Our analysis takes into account dispersion as well as two-photon processes and Kerr effect, allowing complete analysis of any three waves with arbitrary phase mismatched design and any nonlinear optical process. We use this analysis to design an efficient and robust second harmonic generation, the most widely used nonlinear process for both fundamental and applied research. We experimentally show that such design not only allows for very efficient conversion of various of ultrashort pulses, but is also very robust to variations in the parameters of both the nonlinear crystal and the incoming light. These include variation of more than 100 °C in the crystal temperature, a wide bandwidth of up to 75 nm and a chirp variation of 300 fs to 3.5 ps of the incoming pulse. Also, we show the dependency of the adiabatic second harmonic generation design on the pump intensity and the crystal length. Our study shows that two photon absorption plays a critical role in such high influence nonlinear dynamics, and that it must be considered in order to achieve agreement with experimental results.

  17. Ultrafast adiabatic second harmonic generation.

    PubMed

    Dahan, Asaf; Levanon, Assaf; Katz, Mordechai; Suchowski, Haim

    2017-03-01

    We introduce a generalization of the adiabatic frequency conversion method for an efficient conversion of ultrashort pulses in the full nonlinear regime. Our analysis takes into account dispersion as well as two-photon processes and Kerr effect, allowing complete analysis of any three waves with arbitrary phase mismatched design and any nonlinear optical process. We use this analysis to design an efficient and robust second harmonic generation, the most widely used nonlinear process for both fundamental and applied research. We experimentally show that such design not only allows for very efficient conversion of various of ultrashort pulses, but is also very robust to variations in the parameters of both the nonlinear crystal and the incoming light. These include variation of more than 100 °C in the crystal temperature, a wide bandwidth of up to 75 nm and a chirp variation of 300 fs to 3.5 ps of the incoming pulse. Also, we show the dependency of the adiabatic second harmonic generation design on the pump intensity and the crystal length. Our study shows that two photon absorption plays a critical role in such high influence nonlinear dynamics, and that it must be considered in order to achieve agreement with experimental results.

  18. Phase relations and adiabats in boiling seafloor geothermal systems

    USGS Publications Warehouse

    Bischoff, J.L.; Pitzer, Kenneth S.

    1985-01-01

    Observations of large salinity variations and vent temperatures in the range of 380-400??C suggest that boiling or two-phase separation may be occurring in some seafloor geothermal systems. Consideration of flow rates and the relatively small differences in density between vapors and liquids at the supercritical pressures at depth in these systems suggests that boiling is occurring under closed-system conditions. Salinity and temperature of boiling vents can be used to estimate the pressure-temperature point in the subsurface at which liquid seawater first reached the two-phase boundary. Data are reviewed to construct phase diagrams of coexisting brines and vapors in the two-phase region at pressures corresponding to those of the seafloor geothermal systems. A method is developed for calculating the enthalpy and entropy of the coexisting mixtures, and results are used to construct adiabats from the seafloor to the P-T two-phase boundary. Results for seafloor vents discharging at 2300 m below sea level indicate that a 385??C vent is composed of a brine (7% NaCl equivalent) in equilibrium with a vapor (0.1% NaCl). Brine constitutes 45% by weight of the mixture, and the fluid first boiled at approximately 1 km below the seafloor at 415??C, 330 bar. A 400??C vent is primarily vapor (88 wt.%, 0.044% NaCl) with a small amount of brine (26% NaCl) and first boiled at 2.9 km below the seafloor at 500??C, 520 bar. These results show that adiabatic decompression in the two-phase region results in dramatic cooling of the fluid mixture when there is a large fraction of vapor. ?? 1985.

  19. A Pottery Electric Kiln Using Decompression

    NASA Astrophysics Data System (ADS)

    Naoe, Nobuyuki; Yamada, Hirofumi; Nakayama, Tetsuo; Nakayama, Minoru; Minamide, Akiyuki; Takemata, Kazuya

    This paper presents a novel type electric kiln which fires the pottery using the decompression. The electric kiln is suitable for the environment and the energy saving as the pottery furnace. This paper described the baking principle and the baking characteristic of the novel type electric kiln.

  20. Decompression Sickness Risk Versus Time and Altitude

    DTIC Science & Technology

    1993-11-01

    M, Wiegman J, Pilmanis exposure at 22,500 ft (Fig. 1-2) should raise AA. Prebreathe enhancement with concern since that level of decompression is...Andrew A. P11manis in a research phyniologist 2. Fischer MO, Wiegman JF, McLean SA, Olson Andrew A. ihi ish resiarch poycioo SRM. Evaluation of four

  1. Integrating Laboratory and Numerical Decompression Experiments to Investigate Fluid Dynamics into the Conduit

    NASA Astrophysics Data System (ADS)

    Spina, Laura; Colucci, Simone; De'Michieli Vitturi, Mattia; Scheu, Bettina; Dingwell, Donald Bruce

    2015-04-01

    The study of the fluid dynamics of magmatic melts into the conduit, where direct observations are unattainable, was proven to be strongly enhanced by multiparametric approaches. Among them, the coupling of numerical modeling with laboratory experiments represents a fundamental tool of investigation. Indeed, the experimental approach provide invaluable data to validate complex multiphase codes. We performed decompression experiments in a shock tube system, using pure silicon oil as a proxy for the basaltic melt. A range of viscosity comprised between 1 and 1000 Pa s was investigated. The samples were saturated with Argon for 72h at 10MPa, before being slowly decompressed to atmospheric pressure. The evolution of the analogue magmatic system was monitored through a high speed camera and pressure sensors, located into the analogue conduit. The experimental decompressions have then been reproduced numerically using a multiphase solver based on OpenFOAM framework. The original compressible multiphase Openfoam solver twoPhaseEulerFoam was extended to take into account the multicomponent nature of the fluid mixtures (liquid and gas) and the phase transition. According to the experimental conditions, the simulations were run with values of fluid viscosity ranging from 1 to 1000 Pa s. The sensitivity of the model has been tested for different values of the parameters t and D, representing respectively the relaxation time for gas exsolution and the average bubble diameter, required by the Gidaspow drag model. Valuable range of values for both parameters are provided from experimental observations, i.e. bubble nucleation time and bubble size distribution at a given pressure. The comparison of video images with the outcomes of the numerical models was performed by tracking the evolution of the gas volume fraction through time. Therefore, we were able to calibrate the parameter of the model by laboratory results, and to track the fluid dynamics of experimental decompression.

  2. Ethmoidectomy decompression for the treatment of Graves' optic neuropathy.

    PubMed

    Hurwitz, J J; Freeman, J L; Eplett, C J; Fliss, D M; Avram, D R

    1992-10-01

    When orbital decompression becomes necessary in Graves' optic neuropathy, medial wall decompression is a necessary component of the decompression procedure. The ethmoidectomy approach allows more direct visualization of the posterior ethmoids and sphenoids to effect maximum decompression. This is particularly important in cases in which computed tomography shows the medial rectus muscle to be enlarged posteriorly in the orbit. The procedure provides excellent visualization of the medial rectus. As with any medial wall decompression procedure, postoperative restriction of horizontal motility is a frequent complication, often necessitating more than one subsequent operation. The authors describe their experience with the procedure in 25 patients with Graves' optic neuropathy.

  3. CO2-rich melts generated during basalt magma ascent and degassing

    NASA Astrophysics Data System (ADS)

    Pichavant, M.; Di Carlo, I.; Rotolo, S.; Scaillet, B.; Burgisser, A.; Martel, C.

    2012-12-01

    To test mechanisms of basaltic magma degassing, experimental decompressions of volatile-bearing (2.7-3.8 wt% H2O, 600-1300 ppm CO2) Stromboli melts have been performed from 250-200 to 50-25 MPa at 1180-1140°C. Ascent rates were varied from 0.25 to ~ 1.5 m/s. Both the synthesis experiments that served to produce the volatile-bearing pre-decompression melts and the decompression experiments were performed in an internally heated vessel pressurized with Ar-H2 mixtures and fitted with a rapid-quench device. Charges were examined microscopically and by SEM. Vesicularities (% bubbles) were determined from image analysis on polished surfaces and in a few cases from X-ray microtomography. Electron microprobe analysis of post-decompression glasses shows that Fe loss to Au80Pd20 capsules is negligible. Concentrations of H2O and CO2 in both the pre- and post-decompression glasses, as well as their spatial distribution in the charge, were determined by FTIR. Glasses after decompression show a large range of vesicularities, from totally bubble-free to bubble-rich (~ 20 vol% bubbles), the latter with bubble number densities from 104 to 106/cm3, similar to Stromboli pumices. Bubble-poor or bubble-free samples (< 5 vol% bubbles) come from experiments decompressed either at constant rates to 50 MPa or at variable rates to 25 MPa. The bubble-rich charges are found among those decompressed under constant and fast ascent rates to 25 MPa. This suggest that, for our melt composition and dissolved volatile concentrations, homogeneous bubble nucleation requires a pressure drop of at least 150 MPa to be initiated. Varying ascent rates along the decompression path has a significant influence on bubble nucleation. Final melt H2O concentrations are homogeneous and in all cases close to solubilities. In contrast, the post-decompression melt CO2 concentrations are inversely correlated with vesicularities. Bubble-rich glasses have CO2 concentrations that follow theoretical closed

  4. An interacting adiabatic quantum motor

    NASA Astrophysics Data System (ADS)

    Viola Kusminskiy, Silvia; Bruch, Anton; von Oppen, Felix

    We consider the effect of electron-electron interactions on the performance of an adiabatic quantum motor based on a Thouless pump operating in reverse. We model such a device by electrons in a 1d wire coupled to a slowly moving periodic potential associated with the classical mechanical degree of freedom of the motor. This periodic degree of freedom is set into motion by a bias voltage applied to the 1d electron channel. We investigate the Thouless motor with interacting leads modeled as Luttinger liquids. We show that interactions enhance the energy gap opened by the periodic potential and thus the robustness of the Thouless motor against variations in the chemical potential. We show that the motor degree of freedom can be described as a mobile impurity in a Luttinger liquid obeying Langevin dynamics with renormalized coefficients due to interactions, for which we give explicit expressions.

  5. Quantum and classical dynamics in adiabatic computation

    NASA Astrophysics Data System (ADS)

    Crowley, P. J. D.; Äńurić, T.; Vinci, W.; Warburton, P. A.; Green, A. G.

    2014-10-01

    Adiabatic transport provides a powerful way to manipulate quantum states. By preparing a system in a readily initialized state and then slowly changing its Hamiltonian, one may achieve quantum states that would otherwise be inaccessible. Moreover, a judicious choice of final Hamiltonian whose ground state encodes the solution to a problem allows adiabatic transport to be used for universal quantum computation. However, the dephasing effects of the environment limit the quantum correlations that an open system can support and degrade the power of such adiabatic computation. We quantify this effect by allowing the system to evolve over a restricted set of quantum states, providing a link between physically inspired classical optimization algorithms and quantum adiabatic optimization. This perspective allows us to develop benchmarks to bound the quantum correlations harnessed by an adiabatic computation. We apply these to the D-Wave Vesuvius machine with revealing—though inconclusive—results.

  6. Ambulation Increases Decompression Sickness in Altitude Exposure

    NASA Technical Reports Server (NTRS)

    Conkin, Johnny; Pollock, N. W.; Natoli, M. J.; Wessel, J. H., III; Gernhardt, M. L.

    2014-01-01

    INTRODUCTION - Exercise accelerates inert gas elimination during oxygen breathing prior to decompression (prebreathe), but may also promote bubble formation and increase the risk of decompression sickness (DCS). The timing, pattern and intensity of exercise are likely critical to the net effect. The NASA Prebreathe Reduction Program (PRP) combined oxygen prebreathe and exercise preceding a 4.3 psi exposure in non-ambulatory subjects (a microgravity analog) to produce two protocols now used by astronauts preparing for extravehicular activity (CEVIS and ISLE). Additional work is required to investigate whether exercise normal to 1 G environments increases the risk of DCS over microgravity simulation. METHODS - The CEVIS protocol was replicated with one exception. Our subjects completed controlled ambulation (walking in place with fixed cadence and step height) during both preflight and at 4.3 psi instead of remaining non-ambulatory throughout. Decompression stress was graded with aural Doppler (Spencer 0-IV scale). Two-dimensional echocardiographic imaging was used to look for left heart gas emboli (the presence of which prompted test termination). Venous blood was collected at three points to correlate Doppler measures of decompression stress with microparticle (cell fragment) accumulation. Fisher Exact Tests compared test and control groups. Trial suspension would occur when DCS risk >15% or grade IV venous gas emboli (VGE) risk >20% (at 70% confidence). RESULTS - Eleven person-trials were completed (9 male, 2 female) when DCS prompted suspension. DCS was greater than in CEVIS trials (3/11 [27%] vs. 0/45 [0%], respectively, p=0.03). Statistical significance was not reached for peak grade IV VGE (2/11 [18%] vs. 3/45 [7%], p=0.149) or cumulative grade IV VGE observations per subject-trial (8/128 [6%] vs. 26/630 [4%], p=0.151). Microparticle data were collected for 5/11 trials (3 with DCS outcomes), with widely varying patterns that could not be resolved statistically

  7. Experimental fragmentation of crystal- and vesicle-bearing silicic melts

    NASA Astrophysics Data System (ADS)

    Martel, Caroline; Dingwell, Donald; Spieler, Oliver; Pichavant, Michel; Wilke, Max

    2001-07-01

    We experimentally investigate the effect of crystals on the fragmentation behavior of a three-phase (melt+gas+crystals) system under rapid decompression. Starting materials are cylinders of hydrated haplogranite melts containing alumina crystals that are placed at 6-30 MPa and 600-800°C in a fragmentation bomb for foaming. Subsequently, these bubble- and crystal-bearing melts are rapidly decompressed (within <1 s) to room pressure and temperature and the fragmented particles are recovered for analysis. We investigated the influence of the crystal size ( 70-350 µm in diameter), the crystal content (20-95 vol.%), and the magnitude of the decompression (6-30 MPa) on the fragment sizes. Crystals down to 70 µm in diameter have a strong influence on the fragment size distribution by defining fragments made of single crystals. Increasing the crystal content in the starting material leads to an increase of the average size of the fragments. Increasing the magnitude of the decompression generates finer fragments. Fragmentation threshold or dynamic tensile strength ranges from 10 MPa for crystal-poor samples up to >30 MPa for phenocryst- and microlite-bearing samples.

  8. Ultra-high mode mix in low-adiabat National Ignition Facility National Ignition Campaign implosions

    NASA Astrophysics Data System (ADS)

    Scott, Robert; Central Laser Facility Team

    2016-10-01

    This work re-examines a sub-set of the `slow-rise', low adiabat implosions from the National Ignition Campaign using the Hyades radiation-hydrodynamics code in an effort to better understand potential phenomenological sources of `excess' mix observed experimentally. An extensive effort has been made to match both shock-timing and backlit radiography (Con-A) implosion data in an effort to reproduce the experimental conditions as accurately as possible. A 30% reduction in ablation pressure at peak drive is required to match the experimental data. This reduced ablation pressure allows the ablator to decompress, in turn causing the DT ice-ablator interface to go Rayleigh-Taylor unstable early in the implosion acceleration phase. Post-processing the runs with various mix models indicates high-mode mix from the DT ice-ablator interface may penetrate deep into the hotspot. This work offers a potential explanation of why these low adiabat implosions exhibited significantly higher levels of mix than expected from high-fidelity multi-dimensional simulations. Through this new understanding a possible route forward for low-adiabat implosions on NIF is suggested.

  9. Temporal variations in the mantle potential temperatures along the Northwest Hawaiian Ridge using olivine-liquid equilibria: Implications for Hawaiian plume melt flux variations

    NASA Astrophysics Data System (ADS)

    Tree, J. P.; Garcia, M. O.; Putirka, K. D.

    2013-12-01

    The Northwest Hawaiian Ridge extends 2800 km and comprises 47% of the total length of the Hawaiian-Emperor (H-E) Chain. The Ridge contains at least 52 volcanoes whose shape, volume, and distance from neighboring volcanoes vary markedly. The temporal melt flux variation of the H-E has been estimated with various geophysical methods involving fluid dynamics and lithospheric modeling. These models show a dramatic increase (up to 300%) in melt flux over the last 30 Myr. A potential explanation for the increase in melt flux is a temporal increase in the temperature of melting. Olivine thermometry offers the best method for evaluating mantle source temperature variations along the Ridge. An olivine-liquid equilibration temperature estimate can then be recast into a mantle potential temperature after accounting for the heat of fusion during mantle melting and decompression of the mantle as it follows an adiabat to the surface. New whole-rock XRF and olivine analyzes for 18 tholeiitic, three transitional tholeiites, and two picro-basalts from 11 volcanoes spanning the entire length of the Ridge from Middle Bank to Yuryaku (just south of the Bend) were made. These data were used to obtain a temperature estimate of the mantle during shield formation of each volcano. After screening samples for those in chemical equilibrium using a Rhodes diagram and assuming a Kdol-liq(Fe-Mg)=0.345 ×0.03, data from six volcanoes were input into the thermometers of Beattie (1993; Contrib. Mineral. Petr., 118, 103-111) and Putirka et al., (2007; Chemical Geology, 241, 177-206). The results were averaged to estimate mantle potential temperatures. These calculations yield mantle potential temperature estimates that vary positively with volcano volume (e.g., 1460oC at Yuryaku vs 1608-1630oC at Gardner Pinnacles, the largest volume seamount in the Ridge). These results suggest that temperature variations may be playing a significant role in modulating the melt flux of the Ridge. Seven more

  10. Treatment of hemimasticatory spasm with microvascular decompression.

    PubMed

    Wang, Yong-Nan; Dou, Ning-Ning; Zhou, Qiu-Meng; Jiao, Wei; Zhu, Jin; Zhong, Jun; Li, Shi-Ting

    2013-01-01

    Hemimasticatory spasm is a rare disorder characterized by paroxysmal involuntary contraction of the jaw-closing muscles. As the ideology and pathogenesis of the disease are still unclear, there has been no treatment that could give rise to a good outcome so far. Herein, we tried to use surgical management to cure the disease. Six patients with the disease were included in this study. These patients underwent microvascular decompression of the motor fibers of the trigeminal root. After the operation, all faces of the patients felt relaxed at varied degrees, except for 1 patient. Our study showed that microvascular decompression of the trigeminal nerve could lead to a better outcome. However, a control study with a large sample is needed before this technique is widely used.

  11. Reversal of dysthyroid optic neuropathy following orbital fat decompression

    PubMed Central

    Kazim, M.; Trokel, S.; Acaroglu, G.; Elliott, A.

    2000-01-01

    AIMS—To document the successful treatment of five patients with dysthyroid optic neuropathy by orbital fat decompression instead of orbital bone decompression after failed medical therapy.
METHODS—Eight orbits of five patients with dysthyroid optic neuropathy were selected for orbital fat decompression as an alternative to bone removal decompression. Treatment with systemic corticosteroids and/or orbital radiotherapy was either unsuccessful or contraindicated in each case. All patients satisfied clinical indications for orbital bone decompression to reverse the optic neuropathy. High resolution computerised tomographic (CT) scans were performed in all cases and in each case showed signs of enlargement of the orbital fat compartment. As an alternative to bone decompression, orbital fat decompression was performed on all eight orbits.
RESULTS—Orbital fat decompression was performed on five patients (eight orbits) with optic neuropathy. Optic neuropathy was reversed in all cases. There were no cases of postoperative diplopia, enophthalmos, globe ptosis, or anaesthesia. All patients were followed for a minimum of 1 year.
CONCLUSIONS—In a subset of patients with an enlarged orbital fat compartment and in whom extraocular muscle enlargement is not the solitary cause of optic neuropathy, fat decompression is a surgical alternative to bony decompression.

 PMID:10837384

  12. Endothelial dysfunction correlates with decompression bubbles in rats

    PubMed Central

    Zhang, Kun; Wang, Dong; Jiang, Zhongxin; Ning, Xiaowei; Buzzacott, Peter; Xu, Weigang

    2016-01-01

    Previous studies have documented that decompression led to endothelial dysfunction with controversial results. This study aimed to clarify the relationship between endothelial dysfunction, bubble formation and decompression rate. Rats were subjected to simulated air dives with one of four decompression rates: one slow and three rapid. Bubble formation was detected ultrasonically following decompression for two hours, before measurement of endothelial related indices. Bubbles were found in only rapid-decompressed rats and the amount correlated with decompression rate with significant variability. Serum levels of ET-1, 6-keto-PGF1α, ICAM-1, VCAM-1 and MDA, lung Wet/Dry weight ratio and histological score increased, serum NO decreased following rapid decompression. Endothelial-dependent vasodilatation to Ach was reduced in pulmonary artery rings among rapid-decompressed rats. Near all the above changes correlated significantly with bubble amounts. The results suggest that bubbles may be the causative agent of decompression–induced endothelial damage and bubble amount is of clinical significance in assessing decompression stress. Furthermore, serum levels of ET-1 and MDA may serve as sensitive biomarkers with the capacity to indicate endothelial dysfunction and decompression stress following dives. PMID:27615160

  13. Recreational technical diving part 2: decompression from deep technical dives.

    PubMed

    Doolette, David J; Mitchell, Simon J

    2013-06-01

    Technical divers perform deep, mixed-gas 'bounce' dives, which are inherently inefficient because even a short duration at the target depth results in lengthy decompression. Technical divers use decompression schedules generated from modified versions of decompression algorithms originally developed for other types of diving. Many modifications ostensibly produce shorter and/or safer decompression, but have generally been driven by anecdote. Scientific evidence relevant to many of these modifications exists, but is often difficult to locate. This review assembles and examines scientific evidence relevant to technical diving decompression practice. There is a widespread belief that bubble algorithms, which redistribute decompression in favour of deeper decompression stops, are more efficient than traditional, shallow-stop, gas-content algorithms, but recent laboratory data support the opposite view. It seems unlikely that switches from helium- to nitrogen-based breathing gases during ascent will accelerate decompression from typical technical bounce dives. However, there is evidence for a higher prevalence of neurological decompression sickness (DCS) after dives conducted breathing only helium-oxygen than those with nitrogen-oxygen. There is also weak evidence suggesting less neurological DCS occurs if helium-oxygen breathing gas is switched to air during decompression than if no switch is made. On the other hand, helium-to-nitrogen breathing gas switches are implicated in the development of inner-ear DCS arising during decompression. Inner-ear DCS is difficult to predict, but strategies to minimize the risk include adequate initial decompression, delaying helium-to-nitrogen switches until relatively shallow, and the use of the maximum safe fraction of inspired oxygen during decompression.

  14. Adiabatic heating in impulsive solar flares

    NASA Technical Reports Server (NTRS)

    Maetzler, C.; Bai, T.; Crannell, C. J.; Frost, K. J.

    1977-01-01

    The dynamic X-ray spectra of two simple, impulsive solar flares are examined together with H alpha, microwave and meter wave radio observations. X-ray spectra of both events were characteristic of thermal bremsstrahlung from single temperature plasmas. The symmetry between rise and fall was found to hold for the temperature and emission measure. The relationship between temperature and emission measure was that of an adiabatic compression followed by adiabatic expansion; the adiabatic index of 5/3 indicated that the electron distribution remained isotropic. Observations in H alpha provided further evidence for compressive energy transfer.

  15. Laboratory and numerical decompression experiments: an insight into the nucleation and growth of bubbles

    NASA Astrophysics Data System (ADS)

    Spina, L.; Colucci, S.; De'Michieli Vitturi, M.; Scheu, B.; Dingwell, D. B.

    2014-12-01

    Numerical modeling, joined with experimental investigations, is fundamental for studying the dynamics of magmatic fluid into the conduit, where direct observations are unattainable. Furthermore, laboratory experiments can provide invaluable data to vunalidate complex multiphase codes. With the aim on unveil the essence of nucleation process, as well as the behavior of the multiphase magmatic fluid, we performed slow decompression experiments in a shock tube system. We choose silicon oil as analogue for the magmatic melt, and saturated it with Argon at 10 MPa for 72h. The slow decompression to atmospheric conditions was monitored through a high speed camera and pressure sensors, located into the experimental conduit. The experimental conditions of the decompression process have then been reproduced numerically with a compressible multiphase solver based on OpenFOAM. Numerical simulations have been performed by the OpenFOAM compressibleInterFoam solver for 2 compressible, non-isothermal immiscible fluids, using a VOF (volume of fluid) phase-fraction based interface capturing approach. The data extracted from 2D images obtained from laboratory analyses were compared to the outcome of numerical investigation, showing the capability of the model to capture the main processes studied.

  16. Experimental demonstration of composite adiabatic passage

    NASA Astrophysics Data System (ADS)

    Schraft, Daniel; Halfmann, Thomas; Genov, Genko T.; Vitanov, Nikolay V.

    2013-12-01

    We report an experimental demonstration of composite adiabatic passage (CAP) for robust and efficient manipulation of two-level systems. The technique represents a altered version of rapid adiabatic passage (RAP), driven by composite sequences of radiation pulses with appropriately chosen phases. We implement CAP with radio-frequency pulses to invert (i.e., to rephase) optically prepared spin coherences in a Pr3+:Y2SiO5 crystal. We perform systematic investigations of the efficiency of CAP and compare the results with conventional π pulses and RAP. The data clearly demonstrate the superior features of CAP with regard to robustness and efficiency, even under conditions of weakly fulfilled adiabaticity. The experimental demonstration of composite sequences to support adiabatic passage is of significant relevance whenever a high efficiency or robustness of coherent excitation processes need to be maintained, e.g., as required in quantum information technology.

  17. Adiabatic Quantum Search in Open Systems.

    PubMed

    Wild, Dominik S; Gopalakrishnan, Sarang; Knap, Michael; Yao, Norman Y; Lukin, Mikhail D

    2016-10-07

    Adiabatic quantum algorithms represent a promising approach to universal quantum computation. In isolated systems, a key limitation to such algorithms is the presence of avoided level crossings, where gaps become extremely small. In open quantum systems, the fundamental robustness of adiabatic algorithms remains unresolved. Here, we study the dynamics near an avoided level crossing associated with the adiabatic quantum search algorithm, when the system is coupled to a generic environment. At zero temperature, we find that the algorithm remains scalable provided the noise spectral density of the environment decays sufficiently fast at low frequencies. By contrast, higher order scattering processes render the algorithm inefficient at any finite temperature regardless of the spectral density, implying that no quantum speedup can be achieved. Extensions and implications for other adiabatic quantum algorithms will be discussed.

  18. Adiabatic Quantum Search in Open Systems

    NASA Astrophysics Data System (ADS)

    Wild, Dominik S.; Gopalakrishnan, Sarang; Knap, Michael; Yao, Norman Y.; Lukin, Mikhail D.

    2016-10-01

    Adiabatic quantum algorithms represent a promising approach to universal quantum computation. In isolated systems, a key limitation to such algorithms is the presence of avoided level crossings, where gaps become extremely small. In open quantum systems, the fundamental robustness of adiabatic algorithms remains unresolved. Here, we study the dynamics near an avoided level crossing associated with the adiabatic quantum search algorithm, when the system is coupled to a generic environment. At zero temperature, we find that the algorithm remains scalable provided the noise spectral density of the environment decays sufficiently fast at low frequencies. By contrast, higher order scattering processes render the algorithm inefficient at any finite temperature regardless of the spectral density, implying that no quantum speedup can be achieved. Extensions and implications for other adiabatic quantum algorithms will be discussed.

  19. General conditions for quantum adiabatic evolution

    SciTech Connect

    Comparat, Daniel

    2009-07-15

    Adiabaticity occurs when, during its evolution, a physical system remains in the instantaneous eigenstate of the Hamiltonian. Unfortunately, existing results, such as the quantum adiabatic theorem based on a slow down evolution [H({epsilon}t),{epsilon}{yields}0], are insufficient to describe an evolution driven by the Hamiltonian H(t) itself. Here we derive general criteria and exact bounds, for the state and its phase, ensuring an adiabatic evolution for any Hamiltonian H(t). As a corollary, we demonstrate that the commonly used condition of a slow Hamiltonian variation rate, compared to the spectral gap, is indeed sufficient to ensure adiabaticity but only when the Hamiltonian is real and nonoscillating (for instance, containing exponential or polynomial but no sinusoidal functions)

  20. Adiabatic limits on Riemannian Heisenberg manifolds

    SciTech Connect

    Yakovlev, A A

    2008-02-28

    An asymptotic formula is obtained for the distribution function of the spectrum of the Laplace operator, in the adiabatic limit for the foliation defined by the orbits of an invariant flow on a compact Riemannian Heisenberg manifold. Bibliography: 21 titles.

  1. Simulation of periodically focused, adiabatic thermal beams

    SciTech Connect

    Chen, C.; Akylas, T. R.; Barton, T. J.; Field, D. M.; Lang, K. M.; Mok, R. V.

    2012-12-21

    Self-consistent particle-in-cell simulations are performed to verify earlier theoretical predictions of adiabatic thermal beams in a periodic solenoidal magnetic focusing field [K.R. Samokhvalova, J. Zhou and C. Chen, Phys. Plasma 14, 103102 (2007); J. Zhou, K.R. Samokhvalova and C. Chen, Phys. Plasma 15, 023102 (2008)]. In particular, results are obtained for adiabatic thermal beams that do not rotate in the Larmor frame. For such beams, the theoretical predictions of the rms beam envelope, the conservations of the rms thermal emittances, the adiabatic equation of state, and the Debye length are verified in the simulations. Furthermore, the adiabatic thermal beam is found be stable in the parameter regime where the simulations are performed.

  2. Symmetry of the Adiabatic Condition in the Piston Problem

    ERIC Educational Resources Information Center

    Anacleto, Joaquim; Ferreira, J. M.

    2011-01-01

    This study addresses a controversial issue in the adiabatic piston problem, namely that of the piston being adiabatic when it is fixed but no longer so when it can move freely. It is shown that this apparent contradiction arises from the usual definition of adiabatic condition. The issue is addressed here by requiring the adiabatic condition to be…

  3. [Ethmoidectomy and orbital decompression in endocrine ophthalmopathy].

    PubMed

    Richter, W C; Kley, W; Buschmann, W

    1984-07-01

    23 orbita decompression operations were performed in patients suffering from endocrine exophthalmos (Grave's disease) after normalization of thyroid metabolism and systemic corticoid therapy remained unsuccessful. We developed a modification of an external ethmoidectomy. The lamina of the middle nasal concha is carefully preserved, any opening to the nasal cavity is closed. Flap door incisions of the periorbita complete this procedure. Results are good and were followed up for a period of 30 months. The operation resulted in prompt restitution of normal eye position with fast normalization of visual acuity and field. Squint surgery was done in addition.

  4. Assessment of total efficiency in adiabatic engines

    NASA Astrophysics Data System (ADS)

    Mitianiec, W.

    2016-09-01

    The paper presents influence of ceramic coating in all surfaces of the combustion chamber of SI four-stroke engine on working parameters mainly on heat balance and total efficiency. Three cases of engine were considered: standard without ceramic coating, fully adiabatic combustion chamber and engine with different thickness of ceramic coating. Consideration of adiabatic or semi-adiabatic engine was connected with mathematical modelling of heat transfer from the cylinder gas to the cooling medium. This model takes into account changeable convection coefficient based on the experimental formulas of Woschni, heat conductivity of multi-layer walls and also small effect of radiation in SI engines. The simulation model was elaborated with full heat transfer to the cooling medium and unsteady gas flow in the engine intake and exhaust systems. The computer program taking into account 0D model of engine processes in the cylinder and 1D model of gas flow was elaborated for determination of many basic engine thermodynamic parameters for Suzuki DR-Z400S 400 cc SI engine. The paper presents calculation results of influence of the ceramic coating thickness on indicated pressure, specific fuel consumption, cooling and exhaust heat losses. Next it were presented comparisons of effective power, heat losses in the cooling and exhaust systems, total efficiency in function of engine rotational speed and also comparison of temperature inside the cylinder for standard, semi-adiabatic and full adiabatic engine. On the basis of the achieved results it was found higher total efficiency of adiabatic engines at 2500 rpm from 27% for standard engine to 37% for full adiabatic engine.

  5. Colonic Fermentation Promotes Decompression sickness in Rats

    PubMed Central

    de Maistre, Sébastien; Vallée, Nicolas; Gempp, Emmanuel; Lambrechts, Kate; Louge, Pierre; Duchamp, Claude; Blatteau, Jean-Eric

    2016-01-01

    Massive bubble formation after diving can lead to decompression sickness (DCS). During dives with hydrogen as a diluent for oxygen, decreasing the body’s H2 burden by inoculating hydrogen-metabolizing microbes into the gut reduces the risk of DCS. So we set out to investigate if colonic fermentation leading to endogenous hydrogen production promotes DCS in fasting rats. Four hours before an experimental dive, 93 fasting rats were force-fed, half of them with mannitol and the other half with water. Exhaled hydrogen was measured before and after force-feeding. Following the hyperbaric exposure, we looked for signs of DCS. A higher incidence of DCS was found in rats force-fed with mannitol than in those force-fed with water (80%, [95%CI 56, 94] versus 40%, [95%CI 19, 64], p < 0.01). In rats force-fed with mannitol, metronidazole pretreatment reduced the incidence of DCS (33%, [95%CI 15, 57], p = 0.005) at the same time as it inhibited colonic fermentation (14 ± 35 ppm versus 118 ± 90 ppm, p = 0.0001). Pre-diveingestion of mannitol increased the incidence of DCS in fasting rats when colonic fermentation peaked during the decompression phase. More generally, colonic fermentation in rats on a normal diet could promote DCS through endogenous hydrogen production. PMID:26853722

  6. Optic Nerve Decompression through a Supraorbital Approach

    PubMed Central

    Rigante, Luigi; Evins, Alexander I.; Berra, Luigi V.; Beer-Furlan, André; Stieg, Philip E.; Bernardo, Antonio

    2015-01-01

    Objective We propose a stepwise decompression of the optic nerve (ON) through a supraorbital minicraniotomy and describe the surgical anatomy of the ON as seen through this approach. We also discuss the clinical applications of this approach. Methods Supraorbital approaches were performed on 10 preserved cadaveric heads (20 sides). First, 3.5-cm skin incisions were made along the supraciliary arch from the medial third of the orbit and extended laterally. A 2 × 3-cm bone flap was fashioned and extradural dissections were completed. A 180-degree unroofing of the ON was achieved, and the length and width of the proximal and distal portions of the optic canal (OC) were measured. Results The supraorbital minicraniotomy allowed for identification of the anterior clinoid process and other surgical landmarks and adequate drilling of the roof of the OC with a comfortable working angle. A 25-degree contralateral head rotation facilitated visualization of the ON. Conclusion The supraorbital approach is a minimally invasive and cosmetically favorable alternative to more extended approaches with longer operative times used for the management of ON decompression in posttraumatic or compressive optic neuropathy from skull base pathologies extending into the OC. The relative ease of this approach provides a relatively short learning curve for developing neurosurgeons. PMID:26225308

  7. Submarine tower escape decompression sickness risk estimation.

    PubMed

    Loveman, G A M; Seddon, E M; Thacker, J C; Stansfield, M R; Jurd, K M

    2014-01-01

    Actions to enhance survival in a distressed submarine (DISSUB) scenario may be guided in part by knowledge of the likely risk of decompression sickness (DCS) should the crew attempt tower escape. A mathematical model for DCS risk estimation has been calibrated against DCS outcome data from 3,738 exposures of either men or goats to raised pressure. Body mass was used to scale DCS risk. The calibration data included more than 1,000 actual or simulated submarine escape exposures and no exposures with substantial staged decompression. Cases of pulmonary barotrauma were removed from the calibration data. The calibrated model was used to estimate the likelihood of DCS occurrence following submarine escape from the United Kingdom Royal Navy tower escape system. Where internal DISSUB pressure remains at - 0.1 MPa, escape from DISSUB depths < 200 meters is estimated to have DCS risk < 6%. Saturation at raised DISSUB pressure markedly increases risk, with > 60% DCS risk predicted for a 200-meter escape from saturation at 0.21 MPa. Using the calibrated model to predict DCS for direct ascent from saturation gives similar risk estimates to other published models.

  8. Sulfur Isotope Variation in Melt Inclusions From Arc Basalts Revealed By Secondary Ion Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Mandeville, C. W.; Shimizu, N.; Kelley, K. A.

    2009-12-01

    Subduction zones are sites where elements once at the Earth’s surface are recycled back to the mantle. Arc volcanoes return volatiles and hydrous melts to the surface. Understanding of sulfur recycling in magmatic arcs is hampered by insufficient data on net sulfur isotopic composition of slab inputs, that range from δ34S of seawater (21‰) to negative δ34S of -70‰ for secondary sulfides, to values of 0 ± 3‰ in relict magmatic sulfides. We lack sufficient knowledge of the sulfur concentration and isotopic composition of the mantle wedge. Degassing and assimilation of crustal sulfur may produce changes to initial sulfur isotope ratios of magmas. To preclude degassing effects, we measured S isotope ratios in mafic melt inclusions by secondary ionization mass spectrometry (SIMS) from three arc volcanoes, Galunggung, and Krakatau in Indonesia, and Augustine, in Alaska. These data provide a view of the variability of initial sulfur isotope ratios of mafic arc magmas and are being evaluated for correlations with sulfur and iron oxidation state, dissolved volatiles, trace elements, and degassing effects in order to determine the origin(s) of dissolved S. Olivine-hosted melt inclusions from a basaltic bomb from the 1982-1983 Galunggung eruption represent the relatively dry adiabatic decompression melting end member of primary arc magma genesis (Sisson and Bronto,1998). New SIMS δ34S measurements of Galunggung melt inclusions yield ratios from -3.0‰ to +5.0‰ with S concentrations of 1950 ppm - 990 ppm. A few Galunggung inclusions have δ34S between 0.5‰ and 1.4‰ with S conc.'s of 1690 - 1760 ppm, that are within the mantle range, and have low water contents of 0.25 to 0.30 wt.% (Kelley et al. 2005). A subgroup of inclusions yield δ34S of 2.8‰ to 5.0‰ and 990 - 1920 ppm S. Pre-1883 basaltic scoria from Krakatau volcano contain olivine-hosted melt inclusions with water and CO2 concentrations from 1.8 - 4.1 wt.% and 79 - 1017 ppm, respectively

  9. Dissolved water distribution in vesicular magmatic glass records both decompressive bubble growth and quench resorption

    NASA Astrophysics Data System (ADS)

    McIntosh, I. M.; Llewellin, E.; Humphreys, M.; Nichols, A. R.; Burgisser, A.; Schipper, C.

    2013-12-01

    Water distribution in magma varies over the lifetime of an eruption due to a variety of processes, including decompressive degassing of the melt, cooling during the quench from melt to glass, and post-emplacement hydration under ambient conditions. Correct interpretation of water distributions in erupted pyroclasts can therefore offer crucial insights into the dynamics of eruption mechanisms and emplacement histories. Volcanic eruptions are driven by the nucleation and growth of bubbles in magma. Bubbles grow as volatile species in the melt, of which water is volumetrically the most important, diffuse down a concentration gradient towards and across the bubble wall. On cooling, the melt quenches to glass, preserving the spatial distribution of water concentration around the bubbles (now vesicles). We use Backscatter Scanning Electron Microscopy (BSEM), Secondary Ion Mass Spectrometry (SIMS) and Fourier Transform Infra-Red spectroscopy (FTIR) to measure the spatial distribution of water around vesicles in experimentally-vesiculated samples. We find that, contrary to expectation, the total water concentration increases (by up to 2 wt.%) in the ~30 microns closest to the vesicle wall. Our samples record significant resorption of water back into the melt around bubbles during the quench process, a process which represents ';regassing' of the magma. We propose that the observed total water resorption profiles result from the increase in the equilibrium solubility of water as temperature decreases during the quench to glass, and that this resorption locally overprints the pre-existing concentration total water profile resulting from bubble growth during decompression. This resorption occurs over the very short timescales of rapid experimental quench (3-10 seconds) resulting in strongly disequilibrium water speciation. Water re-enters the melt as molecular water leading to enrichment in molecular water around vesicles, while the distribution of hydroxyl groups remains

  10. Cardiovascular Pressures with Venous Gas Embolism and Decompression

    NASA Technical Reports Server (NTRS)

    Butler, B. D.; Robinson, R.; Sutton, T.; Kemper, G. B.

    1995-01-01

    Venous gas embolism (VGE) is reported with decompression to a decreased ambient pressure. With severe decompression, or in cases where an intracardiac septal defect (patent foramen ovale) exists, the venous bubbles can become arterialized and cause neurological decompression illness. Incidence rates of patent foramen ovale in the general population range from 25-34% and yet aviators, astronauts, and deepsea divers who have decompression-induced venous bubbles do not demonstrate neurological symptoms at these high rates. This apparent disparity may be attributable to the normal pressure gradient across the atria of the heart that must be reversed for there to be flow potency. We evaluated the effects of: venous gas embolism (0.025, 0.05 and 0.15 ml/ kg min for 180 min.) hyperbaric decompression; and hypobaric decompression on the pressure gradient across the left and right atria in anesthetized dogs with intact atrial septa. Left ventricular end-diastolic pressure was used as a measure of left atrial pressure. In a total of 92 experimental evaluations in 22 dogs, there were no reported reversals in the mean pressure gradient across the atria; a total of 3 transient reversals occurred during the peak pressure gradient changes. The reasons that decompression-induced venous bubbles do not consistently cause serious symptoms of decompression illness may be that the amount of venous gas does not always cause sufficient pressure reversal across a patent foramen ovale to cause arterialization of the venous bubbles.

  11. The importance of the melting process for quantifying mantle heterogeneity

    NASA Astrophysics Data System (ADS)

    Lambart, S.

    2015-12-01

    A variety of data requires that the mantle source for basaltic magmatism is heterogeneous. Thanks to numerous experimental studies, parameterizations are available to model the melting behavior of peridotite and pyroxenite compositions that are thought to be present in the mantle (e.g., 1, 2). Based on these parameterizations, numerous studies have attempted to estimate the proportion of pyroxenites in magmatic sources. However, while almost all melting experiments correspond to a batch melting process, it is likely that oceanic basalts are formed by near fractional melting rather than batch melting (e.g., 3). Due to the limited extent of melting of peridotites under upper mantle conditions, their magmatic productivity and melt compositions are similar for batch and fractional melting (e.g., 4). In contrast, pyroxenites undergo much higher meting degrees during decompression of a heterogeneous, peridotite-rich mantle source. Using pMELTS, I investigated the effect of near-fractional melting of pyroxenite. Results suggest that the nature of the melting process for pyroxenites can significantly affect (1) the melt productivity of pyroxenites and thus their potential contribution in basalt genesis, (2) the major element composition of melts and thus their interaction with the surrounding peridodite, and (3) the concentration of minor elements such as Ni and consequently the estimation of pyroxenite proportion in magma-source (e.g., 5). In particular, calculations imply that the proportion of solid pyroxenite in the magma source is likely to be underestimated using "batch melting" rather than "fractional melting" parameterization. An increase in the pyroxenite proportion may affect the buoyancy of the mixture in the upper mantle and have important geodynamical implications. 1-Katz et al., 2003, GGG 4; 2-Lambart et al., 2013, Lithos 160-161; 3- Hirose & Kawamura, 1994, Geophy. Res. Let 21; 4-Johnson et al., 1990, J. Geophy. Res. 95; 5-Sobolev et al., 2007, Science 316

  12. Ambulation Increases Decompression Sickness in Spacewalk Simulations

    NASA Technical Reports Server (NTRS)

    Pollock, N. W.; Natoli, M. J.; Conkin, J.; Wessel, J. H., III; Gernhardt, M. L.

    2014-01-01

    Musculoskeletal activity has the potential to both improve and compromise decompression safety. Exercise enhances inert gas elimination during oxygen breathing prior to decompression (prebreathe), but it may also promote bubble nuclei formation (nucleation), which can lead to gas phase separation and bubble growth and increase the risk of decompression sickness (DCS). The timing, pattern and intensity of musculoskeletal activity and the level of tissue supersaturation may be critical to the net effect. Understanding the relationships is important to evaluate exercise prebreathe protocols and quantify decompression risk in gravity and microgravity environments. Data gathered during NASA's Prebreathe Reduction Program (PRP) studies combined oxygen prebreathe and exercise followed by low pressure (4.3 psi; altitude equivalent of 30,300 ft [9,235 m]) microgravity simulation to produce two protocols used by astronauts preparing for extravehicular activity. Both the Phase II/CEVIS (cycle ergometer vibration isolation system) and ISLE (in-suit light exercise) trials eliminated ambulation to more closely simulate the microgravity environment. The CEVIS results (35 male, 10 female) serve as control data for this NASA/Duke study to investigate the influence of ambulation exercise on bubble formation and the subsequent risk of DCS. METHODS Four experiments will replicate the CEVIS exercise-enhanced oxygen prebreathe protocol, each with a different exception. The first of these is currently underway. Experiment 1 - Subjects complete controlled ambulation (walking in place with fixed cadence and step height) during both preflight and at 4.3 psi instead of remaining nonambulatory throughout. Experiment 2 - Subjects remain non-ambulatory during the preflight period and ambulatory at 4.3 psi. Experiment 3 - Subjects ambulate during the preflight period and remain non-ambulatory at 4.3 psi. Experiment 4 - The order of heavy and light exercise employed in the CEVIS protocol is

  13. Adiabatic optimization versus diffusion Monte Carlo methods

    NASA Astrophysics Data System (ADS)

    Jarret, Michael; Jordan, Stephen P.; Lackey, Brad

    2016-10-01

    Most experimental and theoretical studies of adiabatic optimization use stoquastic Hamiltonians, whose ground states are expressible using only real nonnegative amplitudes. This raises a question as to whether classical Monte Carlo methods can simulate stoquastic adiabatic algorithms with polynomial overhead. Here we analyze diffusion Monte Carlo algorithms. We argue that, based on differences between L1 and L2 normalized states, these algorithms suffer from certain obstructions preventing them from efficiently simulating stoquastic adiabatic evolution in generality. In practice however, we obtain good performance by introducing a method that we call Substochastic Monte Carlo. In fact, our simulations are good classical optimization algorithms in their own right, competitive with the best previously known heuristic solvers for MAX-k -SAT at k =2 ,3 ,4 .

  14. Nonadiabatic exchange dynamics during adiabatic frequency sweeps.

    PubMed

    Barbara, Thomas M

    2016-04-01

    A Bloch equation analysis that includes relaxation and exchange effects during an adiabatic frequency swept pulse is presented. For a large class of sweeps, relaxation can be incorporated using simple first order perturbation theory. For anisochronous exchange, new expressions are derived for exchange augmented rotating frame relaxation. For isochronous exchange between sites with distinct relaxation rate constants outside the extreme narrowing limit, simple criteria for adiabatic exchange are derived and demonstrate that frequency sweeps commonly in use may not be adiabatic with regard to exchange unless the exchange rates are much larger than the relaxation rates. Otherwise, accurate assessment of the sensitivity to exchange dynamics will require numerical integration of the rate equations. Examples of this situation are given for experimentally relevant parameters believed to hold for in-vivo tissue. These results are of significance in the study of exchange induced contrast in magnetic resonance imaging.

  15. Complexity of the Quantum Adiabatic Algorithm

    NASA Technical Reports Server (NTRS)

    Hen, Itay

    2013-01-01

    The Quantum Adiabatic Algorithm (QAA) has been proposed as a mechanism for efficiently solving optimization problems on a quantum computer. Since adiabatic computation is analog in nature and does not require the design and use of quantum gates, it can be thought of as a simpler and perhaps more profound method for performing quantum computations that might also be easier to implement experimentally. While these features have generated substantial research in QAA, to date there is still a lack of solid evidence that the algorithm can outperform classical optimization algorithms.

  16. On black hole spectroscopy via adiabatic invariance

    NASA Astrophysics Data System (ADS)

    Jiang, Qing-Quan; Han, Yan

    2012-12-01

    In this Letter, we obtain the black hole spectroscopy by combining the black hole property of adiabaticity and the oscillating velocity of the black hole horizon. This velocity is obtained in the tunneling framework. In particular, we declare, if requiring canonical invariance, the adiabatic invariant quantity should be of the covariant form Iadia = ∮pi dqi. Using it, the horizon area of a Schwarzschild black hole is quantized independently of the choice of coordinates, with an equally spaced spectroscopy always given by ΔA = 8 π lp2 in the Schwarzschild and Painlevé coordinates.

  17. On adiabatic invariant in generalized Galileon theories

    SciTech Connect

    Ema, Yohei; Jinno, Ryusuke; Nakayama, Kazunori; Mukaida, Kyohei E-mail: jinno@hep-th.phys.s.u-tokyo.ac.jp E-mail: kazunori@hep-th.phys.s.u-tokyo.ac.jp

    2015-10-01

    We consider background dynamics of generalized Galileon theories in the context of inflation, where gravity and inflaton are non-minimally coupled to each other. In the inflaton oscillation regime, the Hubble parameter and energy density oscillate violently in many cases, in contrast to the Einstein gravity with minimally coupled inflaton. However, we find that there is an adiabatic invariant in the inflaton oscillation regime in any generalized Galileon theory. This adiabatic invariant is useful in estimating the expansion law of the universe and also the particle production rate due to the oscillation of the Hubble parameter.

  18. Spontaneous emission in stimulated Raman adiabatic passage

    SciTech Connect

    Ivanov, P. A.; Vitanov, N. V.; Bergmann, K.

    2005-11-15

    This work explores the effect of spontaneous emission on the population transfer efficiency in stimulated Raman adiabatic passage (STIRAP). The approach uses adiabatic elimination of weakly coupled density matrix elements in the Liouville equation, from which a very accurate analytic approximation is derived. The loss of population transfer efficiency is found to decrease exponentially with the factor {omega}{sub 0}{sup 2}/{gamma}, where {gamma} is the spontaneous emission rate and {omega}{sub 0} is the peak Rabi frequency. The transfer efficiency increases with the pulse delay and reaches a steady value. For large pulse delay and large spontaneous emission rate STIRAP degenerates into optical pumping.

  19. Adiabatic Hyperspherical Analysis of Realistic Nuclear Potentials

    NASA Astrophysics Data System (ADS)

    Daily, K. M.; Kievsky, Alejandro; Greene, Chris H.

    2015-12-01

    Using the hyperspherical adiabatic method with the realistic nuclear potentials Argonne V14, Argonne V18, and Argonne V18 with the Urbana IX three-body potential, we calculate the adiabatic potentials and the triton bound state energies. We find that a discrete variable representation with the slow variable discretization method along the hyperradial degree of freedom results in energies consistent with the literature. However, using a Laguerre basis results in missing energy, even when extrapolated to an infinite number of basis functions and channels. We do not include the isospin T = 3/2 contribution in our analysis.

  20. Adiabatic cluster-state quantum computing

    SciTech Connect

    Bacon, Dave; Flammia, Steven T.

    2010-09-15

    Models of quantum computation (QC) are important because they change the physical requirements for achieving universal QC. For example, one-way QC requires the preparation of an entangled ''cluster'' state, followed by adaptive measurement on this state, a set of requirements which is different from the standard quantum-circuit model. Here we introduce a model based on one-way QC but without measurements (except for the final readout), instead using adiabatic deformation of a Hamiltonian whose initial ground state is the cluster state. Our results could help increase the feasibility of adiabatic schemes by using tools from one-way QC.

  1. Markovian quantum master equation beyond adiabatic regime.

    PubMed

    Yamaguchi, Makoto; Yuge, Tatsuro; Ogawa, Tetsuo

    2017-01-01

    By introducing a temporal change time scale τ_{A}(t) for the time-dependent system Hamiltonian, a general formulation of the Markovian quantum master equation is given to go well beyond the adiabatic regime. In appropriate situations, the framework is well justified even if τ_{A}(t) is faster than the decay time scale of the bath correlation function. An application to the dissipative Landau-Zener model demonstrates this general result. The findings are applicable to a wide range of fields, providing a basis for quantum control beyond the adiabatic regime.

  2. Markovian quantum master equation beyond adiabatic regime

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Makoto; Yuge, Tatsuro; Ogawa, Tetsuo

    2017-01-01

    By introducing a temporal change time scale τA(t ) for the time-dependent system Hamiltonian, a general formulation of the Markovian quantum master equation is given to go well beyond the adiabatic regime. In appropriate situations, the framework is well justified even if τA(t ) is faster than the decay time scale of the bath correlation function. An application to the dissipative Landau-Zener model demonstrates this general result. The findings are applicable to a wide range of fields, providing a basis for quantum control beyond the adiabatic regime.

  3. Threshold altitude resulting in decompression sickness

    NASA Technical Reports Server (NTRS)

    Kumar, K. V.; Waligora, James M.; Calkins, Dick S.

    1990-01-01

    A review of case reports, hypobaric chamber training data, and experimental evidence indicated that the threshold for incidence of altitude decompression sickness (DCS) was influenced by various factors such as prior denitrogenation, exercise or rest, and period of exposure, in addition to individual susceptibility. Fitting these data with appropriate statistical models makes it possible to examine the influence of various factors on the threshold for DCS. This approach was illustrated by logistic regression analysis on the incidence of DCS below 9144 m. Estimations using these regressions showed that, under a noprebreathe, 6-h exposure, simulated EVA profile, the threshold for symptoms occurred at approximately 3353 m; while under a noprebreathe, 2-h exposure profile with knee-bends exercise, the threshold occurred at 7925 m.

  4. Automatic decompression device for internal combustion engine

    SciTech Connect

    Tsumiyama, Y.

    1986-10-07

    A decompression device is described for an internal combustion engine comprising: a holder secured to a camshaft supporting cams for controlling suction and exhaust valves of the engine, the cams having a contour and the holder having secured thereto a first cylindrical pin and a stopper pin; engine speed-responsive means including a first centrifugal weight supported by the holder for pivotal movement about the first pin and a second centrifugal weight supported on the first centrifugal weight for pivotal movement about a second pin having an axis parallel to the camshaft; cam means including a cylindrical pillar disposed on the second weight radially inwardly of the second pin and extending axially of the camshaft toward the cams for engagement with a valve operating member associated with one of the cams; and tension spring means mounted between the first centrifugal weight and the second centrifugal for moving the weights between a first position and a second position.

  5. Transcranial Doppler ultrasound and the etiology of neurologic decompression sickness during altitude decompression

    NASA Technical Reports Server (NTRS)

    Norfleet, W. T.; Powell, M. R.; Kumar, K. Vasantha; Waligora, J.

    1993-01-01

    The presence of gas bubbles in the arterial circulation can occur from iatrogenic mishaps, cardiopulmonary bypass devices, or following decompression, e.g., in deep-sea or SCUBA diving or in astronauts during extravehicular activities (EVA). We have examined the pathophysiology of neurological decompression sickness in human subjects who developed a large number of small gas bubbles in the right side of the heart as a result of hypobaric exposures. In one case, gas bubbles were detected in the middle cerebral artery (MCA) and the subject developed neurological symptoms; a 'resting' patent foramen ovalae (PFO) was found upon saline contrast echocardiography. A PFO was also detected in another individual who developed Spencer Grade 4 precordial Doppler ultrasound bubbles, but no evidence was seen of arterialization of bubbles upon insonation of either the MCA or common carotid artery. The reason for this difference in the behavior of intracardiac bubbles in these two individuals is not known. To date, we have not found evidence of right-to-left shunting of bubbles through pulmonary vasculature. The volume of gas bubbles present following decompression is examined and compared with the number arising from saline contrast injection. The estimates are comparable.

  6. Decompression sickness ('the bends') in sea turtles.

    PubMed

    García-Párraga, D; Crespo-Picazo, J L; de Quirós, Y Bernaldo; Cervera, V; Martí-Bonmati, L; Díaz-Delgado, J; Arbelo, M; Moore, M J; Jepson, P D; Fernández, Antonio

    2014-10-16

    Decompression sickness (DCS), as clinically diagnosed by reversal of symptoms with recompression, has never been reported in aquatic breath-hold diving vertebrates despite the occurrence of tissue gas tensions sufficient for bubble formation and injury in terrestrial animals. Similarly to diving mammals, sea turtles manage gas exchange and decompression through anatomical, physiological, and behavioral adaptations. In the former group, DCS-like lesions have been observed on necropsies following behavioral disturbance such as high-powered acoustic sources (e.g. active sonar) and in bycaught animals. In sea turtles, in spite of abundant literature on diving physiology and bycatch interference, this is the first report of DCS-like symptoms and lesions. We diagnosed a clinico-pathological condition consistent with DCS in 29 gas-embolized loggerhead sea turtles Caretta caretta from a sample of 67. Fifty-nine were recovered alive and 8 had recently died following bycatch in trawls and gillnets of local fisheries from the east coast of Spain. Gas embolization and distribution in vital organs were evaluated through conventional radiography, computed tomography, and ultrasound. Additionally, positive response following repressurization was clinically observed in 2 live affected turtles. Gas embolism was also observed postmortem in carcasses and tissues as described in cetaceans and human divers. Compositional gas analysis of intravascular bubbles was consistent with DCS. Definitive diagnosis of DCS in sea turtles opens a new era for research in sea turtle diving physiology, conservation, and bycatch impact mitigation, as well as for comparative studies in other air-breathing marine vertebrates and human divers.

  7. Outcome of endoscopic decompression of retrocalcaneal bursitis

    PubMed Central

    Kondreddi, Vamsi; Gopal, R Krishna; Yalamanchili, Ranjith K

    2012-01-01

    Background: Posterior heel pain due to retrocalcaneal bursitis, is a disabling condition that responds well to the conventional methods of treatment. Patients who do not respond to conservative treatment may require surgical intervention. This study evaluates the outcome of endoscopic decompression of retrocalcaneal bursitis, with resection of posterosuperior eminence of the calcaneum. Materials and Methods: This present study included 25 heels from 23 consecutive patients with posterior heel pain, who did not respond to conservative treatment and underwent endoscopic decompression of the retrocalcaneal bursae and excision of bony spurs. The functional outcome was evaluated by comparing the pre and postoperative American Orthopedic Foot and Ankle Society (AOFAS) scores. The Maryland ankle and foot score was used postoperatively to assess the patient's satisfaction at the one-year followup. Results: The University of Maryland scores of 25 heels were categorized as the nonparametric categories, and it was observed that 16 patients had an excellent outcome, six good, three fair and there were no poor results. The AOFAS scores averaged 57.92 ± 6.224 points preoperatively and 89.08 ± 5.267 points postoperatively (P < 0.001), at an average followup of 16.4 months. The 12 heels having noninsertional tendinosis on ultrasound had low AOFAS scores compared to 13 heels having retrocalcaneal bursitis alone. At one year followup, correlation for preoperative ultrasound assessment of tendoachilles degeneration versus postoperative Maryland score (Spearman correlation) had shown a strong negative correlation. Conclusion: Endoscopic calcaneal resection is highly effective in patients with mild or no degeneration and yields cosmetically better results with fewer complications. Patients with degenerative changes in Achilles tendon had poorer outcomes in terms of subjective satisfaction. PMID:23325968

  8. Adiabatic Compression in a Fire Syringe.

    ERIC Educational Resources Information Center

    Hayn, Carl H.; Baird, Scott C.

    1985-01-01

    Suggests using better materials in fire syringes to obtain more effective results during demonstrations which show the elevation in temperature upon a very rapid (adiabatic) compression of air. Also describes an experiment (using ignition temperatures) which introduces students to the use of thermocouples for high temperature measurements. (DH)

  9. Apparatus to Measure Adiabatic and Isothermal Processes.

    ERIC Educational Resources Information Center

    Lamb, D. W.; White, G. M.

    1996-01-01

    Describes a simple manual apparatus designed to serve as an effective demonstration of the differences between isothermal and adiabatic processes for the general or elementary physics student. Enables students to verify Boyle's law for slow processes and identify the departure from this law for rapid processes and can also be used to give a clear…

  10. Adiabatic and Non-adiabatic quenches in a Spin-1 Bose Einstein Condensate

    NASA Astrophysics Data System (ADS)

    Boguslawski, Matthew; Hebbe Madhusudhana, Bharath; Anquez, Martin; Robbins, Bryce; Barrios, Maryrose; Hoang, Thai; Chapman, Michael

    2016-05-01

    A quantum phase transition (QPT) is observed in a wide range of phenomena. We have studied the dynamics of a spin-1 ferromagnetic Bose-Einstein condensate for both adiabatic and non-adiabatic quenches through a QPT. At the quantum critical point (QCP), finite size effects lead to a non-zero gap, which makes an adiabatic quench possible through the QPT. We experimentally demonstrate such a quench, which is forbidden at the mean field level. For faster quenches through the QCP, the vanishing energy gap causes the reaction timescale of the system to diverge, preventing the system from adiabatically following the ground state. We measure the temporal evolution of the spin populations for different quench speeds and determine the exponents characterizing the scaling of the onset of excitations, which are in good agreement with the predictions of Kibble-Zurek mechanism.

  11. Fixed-point adiabatic quantum search

    NASA Astrophysics Data System (ADS)

    Dalzell, Alexander M.; Yoder, Theodore J.; Chuang, Isaac L.

    2017-01-01

    Fixed-point quantum search algorithms succeed at finding one of M target items among N total items even when the run time of the algorithm is longer than necessary. While the famous Grover's algorithm can search quadratically faster than a classical computer, it lacks the fixed-point property—the fraction of target items must be known precisely to know when to terminate the algorithm. Recently, Yoder, Low, and Chuang [Phys. Rev. Lett. 113, 210501 (2014), 10.1103/PhysRevLett.113.210501] gave an optimal gate-model search algorithm with the fixed-point property. Previously, it had been discovered by Roland and Cerf [Phys. Rev. A 65, 042308 (2002), 10.1103/PhysRevA.65.042308] that an adiabatic quantum algorithm, operating by continuously varying a Hamiltonian, can reproduce the quadratic speedup of gate-model Grover search. We ask, can an adiabatic algorithm also reproduce the fixed-point property? We show that the answer depends on what interpolation schedule is used, so as in the gate model, there are both fixed-point and non-fixed-point versions of adiabatic search, only some of which attain the quadratic quantum speedup. Guided by geometric intuition on the Bloch sphere, we rigorously justify our claims with an explicit upper bound on the error in the adiabatic approximation. We also show that the fixed-point adiabatic search algorithm can be simulated in the gate model with neither loss of the quadratic Grover speedup nor of the fixed-point property. Finally, we discuss natural uses of fixed-point algorithms such as preparation of a relatively prime state and oblivious amplitude amplification.

  12. Adiabatic burst evaporation from bicontinuous nanoporous membranes.

    PubMed

    Ichilmann, Sachar; Rücker, Kerstin; Haase, Markus; Enke, Dirk; Steinhart, Martin; Xue, Longjian

    2015-05-28

    Evaporation of volatile liquids from nanoporous media with bicontinuous morphology and pore diameters of a few 10 nm is an ubiquitous process. For example, such drying processes occur during syntheses of nanoporous materials by sol-gel chemistry or by spinodal decomposition in the presence of solvents as well as during solution impregnation of nanoporous hosts with functional guests. It is commonly assumed that drying is endothermic and driven by non-equilibrium partial pressures of the evaporating species in the gas phase. We show that nearly half of the liquid evaporates in an adiabatic mode involving burst-like liquid-to-gas conversions. During single adiabatic burst evaporation events liquid volumes of up to 10(7) μm(3) are converted to gas. The adiabatic liquid-to-gas conversions occur if air invasion fronts get unstable because of the built-up of high capillary pressures. Adiabatic evaporation bursts propagate avalanche-like through the nanopore systems until the air invasion fronts have reached new stable configurations. Adiabatic cavitation bursts thus compete with Haines jumps involving air invasion front relaxation by local liquid flow without enhanced mass transport out of the nanoporous medium and prevail if the mean pore diameter is in the range of a few 10 nm. The results reported here may help optimize membrane preparation via solvent-based approaches, solution-loading of nanopore systems with guest materials as well as routine use of nanoporous membranes with bicontinuous morphology and may contribute to better understanding of adsorption/desorption processes in nanoporous media.

  13. Adiabatic circuits: converter for static CMOS signals

    NASA Astrophysics Data System (ADS)

    Fischer, J.; Amirante, E.; Bargagli-Stoffi, A.; Schmitt-Landsiedel, D.

    2003-05-01

    Ultra low power applications can take great advantages from adiabatic circuitry. In this technique a multiphase system is used which consists ideally of trapezoidal voltage signals. The input signals to be processed will often come from a function block realized in static CMOS. The static rectangular signals must be converted for the oscillating multiphase system of the adiabatic circuitry. This work shows how to convert the input signals to the proposed pulse form which is synchronized to the appropriate supply voltage. By means of adder structures designed for a 0.13µm technology in a 4-phase system there will be demonstrated, which additional circuits are necessary for the conversion. It must be taken into account whether the data arrive in parallel or serial form. Parallel data are all in one phase and therefore it is advantageous to use an adder structure with a proper input stage, e.g. a Carry Lookahead Adder (CLA). With a serial input stage it is possible to read and to process four signals during one cycle due to the adiabatic 4-phase system. Therefore input signals with a frequency four times higher than the adiabatic clock frequency can be used. This reduces the disadvantage of the slow clock period typical for adiabatic circuits. By means of an 8 bit Ripple Carry Adder (8 bit RCA) the serial reading will be introduced. If the word width is larger than 4 bits the word can be divided in 4 bit words which are processed in parallel. This is the most efficient way to minimize the number of input lines and pads. At the same time a high throughput is achieved.

  14. The dynamic instability of adiabatic blast waves

    NASA Technical Reports Server (NTRS)

    Ryu, Dongsu; Vishniac, Ethan T.

    1991-01-01

    Adiabatic blastwaves, which have a total energy injected from the center E varies as t(sup q) and propagate through a preshock medium with a density rho(sub E) varies as r(sup -omega) are described by a family of similarity solutions. Previous work has shown that adiabatic blastwaves with increasing or constant postshock entropy behind the shock front are susceptible to an oscillatory instability, caused by the difference between the nature of the forces on the two sides of the dense shell behind the shock front. This instability sets in if the dense postshock layer is sufficiently thin. The stability of adiabatic blastwaves with a decreasing postshock entropy is considered. Such blastwaves, if they are decelerating, always have a region behind the shock front which is subject to convection. Some accelerating blastwaves also have such region, depending on the values of q, omega, and gamma where gamma is the adiabatic index. However, since the shock interface stabilizes dynamically induced perturbations, blastwaves become convectively unstable only if the convective zone is localized around the origin or a contact discontinuity far from the shock front. On the other hand, the contact discontinuity of accelerating blastwaves is subject to a strong Rayleigh-Taylor instability. The frequency spectra of the nonradial, normal modes of adiabatic blastwaves have been calculated. The results have been applied to the shocks propagating through supernovae envelopes. It is shown that the metal/He and He/H interfaces are strongly unstable against the Rayleigh-Taylor instability. This instability will induce mixing in supernovae envelopes. In addition the implications of this work for the evolution of planetary nebulae is discussed.

  15. Continuous eclogite melting and variable refertilisation in upwelling heterogeneous mantle.

    PubMed

    Rosenthal, Anja; Yaxley, Gregory M; Green, David H; Hermann, Joerg; Kovács, István; Spandler, Carl

    2014-08-18

    Large-scale tectonic processes introduce a range of crustal lithologies into the Earth's mantle. These lithologies have been implicated as sources of compositional heterogeneity in mantle-derived magmas. The model being explored here assumes the presence of widely dispersed fragments of residual eclogite (derived from recycled oceanic crust), stretched and stirred by convection in the mantle. Here we show with an experimental study that these residual eclogites continuously melt during upwelling of such heterogeneous mantle and we characterize the melting reactions and compositional changes in the residue minerals. The chemical exchange between these partial melts and more refractory peridotite leads to a variably metasomatised mantle. Re-melting of these metasomatised peridotite lithologies at given pressures and temperatures results in diverse melt compositions, which may contribute to the observed heterogeneity of oceanic basalt suites. We also show that heterogeneous upwelling mantle is subject to diverse local freezing, hybridization and carbonate-carbon-silicate redox reactions along a mantle adiabat.

  16. Continuous eclogite melting and variable refertilisation in upwelling heterogeneous mantle

    PubMed Central

    Rosenthal, Anja; Yaxley, Gregory M.; Green, David H.; Hermann, Joerg; Kovács, István; Spandler, Carl

    2014-01-01

    Large-scale tectonic processes introduce a range of crustal lithologies into the Earth's mantle. These lithologies have been implicated as sources of compositional heterogeneity in mantle-derived magmas. The model being explored here assumes the presence of widely dispersed fragments of residual eclogite (derived from recycled oceanic crust), stretched and stirred by convection in the mantle. Here we show with an experimental study that these residual eclogites continuously melt during upwelling of such heterogeneous mantle and we characterize the melting reactions and compositional changes in the residue minerals. The chemical exchange between these partial melts and more refractory peridotite leads to a variably metasomatised mantle. Re-melting of these metasomatised peridotite lithologies at given pressures and temperatures results in diverse melt compositions, which may contribute to the observed heterogeneity of oceanic basalt suites. We also show that heterogeneous upwelling mantle is subject to diverse local freezing, hybridization and carbonate-carbon-silicate redox reactions along a mantle adiabat. PMID:25130275

  17. Circumferential decompression of the foramen magnum for the treatment of syringomyelia associated with basilar invagination.

    PubMed

    Collignon, Frederic P; Cohen-Gadol, Aaron A; Krauss, William E

    2004-07-01

    Posterior fossa decompression utilizing suboccipital craniectomy and duraplasty remains the standard surgical treatment for Chiari-associated syringomyelia. In the presence of basilar invagination, anterior decompression, typically transoral odontoidectomy, or posterior decompression may be performed. We report two cases in which anterior and posterior (circumferential) decompression of the foramen magnum was used to treat cervical syringomyelia successfully. These cases demonstrate that circumferential decompression of the foramen magnum may be necessary in some cases of cervical syringomyelia associated with basilar invagination and Chiari malformation.

  18. The probability and severity of decompression sickness

    PubMed Central

    Hada, Ethan A.; Vann, Richard D.; Denoble, Petar J.

    2017-01-01

    Decompression sickness (DCS), which is caused by inert gas bubbles in tissues, is an injury of concern for scuba divers, compressed air workers, astronauts, and aviators. Case reports for 3322 air and N2-O2 dives, resulting in 190 DCS events, were retrospectively analyzed and the outcomes were scored as (1) serious neurological, (2) cardiopulmonary, (3) mild neurological, (4) pain, (5) lymphatic or skin, and (6) constitutional or nonspecific manifestations. Following standard U.S. Navy medical definitions, the data were grouped into mild—Type I (manifestations 4–6)–and serious–Type II (manifestations 1–3). Additionally, we considered an alternative grouping of mild–Type A (manifestations 3–6)–and serious–Type B (manifestations 1 and 2). The current U.S. Navy guidance allows for a 2% probability of mild DCS and a 0.1% probability of serious DCS. We developed a hierarchical trinomial (3-state) probabilistic DCS model that simultaneously predicts the probability of mild and serious DCS given a dive exposure. Both the Type I/II and Type A/B discriminations of mild and serious DCS resulted in a highly significant (p << 0.01) improvement in trinomial model fit over the binomial (2-state) model. With the Type I/II definition, we found that the predicted probability of ‘mild’ DCS resulted in a longer allowable bottom time for the same 2% limit. However, for the 0.1% serious DCS limit, we found a vastly decreased allowable bottom dive time for all dive depths. If the Type A/B scoring was assigned to outcome severity, the no decompression limits (NDL) for air dives were still controlled by the acceptable serious DCS risk limit rather than the acceptable mild DCS risk limit. However, in this case, longer NDL limits were allowed than with the Type I/II scoring. The trinomial model mild and serious probabilities agree reasonably well with the current air NDL only with the Type A/B scoring and when 0.2% risk of serious DCS is allowed. PMID:28296928

  19. The probability and severity of decompression sickness.

    PubMed

    Howle, Laurens E; Weber, Paul W; Hada, Ethan A; Vann, Richard D; Denoble, Petar J

    2017-01-01

    Decompression sickness (DCS), which is caused by inert gas bubbles in tissues, is an injury of concern for scuba divers, compressed air workers, astronauts, and aviators. Case reports for 3322 air and N2-O2 dives, resulting in 190 DCS events, were retrospectively analyzed and the outcomes were scored as (1) serious neurological, (2) cardiopulmonary, (3) mild neurological, (4) pain, (5) lymphatic or skin, and (6) constitutional or nonspecific manifestations. Following standard U.S. Navy medical definitions, the data were grouped into mild-Type I (manifestations 4-6)-and serious-Type II (manifestations 1-3). Additionally, we considered an alternative grouping of mild-Type A (manifestations 3-6)-and serious-Type B (manifestations 1 and 2). The current U.S. Navy guidance allows for a 2% probability of mild DCS and a 0.1% probability of serious DCS. We developed a hierarchical trinomial (3-state) probabilistic DCS model that simultaneously predicts the probability of mild and serious DCS given a dive exposure. Both the Type I/II and Type A/B discriminations of mild and serious DCS resulted in a highly significant (p < 0.01) improvement in trinomial model fit over the binomial (2-state) model. With the Type I/II definition, we found that the predicted probability of 'mild' DCS resulted in a longer allowable bottom time for the same 2% limit. However, for the 0.1% serious DCS limit, we found a vastly decreased allowable bottom dive time for all dive depths. If the Type A/B scoring was assigned to outcome severity, the no decompression limits (NDL) for air dives were still controlled by the acceptable serious DCS risk limit rather than the acceptable mild DCS risk limit. However, in this case, longer NDL limits were allowed than with the Type I/II scoring. The trinomial model mild and serious probabilities agree reasonably well with the current air NDL only with the Type A/B scoring and when 0.2% risk of serious DCS is allowed.

  20. Paradoxical Herniation following Decompressive Craniectomy in the Subacute Setting

    PubMed Central

    Espinosa, Jose

    2016-01-01

    Decompressive craniectomy is reserved for extreme cases of intracranial hypertension. An uncommon complication known as paradoxical herniation has been documented within weeks to months following surgery. Here we present a unique case within days of surgery. Since standard medical treatment for intracranial hypertension will exacerbate paradoxical herniation, any abrupt neurological changes following decompressive craniectomy should be carefully investigated. Immediate treatment for paradoxical herniation is placement of the patient in the supine position with adequate hydration. Cranioplasty is the ultimate treatment option. PMID:27446619

  1. Cases from the aerospace medicine residents' teaching file. Decompression sickness.

    PubMed

    Taylor, G N

    2000-12-01

    Decompression sickness is an uncommon but serious risk associated with flying and SCUBA diving with potential for significant morbidity and mortality. It can occur in both novice and experienced individuals. This case illustrates an atypical presentation of decompression sickness in an experienced amateur SCUBA diver. Clinical suspicion must be high, since the presenting symptoms can be nonspecific as in this case. Early recognition and treatment are important for maximum recovery.

  2. Investigation of Hematologic and Pathologic Response to Decompression.

    DTIC Science & Technology

    1978-05-10

    advanced case of osteonecrosjs did not manifest itself radiographically. In addition to -extensive necrosis of the cortical bone with peniosteal new...weeks of the ini tial decompression (6 , 7) . His tologic study of these cases of osteonecrosis , as well as evid ence presented by other investi gators...thrombotic therapy remains to be determined. I 45. I. . References 1. Rivera , T.C. Decompression sickness among div e rs: An analysis of 935 cases . M

  3. Patterns and Variations in Microvascular Decompression for Trigeminal Neuralgia

    PubMed Central

    TODA, Hiroki; GOTO, Masanori; IWASAKI, Koichi

    2015-01-01

    Microvascular decompression (MVD) is a highly effective surgical treatment for trigeminal neuralgia (TN). Although there is little prospective clinical evidence, accumulated observational studies have demonstrated the benefits of MVD for refractory TN. In the current surgical practice of MVD for TN, there have been recognized patterns and variations in surgical anatomy and various decompression techniques. Here we provide a stepwise description of surgical procedures and relevant anatomical characteristics, as well as procedural options. PMID:25925756

  4. Neurovascular Bundle Decompression without Excessive Dissection for Tarsal Tunnel Syndrome

    PubMed Central

    KIM, Kyongsong; ISU, Toyohiko; MORIMOTO, Daijiro; SASAMORI, Toru; SUGAWARA, Atsushi; CHIBA, Yasuhiro; ISOBE, Masahiro; KOBAYASHI, Shiro; MORITA, Akio

    2014-01-01

    Tarsal tunnel syndrome (TTS) is an entrapment neuropathy of the posterior tibial nerve and its branches in the tarsal tunnel. We present our less invasive surgical treatment of TTS in 69 patients (116 feet) and their clinical outcomes. The mean follow-up period was 64.6 months. With the patient under local anesthesia we use a microscope to perform sharp dissection of the flexor retinaculum and remove the connective tissues surrounding the posterior tibial nerve and vessels. To prevent postoperative adhesion and delayed neuropathy, decompression is performed to achieve symptom improvement without excessive dissection. Decompression is considered complete when the patient reports intraoperative symptom abatement and arterial pulsation is sufficient. The sensation of numbness and/or pain and of foreign substance adhesion was reduced in 92% and 95% of our patients, respectively. In self-assessments, 47 patients (68%) reported the treatment outcome as satisfactory, 15 (22%) as acceptable, and 7 (10%) were dissatisfied. Of 116 feet, 4 (3%) required re-operation, initial decompression was insufficient in 2 feet and further decompression was performed; in the other 2 feet improvement was achieved by decompression of the distal tarsal tunnel. Our surgical method involves neurovascular bundle decompression to obtain sufficient arterial pulsation. As we use local anesthesia, we can confirm symptom improvement intraoperatively, thereby avoiding unnecessary excessive dissection. Our method is simple, safe, and without detailed nerve dissection and it prevents postoperative adhesion. PMID:25367582

  5. Neurovascular bundle decompression without excessive dissection for tarsal tunnel syndrome.

    PubMed

    Kim, Kyongsong; Isu, Toyohiko; Morimoto, Daijiro; Sasamori, Toru; Sugawara, Atsushi; Chiba, Yasuhiro; Isobe, Masahiro; Kobayashi, Shiro; Morita, Akio

    2014-01-01

    Tarsal tunnel syndrome (TTS) is an entrapment neuropathy of the posterior tibial nerve and its branches in the tarsal tunnel. We present our less invasive surgical treatment of TTS in 69 patients (116 feet) and their clinical outcomes. The mean follow-up period was 64.6 months. With the patient under local anesthesia we use a microscope to perform sharp dissection of the flexor retinaculum and remove the connective tissues surrounding the posterior tibial nerve and vessels. To prevent postoperative adhesion and delayed neuropathy, decompression is performed to achieve symptom improvement without excessive dissection. Decompression is considered complete when the patient reports intraoperative symptom abatement and arterial pulsation is sufficient. The sensation of numbness and/or pain and of foreign substance adhesion was reduced in 92% and 95% of our patients, respectively. In self-assessments, 47 patients (68%) reported the treatment outcome as satisfactory, 15 (22%) as acceptable, and 7 (10%) were dissatisfied. Of 116 feet, 4 (3%) required re-operation, initial decompression was insufficient in 2 feet and further decompression was performed; in the other 2 feet improvement was achieved by decompression of the distal tarsal tunnel. Our surgical method involves neurovascular bundle decompression to obtain sufficient arterial pulsation. As we use local anesthesia, we can confirm symptom improvement intraoperatively, thereby avoiding unnecessary excessive dissection. Our method is simple, safe, and without detailed nerve dissection and it prevents postoperative adhesion.

  6. Quantum-Classical Correspondence of Shortcuts to Adiabaticity

    NASA Astrophysics Data System (ADS)

    Okuyama, Manaka; Takahashi, Kazutaka

    2017-04-01

    We formulate the theory of shortcuts to adiabaticity in classical mechanics. For a reference Hamiltonian, the counterdiabatic term is constructed from the dispersionless Korteweg-de Vries (KdV) hierarchy. Then the adiabatic theorem holds exactly for an arbitrary choice of time-dependent parameters. We use the Hamilton-Jacobi theory to define the generalized action. The action is independent of the history of the parameters and is directly related to the adiabatic invariant. The dispersionless KdV hierarchy is obtained from the classical limit of the KdV hierarchy for the quantum shortcuts to adiabaticity. This correspondence suggests some relation between the quantum and classical adiabatic theorems.

  7. Experimental respiratory decompression sickness in sheep.

    PubMed

    Atkins, C E; Lehner, C E; Beck, K A; Dubielzig, R R; Nordheim, E V; Lanphier, E H

    1988-09-01

    Respiratory decompression sickness (RDCS, "the chokes") is a potentially lethal consequence of ambient pressure reduction. Lack of a clearly suitable animal model has impeded understanding of this condition. RDCS, unaccompanied by central nervous system signs, occurred in 17 of 18 unanesthetized sheep exposed to compressed air at 230 kPa (2.27 ATA) for 22 h, returned to normal pressure for approximately 40 min, and taken to simulated altitude (0.75 ATA, 570 Torr). Respiratory signs, including tachypnea, sporadic apnea, and labored breathing, were accompanied by precordial Doppler ultrasound evidence of marked venous bubble loading. Pulmonary arterial pressures exceeded 30 Torr in five catheterized sheep that died or became moribund. Hypoxemia (arterial Po2 less than 40 Torr), neutropenia, and thrombocytopenia were observed. Peribronchovascular edema was the most prominent necropsy finding. Chest radiography indicated interstitial edema in most affected sheep. High body weight and catheterization predisposed the sheep to severe RDCS. It appears that this protocol reliably provides a useful animal model for studies of RDCS and obstructive pulmonary hypertension, that the precipitating event is massive pulmonary embolization by bubbles, and that venous bubbles, detected by Doppler ultrasound, can signal impending RDCS.

  8. Use of ultrasound in altitude decompression modeling

    NASA Technical Reports Server (NTRS)

    Olson, Robert M.; Pilmanis, Andrew A.

    1993-01-01

    A model that predicts the probability of developing decompression sickness (DCS) with various denitrogenation schedules is being developed by the Armstrong Laboratory, using human data from previous exposures. It was noted that refinements are needed to improve the accuracy and scope of the model. A commercially developed ultrasonic echo imaging system is being used in this model development. Using this technique, bubbles images from a subject at altitude can be seen in the gall bladder, hepatic veins, vena cava, and chambers of the heart. As judged by their motion and appearance in the vena cava, venous bubbles near the heart range in size from 30 to 300 M. The larger bubbles skim along the top, whereas the smaller ones appear as faint images near the bottom of the vessel. Images from growing bubbles in a model altitude chamber indicate that they grow rapidly, going from 20 to 100 M in 3 sec near 30,000 ft altitude. Information such as this is valuable in verifying those aspects of the DCS model dealing with bubble size, their growth rate, and their site of origin.

  9. A systematic review of factitious decompression sickness.

    PubMed

    Kenedi, Christopher; Sames, Christopher; Paice, Rhonda

    2013-01-01

    We present a case of factitious decompression sickness (DCS) involving a patient emergently treated at a hyperbaric medicine facility in New Zealand. Patients with factitious disorder feign illnesses such as DCS in order to receive care and attention despite the lack of an underlying illness. Other studies have suggested that 0.6% to as many as 9.3% of hospital admissions are factitious in nature. Therefore we believe that factitious DCS is occurring more often than hyperbaric clinicians suspect. DCS can be life-threatening, and hyperbaric medicine clinicians will almost always "err on the side of caution" when patients are referred with symptoms of DCS. Because DCS can be diagnosed based on subjective symptoms and self-reported history, there are opportunities for factitious patients to receive hyperbaric therapy. The costs associated with factitious DCS include transport, staff resources and preventing patients with treatable conditions from accessing the hyperbaric chamber. We performed a systematic review of the literature and found eight additional reported cases of confirmed or suspected factitious DCS. We report our findings and recommendations for hyperbaric medicine specialists regarding the recognition and management of factitious DCS.

  10. Adiabatic Quantum Simulation of Quantum Chemistry

    NASA Astrophysics Data System (ADS)

    Babbush, Ryan; Love, Peter J.; Aspuru-Guzik, Alán

    2014-10-01

    We show how to apply the quantum adiabatic algorithm directly to the quantum computation of molecular properties. We describe a procedure to map electronic structure Hamiltonians to 2-body qubit Hamiltonians with a small set of physically realizable couplings. By combining the Bravyi-Kitaev construction to map fermions to qubits with perturbative gadgets to reduce the Hamiltonian to 2-body, we obtain precision requirements on the coupling strengths and a number of ancilla qubits that scale polynomially in the problem size. Hence our mapping is efficient. The required set of controllable interactions includes only two types of interaction beyond the Ising interactions required to apply the quantum adiabatic algorithm to combinatorial optimization problems. Our mapping may also be of interest to chemists directly as it defines a dictionary from electronic structure to spin Hamiltonians with physical interactions.

  11. Ramsey numbers and adiabatic quantum computing.

    PubMed

    Gaitan, Frank; Clark, Lane

    2012-01-06

    The graph-theoretic Ramsey numbers are notoriously difficult to calculate. In fact, for the two-color Ramsey numbers R(m,n) with m, n≥3, only nine are currently known. We present a quantum algorithm for the computation of the Ramsey numbers R(m,n). We show how the computation of R(m,n) can be mapped to a combinatorial optimization problem whose solution can be found using adiabatic quantum evolution. We numerically simulate this adiabatic quantum algorithm and show that it correctly determines the Ramsey numbers R(3,3) and R(2,s) for 5≤s≤7. We then discuss the algorithm's experimental implementation, and close by showing that Ramsey number computation belongs to the quantum complexity class quantum Merlin Arthur.

  12. Comment on ``Adiabatic theory for the bipolaron''

    NASA Astrophysics Data System (ADS)

    Smondyrev, M. A.; Devreese, J. T.

    1996-05-01

    Comments are given on the application of the Bogoliubov-Tyablikov approach to the bipolaron problem in a recent paper by Lakhno [Phys. Rev. B 51, 3512 (1995)]. This author believes that his model (1) is the translation-invariant adiabatic theory of bipolarons and (2) gives asymptotically exact solutions in the adiabatic limit while the other approaches are considered as either phenomenological or variational in nature. Numerical results by Lakhno are in contradiction with all other papers published on the subject because his model leads to much lower energies. Thus, the author concludes that bipolarons ``are more stable than was considered before.'' We prove that both the analytical and the numerical results presented by Lakhno are wrong.

  13. Shortcuts to adiabaticity from linear response theory

    SciTech Connect

    Acconcia, Thiago V.; Bonança, Marcus V. S.; Deffner, Sebastian

    2015-10-23

    A shortcut to adiabaticity is a finite-time process that produces the same final state as would result from infinitely slow driving. We show that such shortcuts can be found for weak perturbations from linear response theory. Moreover, with the help of phenomenological response functions, a simple expression for the excess work is found—quantifying the nonequilibrium excitations. For two specific examples, i.e., the quantum parametric oscillator and the spin 1/2 in a time-dependent magnetic field, we show that finite-time zeros of the excess work indicate the existence of shortcuts. We finally propose a degenerate family of protocols, which facilitates shortcuts to adiabaticity for specific and very short driving times.

  14. Shortcuts to adiabaticity from linear response theory

    DOE PAGES

    Acconcia, Thiago V.; Bonança, Marcus V. S.; Deffner, Sebastian

    2015-10-23

    A shortcut to adiabaticity is a finite-time process that produces the same final state as would result from infinitely slow driving. We show that such shortcuts can be found for weak perturbations from linear response theory. Moreover, with the help of phenomenological response functions, a simple expression for the excess work is found—quantifying the nonequilibrium excitations. For two specific examples, i.e., the quantum parametric oscillator and the spin 1/2 in a time-dependent magnetic field, we show that finite-time zeros of the excess work indicate the existence of shortcuts. We finally propose a degenerate family of protocols, which facilitates shortcuts tomore » adiabaticity for specific and very short driving times.« less

  15. Adiabatic state preparation study of methylene

    SciTech Connect

    Veis, Libor Pittner, Jiří

    2014-06-07

    Quantum computers attract much attention as they promise to outperform their classical counterparts in solving certain type of problems. One of them with practical applications in quantum chemistry is simulation of complex quantum systems. An essential ingredient of efficient quantum simulation algorithms are initial guesses of the exact wave functions with high enough fidelity. As was proposed in Aspuru-Guzik et al. [Science 309, 1704 (2005)], the exact ground states can in principle be prepared by the adiabatic state preparation method. Here, we apply this approach to preparation of the lowest lying multireference singlet electronic state of methylene and numerically investigate preparation of this state at different molecular geometries. We then propose modifications that lead to speeding up the preparation process. Finally, we decompose the minimal adiabatic state preparation employing the direct mapping in terms of two-qubit interactions.

  16. Fast forward to the classical adiabatic invariant

    NASA Astrophysics Data System (ADS)

    Jarzynski, Christopher; Deffner, Sebastian; Patra, Ayoti; Subaşı, Yiǧit

    2017-03-01

    We show how the classical action, an adiabatic invariant, can be preserved under nonadiabatic conditions. Specifically, for a time-dependent Hamiltonian H =p2/2 m +U (q ,t ) in one degree of freedom, and for an arbitrary choice of action I0, we construct a so-called fast-forward potential energy function VFF(q ,t ) that, when added to H , guides all trajectories with initial action I0 to end with the same value of action. We use this result to construct a local dynamical invariant J (q ,p ,t ) whose value remains constant along these trajectories. We illustrate our results with numerical simulations. Finally, we sketch how our classical results may be used to design approximate quantum shortcuts to adiabaticity.

  17. Adiabatic invariance with first integrals of motion.

    PubMed

    Adib, Artur B

    2002-10-01

    The construction of a microthermodynamic formalism for isolated systems based on the concept of adiabatic invariance is an old but seldom appreciated effort in the literature, dating back at least to P. Hertz [Ann. Phys. (Leipzig) 33, 225 (1910)]. An apparently independent extension of such formalism for systems bearing additional first integrals of motion was recently proposed by Hans H. Rugh [Phys. Rev. E 64, 055101 (2001)], establishing the concept of adiabatic invariance even in such singular cases. After some remarks in connection with the formalism pioneered by Hertz, it will be suggested that such an extension can incidentally explain the success of a dynamical method for computing the entropy of classical interacting fluids, at least in some potential applications where the presence of additional first integrals cannot be ignored.

  18. Trapped Ion Quantum Computation by Adiabatic Passage

    SciTech Connect

    Feng Xuni; Wu Chunfeng; Lai, C. H.; Oh, C. H.

    2008-11-07

    We propose a new universal quantum computation scheme for trapped ions in thermal motion via the technique of adiabatic passage, which incorporates the advantages of both the adiabatic passage and the model of trapped ions in thermal motion. Our scheme is immune from the decoherence due to spontaneous emission from excited states as the system in our scheme evolves along a dark state. In our scheme the vibrational degrees of freedom are not required to be cooled to their ground states because they are only virtually excited. It is shown that the fidelity of the resultant gate operation is still high even when the magnitude of the effective Rabi frequency moderately deviates from the desired value.

  19. Adiabatic quantum simulation of quantum chemistry.

    PubMed

    Babbush, Ryan; Love, Peter J; Aspuru-Guzik, Alán

    2014-10-13

    We show how to apply the quantum adiabatic algorithm directly to the quantum computation of molecular properties. We describe a procedure to map electronic structure Hamiltonians to 2-body qubit Hamiltonians with a small set of physically realizable couplings. By combining the Bravyi-Kitaev construction to map fermions to qubits with perturbative gadgets to reduce the Hamiltonian to 2-body, we obtain precision requirements on the coupling strengths and a number of ancilla qubits that scale polynomially in the problem size. Hence our mapping is efficient. The required set of controllable interactions includes only two types of interaction beyond the Ising interactions required to apply the quantum adiabatic algorithm to combinatorial optimization problems. Our mapping may also be of interest to chemists directly as it defines a dictionary from electronic structure to spin Hamiltonians with physical interactions.

  20. Multiphoton adiabatic passage for atom optics applications

    SciTech Connect

    Demeter, Gabor; Djotyan, Gagik P.

    2009-04-15

    We study the force exerted on two-level atoms by short, counterpropagating laser pulses. When the counterpropagating pulses overlap each other partially, multiphoton adiabatic processes are possible in several configurations, which amplify the force exerted on the atoms. We investigate the practical usefulness of such multiphoton adiabatic transitions for the manipulation of the atoms' mechanical state. In particular, we compare the efficiency of a pair of constant frequency, oppositely detuned laser pulses and that of a pair of frequency-chirped pulses. We also consider the case of prolonged exposure to a sequence of laser pulses for a duration that is comparable to or much larger than the spontaneous lifetime of the atoms. We use numerical methods to calculate the reduction of the force and the heating of the atomic ensemble when spontaneous emission cannot be neglected during the interaction. In addition, we derive simple approximate formulas for the force and the heating, and compare them to the numerical results.

  1. Adiabatic quantum optimization for associative memory recall

    DOE PAGES

    Seddiqi, Hadayat; Humble, Travis S.

    2014-12-22

    Hopfield networks are a variant of associative memory that recall patterns stored in the couplings of an Ising model. Stored memories are conventionally accessed as fixed points in the network dynamics that correspond to energetic minima of the spin state. We show that memories stored in a Hopfield network may also be recalled by energy minimization using adiabatic quantum optimization (AQO). Numerical simulations of the underlying quantum dynamics allow us to quantify AQO recall accuracy with respect to the number of stored memories and noise in the input key. We investigate AQO performance with respect to how memories are storedmore » in the Ising model according to different learning rules. Our results demonstrate that AQO recall accuracy varies strongly with learning rule, a behavior that is attributed to differences in energy landscapes. Consequently, learning rules offer a family of methods for programming adiabatic quantum optimization that we expect to be useful for characterizing AQO performance.« less

  2. Adiabatic quantum optimization for associative memory recall

    SciTech Connect

    Seddiqi, Hadayat; Humble, Travis S.

    2014-12-22

    Hopfield networks are a variant of associative memory that recall patterns stored in the couplings of an Ising model. Stored memories are conventionally accessed as fixed points in the network dynamics that correspond to energetic minima of the spin state. We show that memories stored in a Hopfield network may also be recalled by energy minimization using adiabatic quantum optimization (AQO). Numerical simulations of the underlying quantum dynamics allow us to quantify AQO recall accuracy with respect to the number of stored memories and noise in the input key. We investigate AQO performance with respect to how memories are stored in the Ising model according to different learning rules. Our results demonstrate that AQO recall accuracy varies strongly with learning rule, a behavior that is attributed to differences in energy landscapes. Consequently, learning rules offer a family of methods for programming adiabatic quantum optimization that we expect to be useful for characterizing AQO performance.

  3. Adiabatic Quantum Simulation of Quantum Chemistry

    PubMed Central

    Babbush, Ryan; Love, Peter J.; Aspuru-Guzik, Alán

    2014-01-01

    We show how to apply the quantum adiabatic algorithm directly to the quantum computation of molecular properties. We describe a procedure to map electronic structure Hamiltonians to 2-body qubit Hamiltonians with a small set of physically realizable couplings. By combining the Bravyi-Kitaev construction to map fermions to qubits with perturbative gadgets to reduce the Hamiltonian to 2-body, we obtain precision requirements on the coupling strengths and a number of ancilla qubits that scale polynomially in the problem size. Hence our mapping is efficient. The required set of controllable interactions includes only two types of interaction beyond the Ising interactions required to apply the quantum adiabatic algorithm to combinatorial optimization problems. Our mapping may also be of interest to chemists directly as it defines a dictionary from electronic structure to spin Hamiltonians with physical interactions. PMID:25308187

  4. Computer Code For Turbocompounded Adiabatic Diesel Engine

    NASA Technical Reports Server (NTRS)

    Assanis, D. N.; Heywood, J. B.

    1988-01-01

    Computer simulation developed to study advantages of increased exhaust enthalpy in adiabatic turbocompounded diesel engine. Subsytems of conceptual engine include compressor, reciprocator, turbocharger turbine, compounded turbine, ducting, and heat exchangers. Focus of simulation of total system is to define transfers of mass and energy, including release and transfer of heat and transfer of work in each subsystem, and relationship among subsystems. Written in FORTRAN IV.

  5. Adiabatic charging of nickel-hydrogen batteries

    NASA Technical Reports Server (NTRS)

    Lurie, Chuck; Foroozan, S.; Brewer, Jeff; Jackson, Lorna

    1995-01-01

    Battery management during prelaunch activities has always required special attention and careful planning. The transition from nickel-cadium to nickel-hydrogen batteries, with their high self discharge rate and lower charge efficiency, as well as longer prelaunch scenarios, has made this aspect of spacecraft battery management even more challenging. The AXAF-I Program requires high battery state of charge at launch. The use of active cooling, to ensure efficient charging, was considered and proved to be difficult and expensive. Alternative approaches were evaluated. Optimized charging, in the absence of cooling, appeared promising and was investigated. Initial testing was conducted to demonstrate the feasibility of the 'Adiabatic Charging' approach. Feasibility was demonstrated and additional testing performed to provide a quantitative, parametric data base. The assumption that the battery is in an adiabatic environment during prelaunch charging is a conservative approximation because the battery will transfer some heat to its surroundings by convective air cooling. The amount is small compared to the heat dissipated during battery overcharge. Because the battery has a large thermal mass, substantial overcharge can occur before the cells get too hot to charge efficiently. The testing presented here simulates a true adiabatic environment. Accordingly the data base may be slightly conservative. The adiabatic charge methodology used in this investigation begins with stabilizing the cell at a given starting temperature. The cell is then fully insulated on all sides. Battery temperature is carefully monitored and the charge terminated when the cell temperature reaches 85 F. Charging has been evaluated with starting temperatures from 55 to 75 F.

  6. Aspects of adiabatic population transfer and control

    NASA Astrophysics Data System (ADS)

    Demirplak, Mustafa

    This thesis explores two different questions. The first question we answer is how to restore a given population transfer scenario given that it works efficiently in the adiabatic limit but fails because of lack of intensity and/or short duration. We derive a very simple algorithm to do this and apply it to both toy and realistic models. Two results emerge from this study. While the mathematical existence of the programme is certain it might not always be physically desirable. The restoration of adiabaticity is phase sensitive. The second question that is answered in this thesis is not how to invent new control paradigms, but rather what would happen to them in the presence of stochastic perturbers. We first use a phenomenological model to study the effect of stochastic dephasing on population transfer by stimulated Raman adiabatic passage. The results of this Monte Carlo calculation are qualitatively explained with a perturbation theoretical result in the dressed state basis. The reliability of our phenomenological model is questioned through a more rigorous hybrid quantal-classical simulation of controlled population transfer in HCl in Ar.

  7. Adiabatic graph-state quantum computation

    NASA Astrophysics Data System (ADS)

    Antonio, B.; Markham, D.; Anders, J.

    2014-11-01

    Measurement-based quantum computation (MBQC) and holonomic quantum computation (HQC) are two very different computational methods. The computation in MBQC is driven by adaptive measurements executed in a particular order on a large entangled state. In contrast in HQC the system starts in the ground subspace of a Hamiltonian which is slowly changed such that a transformation occurs within the subspace. Following the approach of Bacon and Flammia, we show that any MBQC on a graph state with generalized flow (gflow) can be converted into an adiabatically driven holonomic computation, which we call adiabatic graph-state quantum computation (AGQC). We then investigate how properties of AGQC relate to the properties of MBQC, such as computational depth. We identify a trade-off that can be made between the number of adiabatic steps in AGQC and the norm of \\dot{H} as well as the degree of H, in analogy to the trade-off between the number of measurements and classical post-processing seen in MBQC. Finally the effects of performing AGQC with orderings that differ from standard MBQC are investigated.

  8. Random matrix model of adiabatic quantum computing

    SciTech Connect

    Mitchell, David R.; Adami, Christoph; Lue, Waynn; Williams, Colin P.

    2005-05-15

    We present an analysis of the quantum adiabatic algorithm for solving hard instances of 3-SAT (an NP-complete problem) in terms of random matrix theory (RMT). We determine the global regularity of the spectral fluctuations of the instantaneous Hamiltonians encountered during the interpolation between the starting Hamiltonians and the ones whose ground states encode the solutions to the computational problems of interest. At each interpolation point, we quantify the degree of regularity of the average spectral distribution via its Brody parameter, a measure that distinguishes regular (i.e., Poissonian) from chaotic (i.e., Wigner-type) distributions of normalized nearest-neighbor spacings. We find that for hard problem instances - i.e., those having a critical ratio of clauses to variables - the spectral fluctuations typically become irregular across a contiguous region of the interpolation parameter, while the spectrum is regular for easy instances. Within the hard region, RMT may be applied to obtain a mathematical model of the probability of avoided level crossings and concomitant failure rate of the adiabatic algorithm due to nonadiabatic Landau-Zener-type transitions. Our model predicts that if the interpolation is performed at a uniform rate, the average failure rate of the quantum adiabatic algorithm, when averaged over hard problem instances, scales exponentially with increasing problem size.

  9. Allometric scaling of decompression sickness risk in terrestrial mammals; cardiac output explains risk of decompression sickness

    NASA Astrophysics Data System (ADS)

    Fahlman, Andreas

    2017-02-01

    A probabilistic model was used to predict decompression sickness (DCS) outcome in pig (70 and 20 kg), hamster (100 g), rat (220 g) and mouse (20 g) following air saturation dives. The data set included 179 pig, 200 hamster, 360 rat, and 224 mouse exposures to saturation pressures ranging from 1.9–15.2 ATA and with varying decompression rates (0.9–156 ATA • min‑1). Single exponential kinetics described the tissue partial pressures (Ptiss) of N2: Ptiss =  ∫(Pamb – Ptiss) • τ‑1 dt, where Pamb is ambient N2 pressure and τ is a time constant. The probability of DCS [P(DCS)] was predicted from the risk function: P(DCS) = 1‑e‑r, where r = ∫(PtissN2 ‑ Thr ‑ Pamb) • Pamb–1 dt, and Thr is a threshold parameter. An equation that scaled τ with body mass included a constant (c) and an allometric scaling parameter (n), and the best model included n, Thr, and two c. The final model provided accurate predictions for 58 out of 61 dive profiles for pig, hamster, rat, and mouse. Thus, body mass helped improve the prediction of DCS risk in four mammalian species over a body mass range covering 3 orders of magnitude.

  10. Allometric scaling of decompression sickness risk in terrestrial mammals; cardiac output explains risk of decompression sickness

    PubMed Central

    Fahlman, Andreas

    2017-01-01

    A probabilistic model was used to predict decompression sickness (DCS) outcome in pig (70 and 20 kg), hamster (100 g), rat (220 g) and mouse (20 g) following air saturation dives. The data set included 179 pig, 200 hamster, 360 rat, and 224 mouse exposures to saturation pressures ranging from 1.9–15.2 ATA and with varying decompression rates (0.9–156 ATA • min−1). Single exponential kinetics described the tissue partial pressures (Ptiss) of N2: Ptiss =  ∫(Pamb – Ptiss) • τ−1 dt, where Pamb is ambient N2 pressure and τ is a time constant. The probability of DCS [P(DCS)] was predicted from the risk function: P(DCS) = 1−e−r, where r = ∫(PtissN2 − Thr − Pamb) • Pamb–1 dt, and Thr is a threshold parameter. An equation that scaled τ with body mass included a constant (c) and an allometric scaling parameter (n), and the best model included n, Thr, and two c. The final model provided accurate predictions for 58 out of 61 dive profiles for pig, hamster, rat, and mouse. Thus, body mass helped improve the prediction of DCS risk in four mammalian species over a body mass range covering 3 orders of magnitude. PMID:28150725

  11. Allometric scaling of decompression sickness risk in terrestrial mammals; cardiac output explains risk of decompression sickness.

    PubMed

    Fahlman, Andreas

    2017-02-02

    A probabilistic model was used to predict decompression sickness (DCS) outcome in pig (70 and 20 kg), hamster (100 g), rat (220 g) and mouse (20 g) following air saturation dives. The data set included 179 pig, 200 hamster, 360 rat, and 224 mouse exposures to saturation pressures ranging from 1.9-15.2 ATA and with varying decompression rates (0.9-156 ATA • min(-1)). Single exponential kinetics described the tissue partial pressures (Ptiss) of N2: Ptiss =  ∫(Pamb - Ptiss) • τ(-1) dt, where Pamb is ambient N2 pressure and τ is a time constant. The probability of DCS [P(DCS)] was predicted from the risk function: P(DCS) = 1-e(-r), where r = ∫(PtissN2 - Thr - Pamb) • Pamb(-1) dt, and Thr is a threshold parameter. An equation that scaled τ with body mass included a constant (c) and an allometric scaling parameter (n), and the best model included n, Thr, and two c. The final model provided accurate predictions for 58 out of 61 dive profiles for pig, hamster, rat, and mouse. Thus, body mass helped improve the prediction of DCS risk in four mammalian species over a body mass range covering 3 orders of magnitude.

  12. Delayed Recompression for Decompression Sickness: Retrospective Analysis

    PubMed Central

    Hadanny, Amir; Fishlev, Gregori; Bechor, Yair; Bergan, Jacob; Friedman, Mony; Maliar, Amit; Efrati, Shai

    2015-01-01

    Introduction Most cases of decompression sickness (DCS) occur soon after surfacing, with 98% within 24 hours. Recompression using hyperbaric chamber should be administrated as soon as feasible in order to decrease bubble size and avoid further tissue injury. Unfortunately, there may be a significant time delay from surfacing to recompression. The time beyond which hyperbaric treatment is non effective is unclear. The aims of the study were first to evaluate the effect of delayed hyperbaric treatment, initiated more than 48h after surfacing for DCS and second, to evaluate the different treatment protocols. Methods From January 2000 to February 2014, 76 divers had delayed hyperbaric treatment (≥48h) for DCS in the Sagol center for Hyperbaric medicine and Research, Assaf-Harofeh Medical Center, Israel. Data were collected from their medical records and compared to data of 128 patients treated earlier than 48h after surfacing at the same hyperbaric institute. Results There was no significant difference, as to any of the baseline characteristics, between the delayed and early treatment groups. With respect to treatment results, at the delayed treatment divers, complete recovery was achieved in 76% of the divers, partial recovery in 17.1% and no improvement in 6.6%. Similar results were achieved when treatment started early, where 78% of the divers had complete recovery, 15.6% partial recovery and 6.2% no recovery. Delayed hyperbaric treatment using US Navy Table 6 protocol trended toward a better clinical outcome yet not statistically significant (OR=2.786, CI95%[0.896-8.66], p=0.07) compared to standard hyperbaric oxygen therapy of 90 minutes at 2 ATA, irrespective of the symptoms severity at presentation. Conclusions Late recompression for DCS, 48 hours or more after surfacing, has clinical value and when applied can achieve complete recovery in 76% of the divers. It seems that the preferred hyperbaric treatment protocol should be based on US Navy Table 6. PMID

  13. Decompression sickness following breath-hold diving.

    PubMed

    Schipke, J D; Gams, E; Kallweit, Oliver

    2006-01-01

    Despite convincing evidence of a relationship between breath-hold diving and decompression sickness (DCS), the causal connection is only slowly being accepted. Only the more recent textbooks have acknowledged the risks of repetitive breath-hold diving. We compare four groups of breath-hold divers: (1) Japanese and Korean amas and other divers from the Pacific area, (2) instructors at naval training facilities, (3) spear fishers, and (4) free-dive athletes. While the number of amas is likely decreasing, and Scandinavian Navy training facilities recorded only a few accidents, the number of spear fishers suffering accidents is on the rise, in particular during championships or using scooters. Finally, national and international associations (e.g., International Association of Free Drives [IAFD] or Association Internationale pour Le Developpment De L'Apnee [AIDA]) promote free-diving championships including deep diving categories such as constant weight, variable weight, and no limit. A number of free-diving athletes, training for or participating in competitions, are increasingly accident prone as the world record is presently set at a depth of 171 m. This review presents data found after searching Medline and ISI Web of Science and using appropriate Internet search engines (e.g., Google). We report some 90 cases in which DCS occurred after repetitive breath-hold dives. Even today, the risk of suffering from DCS after repetitive breath-hold diving is often not acknowledged. We strongly suggest that breath-hold divers and their advisors and physicians be made aware of the possibility of DCS and of the appropriate therapeutic measures to be taken when DCS is suspected. Because the risk of suffering from DCS increases depending on depth, bottom time, rate of ascent, and duration of surface intervals, some approaches to assess the risks are presented. Regrettably, none of these approaches is widely accepted. We propose therefore the development of easily manageable

  14. Non-adiabatic effects in near-adiabatic mixed-field orientation and alignment

    NASA Astrophysics Data System (ADS)

    Maan, Anjali; Ahlawat, Dharamvir Singh; Prasad, Vinod

    2016-11-01

    We present a theoretical study of the impact of a pair of moderate electric fields tilted an angle with respect to one another on a molecule. As a prototype, we consider a molecule with large rotational constant (with corresponding small rotational period) and moderate dipole moment. Within rigid-rotor approximation, the time-dependent Schrodinger equation is solved using fourth-order Runge-Kutta method. We have analysed that lower rotational states are significantly influenced by variation in pulse durations, the tilt angle between the fields and also on the electric field strengths. We also suggest a control scheme of how the rotational dynamics, orientation and alignment of a molecule can be enhanced by a combination of near-adiabatic pulses in comparision to non-adiabatic or adiabatic pulses.

  15. Bond selective chemistry beyond the adiabatic approximation

    SciTech Connect

    Butler, L.J.

    1993-12-01

    One of the most important challenges in chemistry is to develop predictive ability for the branching between energetically allowed chemical reaction pathways. Such predictive capability, coupled with a fundamental understanding of the important molecular interactions, is essential to the development and utilization of new fuels and the design of efficient combustion processes. Existing transition state and exact quantum theories successfully predict the branching between available product channels for systems in which each reaction coordinate can be adequately described by different paths along a single adiabatic potential energy surface. In particular, unimolecular dissociation following thermal, infrared multiphoton, or overtone excitation in the ground state yields a branching between energetically allowed product channels which can be successfully predicted by the application of statistical theories, i.e. the weakest bond breaks. (The predictions are particularly good for competing reactions in which when there is no saddle point along the reaction coordinates, as in simple bond fission reactions.) The predicted lack of bond selectivity results from the assumption of rapid internal vibrational energy redistribution and the implicit use of a single adiabatic Born-Oppenheimer potential energy surface for the reaction. However, the adiabatic approximation is not valid for the reaction of a wide variety of energetic materials and organic fuels; coupling between the electronic states of the reacting species play a a key role in determining the selectivity of the chemical reactions induced. The work described below investigated the central role played by coupling between electronic states in polyatomic molecules in determining the selective branching between energetically allowed fragmentation pathways in two key systems.

  16. Quantized adiabatic transport in momentum space.

    PubMed

    Ho, Derek Y H; Gong, Jiangbin

    2012-07-06

    Though topological aspects of energy bands are known to play a key role in quantum transport in solid-state systems, the implications of Floquet band topology for transport in momentum space (i.e., acceleration) have not been explored so far. Using a ratchet accelerator model inspired by existing cold-atom experiments, here we characterize a class of extended Floquet bands of one-dimensional driven quantum systems by Chern numbers, reveal topological phase transitions therein, and theoretically predict the quantization of adiabatic transport in momentum space. Numerical results confirm our theory and indicate the feasibility of experimental studies.

  17. Adiabatic demagnetization refrigerator for space use

    NASA Technical Reports Server (NTRS)

    Serlemitsos, A. T.; Warner, B. A.; Castles, S.; Breon, S. R.; San Sebastian, M.; Hait, T.

    1990-01-01

    An Adiabatic Demagnetization Refrigerator (ADR) for space use is under development at NASA's Goddard Space Flight Center (GSFC). The breadboard ADR operated at 100 mK for 400 minutes. Some significant changes to that ADR, designed to eliminate shortcomings revealed during tests, are reported. To increase thermal contact, the ferric ammonium sulfate crystals were grown directly on gold-plated copper wires which serve as the thermal bus. The thermal link to the X-ray sensors was also markedly improved. To speed up the testing required to determine the best design parameters for the gas gap heat switch, the new heat switch has a modular design and is easy to disassemble.

  18. Shortcuts to adiabaticity for quantum annealing

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazutaka

    2017-01-01

    We study the Ising Hamiltonian with a transverse field term to simulate the quantum annealing. Using shortcuts to adiabaticity, we design the time dependence of the Hamiltonian. The dynamical invariant is obtained by the mean-field ansatz, and the Hamiltonian is designed by the inverse engineering. We show that the time dependence of physical quantities such as the magnetization is independent of the speed of the Hamiltonian variation in the infinite-range model. We also show that rotating transverse magnetic fields are useful to achieve the ideal time evolution.

  19. Phase avalanches in near-adiabatic evolutions

    SciTech Connect

    Vertesi, T.; Englman, R.

    2006-02-15

    In the course of slow, nearly adiabatic motion of a system, relative changes in the slowness can cause abrupt and high magnitude phase changes, ''phase avalanches,'' superimposed on the ordinary geometric phases. The generality of this effect is examined for arbitrary Hamiltonians and multicomponent (>2) wave packets and is found to be connected (through the Blaschke term in the theory of analytic signals) to amplitude zeros in the lower half of the complex time plane. Motion on a nonmaximal circle on the Poincare-sphere suppresses the effect. A spectroscopic transition experiment can independently verify the phase-avalanche magnitudes.

  20. Decoherence in a scalable adiabatic quantum computer

    SciTech Connect

    Ashhab, S.; Johansson, J. R.; Nori, Franco

    2006-11-15

    We consider the effects of decoherence on Landau-Zener crossings encountered in a large-scale adiabatic-quantum-computing setup. We analyze the dependence of the success probability--i.e., the probability for the system to end up in its new ground state--on the noise amplitude and correlation time. We determine the optimal sweep rate that is required to maximize the success probability. We then discuss the scaling of decoherence effects with increasing system size. We find that those effects can be important for large systems, even if they are small for each of the small building blocks.

  1. Cavity-state preparation using adiabatic transfer

    NASA Astrophysics Data System (ADS)

    Larson, Jonas; Andersson, Erika

    2005-05-01

    We show how to prepare a variety of cavity field states for multiple cavities. The state preparation technique used is related to the method of stimulated adiabatic Raman passage. The cavity modes are coupled by atoms, making it possible to transfer an arbitrary cavity field state from one cavity to another and also to prepare nontrivial cavity field states. In particular, we show how to prepare entangled states of two or more cavities, such as an Einstein-Podolsky-Rosen state and a W state, as well as various entangled superpositions of coherent states in different cavities, including Schrödinger cat states. The theoretical considerations are supported by numerical simulations.

  2. Generalized Ramsey numbers through adiabatic quantum optimization

    NASA Astrophysics Data System (ADS)

    Ranjbar, Mani; Macready, William G.; Clark, Lane; Gaitan, Frank

    2016-09-01

    Ramsey theory is an active research area in combinatorics whose central theme is the emergence of order in large disordered structures, with Ramsey numbers marking the threshold at which this order first appears. For generalized Ramsey numbers r( G, H), the emergent order is characterized by graphs G and H. In this paper we: (i) present a quantum algorithm for computing generalized Ramsey numbers by reformulating the computation as a combinatorial optimization problem which is solved using adiabatic quantum optimization; and (ii) determine the Ramsey numbers r({{T}}m,{{T}}n) for trees of order m,n = 6,7,8, most of which were previously unknown.

  3. The risks of scuba diving: a focus on Decompression Illness.

    PubMed

    Hall, Jennifer

    2014-11-01

    Decompression Illness includes both Decompression Sickness (DCS) and Pulmonary Overinflation Syndrome (POIS), subsets of diving-related injury related to scuba diving. DCS is a condition in which gas bubbles that form while diving do not have adequate time to be resorbed or "off-gassed," resulting in entrapment in specific regions of the body. POIS is due to an overly rapid ascent to the surface resulting in the rupture of alveoli and subsequent extravasation of air bubbles into tissue planes or even the cerebral circulation. Divers must always be cognizant of dive time and depth, and be trained in the management of decompression. A slow and controlled ascent, plus proper control of buoyancy can reduce the dangerous consequences of pulmonary barotrauma. The incidence of adverse effects can be diminished with safe practices, allowing for the full enjoyment of this adventurous aquatic sport.

  4. The Risks of Scuba Diving: A Focus on Decompression Illness

    PubMed Central

    2014-01-01

    Decompression Illness includes both Decompression Sickness (DCS) and Pulmonary Overinflation Syndrome (POIS), subsets of diving-related injury related to scuba diving. DCS is a condition in which gas bubbles that form while diving do not have adequate time to be resorbed or “off-gassed,” resulting in entrapment in specific regions of the body. POIS is due to an overly rapid ascent to the surface resulting in the rupture of alveoli and subsequent extravasation of air bubbles into tissue planes or even the cerebral circulation. Divers must always be cognizant of dive time and depth, and be trained in the management of decompression. A slow and controlled ascent, plus proper control of buoyancy can reduce the dangerous consequences of pulmonary barotrauma. The incidence of adverse effects can be diminished with safe practices, allowing for the full enjoyment of this adventurous aquatic sport. PMID:25478296

  5. Generating shortcuts to adiabaticity in quantum and classical dynamics

    NASA Astrophysics Data System (ADS)

    Jarzynski, Christopher

    2013-10-01

    Transitionless quantum driving achieves adiabatic evolution in a hurry, using a counterdiabatic Hamiltonian to stifle nonadiabatic transitions. Here this shortcut to adiabaticity is cast in terms of a generator of adiabatic transport. This yields a classical analog of transitionless driving, and provides a strategy for constructing quantal counterdiabatic Hamiltonians. As an application of this framework, exact classical and quantal counterdiabatic terms are obtained for a particle in a box and for even-power-law potentials in one degree of freedom.

  6. Numerical simulations of solar spicules: Adiabatic and non-adiabatic studies

    NASA Astrophysics Data System (ADS)

    Kuźma, B.; Murawski, K.; Zaqarashvili, T. V.; Konkol, P.; Mignone, A.

    2017-01-01

    Aims: We aim to study the formation and evolution of solar spicules using numerical simulations of a vertical velocity pulse that is launched from the upper chromosphere. Methods: With the use of the PLUTO code, we numerically solved adiabatic and non-adiabatic magnetohydrodynamic (MHD) equations in 2D cylindrical geometry. We followed the evolution of spicules triggered by pulses that are launched in a vertical velocity component from the upper chromosphere. Then we compared the results obtained with and without non-adiabatic terms in the MHD equations. Results: Our numerical results reveal that the velocity pulse is steepened into a shock that propagates upward into the corona. The chromospheric cold and dense plasma follows the shock and rises into the corona with the mean speed of 20-25 km s-1. The nonlinear wake behind the pulse in the stratified atmosphere leads to quasi-periodic rebound shocks, which lead to quasi-periodic rising of chromospheric plasma into the corona with a period close to the acoustic cut-off period of the chromosphere. We found that the effect of non-adiabatic terms on spicule evolution is minor; the general properties of spicules such as their heights and rising-time remain slightly affected by these terms. Conclusions: In the framework of the axisymmetric model we devised, we show that the solar spicules can be triggered by the vertical velocity pulses, and thermal conduction and radiative cooling terms do not exert any significant influence on the dynamics of these spicules.

  7. On the Role of Prior Probability in Adiabatic Quantum Algorithms

    NASA Astrophysics Data System (ADS)

    Sun, Jie; Lu, Songfeng; Yang, Liping

    2016-03-01

    In this paper, we study the role of prior probability on the efficiency of quantum local adiabatic search algorithm. The following aspects for prior probability are found here: firstly, only the probabilities of marked states affect the running time of the adiabatic evolution; secondly, the prior probability can be used for improving the efficiency of the adiabatic algorithm; thirdly, like the usual quantum adiabatic evolution, the running time for the case of multiple solution states where the number of marked elements are smaller enough than the size of the set assigned that contains them can be significantly bigger than that of the case where the assigned set only contains all the marked states.

  8. Adiabatic following for a three-state quantum system

    NASA Astrophysics Data System (ADS)

    Huang, Wei; Shore, Bruce W.; Rangelov, Andon; Kyoseva, Elica

    2017-01-01

    Adiabatic time-evolution - found in various forms of adiabatic following and adiabatic passage - is often advantageous for controlled manipulation of quantum systems due to its insensitivity to deviations in the pulse shapes and timings. In this paper we discuss controlled adiabatic evolution of a three-state quantum system, a natural advance to the widespread use of two-state systems in numerous contemporary applications. We discuss, and illustrate, not only possibilities for population transfer but also for creating, with prescribed relative phase, 50:50 superpositions of two Zeeman sublevels in a letter-vee coupling linkage.

  9. Adiabatic approximation via hodograph translation and zero-curvature equations

    NASA Astrophysics Data System (ADS)

    Karasev, M. V.

    2014-04-01

    For quantum as well classical slow-fast systems, we develop a general method which allows one to compute the adiabatic invariant (approximate integral of motion), its symmetries, the adiabatic guiding center coordinates and the effective scalar Hamiltonian in all orders of a small parameter. The scheme does not exploit eigenvectors or diagonalization, but is based on the ideas of isospectral deformation and zero-curvature equations, where the role of "time" is played by the adiabatic (quantization) parameter. The algorithm includes the construction of the zero-curvature adiabatic connection and its splitting generated by averaging up to an arbitrary order in the small parameter.

  10. Quantum Adiabatic Algorithms and Large Spin Tunnelling

    NASA Technical Reports Server (NTRS)

    Boulatov, A.; Smelyanskiy, V. N.

    2003-01-01

    We provide a theoretical study of the quantum adiabatic evolution algorithm with different evolution paths proposed in this paper. The algorithm is applied to a random binary optimization problem (a version of the 3-Satisfiability problem) where the n-bit cost function is symmetric with respect to the permutation of individual bits. The evolution paths are produced, using the generic control Hamiltonians H (r) that preserve the bit symmetry of the underlying optimization problem. In the case where the ground state of H(0) coincides with the totally-symmetric state of an n-qubit system the algorithm dynamics is completely described in terms of the motion of a spin-n/2. We show that different control Hamiltonians can be parameterized by a set of independent parameters that are expansion coefficients of H (r) in a certain universal set of operators. Only one of these operators can be responsible for avoiding the tunnelling in the spin-n/2 system during the quantum adiabatic algorithm. We show that it is possible to select a coefficient for this operator that guarantees a polynomial complexity of the algorithm for all problem instances. We show that a successful evolution path of the algorithm always corresponds to the trajectory of a classical spin-n/2 and provide a complete characterization of such paths.

  11. The genesis of adiabatic shear bands

    PubMed Central

    Landau, P.; Osovski, S.; Venkert, A.; Gärtnerová, V.; Rittel, D.

    2016-01-01

    Adiabatic shear banding (ASB) is a unique dynamic failure mechanism that results in an unpredicted catastrophic failure due to a concentrated shear deformation mode. It is universally considered as a material or structural instability and as such, ASB is hardly controllable or predictable to some extent. ASB is modeled on the premise of stability analyses. The leading paradigm is that a competition between strain (rate) hardening and thermal softening determines the onset of the failure. It was recently shown that microstructural softening transformations, such as dynamic recrystallization, are responsible for adiabatic shear failure. These are dictated by the stored energy of cold work, so that energy considerations can be used to macroscopically model the failure mechanism. The initial mechanisms that lead to final failure are still unknown, as well as the ASB formation mechanism(s). Most of all - is ASB an abrupt instability or rather a gradual transition as would be dictated by microstructural evolutions? This paper reports thorough microstructural characterizations that clearly show the gradual character of the phenomenon, best described as a nucleation and growth failure mechanism, and not as an abrupt instability as previously thought. These observations are coupled to a simple numerical model that illustrates them. PMID:27849023

  12. Accurate Variational Description of Adiabatic Quantum Optimization

    NASA Astrophysics Data System (ADS)

    Carleo, Giuseppe; Bauer, Bela; Troyer, Matthias

    Adiabatic quantum optimization (AQO) is a quantum computing protocol where a system is driven by a time-dependent Hamiltonian. The initial Hamiltonian has an easily prepared ground-state and the final Hamiltonian encodes some desired optimization problem. An adiabatic time evolution then yields a solution to the optimization problem. Several challenges emerge in the theoretical description of this protocol: on one hand, the exact simulation of quantum dynamics is exponentially complex in the size of the optimization problem. On the other hand, approximate approaches such as tensor network states (TNS) are limited to small instances by the amount of entanglement that can be encoded. I will present here an extension of the time-dependent Variational Monte Carlo approach to problems in AQO. This approach is based on a general class of (Jastrow-Feenberg) entangled states, whose parameters are evolved in time according to a stochastic variational principle. We demonstrate this approach for optimization problems of the Ising spin-glass type. A very good accuracy is achieved when compared to exact time-dependent TNS on small instances. We then apply this approach to larger problems, and discuss the efficiency of the quantum annealing scheme in comparison with its classical counterpart.

  13. Nonadiabatic Transitions in Adiabatic Rapid Passage

    NASA Astrophysics Data System (ADS)

    Lu, T.; Miao, X.; Metcalf, H.

    2006-05-01

    Optical forces much larger than the ordinary radiative force can be achieved on a two-level atom by multiple repetitions of adiabatic rapid passage sweeps with counterpropagating light beams. Chirped light pulses drive the atom-laser system up a ladder of dressed state energy sheets on sequential trajectories, thereby decreasing the atomic kinetic energy. Nonadiabatic transitions between the energy sheets must be avoided for this process to be effective. We have calculated the nonadiabatic transition probability for various chirped light pulses numerically. These results were compared to the first Demkov-Kunike model and the well-known Landau-Zener model. In addition, an analytical form of the nonadiabatic transition probability has been found for linearly chirped pulses and an approximate form for generic symmetric finite-time pulses has been found for the entire parameter space using the technique of unitary integration. From this, the asymptotic transition probability in the adiabatic limit was derived. T. Lu, X. Miao, and H. Metcalf, Phys., Rev. A 71 061405(R) (2005). Yu. Demkov and M. Kunike, Vestn. Leningr. Univ. Fis. Khim., 16, 39 (1969); K.-A. Suominen and B. Garraway, Phys. Rev. A45, 374 (1992)

  14. The formation of multiple adiabatic shear bands

    NASA Astrophysics Data System (ADS)

    Zhou, F.; Wright, T. W.; Ramesh, K. T.

    2006-07-01

    In a previous paper, Zhou et al. [2006. A numerical methodology for investigating adiabatic shear band formation. J. Mech. Phys. Solids, 54, 904-926] developed a numerical method for analyzing one-dimensional deformation of thermoviscoplastic materials. The method uses a second order algorithm for integration along characteristic lines, and computes the plastic flow after complete localization with high resolution and efficiency. We apply this numerical scheme to analyze localization in a thermoviscoplastic material where multiple shear bands are allowed to form at random locations in a large specimen. As a shear band develops, it unloads neighboring regions and interacts with other bands. Beginning with a random distribution of imperfections, which might be imagined as arising qualitatively from the microstructure, we obtain the average spacing of shear bands through calculations and compare our results with previously existing theoretical estimates. It is found that the spacing between nucleating shear bands follows the perturbation theory due to Wright and Ockendon [1996. A scaling law for the effect of inertia on the formation of adiabatic shear bands. Int. J. Plasticity 12, 927-934], whereas the spacing between mature shear bands is closer to that predicted by the momentum diffusion theory of Grady and Kipp [1987. The growth of unstable thermoplastic shear with application to steady-wave shock compression in solids. J. Mech. Phys. Solids 35, 95-119]. Scaling laws for the dependence of band spacing on material parameters differ in many respects from either theory.

  15. Adiabatic cooling of solar wind electrons

    NASA Technical Reports Server (NTRS)

    Sandbaek, Ornulf; Leer, Egil

    1992-01-01

    In thermally driven winds emanating from regions in the solar corona with base electron densities of n0 not less than 10 exp 8/cu cm, a substantial fraction of the heat conductive flux from the base is transfered into flow energy by the pressure gradient force. The adiabatic cooling of the electrons causes the electron temperature profile to fall off more rapidly than in heat conduction dominated flows. Alfven waves of solar origin, accelerating the basically thermally driven solar wind, lead to an increased mass flux and enhanced adiabatic cooling. The reduction in electron temperature may be significant also in the subsonic region of the flow and lead to a moderate increase of solar wind mass flux with increasing Alfven wave amplitude. In the solar wind model presented here the Alfven wave energy flux per unit mass is larger than that in models where the temperature in the subsonic flow is not reduced by the wave, and consequently the asymptotic flow speed is higher.

  16. Non-adiabatic Rayleigh-Taylor instability

    NASA Astrophysics Data System (ADS)

    Canfield, Jesse; Denissen, Nicholas; Reisner, Jon

    2016-11-01

    Onset of Rayleigh-Taylor instability (RTI) in a non-adiabatic environment is investigated with the multi-physics numerical model, FLAG. This work was inspired by laboratory experiments of non-adiabatic RTI, where a glass vessel with a layer of tetrahyrdofuran (THF) below a layer of toluene was placed inside a microwave. THF, a polar solvent, readily absorbs electromagnetic energy from microwaves. Toluene, a non-polar solvent, is nearly transparent to microwave heating. The presence of a heat source in the THF layer produced convection and a time-dependent Atwood number (At). The system, initially in stable hydrostatic equilibrium At < 0 , was set into motion by microwave induced, volumetric heating of the THF. The point when At > 0 , indicates that the system is RTI unstable. The observed dominant mode at the onset of RTI was the horizontal length scale of the vessel. This scale is contrary to classical RTI, where the modes start small and increases in scale with time. It is shown that the dominant RTI mode observed in the experiments was determined by the THF length scale prior to RTI. The dominant length scale transitions from the THF to the toluene via the updrafts and downdrafts in the convective cells. This happens when At passes from negative to positive. This work was funded by the Advanced Simulation and Computing Program.

  17. Delayed, disequilibrium degassing in rhyolite magma: Decompression experiments and implications for explosive volcanism

    USGS Publications Warehouse

    Mangan, M.; Sisson, T.

    2000-01-01

    Recent numerical models and analog shock tube experiments show that disequilibrium degassing during magma ascent may lead to violent vesiculation very near the surface. In this study a series of decompression experiments using crystal-free, rhyolite melt were conducted to examine the development of large supersaturations due to delayed, homogenous (spontaneous) bubble nucleation. Melts were saturated at 900??C and 200 MPa with either 5.2 wt% dissolved H2O, or with 4.2 wt% H2O and 640 ppm CO2, and isothermally decompressed at linear rates of either 0.003, 0.025, or 8.5 MPa/s to final pressures between 25 and 175 MPa. Additional isobaric saturation experiments (900??C, 200-25 MPa) using pure H2O or mixed H2O-CO2 fluids establish reference equilibrium solubility curves/values. Homogenous nucleation is triggered in both H2O-only and H2O-CO2 experiments once the supersaturation pressure (??Pss) reaches ?? 120-150 MPa and the melt contains ?? two times its equilibrium water contents. Bubble number density and nucleation rate depend on the supersaturation pressure, with values on the order of 102/cm3 and < 1/cm3/s for ??Pss~120 MPa; 106/cm3 and 103-105/cm3/s for ??Pss??~130-150 MPa; and 107/cm3 and 106/cm3/s for ??Pss??160-175 MPa. Nucleation rates are consistent with classical nucleation theory, and infer an activation energy for nucleation of 1.5 x 10-18 J/nucleus, a critical bubble radius of 2 x 10-9 m, and an effective surface tension for rhyolite at 5.2 wt% H2O and 900??C of 0.10-0.11 N/m. The long nucleation delay limits the time available for subsequent diffusion such that disequilibrium dissolved H2O and CO2 contents persist to the end of our runs. The disequilibrium degassing paths inferred from our experiments contrast markedly with the equilibrium or quasi-equilibrium paths found in other studies where bubble nucleation occurs heterogenously on crystals or other discontinuities in the melt at low ??Pss. Homogenous and heterogenous nucleation rates are

  18. Adiabatic effects of electrons and ions on electro-acoustic solitary waves in an adiabatic dusty plasma

    NASA Astrophysics Data System (ADS)

    Tanjia, Fatema; Mamun, A. A.

    2009-02-01

    A dusty plasma consisting of negatively charged cold dust, adiabatic hot ions, and inertia-less adiabatic hot electrons has been considered. The adiabatic effects of electrons and ions on the basic properties of electro-acoustic solitary waves associated with different types of electro-acoustic (viz. ion-acoustic (IA), dust ion-acoustic (DIA), and dust acoustic (DA)) waves are thoroughly investigated by the reductive perturbation method. It is found that the basic properties of the IA, DIA, and DA waves are significantly modified by the adiabatic effects of ions and inertia-less electrons. The implications of our results in space and laboratory dusty plasmas are briefly discussed.

  19. 46 CFR Appendix A to Part 197 - Air No-Decompression Limits

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Air No-Decompression Limits A Appendix A to Part 197... STANDARDS GENERAL PROVISIONS Pt. 197, App. A Appendix A to Part 197—Air No-Decompression Limits The following table gives the depth versus bottom time limits for single, no-decompression, air dives...

  20. Decompressive Craniectomy and Traumatic Brain Injury: A Review

    PubMed Central

    Alvis-Miranda, Hernando; Castellar-Leones, Sandra Milena; Moscote-Salazar, Luis Rafael

    2013-01-01

    Intracranial hypertension is the largest cause of death in young patients with severe traumatic brain injury. Decompressive craniectomy is part of the second level measures for the management of increased intracranial pressure refractory to medical management as moderate hypothermia and barbiturate coma. The literature lack of concepts is their indications. We present a review on the state of the art. PMID:27162826

  1. Endoscopic decompression for intraforaminal and extraforaminal nerve root compression

    PubMed Central

    2011-01-01

    Objective The purpose of this study was to evaluate the outcome of endoscopic decompression surgery for intraforaminal and extraforaminal nerve root compression in the lumbar spine. Methods The records from seventeen consecutive patients treated with endoscopic posterior decompression without fusion for intaforaminal and extraforaminal nerve root compression in the lumbar spine (7 males and 10 females, mean age: 67.9 ± 10.7 years) were retrospectively reviewed. The surgical procedures consisted of lateral or translaminal decompression with or without discectomy. The following items were investigated: 1) the preoperative clinical findings; 2) the radiologic findings including MRI and computed tomography-discography; and 3) the surgical outcome as evaluated using the Japanese Orthopaedic Association scale for lower back pain (JOA score). Results All patients had neurological findings compatible with a radiculopathy, such as muscle weakness and sensory disturbance. MRI demonstrated the obliteration of the normal increased signal intensity fat in the intervertebral foramen. Ten patients out of 14 who underwent computed tomography-discography exhibited disc protrusion or herniation. Selective nerve root block was effective in all patients. During surgery, 12 patients were found to have a protruded disc or herniation that compressed the nerve root. Sixteen patients reported pain relief immediately after surgery. Conclusions Intraforaminal and extraforaminal nerve root compression is a rare but distinct pathological condition causing severe radiculopathy. Endoscopic decompression surgery is considered to be an appropriate and less invasive surgical option. PMID:21439083

  2. 46 CFR 197.332 - PVHO-Decompression chambers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... minimum pressure capability of— (1) 6 ATA, when used for diving to 300 fsw; or (2) The maximum depth of the dive, when used for diving operations deeper than 300 fsw, unless a closed bell meeting the... minute to 60 fsw and at least 1 ATA per minute thereafter; (j) Have a decompression rate of 1 ATA...

  3. 46 CFR 197.332 - PVHO-Decompression chambers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... minimum pressure capability of— (1) 6 ATA, when used for diving to 300 fsw; or (2) The maximum depth of the dive, when used for diving operations deeper than 300 fsw, unless a closed bell meeting the... minute to 60 fsw and at least 1 ATA per minute thereafter; (j) Have a decompression rate of 1 ATA...

  4. 46 CFR 197.332 - PVHO-Decompression chambers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... minimum pressure capability of— (1) 6 ATA, when used for diving to 300 fsw; or (2) The maximum depth of the dive, when used for diving operations deeper than 300 fsw, unless a closed bell meeting the... minute to 60 fsw and at least 1 ATA per minute thereafter; (j) Have a decompression rate of 1 ATA...

  5. 46 CFR 197.332 - PVHO-Decompression chambers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... minimum pressure capability of— (1) 6 ATA, when used for diving to 300 fsw; or (2) The maximum depth of the dive, when used for diving operations deeper than 300 fsw, unless a closed bell meeting the... minute to 60 fsw and at least 1 ATA per minute thereafter; (j) Have a decompression rate of 1 ATA...

  6. 46 CFR 197.332 - PVHO-Decompression chambers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... minimum pressure capability of— (1) 6 ATA, when used for diving to 300 fsw; or (2) The maximum depth of the dive, when used for diving operations deeper than 300 fsw, unless a closed bell meeting the... minute to 60 fsw and at least 1 ATA per minute thereafter; (j) Have a decompression rate of 1 ATA...

  7. A Log Logistic Survival Model Applied to Hypobaric Decompression Sickness

    NASA Technical Reports Server (NTRS)

    Conkin, Johnny

    2001-01-01

    Decompression sickness (DCS) is a complex, multivariable problem. A mathematical description or model of the likelihood of DCS requires a large amount of quality research data, ideas on how to define a decompression dose using physical and physiological variables, and an appropriate analytical approach. It also requires a high-performance computer with specialized software. I have used published DCS data to develop my decompression doses, which are variants of equilibrium expressions for evolved gas plus other explanatory variables. My analytical approach is survival analysis, where the time of DCS occurrence is modeled. My conclusions can be applied to simple hypobaric decompressions - ascents lasting from 5 to 30 minutes - and, after minutes to hours, to denitrogenation (prebreathing). They are also applicable to long or short exposures, and can be used whether the sufferer of DCS is at rest or exercising at altitude. Ultimately I would like my models to be applied to astronauts to reduce the risk of DCS during spacewalks, as well as to future spaceflight crews on the Moon and Mars.

  8. The Design and Development of the Topside Decompression Monitor

    DTIC Science & Technology

    2011-06-01

    4 Subsea Cable CE-3T-6-100UC ................................................... 5 Diver-Worn Depth Sensor ...laptop computer, instrumentation case, diver instrumentation cable, and diver-worn depth sensor ; its software components include a decompression program...1 Sensor Instrumentation Case ................................................................. 1 Diver

  9. A Modified Adiabatic Quantum Algorithm for Evaluation of Boolean Functions

    NASA Astrophysics Data System (ADS)

    Sun, Jie; Lu, Songfeng; Liu, Fang

    2015-09-01

    In this paper, we propose a modified construction of the quantum adiabatic algorithm for Boolean functions studied by M. Andrecut et al. [13, 14]. Our algorithm has the time complexity O(1) for the evaluation of Boolean functions, without additional computational cost of implementing the driving Hamiltonian, which is required by the adiabatic evolution described in [13, 14].

  10. Adiabat-shaping in indirect drive inertial confinement fusion

    SciTech Connect

    Baker, K. L.; Robey, H. F.; Milovich, J. L.; Jones, O. S.; Smalyuk, V. A.; Casey, D. T.; MacPhee, A. G.; Pak, A.; Celliers, P. M.; Clark, D. S.; Landen, O. L.; Peterson, J. L.; Berzak-Hopkins, L. F.; Weber, C. R.; Haan, S. W.; Döppner, T. D.; Dixit, S.; Hamza, A. V.; Jancaitis, K. S.; Kroll, J. J.; and others

    2015-05-15

    Adiabat-shaping techniques were investigated in indirect drive inertial confinement fusion experiments on the National Ignition Facility as a means to improve implosion stability, while still maintaining a low adiabat in the fuel. Adiabat-shaping was accomplished in these indirect drive experiments by altering the ratio of the picket and trough energies in the laser pulse shape, thus driving a decaying first shock in the ablator. This decaying first shock is designed to place the ablation front on a high adiabat while keeping the fuel on a low adiabat. These experiments were conducted using the keyhole experimental platform for both three and four shock laser pulses. This platform enabled direct measurement of the shock velocities driven in the glow-discharge polymer capsule and in the liquid deuterium, the surrogate fuel for a DT ignition target. The measured shock velocities and radiation drive histories are compared to previous three and four shock laser pulses. This comparison indicates that in the case of adiabat shaping the ablation front initially drives a high shock velocity, and therefore, a high shock pressure and adiabat. The shock then decays as it travels through the ablator to pressures similar to the original low-adiabat pulses when it reaches the fuel. This approach takes advantage of initial high ablation velocity, which favors stability, and high-compression, which favors high stagnation pressures.

  11. The Adiabatic Invariance of the Action Variable in Classical Dynamics

    ERIC Educational Resources Information Center

    Wells, Clive G.; Siklos, Stephen T. C.

    2007-01-01

    We consider one-dimensional classical time-dependent Hamiltonian systems with quasi-periodic orbits. It is well known that such systems possess an adiabatic invariant which coincides with the action variable of the Hamiltonian formalism. We present a new proof of the adiabatic invariance of this quantity and illustrate our arguments by means of…

  12. Kinetic Theory Derivation of the Adiabatic Law for Ideal Gases.

    ERIC Educational Resources Information Center

    Sobel, Michael I.

    1980-01-01

    Discusses how the adiabatic law for ideal gases can be derived from the assumption of a Maxwell-Boltzmann (or any other) distribution of velocities--in contrast to the usual derivations from thermodynamics alone, and the higher-order effect that leads to one-body viscosity. An elementary derivation of the adiabatic law is given. (Author/DS)

  13. Quantum Adiabatic Optimization and Combinatorial Landscapes

    NASA Technical Reports Server (NTRS)

    Smelyanskiy, V. N.; Knysh, S.; Morris, R. D.

    2003-01-01

    In this paper we analyze the performance of the Quantum Adiabatic Evolution (QAE) algorithm on a variant of Satisfiability problem for an ensemble of random graphs parametrized by the ratio of clauses to variables, gamma = M / N. We introduce a set of macroscopic parameters (landscapes) and put forward an ansatz of universality for random bit flips. We then formulate the problem of finding the smallest eigenvalue and the excitation gap as a statistical mechanics problem. We use the so-called annealing approximation with a refinement that a finite set of macroscopic variables (verses only energy) is used, and are able to show the existence of a dynamic threshold gamma = gammad, beyond which QAE should take an exponentially long time to find a solution. We compare the results for extended and simplified sets of landscapes and provide numerical evidence in support of our universality ansatz.

  14. Number Partitioning via Quantum Adiabatic Computation

    NASA Technical Reports Server (NTRS)

    Smelyanskiy, Vadim N.; Toussaint, Udo; Clancy, Daniel (Technical Monitor)

    2002-01-01

    We study both analytically and numerically the complexity of the adiabatic quantum evolution algorithm applied to random instances of combinatorial optimization problems. We use as an example the NP-complete set partition problem and obtain an asymptotic expression for the minimal gap separating the ground and exited states of a system during the execution of the algorithm. We show that for computationally hard problem instances the size of the minimal gap scales exponentially with the problem size. This result is in qualitative agreement with the direct numerical simulation of the algorithm for small instances of the set partition problem. We describe the statistical properties of the optimization problem that are responsible for the exponential behavior of the algorithm.

  15. The HAWC and SAFIRE Adiabatic Demagnetization Refrigerators

    NASA Technical Reports Server (NTRS)

    Tuttle, Jim; Shirron, Peter; DiPirro, Michael; Jackson, Michael; Behr, Jason; Kunes, Evan; Hait, Tom; Krebs, Carolyn (Technical Monitor)

    2001-01-01

    The High-Resolution Airborne Wide-band Camera (HAWC) and Submillimeter and Far Infrared Experiment (SAFIRE) are far-infrared experiments which will fly on the Stratospheric Observatory for Infrared Astronomy (SOFIA) aircraft. HAWC's detectors will operate at 0.2 Kelvin, while those of SAFIRE will be at 0.1 Kelvin. Each instrument will include an adiabatic demagnetization refrigerator (ADR) to cool its detector stage from the liquid helium bath temperature (HAWC's at 4.2 Kelvin and SAFIRE's pumped to about 1.3 Kelvin) to its operating temperature. Except for the magnets used to achieve the cooling and a slight difference in the heat switch design, the two ADRs are nearly identical. We describe the ADR design and present the results of performance testing.

  16. Sliding seal materials for adiabatic engines

    NASA Technical Reports Server (NTRS)

    Lankford, J.

    1985-01-01

    The sliding friction coefficients and wear rates of promising carbide, oxide, and nitride materials were measured under temperature, environmental, velocity, loading conditions that are representative of the adiabatic engine environment. In order to provide guidance needed to improve materials for this application, the program stressed fundamental understanding of the mechanisms involved in friction and wear. Microhardness tests were performed on the candidate materials at elevated temperatures, and in atmospheres relevant to the piston seal application, and optical and electron microscopy were used to elucidate the micromechanisms of wear following wear testing. X-ray spectroscopy was used to evaluate interface/environment interactions which seemed to be important in the friction and wear process. Electrical effects in the friction and wear processes were explored in order to evaluate the potential usefulness of such effects in modifying the friction and wear rates in service. However, this factor was found to be of negligible significance in controlling friction and wear.

  17. An adiabatic demagnetization refrigerator for SIRTF

    NASA Astrophysics Data System (ADS)

    Timbie, P. T.; Bernstein, G. M.; Richards, P. L.

    1989-02-01

    An adiabatic demagnetization refrigerator (ADR) has been proposed to cool bolometric infrared detectors on the multiband imaging photometer of the Space Infrared Telescope Facility (SIRTF). One such refrigerator has been built which uses a ferric ammonium alum salt pill suspended by nylon threads in a 3-T solenoid. The resonant modes of this suspension are above 100 Hz. The heat leak to the salt pill is less than 0.5 microW. The system has a hold time at 0.1K of more than 12 h. The cold stage temperature is regulated with a feedback loop that controls the magnetic field. A second, similar refrigerator is being built at a SIRTF prototype to fly on a ballon-borne telescope. It will use a ferromagnetic shield. The possibility of using a high-Tc solenoid-actuated heat switch is also discussed.

  18. Design of a spaceworthy adiabatic demagnetization refrigerator

    NASA Astrophysics Data System (ADS)

    Serlemitsos, A. T.; Kunes, E.; Sansebastian, M.

    A spaceworthy adiabatic demagnetization refrigerator (ADR) under development at NASA-Goddard is presented. A baseline model heat switch was tested extensively with an on/off ratio of about 10,000 and a parasitic heat leak of 10 micro-W. Data obtained from the breadboard models were used to design an ADR with improved structural integrity. The core of the ADR is the salt pill which consists of the paramagnetic salt crystal and the thermal bus. When a magnetic field is applied to the salt it forces the alignment of the magnetic moments, thereby decreasing the entropy of the salt. Preliminary tests results showed a net crystal mass of 680 g instead of the expected 740 g, which indicate that there are gaps in the salt pill. A partial fix was accomplished by sealing helium gas in the salt pill at a pressure of 2 bar, which improved the thermal contact during salt magnetization, at about 2 K.

  19. On stress collapse in adiabatic shear bands

    NASA Astrophysics Data System (ADS)

    Wright, T. W.; Walter, J. W.

    T HE DYNAMICS of adiabatic shear band formation is considered making use of a simplified thermo/visco/plastic flow law. A new numerical solution is used to follow the growth of a perturbation from initiation, through early growth and severe localization, to a slowly varying terminal configuration. Asymptotic analyses predict the early and late stage patterns, but the timing and structure of the abrupt transition to severe localization can only be studied numerically, to date. A characteristic feature of the process is that temperature and plastic strain rate begin to localize immediately, but only slowly, whereas the stress first evolves almost as if there were no perturbation, but then collapses rapidly when severe localization occurs.

  20. Index Theory and Adiabatic Limit in QFT

    NASA Astrophysics Data System (ADS)

    Wawrzycki, Jarosław

    2013-08-01

    The paper has the form of a proposal concerned with the relationship between the three mathematically rigorous approaches to quantum field theory: (1) local algebraic formulation of Haag, (2) Wightman formulation and (3) the perturbative formulation based on the microlocal renormalization method. In this project we investigate the relationship between (1) and (3) and utilize the known relationships between (1) and (2). The main goal of the proposal lies in obtaining obstructions for the existence of the adiabatic limit ( confinement problem in the phenomenological standard model approach). We extend the method of deformation of Dütsch and Fredenhagen (in the Bordeman-Waldmann sense) and apply Fedosov construction of the formal index—an analog of the index for deformed symplectic manifolds, generalizing the Atiyah-Singer index. We present some first steps in realization of the proposal.

  1. An adiabatic demagnetization refrigerator for SIRTF

    NASA Technical Reports Server (NTRS)

    Timbie, P. T.; Bernstein, G. M.; Richards, P. L.

    1989-01-01

    An adiabatic demagnetization refrigerator (ADR) has been proposed to cool bolometric infrared detectors on the multiband imaging photometer of the Space Infrared Telescope Facility (SIRTF). One such refrigerator has been built which uses a ferric ammonium alum salt pill suspended by nylon threads in a 3-T solenoid. The resonant modes of this suspension are above 100 Hz. The heat leak to the salt pill is less than 0.5 microW. The system has a hold time at 0.1K of more than 12 h. The cold stage temperature is regulated with a feedback loop that controls the magnetic field. A second, similar refrigerator is being built at a SIRTF prototype to fly on a ballon-borne telescope. It will use a ferromagnetic shield. The possibility of using a high-Tc solenoid-actuated heat switch is also discussed.

  2. Design of a spaceworthy adiabatic demagnetization refrigerator

    NASA Technical Reports Server (NTRS)

    Serlemitsos, A. T.; Kunes, E.; Sansebastian, M.

    1992-01-01

    A spaceworthy adiabatic demagnetization refrigerator (ADR) under development at NASA-Goddard is presented. A baseline model heat switch was tested extensively with an on/off ratio of about 10,000 and a parasitic heat leak of 10 micro-W. Data obtained from the breadboard models were used to design an ADR with improved structural integrity. The core of the ADR is the salt pill which consists of the paramagnetic salt crystal and the thermal bus. When a magnetic field is applied to the salt it forces the alignment of the magnetic moments, thereby decreasing the entropy of the salt. Preliminary tests results showed a net crystal mass of 680 g instead of the expected 740 g, which indicate that there are gaps in the salt pill. A partial fix was accomplished by sealing helium gas in the salt pill at a pressure of 2 bar, which improved the thermal contact during salt magnetization, at about 2 K.

  3. Adiabatic connection at negative coupling strengths

    SciTech Connect

    Seidl, Michael; Gori-Giorgi, Paola

    2010-01-15

    The adiabatic connection of density functional theory (DFT) for electronic systems is generalized here to negative values of the coupling strength alpha (with attractive electrons). In the extreme limit alpha->-infinity a simple physical solution is presented and its implications for DFT (as well as its limitations) are discussed. For two-electron systems (a case in which the present solution can be calculated exactly), we find that an interpolation between the limit alpha->-infinity and the opposite limit of infinitely strong repulsion (alpha->+infinity) yields a rather accurate estimate of the second-order correlation energy E{sub c}{sup GL2}[rho] for several different densities rho, without using virtual orbitals. The same procedure is also applied to the Be isoelectronic series, analyzing the effects of near degeneracy.

  4. Adiabatic theory for anisotropic cold molecule collisions

    SciTech Connect

    Pawlak, Mariusz; Shagam, Yuval; Narevicius, Edvardas; Moiseyev, Nimrod

    2015-08-21

    We developed an adiabatic theory for cold anisotropic collisions between slow atoms and cold molecules. It enables us to investigate the importance of the couplings between the projection states of the rotational motion of the atom about the molecular axis of the diatom. We tested our theory using the recent results from the Penning ionization reaction experiment {sup 4}He(1s2s {sup 3}S) + HD(1s{sup 2}) → {sup 4}He(1s{sup 2}) + HD{sup +}(1s) + e{sup −} [Lavert-Ofir et al., Nat. Chem. 6, 332 (2014)] and demonstrated that the couplings have strong effect on positions of shape resonances. The theory we derived provides cross sections which are in a very good agreement with the experimental findings.

  5. An Integrated Development Environment for Adiabatic Quantum Programming

    SciTech Connect

    Humble, Travis S; McCaskey, Alex; Bennink, Ryan S; Billings, Jay Jay; D'Azevedo, Eduardo; Sullivan, Blair D; Klymko, Christine F; Seddiqi, Hadayat

    2014-01-01

    Adiabatic quantum computing is a promising route to the computational power afforded by quantum information processing. The recent availability of adiabatic hardware raises the question of how well quantum programs perform. Benchmarking behavior is challenging since the multiple steps to synthesize an adiabatic quantum program are highly tunable. We present an adiabatic quantum programming environment called JADE that provides control over all the steps taken during program development. JADE captures the workflow needed to rigorously benchmark performance while also allowing a variety of problem types, programming techniques, and processor configurations. We have also integrated JADE with a quantum simulation engine that enables program profiling using numerical calculation. The computational engine supports plug-ins for simulation methodologies tailored to various metrics and computing resources. We present the design, integration, and deployment of JADE and discuss its use for benchmarking adiabatic quantum programs.

  6. An integrated programming and development environment for adiabatic quantum optimization

    NASA Astrophysics Data System (ADS)

    Humble, T. S.; McCaskey, A. J.; Bennink, R. S.; Billings, J. J.; DʼAzevedo, E. F.; Sullivan, B. D.; Klymko, C. F.; Seddiqi, H.

    2014-01-01

    Adiabatic quantum computing is a promising route to the computational power afforded by quantum information processing. The recent availability of adiabatic hardware has raised challenging questions about how to evaluate adiabatic quantum optimization (AQO) programs. Processor behavior depends on multiple steps to synthesize an adiabatic quantum program, which are each highly tunable. We present an integrated programming and development environment for AQO called Jade Adiabatic Development Environment (JADE) that provides control over all the steps taken during program synthesis. JADE captures the workflow needed to rigorously specify the AQO algorithm while allowing a variety of problem types, programming techniques, and processor configurations. We have also integrated JADE with a quantum simulation engine that enables program profiling using numerical calculation. The computational engine supports plug-ins for simulation methodologies tailored to various metrics and computing resources. We present the design, integration, and deployment of JADE and discuss its potential use for benchmarking AQO programs by the quantum computer science community.

  7. Adiabatic theory, Liapunov exponents, and rotation number for quadratic Hamiltonians

    NASA Astrophysics Data System (ADS)

    Delyon, François; Foulon, Patrick

    1987-11-01

    We consider the adiabatic problem for general time-dependent quadratic Hamiltonians and develop a method quite different from WKB. In particular, we apply our results to the Schrödinger equation in a strip. We show that there exists a first regular step (avoiding resonance problems) providing one adiabatic invariant, bounds on the Liapunov exponents, and estimates on the rotation number at any order of the perturbation theory. The further step is shown to be equivalent to a quantum adiabatic problem, which, by the usual adiabatic techniques, provides the other possible adiabatic invariants. In the special case of the Schrödinger equation our method is simpler and more powerful than the WKB techniques.

  8. Role of Inflammatory Reponse in Experimental Decompression Sickness

    NASA Technical Reports Server (NTRS)

    Butler, B. D.; Little, T.

    1999-01-01

    Decompression to altitude can result in gas bubble formation both in tissues and in the systemic veins. The venous gas emboli (VGE) are often monitored during decompression exposures to assess risk for decompression sickness (DCS). Astronauts are at risk for DCS during extravehicular activities (EVA), where decompression occurs from the Space Shuttle or Space Station atmospheric pressure of 14.7 pounds per square inch (PSI) to that of the space suit pressure of 4.3 PSI. DCS symptoms include diffuse pain, especially around joints, inflammation and edema. Pathophysiological effects include interstitial inflammatory responses and recurring injury to the vascular endothelium. Such responses can result in vasoconstriction and associated hemodynamic changes.The granulocyte cell activation and chemotaxin release results in the formation of vasoactive and microvascular permeability altering mediators, especially from the lungs which are the principal target organ for the venous bubbles, and from activated cells (neutrophils, platelets, macrophages). Such mediators include free arachidonic acid and the byproducts of its metabolism via the cyclooxygenase and lipoxygenase pathways (see figure). The cyclooxygenase pathway results in formation of prostacyclin and other prostaglandins and thromboxanes that cause vasoconstriction, bronchoconstriction and platelet aggregation. Leukotrienes produced by the alternate pathway cause pulmonary and bronchial smooth muscle contraction and edema. Substances directly affecting vascular tone such as nitric oxide may also play a role in the respose to DCS. We are studying the role and consequent effects of the release inflammatory bioactive mediators as a result of DCS and VGE. More recent efforts are focused on identifying the effects of the body's circadian rhythm on these physiological consequences to decompression stress. al

  9. Adiabatic vs. non-adiabatic determination of specific absorption rate of ferrofluids

    NASA Astrophysics Data System (ADS)

    Natividad, Eva; Castro, Miguel; Mediano, Arturo

    2009-05-01

    The measurement of temperature variations in adiabatic conditions allows the determination of the specific absorption rate of magnetic nanoparticles and ferrofluids from the correct incremental expression, SAR=(1/ m MNP) C(Δ T/Δ t). However, when measurements take place in non-adiabatic conditions, one must approximate this expression by SAR≈ Cβ/ m MNP, where β is the initial slope of the temperature vs. time curve during alternating field application. The errors arising from the use of this approximation were estimated through several experiments with different isolating conditions, temperature sensors and sample-sensor contacts. It is concluded that small to appreciable errors can appear, which are difficult to infer or control.

  10. Non-adiabatic molecular dynamics with complex quantum trajectories. II. The adiabatic representation

    SciTech Connect

    Zamstein, Noa; Tannor, David J.

    2012-12-14

    We present a complex quantum trajectory method for treating non-adiabatic dynamics. Each trajectory evolves classically on a single electronic surface but with complex position and momentum. The equations of motion are derived directly from the time-dependent Schroedinger equation, and the population exchange arises naturally from amplitude-transfer terms. In this paper the equations of motion are derived in the adiabatic representation to complement our work in the diabatic representation [N. Zamstein and D. J. Tannor, J. Chem. Phys. 137, 22A517 (2012)]. We apply our method to two benchmark models introduced by John Tully [J. Chem. Phys. 93, 1061 (1990)], and get very good agreement with converged quantum-mechanical calculations. Specifically, we show that decoherence (spatial separation of wavepackets on different surfaces) is already contained in the equations of motion and does not require ad hoc augmentation.

  11. Energy decomposition analysis in an adiabatic picture.

    PubMed

    Mao, Yuezhi; Horn, Paul R; Head-Gordon, Martin

    2017-02-22

    Energy decomposition analysis (EDA) of electronic structure calculations has facilitated quantitative understanding of diverse intermolecular interactions. Nevertheless, such analyses are usually performed at a single geometry and thus decompose a "single-point" interaction energy. As a result, the influence of the physically meaningful EDA components on the molecular structure and other properties are not directly obtained. To address this gap, the absolutely localized molecular orbital (ALMO)-EDA is reformulated in an adiabatic picture, where the frozen, polarization, and charge transfer energy contributions are defined as energy differences between the stationary points on different potential energy surfaces (PESs), which are accessed by geometry optimizations at the frozen, polarized and fully relaxed levels of density functional theory (DFT). Other molecular properties such as vibrational frequencies can thus be obtained at the stationary points on each PES. We apply the adiabatic ALMO-EDA to different configurations of the water dimer, the water-Cl(-) and water-Mg(2+)/Ca(2+) complexes, metallocenes (Fe(2+), Ni(2+), Cu(2+), Zn(2+)), and the ammonia-borane complex. This method appears to be very useful for unraveling how physical effects such as polarization and charge transfer modulate changes in molecular properties induced by intermolecular interactions. As an example of the insight obtained, we find that a linear hydrogen bond geometry for the water dimer is preferred even without the presence of polarization and charge transfer, while the red shift in the OH stretch frequency is primarily a charge transfer effect; by contrast, a near-linear geometry for the water-chloride hydrogen bond is achieved only when charge transfer is allowed.

  12. Lattice Boltzmann technique for heat transport phenomena coupled with melting process

    NASA Astrophysics Data System (ADS)

    Ibrahem, A. M.; El-Amin, M. F.; Mohammadein, A. A.; Gorla, Rama Subba Reddy

    2017-01-01

    In this work, the heat transport phenomena coupled with melting process are studied by using the enthalpy-based lattice Boltzmann method (LBM). The proposed model is a modified version of thermal LB model, where could avoid iteration steps and ensures high accuracy. The Bhatnagar-Gross-Krook (BGK) approximation with a D1Q2 lattice was used to determine the temperature field for one-dimensional melting by conduction and multi-distribution functions (MDF) with D2Q9 lattice was used to determine the density, velocity and temperature fields for two-dimensional melting by natural convection. Different boundary conditions including Dirichlet, adiabatic and bounce-back boundary conditions were used. The influence of increasing Rayleigh number (from 103 to 105) on temperature distribution and melting process is studied. The obtained results show that a good agreement with the analytical solution for melting by conduction case and with the benchmark solution for melting by convection.

  13. Rupture of the cell envelope by decompression of the deep-sea methanogen Methanococcus jannaschii.

    PubMed

    Park, Chan Beum; Clark, Douglas S

    2002-03-01

    The effect of decompression on the structure of Methanococcus jannaschii, an extremely thermophilic deep-sea methanogen, was studied in a novel high-pressure, high-temperature bioreactor. The cell envelope of M. jannaschii appeared to rupture upon rapid decompression (ca. 1 s) from 260 atm of hyperbaric pressure. When decompression from 260 atm was performed over 5 min, the proportion of ruptured cells decreased significantly. In contrast to the effect produced by decompression from hyperbaric pressure, decompression from a hydrostatic pressure of 260 atm did not induce cell lysis.

  14. Rates of Melt Migration Following Deglaciation-Induced Mantle Melting Revealed by Studies of Icelandic Table Mountains

    NASA Astrophysics Data System (ADS)

    Eason, D. E.; Sinton, J. M.; Ito, G.; Gronvold, K.; Kurz, M. D.

    2010-12-01

    Deglaciation leads to enhanced melt production under Iceland due to mantle decompression during glacial unloading. Models of isostatic rebound following ice sheet removal predict the greatest melt perturbations at shallow depths, with corresponding changes in the chemical composition of erupted material. Some table mountains (tuyas, or stapi) in Iceland are thought to have erupted through a thinning ice sheet during ice retreat following the last glacial maximum (~15-11 ka). New observations and geochemical analyses of table mountains in the 170 km-long Western Volcanic Zone (WVZ) of Iceland constrain spatial and temporal variations in volcanic production and composition associated with the last deglaciation period. We present new major and trace element compositional data for 19 table mountains in the WVZ, and use a combination of lava surface morphology, passage zone heights, and 3He exposure age dating to construct an eruption chronology for WVZ subglacial units. Late-glacial units, whose surfaces are relatively unmodified and show no evidence of subsequent glaciation, have low incompatible element concentrations (e.g., ~0.05 wt. % K2O at 8.0 wt. % MgO), low FeO* (~10.0 wt. % at 8.0 wt. % MgO), and high SiO2 and CaO concentrations (~49.0 wt. % and 14.0 wt. % at 8.0 wt. % MgO, respectively), while older table mountains whose surfaces that have been modified by glacial processes after formation have chemical compositions more comparable to average WVZ post-glacial units. Decreased levels of highly incompatible to moderately incompatible elements and elevated SiO2 and CaO concentrations are also found in fini-glacial eruption units, which experienced minimal amounts of ice interaction during formation. These geochemical characteristics are consistent with enhanced melting in the upper mantle, as predicted by models of deglaciation-induced mantle decompression. Detailed geologic and geochemical studies of post-glacial units along the WVZ show the eruptive response

  15. S-Isotope Fractionation between Fluid and Silicate Melts

    NASA Astrophysics Data System (ADS)

    Fiege, A.; Holtz, F.; Shimizu, N.; Behrens, H.; Mandeville, C. W.; Simon, A. C.

    2013-12-01

    Large amounts of sulfur (S) can be released from silicate melts during volcanic eruption. Degassing of magma can lead to S-isotope fractionation between fluid and melt. However, experimental data on fluid-melt S-isotope fractionation are scarce and no data exist for silicate melts at temperatures (T) > 1000°C. Recent advances in in situ S-isotope analyses using secondary ion mass spectroscopy (SIMS) enable determinations of the isotopic composition in silicate glasses with low S content [1] and allow us to investigate experimentally fluid-melt S-isotope fractionation effects in magmatic systems. Isothermal decompression experiments were conducted in internally heated pressure vessels (IHPV). Volatile-bearing (~3 to ~8 wt% H2O, 140 to 2700 ppm S, 0 to 1000 ppm Cl) andesitic and basaltic glasses were synthesized at ~1040°C, ~500 MPa and log(fO2) = QFM to QFM+4 (QFM: quartz-magnetite-fayalite buffer). The decompression experiments were carried out at T = 1030 to 1200°C and similar fO2. Pressure (P) was released continuously from ~400 MPa to 150, 100 or 70 MPa with rates (r) ranging from 0.001 to 0.2 MPa/s. The samples were either rapidly quenched after decompression or annealed for various times (tA) at final conditions (1 to 72 h) before quenching. The volatile-bearing starting glasses and the partially degassed experimental glasses were analyzed by electron microprobe (e.g. Cl-, S-content), IR-spectroscopy (H2O content) and SIMS (δ34S). The gas-melt isotope fractionation factors (αg-m) were estimated following Holloway and Blank [2] and utilizing mass balance calculations. The results show that αg-m remains constant within error over the investigated range of r and tA, reflecting fluid-melt equilibrium fractionation of S isotopes for given T and fO2. Data obtained for oxidizing conditions (~QFM+4) are in agreement with observations in arc magmas [3] and close to what is predicted by previous theoretical and experimental data [4; 5; 6]; e.g. a α(SO2 gas - SO42

  16. [A method for evaluating the safety of decompression regimens for divers].

    PubMed

    Volkov, L K; Voĭtsekhovich, I A; Liapin, V M; Miasnikov, A A

    1996-09-01

    The authors offer a way of estimation of safety modes of decompression, based on definition of intensity of venous gas embolism (VGE) at each decompression and account of probability of illness of divers in series of tests. Intensity of VGE was determined with the help of ultrasonic gas bubbles Doppler radar. Comparative safety of standard modes of decompression of divers of the Navy was estimated, and also the modes, designed in accordance with mathematical model of decompression, offered by I. A. Voĭtsekhovich (1990), were done. The results testify, that use of ultrasonic radar for estimation of intensity of VGE at decompression and account of average and maximum probability of decompression illness in series of tests of modes permit to receive the comparative characteristic of safety of modes at small number of decompressions.

  17. Generation of CO2-rich melts during basalt magma ascent and degassing

    NASA Astrophysics Data System (ADS)

    Pichavant, Michel; Di Carlo, Ida; Rotolo, Silvio G.; Scaillet, Bruno; Burgisser, Alain; Le Gall, Nolwenn; Martel, Caroline

    2013-08-01

    To test mechanisms of basaltic magma degassing, continuous decompressions of volatile-bearing (2.7-3.8 wt% H2O, 600-1,300 ppm CO2) Stromboli melts were performed from 250-200 to 50-25 MPa at 1,180-1,140 °C. Ascent rates were varied from 0.25 to ~1.5 m/s. Glasses after decompression show a wide range of textures, from totally bubble-free to bubble-rich, the latter with bubble number densities from 104 to 106 cm-3, similar to Stromboli pumices. Vesicularities range from 0 to ~20 vol%. Final melt H2O concentrations are homogeneous and always close to solubilities. In contrast, the rate of vesiculation controls the final melt CO2 concentration. High vesicularity charges have glass CO2 concentrations that follow theoretical equilibrium degassing paths, whereas glasses from low vesicularity charges show marked deviations from equilibrium, with CO2 concentrations up to one order of magnitude higher than solubilities. FTIR profiles and maps reveal glass CO2 concentration gradients near the gas-melt interface. Our results stress the importance of bubble nucleation and growth, and of volatile diffusivities, for basaltic melt degassing. Two characteristic distances, the gas interface distance (distance either between bubbles or to gas-melt interfaces) and the volatile diffusion distance, control the degassing process. Melts containing numerous and large bubbles have gas interface distances shorter than volatile diffusion distances, and degassing proceeds by equilibrium partitioning of CO2 and H2O between melt and gas bubbles. For melts where either bubble nucleation is inhibited or bubble growth is limited, gas interface distances are longer than volatile diffusion distances. Degassing proceeds by diffusive volatile transfer at the gas-melt interface and is kinetically limited by the diffusivities of volatiles in the melt. Our experiments show that CO2-oversaturated melts can be generated as a result of magma decompression. They provide a new explanation for the occurrence

  18. An experimental study of permeability development as a function of crystal-free melt viscosity

    NASA Astrophysics Data System (ADS)

    Lindoo, A.; Larsen, J. F.; Cashman, K. V.; Dunn, A. L.; Neill, O. K.

    2016-02-01

    Permeability development in magmas controls gas escape and, as a consequence, modulates eruptive activity. To date, there are few experimental controls on bubble growth and permeability development, particularly in low viscosity melts. To address this knowledge gap, we have run controlled decompression experiments on crystal-free rhyolite (76 wt.% SiO2), rhyodacite (70 wt.% SiO2), K-phonolite (55 wt.% SiO2) and basaltic andesite (54 wt.% SiO2) melts. This suite of experiments allows us to examine controls on the critical porosity at which vesiculating melts become permeable. As starting materials we used both fine powders and solid slabs of pumice, obsidian and annealed starting materials with viscosities of ∼102 to ∼106 Pas. We saturated the experiments with water at 900° (rhyolite, rhyodacite, and phonolite) and 1025 °C (basaltic andesite) at 150 MPa for 2-72 hrs and decompressed samples isothermally to final pressures of 125 to 10 MPa at rates of 0.25-4.11 MPa/s. Sample porosity was calculated from reflected light images of polished charges and permeability was measured using a bench-top gas permeameter and application of the Forchheimer equation to estimate both viscous (k1) and inertial (k2) permeabilities. Degassing conditions were assessed by measuring dissolved water contents using micro-Fourier-Transform Infrared (μ-FTIR) techniques. All experiment charges are impermeable below a critical porosity (ϕc) that varies among melt compositions. For experiments decompressed at 0.25 MPa/s, we find the percolation threshold for rhyolite is 68.3 ± 2.2 vol.%; for rhyodacite is 77.3 ± 3.8 vol.%; and for K-phonolite is 75.6 ± 1.9 vol.%. Rhyolite decompressed at 3-4 MPa/s has a percolation threshold of 74 ± 1.8 vol.%. These results are similar to previous experiments on silicic melts and to high permeability thresholds inferred for silicic pumice. All basaltic andesite melts decompressed at 0.25 MPa/s, in contrast, have permeabilities below the detection

  19. Petrological Constraints on Melt Generation Beneath the Asal Rift (Djibouti)

    NASA Astrophysics Data System (ADS)

    Pinzuti, P.; Humler, E.; Manighetti, I.; Gaudemer, Y.; Bézos, A.

    2010-12-01

    The temporal evolution of the mantle melting processes in the Asal Rift is evaluated from the chemical composition of 95 lava flows sampled along 10 km of the rift axis and 8 km off-axis (that is for the last 650 ky). The major element composition and the trace element ratios of aphyric basalts across the Asal Rift show a symmetric pattern relative to the rift axis and preserved a clear signal of mantle melting depth variations. FeO, Fe8.0, Sm/YbN and Zr/Y increase, whereas SiO2 and Lu/HfN decrease from the rift axis to the rift shoulders. These variations are qualitatively consistent with a shallower melting beneath the rift axis than off-axis and the data show that the melting regime is inconsistent with a passive upwelling model. In order to quantify the depth range and extent of melting, we invert Na8.0 and Fe8.0 contents of basalts based on a pure active upwelling model. Beneath the rift axis, melting paths are shallow, from 60 to 30 km. These melting paths are consistent with adiabatic melting in normal-temperature asthenosphere, beneath an extensively thinned mantle lithosphere. In contrast, melting on the rift shoulders occurred beneath a thick mantle lithosphere and required mantle solidus temperature 180°C hotter than normal (melting paths from 110 to 75 km). The calculated rate of lithospheric thinning is high (6.0 cm yr-1) and could explain the survival of a metastable garnet within the mantle at depth shallower than 90 km beneath the modern Asal Rift.

  20. On diver thermal status and susceptibility to decompression sickness.

    PubMed

    Gerth, Wayne A

    2015-09-01

    In a recent Letter to the Editor, Clarke, et al, indicated that divers who deliberately chill themselves on a dive to reduce risk of decompression sickness (DCS) may be misinterpreting our 2007 Navy Experimental Diving Unit (NEDU) report. Indeed, we did not advocate that divers should risk hypothermia on bottom to reduce risk of DCS, nor do we dispute the authors' overall admonition to avoid diving cold unnecessarily. However, Clarke, et al, imply more generally that results of our study are not applicable to recreational or technical divers because the dives we tested were atypical of dives undertaken by such divers. We wish to clarify that our study does have implications for recreational and technical divers, implications that should not be ignored. The dives we tested were not intended to be typical of dives undertaken in any actual operational context. Instead, we chose to expose divers to temperatures at the extremes of their thermal tolerance in order to ensure that effects of diver thermal status on DCS susceptibility would be found if such effects existed. Our initial test dive profile provided appreciable time both on bottom and during decompression to allow any differential thermal effects during these two dive phases to manifest, while affording a baseline risk of DCS that could be altered by thermal effects without exposing subjects to inordinately high risks of DCS. Our results strongly indicate that the optimal diver thermal conditions for mitigation of DCS risk or minimization of decompression time entail remaining cool during gas uptake phases of a dive and warm during off-gassing phases. While the dose-response characteristics of our observed thermal effects are almost certainly non-linear in both exposure temperature and duration, it is only reasonable to presume that the effects vary monotonically with these factors. We have no reason to presume that such responses and effects under less extreme conditions would be in directions opposite to

  1. Decompression Sickness during Construction of the Dartford Tunnel

    PubMed Central

    Golding, F. Campbell; Griffiths, P.; Hempleman, H. V.; Paton, W. D. M.; Walder, D. N.

    1960-01-01

    A clinical, radiological and statistical survey has been made of decompression sickness during the construction of the Dartford Tunnel. Over a period of two years, 1,200 men were employed on eight-hour shifts at pressures up to 28 pounds per square inch (p.s.i.). There were 689 cases of decompression sickness out of 122,000 compressions, an incidence of 0·56%. The majority of cases (94·9%) were simple “bends”. The remainder (5·1%) exhibited signs and symptoms other than pain and were more serious. All cases were successfully treated and no fatality or permanent disability occurred. In two serious cases, cysts in the lungs were discovered. It is suggested that these gave rise to air embolism when the subjects were decompressed, and pulmonary changes may contribute more than hitherto believed to the pathogenesis of bends. Some other clinical features are described, including “skin-mottling” and an association between bends and the site of an injury. The bends rate is higher for the back shift (3 p.m. to 11 p.m.) and the night shift (11 p.m. to 7 a.m.) than for the day shift. In the treatment of decompression sickness it appears to be more satisfactory to use the minimum pressure required for relief of symptoms followed by slow decompression with occasional “soaks”, than to attempt to drive the causative bubbles into solution with high pressures. During the contract the decompression tables recently prescribed by the Ministry of Labour were used. Evidence was obtained that they could be made safer, and that the two main assumptions on which they are based (that sickness will not occur at pressures below 18 p.s.i., and that a man saturates in four hours) may be incorrect. It is desirable to test tables based on 15 p.s.i. and eight-hour saturation. The existence of acclimatization to pressure was confirmed; it is such that the bends rate may fall in two to three weeks to 0·1% of the incidence on the first day of exposure. Acclimatization is lost again

  2. Risk of decompression sickness in the presence of circulating microbubbles

    NASA Technical Reports Server (NTRS)

    Kumar, K. Vasantha; Powell, Michael R.

    1993-01-01

    In this study, we examined the association between microbubbles formed in the circulation from a free gas phase and symptoms of altitude decompression sickness (DCS). In a subgroup of 59 males of mean (S.D) age 31.2 (5.8) years who developed microbubbles during exposure to 26.59 kPa (4.3 psi) under simulated extravehicular activities (EVA), symptoms of DCS occurred in 24 (41 percent) individuals. Spencer grade 1 microbubbles occurred in 4 (7 percent), grade 2 in 9 (15 percent), grade 3 in 15 (25 percent), and grade 4 in 31 (53 percent) of subjects. Survival analysis using Cox proportional hazards regression showed that individuals with less than grade 3 CMB showed 2.46 times (95 percent confidence interval = 1.26 to 5.34) higher risk of symptoms. This information is crucial for defining the risk of DCS for inflight Doppler monitoring under space EVA. Altitude decompression sickness (DCS) occurs when there is acute reduction in ambient pressure. The symptoms of DCS are due to the formation of a free gas phase (in the form of gas microbubbles) in tissues during decompression. Musculo-skeletal pain of bends is the commonest form of DCS in altitude exposures. In the space flight environment, there is a risk of DCS when astronauts decompress from the normobaric shuttle pressure into the hypobaric space suit pressure (currently about 29.65 kPa (4.3 psi) for extra-vehicular activities (EVA). This risk is counterbalanced by a judicious combination of prior denitrogenation and staged decompression. Studies of DCS are limited by the duration of the test at reduced pressure. Since only a proportion of subjects tested develop symptoms, the information on DCS is generally incomplete or 'censored'. Many studies employ Doppler ultrasound monitoring of the precordial area for detecting circulating microbubbles (CMB). Although the association between CMB and bends pain is not causal, CMB are frequently monitored during decompression. In this paper, we examine the association

  3. On the General Class of Models of Adiabatic Evolution

    NASA Astrophysics Data System (ADS)

    Sun, Jie; Lu, Songfeng; Liu, Fang

    2016-10-01

    The general class of models of adiabatic evolution was proposed to speed up the usual adiabatic computation in the case of quantum search problem. It was shown [8] that, by temporarily increasing the ground state energy of a time-dependent Hamiltonian to a suitable quantity, the quantum computation can perform the calculation in time complexity O(1). But it is also known that if the overlap between the initial and final states of the system is zero, then the computation based on the generalized models of adiabatic evolution can break down completely. In this paper, we find another severe limitation for this class of adiabatic evolution-based algorithms, which should be taken into account in applications. That is, it is still possible that this kind of evolution designed to deal with the quantum search problem fails completely if the interpolating paths in the system Hamiltonian are chosen inappropriately, while the usual adiabatic evolutions can do the same job relatively effectively. This implies that it is not always recommendable to use nonlinear paths in adiabatic computation. On the contrary, the usual simple adiabatic evolution may be sufficient for effective use.

  4. Effects of EOS adiabat on hot spot dynamics

    NASA Astrophysics Data System (ADS)

    Cheng, Baolian; Kwan, Thomas; Wang, Yi-Ming; Batha, Steven

    2013-10-01

    Equation of state (EOS) and adiabat of the pusher play significant roles in the dynamics and formation of the hot spot of an ignition capsule. For given imploding energy, they uniquely determine the partition of internal energy, mass, and volume between the pusher and the hot spot. In this work, we apply the new scaling laws recently derived by Cheng et al. to the National Ignition Campaign (NIC) ignition capsules and study the impacts of EOS and adiabat of the pusher on the hot spot dynamics by using the EOS adiabat index as an adjustable model parameter. We compare our analysis with the NIC data, specifically, for shots N120321 and N120205, and with the numerical simulations of these shots. The predictions from our theoretical model are in good agreements with the NIC data when a hot adiabat was used for the pusher, and with code simulations when a cold adiabat was used for the pusher. Our analysis indicates that the actual adiabat of the pusher in NIC experiments may well be higher than the adiabat assumed in the simulations. This analysis provides a physical and systematic explanation to the ongoing disagreements between the NIC experimental results and the multi-dimensional numerical simulations. This work was performed under the auspices of the U.S. Department of Energy by the Los Alamos National Laboratory under contract number W-7405-ENG-36.

  5. Non-adiabatic perturbations in Ricci dark energy model

    SciTech Connect

    Karwan, Khamphee; Thitapura, Thiti E-mail: nanodsci2523@hotmail.com

    2012-01-01

    We show that the non-adiabatic perturbations between Ricci dark energy and matter can grow both on superhorizon and subhorizon scales, and these non-adiabatic perturbations on subhorizon scales can lead to instability in this dark energy model. The rapidly growing non-adiabatic modes on subhorizon scales always occur when the equation of state parameter of dark energy starts to drop towards -1 near the end of matter era, except that the parameter α of Ricci dark energy equals to 1/2. In the case where α = 1/2, the rapidly growing non-adiabatic modes disappear when the perturbations in dark energy and matter are adiabatic initially. However, an adiabaticity between dark energy and matter perturbations at early time implies a non-adiabaticity between matter and radiation, this can influence the ordinary Sachs-Wolfe (OSW) effect. Since the amount of Ricci dark energy is not small during matter domination, the integrated Sachs-Wolfe (ISW) effect is greatly modified by density perturbations of dark energy, leading to a wrong shape of CMB power spectrum. The instability in Ricci dark energy is difficult to be alleviated if the effects of coupling between baryon and photon on dark energy perturbations are included.

  6. Melting of the precipitated ice IV in LiCl aqueous solution and polyamorphism of water.

    PubMed

    Mishima, Osamu

    2011-12-08

    Melting of the precipitated ice IV in supercooled LiCl-H(2)O solution was studied in the range of 0-0.6 MPa and 160-270 K. Emulsified solution was used to detect this metastable transition. Ice IV was precipitated from the aqueous solution of 2.0 mol % LiCl (or 4.8 mol % LiCl) in each emulsion particle at low-temperature and high-pressure conditions, and the emulsion was decompressed at different temperatures. The melting of ice IV was detected from the temperature change of the emulsified sample during the decompression. There was an apparently sudden change in the slope of the ice IV melting curve (liquidus) in the pressure-temperature diagram. At the high-pressure and high-temperature side of the change, the solute-induced freezing point depression was observed. At the low-pressure and low-temperature side, ice IV transformed into ice Ih on the decompression, and the transition was almost unrelated to the concentration of LiCl. These experimental results were roughly explained by the presumed existence of two kinds of liquid water (low-density liquid water and high-density liquid water), or polyamorphism in water, and by the simple assumption that LiCl dissolved maily in high-density liquid water.

  7. Dynamics of Charged Particles in an Adiabatic Thermal Beam Equilibrium

    NASA Astrophysics Data System (ADS)

    Chen, Chiping; Wei, Haofei

    2010-11-01

    Charged-particle motion is studied in the self-electric and self-magnetic fields of a well-matched, intense charged-particle beam and an applied periodic solenoidal magnetic focusing field. The beam is assumed to be in a state of adiabatic thermal equilibrium. The phase space is analyzed and compared with that of the well-known Kapchinskij-Vladimirskij (KV)-type beam equilibrium. It is found that the widths of nonlinear resonances in the adiabatic thermal beam equilibrium are narrower than those in the KV-type beam equilibrium. Numerical evidence is presented, indicating almost complete elimination of chaotic particle motion in the adiabatic thermal beam equilibrium.

  8. Bayesian approach to decompression sickness model parameter estimation.

    PubMed

    Howle, L E; Weber, P W; Nichols, J M

    2017-03-01

    We examine both maximum likelihood and Bayesian approaches for estimating probabilistic decompression sickness model parameters. Maximum likelihood estimation treats parameters as fixed values and determines the best estimate through repeated trials, whereas the Bayesian approach treats parameters as random variables and determines the parameter probability distributions. We would ultimately like to know the probability that a parameter lies in a certain range rather than simply make statements about the repeatability of our estimator. Although both represent powerful methods of inference, for models with complex or multi-peaked likelihoods, maximum likelihood parameter estimates can prove more difficult to interpret than the estimates of the parameter distributions provided by the Bayesian approach. For models of decompression sickness, we show that while these two estimation methods are complementary, the credible intervals generated by the Bayesian approach are more naturally suited to quantifying uncertainty in the model parameters.

  9. Report on computation of repetitive hyperbaric-hypobaric decompression tables

    NASA Technical Reports Server (NTRS)

    Edel, P. O.

    1975-01-01

    The tables were constructed specifically for NASA's simulated weightlessness training program; they provide for 8 depth ranges covering depths from 7 to 47 FSW, with exposure times of 15 to 360 minutes. These tables were based up on an 8 compartment model using tissue half-time values of 5 to 360 minutes and Workmanline M-values for control of the decompression obligation resulting from hyperbaric exposures. Supersaturation ratios of 1.55:1 to 2:1 were used for control of ascents to altitude following such repetitive dives. Adequacy of the method and the resultant tables were determined in light of past experience with decompression involving hyperbaric-hypobaric interfaces in human exposures. Using these criteria, the method showed conformity with empirically determined values. In areas where a discrepancy existed, the tables would err in the direction of safety.

  10. Acute obstructive hydrocephalus complicating decompression surgery of the craniovertebral junction

    PubMed Central

    Ohya, Junichi; Chikuda, Hirotaka; Nakatomi, Hirofumi; Sakamoto, Ryuji; Saito, Nobuhito; Tanaka, Sakae

    2016-01-01

    Obstructive hydrocephalus has been described as a rare complication following foramen magnum decompression for Chiari malformation. However, there are few reports of obstructive hydrocephalus after spinal surgery for other pathologies of the craniovertebral junction (CVJ). The authors herein report a 52-year-old female with achondroplasia presenting with an 8-month history of myelopathy due to spinal cord compression at CVJ. She underwent resection of the C1 posterior arch and part of the edge of the occipital bone. A computed tomography (CT) scan obtained 1-week after the surgery revealed bilateral infratentorial fluid collection. The patient was first managed conservatively; however, on the 17th day, her consciousness level showed sudden deterioration. Emergency CT demonstrated marked hydrocephalus due to obstruction of the cerebral aqueduct. Acute obstructive hydrocephalus can occur late after decompression surgery at the CVJ, and thus should be included in the differential diagnosis of a deteriorating mental status. PMID:27366268

  11. Predictive modeling of altitude decompression sickness in humans

    NASA Technical Reports Server (NTRS)

    Kenyon, D. J.; Hamilton, R. W., Jr.; Colley, I. A.; Schreiner, H. R.

    1972-01-01

    The coding of data on 2,565 individual human altitude chamber tests is reported as part of a selection procedure designed to eliminate individuals who are highly susceptible to decompression sickness, individual aircrew members were exposed to the pressure equivalent of 37,000 feet and observed for one hour. Many entries refer to subjects who have been tested two or three times. This data contains a substantial body of statistical information important to the understanding of the mechanisms of altitude decompression sickness and for the computation of improved high altitude operating procedures. Appropriate computer formats and encoding procedures were developed and all 2,565 entries have been converted to these formats and stored on magnetic tape. A gas loading file was produced.

  12. The behavior of Fe3+/∑Fe during partial melting of spinel lherzolite

    NASA Astrophysics Data System (ADS)

    Gaetani, Glenn A.

    2016-07-01

    This study presents an internally consistent model for the behavior of Fe3+/∑Fe during partial melting of spinel lherzolite. The Fe3+/∑Fe ratio for olivine is calculated on the basis of point defect thermodynamics, and the oxidation states of iron in the other solid phases are calculated using Fe3+/Fe2+ distribution between olivine and orthopyroxene, clinopyroxene, or spinel. Conservation of mass is used to relate the Fe3+/Fe2+ ratio of partial melt to the concentrations of Fe3+ and Fe2+ in the initial and residual solids as a function of pressure, temperature, and oxygen fugacity. Results from isobaric batch melting calculations demonstrate that the Fe3+/∑Fe ratio of the partial melt decreases with increasing melt fraction. Conversely, the Fe3+/∑Fe ratio of the partial melt increases with increasing melt fraction during decompression batch melting. The relative oxygen fugacity of the upper mantle depends on both the oxidation state of iron and mantle potential temperature. Results from incremental decompression melting calculations in which 1% melt is produced for each 100 MPa of decompression and then removed from the residual solid indicate that relative oxygen fugacity calculated from the oxidation state of iron in basaltic glass does not represent a unique value for the oceanic upper mantle but, rather, reflects conditions in the lower portion of the melting regime. A 100 °C change in mantle potential temperature produces a change in relative oxygen fugacity of ∼0.8 log units, similar to the global range inferred from mid-ocean ridge basalt glasses. It is necessary, therefore, to compare relative oxygen fugacity calculated from basaltic glass with proxies for potential temperature before drawing conclusions on heterogeneity of the oxidation state of iron in the oceanic upper mantle. Results from model calculations also suggest that the sub-arc mantle is intrinsically more oxidizing than the oceanic mantle because it is cooler. The global correlation

  13. On-the-Fly Decompression and Rendering of Multiresolution Terrain

    SciTech Connect

    Lindstrom, P; Cohen, J D

    2009-04-02

    We present a streaming geometry compression codec for multiresolution, uniformly-gridded, triangular terrain patches that supports very fast decompression. Our method is based on linear prediction and residual coding for lossless compression of the full-resolution data. As simplified patches on coarser levels in the hierarchy already incur some data loss, we optionally allow further quantization for more lossy compression. The quantization levels are adaptive on a per-patch basis, while still permitting seamless, adaptive tessellations of the terrain. Our geometry compression on such a hierarchy achieves compression ratios of 3:1 to 12:1. Our scheme is not only suitable for fast decompression on the CPU, but also for parallel decoding on the GPU with peak throughput over 2 billion triangles per second. Each terrain patch is independently decompressed on the fly from a variable-rate bitstream by a GPU geometry program with no branches or conditionals. Thus we can store the geometry compressed on the GPU, reducing storage and bandwidth requirements throughout the system. In our rendering approach, only compressed bitstreams and the decoded height values in the view-dependent 'cut' are explicitly stored on the GPU. Normal vectors are computed in a streaming fashion, and remaining geometry and texture coordinates, as well as mesh connectivity, are shared and re-used for all patches. We demonstrate and evaluate our algorithms on a small prototype system in which all compressed geometry fits in the GPU memory and decompression occurs on the fly every rendering frame without any cache maintenance.

  14. The Possible Relationship Between Patent Foramen Ovale and Decompression Sickness:.

    DTIC Science & Technology

    1999-01-01

    a potential conduit for blood clot (resulting in a stroke), or venous gas bubbles during decompression, (resulting in type II neurologic...Despite the high prevalence of PFO in the general population, and the relatively common occurrence of venous gas bubbles in diving and altitude exposures...being present in up to a third of the population. The potential for right- to-left shunting of venous gas emboli (VGE) which are known to occur in even

  15. Rapid decompression of congenital hydrocephalus associated with parenchymal hemorrhage.

    PubMed

    Bass, T; White, L E; Wood, R D; Werner, A L; Schinco, F P

    1995-10-01

    A newborn boy with congenital hydrocephalus was diagnosed with aqueductal stenosis using magnetic resonance imaging. Low-resistance ventriculoperitoneal shunt placement was followed by clinical deterioration. Repeat imaging studies revealed a collapsed cortical mantle with subdural hemorrhage. In addition to subdural blood, often associated with marked cerebral conformational changes, extensive intraparenchymal hemorrhage was seen. For extreme congenital hydrocephalus, ventriculoperitoneal shunts with greater resistance to flow than the currently used neonatal shunt devices may be indicated, to allow a more gradual ventricular decompression.

  16. Sidenafil Pre-Treatment Promotes Decompression Sickness in Rats

    PubMed Central

    Blatteau, Jean-Eric; Brubakk, Alf O.; Gempp, Emmanuel; Castagna, Olivier; Risso, Jean-Jacques; Vallée, Nicolas

    2013-01-01

    Vascular bubble formation after decompression contributes to endothelial injuries which form the basis for the development of decompression sickness (DCS). Nitric oxide (NO) is a powerful vasodilator that contributes to vessel homeostasis. It has been shown that NO-releasing agent may reduce bubble formation and prevent serious decompression sickness. The use of sildenafil, a well-known, phosphodiesterase-5 blocker, which act by potentiating the vasodilatory effect on smooth muscle relaxation, has never been studied in DCS. The purpose of the present study was to evaluate the clinical effects of sildenafil pre-treatment on DCS in a rat model. 67 rats were subjected to a simulated dive at 90 msw for 45 min before staged decompression. The experimental group received 10 mg/kg of sildenafil one hour before exposure (n = 35) while controls were not treated (n = 32). Clinical assessment took place over a period of 30 min after surfacing. At the end, blood samples were collected for blood cells counts and the level of circulating bubbles in the right cavities was quantified. There were significantly more manifestations of DCS in the sildenafil group than in the controls (34.3% vs 6.25%, respectively, p = 0.012). Platelet count was more reduced in treated rats than in controls (−21.7% vs −7%, respectively, p = 0.029), whereas bubble grades did not differ between groups. We concluded that pre-treatment with sildenafil promotes the onset and severity of neurological DCS. When considering the use of phosphodiesterase-5 blockers in the context of diving, careful discussion with physician should be recommended. PMID:23580342

  17. 29 CFR Appendix A to Subpart S of... - Decompression Tables

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 8 2010-07-01 2010-07-01 false Decompression Tables A Appendix A to Subpart S of Part 1926..., Caissons, Cofferdams and Compressed Air Pt. 1926, Subpt. S, App. A Appendix A to Subpart S of Part 1926... pressure p.s.i.g. Working period hours 1/2 1 11/2 2 3 4 5 6 7 8 Over 8 9 to 12 3 3 3 3 3 3 3 3 3 3 3 14 6...

  18. Decompressive hemicraniectomy in supra-tentorial malignant infarcts

    PubMed Central

    Nizami, Furqan A.; Ramzan, Altaf U.; Wani, Abrar A.; Wani, Mushtaq A.; Malik, Nayil K.; Shah, Pervaiz A.; Asimi, Ravouf

    2012-01-01

    Background: Decompressive hemicraniectomy not only reduces the intracranial pressure but has been demonstrated to increase survival and decrease the morbidity in patients with supratentorial malignant brain infarcts (STMBI). The aim of this study was to assess the efficacy of surgical decompression to decrease the mortality and morbidity in patients with STMBI refractory to medical therapy and to compare the results with those of the medically managed patients. Methods: All the 24 consecutive patients with clinical and radiological diagnosis of STMBI, refractory to medical management in 2 years, were included. Option of surgical decompression after explaining the outcome, risk and benefits of the procedure was given to the attendants/relatives of all patients who were fulfilling the inclusion criteria. The patient group, whose attendants/relatives were not willing to undergo surgery, were subjected to the same medical therapy and they were taken as the “control group.” Results: Supratentorial malignant infarcts were more common in the age group of 41–60 years. Mean age of presentation was 42.16 ± 16.2 years and the mean GCS on admission was 7.83 ± 2.1. Mortality was 16.7% in the surgically and 25.0% in the medically managed group. Patients operated early (<48 h), age ≤60 years, midline shift <5 mm and size of infarct less than 2/3rd of the vascular territory involved showed good prognosis. The functional outcome revealed by modified Rankin Score (mRS) and Glasgow Outcome Score (GOS) was better in surgically managed patients. Results of the Zung Self-Rating Depression Score were better in surgically managed patients at 1 year. Barthal Index in the surgically managed group showed statistically significant results. Conclusions: Decompressive hemicraniectomy with duroplasty if performed early in STMBI not only decreases the mortality but also increases the functional outcome when compared with patients who were managed conservatively with medical therapy only

  19. Emergency decompressive craniectomy after removal of convexity meningiomas

    PubMed Central

    Missori, Paolo; Domenicucci, Maurizio; Paolini, Sergio; Mancarella, Cristina; Tola, Serena; D’Elia, Alessandro; Marotta, Nicola; Seferi, Arsen; Esposito, Vincenzo

    2016-01-01

    Background: Convexity meningiomas are benign brain tumors that are amenable to complete surgical resection and are associated with a low complication rate. The aim of this study was to identify factors that result in acute postoperative neurological worsening after the removal of convexity meningiomas. Methods: Clinical evaluation and neuroradiological analysis of patients who underwent removal of a supratentorial convexity meningioma were reviewed. Patients were selected when their postoperative course was complicated by acute neurological deterioration requiring decompressive craniectomy. Results: Six patients (mean age: 43.3 years) underwent surgical removal of a supratentorial convexity meningioma. Brain shift (mean: 9.9 mm) was evident on preoperative imaging due to lesions of varying size and perilesional edema. At various times postoperatively, patient consciousness worsened (up to decerebrate posture) with contralateral paresis and pupillary anisocoria. Computed tomography revealed no postoperative hematoma, however, did indicate increased brain edema and ventricular shift (mean: 12 mm). Emergency decompressive craniectomy and brief ventilator assistance were performed in all patients. Ischemia of the ipsilateral posterior cerebral artery occurred in 3 patients and hydrocephalus occurred in 2 patients. Outcome was good in 2, fair in 2, 1 patient had severe disability, and 1 patient died after 8 months. Conclusions: Brain shift on preoperative imaging is a substantial risk factor for postoperative neurological worsening in young adult patients after the removal of convexity meningiomas. Emergency decompressive craniectomy must be considered because it is effective in most cases. Other than consciousness impairment, there is no reliable clinical landmark to guide the decision to perform decompressive craniectomy; however, brain ischemia may have already occurred. PMID:27857859

  20. Hemimasticatory spasm treated with microvascular decompression of the trigeminal nerve.

    PubMed

    Chon, Kyu-Hyon; Lee, Jong-Myong; Koh, Eun-Jeong; Choi, Ha-Young

    2012-09-01

    Hemimasticatory spasm is a very rare disorder of the trigeminal nerve characterized by paroxysmal involuntary contraction of the jaw-closing muscles. The mechanisms leading to hemimasticatory spasm are still unclear. Recently, injection of botulinum toxin has become the treatment of choice due to its excellent results. We report a case of a successful treatment of hemimasticatory spasm via microvascular decompression of the motor branch of the trigeminal nerve.

  1. A new tube for simultaneous gastric decompression and jejunal alimentation.

    PubMed

    Nelson, R; Nyhus, L M

    1985-04-01

    A new tube has been devised for simultaneous gastric decompression and jejunal enteral alimentation. The tube is inserted by the nasogastric route intraoperatively. What differentiates this from earlier tubes is the addition of two inflatable balloons that facilitate passage of the tip of the tube through the retroperitoneal duodenum and into the proximal jejunum. Such a device is needed because the advantages of enteral alimentation in the postoperative patient include safety, low cost and significant metabolic benefits.

  2. Melt containment member

    SciTech Connect

    Rieken, Joel R.; Heidloff, Andrew J.

    2014-09-09

    A tubular melt containment member for transient containment of molten metals and alloys, especially reactive metals and alloys, includes a melt-contacting layer or region that comprises an oxygen-deficient rare earth oxide material that is less reactive as compared to the counterpart stoichiometric rare earth oxide. The oxygen-deficient (sub-stoichiometric) rare earth oxide can comprise oxygen-deficient yttria represented by Y.sub.2O.sub.3-x wherein x is from 0.01 to 0.1. Use of the oxygen-deficient rare earth oxide as the melt-contacting layer or region material reduces reaction with the melt for a given melt temperature and melt contact time.

  3. Quantum adiabatic optimization and combinatorial landscapes

    NASA Astrophysics Data System (ADS)

    Smelyanskiy, V. N.; Knysh, S.; Morris, R. D.

    2004-09-01

    In this paper we analyze the performance of the Quantum Adiabatic Evolution algorithm on a variant of the satisfiability problem for an ensemble of random graphs parametrized by the ratio of clauses to variables, γ=M/N . We introduce a set of macroscopic parameters (landscapes) and put forward an ansatz of universality for random bit flips. We then formulate the problem of finding the smallest eigenvalue and the excitation gap as a statistical mechanics problem. We use the so-called annealing approximation with a refinement that a finite set of macroscopic variables (instead of only energy) is used, and are able to show the existence of a dynamic threshold γ=γd starting with some value of K —the number of variables in each clause. Beyond the dynamic threshold, the algorithm should take an exponentially long time to find a solution. We compare the results for extended and simplified sets of landscapes and provide numerical evidence in support of our universality ansatz. We have been able to map the ensemble of random graphs onto another ensemble with fluctuations significantly reduced. This enabled us to obtain tight upper bounds on the satisfiability transition and to recompute the dynamical transition using the extended set of landscapes.

  4. Design of the PIXIE adiabatic demagnetization refrigerators

    NASA Astrophysics Data System (ADS)

    Shirron, Peter J.; Kimball, Mark O.; Fixsen, Dale J.; Kogut, Alan J.; Li, Xiaoyi; DiPirro, Michael J.

    2012-04-01

    The Primordial Inflation Explorer (PIXIE) is a proposed mission to densely map the polarization of the cosmic microwave background. It will operate in a scanning mode from a sun-synchronous orbit, using low temperature detectors (at 0.1 K) and located inside a telescope that is cooled to approximately 2.73 K - to match the background temperature. A mechanical cryocooler operating at 4.5 K establishes a low base temperature from which two adiabatic demagnetization refrigerator (ADR) assemblies will cool the telescope and detectors. To achieve continuous scanning capability, the ADRs must operate continuously. Complicating the design are two factors: (1) the need to systematically vary the temperature of various telescope components in order to separate the small polarization signal variations from those that may arise from temperature drifts and changing gradients within the telescope, and (2) the orbital and monthly variations in lunar irradiance into the telescope barrels. These factors require the telescope ADR to reject quasi-continuous heat loads of 2-3 mW, while maintaining a peak heat reject rate of less than 12 mW. The detector heat load at 0.1 K is comparatively small at 1-2 μW. This paper will describe the 3-stage and 2-stage continuous ADRs that will be used to meet the cooling power and temperature stability requirements of the PIXIE detectors and telescope.

  5. Adiabatic quantum algorithm for search engine ranking.

    PubMed

    Garnerone, Silvano; Zanardi, Paolo; Lidar, Daniel A

    2012-06-08

    We propose an adiabatic quantum algorithm for generating a quantum pure state encoding of the PageRank vector, the most widely used tool in ranking the relative importance of internet pages. We present extensive numerical simulations which provide evidence that this algorithm can prepare the quantum PageRank state in a time which, on average, scales polylogarithmically in the number of web pages. We argue that the main topological feature of the underlying web graph allowing for such a scaling is the out-degree distribution. The top-ranked log(n) entries of the quantum PageRank state can then be estimated with a polynomial quantum speed-up. Moreover, the quantum PageRank state can be used in "q-sampling" protocols for testing properties of distributions, which require exponentially fewer measurements than all classical schemes designed for the same task. This can be used to decide whether to run a classical update of the PageRank.

  6. Adiabatic Quantum Algorithm for Search Engine Ranking

    NASA Astrophysics Data System (ADS)

    Garnerone, Silvano; Zanardi, Paolo; Lidar, Daniel A.

    2012-06-01

    We propose an adiabatic quantum algorithm for generating a quantum pure state encoding of the PageRank vector, the most widely used tool in ranking the relative importance of internet pages. We present extensive numerical simulations which provide evidence that this algorithm can prepare the quantum PageRank state in a time which, on average, scales polylogarithmically in the number of web pages. We argue that the main topological feature of the underlying web graph allowing for such a scaling is the out-degree distribution. The top-ranked log⁡(n) entries of the quantum PageRank state can then be estimated with a polynomial quantum speed-up. Moreover, the quantum PageRank state can be used in “q-sampling” protocols for testing properties of distributions, which require exponentially fewer measurements than all classical schemes designed for the same task. This can be used to decide whether to run a classical update of the PageRank.

  7. On the persistence of adiabatic shear bands

    NASA Astrophysics Data System (ADS)

    Boakye-Yiadom, S.; Bassim, M. N.; Al-Ameeri, S.

    2012-08-01

    It is generally agreed that the initiation and development of adiabatic shear bands (ASBs) are manifestations of damage in metallic materials subjected to high strain rates and large strains as those due to impact in a Hopkinson Bar system. Models for evolution of these bands have been described in the literature. One question that has not received attention is how persistent these bands are and whether their presence and effect can be reversed or eliminated by using a process of thermal (heat treatment) or thermo-mechanical treatment that would relieve the material from the high strain associated with ASBs and their role as precursors to crack initiation and subsequent failure. Since ASBs are more prevalent and more defined in BCC metals including steels, a study was conducted to investigate the best conditions of generating ASBs in a heat treatable steel, followed by determining the best conditions for heat treatment of specimens already damaged by the presence of ASBs in order to relieve the strains due to ASBs and restore the material to an apparent microstructure without the "scars" due to the previous presence of ASBs. It was found that heat treatment achieves the curing from ASBs. This presentation documents the process undertaken to achieve this objective.

  8. Adiabatic Spin Pumping with Quantum Dots

    NASA Astrophysics Data System (ADS)

    Mucciolo, Eduardo R.

    Electronic transport in mesoscopic systems has been intensively studied for more the last three decades. While there is a substantial understanding of the stationary regime, much less is know about phase-coherent nonequilibrium transport when pulses or ac perturbations are used to drive electrons at low temperatures and at small length scales. However, about 20 years ago Thouless proposed to drive nondissipative currents in quantum systems by applying simultaneously two phase-locked external perturbations. The so-called adiabatic pumping mechanism has been revived in the last few years, both theoretically and experimentally, in part because of the development of lateral semiconductor quantum dots. Here we will explain how open dots can be used to create spin-polarized currents with little or no net charge transfer. The pure spin pump we propose is the analog of a charge battery in conventional electronics and may provide a needed circuit element for spin-based electronics. We will also discuss other relevant issues such as rectification and decoherence and point out possible extensions of the mechanism to closed dots.

  9. Empirical relationships of homogeneous bubble nucleation, growth and coalescence in rhyolitic melt

    NASA Astrophysics Data System (ADS)

    Giachetti, T.; Gonnermann, H. M.; Gardner, J. E.; Truong, N.; Toledo, P.; Hajimirza, S.

    2015-12-01

    Decompression experiments of homogeneous nucleation, growth and coalescence of bubbles in rhyolitic melt provide new data for an empirical formulation to predict bubble number density and size from controlled experimental conditions. Samples were hydrated at 200-250 MPa and 850 °C to water contents of 5.4-6.0 wt%, followed by decompression at rates of 60-150 MPa.s-1. Samples were held at final pressures for 6-90 s, allowing for bubble growth and coalescence after decompression and nucleation. Scanning electron microscopic (SEM) images and computed tomography (CT) scans of the decompressed glasses were analyzed for size distributions of both isolated and coalesced bubbles separately. Sample porosities vary from 4% to 63%, and connected porosity is positively correlated with total porosity for samples where it is greater than approximately 35%. A steep increase in the proportion of connected bubbles is observed once the average bubble wall thickness becomes lower than approximately 2 μm. In combination with SEM, CT and bubble size distributions these results indicate that bubble coalescence is independent of bubble size. Bubble number density varies from 8.9×1011 m-3 to 4.4×1016 m-3 (melt-referenced), and is positively correlated with the degree of supersaturation (130-210 MPa), as well as initial water content. For most experiments, we do not observe any increase in bubble number density after 10-20 s, suggesting that bubble nucleation has stopped. The bubble number density does not show a systematic correlation with decompression rate.

  10. Influence of repeated daily diving on decompression stress.

    PubMed

    Zanchi, J; Ljubkovic, M; Denoble, P J; Dujic, Z; Ranapurwala, S; Pollock, N W

    2014-06-01

    Acclimatization (an adaptive change in response to repeated environmental exposure) to diving could reduce decompression stress. A decrease in post-dive circulating venous gas emboli (VGE or bubbles) would represent positive acclimatization. The purpose of this study was to determine whether four days of daily diving alter post-dive bubble grades. 16 male divers performed identical no-decompression air dives on 4 consecutive days to 18 meters of sea water for 47 min bottom times. VGE monitoring was performed with transthoracic echocardiography every 20 min for 120 min post-dive. Completion of identical daily dives resulted in progressively decreasing odds (or logit risk) of having relatively higher grade bubbles on consecutive days. The odds on Day 4 were half that of Day 1 (OR 0.50, 95% CI: 0.34, 0.73). The odds ratio for a >III bubble grade on Day 4 was 0.37 (95% CI: 0.20, 0.70) when compared to Day 1. The current study indicates that repetitive daily diving may reduce bubble formation, representing a positive (protective) acclimatization to diving. Further work is required to evaluate the impact of additional days of diving and multiple dive days and to determine if the effect is sufficient to alter the absolute risk of decompression sickness.

  11. Decryption-decompression of AES protected ZIP files on GPUs

    NASA Astrophysics Data System (ADS)

    Duong, Tan Nhat; Pham, Phong Hong; Nguyen, Duc Huu; Nguyen, Thuy Thanh; Le, Hung Duc

    2011-10-01

    AES is a strong encryption system, so decryption-decompression of AES encrypted ZIP files requires very large computing power and techniques of reducing the password space. This makes implementations of techniques on common computing system not practical. In [1], we reduced the original very large password search space to a much smaller one which surely containing the correct password. Based on reduced set of passwords, in this paper, we parallel decryption, decompression and plain text recognition for encrypted ZIP files by using CUDA computing technology on graphics cards GeForce GTX295 of NVIDIA, to find out the correct password. The experimental results have shown that the speed of decrypting, decompressing, recognizing plain text and finding out the original password increases about from 45 to 180 times (depends on the number of GPUs) compared to sequential execution on the Intel Core 2 Quad Q8400 2.66 GHz. These results have demonstrated the potential applicability of GPUs in this cryptanalysis field.

  12. Protective Effects of Fluoxetine on Decompression Sickness in Mice

    PubMed Central

    Blatteau, Jean-Eric; Barre, Sandrine; Pascual, Aurelie; Castagna, Olivier; Abraini, Jacques H.; Risso, Jean-Jacques; Vallee, Nicolas

    2012-01-01

    Massive bubble formation after diving can lead to decompression sickness (DCS) that can result in central nervous system disorders or even death. Bubbles alter the vascular endothelium and activate blood cells and inflammatory pathways, leading to a systemic pathophysiological process that promotes ischemic damage. Fluoxetine, a well-known antidepressant, is recognized as having anti-inflammatory properties at the systemic level, as well as in the setting of cerebral ischemia. We report a beneficial clinical effect associated with fluoxetine in experimental DCS. 91 mice were subjected to a simulated dive at 90 msw for 45 min before rapid decompression. The experimental group received 50 mg/kg of fluoxetine 18 hours before hyperbaric exposure (n = 46) while controls were not treated (n = 45). Clinical assessment took place over a period of 30 min after surfacing. At the end, blood samples were collected for blood cells counts and cytokine IL-6 detection. There were significantly fewer manifestations of DCS in the fluoxetine group than in the controls (43.5% versus 75.5%, respectively; p = 0.004). Survivors showed a better and significant neurological recovery with fluoxetine. Platelets and red cells were significantly decreased after decompression in controls but not in the treated mice. Fluoxetine reduced circulating IL-6, a relevant marker of systemic inflammation in DCS. We concluded that fluoxetine decreased the incidence of DCS and improved motor recovery, by limiting inflammation processes. PMID:23145072

  13. Traumatic extradural haematoma revealed after contralateral decompressive craniectomy.

    PubMed

    Nadig, Adarsh S; King, Andrew T

    2012-12-01

    Traumatic extradural haematoma following a severe head injury is well documented in neurosurgical literature. We report a case of traumatic extradural haematoma which initially was concealed by the high intracranial pressure (ICP) and revealed after the contralateral decompressive craniectomy. A 21-year-old roofer sustained severe head injury from a fall. The CT brain showed right sided fronto-temporal contusions with small acute subdural haematoma and left orbital roof fracture extending into the temporal bone. ICP was above 45 mmHg even after maximal medical therapy. Decompressive craniectomy was performed on the right side along with contusionectomy. Within an hour, ICP spiked and the CT brain showed left side extradural haematoma. The second surgery demonstrated a bleeding middle meningeal artery associated with the left temporal bone fracture. The clinical sequence of events, radiological and operative findings revealed this to be a traumatic extradural haematoma sustained at the initial trauma. This was revealed after the tamponade effect was released from the initial decompressive craniectomy on the contralateral side.

  14. Musculoskeletal-induced Nucleation in Altitude Decompression Sickness

    NASA Technical Reports Server (NTRS)

    Pollock, N. W.; Natoli, M. J.; Conkin, J.; Wessel, J. H., III; Gernhardt, M. L.

    2014-01-01

    Musculoskeletal activity has the potential to both improve and compromise decompression safety. Exercise enhances inert gas elimination during oxygen breathing prior to decompression (prebreathe), but it may also promote bubble nuclei formation (nucleation), which can lead to gas phase separation and bubble growth and increase the risk of decompression sickness (DCS). The timing, pattern and intensity of musculoskeletal activity and the level of tissue supersaturation may be critical to the net effect. There are limited data available to evaluate cost-benefit relationships. Understanding the relationship is important to improve our understanding of the underlying mechanisms of nucleation in exercise prebreathe protocols and to quantify risk in gravity and microgravity environments. Data gathered during NASA's Prebreathe Reduction Program (PRP) studies combined oxygen prebreathe and exercise followed by low pressure (4.3 psi; altitude equivalent of 30,300 ft [9,235 m]) microgravity simulation to produce two protocols used by astronauts preparing for extravehicular activity. Both the Phase II/CEVIS (cycle ergometer vibration isolation system) and ISLE (in-suit light exercise) trials eliminated ambulation to more closely simulate the microgravity environment. The CEVIS results (35 male, 10 female) serve as control data for this NASA/Duke study to investigate the influence of ambulation exercise on bubble formation and the subsequent risk of DCS.

  15. Acceleration of adiabatic quantum dynamics in electromagnetic fields

    SciTech Connect

    Masuda, Shumpei; Nakamura, Katsuhiro

    2011-10-15

    We show a method to accelerate quantum adiabatic dynamics of wave functions under electromagnetic field (EMF) by developing the preceding theory [Masuda and Nakamura, Proc. R. Soc. London Ser. A 466, 1135 (2010)]. Treating the orbital dynamics of a charged particle in EMF, we derive the driving field which accelerates quantum adiabatic dynamics in order to obtain the final adiabatic states in any desired short time. The scheme is consolidated by describing a way to overcome possible singularities in both the additional phase and driving potential due to nodes proper to wave functions under EMF. As explicit examples, we exhibit the fast forward of adiabatic squeezing and transport of excited Landau states with nonzero angular momentum, obtaining the result consistent with the transitionless quantum driving applied to the orbital dynamics in EMF.

  16. Adiabatic shear bands localization in materials undergoing deformations

    NASA Astrophysics Data System (ADS)

    Ryabov, P. N.; Kudryashov, N. A.; Muratov, R. V.

    2017-01-01

    We consider the adiabatic shear banding phenomenon in composite materials undergoing the high speed shear deformations. The mathematical model of adiabatic shear banding in thermo-visco-plastic material is given. New two step numerical algorithm which is based on the Courant-Isaacson-Rees scheme that allows one to simulate fully localized plastic flow from initial stage of localization is proposed. To test this numerical algorithm we use three benchmark problems. The testing results show the accuracy and efficiency of proposed algorithm. The features of adiabatic shear bands formation in composites are studied. The existence of characteristic depth of localization in composites is shown. Influence of initial temperature distribution on the processes of adiabatic shear bands formation in composites is considered.

  17. Adiabaticity and spectral splits in collective neutrino transformations

    SciTech Connect

    Raffelt, Georg G.; Smirnov, Alexei Yu.

    2007-12-15

    Neutrinos streaming off a supernova core transform collectively by neutrino-neutrino interactions, leading to 'spectral splits' where an energy E{sub split} divides the transformed spectrum sharply into parts of almost pure but different flavors. We present a detailed description of the spectral-split phenomenon which is conceptually and quantitatively understood in an adiabatic treatment of neutrino-neutrino effects. Central to this theory is a self-consistency condition in the form of two sum rules (integrals over the neutrino spectra that must equal certain conserved quantities). We provide explicit analytic and numerical solutions for various neutrino spectra. We introduce the concept of the adiabatic reference frame and elaborate on the relative adiabatic evolution. Violating adiabaticity leads to the spectral split being 'washed out'. The sharpness of the split appears to be represented by a surprisingly universal function.

  18. Adiabatic and isocurvature perturbation projections in multi-field inflation

    SciTech Connect

    Gordon, Chris; Saffin, Paul M. E-mail: Paul.Saffin@nottingham.ac.uk

    2013-08-01

    Current data are in good agreement with the predictions of single field inflation. However, the hemispherical asymmetry, seen in the cosmic microwave background data, may hint at a potential problem. Generalizing to multi-field models may provide one possible explanation. A useful way of modeling perturbations in multi-field inflation is to investigate the projection of the perturbation along and perpendicular to the background fields' trajectory. These correspond to the adiabatic and isocurvature perturbations. However, it is important to note that in general there are no corresponding adiabatic and isocurvature fields. The purpose of this article is to highlight the distinction between a field redefinition and a perturbation projection. We provide a detailed derivation of the evolution of the isocurvature perturbation to show that no assumption of an adiabatic or isocurvature field is needed. We also show how this evolution equation is consistent with the field covariant evolution equations for the adiabatic perturbation in the flat field space limit.

  19. Ultrafast stimulated Raman parallel adiabatic passage by shaped pulses

    SciTech Connect

    Dridi, G.; Guerin, S.; Hakobyan, V.; Jauslin, H. R.; Eleuch, H.

    2009-10-15

    We present a general and versatile technique of population transfer based on parallel adiabatic passage by femtosecond shaped pulses. Their amplitude and phase are specifically designed to optimize the adiabatic passage corresponding to parallel eigenvalues at all times. We show that this technique allows the robust adiabatic population transfer in a Raman system with the total pulse area as low as 3{pi}, corresponding to a fluence of one order of magnitude below the conventional stimulated Raman adiabatic passage process. This process of short duration, typically picosecond and subpicosecond, is easily implementable with the modern pulse shaper technology and opens the possibility of ultrafast robust population transfer with interesting applications in quantum information processing.

  20. Shortcuts to adiabaticity for non-Hermitian systems

    SciTech Connect

    Ibanez, S.; Martinez-Garaot, S.; Torrontegui, E.; Muga, J. G.; Chen Xi

    2011-08-15

    Adiabatic processes driven by non-Hermitian, time-dependent Hamiltonians may be sped up by generalizing inverse engineering techniques based on counter-diabatic (transitionless driving) algorithms or on dynamical invariants. We work out the basic theory and examples described by two-level Hamiltonians: the acceleration of rapid adiabatic passage with a decaying excited level and of the dynamics of a classical particle on an expanding harmonic oscillator.

  1. Nonadiabatic transitions in finite-time adiabatic rapid passage

    NASA Astrophysics Data System (ADS)

    Lu, T.; Miao, X.; Metcalf, H.

    2007-06-01

    To apply the adiabatic rapid passage process repetitively [T. Lu, X. Miao, and H. Metcalf, Phys. Rev. A 71, 061405(R) (2005)], the nonadiabatic transition probability of a two-level atom subject to chirped light pulses over a finite period of time needs to be calculated. Using a unitary first-order perturbation method in the rotating adiabatic frame, an approximate formula has been derived for such transition probabilities in the entire parameter space of the pulses.

  2. ENTROPY-VORTEX WAVES IN NON-ADIABATIC FLOWS

    SciTech Connect

    Ibáñez S, Miguel H.

    2016-02-20

    The Ertel theorem on the vorticity along the flow of adiabatic fluids is generalized for non-adiabatic flows. Several limiting cases are analyzed and the results are applied to flows behind different hydrodynamics fronts, particularly to thermal fronts (heat and cooling fronts). An important conclusion of the present analysis is that vorticity is inherent in the condensation’s (or hot spots) formation by thermal instabilities in plasma flows. Implications for several astrophysical plasmas are outlined.

  3. Vacuum vessel eddy current modeling for TFTR adiabatic compression experiments

    SciTech Connect

    DeLucia, J.; Bell, M.; Wong, K.L.

    1985-07-01

    A relatively simple current filament model of the TFTR vacuum vessel is described. It is used to estimate the three-dimensional structure of magnetic field perturbations in the vicinity of the plasma that arise from vacuum vessel eddy currents induced during adiabatic compression. Eddy currents are calculated self-consistently with the plasma motion. The Shafranov formula and adiabatic scaling laws are used to model the plasma. Although the specific application is to TFTR, the present model is of generation applicability.

  4. Case Control Study of Type II Decompression Sickness Associated with Patent Foramen Ovale in Experimental No-Decompression Dives

    DTIC Science & Technology

    2010-05-01

    Navy Experimental Diving Unit 321 Bullfinch Rd. Panama City, FL 32407-7015 TA 07-08 NEDU TR 10-07 May 2010 CASE CONTROL STUDY OF TYPE II...08 NO. 11. TITLE (Include Security Classification) (U) Case Control Study of Type II Decompression Sickness Associated with Patent Foramen Ovale in...Unit, NEDU 19. ABSTRACT (Continue on reverse if necessary and identify by block number) This is a retrospective case control study comparing

  5. A connection between mix and adiabat in ICF capsules

    NASA Astrophysics Data System (ADS)

    Cheng, Baolian; Kwan, Thomas; Wang, Yi-Ming; Yi, Sunghuan (Austin); Batha, Steven

    2016-10-01

    We study the relationship between instability induced mix, preheat and the adiabat of the deuterium-tritium (DT) fuel in fusion capsule experiments. Our studies show that hydrodynamic instability not only directly affects the implosion, hot spot shape and mix, but also affects the thermodynamics of the capsule, such as, the adiabat of the DT fuel, and, in turn, affects the energy partition between the pusher shell (cold DT) and the hot spot. It was found that the adiabat of the DT fuel is sensitive to the amount of mix caused by Richtmyer-Meshkov (RM) and Rayleigh-Taylor (RT) instabilities at the material interfaces due to its exponential dependence on the fuel entropy. An upper limit of mix allowed maintaining a low adiabat of DT fuel is derived. Additionally we demonstrated that the use of a high adiabat for the DT fuel in theoretical analysis and with the aid of 1D code simulations could explain some aspects of the 3D effects and mix in the capsule experiments. Furthermore, from the observed neutron images and our physics model, we could infer the adiabat of the DT fuel in the capsule and determine the possible amount of mix in the hot spot (LA-UR-16-24880). This work was conducted under the auspices of the U.S. Department of Energy by the Los Alamos National Laboratory under Contract No. W-7405-ENG-36.

  6. Experimental and analytical study of contact melting in a rectangular cavity

    NASA Astrophysics Data System (ADS)

    Dong, Z. F.; Chen, Z. Q.; Wang, Q. J.; Ebadian, M. A.

    1991-09-01

    A detailed investigation is presented of analytical and experimental findings for contact melting in a rectangular cavity for the phase change materials n-heptadecane and n-eicosane. The temperature of the two side walls and bottom surface of the cavity are maintained by circulating water through a highly sensitive thermostat. The other surfaces are subjected to adiabatic conditions. The time-dependent solid-liquid interface contour is measured photographically during the melting process. The experimental data, such as the melting rate and the dimensionless height of the solid, are compared with predicted values of the theoretical model, and good agreement is observed. It is demonstrated that the height of the microchannel at the bottom is constant. This shows that the heat transfer across the channel is dominated by conduction. Results also indicate that the melting on the vertical wall is controlled by conduction. It is concluded, therefore, that heat conduction is the main contact melting mechanism in a rectangular cavity.

  7. Sulfur isotope fractionation between fluid and andesitic melt: An experimental study

    USGS Publications Warehouse

    Fiege, Adrian; Holtz, François; Shimizu, Nobumichi; Mandeville, Charles W.; Behrens, Harald; Knipping, Jaayke L.

    2014-01-01

    Glasses produced from decompression experiments conducted by Fiege et al. (2014a) were used to investigate the fractionation of sulfur isotopes between fluid and andesitic melt upon magma degassing. Starting materials were synthetic glasses with a composition close to a Krakatau dacitic andesite. The glasses contained 4.55–7.95 wt% H2O, ∼140 to 2700 ppm sulfur (S), and 0–1000 ppm chlorine (Cl). The experiments were carried out in internally heated pressure vessels (IHPV) at 1030 °C and oxygen fugacities (fO2) ranging from QFM+0.8 log units up to QFM+4.2 log units (QFM: quartz–fayalite–magnetite buffer). The decompression experiments were conducted by releasing pressure (P) continuously from ∼400 MPa to final P of 150, 100, 70 and 30 MPa. The decompression rate (r) ranged from 0.01 to 0.17 MPa/s. The samples were annealed for 0–72 h (annealing time, tA) at the final P and quenched rapidly from 1030 °C to room temperature (T).The decompression led to the formation of a S-bearing aqueous fluid phase due to the relatively large fluid–melt partitioning coefficients of S. Secondary ion mass spectrometry (SIMS) was used to determine the isotopic composition of the glasses before and after decompression. Mass balance calculations were applied to estimate the gas–melt S isotope fractionation factor αg-m.No detectable effect of r and tA on αg-m was observed. However, SIMS data revealed a remarkable increase of αg-m from ∼0.9985 ± 0.0007 at >QFM+3 to ∼1.0042 ± 0.0042 at ∼QFM+1. Noteworthy, the isotopic fractionation at reducing conditions was about an order of magnitude larger than predicted by previous works. Based on our experimental results and on previous findings for S speciation in fluid and silicate melt a new model predicting the effect of fO2 on αg-m (or Δ34Sg–m) in andesitic systems at 1030 °C is proposed. Our experimental results as well as our modeling are of high importance for the interpretation of S isotope

  8. Sulfur isotope fractionation between fluid and andesitic melt: An experimental study

    NASA Astrophysics Data System (ADS)

    Fiege, Adrian; Holtz, François; Shimizu, Nobumichi; Mandeville, Charles W.; Behrens, Harald; Knipping, Jaayke L.

    2014-10-01

    Glasses produced from decompression experiments conducted by Fiege et al. (2014a) were used to investigate the fractionation of sulfur isotopes between fluid and andesitic melt upon magma degassing. Starting materials were synthetic glasses with a composition close to a Krakatau dacitic andesite. The glasses contained 4.55-7.95 wt% H2O, ∼140 to 2700 ppm sulfur (S), and 0-1000 ppm chlorine (Cl). The experiments were carried out in internally heated pressure vessels (IHPV) at 1030 °C and oxygen fugacities (fO2) ranging from QFM+0.8 log units up to QFM+4.2 log units (QFM: quartz-fayalite-magnetite buffer). The decompression experiments were conducted by releasing pressure (P) continuously from ∼400 MPa to final P of 150, 100, 70 and 30 MPa. The decompression rate (r) ranged from 0.01 to 0.17 MPa/s. The samples were annealed for 0-72 h (annealing time, tA) at the final P and quenched rapidly from 1030 °C to room temperature (T). The decompression led to the formation of a S-bearing aqueous fluid phase due to the relatively large fluid-melt partitioning coefficients of S. Secondary ion mass spectrometry (SIMS) was used to determine the isotopic composition of the glasses before and after decompression. Mass balance calculations were applied to estimate the gas-melt S isotope fractionation factor αg-m. No detectable effect of r and tA on αg-m was observed. However, SIMS data revealed a remarkable increase of αg-m from ∼0.9985 ± 0.0007 at >QFM+3 to ∼1.0042 ± 0.0042 at ∼QFM+1. Noteworthy, the isotopic fractionation at reducing conditions was about an order of magnitude larger than predicted by previous works. Based on our experimental results and on previous findings for S speciation in fluid and silicate melt a new model predicting the effect of fO2 on αg-m (or Δ34Sg-m) in andesitic systems at 1030 °C is proposed. Our experimental results as well as our modeling are of high importance for the interpretation of S isotope signatures in natural samples (e

  9. Adiabatic and non-adiabatic charge pumping in a single-level molecular motor

    NASA Astrophysics Data System (ADS)

    Napitu, B. D.; Thijssen, J. M.

    2015-07-01

    We propose a design for realizing quantum charge pump based on a recent proposal for a molecular motor (Seldenthuis J S et al 2010 ACS Nano 4 6681). Our design is based on the presence of a moiety with a permanent dipole moment which can rotate, thereby modulating the couplings to metallic contacts at both ends of the molecule. Using the non-equilibrium Keldysh Green’s function formalism (NEGF), we show that our design indeed generates a pump current. In the non-interacting pump, the variation of frequency from adiabatic to non-adiabatic regime, can be used to control the direction as well as the amplitude of the average current. The effect of Coulomb interaction is considered within the first- and the second- order perturbation. The numerical implementation of the scheme is quite demanding, and we develop an analytical approximation to obtain a speed-up giving results within a reasonable time. We find that the amplitude of the average pumped current can be controlled by both the driving frequency and the Coulomb interaction. The direction of of pumped current is shown to be determined by the phase difference between left and right anchoring groups.

  10. Adiabatic and non-adiabatic charge pumping in a single-level molecular motor.

    PubMed

    Napitu, B D; Thijssen, J M

    2015-07-15

    We propose a design for realizing quantum charge pump based on a recent proposal for a molecular motor (Seldenthuis J S et al 2010 ACS Nano 4 6681). Our design is based on the presence of a moiety with a permanent dipole moment which can rotate, thereby modulating the couplings to metallic contacts at both ends of the molecule. Using the non-equilibrium Keldysh Green's function formalism (NEGF), we show that our design indeed generates a pump current. In the non-interacting pump, the variation of frequency from adiabatic to non-adiabatic regime, can be used to control the direction as well as the amplitude of the average current. The effect of Coulomb interaction is considered within the first- and the second- order perturbation. The numerical implementation of the scheme is quite demanding, and we develop an analytical approximation to obtain a speed-up giving results within a reasonable time. We find that the amplitude of the average pumped current can be controlled by both the driving frequency and the Coulomb interaction. The direction of of pumped current is shown to be determined by the phase difference between left and right anchoring groups.

  11. Intraoperative computed tomography for cervicomedullary decompression of foramen magnum stenosis in achondroplasia: two case reports.

    PubMed

    Arishima, Hidetaka; Tsunetoshi, Kenzo; Kodera, Toshiaki; Kitai, Ryuhei; Takeuchi, Hiroaki; Kikuta, Ken-Ichiro

    2013-01-01

    The authors report two cases of cervicomedullary decompression of foramen magnum (FM) stenosis in children with achondroplasia using intraoperative computed tomography (iCT). A 14-month-old girl with myelopathy and retarded motor development, and a 10-year-old girl who had already undergone incomplete FM decompression was presented with myelopathy. Both patients underwent decompressive sub-occipitalcraniectomy and C1 laminectomy without duraplasty using iCT. It clearly showed the extent of FM decompression during surgery, which finally enabled sufficient decompression. After the operation, their myelopathy improved. We think that iCT can provide useful information and guidance for sufficient decompression for FM stenosis in children with achondroplasia.

  12. Adiabatic fission barriers in superheavy nuclei

    NASA Astrophysics Data System (ADS)

    Jachimowicz, P.; Kowal, M.; Skalski, J.

    2017-01-01

    Using the microscopic-macroscopic model based on the deformed Woods-Saxon single-particle potential and the Yukawa-plus-exponential macroscopic energy, we calculated static fission barriers Bf for 1305 heavy and superheavy nuclei 98 ≤Z ≤126 , including even-even, odd-even, even-odd and odd-odd systems. For odd and odd-odd nuclei, adiabatic potential-energy surfaces were calculated by a minimization over configurations with one blocked neutron or/and proton on a level from the 10th below to the 10th above the Fermi level. The parameters of the model that have been fixed previously by a fit to masses of even-even heavy nuclei were kept unchanged. A search for saddle points has been performed by the "imaginary water flow" method on a basic five-dimensional deformation grid, including triaxiality. Two auxiliary grids were used for checking the effects of the mass asymmetry and hexadecapole nonaxiality. The ground states (g.s.) were found by energy minimization over configurations and deformations. We find that the nonaxiality significantly changes first and second fission saddle in many nuclei. The effect of the mass asymmetry, known to lower the second, very deformed saddles in actinides, in the heaviest nuclei appears at the less deformed saddles in more than 100 nuclei. It happens for those saddles in which the triaxiality does not play any role, which suggests a decoupling between effects of the mass asymmetry and triaxiality. We studied also the influence of the pairing interaction strength on the staggering of Bf for odd- and even-particle numbers. Finally, we provide a comparison of our results with other theoretical fission barrier evaluations and with available experimental estimates.

  13. The Asthenosphere Melting Regimes Alteration due to Changing Conditions of Upper Mantle

    NASA Astrophysics Data System (ADS)

    Perepechko, Y. V.; Sharapov, V. N.; Sorokin, K., Jr.

    2014-12-01

    Analyzed in the article are different asthenosphere magma generation regimes above the upper mantle hot spots as thermodynamic and geometric parameters of the upper mantle and the conditions on its boundaries vary. The two-layer mantle model is applied to consider the formation of decompression melting areas. The thickness of metasomatically altered lithospheric mantle is determined by the mantle substance rheology and the location of the upper boundary of asthenosphere. We also take into consideration the principal solid state phase transitions by using the mantle substance state equation. The sizes and distribution of hot spots as well as their maximal temperature were defined by the thermodynamic conditions of the perovskite transition existence. The numerical analysis results demonstrate the manifestation of three main mantle dynamics modes; the conditions necessary to form the partial melting zones are not reached; some melting areas with the 30 to 65 Ma existence time do occur; the melting areas that are formed exist permanently. The permanently existing asthenosphere zones are marked by quasiperiodical variation in thickness and the degree of melting. The typical temperatures of a hot spot sharing these modes are the 1740°С and 2020°С correspondingly. The originally presupposed heating degree and the temperature ratio of the upper mantle do influence the decompression melting degree substantially and - to a lesser extent - they influence the size of melting zones. The primary evolution of the second mode is described by the development of a complex system of asthenosphere zones that lead to the occurrence of additional convectional cells dividing the partial melting zone. The variation in the rheological properties of the mantle substance also contributes to the manifestation of the complex structure of asthenosphere zone. The work was made with support of the Russian Foundation for Basic Research grant #12-05-00625.

  14. Influence of starting material on the degassing behavior of trachytic and phonolitic melts

    NASA Astrophysics Data System (ADS)

    Preuss, Oliver; Marxer, Holger; Nowak, Marcus

    2015-04-01

    The dynamic magmatic processes beneath volcanic systems, occurring during magma ascent, cannot be observed directly in nature. Simulation of magma ascent in the lab realized by continuous decompression (CD) of a volatile containing melt is essential to understand these processes that may lead to potentially catastrophic eruptions threatening millions of people in highly populated areas like Naples located between the Campi Flegrei Volcanic Field and the Monte Somma-Vesuvio strato-volcano. In this project, experimental simulations of Campanian Ignimbrite (CI) magma ascent will give insight to the mechanisms of the CI super eruption, thus providing tools for volcanic hazard assessment at the high risk Campanian Volcanic District and other comparable volcanic systems. Additionally, comparable experiments with the same conditions using the 'white pumice' composition of the catastrophic Vesuvius AD 79 (VAD79) eruption, have been conducted. So far, the experiments were performed in an internally heated argon pressure vessel coupled with a high-pressure low-flow metering valve and a piezoelectric nano-positioning system using a starting pressure of 200 MPa, H2O content of about 5 wt% and two different decompression rates (0.024 and 0.17 MPa/s) at a superliquidus temperature of 1050 ° C to ensure a crystal free melt and a homogeneous bubble nucleation. Experiments were conducted with both, glass powder and cylinders, subsequently decompressed to 75 and 100 MPa and rapidly quenched. Beside the results that e.g. decompression rate, volatile content, fluid solubility and target pressure affect the degassing behavior of the melt, the influence of the starting material on the degassing processes is significant. Analyses of BSE- and transmitted light microscopy images revealed a different degassing behavior of glass cylinder experiments compared to powders. Nitrogen has a very low solubility in hydrous silicate melts, supporting our suggestion that preexisting nitrogen rich

  15. Melt inclusions: Chapter 6

    USGS Publications Warehouse

    ,; Lowenstern, J. B.

    2014-01-01

    Melt inclusions are small droplets of silicate melt that are trapped in minerals during their growth in a magma. Once formed, they commonly retain much of their initial composition (with some exceptions) unless they are re-opened at some later stage. Melt inclusions thus offer several key advantages over whole rock samples: (i) they record pristine concentrations of volatiles and metals that are usually lost during magma solidification and degassing, (ii) they are snapshots in time whereas whole rocks are the time-integrated end products, thus allowing a more detailed, time-resolved view into magmatic processes (iii) they are largely unaffected by subsolidus alteration. Due to these characteristics, melt inclusions are an ideal tool to study the evolution of mineralized magma systems. This chapter first discusses general aspects of melt inclusions formation and methods for their investigation, before reviewing studies performed on mineralized magma systems.

  16. Magmatic storage conditions, decompression rate, and incipient caldera collapse of the 1902 eruption of Santa Maria Volcano, Guatemala

    NASA Astrophysics Data System (ADS)

    Andrews, Benjamin J.

    2014-08-01

    Phase equilibria experiments and analysis of natural pumice and phenocryst compositions indicate the 1902 Santa Maria dacite was stored at ~ 140-170 MPa and 840-850 °C prior to eruption. H2O-saturated, cold-seal experiments conducted in vessels with an intrinsic log fO2 of NNO + 1 ± 0.5 show that the natural phase assemblage (melt + plagioclase + amphibole + orthopyroxene + Fe-Ti oxides + apatite) is stable from approximately 115-140 MPa at temperatures below ~ 825 °C, to ~ 840-860 °C at 150 MPa, to > 850 and < 875 °C at 200 MPa. Natural plagioclase phenocrysts have rim compositions that range from An40-An45; this range of compositions defines a ~ 20 °C band that intersects the stable phase assemblage at ~ 150 MPa and 850 °C. Plagioclase hosted melt inclusions were analyzed using FTIR and commonly contain < 5 wt.% H2O, which corresponds to a pressure of ~ 170 MPa at 850 °C, under pure H2O saturated conditions. Amphibole geothermobarometry (Ridolfi et al., 2010) applied to experimental samples suggest two populations of amphiboles, phenocrysts grown during the experiments and inherited xenocrysts, but the pressure-temperature conditions returned by the geothermobarometer are routinely > 50 MPa and > 50 °C greater than experimental run conditions; precise estimates of magmatic conditions based solely upon amphibole composition are likely inaccurate. The experimental results and analysis of natural crystals suggest that although the natural amphiboles likely record a broad range of magmatic conditions, only the lower bounds of that range reflect pre-eruptive storage conditions. Comparison of Santa Maria microlite abundances with decompression experiments examining other silicic systems from the literature suggests that the 1902 dacite decompressed at the rate of ~ 0.005 to 0.01 MPa/s during the eruption. Applying the decompression rate with the previously described eruption rate of approximately 2-3 × 108 kg/s (Williams and Self, 1983; Carey and Sparks, 1986

  17. Time Course of Endothelial Dysfunction Induced by Decompression Bubbles in Rats

    PubMed Central

    Zhang, Kun; Wang, Mengmeng; Wang, Haowen; Liu, Yinuo; Buzzacott, Peter; Xu, Weigang

    2017-01-01

    Decompression stress can cause endothelial injury, leading to systematic inflammation and prothrombotic phenomena. Our previous work found that endothelial injury following decompression correlated positively with bubble formation. This study aimed to investigate the time course of endothelial injury and the relationship with bubble amounts. Rats were subjected to a simulated air dive to 7 ATA for 90 min with rapid decompression. Bubbles were detected ultrasonically at the root of pulmonary arteries following decompression. Surviving rats were randomly divided into six groups according to sampling time following decompression (2, 6, 12, 24, 48, and 72 h). Three parameters, serum levels of malondialdehyde (MDA), endothelin-1 (ET-1), and intercellular cell adhesion molecule-1 (ICAM-1) were identified from our previous study and measured. The level of MDA reached a peak level at 12 h post decompression, and then decreased gradually to control level before 72 h. For both ET-1 and ICAM-1, the greatest expression appeared at 24 h following surfacing, and the increases lasted for more than 72 h. These changes correlated positively with bubble counts at most detection time points. This study reveals the progress of endothelial dysfunction following decompression which provides guidance for timing the determination at least for the current model. The results further verify that bubbles are the causative agents of decompression induced endothelial damage and bubble amounts are an objective and suitable parameter to predict endothelial dysfunction. Most importantly, levels of endothelial biomarkers post dive may serve as sensitive parameters for assessing bubble load and decompression stress. PMID:28386238

  18. Intra-Operative Vertebroplasty Combined with Posterior Cord Decompression

    PubMed Central

    Allegretti, Luca; Mavilio, Nicola; Fiaschi, Pietro; Bragazzi, Roberto; Pacetti, Mattia; Castelletti, Lara; Saitta, Laura; Castellan, Lucio

    2014-01-01

    Summary Percutaneous vertebroplasty (VP) is a minimally invasive technique for the treatment of vertebral pathology providing early vertebral stabilization and pain relief. In cases of vertebral pathology complicated by spinal cord compression with associated neurological deficits, VP alone cannot be performed free of risks. We describe a combined approach in which decompressive laminectomy and intra-operative vertebroplasty (IVP) are performed during a single session. Among the 252 VP performed in our centre in the past three years, 12 patients (12 vertebral levels) with different pathologies (six symptomatic haemangiomas, two metastatic fractures, four osteoporotic fractures) were treated with an open procedure combined with surgery. All cases were treated with decompressive laminectomy and IVP (mono/bipeduncular or median-posterior trans-somatic access). Five patients with symptomatic haemangiomas were treated with endovascular embolization prior to the combined approach. A visual analogue scale (VAS) was applied to assess pain intensity before and after surgery. The neurological deficits were evaluated with an ASIA impairment scale. In all cases benefit from pain and neurological deficits was observed. The mean VAS score decreased from 7.8 to 2.5 after surgery. The ASIA score improved in all cases (five cases from D to E and five cases from C to D). No clinical complications were observed. In one case a CT scan performed after the procedure showed a foraminal accumulation of PMMA, but the patient referred no symptoms. IVP can be successfully applied in different pathologies affecting the vertebrae. In our limited series this approach proved safe and efficient to provide decompression of spinal cord and dural sac and vertebral body stabilization in a single session. PMID:25363261

  19. Decompression without Fusion for Low-Grade Degenerative Spondylolisthesis

    PubMed Central

    Cheung, Jason Pui Yin; Cheung, Prudence Wing Hang; Cheung, Kenneth Man Chee

    2016-01-01

    Study Design Retrospective series. Purpose Assess results of decompression-only surgery for low-grade degenerative spondylolisthesis with consideration of instability. Overview of Literature There is no consensus on whether fusion or decompression-only surgery leads to better outcomes for patients with low-grade degenerative spondylolisthesis. Current trends support fusion but many studies are flawed due to over-generalization without consideration of radiological instability and their variable presentations and natural history. Methods Patients with surgically treated degenerative spondylolisthesis from 1990–2013 were included. Clinical and radiological instability measures were included. Any residual or recurrence of symptoms, revision surgery performed and functional outcome scores including the numerical global rate of change scale, visual analogue scale, and modified Barthel index were measured. Follow-up periods for patients were divided into short-term (<5 years), mid-term (5–10 years) and long-term (>10 years). Results A total of 64 patients were recruited. Mechanical low back pain was noted in 48 patients and most (85.4%) had relief of back pain postoperatively. Radiological instability was noted in 4 subjects by flexion-extension radiographs and 12 subjects with prone traction radiographs by increased disc height and reduction of olisthesis and slip angle. From the results of the short-term, mid-term and long-term follow-up, reoperation only occurred within the first 5-year follow-up period. All functional scores improved from preoperative to postoperative 1-year follow-up. Conclusions Decompression-only for low-grade degenerative spondylolisthesis has good long-term results despite instability. Further higher-level studies should be performed on this patient group with radiological instability to suggest the superior surgical option. PMID:26949462

  20. Diving decompression models and bubble metrics: modern computer syntheses.

    PubMed

    Wienke, B R

    2009-04-01

    A quantitative summary of computer models in diving applications is presented, underscoring dual phase dynamics and quantifying metrics in tissue and blood. Algorithms covered include the multitissue, diffusion, split phase gradient, linear-exponential, asymmetric tissue, thermodynamic, varying permeability, reduced gradient bubble, tissue bubble diffusion, and linear-exponential phase models. Defining relationships are listed, and diver staging regimens are underscored. Implementations, diving sectors, and correlations are indicated for models with a history of widespread acceptance, utilization, and safe application across recreational, scientific, military, research, and technical communities. Presently, all models are incomplete, but many (included above) are useful, having resulted in diving tables, underwater meters, and dive planning software. Those herein employ varying degrees of calibration and data tuning. We discuss bubble metrics in tissue and blood as a backdrop against computer models. The past 15 years, or so, have witnessed changes and additions to diving protocols and table procedures, such as shorter nonstop time limits, slower ascent rates, shallow safety stops, ascending repetitive profiles, deep decompression stops, helium based breathing mixtures, permissible reverse profiles, multilevel techniques, both faster and slower controlling repetitive tissue halftimes, smaller critical tensions, longer flying-after-diving surface intervals, and others. Stimulated by Doppler and imaging technology, table and decompression meter development, theory, statistics, chamber and animal testing, or safer diving consensus, these modifications affect a gamut of activity, spanning bounce to decompression, single to multiday, and air to mixed gas diving. As it turns out, there is growing support for many protocols on operational, experimental, and theoretical grounds, with bubble models addressing many concerns on plausible bases, but with further testing or

  1. Gender and Decompression Sickness: A Critical Review and Analysis

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The author addressed the following questions: are women at greater risk of decompression sickness and venous gas emboli at certain times in their reproductive cycle, is risk modified by the use of birth control pills (BCP), and is there a difference in overall risk between men and women under the same decompression dose? The summary considers information from the few abstracts and reports that were available. Except for the observation of more Type II DCS in women, particularly in women who fly after diving, there was no compelling evidence of a difference in DCS risk between men and women SCUBA divers. Many women that presented with DCS symptoms seemed to be in or near menses, with statistically fewer cases reported as time increased from menses. There was no compelling evidence that the use of BCP in SCUBA divers increases the risk of DCS. There were insufficient data about VGE from SCUBA diving to make any conclusion about the incidence of VGE and gender. In contrast, there were ample data about VGE from research in altitude chambers. Women produced less VGE and less Grade IV VGE compared to men under the same decompression dose, certainly when resting oxygen prebreathe (PB) was performed prior to ascent to altitude. Dual-cycle ergometry exercise during PB tends to reduce the differences in VGE between men and women. There was no compelling evidence that the risk of altitude DCS was different between men and women. However, a large number of DCS cases were associated with menses, and the use of BCP did seem to put women at a slightly greater risk than those that did not use BCP. There were substantial observations that women comprised a larger number of difficult cases that required complicated medical management.

  2. Ischiofemoral Space Decompression Through Posterolateral Approach: Cutting Block Technique

    PubMed Central

    Howse, Elizabeth A.; Mannava, Sandeep; Tamam, Cüneyt; Martin, Hal D.; Bredella, Miriam A.; Stubbs, Allston J.

    2014-01-01

    Ischiofemoral space impingement has become an increasingly recognized extracapsular cause of atypical hip, deep gluteal, and groin pain that can be treated endoscopically. We present a minimally invasive posterolateral technique that preserves the attachment of the iliopsoas tendon and quadratus femoris insertion while decompressing the ischiofemoral space by resecting the lesser trochanter. Furthermore, we present tips to perform this technique in a manner that minimizes the potential for damage to the sciatic nerve. This technique also allows the surgeon to treat concurrent hip pathology arthroscopically. PMID:25685670

  3. Surgical decompression for notalgia paresthetica: a case report.

    PubMed

    Williams, Eric H; Rosson, Gedge D; Elsamanoudi, Ibrahim; Dellon, A Lee

    2010-01-01

    Notalgia paresthetica is a rare nerve compression. From the Greek word noton, meaning "back," and algia, meaning "pain," "notalgia paresthetica" implies that symptoms of burning pain, itching, and/or numbness in the localized region between the spinous processes of T2 through T6 and the medial border of the scapula constitute a nerve compression syndrome. The compressed nerve is the dorsal branch of the spinal nerve. It is compressed by the paraspinous muscles and fascia against the transverse process of these spinal segments. This is the first report of symptomatic relief by decompression of this nerve.

  4. Autonomic neurosurgery: from microvascular decompression to image guided stimulation

    PubMed Central

    Pereira, EAC; Green, AL

    2007-01-01

    The paper reviews mechanisms underlying autonomic disorders, with a focus on cardiovascular dysfunction. Neurosurgical approaches are described for medically refractory hypertension and orthostatic hypotension. After review of microvascular decompression of the rostral ventrolateral medulla, stereotactic CT and MRI guided deep brain stimulation of the periaqueductal grey matter (PAG) is evaluated. Results are presented from patient studies showing reductions in blood pressure with ventral PAG stimulation and increases in blood pressure with dorsal PAG stimulation. A rationale for the treatment of autonomic disorders by neurosurgical intervention is discussed. PMID:21614256

  5. Recomputation of U. S. Navy Standard Air Decompression Tables,

    DTIC Science & Technology

    1982-01-31

    Contr-act #NOOQ(4-81-G-0216 with funds provided by the Naval Vedical Research and Development Comrmand. January 31, 1982 Appzavod fol Tru"-Ilc DL~trbuban...AO-AIII 991 SEA-SPACE RESEARCH . CO INC MARRERO LA F/6 6/19 RECOMPUTATZON F U. S. NAVY STANDARD AIR DECOMPRESSION TABLES, WI JAN 82 P 0 EDEL N0001-81...Peter 0. Edel SEA-SPACE RESEARCH COMPANY, INC. Marrero, Louisiana The research reported here has been supported under the Office of Naval Research

  6. Probable decompression sickness in a trainee with atopic dermatitis.

    PubMed

    Yoneda, I

    1998-07-01

    Hypobaric chamber training has a potential risk of inducing decompression sickness (DCS). A case of a patient with an atopic dermatitis who complained of paresthesia and numbness in his left arm and shoulder during the altitude exposure is presented here. His symptoms were severe enough for the attending medical officer to diagnose Type II DCS, but it turned out to be a probable case of simple skin bends requiring no treatment. The author can find no better explanation for this discrepancy than the contribution of dermatitis. The possibility of atopic dermatitis confounding the correct diagnosis of the severity of DCS is proposed.

  7. Seismic evidence of effects of water on melt transport in the Lau back-arc mantle.

    PubMed

    Wei, S Shawn; Wiens, Douglas A; Zha, Yang; Plank, Terry; Webb, Spahr C; Blackman, Donna K; Dunn, Robert A; Conder, James A

    2015-02-19

    Processes of melt generation and transport beneath back-arc spreading centres are controlled by two endmember mechanisms: decompression melting similar to that at mid-ocean ridges and flux melting resembling that beneath arcs. The Lau Basin, with an abundance of spreading ridges at different distances from the subduction zone, provides an opportunity to distinguish the effects of these two different melting processes on magma production and crust formation. Here we present constraints on the three-dimensional distribution of partial melt inferred from seismic velocities obtained from Rayleigh wave tomography using land and ocean-bottom seismographs. Low seismic velocities beneath the Central Lau Spreading Centre and the northern Eastern Lau Spreading Centre extend deeper and westwards into the back-arc, suggesting that these spreading centres are fed by melting along upwelling zones from the west, and helping to explain geochemical differences with the Valu Fa Ridge to the south, which has no distinct deep low-seismic-velocity anomalies. A region of low S-wave velocity, interpreted as resulting from high melt content, is imaged in the mantle wedge beneath the Central Lau Spreading Centre and the northeastern Lau Basin, even where no active spreading centre currently exists. This low-seismic-velocity anomaly becomes weaker with distance southward along the Eastern Lau Spreading Centre and the Valu Fa Ridge, in contrast to the inferred increase in magmatic productivity. We propose that the anomaly variations result from changes in the efficiency of melt extraction, with the decrease in melt to the south correlating with increased fractional melting and higher water content in the magma. Water released from the slab may greatly reduce the melt viscosity or increase grain size, or both, thereby facilitating melt transport.

  8. Signatures of nonthermal melting

    PubMed Central

    Zier, Tobias; Zijlstra, Eeuwe S.; Kalitsov, Alan; Theodonis, Ioannis; Garcia, Martin E.

    2015-01-01

    Intense ultrashort laser pulses can melt crystals in less than a picosecond but, in spite of over thirty years of active research, for many materials it is not known to what extent thermal and nonthermal microscopic processes cause this ultrafast phenomenon. Here, we perform ab-initio molecular-dynamics simulations of silicon on a laser-excited potential-energy surface, exclusively revealing nonthermal signatures of laser-induced melting. From our simulated atomic trajectories, we compute the decay of five structure factors and the time-dependent structure function. We demonstrate how these quantities provide criteria to distinguish predominantly nonthermal from thermal melting. PMID:26798822

  9. LETTERS AND COMMENTS: Adiabatic process reversibility: microscopic and macroscopic views

    NASA Astrophysics Data System (ADS)

    Anacleto, Joaquim; Pereira, Mário G.

    2009-05-01

    The reversibility of adiabatic processes was recently addressed by two publications. In the first (Miranda 2008 Eur. J. Phys. 29 937-43), an equation was derived relating the initial and final volumes and temperatures for adiabatic expansions of an ideal gas, using a microscopic approach. In that relation the parameter r accounts for the process reversibility, ranging between 0 and 1, which corresponds to the free and reversible expansion, respectively. In the second (Anacleto and Pereira 2009 Eur. J. Phys. 30 177-83), the authors have shown that thermodynamics can effectively and efficiently be used to obtain the general law for adiabatic processes carried out by an ideal gas, including compressions, for which r \\ge 1. The present work integrates and extends the aforementioned studies, providing thus further insights into the analysis of the adiabatic process. It is shown that Miranda's work is wholly valid for compressions. In addition, it is demonstrated that the adiabatic reversibility coefficient given in terms of the piston velocity and the root mean square velocity of the gas particles is equivalent to the macroscopic description, given just by the quotient between surroundings and system pressure values.

  10. Initial Melting and wall-rock flux-melting of a wet multi-component mantle and its implications for the formation of MORB

    NASA Astrophysics Data System (ADS)

    Morgan, J. P.; Hasenclever, J.

    2013-12-01

    We explore several simple scenarios for wet melting of a heterogeneous multi- component mantle. In our melting formulation the mantle is viewed as a mixture consisting of a heterogeneously depleted peridotite matrix with embedded veins of fertile peridotite and/or geochemically enriched pyroxenite. These lithological units differ in their mineral composition but are assumed to have diffusively equilibrated both their water/hydrogen content and temperature over the hundreds of millions to billions of years prior to entering a melting region. During the melting process, however, only thermal but not chemical (water) equilibrium is assumed between the lithologies, which is a reasonable assumption for veins with thicknesses on the order of few tens to few hundreds of meters, a thermal diffusivity of 10^-6 m^2/s and a diffusivity of hydrogen of less than 3*10^-9 m^2/s. The thermodynamic formulation of the multi-component melting process, during which all components have to share thermal energy, is based on Phipps Morgan (2001). The wet melting parameterization by Katz et al. (2003) has been included in the thermodynamic formulation by modifying its solidus-depletion-dependence and treating water partitioning during melting as partitioning of a trace element with a D-value like that of Ce. Usually, fractional melting with a small trapped melt fraction is assumed. We will mostly discuss results from 1-D model calculations, which represent the idealized decompression of a multi-component mantle rising underneath a mid-ocean ridge. Melt-migration is assumed to occur as vertical ascent within each column. We have also extended the formulation to examine the effects of rising melts on 'flux-melting' the wall-rock through which they migrate. We are still testing to see if this mechanism can be the reason why ridge melts almost always have major element chemistries in equilibrium with a peridotitic mantle, while the incompatible trace elements in EMORB reflect the influence of

  11. Modeling of formation of intraplate partial melting zones

    NASA Astrophysics Data System (ADS)

    Perepechko, Y. V.; Sorokin, K. E.

    2010-12-01

    This study suggests the mathematical model of dynamics of partial melting in lithosphere causing formation of magmatic systems. The intraplate magmatic systems can be formed at achievement of required thermodynamic conditions, which can be developed due to the following mechanisms: contact heating; decompression melting at mantle matter penetration into lithosphere; and heating by filtering mantle melts and fluids in the weakened lithosphere zones above the asthenospheric structure related to a hotspot. The most efficient mechanism from the point of time and heating degree is the latter one. It is heating of lithosphere matter by mantle melts and fluids, which is especially important for development of melting sites in these systems. At formation of intraplate magmatic systems the fluid is filtered in a porous medium, porous matrix melts partially, and finally a granulated medium is formed there. To decrease the processes of heat and mass transfer in this system, the equations of dynamics of multiphase multivelocity media are derived in this study. In contrast to the Darcy-type models used in previous studies, the suggested two-velocity hydrodynamics theory describing fluid motions in a porous medium with complex reology is the thermodynamically consistent one and allows the description of nonstationary nonlinear processes. The governing equations of the model describe both the process of filtration through the deformed porous matrix and hydrodynamics of heterophase granulated medium without pressure equilibrium in phases. The work was supported by the grants 08-05-00467, 09-05-00602, 09-05-01084 from the Russian Foundation for Basic Research.

  12. The role of pyroxenite in basalt genesis: Melt-PX, a melting parameterization for mantle pyroxenites between 0.9 and 5 GPa

    NASA Astrophysics Data System (ADS)

    Lambart, Sarah; Baker, Michael B.; Stolper, Edward M.

    2016-08-01

    Geochemical and isotopic data suggest that the source regions of oceanic basalts may contain pyroxenite in addition to peridotite. In order to incorporate the wide range of compositions and melting behaviors of pyroxenites into mantle melting models, we have developed a new parameterization, Melt-PX, which predicts near-solidus temperatures and extents of melting as a function of temperature and pressure for mantle pyroxenites. We used 183 high-pressure experiments (25 compositions; 0.9-5 GPa; 1150-1675°C) to constrain a model of melt fraction versus temperature from 5% melting up to the disappearance of clinopyroxene for pyroxenites as a function of pressure, temperature, and bulk composition. When applied to the global set of experimental data, our model reproduces the experimental F values with a standard error of estimate of 13% absolute; temperatures at which the pyroxenite is 5% molten are reproduced with a standard error of estimate of 30°C over a temperature range of ~500°C and a pressure range of ~4 GPa. In conjunction with parameterizations of peridotite melting, Melt-PX can be used to model the partial melting of multilithologic mantle sources—including the effects of varying the composition and the modal proportion of pyroxenite in such source regions. Examples of such applications include calculations of isentropic decompression melting of a mixed peridotite + pyroxenite mantle; these show that although the potential temperature of the upwelling mantle plays an important role in defining the extent of magma production, the composition and mass fraction of the pyroxenite also exert strong controls.

  13. Melt fracture revisited

    SciTech Connect

    Greenberg, J. M.

    2003-07-16

    In a previous paper the author and Demay advanced a model to explain the melt fracture instability observed when molten linear polymer melts are extruded in a capillary rheometer operating under the controlled condition that the inlet flow rate was held constant. The model postulated that the melts were a slightly compressible viscous fluid and allowed for slipping of the melt at the wall. The novel feature of that model was the use of an empirical switch law which governed the amount of wall slip. The model successfully accounted for the oscillatory behavior of the exit flow rate, typically referred to as the melt fracture instability, but did not simultaneously yield the fine scale spatial oscillations in the melt typically referred to as shark skin. In this note a new model is advanced which simultaneously explains the melt fracture instability and shark skin phenomena. The model postulates that the polymer is a slightly compressible linearly viscous fluid but assumes no slip boundary conditions at the capillary wall. In simple shear the shear stress {tau}and strain rate d are assumed to be related by d = F{tau} where F ranges between F{sub 2} and F{sub 1} > F{sub 2}. A strain rate dependent yield function is introduced and this function governs whether F evolves towards F{sub 2} or F{sub 1}. This model accounts for the empirical observation that at high shears polymers align and slide more easily than at low shears and explains both the melt fracture and shark skin phenomena.

  14. Phase relations and melting of carbonated peridotite between 10 and 20 GPa: a proxy for alkali- and CO2-rich silicate melts in the deep mantle

    NASA Astrophysics Data System (ADS)

    Ghosh, Sujoy; Litasov, Konstantin; Ohtani, Eiji

    2014-02-01

    We determined the melting phase relations, melt compositions, and melting reactions of carbonated peridotite on two carbonate-bearing peridotite compositions (ACP: alkali-rich peridotite + 5.0 wt % CO2 and PERC: fertile peridotite + 2.5 wt % CO2) at 10-20 GPa and 1,500-2,100 °C and constrain isopleths of the CO2 contents in the silicate melts in the deep mantle. At 10-20 GPa, near-solidus (ACP: 1,400-1,630 °C) carbonatitic melts with < 10 wt % SiO2 and > 40 wt % CO2 gradually change to carbonated silicate melts with > 25 wt % SiO2 and < 25 wt % CO2 between 1,480 and 1,670 °C in the presence of residual majorite garnet, olivine/wadsleyite, and clinoenstatite/clinopyroxene. With increasing degrees of melting, the melt composition changes to an alkali- and CO2-rich silicate melt (Mg# = 83.7-91.6; ~ 26-36 wt % MgO; ~ 24-43 wt % SiO2; ~ 4-13 wt % CaO; ~ 0.6-3.1 wt % Na2O; and ~ 0.5-3.2 wt % K2O; ~ 6.4-38.4 wt % CO2). The temperature of the first appearance of CO2-rich silicate melt at 10-20 GPa is ~ 440-470 °C lower than the solidus of volatile-free peridotite. Garnet + wadsleyite + clinoenstatite + carbonatitic melt controls initial carbonated silicate melting at a pressure < 15 GPa, whereas garnet + wadsleyite/ringwoodite + carbonatitic melt dominates at pressure > 15 GPa. Similar to hydrous peridotite, majorite garnet is a liquidus phase in carbonated peridotites (ACP and PERC) at 10-20 GPa. The liquidus is likely to be at ~ 2,050 °C or higher at pressures of the present study, which gives a melting interval of more than 670 °C in carbonated peridotite systems. Alkali-rich carbonated silicate melts may thus be produced through partial melting of carbonated peridotite to 20 GPa at near mantle adiabat or even at plume temperature. These alkali- and CO2-rich silicate melts can percolate upward and may react with volatile-rich materials accumulate at the top of transition zone near 410-km depth. If these refertilized domains migrate upward and convect out of the

  15. A very high speed lossless compression/decompression chip set

    NASA Technical Reports Server (NTRS)

    Venbrux, Jack; Liu, Norley; Liu, Kathy; Vincent, Peter; Merrell, Randy

    1991-01-01

    A chip is described that will perform lossless compression and decompression using the Rice Algorithm. The chip set is designed to compress and decompress source data in real time for many applications. The encoder is designed to code at 20 M samples/second at MIL specifications. That corresponds to 280 Mbits/second at maximum quantization or approximately 500 Mbits/second under nominal conditions. The decoder is designed to decode at 10 M samples/second at industrial specifications. A wide range of quantization levels is allowed (4...14 bits) and both nearest neighbor prediction and external prediction are supported. When the pre and post processors are bypassed, the chip set performs high speed entropy coding and decoding. This frees the chip set from being tied to one modeling technique or specific application. Both the encoder and decoder are being fabricated in a 1.0 micron CMOS process that has been tested to survive 1 megarad of total radiation dosage. The CMOS chips are small, only 5 mm on a side, and both are estimated to consume less than 1/4 of a Watt of power while operating at maximum frequency.

  16. Decompressive Surgery in a Patient with Posttraumatic Syringomyelia

    PubMed Central

    Byun, Min Seok; Hwang, Yong Soon; Park, Sang Keun

    2010-01-01

    Posttraumatic syringomyelia may result from a variety of inherent conditions and traumatic events, or from some combination of these. Many hypotheses have arisen to explain this complex disorder, but no consensus has emerged. A 28-year-old man presented with progressive lower extremity weakness, spasticity, and decreased sensation below the T4 dermatome five years after an initial trauma. Magnetic resonance imaging (MRI) revealed a large, multi-septate syrinx cavity extending from C5 to L1, with a retropulsed bony fragment of L2. We performed an L2 corpectomy, L1-L3 interbody fusion using a mesh cage and screw fixation, and a wide decompression and release of the ventral portion of the spinal cord with an operating microscope. The patient showed complete resolution of his neurological symptoms, including the bilateral leg weakness and dysesthesia. Postoperative MRI confirmed the collapse of the syrinx and restoration of subarachnoid cerebrospinal fluid (CSF) flow. These findings indicate a good correlation between syrinx collapse and symptomatic improvement. This case showed that syringomyelia may develop through obstruction of the subarachnoid CSF space by a bony fracture and kyphotic deformity. Ventral decompression of the obstructed subarachnoid space, with restoration of spinal alignment, effectively treated the spinal canal encroachment and post-traumatic syringomyelia. PMID:20379479

  17. Cortical blindness following posterior lumbar decompression and fusion.

    PubMed

    Agarwal, Nitin; Hansberry, David R; Goldstein, Ira M

    2014-01-01

    Perioperative vision loss following non-ocular surgery is a well-documented phenomenon. In particular, perioperative vision loss has been frequently cited following spinal surgery. Although the rate of vision compromise in spinal surgery is relatively low, the consequences can be quite severe and devastating for the patient. We report a 60-year-old woman who initially presented with back and left leg pain as well as paraparesis. Imaging studies of the lumbar spine showed bony erosion consistent with tumor infiltration of the L3 and L4 spinal segments. Laminectomy at the L2-L4 levels for decompression of the intraspinal tumor was performed. Pathology of the resected bone was consistent with metastatic adenocarincoma. Postoperatively, the patient suffered severe anemia and bilateral infarctions of the posterior cerebral arteries and occipital lobes resulting in vision compromise. Although a definitive pathogenesis remains unknown, preoperative cardiovascular issues and intraoperative hemodynamic instabilities have typically been implicated as high risk factors. High risk factors for this novel clinical presentation of visual compromise following posterior lumbar laminectomy with decompression for an intraspinal tumor are reported.

  18. Case Descriptions and Observations About Cutis Marmorata From Hypobaric Decompressions

    NASA Technical Reports Server (NTRS)

    Conkin, Johnny; Pilmanis, Andrew A.; Webb, James T.

    2002-01-01

    There is disagreement about the pathophysiology, classification, and treatment of cutis marmorata (CM), so there is disagreement about the disposition and medical status of a person that had CM. CM is rare, associated with stressful decompressions, and may be associated with serious signs and symptoms of decompression sickness (DCS). CM presents as purple or bluish-red skin mottling, often in the pectoral region, shoulders, chest, or upper abdomen. It is unethical to induce CM in humans so all information comes from retrospective analysis of case reports, or from animal models. A literature search, seven recent case reports from the Johnson Space Center and Brooks Air Force Base Hypobaric DCS Databases, interviews with DCS treatment experts, and responses to surveys provided the factual information used to arrive at our conclusions and recommendations. The "weight of evidence" indicates that CM is a local, not centrally mediated or systemic response to bubbles. It is unclear whether obstruction of arterial or venous blood flow is the primary insult since the lesion is reported under either condition. Any neurological or cardiovascular involvements are coincidental, developing along the same time course. The skin could be the source of the bubbles due to its mass, the associated layer of fat, and the variable nature of skin blood flow. CM should not be categorized as Type II DCS, should be included with other skin manifestations in a category called cutaneous DCS, and hyperbaric treatment is only needed if ground level oxygen is ineffective in the case of altitude-induced CM.

  19. Diving behaviour and decompression sickness among Galapagos underwater harvesters.

    PubMed

    Westin, A A; Asvall, J; Idrovo, G; Denoble, P; Brubakk, A O

    2005-01-01

    Diving conditions, dive profiles, vascular bubbles, and symptoms of decompression sickness (DCS) in a group of Galapagos commercial divers are described. They harvest sea cucumbers from small boats with surface supplied air (hookah). Dive profiles for 12 divers were recorded using dive loggers, and bubble formation was measured in the pulmonary artery. DCS symptoms were assessed by interview. A total of 380 immersions were recorded over a nine day period. The divers did on average 6.3 immersions per day, in a yo-yo pattern. Mean overall depth was 34.5 FSW. Maximum recorded depth was 107 FSW. Average bottom time per day per diver was 175 minutes. 82 % of all ascents exceeded the recommended maximum ascent rate of 30 FSW/ min. High bubble grades were observed on six occasions, but the test was unreliable. Muscle and joint pain was reported on five occasions, in three different divers. Symptoms were typically managed by analgesics, in-water recompression or not at all. The divers were extremely reluctant to seek professional help for DCS symptoms, mostly due to the high costs of treatment. We conclude that the fishermen dive beyond standard no-decompression limits, and that DCS symptoms are common.

  20. Endothelia-Targeting Protection by Escin in Decompression Sickness Rats

    PubMed Central

    Zhang, Kun; Jiang, Zhongxin; Ning, Xiaowei; Yu, Xuhua; Xu, Jiajun; Buzzacott, Peter; Xu, Weigang

    2017-01-01

    Endothelial dysfunction is involved in the pathogenesis of decompression sickness (DCS) and contributes substantively to subsequent inflammatory responses. Escin, the main active compound in horse chestnut seed extract, is well known for its endothelial protection and anti-inflammatory properties. This study aimed to investigate the potential protection of escin against DCS in rats. Escin was administered orally to adult male rats for 7 d (1.8 mg/kg/day) before a simulated air dive. After decompression, signs of DCS were monitored, and blood and pulmonary tissue were sampled for the detection of endothelia related indices. The incidence and mortality of DCS were postponed and decreased significantly in rats treated with escin compared with those treated with saline (P < 0.05). Escin significantly ameliorated endothelial dysfunction (increased serum E-selectin and ICAM-1 and lung Wet/Dry ratio, decreased serum NO), and oxidative and inflammatory responses (increased serum MDA, MPO, IL-6 and TNF-α) (P < 0.05 or P < 0.01). The results suggest escin has beneficial effects on DCS related to its endothelia-protective properties and might be a drug candidate for DCS prevention and treatment. PMID:28112272

  1. 2014 Decompression Sickness/Extravehicular Activity Risks Standing Review Panel

    NASA Technical Reports Server (NTRS)

    Steinberg, Susan

    2015-01-01

    The 2014 Decompression Sickness (DCS)/Extravehicular Activity (EVA) Risks Standing Review Panel (from here on referred to as the SRP) met for a site visit in Houston, TX on November 4 - 5, 2014. The SRP reviewed the updated Evidence Reports for The Risk of Decompression Sickness (from here on referred to as the 2014 DCS Evidence Report) and the Risk of Injury and Compromised Performance due to EVA Operations (from here on referred to as the 2014 EVA Evidence Report), as well as the Research Plans for these Risks. The SRP appreciated the time and effort that the DCS and EVA disciplines put into their review documents and presentations. The SRP felt that the 2014 DCS Evidence Report and the 2014 EVA Evidence Reports were very thorough and addressed the majority of the known DCS and EVA issues. The researchers at NASA Johnson Space Center (JSC) have the knowledge base to deal with the DCS and EVA issues. Overall, the SRP thinks the DCS and EVA research teams have compiled excellent reports which address the majority of the literature and background information.

  2. The mechanics of decompressive craniectomy: Bulging in idealized geometries

    NASA Astrophysics Data System (ADS)

    Weickenmeier, Johannes; Kuhl, Ellen; Goriely, Alain

    2016-11-01

    In extreme cases of traumatic brain injury or a stroke, the resulting uncontrollable swelling of the brain may lead to a harmful increase of the intracranial pressure. As a common measure for immediate release of pressure on the brain, part of the skull is surgically removed allowing for the brain to bulge outwards, a procedure known as a decompressive craniectomy. During this excessive brain swelling, the affected tissue typically undergoes large deformations resulting in a complex three-dimensional mechanical loading state with several important implications on optimal treatment strategies and outcome. Here, as a first step towards a better understanding of the mechanics of a decompressive craniectomy, we consider simple models for the bulging of elastic solids under geometric constraints representative of the surgical intervention. In small deformations and simple geometries, the exact solution of this problem is derived from the theory of contact mechanics. The analysis of these solutions reveals a number of interesting generic features relevant for the mechanics of craniectomy.

  3. Gender not a factor for altitude decompression sickness risk

    NASA Technical Reports Server (NTRS)

    Webb, James T.; Kannan, Nandini; Pilmanis, Andrew A.

    2003-01-01

    INTRODUCTION: Early, retrospective reports of the incidence of altitude decompression sickness (DCS) during altitude chamber training exposures indicated that women were more susceptible than men. We hypothesized that a controlled, prospective study would show no significant difference. METHODS: We conducted 25 altitude chamber decompression exposure profiles. A total of 291 human subjects, 197 men and 94 women, underwent 961 exposures to simulated altitude for up to 8 h, using zero to 4 h of preoxygenation. Throughout the exposures, subjects breathed 100% oxygen, rested or performed mild or strenuous exercise, and were monitored for precordial venous gas emboli (VGE) and DCS symptoms. RESULTS: No significant differences in DCS incidence were observed between men (49.5%) and women (45.3%). However, VGE occurred at significantly higher rates among men than women under the same exposure conditions, 69.3% and 55.0% respectively. Women using hormonal contraception showed significantly greater susceptibility to DCS than those not using hormonal contraception during the latter two weeks of the menstrual cycle. Significantly higher DCS incidence was observed in the heaviest men, in women with the highest body fat, and in subjects with the highest body mass indices and lowest levels of fitness. CONCLUSION: No differences in altitude DCS incidence were observed between the sexes under our test conditions, although men developed VGE more often than women. Age and height showed no significant influence on DCS incidence, but persons of either sex with higher body mass index and lower physical fitness developed DCS more frequently.

  4. Neuroprotective role of the TREK-1 channel in decompression sickness.

    PubMed

    Vallee, Nicolas; Meckler, Cédric; Risso, Jean-Jacques; Blatteau, Jean-Eric

    2012-04-01

    Nitrogen supersaturation and bubble formation can occur in the vascular system after diving, leading to death and nervous disorders from decompression sickness (DCS). Bubbles alter the vascular endothelium, activate platelets, and lead to focal ischemia with neurological damage mediated by the mechanosensitive TREK-1 neuronal potassium ion channel that sets pre- and postsynaptic resting membrane potentials. We report a neuroprotective effect associated with TREK-1. C57Bl6 mice were subjected to decompression from a simulated 90 msw dive. Of 143 mice that were wild type (WT) for TREK-1, 51.7% showed no DCS, 27.3% failed a grip test, and 21.0% died. Of 88 TREK-1 knockouts (KO), 26.1% showed no DCS, 42.0% failed a grip test, and 31.8% died. Mice that did not express TREK-1 had lower DCS resistance and were more likely to develop neurological symptoms. We conclude that the TREK-1 potassium channel was neuroprotective for DCS.

  5. Transesophageal Echocardiographic Study of Decompression-Induced Venous Gas Emboli

    NASA Technical Reports Server (NTRS)

    Butler, B. D.; Morris, W. P.

    1995-01-01

    Transesophageal echo-cardiography was used to evaluate venous bubbles produced in nine anesthetized dogs following decompression from 2.84 bar after 120 min at pressure. In five dogs a pulsed Doppler cuff probe was placed around the inferior vena cava for bubble grade determination. The transesophageal echo images demonstrated several novel or less defined events. In each case where the pulmonary artery was clearly visualized, the venous bubbles were seen to oscillate back and forth several times, bringing into question the effect of coincidental counting in routine bubble grade analysis using precordial Doppler. A second finding was that in all cases, extensive bubbling occurred in the portal veins with complete extraction by the liver sinusoids, with one exception where a portal-to-hepatic venous anastomosis was observed. Compression of the bowel released copious numbers of bubbles into the portal veins, sometimes more than were released into the inferior vena cava. Finally, large masses of foam were routinely observed in the non-dependent regions of the inferior vena cava that not only delayed the appearance of bubbles in the pulmonary artery but also allowed additional opportunity for further reaction with blood products and for coalescence to occur before reaching the pulmonary microcirculation. These novel observations are discussed in relation to the decompression process.

  6. Relative decompression risk of dry and wet chamber air dives.

    PubMed

    Weathersby, P K; Survanshi, S S; Nishi, R Y

    1990-07-01

    The difference in risk of decompression sickness (DCS) between dry chamber subjects and wet, working divers is unknown and a direct test of the difference would be large and expensive. We used probabilistic models and maximum likelihood estimation to examine 797 dry (and generally resting and comfortable) and 244 wet (and generally working and cold) chamber dives from the Defence and Civil Institute of Environmental Medicine, supplemented with 483 wet (working, cold) dives from the Navy Experimental Diving Unit. Several analyses considered whether dry and wet data were distinguishable using several models, whether models obtained from one set of exposure conditions would correctly predict the occurrence of DCS in the other condition, and whether a single wet-dry risk difference parameter was different from zero. Although the two conditions may not produce identical risks, immersion appears to change relative risk of DCS by less than 30% and certainly involves less than a doubling of DCS risk. Uncontrolled differences in exercise and temperature stresses unavoidably complicate interpretation. Several methods are presented to extrapolate results from dry-test subjects in decompression trials to expected at-sea performance.

  7. Shortcuts to adiabaticity in a time-dependent box

    PubMed Central

    Campo, A. del; Boshier, M. G.

    2012-01-01

    A method is proposed to drive an ultrafast non-adiabatic dynamics of an ultracold gas trapped in a time-dependent box potential. The resulting state is free from spurious excitations associated with the breakdown of adiabaticity, and preserves the quantum correlations of the initial state up to a scaling factor. The process relies on the existence of an adiabatic invariant and the inversion of the dynamical self-similar scaling law dictated by it. Its physical implementation generally requires the use of an auxiliary expulsive potential. The method is extended to a broad family of interacting many-body systems. As illustrative examples we consider the ultrafast expansion of a Tonks-Girardeau gas and of Bose-Einstein condensates in different dimensions, where the method exhibits an excellent robustness against different regimes of interactions and the features of an experimentally realizable box potential. PMID:22970340

  8. Adiabatic circular polarizer based on chiral fiber grating.

    PubMed

    Yang, Li; Xue, Lin-Lin; Li, Cheng; Su, Jue; Qian, Jing-Ren

    2011-01-31

    Based on the adiabatic coupling principle, a new scheme of a broadband circular polarizer formed by twisting a high-birefringence (Hi-Bi) fiber with a slowly varying twist rate is proposed. The conditions of adiabatic coupling for the adiabatic polarizer are first identified through analytical derivations. These conditions are easily realized by choosing a reasonable variation of the twist rate. Moreover, the bandwidth of the polarizer is able to be directly determined by the twist rates at the two ends. Finally, the broadband characteristics of the polarizer are demonstrated by simulations. It is also shown that the performance of the polarizer can be remarkably improved by accomplishing a multi-mode phase-matching along the grating or by using of the couplings of the core mode to lossy modes.

  9. Effect of dephasing on stimulated Raman adiabatic passage

    SciTech Connect

    Ivanov, P.A.; Vitanov, N.V.; Bergmann, K.

    2004-12-01

    This work explores the effect of phase relaxation on the population transfer efficiency in stimulated Raman adiabatic passage (STIRAP). The study is based on the Liouville equation, which is solved analytically in the adiabatic limit. The transfer efficiency of STIRAP is found to decrease exponentially with the dephasing rate; this effect is stronger for shorter pulse delays and weaker for larger delays, since the transition time is found to be inversely proportional to the pulse delay. Moreover, it is found that the transfer efficiency of STIRAP in the presence of dephasing does not depend on the peak Rabi frequencies at all, as long as they are sufficiently large to enforce adiabatic evolution; hence increasing the field intensity cannot reduce the dephasing losses. It is shown also that for any dephasing rate, the final populations of the initial state and the intermediate state are equal. For strong dephasing all three populations tend to (1/3)

  10. Applications of chirped Raman adiabatic rapid passage to atom interferometry

    NASA Astrophysics Data System (ADS)

    Kotru, Krish; Butts, David L.; Kinast, Joseph M.; Johnson, David M. S.; Radojevic, Antonije M.; Timmons, Brian P.; Stoner, Richard E.

    2012-02-01

    We present robust atom optics, based on chirped Raman adiabatic rapid passage (ARP), in the context of atom interferometry. Such ARP light pulses drive coherent population transfer between two hyperfine ground states by sweeping the frequency difference of two fixed-intensity optical fields with large single photon detunings. Since adiabatic transfer is less sensitive to atom temperature and non-uniform Raman beam intensity than standard Raman pulses, this approach should improve the stability of atom interferometers operating in dynamic environments. In such applications, chirped Raman ARP may also provide advantages over the previously demonstrated stimulated Raman adiabatic passage (STIRAP) technique, which requires precise modulation of beam intensity and zeroing of the single photon detuning. We demonstrate a clock interferometer with chirped Raman ARP pulses, and compare its stability to that of a conventional Raman pulse interferometer. We also discuss potential improvements to inertially sensitive atom interferometers. Copyright 2011 by The Charles Stark Draper Laboratory, Inc. All rights reserved.

  11. 46 CFR Appendix A to Part 197 - Air No-Decompression Limits

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Air No-Decompression Limits A Appendix A to Part 197... STANDARDS GENERAL PROVISIONS Pt. 197, App. A Appendix A to Part 197—Air No-Decompression Limits The... within any 12-hour period. The limit is the maximum bottom time in minutes that a diver can spend at...

  12. 46 CFR Appendix A to Part 197 - Air No-Decompression Limits

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Air No-Decompression Limits A Appendix A to Part 197... STANDARDS GENERAL PROVISIONS Pt. 197, App. A Appendix A to Part 197—Air No-Decompression Limits The... within any 12-hour period. The limit is the maximum bottom time in minutes that a diver can spend at...

  13. Arthroscopic core decompression of the lunate in early stage Kienbock disease of the lunate.

    PubMed

    Bain, Gregory I; Smith, Michael L; Watts, Adam C

    2011-03-01

    Since the first description of Kienbock disease in 1910, the etiology and treatment have remained controversial topics. Core decompression is an accepted treatment option in early-stage avascular necrosis of the femoral head, and more recently the humeral head. This paper reports the technique of arthroscopic fluoroscopically guided core decompression of the lunate with 6-year results.

  14. 46 CFR Appendix A to Part 197 - Air No-Decompression Limits

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Air No-Decompression Limits A Appendix A to Part 197... STANDARDS GENERAL PROVISIONS Pt. 197, App. A Appendix A to Part 197—Air No-Decompression Limits The... within any 12-hour period. The limit is the maximum bottom time in minutes that a diver can spend at...

  15. Numerical Investigation of the effect of adiabatic section location on thermal performance of a heat pipe network with the application in thermal energy storage systems

    NASA Astrophysics Data System (ADS)

    Mahdavi, Mahboobe; Tiari, Saeed; Qiu, Songgang

    2015-11-01

    Latent heat thermal energy storage systems benefits from high energy density and isothermal storing process. However, the low thermal conductivity of the phase change material leads to prolong the melting or solidification time. Using a passive device such as heat pipes is required to enhance the heat transfer and to improve the efficiency of the system. In the present work, the performance of a heat pipe network specifically designed for a thermal energy storage system is studied numerically. The network includes a primary heat pipe, which transfers heat received from solar receiver to the heat engine. The excess heat is simultaneously delivered to charge the phase change material via secondary heat pipes. The primary heat pipe composed of a disk shape evaporator, an adiabatic section and a disk shape condenser. The adiabatic section can be either located at the center or positioned outward to the surrounding of the container. Here, the effect of adiabatic section position on thermal performance of the system is investigated. It was concluded that displacing the adiabatic section outwards dramatically increases the average temperatures of the condensers and reduces the thermal resistance of heat pipes.

  16. Adiabatic Pseudospectral Technique: Applications to Four Atom Molecules

    NASA Astrophysics Data System (ADS)

    Antikainen, Jyrki Tapio

    1995-01-01

    After the introduction, in chapter 2 we review some of the well established techniques used to solve the Schrodinger equation. The following methods are discussed: the Finite Basis Representation, the Discrete Variable Representation, the Basic Light basis set truncation, and the Lanczos tridiagonalization. After reviewing the previous techniques we present the main features of our Adiabatic Pseudospectral (APS) technique. The Adiabatic Pseudospectral technique is a synthesis of several powerful computational methods such as the sequential adiabatic basis set reduction, the iterative Lanczos diagonalization, the collocation techniques, and a careful implementation of the matrix -vector product for the Hamiltonian in the reduced adiabatic representation. In chapter 3 we use our adiabatic pseudospectral method (APS) to calculate energy levels of the H _2O_2 molecule up to 5000 cm ^{-1}. Reasonably high accuracy (a few wavenumbers) is achieved for a fully six dimensional calculation in a few hours of CPU time on an IBM 580 workstation. These results are a great improvement over previous calculations on the same system which required 50-100 times more computational effort for a similar level of accuracy. The method presented here is both general and robust. It will allow for routine studies of six dimensional potential surfaces and the associated spectroscopy, while making calculations on still larger systems feasible. In chapter 4 the adiabatic pseudospectral method is used to study the high energy vibrational levels of the H_2C_2 molecule. We calculate stimulated emission pumping spectra initialized by the excited electronic state vibrational trans-bent state ~ A_sp{u}{1 }3_{nu}_3 . The calculations show that with the APS-method we can easily investigate energy regions in the excess of 15,000 cm^{-1}; these high energy regions have been previously unattainable by computational techniques.

  17. Spatial adiabatic passage: a review of recent progress

    NASA Astrophysics Data System (ADS)

    Menchon-Enrich, R.; Benseny, A.; Ahufinger, V.; Greentree, A. D.; Busch, Th; Mompart, J.

    2016-07-01

    Adiabatic techniques are known to allow for engineering quantum states with high fidelity. This requirement is currently of large interest, as applications in quantum information require the preparation and manipulation of quantum states with minimal errors. Here we review recent progress on developing techniques for the preparation of spatial states through adiabatic passage, particularly focusing on three state systems. These techniques can be applied to matter waves in external potentials, such as cold atoms or electrons, and to classical waves in waveguides, such as light or sound.

  18. Quantum dynamics by the constrained adiabatic trajectory method

    SciTech Connect

    Leclerc, A.; Jolicard, G.; Guerin, S.; Killingbeck, J. P.

    2011-03-15

    We develop the constrained adiabatic trajectory method (CATM), which allows one to solve the time-dependent Schroedinger equation constraining the dynamics to a single Floquet eigenstate, as if it were adiabatic. This constrained Floquet state (CFS) is determined from the Hamiltonian modified by an artificial time-dependent absorbing potential whose forms are derived according to the initial conditions. The main advantage of this technique for practical implementation is that the CFS is easy to determine even for large systems since its corresponding eigenvalue is well isolated from the others through its imaginary part. The properties and limitations of the CATM are explored through simple examples.

  19. Adiabatic regularisation of power spectra in k-inflation

    SciTech Connect

    Alinea, Allan L.; Kubota, Takahiro; Nakanishi, Yukari; Naylor, Wade E-mail: kubota@celas.osaka-u.ac.jp E-mail: naylor@phys.sci.osaka-u.ac.jp

    2015-06-01

    We look at the question posed by Parker et al. about the effect of UV regularisation on the power spectrum for inflation. Focusing on the slow-roll k-inflation, we show that up to second order in the Hubble and sound flow parameters, the adiabatic regularisation of such model leads to no difference in the power spectrum apart from certain cases that violate near scale-invariant power spectra. Furthermore, extending to non-minimal k-inflation, we establish the equivalence of the subtraction terms in the adiabatic regularisation of the power spectrum in Jordan and Einstein frames.

  20. Dynamics with the effective adiabatic theory: The Bloch equations

    NASA Astrophysics Data System (ADS)

    Carmeli, Benny; Chandler, David

    1988-07-01

    This paper extends our earlier work on the effective adiabatic theory [J. Chem. Phys. 82, 3400 (1985)] to study relaxation of a two-level system coupled to a Gaussian dissipative bath—the spin-boson problem. Bloch equations are derived which, under the limited circumstances described herein, treat the role of bath fluctuations omitted in the equilibrium effective adiabatic reference system. Applications to the Lorentzian dissipative bath show that the theory agrees closely with numerical simulation results. Application to an Ohmic bath shows that the theory is in agreement with currently accepted results concerned with the problem of macroscopic quantum coherence.

  1. Adiabatic State Conversion and Pulse Transmission in Optomechanical Systems

    NASA Astrophysics Data System (ADS)

    Tian, Lin

    2012-04-01

    Optomechanical systems with strong coupling can be a powerful medium for quantum state engineering of the cavity modes. Here, we show that quantum state conversion between cavity modes of distinctively different wavelengths can be realized with high fidelity by adiabatically varying the effective optomechanical couplings. The conversion fidelity for Gaussian states is derived by solving the Langevin equation in the adiabatic limit. Meanwhile, we also show that traveling photon pulses can be transmitted between different input and output channels with high fidelity and the output pulse can be engineered via the optomechanical couplings.

  2. Gravitational Chern-Simons and the adiabatic limit

    SciTech Connect

    McLellan, Brendan

    2010-12-15

    We compute the gravitational Chern-Simons term explicitly for an adiabatic family of metrics using standard methods in general relativity. We use the fact that our base three-manifold is a quasiregular K-contact manifold heavily in this computation. Our key observation is that this geometric assumption corresponds exactly to a Kaluza-Klein Ansatz for the metric tensor on our three-manifold, which allows us to translate our problem into the language of general relativity. Similar computations have been performed by Guralnik et al.[Ann. Phys. 308, 222 (2008)], although not in the adiabatic context.

  3. Craniocervical spinal instability after type 1 Arnold Chiari decompression: a case report.

    PubMed

    Camino Willhuber, Gaston O; Bosio, Santiago T; Puigdevall, Miguel H; Halliburton, Carolina; Sola, Carlos A; Maenza, Ruben A

    2017-01-01

    To present and describe an unusual case of spinal instability after craniocervical spinal decompression for a type-1 Chiari malformation. Type-1 Chiari malformation is a craniocervical disorder characterized by tonsillar displacement greater than 5 mm into the vertebral canal; posterior fossa decompression is the most common surgical treatment for this condition. Postoperative complications have been described: cerebrospinal fluid leak, pseudomeningocele, aseptic meningitis, wound infection, and neurological deficit. However, instability after decompression is unusual. A 9-year-old female presented with symptomatic torticollis after cervical decompression for a type-1 Chiari malformation. Spinal instability was diagnosed; craniocervical stabilization was performed. After a 12-month follow-up, spinal stability was achieved, with a satisfactory clinical neck alignment. We present a craniocervical instability secondary to surgical decompression; clinical and radiological symptoms, and definitive treatment were described.

  4. The effect of extended O2 prebreathing on altitude decompression sickness and venous gas bubbles

    NASA Technical Reports Server (NTRS)

    Waligora, James M.; Horrigan, David J.; Conkin, Johnny

    1987-01-01

    The purpose of this study was to determine the effect of extended O2 prebreathing on symptom and bubble incidence during decompressions simulating extravehicular activity. The 38 subjects breathed O2 for a 6-hr period prior to decompression to 4.3 psi. The subjects performed upper body exercises for 6 hr. Eight subjects were exposed to the same protocol after an 8-hr prebreathe. Venous bubbles were detected in 18 of 38 subjects decompressed after the 6-hr prebreathe. Four of these subjects reported symptoms of altitude decompression sickness. No symptoms or bubbles were detected in the eight subjects who had prebreathed 8 hr. The incidence of symptoms and bubbles, when combined with prior data on 3.5- and 4.0-hr prebreathes, showed an inverse correlation to prebreathing time. The incidence of symptoms was higher than has been reported for subjects exposed to decompression of shorter duration with less activity.

  5. Experimental petrology of the ultramafic lavas remotely sensed on the surface of Mercury: Constraints on melting and differentiation of Mercury's mantle (Invited)

    NASA Astrophysics Data System (ADS)

    Grove, T. L.; Charlier, B.; Zuber, M. T.; Brown, S. M.

    2013-12-01

    The orbiting MESSENGER spacecraft has measured major element ratios using x-ray fluorescence spectra. These ratios can be used to calculate absolute abundances of the major oxide components in the lavas exposed on the surface of Mercury. The first compositional data reported by Nittler (2011, Science 333, 1847-50) represented large areas of mixed high-reflectance volcanic plains and low-reflectance materials and did not include the northern volcanic plains. These large area measurements reveal high MgO, high SiO2 and low FeO lavas that are most similar to terrestrial volcanic rocks known as basaltic komatiites. Two compositional groups are distinguished by the presence or absence of a clinopyroxene component. Continued measurement of smaller areas on the surface (Weider et al., 2012, JGR 117, E00L05) confirms the existence of two groups. Melting experiments at one atmosphere on the average compositions of each of the two groups were performed to provide constraints on melting and crystallization processes. The two compositional groups cannot be related to each other by any fractional crystallization process at any pressure within the silicate interior of Mercury. This result suggests that the silicate interior of Mercury contains differentiated source regions. One possibility for development of distinctive source regions is early multi-stage differentiation and remelting processes in Mercury's interior. Magma ocean crystallization followed by adiabatic decompression of the differentiated cumulate layers during post magma ocean overturn and/or convection could lead to conditions that would be adequate to cause melting and volcanism that is preserved in the surface lavas. High-pressure phase equilibria on compositional systems similar to the Mercury lavas supports partial melting at pressures > 1 GPa if the Na detected by gamma ray spectroscopy is assumed to be included in the surface lavas. This depth corresponds to equilibration of the melts close to the crust

  6. An old model in a new perspective: The dynamic melting column and its application in intracontinental basalt petrogenesis

    NASA Astrophysics Data System (ADS)

    Taracsák, Zoltán; Molnár, Gábor; Harangi, Szabolcs

    2016-04-01

    Basaltic melt generation has been thought to be a simple process, involving distinct and well-defined melt batches generated in the asthenosphere or in the lithospheric mantle. However in the last decade, it became clear that complex processes including magma mixing from several sources may take place during magma generation, therefore single melting models might not be able to describe the melting process properly. We suggest that a trace element based melting column model assuming step by-step, dynamic melting caused by decompression would be a good estimation of how the mantle melts in intracontinental settings. This model makes it possible to assume a heterogeneous mantle source by adding melting cells with different composition and mineralogy, and can handle changes in bulk distribution coefficients caused by phase transitions for example the spinel-garnet transition in the upper mantle. If the uppermost part of the melting column reaches the stability of spinel, partitioning of rare earth elements (REEs) change drastically, as heavy REEs are compatible in the garnet stability field during melting while moderately incompatible in depths where spinel is stable. This way, trace element concentrations in primitive basalts can provide information on melting depth. This depth can be quantified with the step-by-step dynamic melting column model if the geotherm or the potential temperature is known. This way the depth of the spinel-garnet transition will be definable. We assume that melting beneath intracontinental volcanic fields is limited to the asthenosphere, and that the top of the melting column will represent the lithosphere-asthenosphere boundary (LAB). To test our model, we calculated lithospheric thicknesses for four Neogene-Quarternary basaltic volcanic fields from the Pannonian Basin, East Central Europe. Our results indicate slightly different LAB depths compared to previous, major element based calculations (Harangi et al., Int J Earth Sci, 2015).

  7. Plants survive rapid decompression: Implications for bioregenerative life support

    NASA Astrophysics Data System (ADS)

    Wheeler, R. M.; Wehkamp, C. A.; Stasiak, M. A.; Dixon, M. A.; Rygalov, V. Y.

    2011-05-01

    Radish (Raphanus sativus), lettuce (Latuca sativa), and wheat (Triticum aestivum) plants were grown at either 98 kPa (ambient) or 33 kPa atmospheric pressure with constant 21 kPa oxygen and 0.12 kPa carbon dioxide in atmospherically closed pressure chambers. All plants were grown rockwool using recirculating hydroponics with a complete nutrient solution. At 20 days after planting, chamber pressures were pumped down as rapidly as possible, reaching 5 kPa after about 5 min and ˜1.5 kPa after about 10 min. The plants were held at 1.5 kPa for 30 min and then pressures were restored to their original settings. Temperature (22 °C) and humidity (65% RH) controls were engaged throughout the depressurization, although temperatures dropped to near 16 °C for a brief period. CO2 and O2 were not detectable at the low pressure, suggesting that most of the 1.5 kPa atmosphere consisted of water vapor. Following re-pressurization, plants were grown for another 7 days at the original pressures and then harvested. The lettuce, radish, and wheat plants showed no visible effects from the rapid decompression, and there were no differences in fresh or dry mass when compared to control plants maintained continuously at 33 or 98 kPa. But radish storage root fresh mass and lettuce head fresh and dry masses were less at 33 kPa compared to 98 kPa for both the controls and decompression treatment. The results suggest that plants are extremely resilient to rapid decompression, provided they do not freeze (from evaporative cooling) or desiccate. The water of the hydroponic system was below the boiling pressure during these tests and this may have protected the plants by preventing pressures from dropping below 1.5 kPa and maintaining humidity near 1.5 kPa. Further testing is needed to determine how long plants can withstand such low pressure, but the results suggest there are at least 30 min to respond to catastrophic pressure losses in a plant production chamber that might be used for life

  8. Trial of Decompressive Craniectomy for Traumatic Intracranial Hypertension.

    PubMed

    Hutchinson, Peter J; Kolias, Angelos G; Timofeev, Ivan S; Corteen, Elizabeth A; Czosnyka, Marek; Timothy, Jake; Anderson, Ian; Bulters, Diederik O; Belli, Antonio; Eynon, C Andrew; Wadley, John; Mendelow, A David; Mitchell, Patrick M; Wilson, Mark H; Critchley, Giles; Sahuquillo, Juan; Unterberg, Andreas; Servadei, Franco; Teasdale, Graham M; Pickard, John D; Menon, David K; Murray, Gordon D; Kirkpatrick, Peter J

    2016-09-22

    Background The effect of decompressive craniectomy on clinical outcomes in patients with refractory traumatic intracranial hypertension remains unclear. Methods From 2004 through 2014, we randomly assigned 408 patients, 10 to 65 years of age, with traumatic brain injury and refractory elevated intracranial pressure (>25 mm Hg) to undergo decompressive craniectomy or receive ongoing medical care. The primary outcome was the rating on the Extended Glasgow Outcome Scale (GOS-E) (an 8-point scale, ranging from death to "upper good recovery" [no injury-related problems]) at 6 months. The primary-outcome measure was analyzed with an ordinal method based on the proportional-odds model. If the model was rejected, that would indicate a significant difference in the GOS-E distribution, and results would be reported descriptively. Results The GOS-E distribution differed between the two groups (P<0.001). The proportional-odds assumption was rejected, and therefore results are reported descriptively. At 6 months, the GOS-E distributions were as follows: death, 26.9% among 201 patients in the surgical group versus 48.9% among 188 patients in the medical group; vegetative state, 8.5% versus 2.1%; lower severe disability (dependent on others for care), 21.9% versus 14.4%; upper severe disability (independent at home), 15.4% versus 8.0%; moderate disability, 23.4% versus 19.7%; and good recovery, 4.0% versus 6.9%. At 12 months, the GOS-E distributions were as follows: death, 30.4% among 194 surgical patients versus 52.0% among 179 medical patients; vegetative state, 6.2% versus 1.7%; lower severe disability, 18.0% versus 14.0%; upper severe disability, 13.4% versus 3.9%; moderate disability, 22.2% versus 20.1%; and good recovery, 9.8% versus 8.4%. Surgical patients had fewer hours than medical patients with intracranial pressure above 25 mm Hg after randomization (median, 5.0 vs. 17.0 hours; P<0.001) but had a higher rate of adverse events (16.3% vs. 9.2%, P=0.03). Conclusions At 6

  9. Adiabatic frequency conversion with a sign flip in the coupling

    NASA Astrophysics Data System (ADS)

    Hristova, H. S.; Rangelov, A. A.; Montemezzani, G.; Vitanov, N. V.

    2016-09-01

    Adiabatic frequency conversion is a method recently developed in nonlinear optics [H. Suchowski, D. Oron, A. Arie, and Y. Silberberg, Phys. Rev. A 78, 063821 (2008), 10.1103/PhysRevA.78.063821], using ideas from the technique of rapid adiabatic passage (RAP) via a level crossing in quantum physics. In this method, the coupling coefficients are constant and the phase mismatch is chirped adiabatically. In this work, we propose another method for adiabatic frequency conversion, in which the phase mismatch is constant and the coupling is a pulse-shaped function with a sign flip (i.e., a phase step of π ) at its maximum. Compared to the RAP method, our technique has comparable efficiency but it is simpler to implement for it only needs two bulk crystals with opposite χ(2 ) nonlinearity. Moreover, because our technique requires constant nonzero frequency mismatch and has zero conversion efficiency on exact frequency matching, it can be used as a frequency filter.

  10. Failure of geometric electromagnetism in the adiabatic vector Kepler problem

    SciTech Connect

    Anglin, J.R.; Schmiedmayer, J.

    2004-02-01

    The magnetic moment of a particle orbiting a straight current-carrying wire may precess rapidly enough in the wire's magnetic field to justify an adiabatic approximation, eliminating the rapid time dependence of the magnetic moment and leaving only the particle position as a slow degree of freedom. To zeroth order in the adiabatic expansion, the orbits of the particle in the plane perpendicular to the wire are Keplerian ellipses. Higher-order postadiabatic corrections make the orbits precess, but recent analysis of this 'vector Kepler problem' has shown that the effective Hamiltonian incorporating a postadiabatic scalar potential ('geometric electromagnetism') fails to predict the precession correctly, while a heuristic alternative succeeds. In this paper we resolve the apparent failure of the postadiabatic approximation, by pointing out that the correct second-order analysis produces a third Hamiltonian, in which geometric electromagnetism is supplemented by a tensor potential. The heuristic Hamiltonian of Schmiedmayer and Scrinzi is then shown to be a canonical transformation of the correct adiabatic Hamiltonian, to second order. The transformation has the important advantage of removing a 1/r{sup 3} singularity which is an artifact of the adiabatic approximation.

  11. Fast Quasi-Adiabatic Gas Cooling: An Experiment Revisited

    ERIC Educational Resources Information Center

    Oss, S.; Gratton, L. M.; Calza, G.; Lopez-Arias, T.

    2012-01-01

    The well-known experiment of the rapid expansion and cooling of the air contained in a bottle is performed with a rapidly responsive, yet very cheap thermometer. The adiabatic, low temperature limit is approached quite closely and measured with our apparatus. A straightforward theoretical model for this process is also presented and discussed.…

  12. Adiabatic compression and radiative compression of magnetic fields

    SciTech Connect

    Woods, C.H.

    1980-02-12

    Flux is conserved during mechanical compression of magnetic fields for both nonrelativistic and relativistic compressors. However, the relativistic compressor generates radiation, which can carry up to twice the energy content of the magnetic field compressed adiabatically. The radiation may be either confined or allowed to escape.

  13. Digitized adiabatic quantum computing with a superconducting circuit.

    PubMed

    Barends, R; Shabani, A; Lamata, L; Kelly, J; Mezzacapo, A; Las Heras, U; Babbush, R; Fowler, A G; Campbell, B; Chen, Yu; Chen, Z; Chiaro, B; Dunsworth, A; Jeffrey, E; Lucero, E; Megrant, A; Mutus, J Y; Neeley, M; Neill, C; O'Malley, P J J; Quintana, C; Roushan, P; Sank, D; Vainsencher, A; Wenner, J; White, T C; Solano, E; Neven, H; Martinis, John M

    2016-06-09

    Quantum mechanics can help to solve complex problems in physics and chemistry, provided they can be programmed in a physical device. In adiabatic quantum computing, a system is slowly evolved from the ground state of a simple initial Hamiltonian to a final Hamiltonian that encodes a computational problem. The appeal of this approach lies in the combination of simplicity and generality; in principle, any problem can be encoded. In practice, applications are restricted by limited connectivity, available interactions and noise. A complementary approach is digital quantum computing, which enables the construction of arbitrary interactions and is compatible with error correction, but uses quantum circuit algorithms that are problem-specific. Here we combine the advantages of both approaches by implementing digitized adiabatic quantum computing in a superconducting system. We tomographically probe the system during the digitized evolution and explore the scaling of errors with system size. We then let the full system find the solution to random instances of the one-dimensional Ising problem as well as problem Hamiltonians that involve more complex interactions. This digital quantum simulation of the adiabatic algorithm consists of up to nine qubits and up to 1,000 quantum logic gates. The demonstration of digitized adiabatic quantum computing in the solid state opens a path to synthesizing long-range correlations and solving complex computational problems. When combined with fault-tolerance, our approach becomes a general-purpose algorithm that is scalable.

  14. Cosmological solutions in spatially curved universes with adiabatic particle production

    NASA Astrophysics Data System (ADS)

    Aresté Saló, Llibert; de Haro, Jaume

    2017-03-01

    We perform a qualitative and thermodynamic study of two models when one takes into account adiabatic particle production. In the first one, there is a constant particle production rate, which leads to solutions depicting the current cosmic acceleration but without inflation. The other one has solutions that unify the early and late time acceleration. These solutions converge asymptotically to the thermal equilibrium.

  15. A Kinetic Study of the Adiabatic Polymerization of Acrylamide.

    ERIC Educational Resources Information Center

    Thomson, R. A. M.

    1986-01-01

    Discusses theory, procedures, and results for an experiment which demonstrates the application of basic physics to chemical problems. The experiment involves the adiabatic process, in which polymerization carried out in a vacuum flask is compared to the theoretical prediction of the model with the temperature-time curve obtained in practice. (JN)

  16. Reversibility and energy dissipation in adiabatic superconductor logic.

    PubMed

    Takeuchi, Naoki; Yamanashi, Yuki; Yoshikawa, Nobuyuki

    2017-12-01

    Reversible computing is considered to be a key technology to achieve an extremely high energy efficiency in future computers. In this study, we investigated the relationship between reversibility and energy dissipation in adiabatic superconductor logic. We analyzed the evolution of phase differences of Josephson junctions in the reversible quantum-flux-parametron (RQFP) gate and confirmed that the phase differences can change time reversibly, which indicates that the RQFP gate is physically, as well as logically, reversible. We calculated energy dissipation required for the RQFP gate to perform a logic operation and numerically demonstrated that the energy dissipation can fall below the thermal limit, or the Landauer bound, by lowering operation frequencies. We also investigated the 1-bit-erasure gate as a logically irreversible gate and the quasi-RQFP gate as a physically irreversible gate. We calculated the energy dissipation of these irreversible gates and showed that the energy dissipation of these gate is dominated by non-adiabatic state changes, which are induced by unwanted interactions between gates due to logical or physical irreversibility. Our results show that, in reversible computing using adiabatic superconductor logic, logical and physical reversibility are required to achieve energy dissipation smaller than the Landauer bound without non-adiabatic processes caused by gate interactions.

  17. Adiabatic State Conversion and Photon Transmission in Optomechanical Systems

    NASA Astrophysics Data System (ADS)

    Tian, Lin

    2012-02-01

    Light-matter interaction in optomechanical systems in the strong coupling regime can be explored as a tool to transfer cavity states and to transmit photon pulses. Here, we show that quantum state conversion between cavity modes with different wavelengths can be realized with high fidelity by adiabatically varying the effective optomechanical couplings. During this adiabatic process, the quantum state is preserved in the dark mode of the cavities, similar to the adiabatic transfer schemes in EIT systems. The fidelity for gaussian states is derived by solving the Langevin equation in the adiabatic limit and shows negligible dependence on the mechanical noise. We also show that an input pulse can be transmitted to an output channel with a different wavelength via the effective optomechanical couplings. The condition for optimal transmission is derived in the frequency domain. Input pulses with a narrow spectral width can be transmitted with high fidelity. For input pulses with a large spectral width, the shape of the output pulses can be manipulated by applying time-dependent effective couplings. (1) L. Tian, arXiv:1111.2119. (2) L. Tian and H. L. Wang, Phys. Rev. A 82, 053806 (2010).

  18. When an Adiabatic Irreversible Expansion or Compression Becomes Reversible

    ERIC Educational Resources Information Center

    Anacleto, Joaquim; Ferreira, J. M.; Soares, A. A.

    2009-01-01

    This paper aims to contribute to a better understanding of the concepts of a "reversible process" and "entropy". For this purpose, an adiabatic irreversible expansion or compression is analysed, by considering that an ideal gas is expanded (compressed), from an initial pressure P[subscript i] to a final pressure P[subscript f], by being placed in…

  19. Dark energy and dark matter from an additional adiabatic fluid

    NASA Astrophysics Data System (ADS)

    Dunsby, Peter K. S.; Luongo, Orlando; Reverberi, Lorenzo

    2016-10-01

    The dark sector is described by an additional barotropic fluid which evolves adiabatically during the Universe's history and whose adiabatic exponent γ is derived from the standard definitions of specific heats. Although in general γ is a function of the redshift, the Hubble parameter and its derivatives, we find that our assumptions lead necessarily to solutions with γ =constant in a Friedmann-Lemaître-Robertson-Walker universe. The adiabatic fluid acts effectively as the sum of two distinct components, one evolving like nonrelativistic matter and the other depending on the value of the adiabatic index. This makes the model particularly interesting as a way of simultaneously explaining the nature of both dark energy and dark matter, at least at the level of the background cosmology. The Λ CDM model is included in this family of theories when γ =0 . We fit our model to supernovae Ia, H (z ) and baryonic acoustic oscillation data, discussing the model selection criteria. The implications for the early Universe and the growth of small perturbations in this model are also discussed.

  20. Non-adiabatic transition probability dependence on conical intersection topography

    NASA Astrophysics Data System (ADS)

    Malhado, João Pedro; Hynes, James T.

    2016-11-01

    We derive a closed form analytical expression for the non-adiabatic transition probability for a distribution of trajectories passing through a generic conical intersection (CI), based on the Landau-Zener equation for the non-adiabatic transition probability for a single straight-line trajectory in the CI's vicinity. We investigate the non-adiabatic transition probability's variation with topographical features and find, for the same crossing velocity, no intrinsic difference in efficiency at promoting non-adiabatic decay between peaked and sloped CIs, a result in contrast to the commonly held view. Any increased efficiency of peaked over sloped CIs is thus due to dynamical effects rather than to any increased transition probability of topographical origin. It is also shown that the transition probability depends in general on the direction of approach to the CI, and that the coordinates' reduced mass can affect the transition probability via its influence on the CI topography in mass-scaled coordinates. The resulting predictions compare well with surface hopping simulation results.

  1. Non-adiabatic transition probability dependence on conical intersection topography.

    PubMed

    Malhado, João Pedro; Hynes, James T

    2016-11-21

    We derive a closed form analytical expression for the non-adiabatic transition probability for a distribution of trajectories passing through a generic conical intersection (CI), based on the Landau-Zener equation for the non-adiabatic transition probability for a single straight-line trajectory in the CI's vicinity. We investigate the non-adiabatic transition probability's variation with topographical features and find, for the same crossing velocity, no intrinsic difference in efficiency at promoting non-adiabatic decay between peaked and sloped CIs, a result in contrast to the commonly held view. Any increased efficiency of peaked over sloped CIs is thus due to dynamical effects rather than to any increased transition probability of topographical origin. It is also shown that the transition probability depends in general on the direction of approach to the CI, and that the coordinates' reduced mass can affect the transition probability via its influence on the CI topography in mass-scaled coordinates. The resulting predictions compare well with surface hopping simulation results.

  2. Digitized adiabatic quantum computing with a superconducting circuit

    NASA Astrophysics Data System (ADS)

    Barends, R.; Shabani, A.; Lamata, L.; Kelly, J.; Mezzacapo, A.; Heras, U. Las; Babbush, R.; Fowler, A. G.; Campbell, B.; Chen, Yu; Chen, Z.; Chiaro, B.; Dunsworth, A.; Jeffrey, E.; Lucero, E.; Megrant, A.; Mutus, J. Y.; Neeley, M.; Neill, C.; O'Malley, P. J. J.; Quintana, C.; Roushan, P.; Sank, D.; Vainsencher, A.; Wenner, J.; White, T. C.; Solano, E.; Neven, H.; Martinis, John M.

    2016-06-01

    Quantum mechanics can help to solve complex problems in physics and chemistry, provided they can be programmed in a physical device. In adiabatic quantum computing, a system is slowly evolved from the ground state of a simple initial Hamiltonian to a final Hamiltonian that encodes a computational problem. The appeal of this approach lies in the combination of simplicity and generality; in principle, any problem can be encoded. In practice, applications are restricted by limited connectivity, available interactions and noise. A complementary approach is digital quantum computing, which enables the construction of arbitrary interactions and is compatible with error correction, but uses quantum circuit algorithms that are problem-specific. Here we combine the advantages of both approaches by implementing digitized adiabatic quantum computing in a superconducting system. We tomographically probe the system during the digitized evolution and explore the scaling of errors with system size. We then let the full system find the solution to random instances of the one-dimensional Ising problem as well as problem Hamiltonians that involve more complex interactions. This digital quantum simulation of the adiabatic algorithm consists of up to nine qubits and up to 1,000 quantum logic gates. The demonstration of digitized adiabatic quantum computing in the solid state opens a path to synthesizing long-range correlations and solving complex computational problems. When combined with fault-tolerance, our approach becomes a general-purpose algorithm that is scalable.

  3. Dissociative melting of ice VII at high pressure

    SciTech Connect

    Goncharov, Alexander F.; Sanloup, Chrystele; Goldman, Nir; Crowhurst, Jonathan C.; Bastea, Sorin; Howard, W.M.; Fried, Laurence E.; Guignot, Nicolas; Mezouar, Mohamed; Meng, Yue

    2009-04-02

    We have used x-ray diffraction to determine the structure factor of water along its melting line to a static pressure of 57 GPa (570 kbar) and a temperature of more than 1500 K, conditions which correspond to the lower mantle of the Earth, and the interiors of Neptune and Uranus up to a depth of 7000 km. We have also performed corresponding first principles and classical molecular dynamics simulations. Above a pressure of 4 GPa the O-O structure factor is found to be very close to that of a simple soft sphere liquid, thus permitting us to determine the density of liquid water near the melting line. By comparing these results with the density of ice, also determined in this study, we find that the enthalpy of fusion ({Delta}H{sub f}) increases enormously along the melting line, reaching approximately 120 kJ/mole at 40 GPa (compared to 6 kJ/mole at 0 GPa), thus revealing significant molecular dissociation of water upon melting. We speculate that an extended two-phase region could occur in planetary processes involving the adiabatic compression of water.

  4. Dissociative melting of ice VII at high pressure

    NASA Astrophysics Data System (ADS)

    Goncharov, Alexander F.; Sanloup, Chrystele; Goldman, Nir; Crowhurst, Jonathan C.; Bastea, Sorin; Howard, W. M.; Fried, Laurence E.; Guignot, Nicolas; Mezouar, Mohamed; Meng, Yue

    2009-03-01

    We have used x-ray diffraction to determine the structure factor of water along its melting line to a static pressure of 57 GPa (570 kbar) and a temperature of more than 1500 K, conditions which correspond to the lower mantle of the Earth, and the interiors of Neptune and Uranus up to a depth of 7000 km. We have also performed corresponding first principles and classical molecular dynamics simulations. Above a pressure of 4 GPa the O-O structure factor is found to be very close to that of a simple soft sphere liquid, thus permitting us to determine the density of liquid water near the melting line. By comparing these results with the density of ice, also determined in this study, we find that the enthalpy of fusion (ΔHf) increases enormously along the melting line, reaching approximately 120 kJ/mole at 40 GPa (compared to 6 kJ/mole at 0 GPa), thus revealing significant molecular dissociation of water upon melting. We speculate that an extended two-phase region could occur in planetary processes involving the adiabatic compression of water.

  5. Transoral decompression and posterior stabilisation in Morquio's disease.

    PubMed Central

    Ashraf, J; Crockard, H A; Ransford, A O; Stevens, J M

    1991-01-01

    A 3.5 year old boy with Morquio's disease was referred with a persisting left hemiparesis four months after a fall and was found to have craniocervical junction compression due to atlantoaxial subluxation and significant anterior soft tissue compression. Transient unconsciousness at the time of the fall was probably due to medullary concussion as a result of hyperextension, not a head injury. Spinal cord compression due to atlantoaxial subluxation at the craniovertebral junction is a major cause of disability and death in these patients. Once cervical myelopathy appears, early posterior occipitocervical fusion has been advocated in order to arrest the progression of neurological disability and this is successful in most cases. This conventional approach was considered unsafe because of the significant anterior compression. A combined anterior transoral decompression with posterior fusion to deal with this particularly difficult problem is described. Images Figure 1 Figure 2 Figure 3 Figure 4 PMID:1755646

  6. The potential role of perfluorocarbon emulsions in decompression illness.

    PubMed

    Spiess, Bruce D

    2010-03-01

    Decompression illness (DCI) is an occasional occurrence in sport, professional, and military diving as well as a potential catastrophe in high-altitude flight, space exploration, mining, and caisson bridge construction. DCI theoretically could be a success-limiting problem in escape from a disabled submarine (DISSUB). Perfluorocarbon emulsions (PFCs) have previously been investigated as 'blood substitutes' with one approved by the United States Food and Drug Administration for the treatment of myocardial ischaemia. PFCs possess enhanced (as compared to plasma) respiratory gas solubility characteristics, including oxygen, nitrogen and carbon dioxide. This review examines approximately 30 years of research regarding the utilization of PFCs in gas embolism as well as experimental DCI. To date, no humans have been treated with PFCs for DCI.

  7. Intra-operative neurophysiology during microvascular decompression for hemifacial spasm.

    PubMed

    Fernández-Conejero, I; Ulkatan, S; Sen, C; Deletis, V

    2012-01-01

    There is evidence that primary hemifacial spasm (HFS) in the majority of patients is related to a vascular compression of the facial nerve at its root exit zone (REZ). As a consequence, the hyperexcitability of facial nerve generates spasms of the facial muscles. Microvascular decompression (MVD) of the facial nerve near its REZ has been established as an effective treatment of HFS. Intra-operative disappearance of abnormal muscle responses (lateral spread) elicited by stimulating one of the facial nerve branches has been used as a method to predict MVD effectiveness. Other neurophysiologic techniques, such as facial F-wave, blink reflex and facial corticobulbar motor evoked potentials (FCoMEP), are feasible to intra-operatively study changes in excitability of the facial nerve and its nucleus during MVDs. Intra-operative neuromonitoring with the mentioned techniques allows a better understanding of HFS pathophysiology and helps to optimise the MVD.

  8. Intravenous Fluid Therapy in Traumatic Brain Injury and Decompressive Craniectomy

    PubMed Central

    Alvis-Miranda, Hernando Raphael; Castellar-Leones, Sandra Milena; Moscote-Salazar, Luis Rafael

    2014-01-01

    The patient with head trauma is a challenge for the emergency physician and for the neurosurgeon. Currently traumatic brain injury constitutes a public health problem. Knowledge of the various supportive therapeutic strategies in the pre-hospital and pre-operative stages is essential for optimal care. The immediate rapid infusion of large volumes of crystalloids to restore blood volume and blood pressure is now the standard treatment of patients with combined traumatic brain injury (TBI) and hemorrhagic shock (HS). The fluid in patients with brain trauma and especially in patients with brain injur y is a critical issue. In this context we present a review of the literature about the history, physiology of current fluid preparations, and a discussion regarding the use of fluid therapy in traumatic brain injury and decompressive craniectomy. PMID:27162857

  9. Global and Local Distortion Inference During Embedded Zerotree Wavelet Decompression

    NASA Technical Reports Server (NTRS)

    Huber, A. Kris; Budge, Scott E.

    1996-01-01

    This paper presents algorithms for inferring global and spatially local estimates of the squared-error distortion measures for the Embedded Zerotree Wavelet (EZW) image compression algorithm. All distortion estimates are obtained at the decoder without significantly compromising EZW's rate-distortion performance. Two methods are given for propagating distortion estimates from the wavelet domain to the spatial domain, thus giving individual estimates of distortion for each pixel of the decompressed image. These local distortion estimates seem to provide only slight improvement in the statistical characterization of EZW compression error relative to the global measure, unless actual squared errors are propagated. However, they provide qualitative information about the asymptotic nature of the error that may be helpful in wavelet filter selection for low bit rate applications.

  10. Low melting mesophase pitches

    SciTech Connect

    Diefendorf, R.J.; Chen, S.H.

    1984-04-17

    A low melting point, low molecular weight, heptane insoluble, 1,2,4-trichlorobenzene soluble mesophase pitch useful in carbon fiber spinning as such or as a plasticizer in a carbon fiber spinning composition is obtained by heating chrysene, triphenylene or paraterphenyl as well as mixtures thereof and hydrocarbon fractions containing the same, dissolving the resulting heat treated material with 1,2,4-trichlorobenzene, and separating the insolubles, and then contacting the 1,2,4-trichlorobenzene soluble fraction with a sufficient amount of heptane to precipitate the low melting point, low molecular weight mesophase pitch.

  11. The Mars Project: Avoiding Decompression Sickness on a Distant Planet

    NASA Technical Reports Server (NTRS)

    Conkin, Johnny

    2000-01-01

    A cost-effective approach for Mars exploration is to use available resources, such as water and atmospheric gases. Nitrogen (N2) and argon (Ar) are available and could form the inert gas component of a habitat atmosphere at 8.0, 9.0, or 10.0 pounds per square inch (psia). The habitat and space suit are designed as an integrated system: a comfortable living environment about 85% of the time and a safe working environment about 15% of the time. A goal is to provide a system that permits unrestricted exploration of Mars, but the risk of decompression sickness (DCS) during the extravehicular activity in a 3.75-psia suit, after exposure to any of the three habitat conditions, may limit unrestricted exploration. I evaluate here the risk of DCS since a significant proportion of a trinary breathing gas in the habitat might contain Ar. I draw on past experience and published information to extrapolate into untested, multivariable conditions to evaluate risk. A rigorous assessment of risk as a probability of DCS for each habitat condition is not yet possible. Based on many assumptions about Ar in hypobaric decompressions, I conclude that the presence of Ar significantly increases the risk of DCS. The risk is significant even with the best habitat option: 2.56 psia oxygen, 3.41 psia N2, and 2.20 psia Ar. Several hours of prebreathing 100% 02, a higher suit pressure, or a combination of other important variables such as limited exposure time on the surface or exercise during prebreathe would be necessary to reduce the risk of DCS to an acceptable level. The acceptable level for DCS risk on Mars has not yet been determined. Mars is a great distance from Earth and therefore from primary medical care. The acceptable risk would necessarily be defined by the capability to treat DCS in the Rover vehicle, in the habitat, or both.

  12. 2014 Decompression Sickness/Extravehicular Activity Risks Standing Review Panel

    NASA Technical Reports Server (NTRS)

    Steinberg, Susan; Mahon, Richard; Klaus, David; Neuman, Tom; Pilmanis, Andrew; Regis, David

    2014-01-01

    The 2014 Decompression Sickness (DCS)/Extravehicular Activity (EVA) Risks Standing Review Panel (from here on referred to as the SRP) met for a site visit in Houston, TX on November 4 - 5, 2014. The SRP reviewed the Research Plans for The Risk of Decompression Sickness and the Risk of Injury and Compromised Performance due to EVA Operations, as well as the Evidence Reports for both of these Risks. The SRP found that the NASA DCS/EVA team did an excellent job of presenting their research plans. The SRP considers it critical that NASA proceeds with the high priority tasks identified in this report (DCS1, DCS3, DCS5). The highest priority is to determine the acceptable DCS and hypoxia risk associated with the planned human exploration beyond low Earth orbit. The risk of DCS is highly dependent upon the pressure within the exploration vehicle. If slightly more hypoxia is permitted then (even with the same percentage of oxygen) the pressure within the exploration vehicle can be lowered thus further mitigating the risk of DCS. The second highest priority is to test and validate the recommended 8.2psi/34% O2 atmosphere. Development of procedures and equipment for human exploration missions are very limited until the results of this testing are completed. The SRP also suggests that DCS7 be separated into two Gaps. Gap DCS7 should deal with DCS treatment while a new Gap should be created to deal with the long-term effects of DCS. The SRP also encourages NASA to increase collaboration with other organizations and pool resources where possible. The current NASA DCS/EVA team has the extensive expertise and a wealth of knowledge in this area. The SRP suggests that increased manpower for this team would be highly productive.

  13. Sub-adiabatic perpendicular electron heating across high-Mach number collisionless shocks

    NASA Astrophysics Data System (ADS)

    Sundkvist, D. J.; Mozer, F.

    2012-12-01

    Spacecraft observations of a high Mach number quasi-perpendicular bow shock with high plasma beta have revealed electrons that were sub-adiabatic through the shock ramp because they were less heated than expected from conservation of the first adiabatic invariant. This stands out in contrast to existing theories of electron heating at collisionless shocks in which the electrons are adiabatically heated through compression or more-than-adiabatically heated due to additional effects such as anomalous resistivity induced by microinstabilites.

  14. Computed chest tomography in an animal model for decompression sickness: radiologic, physiologic, and pathologic findings.

    PubMed

    Reuter, M; Tetzlaff, K; Brasch, F; Gerriets, T; Weiher, M; Struck, N; Hirt, S; Hansen, J; Müller, K M; Heller, M

    2000-01-01

    This study was conducted to investigate the early pulmonary effects of acute decompression in an animal model for human decompression sickness by CT and light microscopy. Ten test pigs were exposed to severe decompression stress in a chamber dive. Three pigs were kept at ambient pressure to serve as controls. Decompression stress was monitored by measurement of pulmonary artery pressure and arterial and venous Doppler recording of bubbles of inert gas. Chest CT was performed pre- and postdive and in addition the inflated lungs were examined after resection. Each lung was investigated by light microscopy. Hemodynamic data and bubble recordings reflected severe decompression stress in the ten test pigs. Computed tomography revealed large quantities of ectopic gas, predominantly intravascular, in three of ten pigs. These findings corresponded to maximum bubble counts in the Doppler study. The remaining test pigs showed lower bubble grades and no ectopic gas by CT. Sporadic interstitial edema was demonstrated in all animals--both test and control pigs--by CT of resected lungs and on histologic examination. A severe compression-decompression schedule can liberate large volumes of inert gas which are detectable by CT. Despite this severe decompression stress, which led to venous microembolism, CT and light microscopy did not demonstrate changes in lung structure related to the experimental dive. Increased extravascular lung water found in all animals may be due to infusion therapy.

  15. Two Portal Percutaneous Endoscopic Decompression for Lumbar Spinal Stenosis: Preliminary Study

    PubMed Central

    Dilokhuttakarn, Thitinut

    2016-01-01

    Study Design Retrospective. Purpose To report the outcomes of patients with lumbar spinal stenosis treated with percutaneous endoscopic decompression, focusing on the results of clinical evaluations. Overview of Literature There are no studies about two portal percutaneous endoscopic decompression in the treatment of lumbar spinal stenosis. Methods Medical and surgical complications were examined and clinical results were analyzed for 30 patients who consecutively underwent two portal percutaneous endoscopic decompression for lumbar spinal stenosis were reviewed. The operations were performed by unilateral laminotomy for bilateral decompression. Results All patients displayed clinical improvement when were evaluated with visual analog scale (VAS) score of pain, Oswestry disability index (ODI) and Macnab criteria. The improvement of VAS and ODI was 8.3±0.7 to 2.3±2.6 and 65.2±13.7 to 24.0±15.5, respectively (both p<0.05). Complications were the same as for open decompression. The most common complication was transient nerve root paresthesia. Conclusions Surgical decompression with two portal percutaneous endoscopic decompression has initial benefits, but long-term studies should pay more attention to the risks of postoperative instability and restenosis as well as the need for re-operation. Further investigations with long-term results are thus required. PMID:27114776

  16. Biomechanical Effects of a Unilateral Approach to Minimally Invasive Lumbar Decompression

    PubMed Central

    Smith, Zachary A.; Vastardis, Georgios A.; Carandang, Gerard; Havey, Robert M.; Hannon, Sean; Dahdaleh, Nader; Voronov, Leonard I.; Fessler, Richard G.; Patwardhan, Avinash G.

    2014-01-01

    Minimally invasive (MI) lumbar decompression became a common approach to treat lumbar stenosis. This approach may potentially mitigate postoperative increases in segmental motion. The goal of this study was to evaluate modifications to segmental motion in the lumbar spine following a MI unilateral approach as compared to traditional facet-sparing and non-facet sparing decompressions. Six human lumbar cadaveric specimens were used. Each specimen was tested in flexion-extension 0 N and 400 N of follower preload), axial rotation, and lateral bending. Each testing condition was evaluated following three separate interventions at L4–L5: 1) Minimally invasive decompression, 2) Facet-sparing, bilateral decompression, and 3) Bilateral decompression with a wide facetectomy. Range of motion following each testing condition was compared to intact specimens. Both MI and traditional decompression procedures create significant increases in ROM in all modes of loading. However, when compared to the MI approach, traditional decompression produces significantly larger increase in ROM in flexion-extension (p<0.005) and axial rotation (p<0.05). It additionally creates increased ROM with lateral bending on the approach side (p<0.05). Lateral bending on the non-approach side is not significantly changed. Lastly, wide medial facet removal (40% to 50%) causes significant hypermobility, especially in axial rotation. While both MI and traditional lumbar decompressions may increase post-operative ROM in all conditions, a MI approach causes significantly smaller increase in ROM. With an MI approach, increased movement with lateral bending is only toward the approach side. Further, non-facet sparing decompression is further destabilizing in all loading modes. PMID:24658010

  17. The Extended Oxygen Window Concept for Programming Saturation Decompressions Using Air and Nitrox.

    PubMed

    Kot, Jacek; Sicko, Zdzislaw; Doboszynski, Tadeusz

    2015-01-01

    Saturation decompression is a physiological process of transition from one steady state, full saturation with inert gas at pressure, to another one: standard conditions at surface. It is defined by the borderline condition for time spent at a particular depth (pressure) and inert gas in the breathing mixture (nitrogen, helium). It is a delicate and long lasting process during which single milliliters of inert gas are eliminated every minute, and any disturbance can lead to the creation of gas bubbles leading to decompression sickness (DCS). Most operational procedures rely on experimentally found parameters describing a continuous slow decompression rate. In Poland, the system for programming of continuous decompression after saturation with compressed air and nitrox has been developed as based on the concept of the Extended Oxygen Window (EOW). EOW mainly depends on the physiology of the metabolic oxygen window--also called inherent unsaturation or partial pressure vacancy--but also on metabolism of carbon dioxide, the existence of water vapor, as well as tissue tension. Initially, ambient pressure can be reduced at a higher rate allowing the elimination of inert gas from faster compartments using the EOW concept, and maximum outflow of nitrogen. Then, keeping a driving force for long decompression not exceeding the EOW allows optimal elimination of nitrogen from the limiting compartment with half-time of 360 min. The model has been theoretically verified through its application for estimation of risk of decompression sickness in published systems of air and nitrox saturation decompressions, where DCS cases were observed. Clear dose-reaction relation exists, and this confirms that any supersaturation over the EOW creates a risk for DCS. Using the concept of the EOW, 76 man-decompressions were conducted after air and nitrox saturations in depth range between 18 and 45 meters with no single case of DCS. In summary, the EOW concept describes physiology of

  18. Near-isothermal conditions in the middle and lower crust induced by melt migration.

    PubMed

    Depine, Gabriela V; Andronicos, Christopher L; Phipps-Morgan, Jason

    2008-03-06

    The thermal structure of the crust strongly influences deformation, metamorphism and plutonism. Models for the geothermal gradient in stable crust predict a steady increase of temperature with depth. This thermal structure, however, is incompatible with observations from high-temperature metamorphic terranes exhumed in orogens. Global compilations of peak conditions in high-temperature metamorphic terranes define relatively narrow ranges of peak temperatures over a wide range in pressure, for both isothermal decompression and isobaric cooling paths. Here we develop simple one-dimensional thermal models that include the effects of melt migration. These models show that long-lived plutonism results in a quasi-steady-state geotherm with a rapid temperature increase in the upper crust and nearly isothermal conditions in the middle and lower crust. The models also predict that the upward advection of heat by melt generates granulite facies metamorphism, and widespread andalusite-sillimanite metamorphism in the upper crust. Once the quasi-steady-state thermal profile is reached, the middle and lower crust are greatly weakened due to high temperatures and anatectic conditions, thus setting the stage for gravitational collapse, exhumation and isothermal decompression after the onset of plutonism. Near-isothermal conditions in the middle and lower crust result from the thermal buffering effect of dehydration melting reactions that, in part, control the shape of the geotherm.

  19. Endoscopic transnasal decompression for management of basilar invagination in osteogenesis imperfecta.

    PubMed

    Hansen, Mitchell A; da Cruz, Melville J; Owler, Brian K

    2008-10-01

    Osteogenesis imperfecta (OI) is a disorder of bone development caused by a genetic dysfunction of collagen synthesis. Basilar invagination (BI) is an uncommon but serious complication of OI. Brainstem decompression in OI is undertaken in certain circumstances. Transoral-transpalatopharyngeal ventral decompression with posterior occipitocervical fusion has become the treatment of choice when required. This technical note outlines a novel endoscopic transnasal approach for ventral decompression. The literature is reviewed and a strategy for the management of BI in patients with OI is outlined.

  20. Surgical variation of microvascular decompression for trigeminal neuralgia: A technical note and anatomical study

    PubMed Central

    da Silva, Otávio T.; de Almeida, César C.; Iglesio, Ricardo F.; de Navarro, Jessie M.; Teixeira, Manoel J.; Duarte, Kleber P.

    2016-01-01

    Background: In this article, the authors described their experience in microvascular decompression for trigeminal neuralgia. Methods: The microvascular decompression technique used in the authors’ institution is described in a step by step manner with some illustrative cases as well as a cadaver dissection to highlight the differences with other previously described techniques. Results: Since 2013, 107 patients were operated in the Neurosurgery Division of the University of São Paulo using the described technique, with a shorter operative time and avoiding cerebellar retractor compared with classic techniques. Conclusion: Our modified microvascular decompression technique for trigeminal neuralgia can be used with safety and efficiency for treating trigeminal neuralgia. PMID:27625893

  1. Neurophysiological assessment of divers with medical histories of neurological decompression illness.

    PubMed Central

    Murrison, A W; Glasspool, E; Pethybridge, R J; Francis, T J; Sedgwick, E M

    1994-01-01

    OBJECTIVE--To examine the possibility that subclinical damage may persist after clinical recovery from neurological decompression illness. METHODS--The neuraxes of 71 divers with medical histories of neurological decompression illness and 37 non-diver controls were examined by recording the somatosensory evoked potentials produced on stimulation of the posterior tibial and median nerves. RESULTS--Although the tests gave some objective support for the presence of "soft" residual neurological symptoms and signs, no evidence was given for the presence of subclinical damage. CONCLUSIONS--The contention that neurological damage persists after full clinical recovery from the neurological decompression illness was not supported. PMID:7849848

  2. Reversible Cerebral Vasoconstriction Syndrome with Intracranial Hypertension: Should Decompressive Craniectomy Be Considered?

    PubMed Central

    Mrozek, Ségolène; Lonjaret, Laurent; Jaffre, Aude; Januel, Anne-Christine; Raposo, Nicolas; Boetto, Sergio; Albucher, Jean-François; Fourcade, Olivier; Geeraerts, Thomas

    2017-01-01

    Background Reversible cerebral vasoconstriction syndrome (RCVS) is a rare cause of intracerebral hemorrhage (ICH) causing intracranial hypertension. Methods Case report. Results We report a case of RCVS-related ICH leading to refractory intracranial hypertension. A decompressive craniectomy was performed to control intracranial pressure. We discuss here the management of RCVS with intracranial hypertension. Decompressive craniectomy was preformed to avoid the risky option of high cerebral perfusion pressure management with the risk of bleeding, hemorrhagic complications, and high doses of norepinephrine. Neurological outcome was good. Conclusion RCVS has a complex pathophysiology and can be very difficult to manage in cases of intracranial hypertension. Decompressive craniectomy should probably be considered. PMID:28203185

  3. Unusual Clinical Presentation and Role of Decompressive Craniectomy in Herpes Simplex Encephalitis.

    PubMed

    Singhi, Pratibha; Saini, Arushi Gahlot; Sahu, Jitendra Kumar; Kumar, Nuthan; Vyas, Sameer; Vasishta, Rakesh Kumar; Aggarwal, Ashish

    2015-08-01

    Decompressive craniectomy in pediatric central nervous infections with refractory intracranial hypertension is less commonly practiced. We describe improved outcome of decompressive craniectomy in a 7-year-old boy with severe herpes simplex encephalitis and medically refractory intracranial hypertension, along with a brief review of the literature. Timely recognition of refractory intracranial hypertension and surgical decompression in children with herpes simplex encephalitis can be life-saving. Additionally, strokelike atypical presentations are being increasingly recognized in children with herpes simplex encephalitis and should not take one away from the underlying herpes simplex encephalitis.

  4. Viscosity Measurement for Tellurium Melt

    NASA Technical Reports Server (NTRS)

    Lin, Bochuan; Li, Chao; Ban, Heng; Scripa, Rosalia N.; Su, Ching-Hua; Lehoczky, Sandor L.

    2006-01-01

    The viscosity of high temperature Te melt was measured using a new technique in which a rotating magnetic field was applied to the melt sealed in a suspended ampoule, and the torque exerted by rotating melt flow on the ampoule wall was measured. Governing equations for the coupled melt flow and ampoule torsional oscillation were solved, and the viscosity was extracted from the experimental data by numerical fitting. The computational result showed good agreement with experimental data. The melt velocity transient initiated by the rotating magnetic field reached a stable condition quickly, allowing the viscosity and electrical conductivity of the melt to be determined in a short period.

  5. Thermoacoustic Streaming and Ultrasonic Processing of Low Melting Melts

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.

    1997-01-01

    Ultrasonic levitation allows the processing of low melting materials both in 1 G as well as in microgravity. The free suspension of the melts also facilitates undercooling, permitting the measurements of the physical properties of the metastable liquids.

  6. Elemental and Sr-Nd-Pb isotope geochemistry of the Cenozoic basalts in Southeast China: Insights into their mantle sources and melting processes

    NASA Astrophysics Data System (ADS)

    Sun, Pu; Niu, Yaoling; Guo, Pengyuan; Ye, Lei; Liu, Jinju; Feng, Yuexing

    2017-02-01

    We analyzed whole-rock major and trace elements and Sr-Nd-Pb isotopes of the Cenozoic basalts in Southeast China to investigate their mantle source characteristics and melting process. These basalts are spatially associated with three extensional fault systems parallel to the coast line. After correction for the effect of olivine microlites on bulk-rock compositions and the effect of crystal fractionation, we obtained primitive melt compositions for these samples. These primitive melts show increasing SiO2, Al2O3 but decreasing FeO, MgO, TiO2, P2O5, CaO and CaO/Al2O3 from the interior to the coast. Such spatial variations of major element abundances and ratios are consistent with a combined effect of fertile source compositional variation and increasing extent and decreasing pressure of decompression melting from beneath the thick lithosphere in the interior to beneath the thin lithosphere in the coast. These basalts are characterized by incompatible element enrichment but varying extent of isotopic depletion. This element-isotope decoupling is most consistent with recent mantle source enrichment by means of low-degree melt metasomatism that elevated incompatible element abundances without yet having adequate time for isotopic ingrowth in the mantle source regions. Furthermore, Sr and Nd isotope ratios show significant correlations with Nb/Th, Nb/La, Sr/Sr* and Eu/Eu*, which substantiates the presence of recycled upper continental crustal material in the mantle sources of these basalts. Pb isotope ratios also exhibit spatial variation, increasing from the interior to the coastal area. The significant correlations of major element abundances with Pb isotope ratios indicate that the Pb isotope variations also result from varied extent and pressure of decompression melting. We conclude that the elevated Pb isotope ratios from the interior to coast are consistent with increasing extent of decompression melting of the incompatible element depleted mantle matrix, which

  7. Sideband excitation of trapped ions by rapid adiabatic passage for manipulation of motional states

    SciTech Connect

    Watanabe, T.; Nomura, S.; Toyoda, K.; Urabe, S.

    2011-09-15

    We describe an analysis and experimental results of the manipulation of motional states of a single trapped {sup 40}Ca{sup +} ion based on sideband excitation by rapid adiabatic passage. When the sideband transition is excited by rapid adiabatic passage, adiabaticity may be affected by ac Stark shifts. We investigate the influence of ac Stark shifts and compensate for these shifts with an additional laser field. This makes the population transfer by rapid adiabatic passage more robust with respect to experimental parameters. Finally, we manipulate the motional states and generate motional Fock states of a single {sup 40}Ca{sup +} ion by rapid adiabatic passage with ac Stark compensation.

  8. New method speeds body inert gas saturation and utilizes surface decompression

    NASA Technical Reports Server (NTRS)

    Edel, P. O.

    1971-01-01

    Method reduces required saturation time from three days to six hours and also reduces required decompression time. Waiting time for planning underwater research is therefore reduced, and emergency surfacing is possible.

  9. Arthroscopic decompression with indigo carmine for treating paralabral cysts in the shoulder.

    PubMed

    Kabuto, Y; Morihara, T; Furukawa, R; Kida, Y; Sukenari, T; Onishi, O; Minami, M; Arai, Y; Fujiwara, H; Kubo, T

    2016-12-01

    Paralabral cysts in the shoulder are a relatively rare pathology. It is sometimes difficult to detect the location of a paralabral cyst in the shoulder using arthroscopy, and it can be difficult to confirm sufficient decompression by arthroscopy. We describe the case of a 64-year-old woman who underwent arthroscopic decompression for a paralabral cyst in the shoulder. Indigo carmine was injected into the cyst under ultrasonography guidance just before the operation. The leakage point of indigo carmine was detected using arthroscopy. Arthroscopic decompression was performed until the indigo carmine was completely discharged. Her shoulder pain, limited range of motion, and muscle weakness during abduction and external rotation improved postoperatively. Magnetic resonance imaging confirmed the disappearance of the cyst. Arthroscopic decompression using an ultrasonography-guided injection of indigo carmine is a useful treatment for a paralabral cyst in the shoulder.

  10. Non-adiabatic dynamics of molecules in optical cavities

    NASA Astrophysics Data System (ADS)

    Kowalewski, Markus; Bennett, Kochise; Mukamel, Shaul

    2016-02-01

    Strong coupling of molecules to the vacuum field of micro cavities can modify the potential energy surfaces thereby opening new photophysical and photochemical reaction pathways. While the influence of laser fields is usually described in terms of classical field, coupling to the vacuum state of a cavity has to be described in terms of dressed photon-matter states (polaritons) which require quantized fields. We present a derivation of the non-adiabatic couplings for single molecules in the strong coupling regime suitable for the calculation of the dressed state dynamics. The formalism allows to use quantities readily accessible from quantum chemistry codes like the adiabatic potential energy surfaces and dipole moments to carry out wave packet simulations in the dressed basis. The implications for photochemistry are demonstrated for a set of model systems representing typical situations found in molecules.

  11. Non-adiabatic dynamics of molecules in optical cavities

    SciTech Connect

    Kowalewski, Markus Bennett, Kochise; Mukamel, Shaul

    2016-02-07

    Strong coupling of molecules to the vacuum field of micro cavities can modify the potential energy surfaces thereby opening new photophysical and photochemical reaction pathways. While the influence of laser fields is usually described in terms of classical field, coupling to the vacuum state of a cavity has to be described in terms of dressed photon-matter states (polaritons) which require quantized fields. We present a derivation of the non-adiabatic couplings for single molecules in the strong coupling regime suitable for the calculation of the dressed state dynamics. The formalism allows to use quantities readily accessible from quantum chemistry codes like the adiabatic potential energy surfaces and dipole moments to carry out wave packet simulations in the dressed basis. The implications for photochemistry are demonstrated for a set of model systems representing typical situations found in molecules.

  12. Adiabatic theory of solitons fed by dispersive waves

    NASA Astrophysics Data System (ADS)

    Pickartz, Sabrina; Bandelow, Uwe; Amiranashvili, Shalva

    2016-09-01

    We consider scattering of low-amplitude dispersive waves at an intense optical soliton which constitutes a nonlinear perturbation of the refractive index. Specifically, we consider a single-mode optical fiber and a group velocity matched pair: an optical soliton and a nearly perfectly reflected dispersive wave, a fiber-optical analog of the event horizon. By combining (i) an adiabatic approach that is used in soliton perturbation theory and (ii) scattering theory from quantum mechanics, we give a quantitative account of the evolution of all soliton parameters. In particular, we quantify the increase in the soliton peak power that may result in the spontaneous appearance of an extremely large, so-called champion soliton. The presented adiabatic theory agrees well with the numerical solutions of the pulse propagation equation. Moreover, we predict the full frequency band of the scattered dispersive waves and explain an emerging caustic structure in the space-time domain.

  13. Engineering adiabaticity at an avoided crossing with optimal control

    NASA Astrophysics Data System (ADS)

    Chasseur, T.; Theis, L. S.; Sanders, Y. R.; Egger, D. J.; Wilhelm, F. K.

    2015-04-01

    We investigate ways to optimize adiabaticity and diabaticity in the Landau-Zener model with nonuniform sweeps. We show how diabaticity can be engineered with a pulse consisting of a linear sweep augmented by an oscillating term. We show that the oscillation leads to jumps in populations whose value can be accurately modeled using a model of multiple, photon-assisted Landau-Zener transitions, which generalizes work by Wubs et al. [New J. Phys. 7, 218 (2005)], 10.1088/1367-2630/7/1/218. We extend the study on diabaticity using methods derived from optimal control. We also show how to preserve adiabaticity with optimal pulses at limited time, finding a nonuniform quantum speed limit.

  14. Adiabatic molecular-dynamics-simulation-method studies of kinetic friction

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Sokoloff, J. B.

    2005-06-01

    An adiabatic molecular-dynamics method is developed and used to study the Muser-Robbins model for dry friction (i.e., nonzero kinetic friction in the slow sliding speed limit). In this model, dry friction between two crystalline surfaces rotated with respect to each other is due to mobile molecules (i.e., dirt particles) adsorbed at the interface. Our adiabatic method allows us to quickly locate interface potential-well minima, which become unstable during sliding of the surfaces. Since dissipation due to friction in the slow sliding speed limit results from mobile molecules dropping out of such unstable wells, our method provides a way to calculate dry friction, which agrees extremely well with results found by conventional molecular dynamics for the same system, but our method is more than a factor of 10 faster.

  15. Steam bottoming cycle for an adiabatic diesel engine

    NASA Technical Reports Server (NTRS)

    Poulin, E.; Demier, R.; Krepchin, I.; Walker, D.

    1984-01-01

    Steam bottoming cycles using adiabatic diesel engine exhaust heat which projected substantial performance and economic benefits for long haul trucks were studied. Steam cycle and system component variables, system cost, size and performance were analyzed. An 811 K/6.90 MPa state of the art reciprocating expander steam system with a monotube boiler and radiator core condenser was selected for preliminary design. The costs of the diesel with bottoming system (TC/B) and a NASA specified turbocompound adiabatic diesel with aftercooling with the same total output were compared, the annual fuel savings less the added maintenance cost was determined to cover the increase initial cost of the TC/B system in a payback period of 2.3 years. Steam bottoming system freeze protection strategies were developed, technological advances required for improved system reliability are considered and the cost and performance of advanced systes are evaluated.

  16. Adiabatic approximation and fluctuations in exciton-polariton condensates

    NASA Astrophysics Data System (ADS)

    Bobrovska, Nataliya; Matuszewski, Michał

    2015-07-01

    We study the relation between the models commonly used to describe the dynamics of nonresonantly pumped exciton-polariton condensates, namely the ones described by the complex Ginzburg-Landau equation, and by the open-dissipative Gross-Pitaevskii equation including a separate equation for the reservoir density. In particular, we focus on the validity of the adiabatic approximation and small density fluctuations approximation that allow one to reduce the coupled condensate-reservoir dynamics to a single partial differential equation. We find that the adiabatic approximation consists of three independent analytical conditions that have to be fulfilled simultaneously. By investigating stochastic versions of the two corresponding models, we verify that the breakdown of these approximations can lead to discrepancies in correlation lengths and distributions of fluctuations. Additionally, we consider the phase diffusion and number fluctuations of a condensate in a box, and show that self-consistent description requires treatment beyond the typical Bogoliubov approximation.

  17. Confinement loss in adiabatic photonic crystal fiber tapers

    NASA Astrophysics Data System (ADS)

    Kuhlmey, Boris T.; Nguyen, Hong C.; Steel, M. J.; Eggleton, Benjamin J.

    2006-09-01

    We numerically study confinement loss in photonic crystal fiber (PCF) tapers and compare our results with previously published experimental data. Agreement between theory and experiment requires taking into account hole shrinkage during the tapering process, which we measure by using a noninvasive technique. We show that losses are fully explained within the adiabatic approximation and that they are closely linked to the existence of a fundamental core-mode cutoff. This cutoff is equivalent to the core-mode cutoff in depressed-cladding fibers, so that losses in PCF tapers can be obtained semiquantitatively from an equivalent depressed-cladding fiber model. Finally, we discuss the definition of adiabaticity in this open boundary problem.

  18. Multidimensional Study of High-Adiabat OMEGA Cryogenic Experiments

    NASA Astrophysics Data System (ADS)

    Collins, T. J. B.; Betti, R.; Bose, A.; Christopherson, A. R.; Knauer, J. P.; Marozas, J. A.; Maximov, A. V.; Mora, A.; Radha, P. B.; Shang, W.; Shvydky, A.; Stoeckl, C.; Woo, K. M.; Varchas, G.

    2016-10-01

    Despite recent advances in modeling laser direct-drive inertial confinement fusion (ICF) experiments, there remains a predictability gap. This is particularly shown by the shortfall in hot-spot pressures inferred from OMEGA cryogenic implosions. To address this, a series of high-adiabat, cryogenic implosions were performed on OMEGA. These shots were performed with and without single-beam smoothing by spectral dispersion, at low and high drive intensities. These shots represent a regime where good agreement with simulation is expected because of the high adiabat. Multidimensional simulations of these shots will be presented with an emphasis on comparison with experimental indicators of departure from spherical symmetry (``1-D-ness''). The roles of short- and long-wavelength perturbations are considered. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  19. Breaking of dynamical adiabaticity in direct laser acceleration of electrons

    NASA Astrophysics Data System (ADS)

    Robinson, A. P. L.; Arefiev, A. V.

    2017-02-01

    The interaction of an electron oscillating in an ion channel and irradiated by a plane electromagnetic wave is considered. It is shown that the interaction qualitatively changes with the increase of electron energy, as the oscillations across the channel become relativistic. The "square-wave-like" profile of the transverse velocity in the relativistic case enables breaking of the adiabaticity that precludes electron energy retention in the non-relativistic case. For an electron with a relativistic factor γ0, the adiabaticity breaks if ωL/ωp0≪√{γ0 } . Under these conditions, the kinetic energy acquired by the electron is retained once the interaction with the laser field ceases. This mechanism notably enables electron heating in regimes that do not require a resonant interaction between the initially oscillating electron and the laser electric field.

  20. Fluctuations of work in nearly adiabatically driven open quantum systems.

    PubMed

    Suomela, S; Salmilehto, J; Savenko, I G; Ala-Nissila, T; Möttönen, M

    2015-02-01

    We extend the quantum jump method to nearly adiabatically driven open quantum systems in a way that allows for an accurate account of the external driving in the system-environment interaction. Using this framework, we construct the corresponding trajectory-dependent work performed on the system and derive the integral fluctuation theorem and the Jarzynski equality for nearly adiabatic driving. We show that such identities hold as long as the stochastic dynamics and work variable are consistently defined. We numerically study the emerging work statistics for a two-level quantum system and find that the conventional diabatic approximation is unable to capture some prominent features arising from driving, such as the continuity of the probability density of work. Our results reveal the necessity of using accurate expressions for the drive-dressed heat exchange in future experiments probing jump time distributions.

  1. Reverse engineering of a nonlossy adiabatic Hamiltonian for non-Hermitian systems

    NASA Astrophysics Data System (ADS)

    Wu, Qi-Cheng; Chen, Ye-Hong; Huang, Bi-Hua; Xia, Yan; Song, Jie

    2016-11-01

    We generalize the quantum adiabatic theorem to the non-Hermitian system and build a strict adiabaticity condition to make the adiabatic evolution nonlossy when taking into account the effect of the adiabatic phase. According to the strict adiabaticity condition, the nonadiabatic couplings and the effect of the imaginary part of adiabatic phase should be eliminated as much as possible. Also, the non-Hermitian Hamiltonian reverse-engineering method is proposed for adiabatically driving an artificial quantum state. A concrete two-level system is adopted to show the usefulness of the reverse-engineering method. We obtain the desired target state by adjusting extra rotating magnetic fields at a predefined time. Furthermore, the numerical simulation shows that certain noise and dissipation in the systems are no longer undesirable but play a positive role in the scheme. Therefore, the scheme is quite useful for quantum information processing in some dissipative systems.

  2. Experimental Adiabatic Quantum Factorization under Ambient Conditions Based on a Solid-State Single Spin System.

    PubMed

    Xu, Kebiao; Xie, Tianyu; Li, Zhaokai; Xu, Xiangkun; Wang, Mengqi; Ye, Xiangyu; Kong, Fei; Geng, Jianpei; Duan, Changkui; Shi, Fazhan; Du, Jiangfeng

    2017-03-31

    The adiabatic quantum computation is a universal and robust method of quantum computing. In this architecture, the problem can be solved by adiabatically evolving the quantum processor from the ground state of a simple initial Hamiltonian to that of a final one, which encodes the solution of the problem. Adiabatic quantum computation has been proved to be a compatible candidate for scalable quantum computation. In this Letter, we report on the experimental realization of an adiabatic quantum algorithm on a single solid spin system under ambient conditions. All elements of adiabatic quantum computation, including initial state preparation, adiabatic evolution (simulated by optimal control), and final state read-out, are realized experimentally. As an example, we found the ground state of the problem Hamiltonian S_{z}I_{z} on our adiabatic quantum processor, which can be mapped to the factorization of 35 into its prime factors 5 and 7.

  3. Arterial gas emboli in altitude-induced decompression sickness

    NASA Technical Reports Server (NTRS)

    Pilmanis, Andrew A.; Olson, Robert M.

    1993-01-01

    Exposure to high altitudes can result in the evolved-gas condition referred to as decompression sickness (DCS). Ultrasonic monitoring techniques have clearly demonstrated the presence of venous gas emboli (VGE) during decompression. Although important to DCS research and our understanding of the physiological mechanisms of this condition, Venus gas emboli have not been considered clinically hazardous, unless in extreme numbers. Arterial gas emboli (AGE), on the other hand, are generally viewed with great concern. Arterial gas emboli can enter the cerebral arterial circulation and arrest blood flow resulting in potentially serious injury. Left ventricular gas emboli were observed with echo imaging in five volunteer subjects during exposure to simulated altitude. These serendipitous findings occurred during altitude exposure under 3 separate research protocols involving 79 subject exposures. The voluntary, fully informed consent of the subjects used in this research was obtained as required by AFR 169-3. A Hewlett-Packard SONOS 1000 Echo Imaging System was used to monitor for precordial gas emboli. The improved resolution of the SONOS 1000 appears to account for these new findings. Four subjects had high incidence DCS and VGE during previous research flights. One subject only had one flight. The altitudes and AGE onset times for the five cases were: (1) 25,500 ft/2:23, (2) 29,000 ft/0:27, (3) 19,500 ft/3:49, (4) 29,500 ft/3:15, and (5) 29,500 ft/1:31. In all five cases, at the time of AGE onset, the VGE scores were high from all monitored locations. Four of the cases were symptomatic at the time of AGE onset (pain and skin mottling). No cerebral manifestations were observed. All subjects were immediately recompressed to ground level and successfully treated with 2 hours of post-breathing or with hyperbaric oxygen therapy. In conclusion, previously undetected AGE were demonstrated--with and without DCS symptoms--during exposure to altitude. It appears that this gas

  4. Exploiting Aerobic Fitness To Reduce Risk Of Hypobaric Decompression Sickness

    NASA Technical Reports Server (NTRS)

    Conkin, Johnny; Gernhardt, Michael L.; Wessel, James H., III

    2007-01-01

    Decompression sickness (DCS) is multivariable. But we hypothesize an aerobically fit person is less likely to experience hypobaric DCS than an unfit person given that fitness is exploited as part of the denitrogenation (prebreathe, PB) process prior to an altitude exposure. Aerobic fitness is peak oxygen uptake (VO2pk, ml/kg/min). METHODS: Treadmill or cycle protocols were used over 15 years to determine VO2pks. We evaluated dichotomous DCS outcome and venous gas emboli (VGE) outcome detected in the pulmonary artery with Doppler ultrasound associated with VO2pk for two classes of experiments: 1) those with no PB or PB under resting conditions prior to ascent in an altitude chamber, and 2) PB that included exercise for some part of the PB. There were 165 exposures (mean VO2pk 40.5 +/- 7.6 SD) with 25 cases of DCS in the first protocol class and 172 exposures (mean VO2pk 41.4 +/- 7.2 SD) with 25 cases of DCS in the second. Similar incidence of the DCS (15.2% vs. 14.5%) and VGE (45.5% vs. 44.8%) between the two classes indicates that decompression stress was similar. The strength of association between outcome and VO2pk was evaluated using univariate logistic regression. RESULTS: An inverse relationship between the DCS outcome and VO2pk was evident, but the relationship was strongest when exercise was done as part of the PB (exercise PB, coef. = -0.058, p = 0.07; rest or no PB, coef. = -0.005, p = 0.86). There was no relationship between VGE outcome and VO2pk (exercise PB, coef. = -0.003, p = 0.89; rest or no PB, coef. = 0.014, p = 0.50). CONCLUSIONS: A significant change in probability of DCS was associated with fitness only when exercise was included in the denitrogenation process. We believe a fit person that exercises during PB efficiently eliminates dissolved nitrogen from tissues.

  5. Exploiting Aerobic Fitness to Reduce Risk of Hypobaric Decompression Sickness

    NASA Technical Reports Server (NTRS)

    Conkin, J.; Gernhardt, M. L.; Wessel, J. H.

    2007-01-01

    Decompression sickness (DCS) is multivariable. But we hypothesize an aerobically fit person is less likely to experience hypobaric DCS than an unfit person given that fitness is exploited as part of the denitrogenation (prebreathe, PB) process prior to an altitude exposure. Aerobic fitness is peak oxygen uptake (VO2pk, ml/kg/min). Treadmill or cycle protocols were used over 15 years to determine VO2pks. We evaluated dichotomous DCS outcome and venous gas emboli (VGE) outcome detected in the pulmonary artery with Doppler ultrasound associated with VO2pk for two classes of experiments: 1) those with no PB or PB under resting conditions prior to ascent in an altitude chamber, and 2) PB that included exercise for some part of the PB. There were 165 exposures (mean VO2pk 40.5 plus or minus 7.6 SD) with 25 cases of DCS in the first protocol class and 172 exposures (mean VO2pk 41.4 plus or minus 7.2 SD) with 25 cases of DCS in the second. Similar incidence of the DCS (15.2% vs. 14.5%) and VGE (45.5% vs. 44.8%) between the two classes indicates that decompression stress was similar. The strength of association between outcome and VO2pk was evaluated using univariate logistic regression. An inverse relationship between the DCS outcome and VO2pk was evident, but the relationship was strongest when exercise was done as part of the PB (exercise PB, coef. = -0.058, p = 0.07; rest or no PB, coef. = -0.005, p = 0.86). There was no relationship between VGE outcome and VO2pk (exercise PB, coef. = -0.003, p = 0.89; rest or no PB, coef. = 0.014, p = 0.50). A significant change in probability of DCS was associated with fitness only when exercise was included in the denitrogenation process. We believe a fit person that exercises during PB efficiently eliminates dissolved nitrogen from tissues.

  6. Microvascular Decompression for Hemifacial Spasm Associated with Vertebrobasilar Artery

    PubMed Central

    Kim, Joo Pyung; Choi, Seok Keun; Rhee, Bong Arm; Lim, Young Jin

    2008-01-01

    Objective Hemifacial spasm (HFS) is considered as a reversible pathophysiological condition mainly induced by continuous vascular compression of the facial nerve root exit zone (REZ) at the cerebellopontine angle. As an offending vessel, vertebrobasilar artery tends to compress much more heavily than others. The authors analyzed HFS caused by vertebrobasilar artery and described the relationships between microsurgical findings and clinical courses. Methods Out of 1,798 cases treated with microvascular decompression (MVD) from Jan. 1980 to Dec. 2004, the causative vessels were either vertebral artery or basilar artery in 87 patients. Seventy-nine patients were enrolled in this study. Preoperatively, computed tomography (CT) or brain magnetic resonance (MR) imaging with 3-dimentional short range MR technique was performed and CT was checked immediately or 2-3 days after anesthetic recovery. The authors retrospectively analyzed the clinical features, the compression patterns of the vessels at the time of surgery and treatment outcomes. Results There were 47 were male and 32 female patients. HFS developed on the left side in 52 cases and on the right side in 27. The mean age of onset was 52.3 years (range 19-60) and the mean duration of symptoms was 10.7 years. Many patients (39 cases; 49.1%) had past history of hypertension. HFS caused only by the vertebral artery was 8 cases although most of the other cases were caused by vertebral artery (VA) in combination with its branching arteries. Most frequently, the VA and the posterior inferior cerebellar artery (PICA) were the simultaneous causative blood vessels comprising 32 cases (40.5%), and in 27 cases (34.2%) the VA and the anterior inferior cerebellar artery (AICA) were the offenders. Facial symptoms disappeared in 61 cases (77.2%) immediately after the operation and 68 cases (86.1%) showed good outcome after 6 months. Surgical outcome just after the operation was poor in whom the perforators arose from the offending

  7. Thermodynamics of Oligonucleotide Duplex Melting

    ERIC Educational Resources Information Center

    Schreiber-Gosche, Sherrie; Edwards, Robert A.

    2009-01-01

    Melting temperatures of oligonucleotides are useful for a number of molecular biology applications, such as the polymerase chain reaction (PCR). Although melting temperatures are often calculated with simplistic empirical equations, application of thermodynamics provides more accurate melting temperatures and an opportunity for students to apply…

  8. Geometric Phase for Adiabatic Evolutions of General Quantum States

    SciTech Connect

    Wu, Biao; Liu, Jie; Niu, Qian; Singh, David J

    2005-01-01

    The concept of a geometric phase (Berry's phase) is generalized to the case of noneigenstates, which is applicable to both linear and nonlinear quantum systems. This is particularly important to nonlinear quantum systems, where, due to the lack of the superposition principle, the adiabatic evolution of a general state cannot be described in terms of eigenstates. For linear quantum systems, our new geometric phase reduces to a statistical average of Berry's phases. Our results are demonstrated with a nonlinear two-level model.

  9. Stellar oscillations - II - The non-adiabatic case

    NASA Astrophysics Data System (ADS)

    Samadi, R.; Belkacem, K.; Sonoi, T.

    2015-02-01

    A leap forward has been performed due to the space-borne missions, MOST, CoRoT and Kepler. They provided a wealth of observational data, and more precisely oscillation spectra, which have been (and are still) exploited to infer the internal structure of stars. While an adiabatic approach is often sufficient to get information on the stellar equilibrium structures it is not sufficient to get a full understanding of the physics of the oscillation. Indeed, it does not permit one to answer some fundamental questions about the oscillations, such as: What are the physical mechanisms responsible for the pulsations inside stars? What determines the amplitudes? To what extent the adiabatic approximation is valid? All these questions can only be addressed by considering the energy exchanges between the oscillations and the surrounding medium. This lecture therefore aims at considering the energetical aspects of stellar pulsations with particular emphasis on the driving and damping mechanisms. To this end, the full non-adiabatic equations are introduced and thoroughly discussed. Two types of pulsation are distinguished, namely the self-excited oscillations that result from an instability and the solar-like oscillations that result from a balance between driving and damping by turbulent convection. For each type, the main physical principles are presented and illustrated using recent observations obtained with the ultra-high precision photometry space-borne missions (MOST, CoRoT and Kepler). Finally, we consider in detail the physics of scaling relations, which relates the seismic global indices with the global stellar parameters and gave birth to the development of statistical (or ensemble) asteroseismology. Indeed, several of these relations rely on the same cause: the physics of non-adiabatic oscillations.

  10. Adiabatic modulation of cnoidal wave by Kuznetsov - Ma soliton

    NASA Astrophysics Data System (ADS)

    Makarov, V. A.; Petnikova, V. M.; Shuvalov, V. V.

    2016-08-01

    The problem of nonlinear interaction of a cnoidal wave (a “fast” component of vector light field) with localized in time and periodic in space control signal in the form of Kuznetsov-Ma soliton (a "slow" component of the same field) is analytically solved in the adiabatic approximation. The conditions which must be fulfilled for stable propagation of the obtained solution with amplitude and frequency modulation are determined.

  11. Adiabatic pipelining: a key to ternary computing with quantum dots.

    PubMed

    Pečar, P; Ramšak, A; Zimic, N; Mraz, M; Lebar Bajec, I

    2008-12-10

    The quantum-dot cellular automaton (QCA), a processing platform based on interacting quantum dots, was introduced by Lent in the mid-1990s. What followed was an exhilarating period with the development of the line, the functionally complete set of logic functions, as well as more complex processing structures, however all in the realm of binary logic. Regardless of these achievements, it has to be acknowledged that the use of binary logic is in computing systems mainly the end result of the technological limitations, which the designers had to cope with in the early days of their design. The first advancement of QCAs to multi-valued (ternary) processing was performed by Lebar Bajec et al, with the argument that processing platforms of the future should not disregard the clear advantages of multi-valued logic. Some of the elementary ternary QCAs, necessary for the construction of more complex processing entities, however, lead to a remarkable increase in size when compared to their binary counterparts. This somewhat negates the advantages gained by entering the ternary computing domain. As it turned out, even the binary QCA had its initial hiccups, which have been solved by the introduction of adiabatic switching and the application of adiabatic pipeline approaches. We present here a study that introduces adiabatic switching into the ternary QCA and employs the adiabatic pipeline approach to successfully solve the issues of elementary ternary QCAs. What is more, the ternary QCAs presented here are sizewise comparable to binary QCAs. This in our view might serve towards their faster adoption.

  12. Competing adiabatic Thouless pumps in enlarged parameter spaces

    NASA Astrophysics Data System (ADS)

    Lopes, Pedro L. e. S.; Ghaemi, Pouyan; Ryu, Shinsei; Hughes, Taylor L.

    2016-12-01

    The transfer of conserved charges through insulating matter via smooth deformations of the Hamiltonian is known as quantum adiabatic, or Thouless, pumping. Central to this phenomenon are Hamiltonians whose insulating gap is controlled by a multidimensional (usually two-dimensional) parameter space in which paths can be defined for adiabatic changes in the Hamiltonian, i.e., without closing the gap. Here, we extend the concept of Thouless pumps of band insulators by considering a larger, three-dimensional parameter space. We show that the connectivity of this parameter space is crucial for defining quantum pumps, demonstrating that, as opposed to the conventional two-dimensional case, pumped quantities depend not only on the initial and final points of Hamiltonian evolution but also on the class of the chosen path and preserved symmetries. As such, we distinguish the scenarios of closed/open paths of Hamiltonian evolution, finding that different closed cycles can lead to the pumping of different quantum numbers, and that different open paths may point to distinct scenarios for surface physics. As explicit examples, we consider models similar to simple models used to describe topological insulators, but with doubled degrees of freedom compared to a minimal topological insulator model. The extra fermionic flavors from doubling allow for extra gapping terms/adiabatic parameters—besides the usual topological mass which preserves the topology-protecting discrete symmetries—generating an enlarged adiabatic parameter space. We consider cases in one and three spatial dimensions, and our results in three dimensions may be realized in the context of crystalline topological insulators, as we briefly discuss.

  13. Adiabatic Compression Sensitivity of Liquid Fuels and Monopropellants

    DTIC Science & Technology

    2007-11-02

    Sensitivity of Liquid Fuels and Monopropellants " 46’b Internat’I Instrumentation Syrup (Bellevue, WA, 30 Apr- 04 May 00) (Statement A) (Deadline: 30 Dec...99) Adiabatic Compression Sensitivity of Liquid Fuels and Monopropellants Ismail M. K. Ismail Tom W. Hawkins Senior Engineer/Scientist Group Leader...hazard sensitivity, propellants, fuels, oxidizers ABSTRACT Liquid rocket fuels and monopropellants can be sensitive to rapid compression. Such liquids

  14. Kinetic vs. thermodynamic control of degassing of H2O-S ± Cl-bearing andesitic melts

    NASA Astrophysics Data System (ADS)

    Fiege, Adrian; Behrens, Harald; Holtz, François; Adams, Franziska

    2014-01-01

    The sulfur (S) distribution between andesitic melts and fluids, both under near-equilibrium conditions and during fast decompression (disequilibrium conditions), has been experimentally investigated. Isothermal decompression experiments were conducted at ∼1030 °C and variable oxygen fugacity (fO2; log(fO2) from ∼QFM+0.8 to ∼QFM+4.2; QFM = quartz-fayalite-magnetite buffer) in internally heated pressure vessels (IHPV) using synthetic, H2O- and S-bearing andesitic melts (∼4-8 wt% H2O, ∼140-2700 ppm S). Selected glasses were doped with chlorine (Cl; 500-1000 ppm) to study the influence of Cl on S partitioning. The starting pressure varied from 300 to 500 MPa, and pressure (p) was released continuously to reach 150, 100, 70, or 30 MPa. The decompression rate (r) ranged from 0.0005 to 0.17 MPa/s and samples were either directly quenched to preserve disequilibrium conditions or annealed for various times (annealing time (tA) = 1-72 h) at final p and 1030 °C to achieve near-equilibrium conditions. The directly quenched experiments revealed a strong increase of the S(fluid)/S(melt) ratio (S(fluid) = wt% S in the fluid; S(melt) = wt% S in the melt) with increasing r, from ∼30 at 0.02 MPa/s to ∼300 at 0.2 MPa/s at oxidizing conditions (log(fO2) > QFM+3), i.e., when sulfate (S6+) was the only S species. After fast decompression (∼0.1 MPa/s) subsequent annealing for ≥ 5 h resulted in a decrease of S(fluid)/S(melt) by a factor of ∼6, indicating that part of the S present in the fluid at tA = 0 h diffuses back into the melt during annealing. This behavior is explained by the positive correlation between p and sulfate solubility in aqueous fluids. In contrast to oxidizing conditions, the S content in the melt remained almost constant with varying r and was independent of tA at low fO2 (QFM+1 to QFM+1.5), when sulfide (S2-) became abundant. Thus, the different behaviors of S2- and S6+ during kinetically-controlled degassing need to be considered when modeling

  15. Alternative technique in atypical spinal decompression: the use of the ultrasonic scalpel in paediatric achondroplasia.

    PubMed

    Woodacre, Timothy; Sewell, Matthew; Clarke, Andrew J; Hutton, Mike

    2016-06-10

    Spinal stenosis can be a very disabling condition. Surgical decompression carries a risk of dural tear and neural injury, which is increased in patients with severe stenosis or an atypical anatomy. We present an unusual case of symptomatic stenosis secondary to achondroplasia presenting in a paediatric patient, and highlight a new surgical technique used to minimise the risk of dural and neural injury during decompression.

  16. Bilateral Ocular Decompression Retinopathy after Ahmed Valve Implantation for Uveitic Glaucoma

    PubMed Central

    Flores-Preciado, Javier; Ancona-Lezama, David Arturo; Valdés-Lara, Carlos Andrés; Díez-Cattini, Gian Franco; Coloma-González, Itziar

    2016-01-01

    Case Report We report the case of a 29-year-old man who underwent Ahmed valve implantation in both eyes as treatment for uveitic glaucoma, subsequently presenting with bilateral ocular decompression retinopathy in the postoperative period. Discussion Ocular decompression retinopathy is a rare complication of filtering surgery in patients with glaucoma; however, the course is benign in most cases, with spontaneous resolution of bleedings and improvement of visual acuity. PMID:27920718

  17. On optimal methods for adiabatic quantum state transformations

    NASA Astrophysics Data System (ADS)

    Somma, Rolando

    2013-03-01

    Many problems in science could be solved by preparing the low-energy quantum state (or any eigenstate) of a Hamiltonian. A common example is the Boolean satisfiability problem, where each clause can be mapped to the energy of an interacting many-body system, and the problem reduces to minimizing the energy. In quantum computing, adiabatic quantum state transformations (ASTs) provide a tool for preparing the quantum state. ASTs are conventionally implemented via slow or adiabatic perturbations to the Hamiltonian, relying on the quantum adiabatic theorem. Nevertheless, more efficient implementations of ASTs exist. In this talk I will review recently developed methods for ASTs that are more efficient and require less assumptions on the Hamiltonians than the conventional implementation. Such methods involve measurements of the states along the evolution path and have a best-case implementation cost of L/G, where L is the length of the (evolved) state path and G is a lower bound to the spectral gap of the Hamiltonians. I will show that this cost is optimal and comment on results of the gap amplification problem, where the goal is to reduce the cost by increasing G. We acknowledge support from NSF through the CCF program and the LDRD programs at Los Alamos National Laboratory and Sandia National Laboratories.

  18. Non-adiabatic molecular dynamics by accelerated semiclassical Monte Carlo

    SciTech Connect

    White, Alexander J.; Gorshkov, Vyacheslav N.; Tretiak, Sergei; Mozyrsky, Dmitry

    2015-07-07

    Non-adiabatic dynamics, where systems non-radiatively transition between electronic states, plays a crucial role in many photo-physical processes, such as fluorescence, phosphorescence, and photoisomerization. Methods for the simulation of non-adiabatic dynamics are typically either numerically impractical, highly complex, or based on approximations which can result in failure for even simple systems. Recently, the Semiclassical Monte Carlo (SCMC) approach was developed in an attempt to combine the accuracy of rigorous semiclassical methods with the efficiency and simplicity of widely used surface hopping methods. However, while SCMC was found to be more efficient than other semiclassical methods, it is not yet as efficient as is needed to be used for large molecular systems. Here, we have developed two new methods: the accelerated-SCMC and the accelerated-SCMC with re-Gaussianization, which reduce the cost of the SCMC algorithm up to two orders of magnitude for certain systems. In many cases shown here, the new procedures are nearly as efficient as the commonly used surface hopping schemes, with little to no loss of accuracy. This implies that these modified SCMC algorithms will be of practical numerical solutions for simulating non-adiabatic dynamics in realistic molecular systems.

  19. Dynamics of Quantum Adiabatic Evolution Algorithm for Number Partitioning

    NASA Technical Reports Server (NTRS)

    Smelyanskiy, Vadius; vonToussaint, Udo V.; Timucin, Dogan A.; Clancy, Daniel (Technical Monitor)

    2002-01-01

    We have developed a general technique to study the dynamics of the quantum adiabatic evolution algorithm applied to random combinatorial optimization problems in the asymptotic limit of large problem size n. We use as an example the NP-complete Number Partitioning problem and map the algorithm dynamics to that of an auxiliary quantum spin glass system with the slowly varying Hamiltonian. We use a Green function method to obtain the adiabatic eigenstates and the minimum exitation gap, gmin = O(n2(sup -n/2)), corresponding to the exponential complexity of the algorithm for Number Partitioning. The key element of the analysis is the conditional energy distribution computed for the set of all spin configurations generated from a given (ancestor) configuration by simultaneous flipping of a fixed number of spins. For the problem in question this distribution is shown to depend on the ancestor spin configuration only via a certain parameter related to the energy of the configuration. As the result, the algorithm dynamics can be described in terms of one-dimensional quantum diffusion in the energy space. This effect provides a general limitation of a quantum adiabatic computation in random optimization problems. Analytical results are in agreement with the numerical simulation of the algorithm.

  20. Dynamics of Quantum Adiabatic Evolution Algorithm for Number Partitioning

    NASA Technical Reports Server (NTRS)

    Smelyanskiy, V. N.; Toussaint, U. V.; Timucin, D. A.

    2002-01-01

    We have developed a general technique to study the dynamics of the quantum adiabatic evolution algorithm applied to random combinatorial optimization problems in the asymptotic limit of large problem size n. We use as an example the NP-complete Number Partitioning problem and map the algorithm dynamics to that of an auxiliary quantum spin glass system with the slowly varying Hamiltonian. We use a Green function method to obtain the adiabatic eigenstates and the minimum excitation gap. g min, = O(n 2(exp -n/2), corresponding to the exponential complexity of the algorithm for Number Partitioning. The key element of the analysis is the conditional energy distribution computed for the set of all spin configurations generated from a given (ancestor) configuration by simultaneous flipping of a fixed number of spins. For the problem in question this distribution is shown to depend on the ancestor spin configuration only via a certain parameter related to 'the energy of the configuration. As the result, the algorithm dynamics can be described in terms of one-dimensional quantum diffusion in the energy space. This effect provides a general limitation of a quantum adiabatic computation in random optimization problems. Analytical results are in agreement with the numerical simulation of the algorithm.

  1. The performance of the quantum adiabatic algorithm on spike Hamiltonians

    NASA Astrophysics Data System (ADS)

    Kong, Linghang; Crosson, Elizabeth

    Spike Hamiltonians arise from optimization instances for which the adiabatic algorithm provably out performs classical simulated annealing. In this work, we study the efficiency of the adiabatic algorithm for solving the “the Hamming weight with a spike” problem by analyzing the scaling of the spectral gap at the critical point for various sizes of the barrier. Our main result is a rigorous lower bound on the minimum spectral gap for the adiabatic evolution when the bit-symmetric cost function has a thin but polynomially high barrier, which is based on a comparison argument and an improved variational ansatz for the ground state. We also adapt the discrete WKB method for the case of abruptly changing potentials and compare it with the predictions of the spin coherent instanton method which was previously used by Farhi, Goldstone and Gutmann. Finally, our improved ansatz for the ground state leads to a method for predicting the location of avoided crossings in the excited energy states of the thin spike Hamiltonian, and we use a recursion relation to understand the ordering of some of these avoided crossings as a step towards analyzing the previously observed diabatic cascade phenomenon.

  2. Adiabatic shear mechanisms for the hard cutting process

    NASA Astrophysics Data System (ADS)

    Yue, Caixu; Wang, Bo; Liu, Xianli; Feng, Huize; Cai, Chunbin

    2015-05-01

    The most important consequence of adiabatic shear phenomenon is formation of sawtooth chip. Lots of scholars focused on the formation mechanism of sawtooth, and the research often depended on experimental approach. For the present, the mechanism of sawtooth chip formation still remains some ambiguous aspects. This study develops a combined numerical and experimental approach to get deeper understanding of sawtooth chip formation mechanism for Polycrystalline Cubic Boron Nitride (PCBN) tools orthogonal cutting hard steel GCr15. By adopting the Johnson-Cook material constitutive equations, the FEM simulation model established in this research effectively overcomes serious element distortions and cell singularity in high strain domain caused by large material deformation, and the adiabatic shear phenomenon is simulated successfully. Both the formation mechanism and process of sawtooth are simulated. Also, the change features regarding the cutting force as well as its effects on temperature are studied. More specifically, the contact of sawtooth formation frequency with cutting force fluctuation frequency is established. The cutting force and effect of cutting temperature on mechanism of adiabatic shear are investigated. Furthermore, the effects of the cutting condition on sawtooth chip formation are researched. The researching results show that cutting feed has the most important effect on sawtooth chip formation compared with cutting depth and speed. This research contributes a better understanding of mechanism, feature of chip formation in hard turning process, and supplies theoretical basis for the optimization of hard cutting process parameters.

  3. Irreconcilable difference between quantum walks and adiabatic quantum computing

    NASA Astrophysics Data System (ADS)

    Wong, Thomas G.; Meyer, David A.

    2016-06-01

    Continuous-time quantum walks and adiabatic quantum evolution are two general techniques for quantum computing, both of which are described by Hamiltonians that govern their evolutions by Schrödinger's equation. In the former, the Hamiltonian is fixed, while in the latter, the Hamiltonian varies with time. As a result, their formulations of Grover's algorithm evolve differently through Hilbert space. We show that this difference is fundamental; they cannot be made to evolve along each other's path without introducing structure more powerful than the standard oracle for unstructured search. For an adiabatic quantum evolution to evolve like the quantum walk search algorithm, it must interpolate between three fixed Hamiltonians, one of which is complex and introduces structure that is stronger than the oracle for unstructured search. Conversely, for a quantum walk to evolve along the path of the adiabatic search algorithm, it must be a chiral quantum walk on a weighted, directed star graph with structure that is also stronger than the oracle for unstructured search. Thus, the two techniques, although similar in being described by Hamiltonians that govern their evolution, compute by fundamentally irreconcilable means.

  4. Non-adiabatic molecular dynamics by accelerated semiclassical Monte Carlo

    DOE PAGES

    White, Alexander J.; Gorshkov, Vyacheslav N.; Tretiak, Sergei; ...

    2015-07-07

    Non-adiabatic dynamics, where systems non-radiatively transition between electronic states, plays a crucial role in many photo-physical processes, such as fluorescence, phosphorescence, and photoisomerization. Methods for the simulation of non-adiabatic dynamics are typically either numerically impractical, highly complex, or based on approximations which can result in failure for even simple systems. Recently, the Semiclassical Monte Carlo (SCMC) approach was developed in an attempt to combine the accuracy of rigorous semiclassical methods with the efficiency and simplicity of widely used surface hopping methods. However, while SCMC was found to be more efficient than other semiclassical methods, it is not yet as efficientmore » as is needed to be used for large molecular systems. Here, we have developed two new methods: the accelerated-SCMC and the accelerated-SCMC with re-Gaussianization, which reduce the cost of the SCMC algorithm up to two orders of magnitude for certain systems. In many cases shown here, the new procedures are nearly as efficient as the commonly used surface hopping schemes, with little to no loss of accuracy. This implies that these modified SCMC algorithms will be of practical numerical solutions for simulating non-adiabatic dynamics in realistic molecular systems.« less

  5. Adiabatic dynamics with classical noise in optical lattice

    NASA Astrophysics Data System (ADS)

    Xu, Guanglei; Daley, Andrew

    2016-05-01

    The technique of adiabatic state preparation is an interesting potential tool for the realisation of sensitive many-body states with ultra-cold atoms at low temperatures. However, questions remain regarding the influence of classical noise in these adiabatic dynamics. We investigate such dynamics in a situation where a level dressing scheme can make amplitude noise in an optical lattice proportional to the Hamiltonian, leading to a quantum Zeno effect for non-adiabatic transitions. We compute the dynamics using stochastic many-body Schrödinger equation and master equation approaches. Taking the examples of 1D Bose-Hubbard model from Mott insulator phase to superfluid phase and comparing with analytical calculations for a two-level system, we demonstrate that when the total time for the process is limited, properly transformed noise can lead to an increased final fidelity in the state preparation. We consider the dynamics also in the presence of imperfections, studying the resulting heating and dephasing for the many-body states, and identifying optimal regimes for future experiments.

  6. Adiabatic invariants for the regular region of the Dicke model

    NASA Astrophysics Data System (ADS)

    Bastarrachea-Magnani, M. A.; Relaño, A.; Lerma-Hernández, S.; López-del-Carpio, B.; Chávez-Carlos, J.; Hirsch, J. G.

    2017-04-01

    Adiabatic invariants for the non-integrable Dicke model are introduced. They are shown to provide approximate second integrals of motion in the energy region where the system exhibits a regular dynamics. This low-energy region, present for any set of values of the Hamiltonian parameters is described both with a semiclassical and a full quantum analysis in a broad region of the parameter space. Peres lattices in this region exhibit that many observables vary smoothly with energy, along distinct lines which beg for a formal description. It is demonstrated how the adiabatic invariants provide a rationale to their presence in many cases. They are built employing the Born–Oppenheimer approximation, valid when a fast system is coupled to a much slower one. As the Dicke model has one bosonic and one fermionic degree of freedom, two versions of the approximation are used, depending on which one is the faster. In both cases a noticeably accord with exact numerical results is obtained. The employment of the adiabatic invariants provides a simple and clear theoretical framework to study the physical phenomenology associated to these regimes, far beyond the energies where a quadratic approximation around the minimal energy configuration can be used.

  7. Experimental implementation of an adiabatic quantum optimization algorithm

    NASA Astrophysics Data System (ADS)

    Steffen, Matthias; van Dam, Wim; Hogg, Tad; Breyta, Greg; Chuang, Isaac

    2003-03-01

    A novel quantum algorithm using adiabatic evolution was recently presented by Ed Farhi [1] and Tad Hogg [2]. This algorithm represents a remarkable discovery because it offers new insights into the usefulness of quantum resources. An experimental demonstration of an adiabatic algorithm has remained beyond reach because it requires an experimentally accessible Hamiltonian which encodes the problem and which must also be smoothly varied over time. We present tools to overcome these difficulties by discretizing the algorithm and extending average Hamiltonian techniques [3]. We used these techniques in the first experimental demonstration of an adiabatic optimization algorithm: solving an instance of the MAXCUT problem using three qubits and nuclear magnetic resonance techniques. We show that there exists an optimal run-time of the algorithm which can be predicted using a previously developed decoherence model. [1] E. Farhi et al., quant-ph/0001106 (2000) [2] T. Hogg, PRA, 61, 052311 (2000) [3] W. Rhim, A. Pines, J. Waugh, PRL, 24,218 (1970)

  8. Analysis of a High-Adiabat Cryogenic Implosion on OMEGA

    NASA Astrophysics Data System (ADS)

    Christopherson, A. R.; Betti, R.; Nora, R.; Epstein, R.; Marshall, F. J.; Forrest, C. J.; Stoeckl, C.; Delettrez, J. A.; Radha, P. B.; Howard, J.

    2014-10-01

    The performance of high-adiabat implosions >~ 10 is marginally affected by nonuniformities because of the strong ablative stabilization. To test the validity of the one-dimensional (1-D) physics included in existing hydrocodes, a study of high-adiabat cryogenic DT implosions is carried out by comparing the results of 1-D simulations with several measured quantities. It is found that after including nonlocal transport, cross-beam energy transfer, and hot electrons, 1-D simulations reproduce most of the observables with reasonable accuracy. Since the analysis is applied to the only high-adiabat DT implosion fielded on OMEGA, these results do not fully validate the 1-D physics of current hydrocodes. However, this work shows the framework for establishing a validation capability of the 1-D physics of inertial confinement fusion implosions. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and the Office of Fusion Energy Sciences Number DE-FG02-04ER54786.

  9. Contrasting MORB-Boninite melt reaction trends in IBM forearc moho transition zone

    NASA Astrophysics Data System (ADS)

    Loocke, M. P.; Snow, J. E.; Ishizuka, O.

    2013-12-01

    Models of arc crust formation prior to subduction initiation are hampered by a paucity of observations from present-day arc lower crust. Here we report petrographic analysis and mineral chemistry of spinel from 35 lower crustal peridotites and gabbros recovered from the inner trench slope of the Bonin Ridge (BR). Two groups of these gabbroic samples appear to have reacted with distinct melt compositions. Group M consists of peridotite (a single cpx-harzburgite), wehrlites, and gabbroic rocks with medium Cr# (100 x Cr / Cr + Al) spinels ranging from 45 to 60 and high TiO2 and Al2O3 spanning ~0.1-2.25 and ~12-30 wt. % respectively. Group B consists of only dunites and cpx-free peridotites with high Cr# spinels ranging from 65 to 94 and low TiO2 and Al2O3 spanning ~0-0.12 and ~3-21 wt. % respectively. The group M and group B samples appear to be the result of melt-rock reaction with a MORB-like melt and a more depleted boninitic melt respectively. MORB-like forearc basalts (FAB) (~50-52 Ma) and younger boninites (~44-48 Ma) recovered from the BR have been interpreted to represent a change from decompression melting at subduction initiation to flux melting and boninitic volcanism after establishment of the arc. The gabbroic samples of group M and group B similarly represent a lower crustal record of the change from MORB-like melts created by decompression melting at or soon after subduction initiation to arc-type flux melting and boninite volcanism thereafter. The presence of lower crustal peridotites and gabbroic rocks with spinels belonging to group M and not group B suggests that the lower crust of the BR may be dominated by gabbroic rocks and material genetically related to the FABs. This would imply that a large portion of the lower crust in the fore-arc was formed during or shortly after subduction initiation and is similar in composition to MOR lower crust.

  10. Outcomes and safety of endoscopic tarsal tunnel decompression: a systematic review.

    PubMed

    Gkotsoulias, Efthymios N; Simonson, Devin C; Roukis, Thomas S

    2014-02-01

    Open surgical decompression of the tarsal tunnel is the standard surgical approach for compression of the tibial nerve within the tarsal tunnel. Complications associated with this approach can be significant and periods of non-weight bearing are required. An alternative approach allowing for minimal soft tissue trauma and reduced time to ambulation is therefore desirable. Endoscopic tarsal tunnel decompression may provide such an alternative. The authors performed a systematic review of electronic databases and other relevant sources to identify material regarding the safety of endoscopic tarsal tunnel decompression. Only articles that included clear information concerning the safety of endoscopic tarsal tunnel decompression with a follow-up of at least 12 months were included. Three studies were identified involving 37 feet, with a weighted mean follow-up of 27 months. There were no permanent complications relating to iatrogenic nerve injury, deep infection, or prolonged wound healing problems documented despite initiating ambulation within one week of surgery. Two patients (5.6%) developed recurrence more than 2 years postoperative and one (2.7%) showed no improvement. Endoscopic tarsal tunnel decompression is a safe procedure with a low rate of recurrence or failure and allows for near-immediate ambulation. However, additional prospective investigations comparing open and endoscopic approaches to tarsal tunnel decompression are warranted.

  11. Empirical models for use in designing decompression procedures for space operations

    NASA Technical Reports Server (NTRS)

    Conkin, Johnny; Edwards, Benjamin F.; Waligora, James M.; Horrigan, David J., Jr.

    1987-01-01

    Empirical models for predicting the incidence of Type 1 altitude decompression sickness (DCS) and venous gas emboli (VGE) during space extravehicular activity (EVA), and for use in designing safe denitrogenation decompression procedures are developed. The models are parameterized using DCS and VGE incidence data from NASA and USAF manned altitude chamber decompression tests using 607 male and female subject tests. These models, and procedures for their use, consist of: (1) an exponential relaxation model and procedure for computing tissue nitrogen partial pressure resulting from a specified prebreathing and stepped decompression sequence; (2) a formula for calculating Tissue Ratio (TR), a tissue decompression stress index; (3) linear and Hill equation models for predicting the total incidence of VGE and DCS attendant with a particular TR; (4) graphs of cumulative DCS and VGE incidence (risk) versus EVA exposure time at any specified TR; and (5) two equations for calculating the average delay period for the initial detection of VGE or indication of Type 1 DCS in a group after a specific denitrogenation decompression procedure. Several examples of realistic EVA preparations are provided.

  12. Potential Fifty Percent Reduction in Saturation Diving Decompression Time Using a Combination of Intermittent Recompression and Exercise

    NASA Technical Reports Server (NTRS)

    Gernhardt, Michael I.; Abercromby, Andrew; Conklin, Johnny

    2007-01-01

    Conventional saturation decompression protocols use linear decompression rates that become progressively slower at shallower depths, consistent with free gas phase control vs. dissolved gas elimination kinetics. If decompression is limited by control of free gas phase, linear decompression is an inefficient strategy. The NASA prebreathe reduction program demonstrated that exercise during O2 prebreathe resulted in a 50% reduction (2 h vs. 4 h) in the saturation decompression time from 14.7 to 4.3 psi and a significant reduction in decompression sickness (DCS: 0 vs. 23.7%). Combining exercise with intermittent recompression, which controls gas phase growth and eliminates supersaturation before exercising, may enable more efficient saturation decompression schedules. A tissue bubble dynamics model (TBDM) was used in conjunction with a NASA exercise prebreathe model (NEPM) that relates tissue inert gas exchange rate constants to exercise (ml O2/kg-min), to develop a schedule for decompression from helium saturation at 400 fsw. The models provide significant prediction (p < 0.001) and goodness of fit with 430 cases of DCS in 6437 laboratory dives for TBDM (p = 0.77) and with 22 cases of DCS in 159 altitude exposures for NEPM (p = 0.70). The models have also been used operationally in over 25,000 dives (TBDM) and 40 spacewalks (NEPM). The standard U.S. Navy (USN) linear saturation decompression schedule from saturation at 400 fsw required 114.5 h with a maximum Bubble Growth Index (BGI(sub max)) of 17.5. Decompression using intermittent recompression combined with two 10 min exercise periods (75% VO2 (sub peak)) per day required 54.25 h (BGI(sub max): 14.7). Combined intermittent recompression and exercise resulted in a theoretical 53% (2.5 day) reduction in decompression time and theoretically lower DCS risk compared to the standard USN decompression schedule. These results warrant future decompression trials to evaluate the efficacy of this approach.

  13. The relationship between the adiabatic bulk modulus and enthalpy for mantle-related minerals

    NASA Astrophysics Data System (ADS)

    Anderson, Orson L.

    1989-07-01

    It is found that the adiabatic bulk modulus, KS, is linear with enthalpy over a wide temperature range: up to at least 1825 K, the present limit of the measurement of the bulk modulus. This correlation is shown to hold for Al2O3, MgO, and Mg2SiO4. Since the enthalpy is listed in thermodynamic tables up to 3000 K, one can reasonably safely extrapolate KS up to lower mantle temperatures using this correlation. This correlation was anticipated in a theoretical 1966 paper, where the definition of the anharmonic parameter δ S was made in terms of properties which vary with temperature, δ _s = - left( {1/{α K_S }} right)left( {{δ K}/{δ T}} right)_{P'} where α is the volume coefficient of thermal expansion. The correlation was first confirmed for polycrystalline oxides in an experimental 1966 paper. Since the isotropic shear modulus, G, is linear with T, it is possible to estimate the sound velocities in the temperature regime just below the melting point.

  14. Developing a 3-shock, low-adiabat drive for high pressure material science experiments on NIF

    NASA Astrophysics Data System (ADS)

    Wehrenberg, Christopher; Prisbrey, Shon; Graham, Peter; Park, Hye-Sook; Huntington, Channing; Maddox, Brian; Benedetti, Robin; Rudd, Robert; Arsenlis, Tom; Remington, Bruce

    2014-10-01

    We describe a series of experiments for basic materials science on NIF to develop a planar, 3-shock, low-adiabat drive to reach peak pressures of 5 Mbar, while keeping the physics samples well below their melt temperatures. The primary diagnostic is VISAR, which measures the compression waves as they travel through a Ta witness plate. X-ray ablation from an indirect drive launches a strong (>10 Mbar) shock through a precision fabricated ``reservoir,'' consisting of a CH ablator, followed by layers of Al, CH(18.75%I), 350 mg/cc CRF foam, and a final layer of 10-30 mg/cc foam. This reservoir releases as plasma across a 1.5 mm vacuum gap, then stagnates on the 15 micron thick Ta witness plate, which is backed by a LiF or quartz window. The lowest density reservoir layer sets the strength of the leading shock, which needs to be controlled to keep the physics samples solid, and to control the dislocation density created by this leading shock. We will describe an extensive series of experiments done on NIF to develop this drive. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.

  15. Adiabatic decohesion in a thermoplastic craze thickening at constant or increasing rate

    NASA Astrophysics Data System (ADS)

    Leevers, Patrick S.; Godart, Marie-Aude

    When a crack in a thermally non-diffusive material is impact loaded—or propagates at high speed—a cohesive process which resists slow crack extension may itself cause decohesion by adiabatic heating. By assuming that decohesion ultimately occurs by low-energy disentanglement within a melt layer of critical thickness, the fracture resistance of craze-forming crystalline polymers can be estimated quantitatively. Previous estimates used a simple, thermomechanically linear representation of craze fibril drawing. This paper presents a more physically realistic, numerical formulation, and demonstrates it for constant craze thickening rate (as imposed by an ideal full-notch tension test) and for linearly increasing thickening rate (as at the tip of an impact-loaded or rapidly propagating crack). For a linear material, the numerical formulation gives results which asymptotically approach those from analytical solutions, as craze density approaches zero. In more realistic model polymers, the enthalpy of fusion increasingly delays decohesion as impact speed increases, although the temperature distribution of an endotherm appears to have little effect. Increasing molecular weight, heuristically associated with decreasing craze density and increasing structural dimension, increases the predicted impact fracture resistance. In every case, fracture resistance passes through a minimum as impact speed increases. The conclusions encourage the use of impact fracture tests, and discourage the use of the full-notch tension test, to assess the dynamic fracture resistance of a craze-forming polymer.

  16. Adiabatic magnetocaloric effect in Ni50Mn35In15 ribbons

    NASA Astrophysics Data System (ADS)

    Álvarez-Alonso, P.; Aguilar-Ortiz, C. O.; Camarillo, J. P.; Salazar, D.; Flores-Zúñiga, H.; Chernenko, V. A.

    2016-11-01

    Heusler-type Ni-Mn-based metamagnetic shape memory alloys (MetaMSMAs) are promising candidates for magnetic refrigeration. To increase heat exchange rate and efficiency of cooling, the material should have a high surface/volume ratio. In this work, the typical Ni50Mn35In15 MetaMSMA was selected to fabricate thin ribbons by melt-spinning. The characteristic transformations of the ribbons were determined by calorimetry, X-ray diffraction, scanning electron microscopy and thermomagnetization measurements. The inverse and conventional magnetocaloric effects (MCEs) associated with the martensitic transformation (MT) and the ferromagnetic transition of the austenite (TCA), respectively, were measured directly by the adiabatic method (ΔTad) and indirectly by estimating the magnetic entropy change from magnetization measurements. It is found that the ribbons exhibit large values of ΔTad = -1.1 K at μ0ΔH = 1.9 T, in the vicinity of the MT temperature of 300 K for inverse MCE, and ΔTad = 2.3 K for conventional MCE at TCA = 309 K. This result strongly motivates further development of different MetaMSMA refrigerants shaped as ribbons.

  17. NanoSIMS results from olivine-hosted melt embayments: Magma ascent rate during explosive basaltic eruptions

    NASA Astrophysics Data System (ADS)

    Lloyd, Alexander S.; Ruprecht, Philipp; Hauri, Erik H.; Rose, William; Gonnermann, Helge M.; Plank, Terry

    2014-08-01

    The explosivity of volcanic eruptions is governed in part by the rate at which magma ascends and degasses. Because the time scales of eruptive processes can be exceptionally fast relative to standard geochronometers, magma ascent rate remains difficult to quantify. Here we use as a chronometer concentration gradients of volatile species along open melt embayments within olivine crystals. Continuous degassing of the external melt during magma ascent results in diffusion of volatile species from embayment interiors to the bubble located at their outlets. The novel aspect of this study is the measurement of concentration gradients in five volatile elements (CO2, H2O, S, Cl, F) at fine-scale (5-10 μm) using the NanoSIMS. The wide range in diffusivity and solubility of these different volatiles provides multiple constraints on ascent timescales over a range of depths. We focus on four 100-200 μm, olivine-hosted embayments erupted on October 17, 1974 during the sub-Plinian eruption of Volcán de Fuego. H2O, CO2, and S all decrease toward the embayment outlet bubble, while F and Cl increase or remain roughly constant. Compared to an extensive melt inclusion suite from the same day of the eruption, the embayments have lost both H2O and CO2 throughout the entire length of the embayment. We fit the profiles with a 1-D numerical diffusion model that allows varying diffusivities and external melt concentrations as a function of pressure. Assuming a constant decompression rate from the magma storage region at approximately 220 MPa to the surface, H2O, CO2 and S profiles for all embayments can be fit with a relatively narrow range in decompression rates of 0.3-0.5 MPa/s, equivalent to 11-17 m/s ascent velocity and an 8 to 12 minute duration of magma ascent from ~ 10 km depth. A two stage decompression model takes advantage of the different depth ranges over which CO2 and H2O degas, and produces good fits given an initial stage of slow decompression (0.05-0.3 MPa/s) at high

  18. Habitat Options to Protect Against Decompression Sickness on Mars

    NASA Astrophysics Data System (ADS)

    Conkin, J.

    2000-07-01

    Men and women are alive today, although perhaps still in diapers, who will explore the surface of Mars. Two achievable goals to enable this exploration are to use Martian resources, and to provide a safe means for unrestricted access to the surface. A cost-effective approach for Mars exploration is to use the available resources, such as water and atmospheric gases. Nitrogen (N2) and Argon (Ar) in a concentration ratio of 1.68/1.0 are available, and could form the inert gas component of a habitat atmosphere at 8.0, 9.0, or 10.0 pounds per square inch absolute (psia). The habitat and space suit must be designed as an integrated, complementary, system: a comfortable living environment about 85% of the time and a safe working environment about 15% of the time. A goal is to provide a system that permits unrestricted exploration of Mars. However the risk of decompression sickness (DCS) during the extravehicular activity (EVA) in a 3.75 psia suit after exposure to either of the three habitat conditions may limit unrestricted exploration.

  19. Microvascular decompression for elderly patients with trigeminal neuralgia.

    PubMed

    Phan, Kevin; Rao, Prashanth J; Dexter, Mark

    2016-07-01

    Microvascular decompression (MVD) has been demonstrated to be an excellent surgical treatment approach in younger patients with trigeminal neuralgia (TN). However, it is not clear whether there are additional morbidity and mortality risks for MVD in the elderly population. We performed a systematic literature review using six electronic databases for studies that compared outcomes for MVD for TN in elderly (cut-off ⩾60, 65, 70years) versus younger populations. Outcomes examined included success rate, deaths, strokes, thromboembolism, meningitis, cranial nerve deficits and cerebrospinal fluid leaks. There were 1524 patients in the elderly cohort and 3488 patients in the younger cohort. There was no significant difference in success rates in elderly versus younger patients (87.5% versus 84.8%; P=0.47). However, recurrence rates were lower in the elderly (11.9% versus 15.6%; P=0.03). The number of deaths in the elderly cohort was higher (0.9% versus 0.1%; P=0.003). Rates of stroke (2.5% versus 1%) and thromboembolism (1.1% versus 0%) were also higher for elderly TN patients. No differences were found for rates of meningitis, cranial nerve deficits or cerebrospinal fluid leak. MVD remains an effective and reasonable strategy in the elderly population. There is evidence to suggest that rates of complications such as death, stroke, and thromboembolism may be significantly higher in the elderly population. The presented results may be useful in the decision-making process for MVD in elderly patients with TN.

  20. Improved image decompression for reduced transform coding artifacts

    NASA Technical Reports Server (NTRS)

    Orourke, Thomas P.; Stevenson, Robert L.

    1994-01-01

    The perceived quality of images reconstructed from low bit rate compression is severely degraded by the appearance of transform coding artifacts. This paper proposes a method for producing higher quality reconstructed images based on a stochastic model for the image data. Quantization (scalar or vector) partitions the transform coefficient space and maps all points in a partition cell to a representative reconstruction point, usually taken as the centroid of the cell. The proposed image estimation technique selects the reconstruction point within the quantization partition cell which results in a reconstructed image which best fits a non-Gaussian Markov random field (MRF) image model. This approach results in a convex constrained optimization problem which can be solved iteratively. At each iteration, the gradient projection method is used to update the estimate based on the image model. In the transform domain, the resulting coefficient reconstruction points are projected to the particular quantization partition cells defined by the compressed image. Experimental results will be shown for images compressed using scalar quantization of block DCT and using vector quantization of subband wavelet transform. The proposed image decompression provides a reconstructed image with reduced visibility of transform coding artifacts and superior perceived quality.

  1. Transmaxillary anterior decompressions in patients with severe basilar impression.

    PubMed

    Bhangoo, R S; Crockard, H A

    1999-02-01

    Severe basilar impression leads to an upward translocation of the upper cervical spine and clivus into the foramen magnum and is a diagnosis best made with computed tomography or magnetic resonance imaging scans. Basilar impression may be a primary condition or secondary to bone softening disorders. Symptoms relating to direct neuraxial compression, obstruction to cerebral spinal fluid outflow, and vascular compromise all have been described. Management depends on the exact nature of the abnormality seen, but it is now firmly accepted that those with anterior neuraxial compression should have an anterior decompression. The severe basilar impression and craniofacial abnormalities seen in osteogenesis imperfecta together with the progressive nature of the condition have led to the development of a specific surgical response, the open door maxillotomy combined with a contoured loop fixation of the cervical spine. Little is known of the long term outcome of severe basilar impression, and long term studies undertaken by centers familiar with the condition and its management are required if definitive care is to be delivered to these patients.

  2. Testing of hypotheses about altitude decompression sickness by statistical analyses

    NASA Technical Reports Server (NTRS)

    Van Liew, H. D.; Burkard, M. E.; Conkin, J.; Powell, M. R. (Principal Investigator)

    1996-01-01

    This communication extends a statistical analysis of forced-descent decompression sickness at altitude in exercising subjects (J Appl Physiol 1994; 76:2726-2734) with a data subset having an additional explanatory variable, rate of ascent. The original explanatory variables for risk-function analysis were environmental pressure of the altitude, duration of exposure, and duration of pure-O2 breathing before exposure; the best fit was consistent with the idea that instantaneous risk increases linearly as altitude exposure continues. Use of the new explanatory variable improved the fit of the smaller data subset, as indicated by log likelihood. Also, with ascent rate accounted for, replacement of the term for linear accrual of instantaneous risk by a term for rise and then decay made a highly significant improvement upon the original model (log likelihood increased by 37 log units). The authors conclude that a more representative data set and removal of the variability attributable to ascent rate allowed the rise-and-decay mechanism, which is expected from theory and observations, to become manifest.

  3. Development and interactions of two inert gas bubbles during decompression.

    PubMed

    Jiang, Y; Homer, L D; Thalmann, E D

    1996-09-01

    A mathematical model has been developed to simulate the evolution of two inert gas bubbles in tissue. This is useful for understanding the dynamics of bubbles that presumably arise during decompression. It is assumed that they are spherical and that the tissue volume surrounding them is infinite. The total pressure in each bubble is determined by the barometric and metabolic gas pressures as well as the pressure due to surface tension. Bipolar coordinates are employed to determine the inert gas pressure distribution. Two coupled governing equations for bubble radii are then derived and solved numerically. The results demonstrate how bubble evolution is affected by the distance between bubbles and the initial bubble radii. The existence time and bubble surface flux of two equal-sized bubbles are calculated and compared with those of a single gas bubble model. The results indicate that when two bubbles are very close, it takes 20% more time for two bubbles to dissolve than for a single one, and the total surface flux of two bubbles is nearly 20% less than twice of a single bubble. When the center-to-center distance is 10 times of bubble radius, the effect of bubble interaction on bubble existence time and surface flux are about 6 and 9% changes, respectively. We conclude that if bubbles are not too small, the interactions among bubbles should be included in inert gas bubble models predicting bubble evolution.

  4. Window decompression in laser-heated MagLIF targets

    NASA Astrophysics Data System (ADS)

    Woodbury, Daniel; Peterson, Kyle; Sefkow, Adam

    2015-11-01

    The Magnetized Liner Inertial Fusion (MagLIF) concept requires pre-magnetized fuel to be pre-heated with a laser before undergoing compression by a thick solid liner. Recent experiments and simulations suggest that yield has been limited to date by poor laser preheat and laser-induced mix in the fuel region. In order to assess laser energy transmission through the pressure-holding window, as well as resultant mix, we modeled window disassembly under different conditions using 1D and 2D simulations in both Helios and HYDRA. We present results tracking energy absorption, time needed for decompression, risk of laser-plasma interaction (LPI) that may scatter laser light, and potential for mix from various window thicknesses, laser spot sizes and gas fill densities. These results indicate that using thinner windows (0.5-1 μm windows) and relatively large laser spot radii (600 μm and above) can avoid deleterious effects and improve coupling with the fuel. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the National Nuclear Security Administration under DE-AC04- 94AL85000.

  5. Decompressive craniectomy following traumatic brain injury: developing the evidence base

    PubMed Central

    Kolias, Angelos G.; Adams, Hadie; Timofeev, Ivan; Czosnyka, Marek; Corteen, Elizabeth A.; Pickard, John D.; Turner, Carole; Gregson, Barbara A.; Kirkpatrick, Peter J.; Murray, Gordon D.; Menon, David K.; Hutchinson, Peter J.

    2016-01-01

    Abstract In the context of traumatic brain injury (TBI), decompressive craniectomy (DC) is used as part of tiered therapeutic protocols for patients with intracranial hypertension (secondary or protocol-driven DC). In addition, the bone flap can be left out when evacuating a mass lesion, usually an acute subdural haematoma (ASDH), in the acute phase (primary DC). Even though, the principle of “opening the skull” in order to control brain oedema and raised intracranial pressure has been practised since the beginning of the 20th century, the last 20 years have been marked by efforts to develop the evidence base with the conduct of randomised trials. This article discusses the merits and challenges of this approach and provides an overview of randomised trials of DC following TBI. An update on the RESCUEicp study, a randomised trial of DC versus advanced medical management (including barbiturates) for severe and refractory post-traumatic intracranial hypertension is provided. In addition, the rationale for the RESCUE-ASDH study, the first randomised trial of primary DC versus craniotomy for adult head-injured patients with an ASDH, is presented. PMID:26972805

  6. Decompressive craniectomy following traumatic brain injury: developing the evidence base.

    PubMed

    Kolias, Angelos G; Adams, Hadie; Timofeev, Ivan; Czosnyka, Marek; Corteen, Elizabeth A; Pickard, John D; Turner, Carole; Gregson, Barbara A; Kirkpatrick, Peter J; Murray, Gordon D; Menon, David K; Hutchinson, Peter J

    2016-01-01

    In the context of traumatic brain injury (TBI), decompressive craniectomy (DC) is used as part of tiered therapeutic protocols for patients with intracranial hypertension (secondary or protocol-driven DC). In addition, the bone flap can be left out when evacuating a mass lesion, usually an acute subdural haematoma (ASDH), in the acute phase (primary DC). Even though, the principle of "opening the skull" in order to control brain oedema and raised intracranial pressure has been practised since the beginning of the 20th century, the last 20 years have been marked by efforts to develop the evidence base with the conduct of randomised trials. This article discusses the merits and challenges of this approach and provides an overview of randomised trials of DC following TBI. An update on the RESCUEicp study, a randomised trial of DC versus advanced medical management (including barbiturates) for severe and refractory post-traumatic intracranial hypertension is provided. In addition, the rationale for the RESCUE-ASDH study, the first randomised trial of primary DC versus craniotomy for adult head-injured patients with an ASDH, is presented.

  7. Melt Structure and Properties: Progress and Prognoses

    NASA Astrophysics Data System (ADS)

    Stebbins, J. F.

    2004-12-01

    Recent advances in quantitative determinations of silicate glass structure are beginning to place important constraints on models of the physical and chemical properties of melts, but much remains to be done before such models can become entirely based on structure. For example, models of free energy and major component activities generally assume (lacking better constraints) that network species (e.g. Al, Si, "Qn" groups) and network modifiers (e.g. Na, Ca, K, Mg) each mix randomly. However, recent spectroscopic studies demonstrate strong ordering in the network (significant if incomplete Al avoidance; preference of Al for "Q4" groups, etc.) and between modifier cations differing greatly in field strength (e.g. K+, Mg2+). Solution models thus may need substantial revision, unless new studies of temperature effects on such ordering indicate approach to randomness at magmatic temperatures. Such studies are ongoing, facilitated by recent developments in hyper-quenching technology. On the other hand, discovery of such low-T ordering provides a likely (and long-suspected) mechanism for at least some of the configurational entropy in multicomponent melts, which in turn is a critical part of models of viscosity: at least in systems with high Al/Si ratios, for example, increase in Al/Si disorder with increasing T will a major part of this term. In many systems, however, the structural origins of Sconf remain mysterious. For both major and minor components, considerable information now exists to constrain models both of activity and of transport processes, but progress awaits development of useful model forms. Examples include new information on the local coordination of anions such as fluoride and chloride, which again show strong chemical ordering. Similarly, we now know a great deal about the concentration of minor "defect" species, that have been considered to be important to viscosity and diffusion (e.g. AlO5, SiO5, "excess" NBO). However, going from speculative

  8. Melting the Divide

    NASA Astrophysics Data System (ADS)

    Gibson, S. M.

    2014-12-01

    Presenting Quaternary Environmental Change to students who fall into Widening Participation criteria at the University of Cambridge, gives a unique opportunity to present academic debate in an approachable and entertaining way. Literally by discussing the melting of our ice caps, melts the divide Cambridge has between its reputation and the reality for the brightest, underprivileged, students. There is a balance between presenting cutting edge research with the need to come across as accessible (and importantly valuable to "learning"). Climate change over the Quaternary lends itself well to this aim. By lecturing groups of potential students through the entire Quaternary in an hour, stopping to discuss how our ancestors interacted with past Interglacials and what are the mechanisms driving change (in generalized terms), you are able to introduce cutting edge research (such as the latest NEEM ice core) to the students. This shows the evolution and importance of higher education and academic research. The lecture leads well onto group discussions (termed "supervisions" in Cambridge), to explore their opinions on the concern for present Anthropogenic Climate Change in relation to Past Climate Change after being presented with images that our ancestors "made it". Here discussion thrives off students saying obvious things (or sarcastic comments!) which quickly can lead into a deep technical discussion on their terms. Such discussions give the students a zest for higher education, simply throwing Ruddiman's (2003) "The Anthroprocene Started Several Thousand Years Ago" at them, questions in a second their concept of Anthropogenic Climate Change. Supervisions lend themselves well to bright, articulate, students and by offering these experiences to students of Widening Participation criteria we quickly melt the divide between the reputation of Cambridge ( and higher education as a whole) and the day to day practice. Higher education is not for the privileged, but a free and

  9. Decompression Device Using a Stainless Steel Tube and Wire for Treatment of Odontogenic Cystic Lesions: A Technical Report.

    PubMed

    Jung, Eun-Joo; Baek, Jin-A; Leem, Dae-Ho

    2014-11-01

    Decompression is considered an effective treatment for odontogenic cystic lesions in the jaw. A variety of decompression devices are successfully used for the treatment of keratocystic odontogenic tumors, radicular cysts, dentigerous cysts, and ameloblastoma. The purpose of these devices is to keep an opening between the cystic lesion and the oral environment during treatment. The aim of this report is to describe an effective decompression tube using a stainless steel tube and wire for treatment of jaw cystic lesions.

  10. Decompression Sickness in Aerospace Medicine: The Development of an Onboard Treatment Facility for the Shuttle-Orbiter Spacecraft.

    DTIC Science & Technology

    1979-06-01

    Center/NASA, Houston, Texas. April 12, 1979. 7. Davis, Jefferson C. et al . "Altitude Decompression Sickness: Hyperbaric Therapy REsults In 145 Cases...34 Aviation, Space, And Environmental Medicine, 48 (8): 722-730, 1977. 8. Davis, Jefferson C. et al . "Neurological Decompression Sickness: Report of 2...Edel, Peter 0. et al . "Interval at Sea Level Pressure Required to Prevent Decompression Sickness in Humans who Fly in Commerical Air- craft After

  11. Bubble reduction after decompression in the prawn Palaemon elegans by pretreatment with hyperbaric oxygen.

    PubMed

    Arieli, Y; Katsenelson, K; Arieli, R

    2007-01-01

    On the theory that bubbles originate from preexisting micronuclei, we previously demonstrated that pretreatment with hyperbaric O2 (HBO2) reduced the number of bubbles in the prawn decompressed from 203 kPa. In the present study, we examined the effect of two HBO2 pretreatment pressures (405 and 709 kPa) on prawns decompressed from a range of pressures between 203-810 kPa. Prawns from the experimental groups were pretreated with O2 at 405 or 709 kPa for 5 min (series A and series B, respectively). Prawns from the control groups were exposed only to air. Following pretreatment, prawns were exposed to air at the desired pressure until saturated with nitrogen, then subjected to rapid decompression and examined under a light microscope. Series A: HBO2 pretreatment at 405 kPa for 5 min significantly reduced the number of bubbles after decompression from 203, 304 and 405 kPa (p < 0.05). The total volume of accumulated gas was not affected by HBO2. Series B: Pretreatment with HBO2 at 709 kPa significantly reduced the number of bubbles after decompression from 203, 304, 507 and 608 kPa (p < 0.05). Total gas volume after decompression from 507 and 608 kPa was reduced as a result of pretreatment with O2. This study demonstrates that HBO2 pretreatment at 405 kPa is sufficient to reduce the number of bubbles that will emerge on decompression from several levels of compression.

  12. The effect of orbital decompression surgery on refraction and intraocular pressure in patients with thyroid orbitopathy

    PubMed Central

    Norris, J H; Ross, J J; Kazim, M; Selva, D; Malhotra, R

    2012-01-01

    Purpose To investigate the effect of orbital decompression surgery in thyroid orbitopathy (TO) on both refractive status and intraocular pressure (IOP). Patients and methods A prospective, multicentre, consecutive audit of patients undergoing thyroid decompression surgery. Indications for surgery included cosmetically unacceptable proptosis or corneal exposure. Exclusion criteria included the following: previous orbital surgery, glaucoma, corneal disease, steroid use in the preceding 12 months, or an acute optic neuropathy. Automated refraction, keratometry, pachymetry, Hertel exophthalmometry, and IOP were recorded at 1 month pre- and 3 months postoperatively. IOP using the Tono-Pen (mean of three readings) was measured in the primary, upgaze, and downgaze positions. Results Data were collected from 52 orbits of 33 patients (East Grinstead, New York, and Adelaide). There was no significant difference between pre- and postoperative data for sphere, cylinder, or central corneal thickness (CCT). The mean spherical equivalent was −0.43±1.49 D pre-operatively and −0.28±1.52 D postoperatively. The steepest meridian of corneal curvature was 93.1 degrees pre- and 94.2 degrees postoperatively, with no significant difference. Mean IOP significantly decreased when measuring by Goldmann applanation tonometry (GAT) (2.28 mm Hg, * P=0.001) and Tono-Pen (3.06 mm Hg, * P=<0.0001). IOP measured in upgaze was significantly greater than that in the primary position. Regression analysis between change in IOP and either Hertel exophthalmometry or the number of orbital walls decompressed was non-significant (*Student's t-test). Conclusion Patients with TO undergoing orbital decompression had, on average, with-the-rule astigmatism not affected by orbital decompression surgery. IOP was significantly reduced by decompression surgery although no relationship between IOP and the degree of decompression was observed. PMID:22261739

  13. Melt Heterogeneity and Degassing at MT Etna from Melt Inclusions

    NASA Astrophysics Data System (ADS)

    Salem, L. C.; Edmonds, M.; Maclennan, J.; Corsaro, R. A.

    2014-12-01

    The melts feeding Mt Etna, Italy, are rich in volatiles and drive long-lasting powerful eruptions of basaltic magma in both effusive and explosive styles of activity. The volatile systematics of the volcanic system are well understood through melt inclusion and volcanic gas studies. Etna's melts are generated from a complex mantle setting, with subduction-related chemical modifications as well as OIB-type features, and then the melts must travel through thick carbonate-rich crust. The continual influx of mantle-derived volatile-rich magma controls the major compositional and eruptive features of Mount Etna and magma mixing has been recognized as an important process driving large eruptions [Kamenetsky, 2007]. Our study focusses on the 1669 eruption, the largest in historical times. Olivine-hosted melt inclusions were analyzed for volatile, trace and major elements using electron microprobe and ion probe (SIMS). We use volatile systematics and geochemical data to deconvolve mantle-derived heterogeneity from melt mixing and crystal fractionation. Our data are well described by a mixing trend between two distinct melts: a CO2-rich (CO2~1000ppm), incompatible trace element depleted melt (La/Yb~16), and a CO2-poor, enriched melt. The mixing also generates a strong correlation between Sr and CO2 in the melt inclusions dataset, reflecting the presence of a strong Sr anomaly in one of the end-member melts. We investigate the origin of this Sr anomaly by considering plagioclase dissolution and crustal assimilation. We also investigate degassing processes in the crust and plumbing system of the volcano. We compare our results with similar studies of OIB and arc-related basalts elsewhere and assess the implications for linking eruption size and style with the nature of the mantle-derived melts. Kamenetsky et al. (2007) Geology 35, 255-258.

  14. REE chemistry of MORB and OIB explained by microchemical disequilibrium melting models

    NASA Astrophysics Data System (ADS)

    Grose, C. J.; Afonso, J. C.

    2015-12-01

    We have developed a two-dimensional numerical model of multi-phase coarsening, diffusive trace element partitioning, and near-fractional melting. The model is applied to decompression melting of MORB and OIB sources and the prediction of REE (La, Sm, and Yb) in erupted lavas. We show that the major features in global OIB REE systematics are easily explained via the so-called LID effect. The properties of models which do explain the data indicate that the OIB source cannot be hot (>1400°C) and may be compositionally similar to the MORB source. Moreover, our models predict that the thermo-mechanical LAB temperature is about 1225°C, average grain radii in the OIB source is on the order of 2-5 mm, and the bulk source compositions of REE are about 2-7 times higher than previous estimates.

  15. Pudendal nerve decompression in perineology : a case series

    PubMed Central

    Beco, Jacques; Climov, Daniela; Bex, Michèle

    2004-01-01

    Background Perineodynia (vulvodynia, perineal pain, proctalgia), anal and urinary incontinence are the main symptoms of the pudendal canal syndrome (PCS) or entrapment of the pudendal nerve. The first aim of this study was to evaluate the effect of bilateral pudendal nerve decompression (PND) on the symptoms of the PCS, on three clinical signs (abnormal sensibility, painful Alcock's canal, painful "skin rolling test") and on two neurophysiological tests: electromyography (EMG) and pudendal nerve terminal motor latencies (PNTML). The second aim was to study the clinical value of the aforementioned clinical signs in the diagnosis of PCS. Methods In this retrospective analysis, the studied sample comprised 74 female patients who underwent a bilateral PND between 1995 and 2002. To accomplish the first aim, the patients sample was compared before and at least one year after surgery by means of descriptive statistics and hypothesis testing. The second aim was achieved by means of a statistical comparison between the patient's group before the operation and a control group of 82 women without any of the following signs: prolapse, anal incontinence, perineodynia, dyschesia and history of pelvi-perineal surgery. Results When bilateral PND was the only procedure done to treat the symptoms, the cure rates of perineodynia, anal incontinence and urinary incontinence were 8/14, 4/5 and 3/5, respectively. The frequency of the three clinical signs was significantly reduced. There was a significant reduction of anal and perineal PNTML and a significant increase of anal richness on EMG. The Odd Ratio of the three clinical signs in the diagnosis of PCS was 16,97 (95% CI = 4,68 – 61,51). Conclusion This study suggests that bilateral PND can treat perineodynia, anal and urinary incontinence. The three clinical signs of PCS seem to be efficient to suspect this diagnosis. There is a need for further studies to confirm these preliminary results. PMID:15516268

  16. The effect of simulated weightlessness on hypobaric decompression sickness

    NASA Technical Reports Server (NTRS)

    Balldin, Ulf I.; Pilmanis, Andrew A.; Webb, James T.

    2002-01-01

    BACKGROUND: A discrepancy exists between the incidence of ground-based decompression sickness (DCS) during simulated extravehicular activity (EVA) at hypobaric space suit pressure (20-40%) and crewmember reports during actual EVA (zero reports). This could be due to the effect of gravity during ground-based DCS studies. HYPOTHESIS: At EVA suit pressures of 29.6 kPa (4.3 psia), there is no difference in the incidence of hypobaric DCS between a control group and group exposed to simulated weightlessness (supine body position). METHODS: Male subjects were exposed to a hypobaric pressure of 29.6 kPa (4.3 psi) for up to 4 h. The control group (n = 26) pre-oxygenated for 60 min (first 10 min exercising) before hypobaric exposure and walking around in the altitude chamber. The test group (n = 39) remained supine for a 3 h prior to and during the 60-min pre-oxygenation (also including exercise) and at hypobaric pressure. DCS symptoms and venous gas emboli (VGE) at hypobaric pressure were registered. RESULTS: DCS occurred in 42% in the control and in 44% in simulated weightlessness group (n.s.). The mean time for DCS to develop was 112 min (SD +/- 61) and 123 min (+/- 67), respectively. VGE occurred in 81% of the control group subjects and in 51% of the simulated weightlessness subjects (p = 0.02), while severe VGE occurred in 58% and 33%, respectively (p = 0.08). VGE started after 113 min (+/- 43) in the control and after 76 min (+/- 64) in the simulated weightlessness group. CONCLUSIONS: No difference in incidence of DCS was shown between control and simulated weightlessness conditions. VGE occurred more frequently during the control condition with bubble-releasing arm and leg movements.

  17. Melting in Martian Snowbanks

    NASA Technical Reports Server (NTRS)

    Zent, A. P.; Sutter, B.

    2005-01-01

    Precipitation as snow is an emerging paradigm for understanding water flow on Mars, which gracefully resolves many outstanding uncertainties in climatic and geomorphic interpretation. Snowfall does not require a powerful global greenhouse to effect global precipitation. It has long been assumed that global average temperatures greater than 273K are required to sustain liquid water at the surface via rainfall and runoff. Unfortunately, the best greenhouse models to date predict global mean surface temperatures early in Mars' history that differ little from today's, unless exceptional conditions are invoked. Snowfall however, can occur at temperatures less than 273K; all that is required is saturation of the atmosphere. At global temperatures lower than 273K, H2O would have been injected into the atmosphere by impacts and volcanic eruptions during the Noachian, and by obliquity-driven climate oscillations more recently. Snow cover can accumulate for a considerable period, and be available for melting during local spring and summer, unless sublimation rates are sufficient to remove the entire snowpack. We decided to explore the physics that controls the melting of snow in the high-latitude regions of Mars to understand the frequency and drainage of snowmelt in the high martian latitudes.

  18. Shortcuts to adiabaticity by counterdiabatic driving for trapped-ion displacement in phase space

    PubMed Central

    An, Shuoming; Lv, Dingshun; del Campo, Adolfo; Kim, Kihwan

    2016-01-01

    The application of adiabatic protocols in quantum technologies is severely limited by environmental sources of noise and decoherence. Shortcuts to adiabaticity by counterdiabatic driving constitute a powerful alternative that speed up time-evolution while mimicking adiabatic dynamics. Here we report the experimental implementation of counterdiabatic driving in a continuous variable system, a shortcut to the adiabatic transport of a trapped ion in phase space. The resulting dynamics is equivalent to a ‘fast-motion video' of the adiabatic trajectory. The robustness of this protocol is shown to surpass that of competing schemes based on classical local controls and Fourier optimization methods. Our results demonstrate that shortcuts to adiabaticity provide a robust speedup of quantum protocols of wide applicability in quantum technologies. PMID:27669897

  19. Shear Faulting and Adiabatic Heating: Experimental Results from Ice

    NASA Astrophysics Data System (ADS)

    Golding, N.; Schulson, E. M.; Renshaw, C. E.

    2011-12-01

    Ice exhibits two distinct modes of shear faulting (Golding et al. Acta Materialia, 2010;58:5043), namely frictional or Coulombic (C) faulting under moderate levels of confinement and non-frictional or plastic (P) faulting under high levels of confinement. The mechanisms governing C-faulting have previously been discussed in connection with the comb-crack model (Renshaw & Schulson Nature, 2001;412:897). Here we examine the physical process[es] that trigger P-faulting. Systematic experiments on laboratory grown granular and columnar polycrystalline ice loaded triaxially under a high degree of confinement at -10 oC to -40 oC at applied strain rates 10-5 s-1 to 10-1 s-1 trace the micro-mechanical evolution of P-faulting. Terminal failure is characterized by a sudden brittle-like loss in load bearing capacity, the development of a narrow shear band, comprised of recrystallized grains and oriented on a plane of maximum shear, and localized heating. Possible mechanisms considered to account for the localization include: 1) adiabatic heating, 2) localized material softening through a reduction in dislocation density caused by dynamic recrystallization and 3) a transition from power-law creep to grain-size-dependent diffusional creep as a result of grain refinement caused by dynamic recrystallization. Our results indicate that, although recrystallization develops dynamically during loading, microstructural development does not significantly affect shear localization in ice. Nor does it affect the character of the fault. The minimum levels of deformation required to generate faulting are found to be consistent with those predicted for adiabatic shear instability. The present observations suggest that under specific conditions adiabatic heating, rather than dynamic recrystallization, may lead to material instability and shear faulting.

  20. Adiabatic quantum computing with spin qubits hosted by molecules.

    PubMed

    Yamamoto, Satoru; Nakazawa, Shigeaki; Sugisaki, Kenji; Sato, Kazunobu; Toyota, Kazuo; Shiomi, Daisuke; Takui, Takeji

    2015-01-28

    A molecular spin quantum computer (MSQC) requires electron spin qubits, which pulse-based electron spin/magnetic resonance (ESR/MR) techniques can afford to manipulate for implementing quantum gate operations in open shell molecular entities. Importantly, nuclear spins, which are topologically connected, particularly in organic molecular spin systems, are client qubits, while electron spins play a role of bus qubits. Here, we introduce the implementation for an adiabatic quantum algorithm, suggesting the possible utilization of molecular spins with optimized spin structures for MSQCs. We exemplify the utilization of an adiabatic factorization problem of 21, compared with the corresponding nuclear magnetic resonance (NMR) case. Two molecular spins are selected: one is a molecular spin composed of three exchange-coupled electrons as electron-only qubits and the other an electron-bus qubit with two client nuclear spin qubits. Their electronic spin structures are well characterized in terms of the quantum mechanical behaviour in the spin Hamiltonian. The implementation of adiabatic quantum computing/computation (AQC) has, for the first time, been achieved by establishing ESR/MR pulse sequences for effective spin Hamiltonians in a fully controlled manner of spin manipulation. The conquered pulse sequences have been compared with the NMR experiments and shown much faster CPU times corresponding to the interaction strength between the spins. Significant differences are shown in rotational operations and pulse intervals for ESR/MR operations. As a result, we suggest the advantages and possible utilization of the time-evolution based AQC approach for molecular spin quantum computers and molecular spin quantum simulators underlain by sophisticated ESR/MR pulsed spin technology.

  1. Optical force on atoms with periodic adiabatic rapid passage sequences

    NASA Astrophysics Data System (ADS)

    Miao, Xiyue

    Adiabatic Rapid Passage (ARP) is a long-existing method to invert the population of a two-level nuclear spin system. Its extension to the optical domain necessitates a frequency chirped light pulse to interact with a two-level atom through dipole interaction. In this dissertation ARP processes for various pulse schemes and pulse parameters have been studied theoretically and experimentally. The non-adiabatic transition probability of ARP was quantified to characterize the efficiency of ARP for population transfer. Unanticipated regularities were found in the pulse parameter space. ARP sequences in periodic phase coherent counter-propagating light pulses can be used to produce large optical forces on atoms. The magnitude of the force is proportional to the pulse repetition rate. So the force can be much larger than the usual radiative force if the pulse repetition rate is much higher than the spontaneous emission rate. The behavior of the atoms in such periodic ARP fields without spontaneous emission is well described by a periodic Hamiltonian. By investigating the evolution of the Bloch vector on the Bloch sphere, we related the average optical force on atoms to the non-adiabatic transition probability of a single pulse. Syncopation time has to be introduced in the pulsing scheme to produce a directional force in the presence of spontaneous emission. Experimentally, we observed the force on He* atoms by the deflection of the atomic beam with periodic chirped pulses from counter-propagating pulse trains. The chirped pulse train was realized by synchronized phase and amplitude modulation of the light from a cw diode laser. The Fourier spectrum of the modulated light was monitored to guarantee the quality of the chirped pulses. The measured ARP forces are about half of the theoretical predictions. Not only have we shown that such forces are huge and robust, but we have also been able to map the forces in the two dimensional pulse parameter space. The force

  2. Redox freezing and melting in the Earth's deep mantle resulting from carbon-iron redox coupling.

    PubMed

    Rohrbach, Arno; Schmidt, Max W

    2011-04-14

    Very low seismic velocity anomalies in the Earth's mantle may reflect small amounts of melt present in the peridotite matrix, and the onset of melting in the Earth's upper mantle is likely to be triggered by the presence of small amounts of carbonate. Such carbonates stem from subducted oceanic lithosphere in part buried to depths below the 660-kilometre discontinuity and remixed into the mantle. Here we demonstrate that carbonate-induced melting may occur in deeply subducted lithosphere at near-adiabatic temperatures in the Earth's transition zone and lower mantle. We show experimentally that these carbonatite melts are unstable when infiltrating ambient mantle and are reduced to immobile diamond when recycled at depths greater than ∼250 kilometres, where mantle redox conditions are determined by the presence of an (Fe,Ni) metal phase. This 'redox freezing' process leads to diamond-enriched mantle domains in which the Fe(0), resulting from Fe(2+) disproportionation in perovskites and garnet, is consumed but the Fe(3+) preserved. When such carbon-enriched mantle heterogeneities become part of the upwelling mantle, diamond will inevitably react with the Fe(3+) leading to true carbonatite redox melting at ∼660 and ∼250 kilometres depth to form deep-seated melts in the Earth's mantle.

  3. Graphite solubility and co-vesiculation in basalt-like melts at one-ATM

    NASA Technical Reports Server (NTRS)

    Colson, R. O.

    1993-01-01

    The identity and source of the vapor phase that caused lunar lava-fountaining and vesiculation in lunar basalts continues to be of interest because of its implications for the composition and state of the lunar interior and because of its implications for lunar resources. In light of the apparent near-absence of H2O on the Moon, it has been suggested that the vapor phase may be CO2-CO. This premise is supported by the presence of carbon on the surface of volcanic glass beads. However, although the rapid exsolution of CO2 from a melt during decompression may be consistent with firefountaining, it fails to provide a satisfying explanation for vesiculation in mare basalt where exsolution of the gas phase would more reasonably be related to cooling/crystallization at low pressure rather than decompression from high pressure. Also, geochemical trends in lunar volcanic glasses suggest that their source has an oxygen fugacity more reducing than the iron-wustite buffer, an oxygen fugacity that is inconsistent with presence of dissolved CO2-CO at depth. The results of experiments in which a vesicular 'basalt' is produced from a melt equilibrated with graphite and pure CO gas at one atmosphere pressure are reported. The vesiculation is apparently related to exsolution of CO or a CO species during cooling of the melt or growth of quench crystals. Additionally, particulate carbon dispersed through the quenched sample suggests that elemental carbon is either in solution in the melt prior to quenching or tends to go into suspension perhaps as colloid-like particles. These two observations may provide insight into the nature of fire-fountaining and vesiculation on the Moon.

  4. Melting of Ice under Pressure

    SciTech Connect

    Schwegler, E; Sharma, M; Gygi, F; Galli, G

    2008-07-31

    The melting of ice under pressure is investigated with a series of first principles molecular dynamics simulations. In particular, a two-phase approach is used to determine the melting temperature of the ice-VII phase in the range of 10 to 50 GPa. Our computed melting temperatures are consistent with existing diamond anvil cell experiments. We find that for pressures between 10 to 40 GPa, ice melts as a molecular solid. For pressures above {approx}45 GPa there is a sharp increase in the slope of the melting curve due to the presence of molecular dissociation and proton diffusion in the solid, prior to melting. The onset of significant proton diffusion in ice-VII as a function of increasing temperature is found to be gradual and bears many similarities to that of a type-II superionic solid.

  5. Melting of ice under pressure.

    PubMed

    Schwegler, Eric; Sharma, Manu; Gygi, François; Galli, Giulia

    2008-09-30

    The melting of ice under pressure is investigated with a series of first-principles molecular dynamics simulations. In particular, a two-phase approach is used to determine the melting temperature of the ice-VII phase in the range of 10-50 GPa. Our computed melting temperatures are consistent with existing diamond anvil cell experiments. We find that for pressures between 10 and 40 GPa, ice melts as a molecular solid. For pressures above approximately 45 Gpa, there is a sharp increase in the slope of the melting curve because of the presence of molecular dissociation and proton diffusion in the solid before melting. The onset of significant proton diffusion in ice-VII as a function of increasing temperature is found to be gradual and bears many similarities to that of a type-II superionic solid.

  6. Diabatic Versus Adiabatic Calculation of Torsion-Vibration Interactions

    NASA Astrophysics Data System (ADS)

    Hougen, Jon T.

    2013-06-01

    The introductory part of this talk will deal briefly with two historical topics: (i) use of the words adiabatic, nonadiabatic, and diabatic in thermodynamics and quantum mechanics, and (ii) application of diabatic and adiabatic ideas to vibrational energy level calculations for a pair of diatomic-molecule potential energy curves exhibiting an avoided crossing. The main part of the talk will be devoted to recent work with Li-Hong Xu and Ron Lees on how ab initio projected frequency calculations for small-amplitude vibrations along the large-amplitude internal rotation path in methanol can best be used to help guide experimental assignments and fits in the IR vibrational spectrum. The three CH stretching vibrations for CH_{3}OH can conveniently be represented as coefficients multiplying three different types of basis vibrations, i.e., as coefficients of: (i) the local mode C-H_i bond displacements δr_{i} for hydrogens H_{1}, H_{2} and H_{3} of the methyl top, (ii) symmetrized linear combinations of the three δr_{i} of species A_{1} oplus E in the permutation-inversion group G_{6} = C_{3v} appropriate for methanol, or (iii) symmetrized linear combinations of the three δr_{i} of species 2A_{1} oplus A_{2} in the permutation-inversion group G_{6}. In this talk, we will focus on diabatic and adiabatic computations for the A_{1} oplus E basis vibrations of case (ii) above. We will briefly explain how Jahn-Teller-like and Renner-Teller-like torsion-vibration interaction terms occurring in the potential energy expression in the diabatic calculation become torsion-vibration Coriolis interaction terms occurring in the kinetic energy expression of the adiabatic calculations, and also show how, for algebraically solvable parameter choices, the same energy levels are obtained from either calculation. A final conclusion as to which approach is computationally superior for the numerical data given in a quantum chemistry output file has not yet been arrived at.

  7. Major Steps in the Discovery of Adiabatic Shear Bands

    NASA Astrophysics Data System (ADS)

    Dodd, Bradley; Walley, Stephen M.; Yang, Rong; Nesterenko, Vitali F.

    2015-10-01

    The standard story of the discovery of adiabatic shear bands is that it began with the American researchers Zener and Hollomon's famous 1944 paper where the phenomenon was first reported and named. However, a recent discovery by one of us (SMW) in the Cambridge University Library has shown that the phenomenon was discovered and described by a Russian researcher, V.P. Kravz-Tarnavskii, in 1928. A follow-up paper was published by two of his colleagues in 1935. Translations of the 1928 and 1935 papers may be found at http://arxiv.org/abs/1410.1353.

  8. Adiabatic transport of qubits around a black hole

    NASA Astrophysics Data System (ADS)

    Viennot, David; Moro, Olivia

    2017-03-01

    We consider localized qubits evolving around a black hole following a quantum adiabatic dynamics. We develop a geometric structure (based on fibre bundles) permitting to describe the quantum states of a qubit and the spacetime geometry in a single framework. The quantum decoherence induced by the black hole on the qubit is analysed in this framework (the role of the dynamical and geometric phases in this decoherence is treated), especially for the quantum teleportation protocol when one qubit falls to the event horizon. A simple formula to compute the fidelity of the teleportation is derived. The case of a Schwarzschild black hole is analysed.

  9. From Classical Nonlinear Integrable Systems to Quantum Shortcuts to Adiabaticity

    NASA Astrophysics Data System (ADS)

    Okuyama, Manaka; Takahashi, Kazutaka

    2016-08-01

    Using shortcuts to adiabaticity, we solve the time-dependent Schrödinger equation that is reduced to a classical nonlinear integrable equation. For a given time-dependent Hamiltonian, the counterdiabatic term is introduced to prevent nonadiabatic transitions. Using the fact that the equation for the dynamical invariant is equivalent to the Lax equation in nonlinear integrable systems, we obtain the counterdiabatic term exactly. The counterdiabatic term is available when the corresponding Lax pair exists and the solvable systems are classified in a unified and systematic way. Multisoliton potentials obtained from the Korteweg-de Vries equation and isotropic X Y spin chains from the Toda equations are studied in detail.

  10. Relativistic blast waves in two dimensions. I - The adiabatic case

    NASA Technical Reports Server (NTRS)

    Shapiro, P. R.

    1979-01-01

    Approximate solutions are presented for the dynamical evolution of strong adiabatic relativistic blast waves which result from a point explosion in an ambient gas in which the density varies both with distance from the explosion center and with polar angle in axisymmetry. Solutions are analytical or quasi-analytical for the extreme relativistic case and numerical for the arbitrarily relativistic case. Some general properties of nonplanar relativistic shocks are also discussed, including the incoherence of spherical ultrarelativistic blast-wave fronts on angular scales greater than the reciprocal of the shock Lorentz factor, as well as the conditions for producing blast-wave acceleration.

  11. Magnetic shielding for a spaceborne adiabatic demagnetization refrigerator (ADR)

    NASA Technical Reports Server (NTRS)

    Warner, Brent A.; Shirron, Peter J.; Castles, Stephen H.; Serlemitsos, Aristides T.

    1991-01-01

    The Goddard Space Flight Center has studied magnetic shielding for an adiabatic demagnetization refrigerator. Four types of shielding were studied: active coils, passive ferromagnetic shells, passive superconducting coils, and passive superconducting shells. The passive superconducting shells failed by allowing flux penetration. The other three methods were successful, singly or together. Experimental studies of passive ferromagnetic shielding are compared with calculations made using the Poisson Group of programs, distributed by the Los Alamos Accelerator Code Group of the Los Alamos National Laboratory. Agreement between calculation and experiment is good. The ferromagnetic material is a silicon iron alloy.

  12. More bang for your buck: Super-adiabatic quantum engines

    PubMed Central

    Campo, A. del; Goold, J.; Paternostro, M.

    2014-01-01

    The practical untenability of the quasi-static assumption makes any realistic engine intrinsically irreversible and its operating time finite, thus implying friction effects at short cycle times. An important technological goal is thus the design of maximally efficient engines working at the maximum possible power. We show that, by utilising shortcuts to adiabaticity in a quantum engine cycle, one can engineer a thermodynamic cycle working at finite power and zero friction. Our findings are illustrated using a harmonic oscillator undergoing a quantum Otto cycle. PMID:25163421

  13. Non-Adiabatic Holonomic Quantum Gates in an atomic system

    NASA Astrophysics Data System (ADS)

    Azimi Mousolou, Vahid; Canali, Carlo M.; Sjoqvist, Erik

    2012-02-01

    Quantum computation is essentially the implementation of a universal set of quantum gate operations on a set of qubits, which is reliable in the presence of noise. We propose a scheme to perform robust gates in an atomic four-level system using the idea of non-adiabatic holonomic quantum computation proposed in [1]. The gates are realized by applying sequences of short laser pulses that drive transitions between the four energy levels in such a way that the dynamical phases vanish. [4pt] [1] E. Sjoqvist, D.M. Tong, B. Hessmo, M. Johansson, K. Singh, arXiv:1107.5127v2 [quant-ph

  14. Metallization of nanofilms in strong adiabatic electric fields.

    PubMed

    Durach, Maxim; Rusina, Anastasia; Kling, Matthias F; Stockman, Mark I

    2010-08-20

    We introduce an effect of metallization of dielectric nanofilms by strong, adiabatically varying electric fields. The metallization causes optical properties of a dielectric film to become similar to those of a plasmonic metal (strong absorption and negative permittivity at low optical frequencies). This is a quantum effect, which is exponentially size-dependent, occurring at fields on the order of 0.1 V/Å and pulse durations ranging from ∼1 fs to ∼10 ns for a film thickness of 3-10 nm.

  15. Metallization of Nanofilms in Strong Adiabatic Electric Fields

    NASA Astrophysics Data System (ADS)

    Durach, Maxim; Rusina, Anastasia; Kling, Matthias F.; Stockman, Mark I.

    2010-08-01

    We introduce an effect of metallization of dielectric nanofilms by strong, adiabatically varying electric fields. The metallization causes optical properties of a dielectric film to become similar to those of a plasmonic metal (strong absorption and negative permittivity at low optical frequencies). This is a quantum effect, which is exponentially size-dependent, occurring at fields on the order of 0.1V/Å and pulse durations ranging from ˜1fs to ˜10ns for a film thickness of 3-10 nm.

  16. Salt materials testing for a spacecraft adiabatic demagnetization refrigerator

    NASA Astrophysics Data System (ADS)

    Savage, M. L.; Kittel, P.; Roellig, T.

    As part of a technology development effort to qualify adiabatic demagnetization refrigerators for use in a NASA spacecraft, such as the Space Infrared Telescope Facility, a study of low temperature characteristics, heat capacity and resistance to dehydration was conducted for different salt materials. This report includes results of testing with cerrous metaphosphate, several synthetic rubies, and chromic potassium alum (CPA). Preliminary results show that CPA may be suitable for long-term spacecraft use, provided that the salt is property encapsulated. Methods of salt pill construction and testing for all materials are discussed, as well as reliability tests. Also, the temperature regulation scheme and the test cryostat design are briefly discussed.

  17. Non-adiabatic pumping in an oscillating-piston model

    NASA Astrophysics Data System (ADS)

    Chuchem, Maya; Dittrich, Thomas; Cohen, Doron

    2012-05-01

    We consider the prototypical "piston pump" operating on a ring, where a circulating current is induced by means of an AC driving. This can be regarded as a generalized Fermi-Ulam model, incorporating a finite-height moving wall (piston) and non-trivial topology (ring). The amount of particles transported per cycle is determined by a layered structure of phase space. Each layer is characterized by a different drift velocity. We discuss the differences compared with the adiabatic and Boltzmann pictures, and highlight the significance of the "diabatic" contribution that might lead to a counter-stirring effect.

  18. Optimized sympathetic cooling of atomic mixtures via fast adiabatic strategies

    SciTech Connect

    Choi, Stephen; Sundaram, Bala; Onofrio, Roberto

    2011-11-15

    We discuss fast frictionless cooling techniques in the framework of sympathetic cooling of cold atomic mixtures. It is argued that optimal cooling of an atomic species--in which the deepest quantum degeneracy regime is achieved--may be obtained by means of sympathetic cooling with another species whose trapping frequency is dynamically changed to maintain constancy of the Lewis-Riesenfeld adiabatic invariant. Advantages and limitations of this cooling strategy are discussed, with particular regard to the possibility of cooling Fermi gases to a deeper degenerate regime.

  19. Salt materials testing for a spacecraft adiabatic demagnetization refrigerator

    NASA Technical Reports Server (NTRS)

    Savage, M. L.; Kittel, P.; Roellig, T.

    1990-01-01

    As part of a technology development effort to qualify adiabatic demagnetization refrigerators for use in a NASA spacecraft, such as the Space Infrared Telescope Facility, a study of low temperature characteristics, heat capacity and resistance to dehydration was conducted for different salt materials. This report includes results of testing with cerrous metaphosphate, several synthetic rubies, and chromic potassium alum (CPA). Preliminary results show that CPA may be suitable for long-term spacecraft use, provided that the salt is property encapsulated. Methods of salt pill construction and testing for all materials are discussed, as well as reliability tests. Also, the temperature regulation scheme and the test cryostat design are briefly discussed.

  20. Propagation of laser pulses under conditions of adiabatic population transfer

    SciTech Connect

    Arkhipkin, V G; Manushkin, D V; Timofeev, V P

    1998-12-31

    A medium of three-level absorbing atoms is considered under conditions of adiabatic population transfer. A study is made of the characteristics of spatial propagation of two delayed (relative to one another) Gaussian pulses. It is shown that selective excitation of a two-photon resonant state with a near-unity probability is conserved over the length of a medium, which is considerably greater than the absorption length of a weak probe pulse in the absence of the second field. (physical basis of quantum electronics)