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Sample records for dependent void swelling

  1. ''The Incubation Period for Void Swelling and its Dependence on Temperature, Dose Rate, and Dislocation Structure Evolution''

    SciTech Connect

    Surh, M P; Sturgeon, J B; Wolfer, W G

    2002-06-13

    Void swelling in structural materials used for nuclear reactors is characterized by an incubation period whose duration largely determines the usefulness of the material for core components. Significant evolution of the dislocation and void microstructures that control radiation-induced swelling can occur during this period. Thus, a theory of incubation must treat time-dependent void nucleation in combination with dislocation evolution, in which the sink strengths of voids and dislocations change in concert. We present theoretical results for void nucleation and growth including the time-dependent, self-consistent coupling of point defect concentrations to the evolution of both void populations and dislocation density. Simulations show that the incubation radiation dose is a strong function of the starting dislocation density and of the dislocation bias factors for vacancy and interstitial absorption. Irradiation dose rate and temperature also affect the duration of incubation. The results are in general agreement with experiment for high purity metals.

  2. Erratum for: Master equation and Fokker-Planck methods for void nucleation and growth in irradiation swelling, Vacancy cluster evolution and swelling in irradiated 316 stainless steel and Radiation swelling behavior and its dependence on temperature, dose

    SciTech Connect

    Surh, M P; Sturgeon, J B; Wolfer, W G

    2005-01-03

    We have recently discovered an error in our void nucleation code used in three prior publications [1-3]. A term was omitted in the model for vacancy re-emission that (especially at high temperature) affects void nucleation and growth during irradiation as well as void annealing and Ostwald ripening of the size distribution after irradiation. The omission was not immediately detected because the calculations predict reasonable void densities and swelling behaviors when compared to experiment at low irradiation temperatures, where void swelling is prominent. (Comparable neutron irradiation experiments are less prevalent at higher temperatures, e.g., > 500 C.)

  3. COMPOSITIONAL AND TEMPERATURE DEPENDENCE OF VOID SWELLING IN MODEL Fe-Cr BASE ALLOYS IRRADIATED IN THE EBR-II FAST REACTOR

    SciTech Connect

    Sencer, Bulent H.; Garner, Francis A.

    2001-04-01

    A series of annealed and aged Fe-xCr, Fe-12Cr-yC and Fe-12Cr-0.1C-zMo model alloys were irradiated in EBR-II at eight temperatures between 400 and 650C and dose levels ranging from 35 to 131 dpa. Swelling-induced density changes observed in the binary alloys generally peaked at mid-chromium levels, with the chromium and temperature dependence expressed primarily in the duration of the transient regime. The steady state swelling rate at the lower irradiation temperatures was much higher than previous estimates, reaching ~0.2%/dpa and possibly still climbing at higher neutron exposures. The dependence of swelling on molybdenum and carbon was more complex, depending on whether the temperature was relatively low or high. At temperatures of 482oC and above the effect of carbon additions was very pronounced, with swelling of Fe-12Cr jumping dramatically from near zero at 0.002%C to 6-10% at 0.1%C. This indicates that the major determinant of the composition and temperature dependence probably lies in the duration of the nucleation-dominated transient regime of swelling and not primarily in the steady-state swelling rate as previously envisioned. This raises the possibility that significant swelling may occur earlier in fusion and spallation neutron spectra where high gas generation rates may assist void nucleation.

  4. Irradiation creep relaxation of void swelling-driven stresses

    NASA Astrophysics Data System (ADS)

    Hall, M. M.

    2013-01-01

    Swelling-driven-creep test specimens are used to measure the compressive stresses that develop due to constraint of irradiation void swelling. These specimens use a previously non-irradiated 20% CW Type 316 stainless steel holder to axially restrain two Type 304 stainless steel tubular specimens that were previously irradiated in the US Experimental Breeder Reactor (EBR-II) at 490 °C. One specimen was previously irradiated to fluence levels in the void nucleation regime (9 dpa) and the other in the quasi-steady void growth regime (28 dpa). A lift-off compliance measurement technique was used post-irradiation to determine compressive stresses developed during reirradiation of the two specimen assemblies in Row 7 of EBR-II at temperatures of 547 °C and 504 °C, respectively, to additional damage levels each of about 5 dpa. Results obtained on the higher fluence swelling-driven-creep specimen show that compressive stress due to constraint of swelling retards void swelling to a degree that is consistent with active load uniaxial compression specimens that were irradiated as part of a previously reported multiaxial in-reactor creep experiment. Swelling results obtained on the lower fluence swelling-driven creep specimen show a much larger effect of compressive stress in reducing swelling, demonstrating that the larger effect of stress on swelling is on void nucleation as compared to void growth. Test results are analyzed using a recently proposed multiaxial creep-swelling model.

  5. Methodology for determining void swelling at very high damage under ion irradiation

    NASA Astrophysics Data System (ADS)

    Getto, E.; Sun, K.; Taller, S.; Monterrosa, A. M.; Jiao, Z.; Was, G. S.

    2016-08-01

    At very high damage levels in ion irradiated samples, the decrease in effective density of the irradiated material due to void swelling can lead to errors in quantifying swelling. HT9 was pre-implanted with 10 appm He and subjected to a raster-scanned beam with a damage rate of ∼1 × 10-3 dpa/s at 460oC. Voids were characterized from 0 to 1300 nm. Fixed damage rate and fixed depth methods were developed to account for damage-dependent porosity increase and resulting dependence on depth. The fixed depth method was more appropriate as it limits undue effects from the injected interstitial while maintaining a usable void distribution. By keeping the depth fixed and accounting for the change in damage rate due to reduced density, the steady state swelling rate was 10% higher than calculation of swelling from raw data. This method is easily translatable to other materials, ion types and energies and limits the impact of the injected interstitial.

  6. Effects of titanium additions to austenitic ternary alloys on microstructural evolution and void swelling

    SciTech Connect

    Okita, T; Wolfer, W G; Garner, F A; Sekimura, N

    2003-12-01

    Ternary austenitic model alloys were modified with 0.25 wt.% titanium and irradiated in FFTF reactor at dose rates ranging over more than two orders in magnitude. While lowering of dose rate strongly increases swelling by shortening the incubation dose, the steady state swelling rate is not affected by dose rate. Although titanium addition strongly alters the void microstructure, swelling at {approx} 420 C does not change with titanium additions, but the sensitivity to dose rate is preserved.

  7. Effect of irradiation temperature on void swelling of China Low Activation Martensitic steel (CLAM)

    SciTech Connect

    Zhao Fei; Qiao Jiansheng; Huang Yina; Wan Farong Ohnuki, Soumei

    2008-03-15

    CLAM is one composition of a Reduced Activation Ferritic/Martensitic steel (RAFM), which is being studied in a number of institutes and universities in China. The effect of electron-beam irradiation temperature on irradiation swelling of CLAM was investigated by using a 1250 kV High Voltage Electron Microscope (HVEM). In-situ microstructural observations indicated that voids formed at each experimental temperature - 723 K, 773 K and 823 K. The size and number density of voids increased with increasing irradiation dose at each temperature. The results show that CLAM has good swelling resistance. The maximum void swelling was produced at 723 K; the swelling was about 0.3% when the irradiation damage was 13.8 dpa.

  8. Void swelling in high dose ion-irradiated reduced activation ferritic-martensitic steels

    NASA Astrophysics Data System (ADS)

    Wang, Xu; Monterrosa, Anthony M.; Zhang, Feifei; Huang, Hao; Yan, Qingzhi; Jiao, Zhijie; Was, Gary S.; Wang, Lumin

    2015-07-01

    To determine the void swelling resistance of reduced-activation ferritic-martensitic steels CNS I and CNS II at high doses, ion irradiation was performed up to 188 dpa (4.6 × 1017 ion/cm2) at 460 °C using 5 MeV Fe++ ions. Helium was pre-implanted at levels of 10 and 100 appm at room temperature to investigate the role of helium on void swelling. Commercial FM steel T91 was also irradiated in this condition and the swelling results are of included in this paper as a reference. Voids were observed in all conditions. The 9Cr CNS I samples implanted with 10 appm helium exhibited lower swelling than 9Cr T91 irradiated at the same condition. The 12Cr CNS II with 10 and 100 appm helium showed significantly lower swelling than CNS I and T91. The swelling rate for CNS I and CNS II were determined to be 0.02%/dpa and 0.003%/dpa respectively. Increasing the helium content from 10 to 100 appm shortened the incubation region and increased the void density but had no effect on the swelling rates.

  9. Assessment of void swelling in austenitic stainless steel PWR core internals.

    SciTech Connect

    Chung, H. M.; Energy Technology

    2006-01-31

    As many pressurized water reactors (PWRs) age and life extension of the aged plants is considered, void swelling behavior of austenitic stainless steel (SS) core internals has become the subject of increasing attention. In this report, the available database on void swelling and density change of austenitic SSs was critically reviewed. Irradiation conditions, test procedures, and microstructural characteristics were carefully examined, and key factors that are important to determine the relevance of the database to PWR conditions were evaluated. Most swelling data were obtained from steels irradiated in fast breeder reactors at temperatures >385 C and at dose rates that are orders of magnitude higher than PWR dose rates. Even for a given irradiation temperature and given steel, the integral effects of dose and dose rate on void swelling should not be separated. It is incorrect to extrapolate swelling data on the basis of 'progressive compounded multiplication' of separate effects of factors such as dose, dose rate, temperature, steel composition, and fabrication procedure. Therefore, the fast reactor data should not be extrapolated to determine credible void swelling behavior for PWR end-of-life (EOL) or life-extension conditions. Although the void swelling data extracted from fast reactor studies is extensive and conclusive, only limited amounts of swelling data and information have been obtained on microstructural characteristics from discharged PWR internals or steels irradiated at temperatures and at dose rates comparable to those of a PWR. Based on this relatively small amount of information, swelling in thin-walled tubes and baffle bolts in a PWR is not considered a concern. As additional data and relevant research becomes available, the newer results should be integrated with existing data, and the worthiness of this conclusion should continue to be scrutinized. PWR baffle reentrant corners are the most likely location to experience high swelling rates, and

  10. Effect of defect imbalance on void swelling distributions produced in pure iron irradiated with 3.5 MeV self-ions

    NASA Astrophysics Data System (ADS)

    Shao, Lin; Wei, C.-C.; Gigax, J.; Aitkaliyeva, A.; Chen, D.; Sencer, B. H.; Garner, F. A.

    2014-10-01

    Ion irradiation has been widely used to simulate neutron-induced radiation damage. There are a number of features of ion-induced damage that differ from neutron-induced damage, however, and these differences require investigation before ion data can be confidently used to predict behavior arising from neutron bombardment. In this study 3.5 MeV self-ion irradiation of pure iron was used to study the influence on void swelling of the depth-dependent defect imbalance between vacancies and interstitials that arises from various surface effects, forward scattering of displaced atoms, and especially the injected interstitial effect. It was observed that the depth dependence of void swelling does not follow the behavior anticipated from the depth dependence of the damage rate. Void nucleation and growth develop first in the lower-dose, near-surface region, and then moves to progressively deeper and higher-damage depths during continued irradiation. This indicates a strong initial suppression of void nucleation in the peak damage region that is eventually overcome with continued irradiation. Using the Boltzmann transport equation method, this phenomenon is shown to be due to depth-dependent defect imbalances created under ion irradiation. These findings demonstrate that void swelling does not depend solely on the local dose level and that this sensitivity of swelling to depth must be considered in extraction and interpretation of ion-induced swelling data.

  11. Effect of defect imbalance on void swelling distributions produced in pure iron irradiated with 3.5 MeV self-ions

    DOE PAGESBeta

    Shao, Lin; Wei, C. -C.; Gigax, J.; Aitkaliyeva, A.; Chen, D.; Sencer, B. H.; Garner, F. A.

    2014-06-10

    Ion irradiation has been widely used to simulate radiation damage induced by neutrons. However, there are a number of features of ion-induced damage that differ from neutron-induced damage, and these differences require investigation before behavior arising from neutron bombardment can be confidently predicted from ion data. In this study 3.5 MeV self-ion irradiation of pure iron was used to study the influence on void swelling of the depth-dependent defect imbalance between vacancies and interstitials that arises from various surface effects, forward scattering of displaced atoms, and especially the injected interstitial effect. The depth dependence of void swelling was observed notmore » to follow the behavior anticipated from the depth dependence of the damage rate. Void nucleation and growth develop first in the lower-dose, near-surface region, and then, during continued irradiation, move to progressively deeper and higher-damage depths. This indicates a strong initial suppression of void nucleation in the peak damage region that continued irradiation eventually overcomes. This phenomenon is shown by the Boltzmann transport equation method to be due to depth-dependent defect imbalances created under ion irradiation. These findings thus demonstrate that void swelling does not depend solely on the local dose level and that this sensitivity of swelling to depth must be considered in extracting and interpreting ion-induced swelling data.« less

  12. Effect of defect imbalance on void swelling distributions produced in pure iron irradiated with 3.5 MeV self-ions

    SciTech Connect

    Shao, Lin; Wei, C. -C.; Gigax, J.; Aitkaliyeva, A.; Chen, D.; Sencer, B. H.; Garner, F. A.

    2014-06-10

    Ion irradiation has been widely used to simulate radiation damage induced by neutrons. However, there are a number of features of ion-induced damage that differ from neutron-induced damage, and these differences require investigation before behavior arising from neutron bombardment can be confidently predicted from ion data. In this study 3.5 MeV self-ion irradiation of pure iron was used to study the influence on void swelling of the depth-dependent defect imbalance between vacancies and interstitials that arises from various surface effects, forward scattering of displaced atoms, and especially the injected interstitial effect. The depth dependence of void swelling was observed not to follow the behavior anticipated from the depth dependence of the damage rate. Void nucleation and growth develop first in the lower-dose, near-surface region, and then, during continued irradiation, move to progressively deeper and higher-damage depths. This indicates a strong initial suppression of void nucleation in the peak damage region that continued irradiation eventually overcomes. This phenomenon is shown by the Boltzmann transport equation method to be due to depth-dependent defect imbalances created under ion irradiation. These findings thus demonstrate that void swelling does not depend solely on the local dose level and that this sensitivity of swelling to depth must be considered in extracting and interpreting ion-induced swelling data.

  13. Void swelling in high purity FeCrNi and FeCrNiTi alloys irradiated in JOYO

    NASA Astrophysics Data System (ADS)

    Muroga, T.; Araki, K.; Miyamoto, Y.; Yoshida, N.

    1988-07-01

    Microstructures have been observed in Fe-13Cr-14Ni and Fe-13Cr-14Ni-0.12Ti alloys irradiated in JOYO (Japanese Fast Experimental Reactor) at 400, 500 and 600 °C to the fluence of 0.079, 0.81 and 6.2 × 10 25n/ m2 ( E > 0.1 MeV). In the Fe-13Cr-14Ni alloy, voids are observed in all cases. The dose dependence of swelling seems to obey the kinetics of linear increase with or without initial short transient. On the other hand, remarkable swelling suppression effects are observed in the Fe-13Cr-14Ni-0.12Ti alloy. The detailed microstructural observation suggests the titanium addition effects suppress the void nucleation in the matrix by gettering impurities and obstructing dislocation climb by precipitate decoration on dislocation lines.

  14. Void swelling and precipitation in a titanium-modified austenitic stainless steel under proton irradiation

    NASA Astrophysics Data System (ADS)

    Kimoto, T.; Shiraishi, H.

    1985-07-01

    The correlation between void swelling and precipitation behavior in a 10% cold worked Fe-16.2Ni-14.6Cr-2.37Mo-1.79Mn-0.53Si-0.24Ti-0.06C alloy was examined with 200 keV proton irradiation. Swelling peak temperature after the proton irradiation to 10 dpa was about 823 K, and void swelling decreased steeply with increase in irradiation temperature from 823 to 923 K. Void swelling increased rapidly from 1.9 to 12.1% with increase in irradiation dose from 20 to 45 dpa at 873 K. Fine intragranular TiC precipitates, which were formed during initial stage of irradiation, dissolved gradually with increase in irradiation dose from 10 to 45 dpa at 873 K, while the amount of precipitation of needle-shaped Fe 2P phase containing titanium increased with increasing dose. The reduction of sink strength of the TiC precipitates due to the dissolution during irradiation was thought to cause the increase of swelling rate with increase in irradiation dose from 20 to 45 dpa at 873 K.

  15. Irradiation swelling behavior and its dependence on temperature, dose rate and dislocation structure evolution

    SciTech Connect

    Surh, M P; Sturgeon, J B; Wolfer, W G

    2004-01-16

    The microstructural evolution of high purity steel under irradiation is modeled including a dislocation density that evolves simultaneously with void nucleation and growth. The predicted void swelling trends versus temperature, flux, and time are compared to experiment and to earlier calculations with a fixed dislocation density. The behavior is further analyzed within a simplified picture of segregation of irradiation defects to microstructural sinks. Agreement with experimental swelling behavior improves when dislocations co-evolve with the void content versus simulations with a fixed dislocation density. The time-dependent dislocation content dictates the rate of void nucleation and shapes the overall void size distribution so as to give steady swelling behavior over long times.

  16. Observations of void swelling in selected austenitic alloys during ion irradiation under a rising temperature ramp

    NASA Astrophysics Data System (ADS)

    Mazey, D. J.; Williams, T. M.; Bolster, D. E. J.

    1988-07-01

    Results are given of a TEM study of the void swelling behaviour of CW AISI 321 (En58B), CW FV548 stainless steel and STA Nimonic PE16 alloy during 46 MeV nickel ion irradiation under a near-linear rising temperature ramp. The dose range for the ramp was 0-75 dpa and four temperature ranges were investigated using 50 ° C intervals from 500-550 ° C, 525-575 ° C, 575-625 ° C and 625-675 ° C. Swelling in CW 321 was found to be no greater than that observed after isothermal irradiation to 75 dpa at temperatures corresponding to the end-of-ramp temperatures. This was not the case for CW FV548 where the swelling for the temperature ranges of 525-575 ° C and 575-625 ° C was slightly greater than that observed under isothermal irradiation to 75 dpa. Swelling in STA PE16 in the lower temperature ranges of 500-550 ° C and 525-575°C was much higher than corresponding isothermal values but in the 600-700 ° C temperature range the swelling was close to isothermal values. The results on PE16 indicate that a steady increase in irradiation temperature from just below or just above the low temperature cut-off into the void swelling region produces a significant increase in swelling with respect to that expected under isothermal conditions. Possible interpretations of the observed swelling behaviour in these alloys are discussed.

  17. Effect of initial oxygen content on the void swelling behavior of fast neutron irradiated copper

    SciTech Connect

    Zinkle, S.J.; Garner, F.A.

    1998-03-01

    Density measurements were performed on high purity copper specimens containing {le}10 wt.ppm and {approximately}120 wt.ppm oxygen following irradiation in FFTF MOTA 2B. Significant amounts of swelling were observed in both the oxygen-free and oxygen-doped specimens following irradiation to {approximately}17 dpa at 375 C and {approximately}47 dpa at 430 C. Oxygen doping up to 360 appm (90 wt.ppm) did not significantly affect the void swelling of copper for these irradiation conditions.

  18. Void galaxy properties depending on void filament straightness

    NASA Astrophysics Data System (ADS)

    Shim, Junsup; Lee, Jounghun; Hoyle, Fiona

    2015-08-01

    We investigate the properties of galaxies belonging to the filaments in cosmic void regions, using the void catalogue constructed by Pan et al. (2012) from the SDSS DR7. To identify galaxy filaments within a void, voids with 30 or more galaxies are selected as a sample. We identify 3172 filaments in 1055 voids by applying the filament finding algorithm utilizing minimal spanning tree (MST) which is an unique linear pattern into which connects all the galaxies in a void. We study the correlations between galaxy properties and the specific size of filament which quantifies the degree of the filament straightness. For example, the average magnitude and the magnitude of the faintest galaxy in filament decrease as the straightness of the filament increases. We also find that the correlations become stronger in rich filaments with many member galaxies than in poor ones. We discuss a physical explanation to our findings and their cosmological implications.

  19. Lattice dependent motion of voids during electromigration

    SciTech Connect

    Sindermann, S. P.; Latz, A.; Dumpich, G.; Wolf, D. E.; Meyer zu Heringdorf, F.-J.

    2013-04-07

    The influence of the crystal lattice configuration to electromigration processes, e.g., void formation and propagation, is investigated in suitable test structures. They are fabricated out of self-assembled, bi-crystalline Ag islands, grown epitaxially on a clean Si(111) surface. The {mu}m-wide and approximately 100 nm thick Ag islands are a composition of a Ag(001) and a Ag(111) part. By focused ion beam milling, they are structured into wires with a single grain boundary, the orientation of which can be chosen arbitrarily. In-situ scanning electron microscopy (SEM) allows to capture an image sequence during electrical stressing and monitors the development of voids and hillocks in time. To visualize the position and motion of voids, we calculate void maps using a threshold algorithm. Most of the information from the SEM image sequence is compressed into one single image. Our present electromigration studies are based on in-situ SEM investigations for three different lattice configurations: Ag(001) (with electron current flow in [110] direction), Ag(111) (with electron current flow in [112] direction), and additionally 90 Ring-Operator rotated Ag(111) (with electron current flow in [110] direction). Our experimental results show that not only the formation and shape but also the motion direction of voids strongly depends on the crystal orientation.

  20. Modeling injected interstitial effects on void swelling in self-ion irradiation experiments

    NASA Astrophysics Data System (ADS)

    Short, M. P.; Gaston, D. R.; Jin, M.; Shao, L.; Garner, F. A.

    2016-04-01

    Heavy ion irradiations at high dose rates are often used to simulate slow and expensive neutron irradiation experiments. However, many differences in the resultant modes of damage arise due to unique aspects of heavy ion irradiation. One such difference was recently shown in pure iron to manifest itself as a double peak in void swelling, with both peaks located away from the region of highest displacement damage. In other cases involving a variety of ferritic alloys there is often only a single peak in swelling vs. depth that is located very near the ion-incident surface. We show that these behaviors arise due to a combination of two separate effects: 1) suppression of void swelling due to injected interstitials, and 2) preferential sinking of interstitials to the ion-incident surface, which are very sensitive to the irradiation temperature and displacement rate. Care should therefore be used in collection and interpretation of data from the depth range outside the Bragg peak of ion irradiation experiments, as it is shown to be more complex than previously envisioned.

  1. Prediction of void swelling in the baffle ring of WWER-1000 reactors for service life of 30-60 years

    NASA Astrophysics Data System (ADS)

    Kalchenko, A. S.; Bryk, V. V.; Lazarev, N. P.; Voyevodin, V. N.; Garner, F. A.

    2013-06-01

    Major internal components of WWER-type nuclear reactors are made from annealed 18Cr10NiTi steel, a close analog to AISI 321. Void swelling of the baffle ring in particular could be a major factor limiting operation of the reactor beyond the current 30 years license. A predictive swelling equation is needed to forecast the spatial variation of swelling so as to identify those areas requiring additional attention. Available data on the swelling of this steel arising from irradiation in the BOR-60 fast reactor was combined with data from a heavy ion accelerator at higher displacement rates to formulate a predictive equation of swelling for the WWER-relevant range of temperature, irradiation dose and dose rates. This equation was used to estimate the swelling distribution over a cross-section of the baffle ring of a WWER reactor during a service life up to 60 years, reaching a local maximum of ˜30% swelling. It was shown that void swelling extends over a larger portion of the baffle ring than previously expected and exhibits a very complex and irregular distribution in response to complex distributions of temperature and dpa rate. Most importantly, as operation is extended beyond 30 years several areas of the ring may experience swelling in excess of 10% where void-induced embrittlement begins and one area may exceed 20% after 45 years, a swelling level where a complete loss of ductility is known to occur.

  2. Void Swelling and Microstructure of Austenitic Stainless Steels Irradiated in the BOR - 60 Reactor

    SciTech Connect

    Chen, Y.; Yang, Yong; Huang, Yina; Allen, T.; Alexandreanu, B.; Natesan, K.

    2012-11-01

    As nuclear power plants age and neutron fluence increases, detrimental effects resulting from radiation damage have become an increasingly important issue for the operational safety and structural integrity of core internal components. In this study, irradiated specimens of reactor core internal components were characterized by transmission electron microscopy. The specimens had been irradiated to 5.5-45 dpa in the BOR-60 reactor at a dose rate close to 10-6 dpa/s and temperature of about 320°C. No voids were observed in the austenitic stainless steels and nickel alloys at all doses. Despite the possibility that fine voids below the TEM resolution limit may be present, it was clear that void swelling was insignificant in all examined alloys up to 45 dpa. Irradiated microstructures of the studied alloys were dominated by a high density of Frank loops. The mean size and density of the Frank loops varied from one material to another, but saturated with increasing dose above ~10 dpa. While no irradiation-induced precipitations were present below 24.5 dpa, fine precipitates were evident in several alloys at 45 dpa.

  3. Void swelling and microstructure evolution at very high damage level in self-ion irradiated ferritic-martensitic steels

    NASA Astrophysics Data System (ADS)

    Getto, E.; Sun, K.; Monterrosa, A. M.; Jiao, Z.; Hackett, M. J.; Was, G. S.

    2016-11-01

    The void swelling and microstructure evolution of ferritic-martensitic alloys HT9, T91 and T92 were characterized following irradiation with Fe++ ions at 460 °C to damage levels of 75-650 displacements per atom with 10 atom parts per million pre-implanted helium. Steady state swelling rate of 0.033%/ dpa was determined for HT9, the least swelling resistant alloy, and 0.007%/ dpa in T91. In T91, resistance was due to suppression of void nucleation. Swelling resistance was greatest in T92, with a low density (∼1 × 1020 m-3) of small voids that had not grown appreciably, indicating suppression of nucleation and growth. Additional heats of T91 indicated that alloy composition was not the determining factor of swelling resistance. Carbon and chromium-rich M2X precipitates formed at 250 dpa and were correlated with decreased nucleation in T91 and T92, but did not affect void growth in HT9. Dislocation and G-phase microstructure evolution was analyzed up to 650 dpa in HT9.

  4. Void swelling of an oxide dispersion strengthened ferritic alloy in a high voltage electron microscope

    NASA Astrophysics Data System (ADS)

    Snykers, M.

    1980-03-01

    An oxide dispersion strengthened ferritic alloy with nominal composition Fe-13Cr-3.5Ti-1.5Mo-2TiO 2 and a cast alloy with a composition close to that of the matrix of the oxide dispersion strengthened alloy are irradiated in a high voltage electron microscope in the temperature range 380-550°C. The alloys are doped with 0-30 ppm helium. For alloys containing 10 ppm He a peak swelling temperature at 450°C is found. A maximum swelling of 1.1% is found at an irradiation dose of 20 dpa. In the absence of He no swelling is found in the temperature range 430-470°C. The swelling rate is highest at the onset of swelling. The results obtained here are quite similar to those for some ferritic steels such as FV607, EM 12 and HT9, except for the influence of He and for the dose dependence.

  5. Effect of pre-implanted helium on void swelling evolution in self-ion irradiated HT9

    NASA Astrophysics Data System (ADS)

    Getto, E.; Jiao, Z.; Monterrosa, A. M.; Sun, K.; Was, G. S.

    2015-07-01

    Void evolution in Fe++-irradiated ferritic-martensitic alloy HT9 was characterized in the temperature range of 400-480 °C between doses of 25 and 375 displacements per atom (dpa) with pre-implanted helium levels of 0-100 appm. A systematic study using depth profiling in cross-section samples was conducted to determine a valid region of analysis between 300 and 700 nm from the surface, which excluded effects due to the injected interstitial and the surface. Pre-implanted helium was found to promote void swelling at low doses by shortening the nucleation regime and to retard void growth at doses in the transient regime by enhancement of nucleation of small voids. Swelling was found to peak at a temperature of 460 °C. The primary effect of temperature was on the nucleation regime; nucleation regime was the shortest at 460 °C compared to that at 440 and 480 °C. The growth rate of voids was temperature-invariant. Steady state swelling was reached at 460 °C between 188 and 375 dpa at a rate of 0.02%/dpa.

  6. Determination of the Lower Temperature Limit of Void Swelling of Stainless Steels at Relatively Low Displacement Rates

    SciTech Connect

    Porollo, S. I.; Konobeev, Yu V.; Dvoriashin, Alexander M.; Krigan, V. M.; Garner, Francis A.

    2002-03-31

    An issue of current interest to PWRs is the possibility that void swelling of austenitic near-core internal components may exert some deleterious effect on component functionality, particularly during extended operation to 60 years. A similar concern has also been raised for water-cooled fusion devices. One question of particular interest is the range of temperature over which void swelling can occur, since the internal components experience temperatures from ~290 to perhaps as high as 390 degrees C in some limited locations. This question was addressed using a flow restrictor component from the low-flux breeder zone of the BN-350 fast reactor in Kazakhstan. This component was constructed of annealed 12X18H10T, an alloy similar to AISI 321 which is used in Russian reactors for applications where AISI 304L would be used in comparable Western and Japanese reactors. Extensive sectioning to produce 114 separate specimens, followed by examination of the radiation-induced microstructure showed that void swelling in the range of temperatures and dpa rates of PWR interest occurs down to ~305 degrees C. At 330 degrees C the swelling reached ~1% at 20 dpa. Comparison of these data with other published results from Russian LWR reactors at <10 dpa confirms that the lowest temperature that stainless steels can begin swelling appears to be ~300 degrees C. Since fusion and PWR spectra generate similar levels of hydrogen and helium, it is expected that these conclusions are also application to fusion devices operating at comparable dpa rates.

  7. The effects of silicon and titanium on void swelling and phase transformations in neutron irradiated 12Cr-15Ni steels

    NASA Astrophysics Data System (ADS)

    Boothby, R. M.; Williams, T. M.

    1988-05-01

    12Cr-15Ni-0.25Ti steels with Si additions of 0.5, 0.9 and 1.4 wt% have been irradiated to a maximum dose of 47 dpa at temperatures ranging from 399 to 649°C. Detailed microstructural examinations of void swelling, precipitation behaviour and austenite instability have been made. Assessments of swelling and matrix phase transformations have also been made using density and induced magnetization measurements respectively. Austenite instability was increased by Si additions; the transformation product was usually ferrite although some martensite was also observed, and compositional fluctuations in untransformed austenite were detected. Precipitation, particularly of G phase, became more extensive and swelling in solution-treated alloys was reduced at higher Si contents. Enhanced growth of voids attached to G phase precipitates was observed. Cold-working decreased both swelling and ferrite formation. A fine dispersion of TiC was effective in suppressing swelling at high irradiation temperature as long as the precipitates remained stable. The stability of TiC was increased by cold-working but reduced by Si additions.

  8. Determination of the Lower Temperature Limit of Void Swelling of Stainless Steels at PWR-Relevant Displacement Rates

    SciTech Connect

    Porollo, S. I.; Konobeev, Yury V.; Dvoriashin, Alexander M.; Krigan, V. M.; Garner, Francis A.

    2004-01-01

    Recent studies associated with light water reactors (LWR) in both the USA and Russia have raised the question of void swelling in austenitic components of core internals. One question of particular interest is the range of temperatures over which voids can develop, especially the lowest temperature. To address this question a flow restrictor component manufactured from annealed X18H9T was removed from the reflector region of the BN-350 fast reactor, located in Kazakhstan. During operation this component spanned temperatures and dpa rates of direct interest to pressurized water reactors (PWRs) in the West and VVERs in Russia. This steel is analogous to AISI 321 and is used in Russian reactors for applications where AISI 304 would be used in the West and in Japan. This component was sectioned on a very fine scale to determine in what range of conditions voids existed. Microstructural data were obtained for 157 separate locations, with 111 specimens showing voids over the relevant range of temperatures and displacement rates, allowing construction of a parametric map of swelling with temperature, dpa and dpa rate. These data show that swelling at doses as high as ~50 dpa persists down to ~306°C for dose rates in the range 0.11 x 10-7 to 1.6 x 10-7dpa/sec. Finally, since the helium generation rate is rather low in the spectral environment of the flow restrictor, the early onset of swelling is attributed primarily to the lower displacement rate, a conclusion supported by a number of other experimental studies.

  9. Void Swelling Of Aisi 321 Analog Stainless Steel Irradiated At Low Dpa Rates In The Bn-350 Reactor

    SciTech Connect

    Maksimkin, O. P.; Tsai, K. V.; Turubarova, L. G.; Doronina, T. A.; Garner, Francis A.

    2006-03-01

    In several recently published studies conducted on a Soviet analog of AISI 321 stainless steel irradiated in either fast reactors or light water reactors, it was shown that the void swelling phenomenon extended to temperatures as low as ~300ºC or less, when produced by neutron irradiation at dpa rates in the range 10-7 to 10-8 dpa/sec. Other studies yielded similar results for AISI 316 and the Russian analog of AISI 316. In the current study a blanket duct assembly from BN-350, constructed from the Soviet analog of AISI 321, also exhibits swelling at dpa rates on the order of 10-8 dpa/sec, with voids seen as low as 281oC and only 0.65 dpa. It appears that low-temperature swelling occurs at low dpa rates in 300 series stainless steels in general, and also occurs during irradiations conducted in either fast or mixed spectrum reactors. Therefore it is expected that a similar behavior will be observed in fusion devices as well.

  10. Void Swelling of AISI 321 Analog Stainless Steel Irradiated at Low DPA Rates in the BN-350 Reactor

    SciTech Connect

    Maksimkin, O. P.; Tsai, K. V.; Turubarova, L. G.; Doronina, T. A.; Garner, Francis A.

    2007-08-01

    In several recently published studies conducted on a Soviet analog of AISI 321 stainless steel irradiated in either fast reactors or light water reactors, it was shown that the void swelling phenomenon extended to temperatures as low as ~300ºC or less, when produced by neutron irradiation at dpa rates in the range 10-7 to 10-8 dpa/sec. Other studies yielded similar results for AISI 316 and the Russian analog of AISI 316. In the current study a blanket duct assembly from BN-350, constructed from the Soviet analog of AISI 321, also exhibits swelling at dpa rates on the order of 10-8 dpa/sec, with voids seen as low as 281C and only 0.65 dpa. It appears that low-temperature swelling occurs at low dpa rates in 300 series stainless steels in general, and also occurs during irradiations conducted in either fast or in mixed spectrum reactors as shown in other studies.

  11. Void swelling of AISI 321 analog stainless steel irradiated at low dpa rates in the BN-350 reactor

    NASA Astrophysics Data System (ADS)

    Maksimkin, O. P.; Tsai, K. V.; Turubarova, L. G.; Doronina, T.; Garner, F. A.

    2007-08-01

    In several recently published studies conducted on a Soviet analog of AISI 321 stainless steel irradiated in either fast reactors or light water reactors, it was shown that the void swelling phenomenon extended to temperatures as low as ˜300 °C or less, when produced by neutron irradiation at dpa rates in the range 10 -7-10 -8 dpa/s. Other studies yielded similar results for AISI 316 and the Russian analog of AISI 316. In the current study a blanket assembly duct from BN-350, constructed from the Soviet analog of AISI 321, also exhibits swelling at dpa rates on the order of 10 -8 dpa/s, with voids seen as low as 281 °C and only 0.65 dpa. It appears that low-temperature swelling occurs at low dpa rates in 300 series stainless steels in general, and also occurs during irradiations conducted in either fast or in mixed spectrum reactors as shown in other studies.

  12. Multi-hollow polymer microspheres with enclosed surfaces and compartmentalized voids prepared by seeded swelling polymerization method.

    PubMed

    Tian, Qiong; Yu, Demei; Zhu, Kaiming; Hu, Guohe; Zhang, Lifeng; Liu, Yuhang

    2016-07-01

    Multi-hollow particles have drawn extensive research interest due to their high specific areas and abundant inner voids, whereas their convenient synthesis still remains challenging. In this paper, we report a simple and convenient method based on seeded swelling polymerization to prepare the multi-hollow microspheres with enclosed surfaces and compartmentalized voids using monodisperse poly (styrene-co-sodium 4-vinylbenzenesulfonate) microspheres as seed particles. A formation mechanism of the multi-hollow structure was proposed involving the processes of water absorption, coalescence and stabilization of water domains, immobilization of multi-hollow structure, and coverage of surface dimples. The influencing parameters on the morphology of the microspheres, including weight ratio of sodium 4-vinylbenzenesulfonate to styrene in the seed particles, dosage of the swelling monomer and the crosslinking agent were systematically investigated. The internal structure of the resultant microspheres could be tuned from solid to multi-hollow by controlling over these parameters. Multi-hollow microspheres with compartmentalized chambers, smooth surfaces and narrow size distributions were obtained as a result.

  13. Multi-hollow polymer microspheres with enclosed surfaces and compartmentalized voids prepared by seeded swelling polymerization method.

    PubMed

    Tian, Qiong; Yu, Demei; Zhu, Kaiming; Hu, Guohe; Zhang, Lifeng; Liu, Yuhang

    2016-07-01

    Multi-hollow particles have drawn extensive research interest due to their high specific areas and abundant inner voids, whereas their convenient synthesis still remains challenging. In this paper, we report a simple and convenient method based on seeded swelling polymerization to prepare the multi-hollow microspheres with enclosed surfaces and compartmentalized voids using monodisperse poly (styrene-co-sodium 4-vinylbenzenesulfonate) microspheres as seed particles. A formation mechanism of the multi-hollow structure was proposed involving the processes of water absorption, coalescence and stabilization of water domains, immobilization of multi-hollow structure, and coverage of surface dimples. The influencing parameters on the morphology of the microspheres, including weight ratio of sodium 4-vinylbenzenesulfonate to styrene in the seed particles, dosage of the swelling monomer and the crosslinking agent were systematically investigated. The internal structure of the resultant microspheres could be tuned from solid to multi-hollow by controlling over these parameters. Multi-hollow microspheres with compartmentalized chambers, smooth surfaces and narrow size distributions were obtained as a result. PMID:27046772

  14. Swelling

    MedlinePlus

    ... syndrome Poor nutrition Pregnancy Thyroid disease Too little albumin in the blood (hypoalbuminemia) Too much salt or ... the swelling. Tests that may be done include: Albumin blood test Blood electrolyte levels Echocardiography ECG Kidney ...

  15. Ion irradiation studies on the void swelling behavior of a titanium modified D9 alloy

    NASA Astrophysics Data System (ADS)

    Balaji, S.; Mohan, Sruthi; Amirthapandian, S.; Chinnathambi, S.; David, C.; Panigrahi, B. K.

    2015-12-01

    The sensitivity of Positron Annihilation Spectroscopy (PAS) for probing vacancy defects and their environment is well known. Its applicability in determination of swelling and the peak swelling temperature was put to test in our earlier work on ion irradiated D9 alloys [1]. Upon comparison with the peak swelling temperature determined by conventional step height measurements it was found that the peak swelling temperature determined using PAS was 50 K higher. It was conjectured that the positrons trapping in the irradiation induced TiC precipitation could have caused the shift. In the present work, D9 alloys have been implanted with 100 appm helium ions and subsequently implanted with 2.5 MeV Ni ions up to peak damage of 100 dpa. The nickel implantations have been carried out through a range of temperatures between 450 °C and 650 °C. The evolution of cavities and TiC precipitates at various temperatures has been followed by TEM and this report provides an experimental verification of the conjecture.

  16. Irradiation creep and void swelling of two LMR heat of HT9 at {approx}400{degrees}C and 165 dpa

    SciTech Connect

    Toloczko, M.B.; Garner, F.A.

    1996-04-01

    Two nominally identical heats of HT9 ferritic-martensitic steel were produced, fabricated into pressurized tubes, and then irradiated in FFTF, using identical procedures. After reaching 165 dpa at {approx}400C, small differences in strains associated with both phase-related change in lattice parameter and void swelling were observed in comparing the two heats. The creep strains, while different, exhibited the same functional relationship to the swelling behavior. The derived creep coefficients, the one associated with creep in the absence of swelling and the one directly responsive to swelling, were essentially identical for the two heats. Even more significantly, the creep coefficients for this bcc ferritic-martensitic steel appear to be very similar and possibly identical to those routinely derived from creep experiments on fcc austenitic steels.

  17. Void Swelling at Low Displacement Rates in Annealed X18H10T Stainless Steel at 4 to 56 DPA and 280-332 degrees centigrade

    SciTech Connect

    Garner, Francis A.; Porollo, S. I.; Vorobjev, A. N.; Konobeev, Yu V.; Dvoriashin, A. M.

    2001-10-01

    Various components of pressurized water power reactors (PWRs) and some proposed fusion devices such as ITER will operate at lower temperatures and displacement rates than are encountered in many test reactors such as EBR-II, FFTF and HFIR. The question arises if the presence and magnitude of void swelling can be predicted for such irradiation environments. Data on Russian steel can be used to address part of this question. In reactor applications where Western countries typically use annealed AISI 304 stainless steel, it is the Russian practice to use annealed X18H10T, a titanium-stabilized 18Cr-10Ni stainless steel analogous to AISI 321. Using a flow restrictor component from the low-flux breeder zone of the BN-350 reactor in Kazakhstan, it was possible to examine the behavior of void swelling at relatively low temperatures and low displacement rates after 12 years of irradiation. The temperature of this component ranged from 270-340 degrees centigrade with a peak dose rate of 1.6 x 10{sup -7} power dpa/sec and a peak dose of 56 dpa. Careful sectioning of the component has yielded a large number of microscopy specimens over a ITER-relevant range of temperatures and displacement rates. Microstructural data are presented and show that void swelling at 10 to 50 dpa persists down to {approx}306 degrees centigrade for dose rates on the order of 1 x 10{sup -7} power dpa/sec.

  18. Void swelling at low displacement rates in annealed 12X18HgT stainless steel at 4-56 dpa and 280-332 °C

    NASA Astrophysics Data System (ADS)

    Porollo, S. I.; Konobeev, Yu. V.; Dvoriashin, A. M.; Vorobjev, A. N.; Krigan, V. M.; Garner, F. A.

    2002-12-01

    Water-cooled fusion devices most likely will have austenitic components that operate at temperatures below the inlet temperatures characteristic of high flux fast reactors used to generate majority of data on void swelling. Many of these components will experience displacement rates of 10 -7-10 -8 dpa/s that are lower than that of most in-core fast reactor experiments. One question of particular interest is how to define the lower limit of the temperature range over which void swelling can occur at such low dpa rates. This question was addressed using a flow restrictor component irradiated at 4-56 dpa and 280-332 °C in the low-flux breeder zone of the BN-350 fast reactor in Kazakhstan. This component was constructed of annealed 12X18HgT, an alloy similar to AISI 321. Extensive sectioning to produce 114 separate specimens, followed by examination of the radiation-induced microstructure showed that void swelling in the range of temperatures and dpa rates of interest occurs down to ˜300 °C.

  19. Void Swelling at Low Displacement Rates in Annealed 12X18H9T Stainless Steel at 4 to 56 dpa and 280-332 degrees C

    SciTech Connect

    Porollo, S. I.; Konobeev, Yu V.; Dvoraishin, A. M.; Vorobjev, A. N.; Krigan, V M.; Garner, Francis A.

    2002-12-01

    Water-cooled fusion devices most likely will have austenitic components that operate at temperatures below the inlet temperatures characteristic of high flux fast reactors used to generate majority of data on void swelling. Many of these same locations will also experience displacement rates that are also lower than that of most in-core fast reactor experiments, 10-7 to 10-8 dpa/s. One question of particular interest is how to define the lower limit of the temperature range over which void swelling can occur, especially at such lower dpa rates. This question was addressed using a flow restrictor component from the low-flux breeder zone of the BN-350 fast reactor in Kazakhstan. This component was constructed of annealed 12X18H10T, an alloy similar to AISI 321. Extensive sectioning to produce 114 separate specimens, followed by examination of the radiation-induced microstructure showed that void swelling in the range of temperatures and dpa rates of interest occurs down to approximately 300 degrees C. At 330 degrees C the swelling reached approximately 1 percent at 20 dpa. Comparison of these data with other published data on this steel from Russian light water reactors at less than 10 dpa confirms that the lowest temperature that stainless steels can begin swelling also appears to be approximately 300 degrees C. Since fusion and LWR spectra generate similar levels of hydrogen and helium, it is expected that these conclusions are equally applicable to both types of reactors when operating at comparable dpa rates.

  20. The influence of fabrication procedure on the void swelling of an oxide dispersion strengthened ferritic alloy in a HVEM

    NASA Astrophysics Data System (ADS)

    Snykers, M.; Biermans, F.; Cornelis, J.

    The influence of changes in the fabrication procedure of ferritic alloys with compositions Fe-13Cr-Ti-Mo-TiO 2 on the swelling behaviour are investigated. The fabrication procedures are: casting, powder metallurgy 3- milling in air and powder metallurgy 3- milling in argon. No difference is found for the results obtained for the materials fabricated by casting and by powder metallurgy 3- milling in air. Slightly different results are obtained for the material fabricated by powder metallurgy 3- milling in argon. This material contains argon in solution in the matrix, which causes a small shift of the peak swelling temperature and of the peak swelling helium concentration for tests carried out at 450°C. The overall swelling of this material is the lowest due to the small grain size and to the high density of inclusions.

  1. Rate dependence of swelling in lithium-ion cells

    SciTech Connect

    Oh, KY; Siegel, JB; Secondo, L; Kim, SU; Samad, NA; Qin, JW; Anderson, D; Garikipati, K; Knobloch, A; Epureanu, BI; Monroe, CW; Stefanopoulou, A

    2014-12-01

    Swelling of a commercial 5 Ah lithium-ion cell with a nickel/manganese/cobalt-oxide cathode is investigated as a function of the charge state and the charge/discharge rate. In combination with sensitive displacement measurements, knowledge of the electrode configuration within this prismatic cell's interior allows macroscopic deformations of the casing to be correlated to electrochemical and mechanical transformations in individual anode/separator/cathode layers. Thermal expansion and interior charge state are both found to cause significant swelling. At low rates, where thermal expansion is negligible, the electrode sandwich dilates by as much as 1.5% as the charge state swings from 0% to 100% because of lithium-ion intercalation. At high rates a comparably large residual swelling was observed at the end of discharge. Thermal expansion caused by joule heating at high discharge rate results in battery swelling. The changes in displacement with respect to capacity at low rate correlate well with the potential changes known to accompany phase transitions in the electrode materials. Although the potential response changes minimally with the C-rate, the extent of swelling varies significantly, suggesting that measurements of swelling may provide a sensitive gauge for characterizing dynamic operating states. (C) 2014 Elsevier B.V. All rights reserved.

  2. The correlation between swelling and radiation-induced segregation in iron-chromium-nickel alloys.

    SciTech Connect

    Allen, T. R.; Busby, J. T.; Kenik, E. A.; Was, G. S.

    1998-03-05

    The magnitudes of both void swelling and radiation-induced segregation (RIS) in iron-chromium-nickel alloys are dependent on bulk alloy composition. Because the diffusivity of nickel via the vacancy flux is slow relative to chromium, nickel enriches and chromium depletes at void surfaces during irradiation. This local composition change reduces the subsequent vacancy flux to the void, thereby reducing void swelling. In this work, the resistance to swelling from major element segregation is estimated using diffusivities derived from grain boundary segregation measurements in irradiated iron-chromium-nickel alloys. The resistance to void swelling in iron- and nickel-base alloys correlates with the segregation and both are functions of bulk alloy composition. Alloys that display the greatest amount of nickel enrichment and chromium depletion are found to be most resistant to void swelling, as predicted. Additionally, swelling is shown to be greater in alloys in which the RIS profiles are slow to develop.

  3. Fractal study of pion void probability distribution in ultrarelativistic nuclear collision and its target dependence

    NASA Astrophysics Data System (ADS)

    Bhaduri, Susmita; Ghosh, Dipak

    2016-08-01

    There are numerous existing works on investigating the dynamics of particle production process in ultrarelativistic nuclear collision. In the past, fluctuation of spatial pattern has been analyzed in terms of the scaling behavior of voids. But analysis of the scaling behavior of the void in fractal scenario has not been explored yet. In this work, we have analyzed the fractality of void probability distribution with a completely different and rigorous method called visibility graph analysis, analyzing the void-data produced out of fluctuation of pions in 32S-AgBr interaction at 200 GeV in pseudo-rapidity (η) and azimuthal angle (ϕ) space. The power of scale-freeness of visibility graph denoted by PSVG is a measure of fractality, which can be used as a quantitative parameter for the assessment of the state of chaotic system. As the behavior of particle production process depends on the target excitation, we can dwell down the void probability distribution in the event-wise fluctuation resulted out of the high energy interaction for different degree of target excitation, with respect to the fractal scenario and analyze the scaling behavior of the voids. From the analysis of the PSVG parameter, we have observed that scaling behavior of void probability distribution in multipion production changes with increasing target excitation. Since visibility graph method is a classic method of complex network analysis, has been applied over fractional Brownian motion (fBm) and fractional Gaussian noises (fGn) to measure the fractality and long-range dependence of a time series successfully, we can quantitatively confirm that fractal behavior of the void probability distribution in particle production process depends on the target excitation.

  4. Constitutive modeling of rate dependence and microinertia effects in porous-plastic materials with multi-sized voids (MSVs)

    NASA Astrophysics Data System (ADS)

    Liu, J. X.; El Sayed, T.

    2013-01-01

    Micro-voids of varying sizes exist in most metals and alloys. Both experiments and numerical studies have demonstrated the critical influence of initial void sizes on void growth. The classical Gurson-Tvergaard-Needleman model summarizes the influence of voids with a single parameter, namely the void-volume fraction, excluding any possible effects of the void-size distribution. We extend our newly proposed model including the multi-sized void (MSV) effect and the void-interaction effect for the capability of working for both moderate and high loading rate cases, where either rate dependence or microinertia becomes considerable or even dominant. Parametric studies show that the MSV-related competitive mechanism among void growth leads to the dependence of the void growth rate on void size, which directly influences the void's contribution to the total energy composition. We finally show that the stress-strain constitutive behavior is also affected by this MSV-related competitive mechanism. The stabilizing effect due to rate sensitivity and microinertia is emphasized.

  5. Use of double and triple-ion irradiation to study the influence of high levels of helium and hydrogen on void swelling of 8-12% Cr ferritic-martensitic steels

    NASA Astrophysics Data System (ADS)

    Kupriiyanova, Y. E.; Bryk, V. V.; Borodin, O. V.; Kalchenko, A. S.; Voyevodin, V. N.; Tolstolutskaya, G. D.; Garner, F. A.

    2016-01-01

    In accelerator-driven spallation (ADS) devices, some of the structural materials will be exposed to intense fluxes of very high energy protons and neutrons, producing not only displacement damage, but very high levels of helium and hydrogen. Unlike fission flux-spectra where most helium and hydrogen are generated by transmutation in nickel and only secondarily in iron or chromium, gas production in ADS flux-spectra are rather insensitive to alloy composition, such that Fe-Cr base ferritic alloys also generate very large gas levels. While ferritic alloys are known to swell less than austenitic alloys in fission spectra, there is a concern that high gas levels in fusion and especially ADS facilities may strongly accelerate void swelling in ferritic alloys. In this study of void swelling in response to helium and hydrogen generation, irradiation was conducted on three ferritic-martensitic steels using the Electrostatic Accelerator with External Injector (ESUVI) facility that can easily produce any combination of helium to dpa and/or hydrogen to dpa ratios. Irradiation was conducted under single, dual and triple beam modes using 1.8 MeV Cr+3, 40 keV He+, and 20 keV H+. In the first part of this study we investigated the response of dual-phase EP-450 to variations in He/dpa and H/dpa ratio, focusing first on dual ion studies and then triple ion studies, showing that there is a diminishing influence on swelling with increasing total gas content. In the second part we investigated the relative response of three alloys spanning a range of starting microstructure and composition. In addition to observing various synergisms between He and H, the most important conclusion was that the tempered martensite phase, known to lag behind the ferrite phase in swelling in the absence of gases, loses much of its resistance to void nucleation when irradiated at large gas/dpa levels.

  6. Void lattice formation as a nonequilibrium phase transition

    SciTech Connect

    Semenov, A. A.; Woo, C. H.

    2006-07-01

    The evolution of a void ensemble in the presence of one-dimensionally migrating self-interstitials is considered, consistently taking into account the nucleation of voids via the stochastic accumulation of vacancies. Including the stochastic fluctuations of the fluxes of mobile defects caused by the random nature of diffusion jumps and cascade initiation, the evolution of the void ensemble is treated using the Fokker-Planck equation approach. A system instability signaling a nonequilibrium phase transition is found to occur when the mean free path of the one-dimensionally moving self-interstitials becomes comparable with the average distance between the voids at a sufficiently high void-number density. Due to the exponential dependence of the void nucleation probability on the net vacancy flux, the nucleation of voids is much more favored at the void lattice positions. Simultaneously, voids initially nucleated at positions where neighboring voids are nonaligned will also shrink away. These two processes leave the aligned voids to form a regular lattice. The shrinkage of nonaligned voids is not a usual thermodynamic effect, but is a kinetic effect caused entirely by the stochastic fluctuations in point-defect fluxes received by the voids. It is shown that the shrinkage of the nonaligned voids, and thus the formation of the void lattice, occurs only if the effective fraction of one-dimensional interstitials is small, less than about 1%. The formation of the void lattice in this way can be accomplished at a void swelling of below 1%, in agreement with experimental observation. The dominance of void nucleation at void-lattice positions practically nullifies the effect of void coalescence induced by the one-dimensional self-interstitial transport.

  7. Effect of grain morphology on gas bubble swelling in UMo fuels - A 3D microstructure dependent Booth model

    NASA Astrophysics Data System (ADS)

    Hu, Shenyang; Burkes, Douglas; Lavender, Curt A.; Joshi, Vineet

    2016-11-01

    A three dimensional microstructure dependent swelling model is developed for studying the fission gas swelling kinetics in irradiated nuclear fuels. The model is extended from the Booth model [1] in order to investigate the effect of heterogeneous microstructures on gas bubble swelling kinetics. As an application of the model, the effect of grain morphology, fission gas diffusivity, and spatially dependent fission rate on swelling kinetics are simulated in UMo fuels. It is found that the decrease of grain size, the increase of grain aspect ratio for the grain having the same volume, and the increase of fission gas diffusivity (fission rate) cause the increase of swelling kinetics. Other heterogeneities such as second phases and spatially dependent thermodynamic properties including diffusivity of fission gas, sink and source strength of defects could be naturally integrated into the model to enhance the model capability.

  8. Cell swelling-induced ATP release is tightly dependent on intracellular calcium elevations

    PubMed Central

    Boudreault, Francis; Grygorczyk, Ryszard

    2004-01-01

    Mechanical stresses release ATP from a variety of cells by a poorly defined mechanism(s). Using custom-designed flow-through chambers, we investigated the kinetics of cell swelling-induced ATP secretion, cell volume and intracellular calcium changes in epithelial A549 and 16HBE14o− cells, and NIH/3T3 fibroblasts. Fifty per cent hypotonic shock triggered transient ATP release from cell confluent monolayers, which consistently peaked at around 1 min 45 s for A549 and NIH/3T3, and at 3 min for 16HBE14o− cells, then declined to baseline within the next 15 min. Whereas the release time course had a similar pattern for the three cell types, the peak rates differed significantly (294 ± 67, 70 ± 22 and 17 ± 2.8 pmol min−1 (106 cells)−1, for A549, 16HBE14o− and NIH/3T3, respectively). The concomitant volume changes of substrate-attached cells were analysed by a 3-dimensional cell shape reconstruction method based on images acquired from two perpendicular directions. The three cell types swelled at a similar rate, reaching maximal expansion in 1 min 45 s, but differed in the duration of the volume plateau and regulatory volume decrease (RVD). These experiments revealed that ATP release does not correlate with either cell volume expansion and the expected activation of stretch-sensitive channels, or with the activation of volume-sensitive, 5-nitro-2-(3-phenylpropylamino) benzoic acid-inhibitable anion channels during RVD. By contrast, ATP release was tightly synchronized, in all three cell types, with cytosolic calcium elevations. Furthermore, loading A549 cells with the calcium chelator BAPTA significantly diminished ATP release (71% inhibition of the peak rate), while the calcium ionophore ionomycin triggered ATP release in the absence of cell swelling. Lowering the temperature to 10°C almost completely abolished A549 cell swelling-induced ATP release (95% inhibition of the peak rate). These results strongly suggest that calcium-dependent exocytosis plays a

  9. Joint swelling

    MedlinePlus

    Swelling of a joint ... Joint swelling may occur along with joint pain . The swelling may cause the joint to appear larger or abnormally shaped. Joint swelling can cause pain or stiffness. After an ...

  10. Void Dynamics

    NASA Astrophysics Data System (ADS)

    Padilla, Nelson D.; Paz, Dante; Lares, Marcelo; Ceccarelli, Laura; Lambas, Diego Garcí A.; Cai, Yan-Chuan; Li, Baojiu

    2016-10-01

    Cosmic voids are becoming key players in testing the physics of our Universe.Here we concentrate on the abundances and the dynamics of voids as these are among the best candidatesto provide information on cosmological parameters. Cai, Padilla & Li (2014)use the abundance of voids to tell apart Hu & Sawicki f(R) models from General Relativity. An interestingresult is that even though, as expected, voids in the dark matter field are emptier in f(R) gravity due to the fifth force expellingaway from the void centres, this result is reversed when haloes are used to find voids. The abundance of voids in this casebecomes even lower in f(R) compared to GR for large voids. Still, the differences are significant and thisprovides a way to tell apart these models. The velocity field differences between f(R) and GR, on the other hand, arethe same for halo voids and for dark matter voids.Paz et al. (2013), concentrate on the velocity profiles around voids. First they show the necessityof four parameters to describe the density profiles around voids given two distinct voidpopulations, voids-in-voids and voids-in-clouds. This profile is used to predict peculiar velocities around voids,and the combination of the latter with void density profiles allows the construction of modelvoid-galaxy cross-correlation functions with redshift space distortions. When these modelsare tuned to fit the measured correlation functions for voids and galaxies in the SloanDigital Sky Survey, small voids are found to be of the void-in-cloud type, whereas largerones are consistent with being void-in-void. This is a novel result that is obtaineddirectly from redshift space data around voids. These profiles can be used toremove systematics on void-galaxy Alcock-Pacinsky tests coming from redshift-space distortions.

  11. Orientation-dependent interfacial mobility governs the anisotropic swelling in lithiated silicon nanowires.

    PubMed

    Yang, Hui; Huang, Shan; Huang, Xu; Fan, Feifei; Liang, Wentao; Liu, Xiao Hua; Chen, Long-Qing; Huang, Jian Yu; Li, Ju; Zhu, Ting; Zhang, Sulin

    2012-04-11

    Recent independent experiments demonstrated that the lithiation-induced volume expansion in silicon nanowires, nanopillars, and microslabs is highly anisotropic, with predominant expansion along the <110> direction but negligibly small expansion along the <111> direction. The origin of such anisotropic behavior remains elusive. Here, we develop a chemomechanical model to study the phase evolution and morphological changes in lithiated silicon nanowires. The model couples the diffusive reaction of lithium with the lithiation-induced elasto-plastic deformation. We show that the apparent anisotropic swelling is critically controlled by the orientation-dependent mobility of the core-shell interface, i.e., the lithiation reaction rate at the atomically sharp phase boundary between the crystalline core and the amorphous shell. Our results also underscore the importance of structural relaxation by plastic flow behind the moving phase boundary, which is essential to quantitative prediction of the experimentally observed morphologies of lithiated silicon nanowires. The study sheds light on the lithiation-mediated failure in nanowire-based electrodes, and the modeling framework provides a basis for simulating the morphological evolution, stress generation, and fracture in high-capacity electrodes for the next-generation lithium-ion batteries.

  12. Src-dependent phosphorylation of caveolin-1 Tyr-14 promotes swelling and release of caveolae

    PubMed Central

    Zimnicka, Adriana M.; Husain, Yawer S.; Shajahan, Ayesha N.; Sverdlov, Maria; Chaga, Oleg; Chen, Zhenlong; Toth, Peter T.; Klomp, Jennifer; Karginov, Andrei V.; Tiruppathi, Chinnaswamy; Malik, Asrar B.; Minshall, Richard D.

    2016-01-01

    Caveolin 1 (Cav1) is a required structural component of caveolae, and its phosphorylation by Src is associated with an increase in caveolae-mediated endocytosis. Here we demonstrate, using quantitative live-cell 4D, TIRF, and FRET imaging, that endocytosis and trafficking of caveolae are associated with a Cav1 Tyr-14 phosphorylation-dependent conformational change, which spatially separates, or loosens, Cav1 molecules within the oligomeric caveolar coat. When tracked by TIRF and spinning-disk microscopy, cells expressing phosphomimicking Cav1 (Y14D) mutant formed vesicles that were greater in number and volume than with Y14F-Cav1-GFP. Furthermore, we observed in HEK cells cotransfected with wild-type, Y14D, or Y14F Cav1-CFP and -YFP constructs that FRET efficiency was greater with Y14F pairs than with Y14D, indicating that pY14-Cav1 regulates the spatial organization of Cav1 molecules within the oligomer. In addition, albumin-induced Src activation or direct activation of Src using a rapamycin-inducible Src construct (RapR-Src) led to an increase in monomeric Cav1 in Western blots, as well as a simultaneous increase in vesicle number and decrease in FRET intensity, indicative of a Src-mediated conformational change in CFP/YFP-tagged WT-Cav1 pairs. We conclude that phosphorylation of Cav1 leads to separation or “spreading” of neighboring negatively charged N-terminal phosphotyrosine residues, promoting swelling of caveolae, followed by their release from the plasma membrane. PMID:27170175

  13. Temperature-dependent void formation and growth at ion-irradiated nanocrystalline CeO2 Si interfaces

    SciTech Connect

    Perez-Bergquist, Alex G; Zhang, Yanwen; Varga, Tamas; Moll, Sandra; Weber, William J

    2014-01-01

    Ceria is a thermally stable ceramic that has numerous applications in the nuclear industry, including use in nuclear fuels and waste forms. Recently, interest has surged in nanostructured ceria due to its increased mechanical properties and electronic conductivity in comparison with bulk ceria and its ability to self-heal in response to energetic ion bombardment. Here, nanocrystalline ceria thin films grown over a silicon substrate are irradiated to fluences of up to 4 1016 ions/cm2 under different irradiation conditions: with differing ion species (Si+ and Ni+), different ion energies (1.0 1.5 MeV), and at varying temperatures (160 600 K). While the nanocrystalline ceria is found to exhibit exceptional radiation resistance under all tested conditions, severe ion irradiation-induced mixing, void formation, and void growth are observed at the ceria/silicon interface, with the degree of damage proving to be temperature dependent.

  14. Void Nucleation, Growth and Coalescence in Irradiated Metals

    SciTech Connect

    Surh, M P; Sturgeon, J B; Wolfer, W G

    2008-01-11

    A novel computational treatment of dense, stiff, coupled reaction rate equations is introduced to study the nucleation, growth, and possible coalescence of cavities during neutron irradiation of metals. Radiation damage is modeled by the creation of Frenkel pair defects and helium impurity atoms. A multi-dimensional cluster size distribution function allows independent evolution of the vacancy and helium content of cavities, distinguishing voids and bubbles. A model with sessile cavities and no cluster-cluster coalescence can result in a bimodal final cavity size distribution with coexistence of small, high-pressure bubbles and large, low-pressure voids. A model that includes unhindered cavity diffusion and coalescence ultimately removes the small helium bubbles from the system, leaving only large voids. The terminal void density is also reduced and the incubation period and terminal swelling rate can be greatly altered by cavity coalescence. Temperature-dependent trapping of voids/bubbles by precipitates and alterations in void surface diffusion from adsorbed impurities and internal gas pressure may give rise to intermediate swelling behavior through their effects on cavity mobility and coalescence.

  15. The dependence of sea surface slope on atmospheric stability and swell conditions

    NASA Technical Reports Server (NTRS)

    Hwang, Paul A.; Shemdin, Omar H.

    1988-01-01

    A tower-mounted optical device is used to measure the two-orthogonal components of the sea surface slope. The results indicate that an unstable stratification at the air-sea interface tends to enhance the surface roughness. The presence of a long ocean swell system steers the primary direction of shortwave propagation away from wind direction, and may increase or reduce the mean square slope of the sea surface.

  16. Orientation dependence of void growth at triple junction of grain boundaries in nanoscale tricrystal nickel film subjected to uniaxial tensile loading

    NASA Astrophysics Data System (ADS)

    Zhang, Yanqiu; Jiang, Shuyong; Zhu, Xiaoming; Sun, Dong

    2016-11-01

    Molecular dynamics simulation was performed in order to investigate the dependence of void growth on crystallographic orientation at the triple junction of grain boundaries in nanoscale tricrystal nickel film subjected to uniaxial tensile loading. The nucleation, the emission and the transmission of Shockley partial dislocations play a predominant role in the growth of void at the triple junction of grain boundaries. The orientation factors of various slip systems are calculated according to Schmid law. The slip systems activated in a grain of tricrystal nickel film basically conform to Schmid law which is completely suitable for a single crystal. The activated slip systems play an important role in plastic deformation of nanoscale tricrystal nickel film subjected to uniaxial tensile loading. The slip directions exhibit great difference among the activated slip systems such that the void is caused to be subjected to various stress conditions, which further leads to the difference in void growth among the tricrystal nickel films with different orientation distributions. It can be concluded that the grain orientation distribution has a significant influence on void growth at the triple junction of grain boundaries.

  17. Scrotal swelling

    MedlinePlus

    ... determine whether you need any tests. Your health care provider may prescribe antibiotics and pain medications, or recommend surgery. A scrotal ultrasound may be done to find where the swelling is occurring.

  18. Modulation of dog atrial swelling-induced chloride current by cAMP: protein kinase A-dependent and -independent pathways.

    PubMed Central

    Du, X Y; Sorota, S

    1997-01-01

    1. The modulation of dog atrial swelling-induced chloride current (I(Cl,swelling)) by cAMP-elevating agents was studied. Forskolin (10 microM) or isoprenaline (1 microM) exerted multiple effects. Although the pattern between cells was variable, there was, in general, a stimulatory action and a more slowly developing inhibitory effect. 2. In any given cell, the response to forskolin or isoprenaline was qualitatively similar suggesting that all of the responses were dependent on stimulation of adenylyl cyclase. The effects of forskolin or isoprenaline on I(Cl,swelling) were inhibited by intracellular dialysis with a P-site inhibitor of adenylyl cyclase, 2'-deoxyadenosine 3'-monophosphate (300 microM). 3. Intracellular dialysis with a peptide inhibitor of protein kinase A (PKI(6-22); 100 microM) blocked the inhibitory response to forskolin or isoprenaline and all cells responded with a monophasic stimulation of I(Cl,swelling). 4. After intracellular dialysis of cells with PKI(6-22) (100 microM) and cAMP (100 microM), current amplitude was not further stimulated by forskolin. 5. After intracellular dialysis with PKI(6-22) and adenosine 5'-O-(3-thiotriphosphate) (ATPgammaS), forskolin stimulated I(Cl,swelling) and the effect of forskolin subsided after it was washed out. 6. In conclusion, there are dual pathways by which cAMP can modulate dog atrial cell I(Cl,swelling). Inhibition results from protein kinase A (PKA)-dependent phosphorylation. In addition, a stimulatory pathway exists that is independent of phosphorylation by PKA or other cellular kinases. Although alternative explanations are possible, the stimulatory effect of cAMP may represent a direct modulation of I(Cl,swelling). Images Figure 1 PMID:9097937

  19. Plasma Parameter Dependence of Critical Particle Size at the Moment of Void Formation in RF Silane Plasmas

    SciTech Connect

    Seon, C. R.; Chai, K. B.; Choe, W.; Park, S.; Chung, C. W.

    2008-09-07

    Although dust-free voids are frequently observed in many dusty plasmas, experiments regarding the critical particle size for the void formation have not been reported much. In this work, the dust particle size measurement at the critical moment of the void formation was performed by the polarization-sensitive laser light scattering method (PSLLS) as the input rf power was varied in the silane plasmas in which particles were created and grown. The electron temperature and ion density were also measured by a floating probe, and the relation between the parameters was studied. The results show that the critical particle size was decreased from 50 nm to 35 nm as the rf power was increased from 30 W to 100 W. In addition, the electron temperature and ion density were increased from 4.7 eV to 6.2 eV and from 7.0x10{sup 9} cm{sup -3} to 1.4x10{sup 10} cm{sup -3}, respectively. To investigate the mechanism of the void formation, we calculated the critical particle size for the void with measured plasma parameters using a simple one-dimensional force balance equation along the horizontal direction (parallel to the electrode). Consequently, the calculated particle sizes were in good agreement with the measured ones.

  20. Clustering and bias measurements of SDSS voids

    NASA Astrophysics Data System (ADS)

    Clampitt, Joseph; Jain, Bhuvnesh; Sánchez, Carles

    2016-03-01

    Using a void catalogue from the Sloan Digital Sky Survey, we present the first measurements of void clustering and the corresponding void bias. Over the range 30-200 Mpc h-1, the void autocorrelation is detected at 5σ significance for voids of radius 15-20 Mpc h-1. We also measure the void-galaxy cross-correlation at higher signal to noise and compare the inferred void bias with the autocorrelation results. Void bias is constant with scale for voids of a given size, but its value falls from 5.6 ± 1.0 to below zero as the void radius increases from 15 to 30 Mpc h-1. The comparison of our measurements with carefully matched galaxy mock catalogues, with no free parameters related to the voids, shows that model predictions can be reliably made for void correlations. We study the dependence of void bias on tracer density and void size with a view to future applications. In combination with our previous lensing measurements of void mass profiles, these clustering measurements provide another step towards using voids as cosmological tracers.

  1. Dependence of the rate of steady-state swelling of fuel-element claddings made of ChS68 steel on the characteristics of neutron irradiation

    NASA Astrophysics Data System (ADS)

    Kozlov, A. V.; Portnykh, I. A.

    2016-08-01

    Rate of steady-state swelling of fuel-element sheaths made of the 06Kh16N15M2G2TFR steel in the course of their operation in a BN-600 reactor has been calculated. In the calculations, the diffusion characteristics of point defects and the results of the determination of the characteristics of the irradiation-induced porosity have been used. The dependence of the dose rate of steady-state swelling on neutron-irradiation characteristics has been analyzed. It has been established that the dose rate of swelling at the steady-state stage is independent of the energy of migration of vacancies and the rate of generation of atomic displacements.

  2. Formation Of Voids In Dusty Lorentzian Plasma

    SciTech Connect

    Bahamida, S.; Annou, K.; Annou, R.

    2008-09-07

    We study the possibility of formation of voids in Lorentzian plasmas containing of dust particles obeying to vortex-like velocity distribution. The size of the void is found to be ion spectral index dependent.

  3. Swelling of phospholipid membranes by divalent metal ions depends on the location of the ions in the bilayers.

    PubMed

    Alsop, Richard J; Maria Schober, Rafaëla; Rheinstädter, Maikel C

    2016-08-10

    The Hofmeister series illustrates how salts produce a wide range of effects in biological systems, which are not exclusively explained by ion charge. In lipid membranes, charged ions have been shown to bind to lipids and either hydrate or dehydrate lipid head groups, and also to swell the water layer in multi-lamellar systems. Typically, Hofmeister phenomena are explained by the interaction of the ions with water, as well as with biological interfaces, such as proteins or membranes. We studied the effect of the divalent cations Mg(2+), Ca(2+), Fe(2+), and Zn(2+) on oriented, stacked, phospholipid bilayers made of dimyristoylphosphatidylcholine (DMPC). Using high-resolution X-ray diffraction, we observed that the cations lead to a swelling of the water layer between the bilayers, without causing significant changes to the bilayer structure. The cations swelled the bilayers in different amounts, in the order Fe(2+) > Mg(2+) > Ca(2+) > Zn(2+). By decomposing the total bilayer electron density into different molecular groups, Zn(2+) and Ca(2+) were found to interact with the glycerol groups of the lipid molecules and cause minor swelling of the bilayers. Mg(2+) and Fe(2+) were found to position near the phosphate groups and cause a strong increase in the number of hydration water molecules. Our results present a molecular mechanism-of-action for the Hofmeister series in phospholipid membranes. PMID:27453289

  4. Malonate induces cell death via mitochondrial potential collapse and delayed swelling through an ROS-dependent pathway

    PubMed Central

    Fernandez-Gomez, Francisco J; Galindo, Maria F; Gómez-Lázaro, Maria; Yuste, Victor J; Comella, Joan X; Aguirre, Norberto; Jordán, Joaquín

    2005-01-01

    Herein we study the effects of the mitochondrial complex II inhibitor malonate on its primary target, the mitochondrion. Malonate induces mitochondrial potential collapse, mitochondrial swelling, cytochrome c (Cyt c) release and depletes glutathione (GSH) and nicotinamide adenine dinucleotide coenzyme (NAD(P)H) stores in brain-isolated mitochondria. Although, mitochondrial potential collapse was almost immediate after malonate addition, mitochondrial swelling was not evident before 15 min of drug presence. This latter effect was blocked by cyclosporin A (CSA), Ruthenium Red (RR), magnesium, catalase, GSH and vitamin E. Malonate added to SH-SY5Y cell cultures produced a marked loss of cell viability together with the release of Cyt c and depletion of GSH and NAD(P)H concentrations. All these effects were not apparent in SH-SY5Y cells overexpressing Bcl-xL. When GSH concentrations were lowered with buthionine sulphoximine, cytoprotection afforded by Bcl-xL overexpression was not evident anymore. Taken together, all these data suggest that malonate causes a rapid mitochondrial potential collapse and reactive oxygen species production that overwhelms mitochondrial antioxidant capacity and leads to mitochondrial swelling. Further permeability transition pore opening and the subsequent release of proapoptotic factors such as Cyt c could therefore be, at least in part, responsible for malonate-induced toxicity. PMID:15655518

  5. On the universality of void density profiles

    NASA Astrophysics Data System (ADS)

    Ricciardelli, E.; Quilis, V.; Varela, J.

    2016-10-01

    The massive exploitation of cosmic voids for precision cosmology in the upcoming dark energy experiments, requires a robust understanding of their internal structure, particularly of their density profile. We show that the void density profile is insensitive to the void radius both in a catalogue of observed voids and in voids from a large cosmological simulation. However, the observed and simulated voids display remarkably different profile shapes, with the former having much steeper profiles than the latter. We ascribe such difference to the dependence of the observed profiles on the galaxy sample used to trace the matter distribution. Samples including low-mass galaxies lead to shallower profiles with respect to the samples where only massive galaxies are used, as faint galaxies live closer to the void centre. We argue that galaxies are biased tracers when used to probe the matter distribution within voids.

  6. The nature of voids - I. Watershed void finders and their connection with theoretical models

    NASA Astrophysics Data System (ADS)

    Nadathur, S.; Hotchkiss, S.

    2015-12-01

    The statistical study of voids in the matter distribution promises to be an important tool for precision cosmology, but there are known discrepancies between theoretical models of voids and the voids actually found in large simulations or galaxy surveys. The empirical properties of observed voids are also not well understood. In this paper, we study voids in an N-body simulation, using the ZOBOV watershed algorithm. As in other studies, we use sets of subsampled dark matter particles as tracers to identify voids, but we use the full-resolution simulation output to measure dark matter densities at the identified locations. Voids span a wide range of sizes and densities, but there is a clear trend towards larger voids containing deeper density minima, a trend which is expected for all watershed void finders. We also find that the tracer density at void locations is usually smaller than the true density, and that this relationship depends on the sampling density of tracers. We show that fits given in the literature fail to match the observed density profiles of voids. The average enclosed density contrast within watershed voids varies widely with both the size of the void and the minimum density within it, but is always far from the shell-crossing threshold expected from theoretical models. Voids with deeper density minima also show much broader density profiles. We discuss the implications of these results for the excursion set approach to modelling such voids.

  7. The temperature dependence of void and bubble formation and growth in aluminium during 600 MeV proton irradiation

    NASA Astrophysics Data System (ADS)

    Victoria, M.; Green, W. V.; Singh, B. N.; Leffers, T.

    1984-05-01

    As a part of a continuing program, we report in the present paper results obtained from irradiating pure aluminium samples in the PIREX facility installed in the 600 MeV proton beam of the accelerator at the Swiss Institute for Nuclear Research (SIN). The aluminium foils have been irradiated at 8 different temperatures in the range from 130°-430°C, to displacement doses of up to 5 dpa and helium contents of over 1000 appm. The TEM examinations have shown that at all irradiation temperatures and displacement doses, helium bubbles are formed uniformly through the whole grain interior. No voids are observed at temperatures above 160° C. At all temperatures, irradiation induced dislocations have been observed, most of them linked to bubbles. At higher temperatures and doses, clear evidence of irradiation induced precipitation has been observed; the precipitates are normally decorated with helium bubbles.

  8. Influence of silicon on swelling and microstructure in Russian austenitic stainless steel EI-847 irradiated to high neutron doses

    NASA Astrophysics Data System (ADS)

    Porollo, S. I.; Shulepin, S. V.; Konobeev, Yu. V.; Garner, F. A.

    2008-08-01

    Void swelling and microstructural development of niobium-stabilized EI-847 austenitic stainless steel with a range of silicon levels were investigated by destructive examination of fuel pin cladding irradiated in three fast reactors located in either Russia or Kazakhstan. The tendency of void swelling to be progressively reduced by increasing silicon concentration appears to be a very general phenomenon in this steel, whether observed in simple, single-variable experiments on well-defined materials or when observed in multivariable, time-dependent irradiations conducted on commercially produced steels over a wide range of irradiation temperatures, neutron spectra and dpa rates. The role of silicon on microstructural development is expressed both in the solid solution via its influence on dislocation and void microstructure and via its influence on formation of radiation-induced phases that in turn alter the matrix composition. Surprisingly, increases in silicon level in this study do not accelerate the formation of silicon-rich G-phase, but act to increase the formation of Nb (C,N) precipitates. Such precipitates are known to be associated with delayed void swelling.

  9. Foot, leg, and ankle swelling

    MedlinePlus

    Swelling of the ankles - feet - legs; Ankle swelling; Foot swelling; Leg swelling; Edema - peripheral; Peripheral edema ... Painless swelling may affect both legs and may include the calves or ... of gravity makes the swelling most noticeable in the lower ...

  10. Universal void density profiles from simulation and SDSS

    NASA Astrophysics Data System (ADS)

    Nadathur, S.; Hotchkiss, S.; Diego, J. M.; Iliev, I. T.; Gottlöber, S.; Watson, W. A.; Yepes, G.

    2016-10-01

    We discuss the universality and self-similarity of void density profiles, for voids in realistic mock luminous red galaxy (LRG) catalogues from the Jubilee simulation, as well as in void catalogues constructed from the SDSS LRG and Main Galaxy samples. Voids are identified using a modified version of the ZOBOV watershed transform algorithm, with additional selection cuts. We find that voids in simulation are self-similar, meaning that their average rescaled profile does not depend on the void size, or - within the range of the simulated catalogue - on the redshift. Comparison of the profiles obtained from simulated and real voids shows an excellent match. The profiles of real voids also show a universal behaviour over a wide range of galaxy luminosities, number densities and redshifts. This points to a fundamental property of the voids found by the watershed algorithm, which can be exploited in future studies of voids.

  11. Dynamic void behavior in polymerizing polymethyl methacrylate cement.

    PubMed

    Muller, Scott D; McCaskie, Andrew W

    2006-02-01

    Cement mantle voids remain controversial with respect to survival of total hip arthroplasty. Void evolution is poorly understood, and attempts at void manipulation can only be empirical. We induced voids in a cement model simulating the constraints of the proximal femur. Intravoid pressure and temperature were recorded throughout polymerization, and the initial and final void volumes were measured. Temperature-dependent peak intravoid pressures and void volume increases were observed. After solidification, subatmospheric intravoid pressures were observed. The magnitude of these observations could not be explained by the ideal gas law. Partial pressures of the void gas at peak pressures demonstrated a dominant effect of gaseous monomer, thereby suggesting that void growth is a pressure-driven phenomenon resulting from temperature-dependent evaporation of monomer into existing trapped air voids. PMID:16520219

  12. Effect of radiation-induced segregation on void nucleation

    SciTech Connect

    Si-Ahmed, A.; Wolfer, W.G.

    1982-01-01

    The effect of segregation on void nucleation is investigated utilizing previous results for the capture efficiency of coated void. First, it is shown that any segregation, whether or not it leads to actual precipitation, leads to a modification of the bias factors for any sink. Small increases of either the lattice parameters or the elastic moduli result in reduced interstitial bias factors. Second, segregations to void embryos not only changes their capture efficiencies but also the surface energy. The effect of these changes on the void nucleation rate is studied in quantitative terms. When the segregation to voids results in an increase of the local lattice parameters by 0.4% or an increase of the shear modulus by 3%, the ultimate void nucleation rate is reached. Further increases no longer enhance void nucleation. Void nucleation without segregation effects would only be possible if the dislocation bias exceeds 50%. With segregation, void nucleation is not strongly dependent on the dislocation bias.

  13. Dynamic Void Growth and Shrinkage in Mg under Electron Irradiation

    SciTech Connect

    Xu, W. Z.; Zhang, Y. F.; Cheng, G. M.; Jian, W. W.; Millett, P. C.; Koch, C. C.; Mathaudhu, S. N.; Zhu, Y. T.

    2014-04-30

    We report in-situ atomic-scale investigation of void evolution, including growth, coalescence and shrinkage, under electron irradiation. With increasing irradiation dose, the total volume of voids increased linearly, while nucleation rate of new voids decreased slightly, and the total number of voids decreased. Some voids continued to grow while others shrank to disappear, depending on the nature of their interactions with nearby self-interstitial loops. For the first time, surface diffusion of adatoms was observed largely responsible for the void coalescence and thickening. These findings provide fundamental understanding to help with the design and modeling of irradiation-resistant materials.

  14. The sparkling Universe: a scenario for cosmic void motions

    NASA Astrophysics Data System (ADS)

    Ceccarelli, Laura; Ruiz, Andrés N.; Lares, Marcelo; Paz, Dante J.; Maldonado, Victoria E.; Luparello, Heliana E.; Garcia Lambas, Diego

    2016-10-01

    Cosmic voids are prominent features of the Universe, encoding relevant information of the growth and evolution of structure through their dynamics. Here, we perform a statistical study of the global motion of cosmic voids using both a numerical simulation and observational data. Their relation to large-scale mass flows and the physical effects that drive those motions. We analyse the bulk motions of voids, finding void mean bulk velocities in the range 300-400 km s-1, depending on void size and the large-scale environment. Statistically, small voids move faster, and voids in relatively higher density environments have higher bulk velocities. Also, we find large-scale overdensities (underdensities) along (opposite to) the void motion direction, suggesting that void motions respond to a pull-push mechanism. Our analysis suggests that their relative motions are generated by large-scale density fluctuations. In agreement with linear theory, voids embedded in low (high) density regions mutually recede (attract) each other, providing the general mechanism to understand the bimodal behaviour of void motions. We have also inferred void motions in the Sloan Digital Sky Survey using linear theory, finding that their estimated motions are in qualitatively agreement with the results of the simulation. Our results suggest a scenario of galaxies and galaxy systems flowing away from void centres with the additional, and more relevant, contribution of the void bulk motion to the total velocity.

  15. The nature of voids - II. Tracing underdensities with biased galaxies

    NASA Astrophysics Data System (ADS)

    Nadathur, S.; Hotchkiss, S.

    2015-11-01

    We study how the properties of cosmic voids depend on those of the tracer galaxy populations in which they are identified. We use a suite of halo occupation distribution mocks in a simulation, identify voids in these populations using the ZOBOV void finder and measure their abundances, sizes, tracer densities and dark matter content. To separate the effects of bias from those of sampling density, we do the same for voids traced by randomly downsampled subsets of the simulation dark matter particles. At the same sampling density, galaxy bias reduces the total number of voids by ˜50 per cent and can dramatically change their size distribution. The matter content of voids in biased and unbiased tracers also differs. Deducing void properties from simulation therefore requires the use of realistic galaxy mocks. We discuss how the void observables can be related to their matter content. In particular we consider the compensation of the total mass deficit in voids and find that the distinction between over- and undercompensated voids is not a function of void size alone, as has previously been suggested. However, we find a simple linear relationship between the average density of tracers in the void and the total mass compensation on much larger scales. The existence of this linear relationship holds independent of the bias and sampling density of the tracers. This provides a universal tool to classify void environments and will be important for the use of voids in observational cosmology.

  16. Temperature dependence of helium-implantation-induced lattice swelling in polycrystalline tungsten: X-ray micro-diffraction and Eigenstrain modelling

    SciTech Connect

    de Broglie, I.; Beck, C. E.; Liu, W.; Hofmann, Felix

    2015-05-30

    Using synchrotron X-ray micro-diffraction and Eigenstrain analysis the distribution of lattice swelling near grain boundaries in helium-implanted polycrystalline tungsten is quantified. Samples heat-treated at up to 1473 K after implantation show less uniform lattice swelling that varies significantly from grain to grain compared to as-implanted samples. An increase in lattice swelling is found in the vicinity of some grain boundaries, even at depths beyond the implanted layer. As a result, these findings are discussed in terms of the evolution of helium-ion-implantation-induced defects.

  17. Breather mechanism of the void ordering in crystals under irradiation

    NASA Astrophysics Data System (ADS)

    Dubinko, Vladimir

    2009-09-01

    The void ordering has been observed in very different radiation environments ranging from metals to ionic crystals. In the present paper the ordering phenomenon is considered as a consequence of the energy transfer along the close packed directions provided by self-focusing discrete breathers. The self-focusing breathers are energetic, mobile and highly localized lattice excitations that propagate great distances in atomic-chain directions in crystals. This points to the possibility of atoms being ejected from the void surface by the breather-induced mechanism, which is similar to the focuson-induced mechanism of vacancy emission from voids proposed in our previous paper. The main difference between focusons and breathers is that the latter are stable against thermal motion. There is evidence that breathers can occur in various crystals, with path lengths ranging from 104 to 107 unit cells. Since the breather propagating range can be larger than the void spacing, the voids can shield each other from breather fluxes along the close packed directions, which provides a driving force for the void ordering. Namely, the vacancy emission rate for "locally ordered" voids (which have more immediate neighbors along the close packed directions) is smaller than that for the "interstitial" ones, and so they have some advantage in growth. If the void number density is sufficiently high, the competition between them makes the "interstitial" voids shrink away resulting in the void lattice formation. The void ordering is intrinsically connected with a saturation of the void swelling, which is shown to be another important consequence of the breather-induced vacancy emission from voids.

  18. Pores and Void in Asclepiades’ Physical Theory

    PubMed Central

    Leith, David

    2012-01-01

    This paper examines a fundamental, though relatively understudied, aspect of the physical theory of the physician Asclepiades of Bithynia, namely his doctrine of pores. My principal thesis is that this doctrine is dependent on a conception of void taken directly from Epicurean physics. The paper falls into two parts: the first half addresses the evidence for the presence of void in Asclepiades’ theory, and concludes that his conception of void was basically that of Epicurus; the second half focuses on the precise nature of Asclepiadean pores, and seeks to show that they represent void interstices between the primary particles of matter which are the constituents of the human body, and are thus exactly analogous to the void interstices between atoms within solid objects in Epicurus’ theory. PMID:22984299

  19. Pores and Void in Asclepiades' Physical Theory.

    PubMed

    Leith, David

    2012-01-01

    This paper examines a fundamental, though relatively understudied, aspect of the physical theory of the physician Asclepiades of Bithynia, namely his doctrine of pores. My principal thesis is that this doctrine is dependent on a conception of void taken directly from Epicurean physics. The paper falls into two parts: the first half addresses the evidence for the presence of void in Asclepiades' theory, and concludes that his conception of void was basically that of Epicurus; the second half focuses on the precise nature of Asclepiadean pores, and seeks to show that they represent void interstices between the primary particles of matter which are the constituents of the human body, and are thus exactly analogous to the void interstices between atoms within solid objects in Epicurus' theory. PMID:22984299

  20. Modeling cosmic void statistics

    NASA Astrophysics Data System (ADS)

    Hamaus, Nico; Sutter, P. M.; Wandelt, Benjamin D.

    2016-10-01

    Understanding the internal structure and spatial distribution of cosmic voids is crucial when considering them as probes of cosmology. We present recent advances in modeling void density- and velocity-profiles in real space, as well as void two-point statistics in redshift space, by examining voids identified via the watershed transform in state-of-the-art ΛCDM n-body simulations and mock galaxy catalogs. The simple and universal characteristics that emerge from these statistics indicate the self-similarity of large-scale structure and suggest cosmic voids to be among the most pristine objects to consider for future studies on the nature of dark energy, dark matter and modified gravity.

  1. Prediction of swelling rocks strain in tunneling

    NASA Astrophysics Data System (ADS)

    Parsapour, D.; Fahimifar, A.

    2016-05-01

    Swelling deformations leading to convergence of tunnels may result in significant difficulties during the construction, in particular for long term use of tunnels. By extracting an experimental based explicit analytical solution for formulating swelling strains as a function of time and stress, swelling strains are predicted from the beginning of excavation and during the service life of tunnel. Results obtained from the analytical model show a proper agreement with experimental results. This closed-form solution has been implemented within a numerical program using the finite element method for predicting time-dependent swelling strain around tunnels. Evaluating effects of swelling parameters on time-dependent strains and tunnel shape on swelling behavior around the tunnel according to this analytical solution is considered. The ground-support interaction and consequent swelling effect on the induced forces in tunnel lining is considered too. Effect of delay in lining installation on swelling pressure which acting on the lining and its structural integrity, is also evaluated. A MATLAB code of " SRAP" is prepared and applied to calculate all swelling analysis around tunnels based on analytical solution.

  2. Testing spherical evolution for modelling void abundances

    NASA Astrophysics Data System (ADS)

    Achitouv, Ixandra; Neyrinck, Mark; Paranjape, Aseem

    2015-08-01

    We compare analytical predictions of void volume functions to those measured from N-body simulations, detecting voids with the ZOBOV void finder. We push to very small, non-linear voids, below few Mpc radius, by considering the unsampled dark matter density field. We also study the case where voids are identified using haloes. We develop analytical formula for the void abundance of both the excursion set approach and the peaks formalism. These formulas are valid for random walks smoothed with a top-hat filter in real space, with a large class of realistic barrier models. We test the extent to which the spherical evolution approximation, which forms the basis of the analytical predictions, models the highly aspherical voids that occur in the cosmic web, and are found by a watershed-based algorithm such as ZOBOV. We show that the volume function returned by ZOBOV is quite sensitive to the choice of treatment of subvoids, a fact that has not been appreciated previously. For reasonable choices of subvoid exclusion, we find that the Lagrangian density δv of the ZOBOV voids - which is predicted to be a constant δv ≈ -2.7 in the spherical evolution model - is different from the predicted value, showing substantial scatter and scale dependence. This result applies to voids identified at z = 0 with effective radius between 1 and 10 h-1 Mpc. Our analytical approximations are flexible enough to give a good description of the resulting volume function; however, this happens for choices of parameter values that are different from those suggested by the spherical evolution assumption. We conclude that analytical models for voids must move away from the spherical approximation in order to be applied successfully to observations, and we discuss some possible ways forward.

  3. Gas in void galaxies

    NASA Astrophysics Data System (ADS)

    Kreckel, Kathryn Joyce

    Void galaxies, residing within the deepest underdensities of the Cosmic Web, present an ideal population for the study of galaxy formation and evolution in an environment undisturbed by the complex processes modifying galaxies in clusters and groups, and provide an observational test for theories of cosmological structure formation. We investigate the neutral hydrogen properties (i.e. content, morphology, kinematics) of void galaxies, both individually and systematically, using a combination of observations and simulations, to form a more complete understanding of the nature of these systems. We investigate in detail the H I morphology and kinematics of two void galaxies. One is an isolated polar disk galaxy in a diffuse cosmological wall situated between two voids. The considerable gas mass and apparent lack of stars in the polar disk, coupled with the general underdensity of the environment, supports recent theories of cold flow accretion as an alternate formation mechanism for polar disk galaxies. We also examine KK 246, the only confirmed galaxy located within the nearby Tully Void. It is a dwarf galaxy with an extremely extended H I disk and signs of an H I cloud with anomalous velocity. It also exhibits clear misalignment between the kinematical major and minor axes, and a general misalignment between the H I and optical major axes. The relative isolation and extreme underdense environment make these both very interesting cases for examining the role of gas accretion in galaxy evolution. To study void galaxies as a population, we have carefully selected a sample of 60 galaxies that reside in the deepest underdensities of geometrically identified voids within the SDSS. We have imaged this new Void Galaxy Survey in H I at the Westerbork Synthesis Radio Telescope with a typical resolution of 8 kpc, probing a volume of 1.2 Mpc and 12,000 km s^-1 surrounding each galaxy. We reach H I mass limits of 2 x 10^8 M_sun and column density sensitivities of 5 x 10^19 cm^-2

  4. Voids in neutron-irradiated metals and alloys

    SciTech Connect

    Hendricks, R.W.

    1980-01-01

    Small-angle x-ray and neutron scattering are powerful analytical tools for investigating long-range fluctuations in electron (x-rays) or magnetic moment (neutrons) densities in materials. In recent years they have yielded valuable information about voids, void size distributions, and swelling in aluminum, aluminum alloys, copper, molybdenum, nickel, nickel-aluminum, niobium and niobium alloys, stainless steels, graphite and silicon carbide. In the case of aluminum, information concerning the shape of the voids and the ratio of specific surface energies was obtained. The technique of small-angle scattering and its application to the study of voids is reviewed in the paper. Emphasis is placed on the conditions which limit the applicability of the technique, on the interpretation of the data, and on a comparison of the results obtained with companion techniques such as transmission electron microscopy and bulk density. 8 figures, 41 references.

  5. Shales and swelling soils

    NASA Astrophysics Data System (ADS)

    Franklin, J. A.; Dimillio, A. F.; Strohm, W. E., Jr.; Vandre, B. C.; Anderson, L. R.

    The thirteen (13) papers in this report deal with the following areas: a shale rating system and tentative applications to shale performance; technical guidelines for the design and construction of shale embankments; stability of waste shale embankments; dynamic response of raw and stabilized Oklahoma shales; laboratory studies of the stabilization of nondurable shales; swelling shale and collapsing soil; development of a laboratory compaction degradation test for shales; soil section approach for evaluation of swelling potential soil moisture properties of subgrade soils; volume changes in compacted clays and shales on saturation; characterization of expansive soils; pavement roughness on expansive clays; and deep vertical fabric moisture barriers in swelling soils.

  6. The Irradiation Effect of a Simultaneous Laser and Electron Dual-beam on Void Formation

    PubMed Central

    Yang, Zhanbing; Watanabe, Seiichi; Kato, Takahiko

    2013-01-01

    Randomly distributed lattice point defects such as supersaturated vacancies (SVs) and Frenkel-pairs (FPs, an interstitial and a vacancy) can be simultaneously introduced into the crystal by energetic beam irradiation in outer space and/or nuclear reactors, but their behavior has not been fully understood. Using a high-voltage electron microscope equipped with a laser (laser-HVEM), we show the striking effects of simultaneous laser-electron (photon-electron) dual-beam irradiation on void formation. Our results reveal that during laser-electron sequential irradiation, pre-laser irradiation enhanced void nucleation and subsequent electron irradiation enhanced void growth. However, the laser-electron dual-beam irradiation was analyzed to depress void swelling remarkably because the recombination of SVs and interstitials was enhanced. The results provide insight into the mechanism underlying the dual-beam radiation-induced depression of void swelling in solids. PMID:23383371

  7. The irradiation effect of a simultaneous laser and electron dual-beam on void formation.

    PubMed

    Yang, Zhanbing; Watanabe, Seiichi; Kato, Takahiko

    2013-01-01

    Randomly distributed lattice point defects such as supersaturated vacancies (SVs) and Frenkel-pairs (FPs, an interstitial and a vacancy) can be simultaneously introduced into the crystal by energetic beam irradiation in outer space and/or nuclear reactors, but their behavior has not been fully understood. Using a high-voltage electron microscope equipped with a laser (laser-HVEM), we show the striking effects of simultaneous laser-electron (photon-electron) dual-beam irradiation on void formation. Our results reveal that during laser-electron sequential irradiation, pre-laser irradiation enhanced void nucleation and subsequent electron irradiation enhanced void growth. However, the laser-electron dual-beam irradiation was analyzed to depress void swelling remarkably because the recombination of SVs and interstitials was enhanced. The results provide insight into the mechanism underlying the dual-beam radiation-induced depression of void swelling in solids.

  8. Voids of dark energy

    SciTech Connect

    Dutta, Sourish; Maor, Irit

    2007-03-15

    We investigate the clustering properties of a dynamical dark energy component. In a cosmic mix of a pressureless fluid and a light scalar field, we follow the linear evolution of spherical matter perturbations. We find that the scalar field tends to form underdensities in response to the gravitationally collapsing matter. We thoroughly investigate these voids for a variety of initial conditions, explain the physics behind their formation, and consider possible observational implications. Detection of dark energy voids will clearly rule out the cosmological constant as the main source of the present acceleration.

  9. Influence of nickel and beryllium content on swelling behavior of copper irradiated with fast neutrons

    SciTech Connect

    Singh, B.N.; Garner, F.A.; Edwards, D.J.; Evans, J.H.

    1996-10-01

    In the 1970`s, the effects of nickel content on the evolution of dislocation microstructures and the formation and growth of voids in Cu-Ni alloys were studied using 1 MeV electrons in a high voltage electron microscope. The swelling rate was found to decrease rapidly with increasing nickel content. The decrease in the swelling rate was associated with a decreasing void growth rate with increasing nickel content at irradiation temperatures up to 450{degrees}C. At 500{degrees}C, both void size and swelling rate were found to peak at 1 and 2% Ni, respectively, and then to decrease rapidly with increasing nickel content. However, recent work has demonstrated that the swelling behavior of Cu-5%Ni irradiated with fission neutrons is very similar for that of pure copper. The present experiments were designed to investigate this apparent discrepancy.

  10. Urethroscrotal Fistula: A Rare Cause of Scrotal Swelling

    PubMed Central

    Parlak, Selcuk; Okay, Aysun E.

    2016-01-01

    Summary Background Urethroscrotal fistula (USF) is an abnormal communication between the urethra and the scrotum. This rare abnormality may be iatrogenic or secondary to perforation of the urethra by a stone. After the passage of urine to the scrotum through the fistula, painless scrotal swelling develops, which disappears completely with manual compression, and voiding can be maintained in this way. Retrograde urethrography (RU) and voiding cystourethrography (VCU) are traditional diagnostic methods, but they have limitations, such as technical difficulties and inability to evaluate the surrounding tissues. Multidetector CT (MDCT), together with reformatted images, can provide valuable information about the surrounding tissues and associated pathologies. Case Report We present a case of a 36-year-old male patient who had painless scrotal swelling after cystolithotomy and urethral stone surgery. The patient indicated that the swelling disappeared after manual compression. A fistula between the bulbous urethra and the scrotum was discovered by MDCT. In our case, we believe that the fistula developed iatrogenically during stone excision or secondary to perforation of the urethra by a stone. Conclusions As a rare pathology, urethroscrotal fistula should be considered in men with a history of urethral stone surgery and symptoms, including painless scrotal swelling, which can be manually compressed after voiding.

  11. Urethroscrotal Fistula: A Rare Cause of Scrotal Swelling

    PubMed Central

    Parlak, Selcuk; Okay, Aysun E.

    2016-01-01

    Summary Background Urethroscrotal fistula (USF) is an abnormal communication between the urethra and the scrotum. This rare abnormality may be iatrogenic or secondary to perforation of the urethra by a stone. After the passage of urine to the scrotum through the fistula, painless scrotal swelling develops, which disappears completely with manual compression, and voiding can be maintained in this way. Retrograde urethrography (RU) and voiding cystourethrography (VCU) are traditional diagnostic methods, but they have limitations, such as technical difficulties and inability to evaluate the surrounding tissues. Multidetector CT (MDCT), together with reformatted images, can provide valuable information about the surrounding tissues and associated pathologies. Case Report We present a case of a 36-year-old male patient who had painless scrotal swelling after cystolithotomy and urethral stone surgery. The patient indicated that the swelling disappeared after manual compression. A fistula between the bulbous urethra and the scrotum was discovered by MDCT. In our case, we believe that the fistula developed iatrogenically during stone excision or secondary to perforation of the urethra by a stone. Conclusions As a rare pathology, urethroscrotal fistula should be considered in men with a history of urethral stone surgery and symptoms, including painless scrotal swelling, which can be manually compressed after voiding. PMID:27668028

  12. THE ORIENTATION OF DISK GALAXIES AROUND LARGE COSMIC VOIDS

    SciTech Connect

    Varela, Jesus; Betancort-Rijo, Juan; Trujillo, Ignacio; Ricciardelli, Elena

    2012-01-10

    Using a large sample of galaxies from the the seventh data release of the Sloan Digital Sky Survey (SDSS-DR7), we have analyzed the alignment of disk galaxies around cosmic voids. We have constructed a complete sample of cosmic voids (devoid of galaxies brighter than M{sub r} - 5log h = -20.17) with radii larger than 10 h{sup -1} Mpc up to redshift 0.12. Disk galaxies in shells around these voids have been used to look for particular alignments between the angular momentum of the galaxies and the radial direction of the voids. We find that disk galaxies around voids larger than {approx}> 15 h{sup -1} Mpc within distances not much larger than 5 h{sup -1} Mpc from the surface of the voids present a significant tendency to have their angular momenta aligned with the void's radial direction with a significance {approx}> 98.8% against the null hypothesis. The strength of this alignment is dependent on the void's radius and for voids with a radius {approx}< 15 h{sup -1} Mpc the distribution of the orientation of the galaxies is compatible with a random distribution. Finally, we find that this trend observed in the alignment of galaxies is similar to the one observed for the minor axis of dark matter halos around cosmic voids found in cosmological simulations, suggesting a possible link in the evolution of both components.

  13. Tensor anisotropy as a tracer of cosmic voids

    NASA Astrophysics Data System (ADS)

    Bustamante, Sebastian; Forero-Romero, Jaime E.

    2015-10-01

    We present a new method to find voids in cosmological simulations based on the tidal and the velocity shear tensors definitions of the cosmic web. We use the fractional anisotropy (FA) computed from the eigenvalues of each web scheme as a void tracer. We identify voids using a watershed transform based on the local minima of the FA field without making any assumption on the shape or structure of the voids. We test the method on the Bolshoi simulation and report on the abundance and radial averaged profiles for the density, velocity and FA. We find that voids in the velocity shear web are smaller than voids in the tidal web, with a particular overabundance of very small voids in the inner region of filaments/sheets. We classify voids as subcompensated/overcompensated depending on the absence/presence of an overdense matter ridge in their density profile, finding that close to 65 and 35 per cent of the total population are classified into each category, respectively. Finally, we find evidence for the existence of universal profiles from the radially averaged profiles for density, velocity and FA. This requires that the radial coordinate is normalized to the effective radius of each void. Put together, all these results show that the FA is a reliable tracer for voids, which can be used in complementarity to other existing methods and tracers.

  14. Surface Fractal Dimension of Bentonite and its Application in Calculation of Swelling Deformation

    NASA Astrophysics Data System (ADS)

    Xiang, G. S.; Xu, Y. F.; Jiang, H.

    2014-09-01

    The correlation between the void ratio of swelled montmorillonite and the vertical overburden pressure can be expressed as {e}{ m} = Kp{ s}{D{ s}-3}. The surface fractal dimension Ds of five bentonites were estimated from the swelling deformation tests according to this fractal correlation. The reliability of surface fractal dimension obtained from the swelling deformation test was confirmed by nitrogen adsorption test, with identical values of surface fractal dimension obtained from both tests. The surface fractal dimension can also be used to estimate the swelling deformation of bentonite, after calculating the swelling coefficient K from the parameters of diffuse double layer (DDL) model in the osmotic swelling phase. Comparison of the model predictions with a number of experimental results on swelling deformation of both Na dominant and Ca dominant bentonites suggests that the surface fractal model works excellent in the cases tested.

  15. Intermittent facial swelling

    PubMed Central

    Pope, Charlie; Gopala Pillai, Suresh Kumar

    2014-01-01

    Intermittent facial swelling is an unusual presentation in the emergency department. The differential diagnosis may range from a variety of causes. Most common differential diagnosis is angio-oedema. However, more serious presentations such as superior venacaval obstruction must not be ignored. This case report presents a patient who was investigated in the hospital for 2 weeks (2 admissions) with intermittent facial swelling. He presented to the emergency department (3rd admission) and was diagnosed to have superior venacaval obstruction secondary to metastatic bronchogenic carcinoma. He underwent emergency endovascular stenting; however, he died within a few weeks. PMID:25326556

  16. Reliability Impact of Stockpile Aging: Stress Voiding

    SciTech Connect

    ROBINSON,DAVID G.

    1999-10-01

    The objective of this research is to statistically characterize the aging of integrated circuit interconnects. This report supersedes the stress void aging characterization presented in SAND99-0975, ''Reliability Degradation Due to Stockpile Aging,'' by the same author. The physics of the stress voiding, before and after wafer processing have been recently characterized by F. G. Yost in SAND99-0601, ''Stress Voiding during Wafer Processing''. The current effort extends this research to account for uncertainties in grain size, storage temperature, void spacing and initial residual stress and their impact on interconnect failure after wafer processing. The sensitivity of the life estimates to these uncertainties is also investigated. Various methods for characterizing the probability of failure of a conductor line were investigated including: Latin hypercube sampling (LHS), quasi-Monte Carlo sampling (qMC), as well as various analytical methods such as the advanced mean value (Ah/IV) method. The comparison was aided by the use of the Cassandra uncertainty analysis library. It was found that the only viable uncertainty analysis methods were those based on either LHS or quasi-Monte Carlo sampling. Analytical methods such as AMV could not be applied due to the nature of the stress voiding problem. The qMC method was chosen since it provided smaller estimation error for a given number of samples. The preliminary results indicate that the reliability of integrated circuits due to stress voiding is very sensitive to the underlying uncertainties associated with grain size and void spacing. In particular, accurate characterization of IC reliability depends heavily on not only the frost and second moments of the uncertainty distribution, but more specifically the unique form of the underlying distribution.

  17. Molecular accessibility in solvent swelled coals

    SciTech Connect

    Kispert, L.D.

    1993-02-01

    An EPR technique developed in this lab is being used to determine the pore size and number distribution changes after swelling the coal samples with various solvents. Stable nitroxide radical spin probes of different sizes, shapes and reactivity are dissolved in an appropriate solvent, the coal sample is added to the resulting solution, stirred over night at elevated temperature, filtered, washed with a non swelling solvent to eliminate any spin probes that are not trapped in the pores and the spin concentration is measured. Comparing these spin probe measurements to DRIFT data have shown that the relative number distribution of acidic functionalities can be accurately predicted by the spin probe method. The spin probe method had also been used to predict the increase in elongated voids in Pittsburgh No. 8 (APCS No. 4) upon swelling with pyridine in agreement with independent SANS data. NMR relaxation data show that it is possible to deduce the pore (accessibility) distribution as a function of size (up to 6 mn). It has also been possible by variable temperature and ENDOR measurements to determine the presence of hydrogen bonding as a function of pore shape and size. The advantage of the EPR method is that it permits molecules of selected shape and size to be used as probes of accessible regions of coal, thus providing information on the importance of molecular shape.

  18. Voids in a neutrino-dominated universe

    NASA Technical Reports Server (NTRS)

    Zeng, Ning; White, Simon D. M.

    1991-01-01

    In a neutrino-dominated universe, galaxies are expected to form only in large-scale sheets and filaments. Most of space should be filled by low-density regions devoid of galaxies. In this paper, N-body simulations are used to estimate the size distribution for these regions for quantitative comparison with the observed voids in recent red-shift surveys. The theoretical distribution depends very weakly on the mode or epoch of galaxy formation. With very conservative assumptions, at best marginal consistency is found even for cosmological parameters as extreme as Omega(v) = 1 and H(0) = 100 km/s per/Mpc. Any significant reduction in either H(0) or Omega(v) leads to predicted void sizes much larger than those observed. This difficulty arises because the observed voids are rarely completely empty.

  19. Hotspot swells revisited

    NASA Astrophysics Data System (ADS)

    King, Scott D.; Adam, Claudia

    2014-10-01

    The first attempts to quantify the width and height of hotspot swells were made more than 30 years ago. Since that time, topography, ocean-floor age, and sediment thickness datasets have improved considerably. Swell heights and widths have been used to estimate the heat flow from the core-mantle boundary, constrain numerical models of plumes, and as an indicator of the origin of hotspots. In this paper, we repeat the analysis of swell geometry and buoyancy flux for 54 hotspots, including the 37 considered by Sleep (1990) and the 49 considered by Courtillot et al. (2003), using the latest and most accurate data. We are able to calculate swell geometry for a number of hotspots that Sleep was only able to estimate by comparison with other swells. We find that in spite of the increased resolution in global bathymetry models there is significant uncertainty in our calculation of buoyancy fluxes due to differences in our measurement of the swells’ width and height, the integration method (volume integration or cross-sectional area), and the variations of the plate velocities between HS2-Nuvel1a (Gripp and Gordon, 1990) and HS3-Nuvel1a (Gripp and Gordon, 2002). We also note that the buoyancy flux for Pacific hotspots is in general larger than for Eurasian, North American, African and Antarctic hotspots. Considering that buoyancy flux is linearly related to plate velocity, we speculate that either the calculation of buoyancy flux using plate velocity over-estimates the actual vertical flow of material from the deep mantle or that convection in the Pacific hemisphere is more vigorous than the Atlantic hemisphere.

  20. Stress-enhanced swelling of metal during irradiation

    SciTech Connect

    Garner, F.A.; Gilbert, E.R.; Porter, D.L.

    1980-04-01

    Data are available which show that stress plays a major role in the development of radiation-induced void growth in AISI 316 and many other alloys. Earlier experiments came to the opposite conclusion and are shown to have investigated stress levels which inadvertantly cold-worked the material. Stress-affected swelling spans the entire temperature range in fast reactor irradiations and accelerates with increasing irradiatin temperature. It also appears to operate in all alloy starting conditions investigated. Two major microstructural mechanisms appear to be causing the enhancement of swelling, which for tensile stresses is manifested primarily as a decrease in the incubation period. These mechanisms are stress-induced changes in the interstitial capture efficiency of voids and stress-induced changes in the vacancy emission rate of various microstructural components. There also appears to be an enhancement of intermetallic phase formation with applied stress and this is shown to increase swelling by accelerating the microchemical evolution that precedes void growth at high temperature. This latter consideration complicates the extrapolation of these data to compressive stress states.

  1. Stress Voiding During Wafer Processing

    SciTech Connect

    Yost, F.G.

    1999-03-01

    Wafer processing involves several heating cycles to temperatures as high as 400 C. These thermal excursions are known to cause growth of voids that limit reliability of parts cut from the wafer. A model for void growth is constructed that can simulate the effect of these thermal cycles on void growth. The model is solved for typical process steps and the kinetics and extent of void growth are determined for each. It is shown that grain size, void spacing, and conductor line width are very important in determining void and stress behavior. For small grain sizes, stress relaxation can be rapid and can lead to void shrinkage during subsequent heating cycles. The effect of rapid quenching from process temperatures is to suppress void growth but induce large remnant stress in the conductor line. This stress can provide the driving force for void growth during storage even at room temperature. For isothermal processes the model can be solved analytically and estimates of terminal void size a nd lifetime are obtained.

  2. Radiation-induced formation, annealing and ordering of voids in crystals: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Dubinko, V. I.; Guglya, A. G.; Donnelly, S. E.

    2011-07-01

    Void ordering has been observed in very different radiation environments ranging from metals to ionic crystals bombarded with energetic particles. The void ordering is often accompanied by a saturation of the void swelling with increasing irradiation dose, which makes an understanding of the underlying mechanisms to be both of scientific significance and of practical importance for nuclear engineering. We show that both phenomena can be explained by the original mechanism based on the anisotropic energy transfer provided by self-focusing discrete breathers or quodons (energetic, mobile, highly localized lattice solitons that propagate great distances along close-packed crystal directions). The interaction of quodons with voids can result in radiation-induced “annealing” of selected voids, which results in the void ordering under special irradiation conditions. We observe experimentally radiation-induced void annealing by lowering the irradiation temperature of nickel and copper samples pre-irradiated to produce voids or gas bubbles. The bulk recombination of Frenkel pairs increases with decreasing temperature resulting in suppression of the production of freely migrating vacancies (the driving force of the void growth). On the other hand, the rate of radiation-induced vacancy emission from voids due to the void interaction with quodons remains essentially unchanged, which results in void dissolution. The experimental data on the void shrinkage and void lattice formation obtained for different metals and irradiating particles are explained by the present model assuming the quodon propagation length to be in the micron range, which is consistent with independent data on the irradiation-induced diffusion of interstitial ions in austenitic stainless steel.

  3. Climatology of Global Swell-Atmosphere Interaction

    NASA Astrophysics Data System (ADS)

    Semedo, Alvaro

    2016-04-01

    At the ocean surface wind sea and swell waves coexist. Wind sea waves are locally generated growing waves strongly linked to the overlaying wind field. Waves that propagate away from their generation area, throughout entire ocean basins, are called swell. Swell waves do not receive energy from local wind. Ocean wind waves can be seen as the "gearbox" between the atmosphere and the ocean, and are of critical importance to the coupled atmosphere-ocean system, since they modulate most of the air-sea interaction processes and exchanges, particularly the exchange of momentum. This modulation is most of the times sea-state dependent, i.e., it is a function of the prevalence of one type of waves over the other. The wave age parameter, defined as the relative speed between the peak wave and the wind (c_p⁄U_10), has been largely used in different aspects of the air-sea interaction theory and in practical modeling solutions of wave-atmosphere coupled model systems. The wave age can be used to assess the development of the sea state but also the prevalence (domination) of wind sea or swell waves at the ocean surface. The presence of fast-running waves (swell) during light winds (at high wave age regimes) induces an upward momentum flux, directed from the water surface to the atmosphere. This upward directed momentum has an impact in the lower marine atmospheric boundary layer (MABL): on the one hand it changes the vertical wind speed profile by accelerating the flow at the first few meters (inducing the so called "wave-driven wind"), and on the other hand it changes the overall MABL turbulence structure by limiting the wind shear - in some observed and modeled situations the turbulence is said to have "collapse". The swell interaction with the lower MABL is a function of the wave age but also of the swell steepness, since steeper waves loose more energy into the atmosphere as their energy attenuates. This interaction can be seen as highest in areas where swells are steepest

  4. Mitosis is swell.

    PubMed

    Zatulovskiy, Evgeny; Skotheim, Jan M

    2015-11-23

    Cell volume and dry mass are typically correlated. However, in this issue, Zlotek-Zlotkiewicz et al. (2015. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201505056) and Son et al. (2015. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201505058) use new live-cell techniques to show that entry to mitosis coincides with rapid cell swelling, which is reversed before division.

  5. Mitosis is swell

    PubMed Central

    Zatulovskiy, Evgeny

    2015-01-01

    Cell volume and dry mass are typically correlated. However, in this issue, Zlotek-Zlotkiewicz et al. (2015. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201505056) and Son et al. (2015. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201505058) use new live-cell techniques to show that entry to mitosis coincides with rapid cell swelling, which is reversed before division. PMID:26598610

  6. Measuring baryon acoustic oscillations from the clustering of voids

    NASA Astrophysics Data System (ADS)

    Liang, Yu; Zhao, Cheng; Chuang, Chia-Hsun; Kitaura, Francisco-Shu; Tao, Charling

    2016-07-01

    We investigate the necessary methodology to optimally measure the baryon acoustic oscillation (BAO) signal from voids, based on galaxy redshift catalogues. To this end, we study the dependence of the BAO signal on the population of voids classified by their sizes. We find for the first time the characteristic features of the correlation function of voids including the first robust detection of BAOs in mock galaxy catalogues. These show an anti-correlation around the scale corresponding to the smallest size of voids in the sample (the void exclusion effect), and dips at both sides of the BAO peak, which can be used to determine the significance of the BAO signal without any priori model. Furthermore, our analysis demonstrates that there is a scale-dependent bias for different populations of voids depending on the radius, with the peculiar property that the void population with the largest BAO significance corresponds to tracers with approximately zero bias on the largest scales. We further investigate the methodology on an additional set of 1000 realistic mock galaxy catalogues reproducing the SDSS-III/BOSS CMASS DR11 data, to control the impact of sky mask and radial selection function. Our solution is based on generating voids from randoms including the same survey geometry and completeness, and a post-processing cleaning procedure in the holes and at the boundaries of the survey. The methodology and optimal selection of void populations validated in this work have been used to perform the first BAO detection from voids in observations, presented in a companion paper.

  7. Void detecting device

    DOEpatents

    Nakamoto, Koichiro; Ohyama, Nobumi; Adachi, Kiyoshi; Kuwahara, Hajime

    1979-01-01

    A detector to be inserted into a flowing conductive fluid, e.g. sodium coolant in a nuclear reactor, comprising at least one exciting coil to receive an a-c signal applied thereto and two detecting coils located in the proximity of the exciting coil. The difference and/or the sum of the output signals of the detecting coils is computed to produce a flow velocity signal and/or a temperature-responsive signal for the fluid. Such flow velocity signal or temperature signal is rectified synchronously by a signal the phase of which is shifted substantially .+-. 90.degree. with respect to the flow velocity signal or temperature signal, thereby enabling the device to detect voids in the flowing fluid without adverse effects from flow velocity variations or flow disturbances occurring in the fluid.

  8. Voids in massive neutrino cosmologies

    SciTech Connect

    Massara, Elena; Villaescusa-Navarro, Francisco; Viel, Matteo; Sutter, P.M. E-mail: villaescusa@oats.inaf.it E-mail: sutter@oats.inaf.it

    2015-11-01

    Cosmic voids are a promising environment to characterize neutrino-induced effects on the large-scale distribution of matter in the universe. We perform a comprehensive numerical study of the statistical properties of voids, identified both in the matter and galaxy distributions, in massive and massless neutrino cosmologies. The matter density field is obtained by running several independent N-body simulations with cold dark matter and neutrino particles, while the galaxy catalogs are modeled by populating the dark matter halos in simulations via a halo occupation distribution (HOD) model to reproduce the clustering properties observed by the Sloan Digital Sky Survey (SDSS) II Data Release 7. We focus on the impact of massive neutrinos on the following void statistical properties: number density, ellipticities, two-point statistics, density and velocity profiles. Considering the matter density field, we find that voids in massive neutrino cosmologies are less evolved than those in the corresponding massless neutrinos case: there is a larger number of small voids and a smaller number of large ones, their profiles are less evacuated, and they present a lower wall at the edge. Moreover, the degeneracy between σ{sub 8} and Ω{sub ν} is broken when looking at void properties. In terms of the galaxy density field, we find that differences among cosmologies are difficult to detect because of the small number of galaxy voids in the simulations. Differences are instead present when looking at the matter density and velocity profiles around these voids.

  9. Molecular accessibility in solvent swelled coal

    SciTech Connect

    Kispert, L.D.

    1992-05-29

    An EPR technique developed in this lab is being used to determine the pore size and number distribution changes after swelling the coal samples with various solvents. Stable nitroxide radical spin probes of different sizes, shapes and reactivity are dissolved in an appropriate solvent, the coal sample is added to the resulting solution, stirred over night at elevated temperature, filtered, washed with a nonswelling solvent to eliminate any spin probes that are not trapped in the pores and the spin concentration measured. Comparing these spin probe measurements to DRIFT data have shown that the relative number distribution of acidic functionalities can be accurately predicted by the spin probe method. The spin probe method has also been used to predict the increase in elongated voids in Pittsburgh No. 8 (APCS No. 4) upon swelling with pyridine in agreement with independent SANS data. NMR relaxation data show that it is possible to deduce the pore (accessibility) distribution as a function of size (up to 6 nm). It has also been possible by variable temperature and ENDOR measurements to determine the presence of hydrogen bonding as a function of pore shape and size. The advantage of EPR method is that it permits molecules of selected shape and size to be used as probes of accessible regions of the coal, thus providing information on the importance of molecular shape.

  10. Molecular accessibility in solvent swelled coal

    SciTech Connect

    Kispert, L.D.

    1992-08-01

    An EPR technique developed in this lab is being used to determine the pore size and number distribution changes after swelling the coal samples with various solvents. Stable nitroxide radical spin probes of different sizes, shapes and reactivity are dissolved in an appropriate solvent, the coal sample is added to the resulting solution, stirred over night at elevated temperature, filtered, washed with a nonswelling solvent to eliminate any spin probes that are not trapped in the pores and the spin concentration measured. Comparing these spin probe measurements to DRIFT data have shown that the relative number distribution of acidic functionalities can be accurately predicted by the spin probe method. The spin probe method has also been used to predict the increase in elongated voids in Pittsburgh No. 8 (APCS No. 4) upon swelling with pyridine in agreement with independent SANS data. NMR relaxation data shows that it is possible to deduce the pore (accessibility) distribution as a function of size (up to 6 nm). It has also been possible by variable temperature and ENDOR measurements to determine the presence of hydrogen bonding as a function of pore shape and size. The advantage of the EPR method is that it permits molecules of selected shape and size to be used as probes of accessible regions of the coal, thus providing information on the importance of molecular shape.

  11. Effects of surface energy anisotropy on void evolution during irradiation: A phase-field model

    NASA Astrophysics Data System (ADS)

    Liu, W. B.; Wang, N.; Ji, Y. Z.; Song, P. C.; Zhang, C.; Yang, Z. G.; Chen, L. Q.

    2016-10-01

    A phase-field model is employed to investigate the effects of surface energy anisotropy on void evolution during irradiation. By incorporating a simple orientation dependent surface energy with sharp cusps on given crystallographic orientations, experimentally observed void shape with facets and rounded corners is captured. When applied to polycrystalline materials, grain dependent void morphologies are predicted, and the simulation results are qualitatively similar to reported void morphologies in irradiated copper. In addition, the formation of void denuded zones and vacancy depleted zones adjacent to the grain boundaries (GBs) in bicrystalline and polycrystalline structures are studied.

  12. Voids in modified gravity reloaded: Eulerian void assignment

    NASA Astrophysics Data System (ADS)

    Lam, Tsz Yan; Clampitt, Joseph; Cai, Yan-Chuan; Li, Baojiu

    2015-07-01

    We revisit the excursion set approach to calculate void abundances in chameleon-type modified gravity theories, which was previously studied by Clampitt, Cai & Li. We focus on properly accounting for the void-in-cloud effect, i.e. the growth of those voids sitting in overdense regions may be restricted by the evolution of their surroundings. This effect may change the distribution function of voids hence affect predictions on the differences between modified gravity (MG) and general relativity (GR). We show that the thin-shell approximation usually used to calculate the fifth force is qualitatively good but quantitatively inaccurate. Therefore, it is necessary to numerically solve the fifth force in both overdense and underdense regions. We then generalize the Eulerian-void-assignment method of Paranjape, Lam & Sheth to our modified gravity model. We implement this method in our Monte Carlo simulations and compare its results with the original Lagrangian methods. We find that the abundances of small voids are significantly reduced in both MG and GR due to the restriction of environments. However, the change in void abundances for the range of void radii of interest for both models is similar. Therefore, the difference between models remains similar to the results from the Lagrangian method, especially if correlated steps of the random walks are used. As Clampitt et al., we find that the void abundance is much more sensitive to MG than halo abundances. Our method can then be a faster alternative to N-body simulations for studying the qualitative behaviour of a broad class of theories. We also discuss the limitations and other practical issues associated with its applications.

  13. Prediction of swelling of 18Cr10NiTi austenitic steel over a wide range of displacement rates

    NASA Astrophysics Data System (ADS)

    Kalchenko, A. S.; Bryk, V. V.; Lazarev, N. P.; Neklyudov, I. M.; Voyevodin, V. N.; Garner, F. A.

    2010-04-01

    The internal components of pressurized water reactors of Russian types WWER-440 and WWER-1000 are constructed of annealed 18Cr10NiTi steel, a close analog to AISI 321. Void swelling of the internals is a concern for plant life extension and predictive equations are required to assess the potential of swelling in critical components such as the baffle ring or reflection shield that surrounds the WWER core. The only previously available swelling data for this steel were derived at higher than PWR-relevant displacement rates in the BOR-60 fast reactor. The swelling equation previously developed from these data does not incorporate the effect of displacement rate on swelling. Using heavy-ion irradiation at very high dpa rates (10 -2 and 10 -3 dpa s -1) and doses (5-100 dpa) and coupling the results to available neutron data a swelling equation has been developed that specifically incorporates the effect of dpa rate on void swelling. Experimental results allow description of the swelling peak, the incubation period and the steady-state swelling rate over a wide range of irradiation temperature. For the first time it appears possible to describe both ion and neutron data on this steel within the framework of a single empirical model. Swelling maps constructed from this model permit forecasting of the behavior of the steel in WWERs under the required irradiation conditions, not only at already attained exposure doses, but more importantly to higher dose levels that will be reached following plant life extension.

  14. On nonlinear excitation of voids in dusty plasmas

    SciTech Connect

    Nebbat, E.; Annou, R.; Bharuthram, R.

    2007-09-15

    The void, which is a dust-free region inside the dust cloud in the plasma, results from a balance of the electrostatic force and the ion-drag force on a dust particulate that has numerous forms, some of which are based on models whereas others are driven from first principles. To explain the generation of voids, K. Avinash, A. Bhattacharjee, and S. Hu [Phys. Rev. Lett. 90, 075001 (2003)] proposed a time-dependent nonlinear model that describes the void as a result of an instability. We augment this model by incorporating the grain drift and reintroducing the velocity convective term as well as by replacing the modeled ion-drag force by a more accurate one. The analysis is conducted in a spherical configuration. It is revealed that the void formation is a threshold phenomenon, i.e., it depends on the grain size. Furthermore, the void possesses a sharp boundary beyond which the dust density decreases and may present a corrugated aspect. For big size grains, the use of both ion-drag forces leads to voids of the same dimension, though for grains of small sizes, the Avinash force drives voids of a higher dimension. The model shows good agreement with the experiment.

  15. Testing Gravity using Void Profiles

    NASA Astrophysics Data System (ADS)

    Cai, Yan-Chuan; Padilla, Nelson; Li, Baojiu

    2016-10-01

    We investigate void properties in f(R) models using N-body simulations, focusing on their differences from General Relativity (GR) and their detectability. In the Hu-Sawicki f(R) modified gravity (MG) models, the halo number density profiles of voids are not distinguishable from GR. In contrast, the same f(R) voids are more empty of dark matter, and their profiles are steeper. This can in principle be observed by weak gravitational lensing of voids, for which the combination of a spectroscopic redshift and a lensing photometric redshift survey over the same sky is required. Neglecting the lensing shape noise, the f(R) model parameter amplitudes fR0=10-5 and 10-4 may be distinguished from GR using the lensing tangential shear signal around voids by 4 and 8 σ for a volume of 1 (Gpc/h)3. The line-of-sight projection of large-scale structure is the main systematics that limits the significance of this signal for the near future wide angle and deep lensing surveys. For this reason, it is challenging to distinguish fR0=10-6 from GR. We expect that this can be overcome with larger volume. The halo void abundance being smaller and the steepening of dark matter void profiles in f(R) models are unique features that can be combined to break the degeneracy between fR0 and σ8.

  16. Void formation in amorphous germanium due to high electronic energy deposition

    SciTech Connect

    Gaertner, K.; Joehrens, J.; Steinbach, T.; Schnohr, C. S.; Wesch, W.; Ridgway, M. C.

    2011-06-01

    The effect of high electronic energy deposition in amorphous germanium has been studied experimentally by Au irradiation with ion energies of up to 185 MeV and different angles of incidence and by molecular dynamics computer simulations. In both cases, the energy deposition leads to void formation accompanied by strong swelling of the amorphous germanium. The simulation results prove that the formation of the voids is mainly based on a shock wave mechanism and the swelling is determined by the competing processes of the formation and growth of voids on the one hand and the shrinking and annihilation of voids on the other hand. In full agreement between experiment and simulation, the amount of the swelling is a linear function of the total energy deposited into electronic processes and there exists a threshold value of the electronic energy loss per ion and depth for swelling. A comparison of the threshold values obtained by the experiment and the simulation suggests that approximately 20% of the energy deposited into electronic processes is converted into atomic motion.

  17. PRECISION COSMOGRAPHY WITH STACKED VOIDS

    SciTech Connect

    Lavaux, Guilhem; Wandelt, Benjamin D.

    2012-08-01

    We present a purely geometrical method for probing the expansion history of the universe from the observation of the shape of stacked voids in spectroscopic redshift surveys. Our method is an Alcock-Paczynski (AP) test based on the average sphericity of voids posited on the local isotropy of the universe. It works by comparing the temporal extent of cosmic voids along the line of sight with their angular, spatial extent. We describe the algorithm that we use to detect and stack voids in redshift shells on the light cone and test it on mock light cones produced from N-body simulations. We establish a robust statistical model for estimating the average stretching of voids in redshift space and quantify the contamination by peculiar velocities. Finally, assuming that the void statistics that we derive from N-body simulations is preserved when considering galaxy surveys, we assess the capability of this approach to constrain dark energy parameters. We report this assessment in terms of the figure of merit (FoM) of the dark energy task force and in particular of the proposed Euclid mission which is particularly suited for this technique since it is a spectroscopic survey. The FoM due to stacked voids from the Euclid wide survey may double that of all other dark energy probes derived from Euclid data alone (combined with Planck priors). In particular, voids seem to outperform baryon acoustic oscillations by an order of magnitude. This result is consistent with simple estimates based on mode counting. The AP test based on stacked voids may be a significant addition to the portfolio of major dark energy probes and its potentialities must be studied in detail.

  18. Comparison of swelling and cavity microstructural development for type 316 stainless steel irradiated in EBR-II and HFIR

    SciTech Connect

    Maziasz, P.J.

    1983-01-01

    Comparison of swelling and cavity microstructures for one heat of 20% cold-worked (CW) type 316 stainless steel (316) irradiated at 500 to 650/sup 0/C in EBR-II (up to 75 dpa) and HFIR (up to 61 dpa) suggests that void growth and swelling are suppressed by the higher helium generation found in HFIR. Instead of voids, many small bubbles develop in the CW 316 in HFIR and resist conversion to voids. However, similar comparison of solution-annealed (SA) 316 irradiated in EBR-II and HFIR at 500 to 550/sup 0/C leads to an opposite conclusion; void swelling is enhanced by helium in HFIR. Many more bubbles nucleate in SA 316 at low fluence in HFIR compared to EBR-II, but bimodel distributions and rapid coarsening eventually lead to high swelling due to high concentrations of matrix ands precipitate-associated voids in HFIR. A key to the swelling resistance of the CW 316 in HFIR appears to be the development of a sufficiently cavity-dominated sink system in the early stages of evolution.

  19. Self-similarity and universality of void density profiles in simulation and SDSS data

    NASA Astrophysics Data System (ADS)

    Nadathur, S.; Hotchkiss, S.; Diego, J. M.; Iliev, I. T.; Gottlöber, S.; Watson, W. A.; Yepes, G.

    2015-06-01

    The stacked density profile of cosmic voids in the galaxy distribution provides an important tool for the use of voids for precision cosmology. We study the density profiles of voids identified using the ZOBOV watershed transform algorithm in realistic mock luminous red galaxy (LRG) catalogues from the Jubilee simulation, as well as in void catalogues constructed from the SDSS LRG and Main Galaxy samples. We compare different methods for reconstructing density profiles scaled by the void radius and show that the most commonly used method based on counts in shells and simple averaging is statistically flawed as it underestimates the density in void interiors. We provide two alternative methods that do not suffer from this effect; one based on Voronoi tessellations is also easily able to account from artefacts due to finite survey boundaries and so is more suitable when comparing simulation data to observation. Using this method, we show that the most robust voids in simulation are exactly self-similar, meaning that their average rescaled profile does not depend on the void size. Within the range of our simulation, we also find no redshift dependence of the mean profile. Comparison of the profiles obtained from simulated and real voids shows an excellent match. The mean profiles of real voids also show a universal behaviour over a wide range of galaxy luminosities, number densities and redshifts. This points to a fundamental property of the voids found by the watershed algorithm, which can be exploited in future studies of voids.

  20. Testing Gravity using Cosmic Voids

    NASA Astrophysics Data System (ADS)

    Falck, Bridget

    2016-01-01

    Though general relativity is well-tested on small (Solar System) scales, the late-time acceleration of the Universe provides strong motivation to test GR on cosmological scales. The difference between the small and large scale behavior of gravity is determined by the screening mechanism in modified gravity theories. Dark matter halos are often screened in these models, especially in models with Vainshtein screening, motivating a search for signatures of modified gravity in cosmic voids. We explore density, force, and velocity profiles of voids found in N-body simulations, using both dark matter particles and dark matter halos to identify the voids. The prospect of testing gravity using cosmic voids may be limited by the sparsity of halos as tracers of the density field.

  1. The spreading of a void on a facet during electromigration

    SciTech Connect

    Chu, X.; Bauer, C.L.; Mullins, W.W.; Klinger, L.M.

    1997-07-01

    A void of cross sectional area A may spread perpendicular to the applied electric field E{sub a} during electromigration because its leading surface develops a facet whose advance is limited by the supply of steps. If the facet is immobile (no step source) and the remaining surface is free to move, and if E{sub a}A is less than a threshold value, then the void assumes a stationary elongated shape dictated by a balance between capillarity and electric field. If E{sub a}A exceeds the threshold value, however, a balance is no longer possible, and the void spreads along the facet without arrest. If the facet has limited mobility, a balance is possible for all values of E{sub a}A, resulting in an elongated moving steady-state shape. The treatment simplifies the void shape as rectangular but preserves the essential features of capillarity and surface electromigration. The authors argue that the motion of a facet on a void along the outward normal requires defects (e.g., intersecting screw dislocations) that act as step sources since homogeneous nucleation of steps on the facet is expected to be negligible. Since voids in fine-line interconnects are often observed to be partially faceted, restricted void motion and resultant spreading which depend sensitively on crystallographic features, such as defect structure and grain orientation, may indeed limit the lifetime of fine-line interconnects in electronic devices.

  2. NMR imaging and cryoporometry of swelling clays

    NASA Astrophysics Data System (ADS)

    Dvinskikh, Sergey V.; Szutkowski, Kosma; Petrov, Oleg V.; Furó, István.

    2010-05-01

    Compacted bentonite clay is currently attracting attention as a promising "self-sealing" buffer material to build in-ground barriers for the encapsulation of radioactive waste. It is expected to fill up the space between waste canister and surrounding ground by swelling and thus delay flow and migration from the host rock to the canister. In environmental sciences, evaluation and understanding of the swelling properties of pre-compacted clay are of uttermost importance for designing such buffers. Major goal of present study was to provide, in a non-invasive manner, a quantitative measure of bentonite distribution in extended samples during different physical processes in an aqueous environment such as swelling, dissolution, and sedimentation on the time scale from minutes to years. The propagation of the swelling front during clay expansion depending on the geometry of the confining space was also studied. Magnetic resonance imaging and nuclear magnetic resonance spectroscopy were adapted and used as main experimental techniques. With this approach, spatially resolved movement of the clay/water interface as well as clay particle distributions in gel phase can be monitored [1]. Bulk samples with swelling in a vertical tube and in a horizontal channel were investigated and clay content distribution profiles in the concentration range over five orders of magnitude and with sub-millimetre spatial resolution were obtained. Expansion rates for bulk swelling and swelling in narrow slits were compared. For sodium-exchanged montmorillonite in contact with de-ionised water, we observed a remarkable acceleration of expansion as compared to that obtained in the bulk. To characterize the porosity of the clay a cryoporometric study [2] has been performed. Our results have important implications to waste repository designs and for the assessment of its long-term performance. Further research exploring clay-water interaction over a wide variety of clay composition and water ionic

  3. The Swelling of Olympic Gels

    NASA Astrophysics Data System (ADS)

    Lang, Michael; Fischer, Jakob; Werner, Marco; Sommer, Jens-Uwe

    2014-03-01

    The swelling equilibrium of Olympic gels is studied by Monte Carlo Simulations. We observe that gels consisting of flexible cyclic molecules of a higher degree of polymerization N show a smaller equilibrium swelling degree Q ~N - 0 . 28φ0- 0 . 72 for the same monomer volume fraction φ0 at network preparation. This observation is explained by a disinterpenetration process of overlapping non-concatenated polymers upon swelling. In the limit of a sufficiently large number of concatenations per cyclic molecule we expect that the equilibrium degree of swelling becomes proportional to φ0- 1 / 2 independent of N. Our results challenge current textbook models for the equilibrium degree of swelling of entangled polymer networks. Now at: Bio Systems Analysis Group, Jena Centre for Bioinformatics (JCB) and Department for Mathematics and Computer Sciences, Friedrich Schiller University of Jena, 07743 Jena, Germany.

  4. Displacement damage rate dependence of defect cluster formation in α-Fe during irradiation

    NASA Astrophysics Data System (ADS)

    Watanabe, Y.; Morishita, K.; Yamamoto, Y.; Hamaguchi, D.; Tanigawa, H.

    2013-05-01

    Formation kinetics of defect clusters in pure iron during irradiation has been numerically investigated by reaction rate theory, with focusing on nucleation process of vacancy clusters (voids) and self-interstitial-atoms (SIA) clusters under a wide range of atomic displacement damage rate (dpa rate) and temperature conditions. In the rate theory model, the size dependence of thermal stability of a defect cluster is treated for a wide range of cluster size. The numerical analysis shows that the nucleation processes of voids and SIA-clusters are quite different from each other. As to the voids, the nucleation rate of voids depends much on temperature and dpa rate, and has the individual peak temperature for each dpa rate, during which the peak temperature increases with increasing dpa rate. This tendency for void nucleation is similar to that for void swelling observed in experiments. As to the SIA-clusters, the nucleation rate of SIA-clusters does not depend much on temperature and has no peak temperatures because of the relatively high thermal stability of an SIA-cluster, indicating that the conventional model (di-interstitial model) is applicable to describe the nucleation of SIA-clusters in a wide range of temperature.

  5. The life and death of cosmic voids

    NASA Astrophysics Data System (ADS)

    Sutter, P. M.; Elahi, Pascal; Falck, Bridget; Onions, Julian; Hamaus, Nico; Knebe, Alexander; Srisawat, Chaichalit; Schneider, Aurel

    2014-12-01

    We investigate the formation, growth, merger history, movement, and destruction of cosmic voids detected via the watershed transform code VIDE in a cosmological N-body dark matter Λ cold dark matter simulation. By adapting a method used to construct halo merger trees, we are able to trace individual voids back to their initial appearance and record the merging and evolution of their progenitors at high redshift. For the scales of void sizes captured in our simulation, we find that the void formation rate peaks at scale factor 0.3, which coincides with a growth in the void hierarchy and the emergence of dark energy. Voids of all sizes appear at all scale factors, though the median initial void size decreases with time. When voids become detectable they have nearly their present-day volumes. Almost all voids have relatively stable growth rates and suffer only infrequent minor mergers. Dissolution of a void via merging is very rare. Instead, most voids maintain their distinct identity as annexed subvoids of a larger parent. The smallest voids are collapsing at the present epoch, but void destruction ceases after scale factor 0.3. In addition, voids centres tend to move very little, less than 10-2 of their effective radii per ln a, over their lifetimes. Overall, most voids exhibit little radical dynamical evolution; their quiet lives make them pristine probes of cosmological initial conditions and the imprint of dark energy.

  6. Effects of Stress and Void-Void Interactions on Current-Driven Void Surface Evolution in Metallic Thin Films

    NASA Astrophysics Data System (ADS)

    Cho, Jaeseol; Gungor, M. Rauf; Maroudas, Dimitrios

    2006-03-01

    We report results of electromigration- and stress-induced migration and morphological evolution of voids in metallic thin films based on self-consistent numerical simulations. The analysis reveals the complex nature of void-void interactions and their implications for the evolution of metallic thin-film electrical resistance, providing interpretation for experimental measurements in interconnect lines. Interestingly, for two voids migrating in the same direction under certain conditions, we find that a smaller void does not always approach and coalesce with a larger one, while a larger void may approach and coalesce with a smaller one. In addition, we find that under certain electromechanical conditions, biaxially applied mechanical stress can cause substantial retardation of void motion, as measured by the constant speed of electromigration-induced translation of morphologically stable voids. This effect suggests the possibility for complete inhibition of current-driven void motion under stress.

  7. Growth of voids in porous ductile materials at high strain rate

    NASA Astrophysics Data System (ADS)

    Wang, Ze-Ping

    1994-08-01

    A hollow-sphere model, with temperature-dependent viscoplastic material response, is developed to investigate the inertial and thermal effects on dynamic growth of voids in ductile materials. Theoretical analysis indicates that the inertial effect (kinetic energy of void growth) mainly dominates the behavoir of the void growth in temperature-dependent and high-strain-rate cases. Otherwise, the viscoplastic effect dominanes and the inertial effect can be negelcted. The rate of the dyanmic growth of voids increases when the thermal effect is considered. An expression of the threshold stress for the void growth is obtained, which depends on the initial porosity, the porosity, the yield strength, the density of surface energy of voids, the initial temperature, and the melting temperature.

  8. Swelling equilibria for cationic 2-hydroxyethyl methacrylate (HEMA)-based hydrogels

    SciTech Connect

    Baker, J.P.; Blanch, H.W.; Prausnitz, J.M.

    1993-08-01

    Cationic HEMA-based hydrogels were synthesized by copolymerizing HEMA with [(methacrylamido)propyl]trimethylammonium chloride (MAPTAC). Swelling equilibria were measured in pure water an in aqueous sodium chloride solutions. Hydrogel swelling is an increasing function of the MAPTAC content. A Flory-type swelling model using a concentration-dependent Flory {Chi} parameter semi-qualitatively describes poly(HEMA co-MAPTAC) hydrogel swelling in aqueous sodium chloride.

  9. Theoretical analysis of electromigration-induced failure of metallic thin films due to transgranular void propagation

    SciTech Connect

    Gungor, M.R.; Maroudas, D.

    1999-02-01

    Failure of metallic thin films driven by electromigration is among the most challenging materials reliability problems in microelectronics toward ultra-large-scale integration. One of the most serious failure mechanisms in thin films with bamboo grain structure is the propagation of transgranular voids, which may lead to open-circuit failure. In this article, a comprehensive theoretical analysis is presented of the complex nonlinear dynamics of transgranular voids in metallic thin films as determined by capillarity-driven surface diffusion coupled with drift induced by electromigration. Our analysis is based on self-consistent dynamical simulations of void morphological evolution and it is aided by the conclusions of an approximate linear stability theory. Our simulations emphasize that the strong dependence of surface diffusivity on void surface orientation, the strength of the applied electric field, and the void size play important roles in the dynamics of the voids. The simulations predict void faceting, formation of wedge-shaped voids due to facet selection, propagation of slit-like features emanating from void surfaces, open-circuit failure due to slit propagation, as well as appearance and disappearance of soliton-like features on void surfaces prior to failure. These predictions are in very good agreement with recent experimental observations during accelerated electromigration testing of unpassivated metallic films. The simulation results are used to establish conditions for the formation of various void morphological features and discuss their serious implications for interconnect reliability. {copyright} {ital 1999 American Institute of Physics.}

  10. Void Growth in Single and Bicrystalline Metals: Atomistic Calculations

    NASA Astrophysics Data System (ADS)

    Traiviratana, Sirirat; Bringa, Eduardo M.; Benson, David J.; Meyers, Marc A.

    2007-12-01

    MD simulations in monocrystalline and bicrystalline copper were carried out with LAMMPS to reveal void growth mechanisms. The specimens were subjected to both tensile uniaxial and hydrostatic strains; the results confirm that the emission of (shear) loops is the primary mechanism of void growth. However, these shear loops develop along two slip planes (and not one, as previously thought), in a heretofore unidentified mechanism of cooperative growth. The emission of dislocations from voids is the first stage, and their reaction and interaction is the second stage. These loops, forming initially on different {111} planes, join at the intersection, the Burgers vector of the dislocations being parallel to the intersection of two {111} planes: a <110> direction. Thus, the two dislocations cancel at the intersection and a biplanar shear loop is formed. The expansion of the loops and their cross slip leads to the severely work hardened layer surrounding a growing void. Calculations were carried out on voids with different sizes, and a size dependence of the stress response to emitted dislocations was observed, in disagreement with the Gurson model[1] which is scale independent. Calculations were also carried out for a void at the interface between two grains.

  11. Swelling in light water reactor internal components: Insights from computational modeling

    SciTech Connect

    Stoller, Roger E.; Barashev, Alexander V.; Golubov, Stanislav I.

    2015-08-01

    A modern cluster dynamics model has been used to investigate the materials and irradiation parameters that control microstructural evolution under the relatively low-temperature exposure conditions that are representative of the operating environment for in-core light water reactor components. The focus is on components fabricated from austenitic stainless steel. The model accounts for the synergistic interaction between radiation-produced vacancies and the helium that is produced by nuclear transmutation reactions. Cavity nucleation rates are shown to be relatively high in this temperature regime (275 to 325°C), but are sensitive to assumptions about the fine scale microstructure produced under low-temperature irradiation. The cavity nucleation rates observed run counter to the expectation that void swelling would not occur under these conditions. This expectation was based on previous research on void swelling in austenitic steels in fast reactors. This misleading impression arose primarily from an absence of relevant data. The results of the computational modeling are generally consistent with recent data obtained by examining ex-service components. However, it has been shown that the sensitivity of the model s predictions of low-temperature swelling behavior to assumptions about the primary damage source term and specification of the mean-field sink strengths is somewhat greater that that observed at higher temperatures. Further assessment of the mathematical model is underway to meet the long-term objective of this research, which is to provide a predictive model of void swelling at relevant lifetime exposures to support extended reactor operations.

  12. Kinetic characterization of swelling of liquid crystalline phases of glyceryl monooleate.

    PubMed

    Lee, Jaehwi; Choi, Sung-Up; Yoon, Mi-Kyeong; Choi, Young Wook

    2003-10-01

    Research in this paper focuses on the kinetic evaluation of swelling of the liquid crystalline phases of glyceryl monooleate (GMO). Swelling of the lamellar and cubic liquid crystalline phases of GMO was studied using two in vitro methods, a total immersion method and a Franz cell method. The swelling of the lamellar phase and GMO having 0 %w/w initial water content was temperature dependent. The swelling ratio was greater at 20 degrees C than 37 degrees C. The water uptake increased dramatically with decreasing initial water content of the liquid crystalline phases. The swelling rates obtained using the Franz cell method with a moist nylon membrane to mimic buccal drug delivery situation were slower than the total immersion method. The swelling was studied by employing first-order and second-order swelling kinetics. The swelling of the liquid crystalline phases of GMO could be described by second-order swelling kinetics. The initial stage of the swelling (t < 4 h) followed the square root of time relationship, indicating that this model is also suitable for describing the water uptake by the liquid crystalline matrices. These results obtained from the current study demonstrate that the swelling strongly depends on temperature, the initial water content of the liquid crystalline phases and the methodology employed for measuring the swelling of GMO.

  13. Spatially extended void-free dusty plasmas in a laboratory radio-frequency discharge

    NASA Astrophysics Data System (ADS)

    Schmidt, C.; Arp, O.; Piel, A.

    2011-11-01

    Laboratory experiments with thermophoretic levitation of dust particles for gravity compensation are reported. The observed spatially extended dust clouds were investigated, e.g., the dependence of discharge parameters on the void structure. These investigations lead to the discovery of an extended parameter region where spatially extended void-free clouds can be found. The mechanism of void closure is accompanied by a spontaneous change in the discharge topology. This change becomes evident from a reversal of the wave propagation direction.

  14. Testing the spherical evolution of cosmic voids

    NASA Astrophysics Data System (ADS)

    Demchenko, Vasiliy; Cai, Yan-Chuan; Heymans, Catherine; Peacock, John A.

    2016-11-01

    We study the spherical evolution model for voids in ΛCDM, where the evolution of voids is governed by dark energy at an earlier time than that for the whole universe or in overdensities. We show that the presence of dark energy suppresses the growth of peculiar velocities, causing void shell-crossing to occur at progressively later epochs as ΩΛ increases. We apply the spherical model to evolve the initial conditions of N-body simulated voids and compare the resulting final void profiles. We find that the model is successful in tracking the evolution of voids with radii greater than 30 h-1 Mpc, implying that void profiles could be used to constrain dark energy. We find that the initial peculiar velocities of voids play a significant role in shaping their evolution. Excluding the peculiar velocity in the evolution model delays the time of shell crossing.

  15. Testing the spherical evolution of cosmic voids

    NASA Astrophysics Data System (ADS)

    Demchenko, Vasiliy; Cai, Yan-Chuan; Heymans, Catherine; Peacock, John A.

    2016-08-01

    We study the spherical evolution model for voids in ΛCDM, where the evolution of voids is governed by dark energy at an earlier time than that for the whole universe or in overdensities. We show that the presence of dark energy suppresses the growth of peculiar velocities, causing void shell-crossing to occur at progressively later epochs as ΩΛ increases. We apply the spherical model to evolve the initial conditions of N-body simulated voids and compare the resulting final void profiles. We find that the model is successful in tracking the evolution of voids with radii greater than 30 h-1Mpc, implying that void profiles could be used to constrain dark energy. We find that the initial peculiar velocities of voids play a significant role in shaping their evolution. Excluding the peculiar velocity in the evolution model delays the time of shell crossing.

  16. Evolution of midplate hotspot swells: Numerical solutions

    NASA Technical Reports Server (NTRS)

    Liu, Mian; Chase, Clement G.

    1990-01-01

    The evolution of midplate hotspot swells on an oceanic plate moving over a hot, upwelling mantle plume is numerically simulated. The plume supplies a Gaussian-shaped thermal perturbation and thermally-induced dynamic support. The lithosphere is treated as a thermal boundary layer with a strongly temperature-dependent viscosity. The two fundamental mechanisms of transferring heat, conduction and convection, during the interaction of the lithosphere with the mantle plume are considered. The transient heat transfer equations, with boundary conditions varying in both time and space, are solved in cylindrical coordinates using the finite difference ADI (alternating direction implicit) method on a 100 x 100 grid. The topography, geoid anomaly, and heat flow anomaly of the Hawaiian swell and the Bermuda rise are used to constrain the models. Results confirm the conclusion of previous works that the Hawaiian swell can not be explained by conductive heating alone, even if extremely high thermal perturbation is allowed. On the other hand, the model of convective thinning predicts successfully the topography, geoid anomaly, and the heat flow anomaly around the Hawaiian islands, as well as the changes in the topography and anomalous heat flow along the Hawaiian volcanic chain.

  17. An analytical model for porous single crystals with ellipsoidal voids

    NASA Astrophysics Data System (ADS)

    Mbiakop, A.; Constantinescu, A.; Danas, K.

    2015-11-01

    A rate-(in)dependent constitutive model for porous single crystals with arbitrary crystal anisotropy (e.g., FCC, BCC, HCP, etc.) containing general ellipsoidal voids is developed. The proposed model, denoted as modified variational model (MVAR), is based on the nonlinear variational homogenization method, which makes use of a linear comparison porous material to estimate the response of the nonlinear porous single crystal. Periodic multi-void finite element simulations are used in order to validate the MVAR for a large number of parameters including cubic (FCC, BCC) and hexagonal (HCP) crystal anisotropy, various creep exponents (i.e., nonlinearity), several stress triaxiality ratios, general void shapes and orientations and various porosity levels. The MVAR model, which involves a priori no calibration parameters, is found to be in good agreement with the finite element results for all cases considered in the rate-dependent context. The model is then used in a predictive manner to investigate the complex response of porous single crystals in several cases with strong coupling between the anisotropy of the crystal and the (morphological) anisotropy induced by the shape and orientation of the voids. Finally, a simple way of calibrating the MVAR with just two adjustable parameters is depicted in the rate-independent context so that an excellent agreement with the FE simulation results is obtained. In this last case, this proposed model can be thought as a generalization of the Gurson model in the context of porous single crystals and general ellipsoidal void shapes and orientations.

  18. Void and precipitate structure in ion- and electron-irradiated ferritic alloys

    NASA Astrophysics Data System (ADS)

    Ohnuki, Soumei; Takahashi, Heishichiro; Takeyama, Taro

    1984-05-01

    Void formation and precipitation were investigated in Fe10Cr and Fe13Cr base alloys by 200 keV C + ion and 1 MeV electron irradiation. The ferritic alloys exhibited significant resistance to void swelling. In FeCr and FeCr-Si alloys, ion-irradiation produced the precipitates of M 23C 6 type. In the FeCrTi alloy, Ti-rich precipitates were formed with high number density on {100} plane. During electron-irradiation Fe-10Cr alloy, complex dislocation loops were produced with high number density, of which Burgers vector was mostly <100>. EDX analysis showed slightly enrichment of chromium on dislocation loops. These results suggested that the stability of <100> type dislocation structure at high dose is an important factor on good swelling resistance in the ferritic alloys, moreover, titanium addition will intensify the stability of the doslocations through the fine precipitation on dislocations.

  19. Subtask 12F1: Effect of neutron irradiation on swelling of vanadium-base alloys

    SciTech Connect

    Chung, H.M.; Loomis, B.A.; Smith, D.L.

    1995-03-01

    The objective of this work is to determine the effects of neutron irradiation on the density change, void distribution, and microstructural evolution of vanadium-base alloys. Swelling behavior and microstructural evolution of V-Ti, V-Cr-Ti, and V-Ti-Si alloys were investigated after irradiation at 420-600{degrees}C up to 114 dpa. The alloys exhibited swelling maxima between 30 and 80 dpa and swelling decreased on irradiation to higher dpa. This is in contrast to the monotonically increasing swelling of binary alloys that contain Fe, Ni, Cr, Mo, W, and Si. Precipitation of dense Ti{sub 5}Si{sub 3} promotes good resistance to swelling of the Ti-containing alloys, and it was concluded that Ti of >3 wt.% and 400-1000 wppm Si are necessary to effectively suppress swelling. Swelling was minimal in V-4Cr-4Ti, identified as the most promising alloy based on good mechanical properties and superior resistance to irradiation embrittlement. 18 refs., 6 figs., 1 tab.

  20. Swelling-induced and controlled curving in layered gel beams

    PubMed Central

    Lucantonio, A.; Nardinocchi, P.; Pezzulla, M.

    2014-01-01

    We describe swelling-driven curving in originally straight and non-homogeneous beams. We present and verify a structural model of swollen beams, based on a new point of view adopted to describe swelling-induced deformation processes in bilayered gel beams, that is based on the split of the swelling-induced deformation of the beam at equilibrium into two components, both depending on the elastic properties of the gel. The method allows us to: (i) determine beam stretching and curving, once assigned the characteristics of the solvent bath and of the non-homogeneous beam, and (ii) estimate the characteristics of non-homogeneous flat gel beams in such a way as to obtain, under free-swelling conditions, three-dimensional shapes. The study was pursued by means of analytical, semi-analytical and numerical tools; excellent agreement of the outcomes of the different techniques was found, thus confirming the strength of the method. PMID:25383031

  1. Redshift-space distortions around voids

    NASA Astrophysics Data System (ADS)

    Cai, Yan-Chuan; Taylor, Andy; Peacock, John A.; Padilla, Nelson

    2016-11-01

    We have derived estimators for the linear growth rate of density fluctuations using the cross-correlation function (CCF) of voids and haloes in redshift space. In linear theory, this CCF contains only monopole and quadrupole terms. At scales greater than the void radius, linear theory is a good match to voids traced out by haloes; small-scale random velocities are unimportant at these radii, only tending to cause small and often negligible elongation of the CCF near its origin. By extracting the monopole and quadrupole from the CCF, we measure the linear growth rate without prior knowledge of the void profile or velocity dispersion. We recover the linear growth parameter β to 9 per cent precision from an effective volume of 3( h-1Gpc)3 using voids with radius >25 h-1Mpc. Smaller voids are predominantly sub-voids, which may be more sensitive to the random velocity dispersion; they introduce noise and do not help to improve measurements. Adding velocity dispersion as a free parameter allows us to use information at radii as small as half of the void radius. The precision on β is reduced to 5 per cent. Voids show diverse shapes in redshift space, and can appear either elongated or flattened along the line of sight. This can be explained by the competing amplitudes of the local density contrast, plus the radial velocity profile and its gradient. The distortion pattern is therefore determined solely by the void profile and is different for void-in-cloud and void-in-void. This diversity of redshift-space void morphology complicates measurements of the Alcock-Paczynski effect using voids.

  2. Molecular accessibility in solvent swelled coals. Quarterly report

    SciTech Connect

    Kispert, L.D.

    1993-02-01

    An EPR technique developed in this lab is being used to determine the pore size and number distribution changes after swelling the coal samples with various solvents. Stable nitroxide radical spin probes of different sizes, shapes and reactivity are dissolved in an appropriate solvent, the coal sample is added to the resulting solution, stirred over night at elevated temperature, filtered, washed with a non swelling solvent to eliminate any spin probes that are not trapped in the pores and the spin concentration is measured. Comparing these spin probe measurements to DRIFT data have shown that the relative number distribution of acidic functionalities can be accurately predicted by the spin probe method. The spin probe method had also been used to predict the increase in elongated voids in Pittsburgh No. 8 (APCS No. 4) upon swelling with pyridine in agreement with independent SANS data. NMR relaxation data show that it is possible to deduce the pore (accessibility) distribution as a function of size (up to 6 mn). It has also been possible by variable temperature and ENDOR measurements to determine the presence of hydrogen bonding as a function of pore shape and size. The advantage of the EPR method is that it permits molecules of selected shape and size to be used as probes of accessible regions of coal, thus providing information on the importance of molecular shape.

  3. Theory of dust voids in plasmas.

    PubMed

    Goree, J; Morfill, G E; Tsytovich, V N; Vladimirov, S V

    1999-06-01

    Dusty plasmas in a gas discharge often feature a stable void, i.e., a dust-free region inside the dust cloud. This occurs under conditions relevant to both plasma processing discharges and plasma crystal experiments. The void results from a balance of the electrostatic and ion drag forces on a dust particle. The ion drag force is driven by a flow of ions outward from an ionization source and toward the surrounding dust cloud, which has a negative space charge. In equilibrium the force balance for dust particles requires that the boundary with the dust cloud be sharp, provided that the particles are cold and monodispersive. Numerical solutions of the one-dimensional nonlinear fluid equations are carried out including dust charging and dust-neutral collisions, but not ion-neutral collisions. The regions of parameter space that allow stable void equilibria are identified. There is a minimum ionization rate that can sustain a void. Spatial profiles of plasma parameters in the void are reported. In the absence of ion-neutral collisions, the ion flow enters the dust cloud's edge at Mach number M=1. Phase diagrams for expanding or contracting voids reveal a stationary point corresponding to a single stable equilibrium void size, provided the ionization rate is constant. Large voids contract and small voids expand until they attain this stationary void size. On the other hand, if the ionization rate is not constant, the void size can oscillate. Results are compared to recent laboratory and microgravity experiments.

  4. The Star Formation Properties of Void Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Moorman, Crystal; Vogeley, Michael S.

    2016-01-01

    We measure the star formation properties of two large samples of galaxies from the SDSS in large-scale cosmic voids on time scales of 10 Myr and 100 Myr, using Ha emission line strengths and GALEX FUV fluxes, respectively. The first sample consists of 109,818 optically selected galaxies. We find that void galaxies in this sample have higher specific star formation rates (SSFRs; star formation rates per unit stellar mass) than similar stellar mass galaxies in denser regions. The second sample is a subset of the optically selected sample containing 8070 galaxies with reliable S/N HI detections from ALFALFA. For the HI detected sample, SSFRs are similar regardless of large-scale environment. Investigating only the HI detected dwarf galaxies reveals a trend towards higher SSFRs in voids. Furthermore, we estimate the star formation rate per unit HI mass, known as the star formation efficiency (SFE) of a galaxy, as a function of environment. For the overall HI detected population, we notice no environmental dependence. Limiting the sample to dwarf galaxies again reveals a trend towards higher SFEs in voids. These results suggest that void environments provide a nurturing environment for dwarf galaxy evolution.

  5. The persistent percolation of single-stream voids

    NASA Astrophysics Data System (ADS)

    Falck, B.; Neyrinck, M. C.

    2015-07-01

    We study the nature of voids defined as single-stream regions that have not undergone shell-crossing. We use ORIGAMI to determine the cosmic web morphology of each dark matter particle in a suite of cosmological N-body simulations, which explicitly calculates whether a particle has crossed paths with others along multiple sets of axes and does not depend on a parameter or smoothing scale. The theoretical picture of voids is that of expanding underdensities with borders defined by shell-crossing. We find instead that locally underdense single-stream regions are not bounded on all sides by multi-stream regions, thus they percolate, filling the simulation volume; we show that the set of multi-stream particles also percolates. This percolation persists to high resolution, where the mass fraction of single-stream voids is low, because the volume fraction remains high; we speculate on the fraction of collapsed mass in the continuum limit of infinite resolution. By introducing a volume threshold parameter to define underdense void `cores', we create a catalogue of ORIGAMI voids which consist entirely of single-stream particles and measure their percolation properties, volume functions, and average densities.

  6. Low-temperature swelling in LWR internal components: a computational assessment

    SciTech Connect

    Stoller, Roger E.; Golubov, Stanislav I.; Barashev, Alexander V.

    2015-01-01

    A modern cluster dynamics model has been used to investigate the materials and irradiation parameters that control microstructural evolution under the relatively low-temperature exposure conditions that are representative of the operating environment for in-core light water reactor components. The focus is on components fabricated from austenitic stainless steel. The model accounts for the synergistic interaction between radiation-produced vacancies and the helium that is produced by nuclear transmutation reactions. Cavity nucleation rates are shown to be relatively high in this temperature regime (275 to 325 °C), but are sensitive to assumptions about the fine-scale microstructure produced under low-temperature irradiation. The cavity nucleation rates observed run counter to the expectation that void swelling would not occur under these conditions. This expectation was based on previous research on void swelling in austenitic steels in fast reactors. This misleading impression arose primarily from an absence of relevant data. The results of the computational modeling are generally consistent with recent data obtained by examining ex-service components. The long-term objective of this research is to provide a predictive model of void swelling at relevant lifetime exposures to support extended reactor operations.

  7. Nocturia: The circadian voiding disorder

    PubMed Central

    Moon, Young Tae; Kim, Kyung Do

    2016-01-01

    Nocturia is a prevalent condition of waking to void during the night. The concept of nocturia has evolved from being a symptomatic aspect of disease associated with the prostate or bladder to a form of lower urinary tract disorder. However, recent advances in circadian biology and sleep science suggest that it might be important to consider nocturia as a form of circadian dysfunction. In the current review, nocturia is reexamined with an introduction to sleep disorders and recent findings in circadian biology in an attempt to highlight the importance of rediscovering nocturia as a problem of chronobiology. PMID:27195315

  8. Nocturia: The circadian voiding disorder.

    PubMed

    Kim, Jin Wook; Moon, Young Tae; Kim, Kyung Do

    2016-05-01

    Nocturia is a prevalent condition of waking to void during the night. The concept of nocturia has evolved from being a symptomatic aspect of disease associated with the prostate or bladder to a form of lower urinary tract disorder. However, recent advances in circadian biology and sleep science suggest that it might be important to consider nocturia as a form of circadian dysfunction. In the current review, nocturia is reexamined with an introduction to sleep disorders and recent findings in circadian biology in an attempt to highlight the importance of rediscovering nocturia as a problem of chronobiology. PMID:27195315

  9. Voiding dysfunction due to neurosyphilis.

    PubMed

    Garber, S J; Christmas, T J; Rickards, D

    1990-07-01

    Three patients with neurosyphilis presenting with urinary frequency, incontinence and voiding dysfunction were investigated. Unlike the previously reported finding of areflexia in tabes dorsalis, all 3 had hypocompliant detrusor hyper-reflexia with detrusor-sphincter dyssynergia and post-micturition residual urine. One patient also had bladder neck dyssynergia treated by bladder neck incision. The other 2 patients were initially managed by intermittent catheterisation but 1 ultimately underwent urinary diversion. The clinical relevance of these findings and the treatment of this condition are discussed.

  10. Large-scale clustering of cosmic voids

    NASA Astrophysics Data System (ADS)

    Chan, Kwan Chuen; Hamaus, Nico; Desjacques, Vincent

    2014-11-01

    We study the clustering of voids using N -body simulations and simple theoretical models. The excursion-set formalism describes fairly well the abundance of voids identified with the watershed algorithm, although the void formation threshold required is quite different from the spherical collapse value. The void cross bias bc is measured and its large-scale value is found to be consistent with the peak background split results. A simple fitting formula for bc is found. We model the void auto-power spectrum taking into account the void biasing and exclusion effect. A good fit to the simulation data is obtained for voids with radii ≳30 Mpc h-1 , especially when the void biasing model is extended to 1-loop order. However, the best-fit bias parameters do not agree well with the peak-background results. Being able to fit the void auto-power spectrum is particularly important not only because it is the direct observable in galaxy surveys, but also our method enables us to treat the bias parameters as nuisance parameters, which are sensitive to the techniques used to identify voids.

  11. Study of void collapse leading to shock initiation and ignition in heterogeneous energetic material

    NASA Astrophysics Data System (ADS)

    Rai, Nirmal Kumar; Koundinyan, Sushilkumar Prabu; Udaykumar, H. S.

    2015-06-01

    In heterogeneous energetic materials like PBX, porosity plays an important role in shock initiation and ignition. This is because the collapse of voids leads to the formation of local high temperature regions termed as hot spots under the application of shock loading. The formation of hot spots can take place because of several mechanisms such as plastic deformation of voids, hydrodynamic impact on voids leading to the formation of high speed material jets etc. Once these hot spots are formed, they can lead to reaction and ignition in the explosive material. However, diffusive phenomenon like heat conduction can play an important role in shock initiation because depending on the size and intensity of void collapse hot spots, local ignition conditions can be smeared out. In the current work, void collapse leading to shock initiation and ignition in HMX has been studied using a massively parallel Eulerian code, SCIMITAR3D. The chemical kinetics of HMX decomposition and reaction has been modeled using the Henson-Smilowitz multi-step mechanism. Based on the current framework an ignition criterion has been established for single void collapse analysis for various shock strengths. Furthermore, the effects of void-void interactions have been analyzed demonstrating the important role of the combination of void fraction, reaction chemistry and heat conduction in determining the ignition threshold. This work has been funded from the AFRL-RWPC, Computational Mechanics Branch, Eglin AFB, Program Manager: Dr. Martin Schmidt.

  12. Bimodal swelling responses in microgel thin films.

    PubMed

    Sorrell, Courtney D; Lyon, L Andrew

    2007-04-26

    A series of studies on microgel thin films is described, wherein quartz crystal microgravimetry (QCM), surface plasmon resonance (SPR), and atomic force microscopy (AFM) have been used to probe the properties of microstructured polymer thin films as a function of film architecture and solution pH. Thin films composed of pNIPAm-co-AAc microgels were constructed by using spin-coating layer-by-layer (scLbL) assembly with poly(allylamine hydrochloride) (PAH) as a polycationic "glue". Our findings suggest that the interaction between the negatively charged microgels and the positively charged PAH has a significant impact on the pH responsivity of the film. These effects are observable in both the optical and mechanical behaviors of the films. The most significant changes in behavior are observed when the motional resistance of a quartz oscillator is monitored via QCM experiments. Slight changes to the film architecture and alternating the pH of the environment significantly changes the QCM and SPR responses, suggesting a pH-dependent swelling that is dependent on both particle swelling and polyelectrolyte de-complexation. Together, these studies allow for a deeper understanding of the morphological changes that take place in environmentally responsive microgel-based thin films. PMID:17407344

  13. Direct transformation of vacancy voids to stacking fault tetrahedra.

    PubMed

    Uberuaga, B P; Hoagland, R G; Voter, A F; Valone, S M

    2007-09-28

    Defect accumulation is the principal factor leading to the swelling and embrittlement of materials during irradiation. It is commonly assumed that, once defect clusters nucleate, their structure remains essentially constant while they grow in size. Here, we describe a new mechanism, discovered during accelerated molecular dynamics simulations of vacancy clusters in fcc metals, that involves the direct transformation of a vacancy void to a stacking fault tetrahedron (SFT) through a series of 3D structures. This mechanism is in contrast with the collapse to a 2D Frank loop which then transforms to an SFT. The kinetics of this mechanism are characterized by an extremely large rate prefactor, tens of orders of magnitude larger than is typical of atomic processes in fcc metals.

  14. Swelling-resistant nuclear fuel

    DOEpatents

    Arsenlis, Athanasios; Satcher, Jr., Joe; Kucheyev, Sergei O.

    2011-12-27

    A nuclear fuel according to one embodiment includes an assembly of nuclear fuel particles; and continuous open channels defined between at least some of the nuclear fuel particles, wherein the channels are characterized as allowing fission gasses produced in an interior of the assembly to escape from the interior of the assembly to an exterior thereof without causing significant swelling of the assembly. Additional embodiments, including methods, are also presented.

  15. Managing Chemotherapy Side Effects: Swelling (Fluid Retention)

    MedlinePlus

    ... ancer I nstitute Managing Chemotherapy Side Effects Swelling (Fluid retention) “My hands and feet were swollen and ... at one time. Managing Chemotherapy Side Effects: Swelling (Fluid retention) Weigh yourself. l Weigh yourself at the ...

  16. Universal density profile for cosmic voids.

    PubMed

    Hamaus, Nico; Sutter, P M; Wandelt, Benjamin D

    2014-06-27

    We present a simple empirical function for the average density profile of cosmic voids, identified via the watershed technique in ΛCDM N-body simulations. This function is universal across void size and redshift, accurately describing a large radial range of scales around void centers with only two free parameters. In analogy to halo density profiles, these parameters describe the scale radius and the central density of voids. While we initially start with a more general four-parameter model, we find two of its parameters to be redundant, as they follow linear trends with the scale radius in two distinct regimes of the void sample, separated by its compensation scale. Assuming linear theory, we derive an analytic formula for the velocity profile of voids and find an excellent agreement with the numerical data as well. In our companion paper [Sutter et al., arXiv:1309.5087 [Mon. Not. R. Astron. Soc. (to be published)

  17. Universal Density Profile for Cosmic Voids

    NASA Astrophysics Data System (ADS)

    Hamaus, Nico; Sutter, P. M.; Wandelt, Benjamin D.

    2014-06-01

    We present a simple empirical function for the average density profile of cosmic voids, identified via the watershed technique in ΛCDM N-body simulations. This function is universal across void size and redshift, accurately describing a large radial range of scales around void centers with only two free parameters. In analogy to halo density profiles, these parameters describe the scale radius and the central density of voids. While we initially start with a more general four-parameter model, we find two of its parameters to be redundant, as they follow linear trends with the scale radius in two distinct regimes of the void sample, separated by its compensation scale. Assuming linear theory, we derive an analytic formula for the velocity profile of voids and find an excellent agreement with the numerical data as well. In our companion paper [Sutter et al., arXiv:1309.5087 [Mon. Not. R. Astron. Soc. (to be published)

  18. Cosmology with void-galaxy correlations.

    PubMed

    Hamaus, Nico; Wandelt, Benjamin D; Sutter, P M; Lavaux, Guilhem; Warren, Michael S

    2014-01-31

    Galaxy bias, the unknown relationship between the clustering of galaxies and the underlying dark matter density field is a major hurdle for cosmological inference from large-scale structure. While traditional analyses focus on the absolute clustering amplitude of high-density regions mapped out by galaxy surveys, we propose a relative measurement that compares those to the underdense regions, cosmic voids. On the basis of realistic mock catalogs we demonstrate that cross correlating galaxies and voids opens up the possibility to calibrate galaxy bias and to define a static ruler thanks to the observable geometric nature of voids. We illustrate how the clustering of voids is related to mass compensation and show that volume-exclusion significantly reduces the degree of stochasticity in their spatial distribution. Extracting the spherically averaged distribution of galaxies inside voids from their cross correlations reveals a remarkable concordance with the mass-density profile of voids.

  19. SYNERESIS AND SWELLING OF GELATIN.

    PubMed

    Kunitz, M

    1928-11-20

    1. When solid blocks of isoelectric gelatin are placed in cold distilled water or dilute buffer of pH 4.7, only those of a gelatin content of more than 10 per cent swell, while those of a lower gelatin content not only do not swell but actually lose water. 2. The final quantity of water lost by blocks of dilute gelatin is the same whether the block is immersed in a large volume of water or whether syneresis has been initiated in the gel through mechanical forces such as shaking, pressure, etc., even in the absence of any outside liquid, thus showing that syneresis is identical with the process of negative swelling of dilute gels when placed in cold water, and may be used as a convenient term for it. 3. Acid- or alkali-containing gels give rise to greater syneresis than isoelectric gels, after the acid or alkali has been removed by dialysis. 4. Salt-containing gels show greater syneresis than salt-free gels of the same pH, after the salt has been washed away. 5. The acid and alkali and also the salt effect on syneresis of gels disappears at a gelatin concentration above 8 per cent. 6. The striking similarity in the behavior of gels with respect to syneresis and of gelatin solutions with respect to viscosity suggests the probability that both are due to the same mechanism, namely the mechanism of hydration of the micellae in gelatin by means of osmosis as brought about either by diffusible ions, as in the presence of acid or alkali, or by the soluble gelatin present in the micellae. The greater the pressures that caused swelling of the micellae while the gelatin was in the sol state, the greater is the loss of water from the gels when the pressures are removed. 7. A quantitative study of the loss of water by dilute gels of various gelatin content shows that the same laws which have been found by Northrop to hold for the swelling of gels of high concentrations apply also to the process of losing water by dilute gels, i.e. to the process of syneresis. The general

  20. Voids in cosmological simulations over cosmic time

    NASA Astrophysics Data System (ADS)

    Wojtak, Radosław; Powell, Devon; Abel, Tom

    2016-06-01

    We study evolution of voids in cosmological simulations using a new method for tracing voids over cosmic time. The method is based on tracking watershed basins (contiguous regions around density minima) of well-developed voids at low redshift, on a regular grid of density field. It enables us to construct a robust and continuous mapping between voids at different redshifts, from initial conditions to the present time. We discuss how the new approach eliminates strong spurious effects of numerical origin when voids' evolution is traced by matching voids between successive snapshots (by analogy to halo merger trees). We apply the new method to a cosmological simulation of a standard Λ-cold-dark-matter cosmological model and study evolution of basic properties of typical voids (with effective radii 6 h-1 Mpc < Rv < 20 h-1 Mpc at redshift z = 0) such as volumes, shapes, matter density distributions and relative alignments. The final voids at low redshifts appear to retain a significant part of the configuration acquired in initial conditions. Shapes of voids evolve in a collective way which barely modifies the overall distribution of the axial ratios. The evolution appears to have a weak impact on mutual alignments of voids implying that the present state is in large part set up by the primordial density field. We present evolution of dark matter density profiles computed on isodensity surfaces which comply with the actual shapes of voids. Unlike spherical density profiles, this approach enables us to demonstrate development of theoretically predicted bucket-like shape of the final density profiles indicating a wide flat core and a sharp transition to high-density void walls.

  1. Atomistic insights into dislocation-based mechanisms of void growth and coalescence

    NASA Astrophysics Data System (ADS)

    Mi, Changwen; Buttry, Daniel A.; Sharma, Pradeep; Kouris, Demitris A.

    2011-09-01

    One of the low-temperature failure mechanisms in ductile metallic alloys is the growth of voids and their coalescence. In the present work we attempt to obtain atomistic insights into the mechanisms underpinning cavitation in a representative metal, namely Aluminum. Often the pre-existing voids in metallic alloys such as Al have complex shapes (e.g. corrosion pits) and the defromation/damage mechanisms exhibit a rich size-dependent behavior across various material length scales. We focus on these two issues in this paper through large-scale calculations on specimens of sizes ranging from 18 thousand to 1.08 million atoms. In addition to the elucidation of the dislocation propagation based void growth mechanism we highlight the observed length scale effect reflected in the effective stress-strain response, stress triaxiality and void fraction evolution. Furthermore, as expected, the conventionally used Gurson's model fails to capture the observed size-effects calling for a mechanistic modification that incorporates the mechanisms observed in our (and other researchers') simulation. Finally, in our multi-void simulations, we find that, the splitting of a big void into a distribution of small ones increases the load-carrying capacity of specimens. However, no obvious dependence of the void fraction evolution on void coalescence is observed.

  2. Void evolution in polycarbonate at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Chen, Y. H.; Feng Chou, Kuo; Li, C. L.; Lee, Sanboh

    2011-08-01

    The void evolution in polycarbonate (PC) at elevated temperatures was investigated. Internal cylindrical cracks and voids were induced in PC by Nd-YAG laser irradiation. During the annealing at temperatures of 177-197 °C, the spherical void grows to a maximum size, which then decreases, and is finally leveling off. A model of void evolution based on the evaporation and condensation mechanisms for growth and shrinkage is proposed. The theoretical predictions are in good agreement with the experimental data. The activation energies of evaporation and condensation processes are determined to be 477.31 and 611.49 kJ/mol, respectively.

  3. Void growth by dislocation-loop emission

    NASA Astrophysics Data System (ADS)

    Ahn, D. C.; Sofronis, P.; Kumar, M.; Belak, J.; Minich, R.

    2007-03-01

    Experimental results from spall tests on aluminum reveal the presence of a dense dislocation structure in an annulus around a void that grew under the tensile pulse when a shock wave was reflected at the free surface of the specimen. The proposition is that dislocation emission from the void surface under load is a viable mechanism for void growth. To understand void growth in the absence of diffusive effects, the interstitial-loop emission mechanism under tensile hydrostatic stress is investigated. First, the micromechanics of pile-up formation when interstitial loops are emitted from a void under applied macroscopic loading is reviewed. Demand for surface energy expenditure upon void-surface change is taken into consideration. It is demonstrated that in face-centered cubic metals loop emission from voids with a radius of ˜10 nm is indeed energetically possible in the hydrostatic stress environment generated by shock loading. On the other hand, the levels of hydrostatic stress prevalent in common structural applications are not sufficient to drive loops at equilibrium positions above a ˜10 nm void. However, for voids larger than about 100 nm, the energetics of loop emission are easily met as a necessary condition even under the low stress environment prevalent in structural applications.

  4. Void evolution in polycarbonate at elevated temperatures

    SciTech Connect

    Chen, Y. H.; Li, C. L.; Lee, Sanboh; Kuo Feng Chou

    2011-08-15

    The void evolution in polycarbonate (PC) at elevated temperatures was investigated. Internal cylindrical cracks and voids were induced in PC by Nd-YAG laser irradiation. During the annealing at temperatures of 177-197 deg. C, the spherical void grows to a maximum size, which then decreases, and is finally leveling off. A model of void evolution based on the evaporation and condensation mechanisms for growth and shrinkage is proposed. The theoretical predictions are in good agreement with the experimental data. The activation energies of evaporation and condensation processes are determined to be 477.31 and 611.49 kJ/mol, respectively.

  5. Experimental investigation of stress effect on swelling and microstructure of Fe-16Cr-15Ni-3Mo-Nb austenitic stainless steel under low-temperature irradiation up to high damage dose in the BOR-60 reactor

    NASA Astrophysics Data System (ADS)

    Neustroev, V. S.; Ostrovsky, Z. E.; Shamardin, V. K.

    2004-08-01

    The present paper was devoted to investigation of the stress effect on swelling and microstructure evolution of the Fe-15.8Cr-15.3Ni-2.8Mo-0.6Nb steel irradiated in the BOR-60 reactor at temperatures from 395 to 410 °C and damage doses from 79 to 98 dpa. Was found out that the stress increase leads to an increase of swelling, that can be associated with a decrease in incubation period with a practically constant swelling rate. Voids concentration increases at the first stage of irradiation when the void sizes are practically constant, and then the concentration reaches some saturation and swelling increase is caused by void growth.

  6. Phase-field Modeling of Void Migration and Growth Kinetics in Materials under Irradiation and Temperature Field

    SciTech Connect

    Li, Yulan; Hu, Shenyang Y.; Sun, Xin; Gao, Fei; Henager, Charles H.; Khaleel, Mohammad A.

    2010-12-15

    A phase-field model is developed to investigate the migration of vacancies, interstitials, and voids as well as void growth kinetics in materials under radiation and temperature field. The model takes into account the generation of vacancies and interstitials associated with the irradiation damage, the recombination between vacancies and interstitials, defect diffusion, and defect sinks. The effect of void sizes, vacancy concentration, vacancy generation rate, recombination rate, and temperature gradient on a single void migration and growth kinetics is parametrically studied. The results demonstrate that the temperature gradient causes void migration and defect fluxes, i.e., the Soret effect, which affects void stability and growth kinetics. It is found that 1) the void migration mobility is independent of the void size, which is in agreement with the theoretical prediction with the assumption of bulk diffusion controlled migration; 2) the void migration mobility strongly depends on temperature gradient; and 3) the effect of defect concentration, generation rate, and recombination rate on void migration mobility is minor although they strongly influence the void growth kinetics.

  7. Scrotal Swelling in the Neonate

    PubMed Central

    Basta, Amaya M.; Courtier, Jesse; Phelps, Andrew; Copp, Hillary L.; MacKenzie, John D.

    2016-01-01

    Discovery of scrotal swelling in a neonate can be a source of anxiety for parents, clinicians, and sonologists alike. This pictorial essay provides a focused review of commonly encountered scrotal masses and mimics specific to the neonatal setting. Although malignancy is a concern, it is very uncommon, as most neonatal scrotal masses are benign. Key discriminating features and management options are highlighted to improve the radiologist’s ability to diagnose neonatal scrotal conditions and guide treatment decisions. Neonatal scrotal processes ranging from common to uncommon will be discussed. PMID:25715370

  8. Statistics and geometry of cosmic voids

    SciTech Connect

    Gaite, José

    2009-11-01

    We introduce new statistical methods for the study of cosmic voids, focusing on the statistics of largest size voids. We distinguish three different types of distributions of voids, namely, Poisson-like, lognormal-like and Pareto-like distributions. The last two distributions are connected with two types of fractal geometry of the matter distribution. Scaling voids with Pareto distribution appear in fractal distributions with box-counting dimension smaller than three (its maximum value), whereas the lognormal void distribution corresponds to multifractals with box-counting dimension equal to three. Moreover, voids of the former type persist in the continuum limit, namely, as the number density of observable objects grows, giving rise to lacunar fractals, whereas voids of the latter type disappear in the continuum limit, giving rise to non-lacunar (multi)fractals. We propose both lacunar and non-lacunar multifractal models of the cosmic web structure of the Universe. A non-lacunar multifractal model is supported by current galaxy surveys as well as cosmological N-body simulations. This model suggests, in particular, that small dark matter halos and, arguably, faint galaxies are present in cosmic voids.

  9. Void Fraction Instrument operation and maintenance manual

    SciTech Connect

    Borgonovi, G.; Stokes, T.I.; Pearce, K.L.; Martin, J.D.; Gimera, M.; Graves, D.B.

    1994-09-01

    This Operations and Maintenance Manual (O&MM) addresses riser installation, equipment and personnel hazards, operating instructions, calibration, maintenance, removal, and other pertinent information necessary to safely operate and store the Void Fraction Instrument. Final decontamination and decommissioning of the Void Fraction Instrument are not covered in this document.

  10. A molecular dynamics study of void initiation and growth in monocrystalline and nanocrystalline copper

    NASA Astrophysics Data System (ADS)

    Traiviratana, Sirirat

    MD simulations in monocrystalline and nanocrystalline copper were carried out with LAMMPS to reveal void growth mechanisms. The specimens were subjected to both tensile uniaxial and hydrostatic strains; the results confirm that the emission of (shear) loops is the primary mechanism of void growth. The expansion of the loops and their cross slip leads to the severely work hardened layer surrounding a growing void. Calculations were carried out on voids with different sizes, and a size dependence of the stress response to emitted dislocations was observed, in disagreement with the Gurson model [1] which is scale independent. The growth of voids simulated by MD is compared with the Cocks-Ashby constitutive model and significant agreement is found. The density of geometrically-necessary dislocations as a function of void size is calculated based on the emission of shear loops and their outward propagation. Calculations were also carried out for a void at the interface between two grains sharing a tilt boundary. The results show similar dislocation behaviors. A code that uses Voronoi tessellation for constructing nanocrystalline structures was developed and used to prepare the structures for simulations. Nanocrystal simulations reveal grain sliding and grain rotation as the nanocrystal deformed. Voids were nucleated at grain junctions and grew to coalescence as dislocations accommodated the material transfer. A code that can be used during post-processing to extract useful dislocation information from MD simulation data was partially developed and proved the feasibility of automatically analyzing dislocations.

  11. Void probability as a function of the void's shape and scale-invariant models

    NASA Technical Reports Server (NTRS)

    Elizalde, E.; Gaztanaga, E.

    1991-01-01

    The dependence of counts in cells on the shape of the cell for the large scale galaxy distribution is studied. A very concrete prediction can be done concerning the void distribution for scale invariant models. The prediction is tested on a sample of the CfA catalog, and good agreement is found. It is observed that the probability of a cell to be occupied is bigger for some elongated cells. A phenomenological scale invariant model for the observed distribution of the counts in cells, an extension of the negative binomial distribution, is presented in order to illustrate how this dependence can be quantitatively determined. An original, intuitive derivation of this model is presented.

  12. Molecular accessibility in solvent swelled coal. Quarterly report

    SciTech Connect

    Kispert, L.D.

    1992-05-29

    An EPR technique developed in this lab is being used to determine the pore size and number distribution changes after swelling the coal samples with various solvents. Stable nitroxide radical spin probes of different sizes, shapes and reactivity are dissolved in an appropriate solvent, the coal sample is added to the resulting solution, stirred over night at elevated temperature, filtered, washed with a nonswelling solvent to eliminate any spin probes that are not trapped in the pores and the spin concentration measured. Comparing these spin probe measurements to DRIFT data have shown that the relative number distribution of acidic functionalities can be accurately predicted by the spin probe method. The spin probe method has also been used to predict the increase in elongated voids in Pittsburgh No. 8 (APCS No. 4) upon swelling with pyridine in agreement with independent SANS data. NMR relaxation data show that it is possible to deduce the pore (accessibility) distribution as a function of size (up to 6 nm). It has also been possible by variable temperature and ENDOR measurements to determine the presence of hydrogen bonding as a function of pore shape and size. The advantage of EPR method is that it permits molecules of selected shape and size to be used as probes of accessible regions of the coal, thus providing information on the importance of molecular shape.

  13. Molecular accessibility in solvent swelled coal. Quarterly report

    SciTech Connect

    Kispert, L.D.

    1992-08-01

    An EPR technique developed in this lab is being used to determine the pore size and number distribution changes after swelling the coal samples with various solvents. Stable nitroxide radical spin probes of different sizes, shapes and reactivity are dissolved in an appropriate solvent, the coal sample is added to the resulting solution, stirred over night at elevated temperature, filtered, washed with a nonswelling solvent to eliminate any spin probes that are not trapped in the pores and the spin concentration measured. Comparing these spin probe measurements to DRIFT data have shown that the relative number distribution of acidic functionalities can be accurately predicted by the spin probe method. The spin probe method has also been used to predict the increase in elongated voids in Pittsburgh No. 8 (APCS No. 4) upon swelling with pyridine in agreement with independent SANS data. NMR relaxation data shows that it is possible to deduce the pore (accessibility) distribution as a function of size (up to 6 nm). It has also been possible by variable temperature and ENDOR measurements to determine the presence of hydrogen bonding as a function of pore shape and size. The advantage of the EPR method is that it permits molecules of selected shape and size to be used as probes of accessible regions of the coal, thus providing information on the importance of molecular shape.

  14. Geoid height versus topography for oceanic plateaus and swells

    NASA Technical Reports Server (NTRS)

    Sandwell, David T.; Mackenzie, Kevin R.

    1989-01-01

    Gridded geoid height data (Marsh et al.l, 1986) and gridded bathymetry data (Van Wykhouse, 1973) are used to estimate the average compensation depths of 53 oceanic swells and plateaus. The relationship between geoid height and topography is examined using Airy and thermal compensation models. It is shown that geoid height is linearly related to topography between wavelengths of 400 and 4000 m as predicted by isostatic compensation models. The geoid/topography ratio is dependent on the average depth of compensation. The intermediate geoid/topography ratios of most thermal swells are interpreted as a linear combination of the decaying thermal swell signature and that of the persisting Airy-compensated volcanic edifice.

  15. Swell Sleeves for Testing Explosive Devices

    NASA Technical Reports Server (NTRS)

    Hinkel, Todd J.; Dean, Richard J.; Hohmann, Carl W.; Hacker, Scott C.; Harrington, Douglas W.; Bacak, James W.

    2003-01-01

    A method of testing explosive and pyrotechnic devices involves exploding the devices inside swell sleeves. Swell sleeves have been used previously for measuring forces. In the present method, they are used to obtain quantitative indications of the energy released in explosions of the devices under test. A swell sleeve is basically a thick-walled, hollow metal cylinder threaded at one end to accept a threaded surface on a device to be tested (see Figure 1). Once the device has been tightly threaded in place in the swell sleeve, the device-and-swell-sleeve assembly is placed in a test fixture, then the device is detonated. After the explosion, the assembly is removed from the test fixture and placed in a coordinate-measuring machine for measurement of the diameter of the swell sleeve as a function of axial position. For each axial position, the original diameter of the sleeve is subtracted from the diameter of the sleeve as swollen by the explosion to obtain the diametral swelling as a function of axial position (see Figure 2). The amount of swelling is taken as a measure of the energy released in the explosion. The amount of swelling can be compared to a standard amount of swelling to determine whether the pyrotechnic device functioned as specified.

  16. Observation of voids and optical seizing of voids in silica glass with infrared femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Watanabe, Wataru; Toma, Tadamasa; Yamada, Kazuhiro; Nishii, Junji; Hayashi, Ken-ichi; Itoh, Kazuyoshi

    2000-11-01

    Many researchers have investigated the interaction of femtosecond laser pulses with a wide variety of materials. The structural modifications both on the surface and inside the bulk of transparent materials have been demonstrated. When femtosecond laser pulses are focused into glasses with a high numerical-aperture objective, voids are formed. We demonstrate that one can seize and move voids formed by femtosecond laser pulses inside silica glass and also merge two voids into one. We also present clear evidence that a void is a cavity by showing a scanning-electron-microscope image of cleft voids: we clove through the glass along a plane that includes the laser-ablated thin line on the surface and the voids formed inside. The optical seizing and merging of voids are important basic techniques for fabricate micro-optical dynamic devices, such as the rewritable 3-D optical storage.

  17. VIDE: The Void IDentification and Examination toolkit

    NASA Astrophysics Data System (ADS)

    Sutter, P. M.; Lavaux, G.; Hamaus, N.; Pisani, A.; Wandelt, B. D.; Warren, M.; Villaescusa-Navarro, F.; Zivick, P.; Mao, Q.; Thompson, B. B.

    2015-03-01

    We present VIDE, the Void IDentification and Examination toolkit, an open-source Python/C++ code for finding cosmic voids in galaxy redshift surveys and N -body simulations, characterizing their properties, and providing a platform for more detailed analysis. At its core, VIDE uses a substantially enhanced version of ZOBOV (Neyinck 2008) to calculate a Voronoi tessellation for estimating the density field and performing a watershed transform to construct voids. Additionally, VIDE provides significant functionality for both pre- and post-processing: for example, VIDE can work with volume- or magnitude-limited galaxy samples with arbitrary survey geometries, or dark matter particles or halo catalogs in a variety of common formats. It can also randomly subsample inputs and includes a Halo Occupation Distribution model for constructing mock galaxy populations. VIDE uses the watershed levels to place voids in a hierarchical tree, outputs a summary of void properties in plain ASCII, and provides a Python API to perform many analysis tasks, such as loading and manipulating void catalogs and particle members, filtering, plotting, computing clustering statistics, stacking, comparing catalogs, and fitting density profiles. While centered around ZOBOV, the toolkit is designed to be as modular as possible and accommodate other void finders. VIDE has been in development for several years and has already been used to produce a wealth of results, which we summarize in this work to highlight the capabilities of the toolkit. VIDE is publicly available at

  18. Antilensing: the bright side of voids.

    PubMed

    Bolejko, Krzysztof; Clarkson, Chris; Maartens, Roy; Bacon, David; Meures, Nikolai; Beynon, Emma

    2013-01-11

    More than half of the volume of our Universe is occupied by cosmic voids. The lensing magnification effect from those underdense regions is generally thought to give a small dimming contribution: objects on the far side of a void are supposed to be observed as slightly smaller than if the void were not there, which together with conservation of surface brightness implies net reduction in photons received. This is predicted by the usual weak lensing integral of the density contrast along the line of sight. We show that this standard effect is swamped at low redshifts by a relativistic Doppler term that is typically neglected. Contrary to the usual expectation, objects on the far side of a void are brighter than they would be otherwise. Thus the local dynamics of matter in and near the void is crucial and is only captured by the full relativistic lensing convergence. There are also significant nonlinear corrections to the relativistic linear theory, which we show actually underpredicts the effect. We use exact solutions to estimate that these can be more than 20% for deep voids. This remains an important source of systematic errors for weak lensing density reconstruction in galaxy surveys and for supernovae observations, and may be the cause of the reported extra scatter of field supernovae located on the edge of voids compared to those in clusters. PMID:23383886

  19. Antilensing: The Bright Side of Voids

    NASA Astrophysics Data System (ADS)

    Bolejko, Krzysztof; Clarkson, Chris; Maartens, Roy; Bacon, David; Meures, Nikolai; Beynon, Emma

    2013-01-01

    More than half of the volume of our Universe is occupied by cosmic voids. The lensing magnification effect from those underdense regions is generally thought to give a small dimming contribution: objects on the far side of a void are supposed to be observed as slightly smaller than if the void were not there, which together with conservation of surface brightness implies net reduction in photons received. This is predicted by the usual weak lensing integral of the density contrast along the line of sight. We show that this standard effect is swamped at low redshifts by a relativistic Doppler term that is typically neglected. Contrary to the usual expectation, objects on the far side of a void are brighter than they would be otherwise. Thus the local dynamics of matter in and near the void is crucial and is only captured by the full relativistic lensing convergence. There are also significant nonlinear corrections to the relativistic linear theory, which we show actually underpredicts the effect. We use exact solutions to estimate that these can be more than 20% for deep voids. This remains an important source of systematic errors for weak lensing density reconstruction in galaxy surveys and for supernovae observations, and may be the cause of the reported extra scatter of field supernovae located on the edge of voids compared to those in clusters.

  20. Malignant cerebral swelling following cranioplasty.

    PubMed

    Honeybul, S; Damodaran, O; Lind, C R P; Lee, G

    2016-07-01

    Over the past few years there have been a number of case reports and small cohort studies that have described so called "malignant" cerebral swelling following an uneventful cranioplasty procedure. The pathophysiology remains to be established however it has been suggested that it may be related to a combination of failure of autoregulation and the use of closed vacuum suction drainage. The current study presents three further patients who had had a decompressive hemicraniectomy for ischaemic stroke. If decompressive craniectomy is utilised in the management of neurological emergencies, close attention and wider reporting of this type of complication is required not only to focus attention on possible management strategies, but also to determine which patients are at most risk of this devastating complication. PMID:27189792

  1. SuperLig Ion Exchange Resin Swelling and Buoyancy Study

    SciTech Connect

    Hassan, N.M.

    2000-07-27

    The objective of this study was to achieve a fundamental understanding of SuperLig resin swelling and shrinking characteristics, which lead to channeling and early breakthrough during loading cycles. The density of salt solution that causes resin floating was also determined to establish a limit for operation. Specific tests performed include (a) pH dependence, (b) ionic strength dependence and (c) buoyancy effect vs. simulant composition.

  2. The growth and coalescence of ellipsoidal voids in plane strain under combined shear and tension

    NASA Astrophysics Data System (ADS)

    Scheyvaerts, F.; Onck, P. R.; Tekogˇlu, C.; Pardoen, T.

    2011-02-01

    New extensions of a model for the growth and coalescence of ellipsoidal voids based on the Gurson formalism are proposed in order to treat problems involving shear and/or voids axis not necessarily aligned with the main loading direction, under plane strain loading conditions. These extensions are motivated and validated using 3D finite element void cell calculations with overall plane strain enforced in one direction. The starting point is the Gologanu model dealing with spheroidal void shape. A void rotation law based on homogenization theory is coupled to this damage model. The predictions of the model closely agree with the 3D cell calculations, capturing the effect of the initial void shape and orientation on the void rotation rate. An empirical correction is also introduced for the change of the void aspect ratio in the plane transverse to the main axis of the void departing from its initially circular shape. This correction is needed for an accurate prediction of the onset of coalescence. Next, a new approach is proposed to take strain hardening into account within the Thomason criterion for internal necking, avoiding the use of strain hardening-dependent fitting parameters. The coalescence criterion is generalized to any possible direction of the coalescence plane and void orientation. Finally, the model is supplemented by a mathematical description of the final drop of the stress carrying capacity during coalescence. The entire model is developed for plane strain conditions, setting the path to a 3D extension. After validation of the model, a parametric study addresses the effect of shear on the ductility of metallic alloys for a range of microstructural and flow parameters, under different stress states. In general, the presence of shear, for identical stress triaxiality, decreases the ductility, partly explaining recent experimental results obtained in the low stress triaxiality regime.

  3. Modeling of voids in colloidal plasmas.

    PubMed

    Akdim, M R; Goedheer, W J

    2002-01-01

    A two-dimensional fluid model for a dusty argon plasma in which the plasma and dust parameters are solved self-consistently, is used to study the behavior of voids, i.e., dust-free regions inside dust clouds. These voids appear in plasma crystal experiments performed under microgravity conditions. The ion drag force turns out to be the most promising driving force behind these voids. The contribution of the thermophoretic force, driven by the temperature gradient induced by gas heating from ion-neutral collisions, can be neglected in the quasineutral center of the plasma.

  4. Neutron Imaging Calibration to Measure Void Fraction

    SciTech Connect

    Geoghegan, Patrick J; Bilheux, Hassina Z; Sharma, Vishaldeep; Fricke, Brian A

    2015-01-01

    Void fraction is an intuitive parameter that describes the fraction of vapor in a two-phase flow. It appears as a key variable in most heat transfer and pressure drop correlations used to design evaporating and condensing heat exchangers, as well as determining charge inventory in refrigeration systems. Void fraction measurement is not straightforward, however, and assumptions on the invasiveness of the measuring technique must be made. Neutron radiography or neutron imaging has the potential to be a truly non-invasive void fraction measuring technique but has until recently only offered qualitative descriptions of two-phase flow, in terms of flow maldistributions, for example. This paper describes the calibration approach necessary to employ neutron imaging to measure steady-state void fraction. Experiments were conducted at the High Flux Isotope Reactor (HFIR) Cold Guide 1D neutron imaging facility at Oak Ridge National Laboratory (ORNL), Oak Ridge, TN, USA.

  5. Using Digital Radiography To Image Liquid Nitrogen in Voids

    NASA Technical Reports Server (NTRS)

    Cox, Dwight; Blevins, Elana

    2007-01-01

    Digital radiography by use of (1) a field-portable x-ray tube that emits low-energy x rays and (2) an electronic imaging x-ray detector has been found to be an effective technique for detecting liquid nitrogen inside voids in thermal-insulation panels. The technique was conceived as a means of investigating cryopumping (including cryoingestion) as a potential cause of loss of thermal insulation foam from space-shuttle external fuel tanks. The technique could just as well be used to investigate cryopumping and cryoingestion in other settings. In images formed by use of low-energy x-rays, one can clearly distinguish between voids filled with liquid nitrogen and those filled with gaseous nitrogen or other gases. Conventional film radiography is of some value, but yields only non-real-time still images that do not show time dependences of levels of liquids in voids. In contrast, the present digital radiographic technique yields a succession of images in real time at a rate of about 10 frames per second. The digitized images can be saved for subsequent analysis to extract data on time dependencies of levels of liquids and, hence, of flow paths and rates of filling and draining. The succession of images also amounts to a real-time motion picture that can be used as a guide to adjustment of test conditions.

  6. Counting voids to probe dark energy

    NASA Astrophysics Data System (ADS)

    Pisani, Alice; Sutter, P. M.; Hamaus, Nico; Alizadeh, Esfandiar; Biswas, Rahul; Wandelt, Benjamin D.; Hirata, Christopher M.

    2015-10-01

    We show that the number of observed voids in galaxy redshift surveys is a sensitive function of the equation of state of dark energy. Using the Fisher matrix formalism, we find the error ellipses in the w0-wa plane when the equation of state of dark energy is assumed to be of the form wCPL(z )=w0+waz /(1 +z ) . We forecast the number of voids to be observed with the ESA Euclid satellite and the NASA WFIRST mission, taking into account updated details of the surveys to reach accurate estimates of their power. The theoretical model for the forecast of the number of voids is based on matches between abundances in simulations and the analytical prediction. To take into account the uncertainties within the model, we marginalize over its free parameters when calculating the Fisher matrices. The addition of the void abundance constraints to the data from Planck, HST and supernova survey data noticeably tighten the w0-wa parameter space. We, thus, quantify the improvement in the constraints due to the use of voids and demonstrate that the void abundance is a sensitive new probe for the dark energy equation of state.

  7. Measuring the Properties of Void Galaxies in Environmental COntext (ECO) using RESOLVE

    NASA Astrophysics Data System (ADS)

    Florez, Jonathan; Berlind, Andreas A.; Moffett, Amanda J.; Gonzalez, Roberto; Eckert, Kathleen D.; Kannappan, Sheila; Resolve

    2015-01-01

    We measure the environmental dependence of multiple galaxy properties inside the Environmental COntext survey focusing primarily on void galaxies for this project. We define void galaxies to be ~5% of galaxies having the lowest local density, where density is determined using the Nth nearest neighbor method. We examine the stellar mass, color, fractional stellar mass growth rate (FSMGR), fractional gas mass determined from a photometric gas fraction relation calibrated with the RESOLVE survey, and morphology distributions of the void galaxy population and compare them to those of galaxies in other large-scale structures (such as filaments or clusters). First, we show that our void galaxies typically have lower stellar masses than galaxies in denser environments, and they display the properties expected of a lower stellar mass population: they have late-types, are bluer, have higher FSMGR, and are more gas rich. Since color, star-formation, gas content, and morphology all correlate with stellar mass, we therefore move on to control for stellar mass and investigate the extent to which void galaxies are different at fixed mass. We show that void galaxies are indeed bluer and slightly more star forming at fixed stellar mass than galaxies in other environments. We also show that the ratio of blue early types to red early types is higher inside voids than in any other environment.

  8. Thermal stability of interface voids in Cu grain boundaries with molecular dynamic simulations

    NASA Astrophysics Data System (ADS)

    Xydou, A.; Parviainen, S.; Aicheler, M.; Djurabekova, F.

    2016-09-01

    By means of molecular dynamic simulations, the stability of cylindrical voids is examined with respect to the diffusion bonding procedure. To do this, the effect of grain boundaries between the grains of different crystallographic orientations on the void closing time was studied at high temperatures from 0.7 up to 0.94 of the bulk melting temperature ({{T}\\text{m}} ). The diameter of the voids varied from 3.5 to 6.5 nm. A thermal instability occurring at high temperatures at the surface of the void placed in a grain boundary triggered the eventual closure of the void at all examined temperatures. The closing time has an exponential dependence on the examined temperature values. A model based on the defect diffusion theory is developed to predict the closing time for voids of macroscopic size. The diffusion coefficient within the grain boundaries is found to be overall higher than the diffusion coefficient in the region around the void surface. The activation energy for the diffusion in the grain boundary is calculated based on molecular dynamic simulations. This value agrees well with the experimental given in the Ashby maps for the creep in copper via Coble GB diffusion.

  9. Cluster-Void Degeneracy Breaking: Dark Energy, Planck, and the Largest Cluster and Void

    NASA Astrophysics Data System (ADS)

    Sahlén, Martin; Zubeldía, Íñigo; Silk, Joseph

    2016-03-01

    Combining galaxy cluster and void abundances breaks the degeneracy between mean matter density {{{Ω }}}{{m}} and power-spectrum normalization {σ }8. For the first time for voids, we constrain {{{Ω }}}{{m}}=0.21+/- 0.10 and {σ }8=0.95+/- 0.21 for a flat Λ CDM universe, using extreme-value statistics on the claimed largest cluster and void. The Planck-consistent results detect dark energy with two objects, independently of other dark energy probes. Cluster-void studies are also complementary in scale, density, and nonlinearity, and are of particular interest for testing modified-gravity models.

  10. Thermal stress induced voids in nanoscale copper interconnects by in-situ TEM heating

    NASA Astrophysics Data System (ADS)

    An, Jin Ho

    Stress induced void formation in Cu interconnects, due to thermal stresses generated during the processing of semiconductors, is an increasing reliability issue in the semiconductor industry as Cu interconnects are being downscaled to follow the demand for faster chip speed. In this work, 1.8 micron and 180 nm wide Cu interconnects, fabricated by Freescale Semiconductors, were subjected to thermal cycles, in-situ in the TEM, to investigate the stress relaxation mechanisms as a function of interconnect linewidth. The experiments show that the 1.8 micron Cu interconnect lines relax the thermal stresses through dislocation nucleation and motion while the Cu interconnect 180 nm lines exhibit void formation. Void formation in 180 nm lines occurs predominantly at triple junctions where the Ta diffusion barrier meets a Cu grain boundary. In order to understand void formation in 180 nm lines, the grain orientation and local stresses are determined. In particular, Nanobeam Diffraction (NBD) in the TEM is used to obtain the diffraction pattern of each grain, from which the crystal orientation is evaluated by the ACT (Automated Crystallography for TEM) software. In addition, 2D Finite Element Method (FEM) simulations are performed using the Object Oriented Finite Modeling (OOF2) software to correlate grain orientation with local stresses, and consequently void formation. According to the experimental and simulation results obtained, void formation in 180nm Cu interconnects does not seem to be solely dependent on local stresses, but a combination of diffusion paths available, stress gradients and possibly the presence of defects. In addition, based on the in-situ TEM observations, void growth seems to occur through grain boundary and/or interfacial diffusion. However, in-situ STEM observations of fully opened voids post-failure show pileup of material at the Cu grain surfaces. This means that surface or interface diffusion is also very active during void growth in the presence

  11. 38 CFR 3.207 - Void or annulled marriage.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Void or annulled marriage... Void or annulled marriage. Proof that a marriage was void or has been annulled should consist of: (a... marriage void, together with such other evidence as may be required for a determination. (b) Annulled....

  12. 38 CFR 3.207 - Void or annulled marriage.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2012-07-01 2012-07-01 false Void or annulled marriage... Void or annulled marriage. Proof that a marriage was void or has been annulled should consist of: (a... marriage void, together with such other evidence as may be required for a determination. (b) Annulled....

  13. 38 CFR 3.207 - Void or annulled marriage.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2014-07-01 2014-07-01 false Void or annulled marriage... Void or annulled marriage. Proof that a marriage was void or has been annulled should consist of: (a... marriage void, together with such other evidence as may be required for a determination. (b) Annulled....

  14. 38 CFR 3.207 - Void or annulled marriage.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2013-07-01 2013-07-01 false Void or annulled marriage... Void or annulled marriage. Proof that a marriage was void or has been annulled should consist of: (a... marriage void, together with such other evidence as may be required for a determination. (b) Annulled....

  15. 38 CFR 3.207 - Void or annulled marriage.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Void or annulled marriage... Void or annulled marriage. Proof that a marriage was void or has been annulled should consist of: (a... marriage void, together with such other evidence as may be required for a determination. (b) Annulled....

  16. Effects of void band orientation and crystallographic anisotropy on void growth and coalescence

    NASA Astrophysics Data System (ADS)

    Nemcko, Michael J.; Li, Jing; Wilkinson, David S.

    2016-10-01

    The effects of void band orientation and crystallographic anisotropy on void growth and linkage have been investigated. 2D model materials were fabricated by laser drilling a band of holes into the gage section of sheet tensile samples using various orientation angles with respect to the tensile axis normal. Both copper and magnesium sheets have been studied in order to examine the role of crystallographic anisotropy on the void growth and linkage processes. The samples were pulled in uniaxial tension inside the chamber of an SEM, enabling a quantitative assessment of the growth and linkage processes. The void band orientation angle has a significant impact on the growth and linkage of the holes in copper. As the void band orientation angle is increased from 0° to 45°, the processes of coalescence and linkage are delayed to higher strain values. Furthermore, the mechanism of linkage changes from internal necking to one dominated by shear localization. In contrast, the void band orientation does not have a significant impact on the void growth and linkage processes in magnesium. Void growth in these materials occurs non-uniformly due to interactions between the holes and the microstructure. The heterogeneous nature of deformation in magnesium makes it difficult to apply a coalescence criterion based on the void dimensions. Furthermore, the strain at failure does not show a relationship with the void band orientation angle. Failure associated with twin and grain boundaries interrupts the plastic growth of the holes and causes rapid fracture. Therefore, the impact of the local microstructure outweighs the effects of the void band orientation angle in this material.

  17. Void-containing materials with tailored Poisson's ratio

    NASA Astrophysics Data System (ADS)

    Goussev, Olga A.; Richner, Peter; Rozman, Michael G.; Gusev, Andrei A.

    2000-10-01

    Assuming square, hexagonal, and random packed arrays of nonoverlapping identical parallel cylindrical voids dispersed in an aluminum matrix, we have calculated numerically the concentration dependence of the transverse Poisson's ratios. It was shown that the transverse Poisson's ratio of the hexagonal and random packed arrays approached 1 upon increasing the concentration of voids while the ratio of the square packed array along the principal continuation directions approached 0. Experimental measurements were carried out on rectangular aluminum bricks with identical cylindrical holes drilled in square and hexagonal packed arrays. Experimental results were in good agreement with numerical predictions. We then demonstrated, based on the numerical and experimental results, that by varying the spatial arrangement of the holes and their volume fraction, one can design and manufacture voided materials with a tailored Poisson's ratio between 0 and 1. In practice, those with a high Poisson's ratio, i.e., close to 1, can be used to amplify the lateral responses of the structures while those with a low one, i.e., close to 0, can largely attenuate the lateral responses and can therefore be used in situations where stringent lateral stability is needed.

  18. The Cosmically Depressed: Life, Sociology and Identity of Voids

    NASA Astrophysics Data System (ADS)

    van de Weygaert, R.; Platen, E.; Tigrak, E.; Hidding, J.; van der Hulst, J. M.; Aragón-Calvo, M. A.; Stanonik, K.; van Gorkom, J. H.

    2010-10-01

    In this contribution we review and discuss several aspects of Cosmic Voids, as a background for our void galaxy project (accompanying paper by Stanonik et al.). Voids are a major component of the large scale distribution of matter and galaxies in the Universe. Following a sketch of the general characteristics of void formation and evolution, we describe the influence of the environment on their development and structure and the characteristic hierarchical buildup of the cosmic void population. In order to be able to study the resulting tenuous void substructure and the galaxies populating the interior of voids, we subsequently set out to describe our parameter free tessellation-based watershed void finding technique. It allows us to trace the outline, shape and size of voids in galaxy redshift surveys. The application of this technique enables us to find galaxies in the deepest troughs of the cosmic galaxy distribution, and has formed the basis of our void galaxy program.

  19. THE METALLICITY OF VOID DWARF GALAXIES

    SciTech Connect

    Kreckel, K.; Groves, B.; Croxall, K.; Pogge, R. W.; Van de Weygaert, R.

    2015-01-01

    The current ΛCDM cosmological model predicts that galaxy evolution proceeds more slowly in lower density environments, suggesting that voids are a prime location to search for relatively pristine galaxies that are representative of the building blocks of early massive galaxies. To test the assumption that void galaxies are more pristine, we compare the evolutionary properties of a sample of dwarf galaxies selected specifically to lie in voids with a sample of similar isolated dwarf galaxies in average density environments. We measure gas-phase oxygen abundances and gas fractions for eight dwarf galaxies (M{sub r} > –16.2), carefully selected to reside within the lowest density environments of seven voids, and apply the same calibrations to existing samples of isolated dwarf galaxies. We find no significant difference between these void dwarf galaxies and the isolated dwarf galaxies, suggesting that dwarf galaxy chemical evolution proceeds independent of the large-scale environment. While this sample is too small to draw strong conclusions, it suggests that external gas accretion is playing a limited role in the chemical evolution of these systems, and that this evolution is instead dominated mainly by the internal secular processes that are linking the simultaneous growth and enrichment of these galaxies.

  20. Cosmic Voids and Void Lensing in the Dark Energy Survey Science Verification Data

    DOE PAGESBeta

    Sánchez, C.; Clampitt, J.; Kovacs, A.; Jain, B.; García-Bellido, J.; Nadathur, S.; Gruen, D.; Hamaus, N.; Huterer, D.; Vielzeuf, P.; et al

    2016-10-26

    Galaxies and their dark matter halos populate a complicated filamentary network around large, nearly empty regions known as cosmic voids. Cosmic voids are usually identified in spectroscopic galaxy surveys, where 3D information about the large-scale structure of the Universe is available. Although an increasing amount of photometric data is being produced, its potential for void studies is limited since photometric redshifts induce line-of-sight position errors of ~50 Mpc/h or more that can render many voids undetectable. In this paper we present a new void finder designed for photometric surveys, validate it using simulations, and apply it to the high-quality photo-zmore » redMaGiC galaxy sample of the Dark Energy Survey Science Verification (DES-SV) data. The algorithm works by projecting galaxies into 2D slices and finding voids in the smoothed 2D galaxy density field of the slice. Fixing the line-of-sight size of the slices to be at least twice the photo- z scatter, the number of voids found in these projected slices of simulated spectroscopic and photometric galaxy catalogs is within 20% for all transverse void sizes, and indistinguishable for the largest voids of radius ~70 Mpc/h and larger. The positions, radii, and projected galaxy profiles of photometric voids also accurately match the spectroscopic void sample. Applying the algorithm to the DES-SV data in the redshift range 0.2 < z < 0.8 , we identify 87 voids with comoving radii spanning the range 18-120 Mpc/h, and carry out a stacked weak lensing measurement. With a significance of 4.4σ, the lensing measurement confirms the voids are truly underdense in the matter field and hence not a product of Poisson noise, tracer density effects or systematics in the data. In conclusion, it also demonstrates, for the first time in real data, the viability of void lensing studies in photometric surveys.« less

  1. Molecular accessibility in solvent swelled coal

    SciTech Connect

    Kispert, L.D.

    1992-11-01

    To expand the information base on molecular accessibility in solvent swelled coal, Argonne Premium Coal Samples (APCS) were swelled in polar, basic solvents before and after moisture loss and upon air oxidation. So far studies have been reported on the changes in pore size distribution as a function of temperature when polar basic swelling solvents are used. Additional studies employing EPR spin probe techniques performed on the breaking up of the hydrogen bonding between bedding planes were later confirmed by magnetic resonance imaging at Argonne National Lab and the University of Illinois.

  2. Molecular accessibility in solvent swelled coal

    SciTech Connect

    Kispert, L.D.

    1990-11-01

    Research continued on the swelling of coal. Changes in the size and number distribution of the accessible regions in five Argonne Premium Coal Samples (APCS No.3, No.4, No.5, No.6, and No.8) upon swelling with the solvents, cyclohexane, toluene, nitrobenzene and pyridine were examined by an EPR spin probe method. It was found that as the basicity of the solvent increased the number and length of the cylindrical pores increased with decreasing rank. The number of cylindrical pores also increased with oxygen content (with decreasing rank) suggesting a destruction of the hydrogen-bond network upon swelling with pyridine. 6 refs.

  3. Swelling of whey and egg white protein hydrogels with stranded and particulate microstructures.

    PubMed

    Li, Hui; Zhao, Lei; Chen, Xiao Dong; Mercadé-Prieto, Ruben

    2016-02-01

    Swelling of protein hydrogels in alkaline conditions strongly depends on the gel microstructure. Stranded transparent gels swell as predicted using a modified Flory-Rehner model with the net protein charge. Particulate opaque gels swell very differently, with a sudden increase at a narrow pH range. Its swelling is not controlled by the protein charge, but by the destruction of the non-covalent interactions. Comparable dissolution thresholds, one with pH and another with the degree of swelling, are observed in both types of microstructures. These conclusions are valid for both whey protein isolate (WPI) gels and egg white gels, suggesting that they are universal for all globular proteins that can form such microscructures. Differences are observed, however, from the prevalent chemical crosslinks in each protein system. Non-covalent interactions dominate WPI gels; when such interactions are destroyed at pH≥11.5 the gels swell extensively and eventually dissolve. In egg white gels, the higher degree of disulphide crosslinking allows extensive swelling when non-covalent interactions are destroyed, but dissolution only occurs at pH≥13 when covalent crosslinks are cleaved. The current study highlights that the microstructure of protein hydrogels, a unique particularity of protein systems compared to other synthetic hydrogels, defines swelling.

  4. The dependence of irradiation creep in austenitic alloys on displacement rate and helium to dpa ratio

    SciTech Connect

    Garner, F.A.; Toloczko, M.B.; Grossbeck, M.L.

    1998-03-01

    Before the parametric dependencies of irradiation creep can be confidently determined, analysis of creep data requires that the various creep and non-creep strains be separated, as well as separating the transient, steady-state, and swelling-driven components of creep. When such separation is attained, it appears that the steady-state creep compliance, B{sub o}, is not a function of displacement rate, as has been previously assumed. It also appears that the formation and growth of helium bubbles under high helium generation conditions can lead to a significant enhancement of the irradiation creep coefficient. This is a transient influence that disappears as void swelling begins to dominate the total strain, but this transient can increase the apparent creep compliance by 100--200% at relatively low ({le}20) dpa levels.

  5. Kinematics of the Local cosmic void

    NASA Astrophysics Data System (ADS)

    Nasonova, O. G.; Karachentsev, I. D.

    2011-03-01

    Available data on the distances and radial velocities of galaxies are systematized in order to study the distribution of peculiar velocities in neighborhoods of the Local cosmic void lying in the direction of the Aquila and Hercules constellations. A sample of 1056 galaxies is used, with distances measured in terms of the luminosity of the tip of the red giant branch (TRGB), the luminosity of the cepheids, the luminosity of type 1a supernovae, surface brightness fluctuations (SBF), and the Tully-Fisher relation. The amplitude of the outflow velocity of the galaxies is found to be ˜300 km/s. The average number density of galaxies inside the void is roughly a factor of five lower than the average outside it. The Local void population is characterized by lower luminosities and later morphological types, with medians of M B = - 15m.7 and T=8 (Sdm), respectively.

  6. From Voids to Yukawaballs And Back

    SciTech Connect

    Land, V.; Goedheer, W. J.

    2008-09-07

    When dust particles are introduced in a radio-frequency discharge under micro-gravity conditions, usually a dust free void is formed due to the ion drag force pushing the particles away from the center. Experiments have shown that it is possible to close the void by reducing the power supplied to the discharge. This reduces the ion density and with that the ratio between the ion drag force and the opposing electric force. We have studied the behavior of a discharge with a large amount of dust particles (radius 3.4 micron) with our hydrodynamic model, and simulated the closure of the void for conditions similar to the experiment. We also approached the formation of a Yukawa ball from the other side, starting with a discharge at low power and injecting batches of dust, while increasing the power to prevent extinction of the discharge. Eventually the same situation could be reached.

  7. Void coalescence within periodic clusters of particles

    NASA Astrophysics Data System (ADS)

    Thomson, C. I. A.; Worswick, M. J.; Pilkey, A. K.; Lloyd, D. J.

    2003-01-01

    The effect of particle clustering on void damage rates in a ductile material under triaxial loading conditions is examined using three-dimensional finite element analysis. An infinite material containing a regular distribution of clustered particles is modelled using a unit cell approach. Three discrete particles are introduced into each unit cell while a secondary population of small particles within the surrounding matrix is represented using the Gurson-Tvergaard-Needleman (GTN) constitutive equations. Deformation strain states characteristic of sheet metal forming are considered; that is, deep drawing, plane strain and biaxial stretching. Uniaxial tensile stress states with varying levels of superimposed hydrostatic tension are also examined. The orientation of a particle cluster with respect to the direction of major principal loading is shown to significantly influence failure strains. Coalescence of voids within a first-order particle cluster (consisting of three particles) is a stable event while collapse of inter-cluster ligaments leads to imminent material collapse through void-sheeting.

  8. Precision cosmology defeats void models for acceleration

    SciTech Connect

    Moss, Adam; Zibin, James P.; Scott, Douglas

    2011-05-15

    The suggestion that we occupy a privileged position near the center of a large, nonlinear, and nearly spherical void has recently attracted much attention as an alternative to dark energy. Putting aside the philosophical problems with this scenario, we perform the most complete and up-to-date comparison with cosmological data. We use supernovae and the full cosmic microwave background spectrum as the basis of our analysis. We also include constraints from radial baryonic acoustic oscillations, the local Hubble rate, age, big bang nucleosynthesis, the Compton y distortion, and for the first time include the local amplitude of matter fluctuations, {sigma}{sub 8}. These all paint a consistent picture in which voids are in severe tension with the data. In particular, void models predict a very low local Hubble rate, suffer from an ''old age problem,'' and predict much less local structure than is observed.

  9. Optimizing Voided Piezoelectric Polymers For Acoustic Sensors

    NASA Astrophysics Data System (ADS)

    Arvelo, Juan I.

    2009-07-01

    Polymer piezoelectric materials offer lower density and more flexibility than piezoelectric ceramics for applications where rugged and lightweight acoustic sensors are required. This paper discusses constraints imposed by material stiffness and dielectric constants and aims to derive a generalized closed-form solution for optimizing charged foamed polymers. Optimized solutions are reached in the limits of very large and small void fraction and permittivity ratio. The permittivity ratio is the ratio of the dielectric constants of the polymer and the material that fills the voids. Demonstrations indicate that, in the oblique asymptote, the optimized void fraction becomes equivalent to the permittivity ratio. This effort was conducted under the auspices of the Undersea Warfare Business Area (UWBA) Independent Research & Development (IRAD) Board of the Johns Hopkins University Applied Physics Laboratory (JHU/APL).

  10. A rare cause of lateral facial swelling.

    PubMed

    Mohanty, Sujata; Gulati, Ujjwal; Vandana; Singh, Sapna

    2014-01-01

    A case of chronic, recurrent and asymptomatic facial swelling in a young male is presented. Swelling extended from lower midface to upper lateral neck and right commissure to anterior massetric border. History, clinical signs and symptoms and examination pointed towards the benign nature of the swelling. Fine-needle aspiration cytology tapered the diagnostic possibilities to a salivary cyst or pseudocyst. Ultrasonography identified the lesion to contain echogenic fluid with irregular borders. "Tail sign" was absent on contrast magnetic resonance imaging, excluding the involvement of the sublingual gland. Surgical excision of the lesion was done along with submandibular gland as both were in continuity via a bottle-neck tract. Final histopathological diagnosis was that of the submandibular gland extravasation phenomenon. As per the best of our knowledge, it is the first case report of a submandibular gland extravasation causing swelling in a retrograde direction onto the face. PMID:25593883

  11. A rare cause of lateral facial swelling

    PubMed Central

    Mohanty, Sujata; Gulati, Ujjwal; Vandana; Singh, Sapna

    2014-01-01

    A case of chronic, recurrent and asymptomatic facial swelling in a young male is presented. Swelling extended from lower midface to upper lateral neck and right commissure to anterior massetric border. History, clinical signs and symptoms and examination pointed towards the benign nature of the swelling. Fine-needle aspiration cytology tapered the diagnostic possibilities to a salivary cyst or pseudocyst. Ultrasonography identified the lesion to contain echogenic fluid with irregular borders. “Tail sign” was absent on contrast magnetic resonance imaging, excluding the involvement of the sublingual gland. Surgical excision of the lesion was done along with submandibular gland as both were in continuity via a bottle-neck tract. Final histopathological diagnosis was that of the submandibular gland extravasation phenomenon. As per the best of our knowledge, it is the first case report of a submandibular gland extravasation causing swelling in a retrograde direction onto the face. PMID:25593883

  12. Swelling of lignites in organic solvents

    SciTech Connect

    R.G. Makitra; D.V. Bryk

    2008-10-15

    Data on the swelling of Turkish lignites can be summarized using linear multiparameter equations that take into account various properties of solvents. Factors responsible for the amounts of absorbed solvents are the basicity and cohesion energy density of the solvents.

  13. Molecular accessibility in solvent swelled coal

    SciTech Connect

    Kispert, L.D.

    1991-01-01

    The EPR-spin probe method was used to study the swelling of covalently cross-linked 2%, 4%, 6%, 8% and 12% polystyrene-divinyl benzene copolymers, used as models of APCS coal structural elements. The results were compared with swelling studies on APCS coals and confirmed results showing that coal was polymeric, that it had covalent cross-links increasing with rank, that it was structurally anisotropic, and that its swelling was anisotropic. The low temperature swelling of Argonne Premium Coal Samples using solvents of varying polarity was investigated. The variation in the shape of the pore was followed as a function of temperature and swelling solvent polarity. This change in pore structure was attributed to break-up of the hydrogen bonding network in coal by polar solvents. The modification in pore shape from spherical to cylindrical was attributed to anisotropy in hydrogen bond densities. The structural changes in coal pores that occur when APCS coal is dehydrated prior to swelling with polar solvents has been determined. These changes are different from those that occur in the absence of prior dehydration. Most impressive is the huge change that occurs in lignite coal (Beulah-Zap). It appears that this coal has collapsed upon dehydration preventing any spin probe from being trapped in the dehydrated lignite upon swelling. Various sized probes have been studied. A study on the variation in the hydrogen bonding character of the pore wall as the coals are swelled with various polar solvents has also been completed. A statistical analysis of the data has been completed to determine important trends in the data. 9 refs.

  14. Swelling kinetics of tea in hot water.

    PubMed

    Joshi, Bhushan S; Farakte, Raosaheb A; Yadav, Geeta U; Patwardhan, Ashwin W; Singh, Gurmeet

    2016-01-01

    In this study, the swelling kinetics of individual tea particles as well as bed of tea granules were investigated for different types of teas. The swelling experiments involved image analysis and volume measurements of tea particles. Each individual particle shows different swelling characteristics. Separating funnels and cylindrical columns of varying sizes were used to study the changes in volume of tea bed. Swelling in separating funnel was observed to be more than that in column. The effect of temperature, particle size, bed height and vessel diameter were investigated. The extent as well as the rate of swelling is found to increase with rise in temperature (60 to 80 °C) and reduction in particle size. A decrease in swelling is observed with increase in bed height as well as decrease in vessel diameter and vice a versa. About 70 to 75 % swelling occurs in the first 40 to 45 s. Two empirical models viz. Weibull and Peleg were used to fit the experimental data. The rate parameters obtained for a sample T5 at different temperatures were in the range of 0.012 to 0.016. The volume changes of all the teas were compared with their elution behavior, by measuring the absorbance of a diluted sample of brew at 272 nm. The activation energies for the process of tea swelling calculated for T1 (1.2 mm), T5 (2.2 mm) and T5 (0.72 mm) were 14.156, 8.37 and 13.42 kJ/mol respectively. PMID:26787951

  15. An unusual case of acute periorbital swelling.

    PubMed

    Torretta, Sara; Brevi, Alessandra; Pagani, Davide; Pignataro, Lorenzo

    2014-01-01

    Periorbital swelling is frequently encountered in ear, nose, and throat practices and, as it may be secondary to acute sinusitis, delayed diagnosis may lead to significant morbidity. We describe the case of a 24-year-old man with acute ethmoid-maxillary sinusitis and ipsilateral facial swelling particularly involving the periorbital area. We also discuss the workup that led to the formulation of an unusual diagnosis.

  16. Secretory vesicle swelling by atomic force microscopy.

    PubMed

    Cho, Sang-Joon; Jena, Bhanu P

    2006-01-01

    The swelling of secretory vesicles has been implicated in exocytosis, but the underlying mechanism of vesicle swelling remained unknown. Earlier studies from our laboratory demonstrated the association of the alpha-subunit of heterotrimeric GTP-binding protein G(alphai3) with zymogen granule membrane and implicated its involvement in vesicle swelling. Mas7, an active mastoparan analog known to stimulate Gi proteins, was found to stimulate the GTPase activity of isolated zymogen granules and cause swelling. Increase in vesicle size in the presence of GTP, NaF, and Mas7 were irreversible and found to be KCl sensitive. However, Ca2+ had no effect on zymogen granule size. Taken together, these results indicated that zymogen granules, the membrane-bound secretory vesicles in exocrine pancreas, swell in response to GTP mediated by a G(alphai3) protein. Subsequently, our studies demonstrated that the water channel aquaporin-1 (AQP1) is also present at the zymogen granule membrane and participates in rapid GTP-induced and G(alphai3)-mediated vesicular water gating and swelling. Isolated zymogen granules exhibit low basal water permeability. However, exposure of granules to GTP results in a marked potentiation of water entry. Treatment of zymogen granules with the known water channel inhibitor Hg2+ is accompanied by a reversible loss in both the basal and GTP-stimulable water entry and vesicle swelling. Introduction of AQP1-specific antibody raised against the carboxy-terminal domain of AQP1 blocked GTP-stimulable swelling of vesicles. Our results demonstrate that AQPI associated at the zymogen granule membrane is involved in basal GTP-induced and G(alphai3)-mediated rapid gating of water into zymogen granules of the exocrine pancreas.

  17. Swelling kinetics of tea in hot water.

    PubMed

    Joshi, Bhushan S; Farakte, Raosaheb A; Yadav, Geeta U; Patwardhan, Ashwin W; Singh, Gurmeet

    2016-01-01

    In this study, the swelling kinetics of individual tea particles as well as bed of tea granules were investigated for different types of teas. The swelling experiments involved image analysis and volume measurements of tea particles. Each individual particle shows different swelling characteristics. Separating funnels and cylindrical columns of varying sizes were used to study the changes in volume of tea bed. Swelling in separating funnel was observed to be more than that in column. The effect of temperature, particle size, bed height and vessel diameter were investigated. The extent as well as the rate of swelling is found to increase with rise in temperature (60 to 80 °C) and reduction in particle size. A decrease in swelling is observed with increase in bed height as well as decrease in vessel diameter and vice a versa. About 70 to 75 % swelling occurs in the first 40 to 45 s. Two empirical models viz. Weibull and Peleg were used to fit the experimental data. The rate parameters obtained for a sample T5 at different temperatures were in the range of 0.012 to 0.016. The volume changes of all the teas were compared with their elution behavior, by measuring the absorbance of a diluted sample of brew at 272 nm. The activation energies for the process of tea swelling calculated for T1 (1.2 mm), T5 (2.2 mm) and T5 (0.72 mm) were 14.156, 8.37 and 13.42 kJ/mol respectively.

  18. Including swell-shrink dynamics in dual-permeability numerical modeling of preferential water flow and solute transport in soils

    NASA Astrophysics Data System (ADS)

    Coppola, Antonio; Comegna, Alessandro; Gerke, Horst; Basile, Angelo

    2015-04-01

    The classical dual-permeability approach introduced by Gerke and van Genuchten for modeling water flow and solute transport in porous media with preferential flow pathways, was extended to account for shrinking effects on macropore and matrix domain hydraulic properties. Conceptually, the soil is treated as a dual-permeability bulk porous medium consisting of two dynamic interacting pore domains (1) the fracture (from shrinkage) pore domain and (2) the aggregate (interparticles plus structural) or matrix pore domain, respectively. The model assumes that the swell-shrink dynamics is represented by the inversely proportional volume changes of the fracture and matrix domains, while the overall porosity of the total soil, and hence the layer thickness, remains constant. Swell-shrink dynamics was incorporated in the model by either changing the coupled domain-specific hydraulic properties according to the shrinkage characteristics of the matrix, or partly by allowing the fractional contribution of the two domains to change with the pressure head. As a first step, the hysteresis in the swell-shrink dynamics was not included. We also assumed that the aggregate behavior and its hydraulic properties depend only on the average aggregate water content and not on its internal real distribution. Compared to the rigid approach, the combined effect of the changing weight and that of the void ratio on the hydraulic properties in the shrinking approach induce much larger and deeper water and solute transfer from the fractures to the matrix during wetting processes. The analysis shows a systematic underestimation of the wetting front propagation times, as well as of the solute travel times and concentrations when the volume of the aggregate domain is assumed to remain constant. The combined and interacting effects of the dynamic weight and the evolution of matrix pressure head in the shrinking approach is responsible for a bimodal behavior of the water exchange term, which in turn

  19. Topology and dark energy: testing gravity in voids.

    PubMed

    Spolyar, Douglas; Sahlén, Martin; Silk, Joe

    2013-12-13

    Modified gravity has garnered interest as a backstop against dark matter and dark energy (DE). As one possible modification, the graviton can become massive, which introduces a new scalar field--here with a Galileon-type symmetry. The field can lead to a nontrivial equation of state of DE which is density and scale dependent. Tension between type Ia supernovae and Planck could be reduced. In voids, the scalar field dramatically alters the equation of state of DE, induces a soon-observable gravitational slip between the two metric potentials, and develops a topological defect (domain wall) due to a nontrivial vacuum structure for the field.

  20. Finding high-redshift voids using Lyman α forest tomography

    NASA Astrophysics Data System (ADS)

    Stark, Casey W.; Font-Ribera, Andreu; White, Martin; Lee, Khee-Gan

    2015-11-01

    We present a new method of finding cosmic voids using tomographic maps of Lyα forest flux. We identify cosmological voids with radii of 2-12 h-1 Mpc in a large N-body simulation at z = 2.5, and characterize the signal of the high-redshift voids in density and Lyα forest flux. The void properties are similar to what has been found at lower redshifts, but they are smaller and have steeper radial density profiles. Similarly to what has been found for low-redshift voids, the radial velocity profiles have little scatter and agree very well with the linear theory prediction. We run the same void finder on an ideal Lyα flux field and tomographic reconstructions at various spatial samplings. We compare the tomographic map void catalogues to the density void catalogue and find good agreement even with modest-sized voids (r > 6 h-1 Mpc). Using our simple void-finding method, the configuration of the ongoing COSMOS Lyman Alpha Mapping And Tomography Observations (CLAMATO) survey covering 1 deg2 would provide a sample of about 100 high-redshift voids. We also provide void-finding forecasts for larger area surveys, and discuss how these void samples can be used to test modified gravity models, study high-redshift void galaxies, and to make an Alcock-Paczynski measurement. To aid future work in this area, we provide public access to our simulation products, catalogues, and sample tomographic flux maps.

  1. The view from the boundary: a new void stacking method

    NASA Astrophysics Data System (ADS)

    Cautun, Marius; Cai, Yan-Chuan; Frenk, Carlos S.

    2016-04-01

    We introduce a new method for stacking voids and deriving their profile that greatly increases the potential of voids as a tool for precision cosmology. Given that voids are distinctly non-spherical and have most of their mass at their edge, voids are better described relative to their boundary rather than relative to their centre, as in the conventional spherical stacking approach. The boundary profile is obtained by computing the distance of each volume element from the void boundary. Voids can then be stacked and their profiles computed as a function of this boundary distance. This approach enhances the weak lensing signal of voids, both shear and convergence, by a factor of 2 when compared to the spherical stacking method. It also results in steeper void density profiles that are characterized by a very slow rise inside the void and a pronounced density ridge at the void boundary. The resulting boundary density profile is self-similar when rescaled by the thickness of the density ridge, implying that the average rescaled profile is independent of void size. The boundary velocity profile is characterized by outflows in the inner regions whose amplitude scales with void size, and by a strong inflow into the filaments and walls delimiting the void. This new picture enables a straightforward discrimination between collapsing and expanding voids both for individual objects as well as for stacked samples.

  2. Structure within thin epoxy films revealed by solvent swelling: A neutron reflectivity study

    SciTech Connect

    KENT,MICHAEL S.; YIM,HYUN; MCNAMARA,WILLIAM FRERE; IVKOV,R.; SATIJA,S.; MAJEWSKI,J.

    2000-03-02

    The focus of this work is the structure within highly crosslinked, two component epoxy films. The authors examine variations in crosslink density within thin epoxy films on silicon substrates by solvent swelling. The method is based on the fact that the equilibrium volume fraction of a swelling solvent is strongly dependent upon the local crosslink density. The authors examine the volume fraction profile of the good solvent nitrobenzene through the epoxy films by neutron reflection. Isotopic substitution is used to provide contrast between the epoxy matrix and the swelling solvent.

  3. Patterned dual pH-responsive core-shell hydrogels with controllable swelling kinetics and volumes.

    PubMed

    Plunkett, Kyle N; Moore, Jeffrey S

    2004-08-01

    Dual pH-responsive core-shell hydrogels containing both a vinyl pyridine component and a 2-dimethylaminoethyl methacrylate component were prepared using an in situ photopolymerization process. Complementary photomasks were utilized to prepare hydrogels with core/shell volume ratios of 2:1, 1:1, and 1:2. Depending on the location of each polymer component, dramatically different swelling profiles were achieved. Selective swelling of the shell followed by the core components allowed the hydrogel to expand with the usual kinetics; however, by switching the location of each polymer component and swelling the core first, swelling rates decreased by over 1 order of magnitude and were dependent on the shell component's volume. The ability to pattern core/shell volumes also provided the ability to fabricate hydrogels that possess a constant maximum diameter but different cutoff points between its first and its second transition volumes. These materials may be of interest for controlled release applications. PMID:15274549

  4. "Dark energy" in the Local Void

    NASA Astrophysics Data System (ADS)

    Villata, M.

    2012-05-01

    The unexpected discovery of the accelerated cosmic expansion in 1998 has filled the Universe with the embarrassing presence of an unidentified "dark energy", or cosmological constant, devoid of any physical meaning. While this standard cosmology seems to work well at the global level, improved knowledge of the kinematics and other properties of our extragalactic neighborhood indicates the need for a better theory. We investigate whether the recently suggested repulsive-gravity scenario can account for some of the features that are unexplained by the standard model. Through simple dynamical considerations, we find that the Local Void could host an amount of antimatter (˜5×1015 M ⊙) roughly equivalent to the mass of a typical supercluster, thus restoring the matter-antimatter symmetry. The antigravity field produced by this "dark repulsor" can explain the anomalous motion of the Local Sheet away from the Local Void, as well as several other properties of nearby galaxies that seem to require void evacuation and structure formation much faster than expected from the standard model. At the global cosmological level, gravitational repulsion from antimatter hidden in voids can provide more than enough potential energy to drive both the cosmic expansion and its acceleration, with no need for an initial "explosion" and dark energy. Moreover, the discrete distribution of these dark repulsors, in contrast to the uniformly permeating dark energy, can also explain dark flows and other recently observed excessive inhomogeneities and anisotropies of the Universe.

  5. Healing Voids In Interconnections In Integrated Circuits

    NASA Technical Reports Server (NTRS)

    Cuddihy, Edward F.; Lawton, Russell A.; Gavin, Thomas

    1989-01-01

    Unusual heat treatment heals voids in aluminum interconnections on integrated circuits (IC's). Treatment consists of heating IC to temperature between 200 degrees C and 400 degrees C, holding it at that temperature, and then plunging IC immediately into liquid nitrogen. Typical holding time at evaluated temperature is 30 minutes.

  6. Simulation of void formation in interconnect lines

    NASA Astrophysics Data System (ADS)

    Sheikholeslami, Alireza; Heitzinger, Clemens; Puchner, Helmut; Badrieh, Fuad; Selberherr, Siegfried

    2003-04-01

    The predictive simulation of the formation of voids in interconnect lines is important for improving capacitance and timing in current memory cells. The cells considered are used in wireless applications such as cell phones, pagers, radios, handheld games, and GPS systems. In backend processes for memory cells, ILD (interlayer dielectric) materials and processes result in void formation during gap fill. This approach lowers the overall k-value of a given metal layer and is economically advantageous. The effect of the voids on the overall capacitive load is tremendous. In order to simulate the shape and positions of the voids and thus the overall capacitance, the topography simulator ELSA (Enhanced Level Set Applications) has been developed which consists of three modules, a level set module, a radiosity module, and a surface reaction module. The deposition process considered is deposition of silicon nitride. Test structures of interconnect lines of memory cells were fabricated and several SEM images thereof were used to validate the corresponding simulations.

  7. Void fraction instrument acceptance test procedure

    SciTech Connect

    Pearce, K.L.

    1994-09-15

    This acceptance test procedure (ATP) was written to test the void fraction instrument (VFI) and verify that the unit is ready for field service. The procedure verifies that the mechanical and electrical features (not specifically addressed in the software ATP) and software alarms are operating as designed.

  8. Overcoming confinement limited swelling in hydrogel thin films using supramolecular interactions.

    PubMed

    Wiener, Clinton G; Weiss, R A; Vogt, Bryan D

    2014-09-21

    The thin film behavior of poly(N-isopropylacrylamide-stat-2-(N-ethylperfluorooctane sulfonamido)ethyl acrylate) (NIPAAm-stat-FOSA) based hydrogels containing 5 mol% FOSA was elucidated using quartz crystal microbalance with dissipation (QCM-D) in combination with spectroscopic ellipsometry (SE) through examination of the lower critical solution temperature (LCST) and temperature dependent swelling for (dry) thicknesses ranging from 10 nm to 121 nm. For all thin films measured, the LCST was shown to slightly increase (>3 °C) in comparison to that of the bulk sample. However for these films, the increase in LCST was statistically identical, irrespective of thickness. Surprisingly, the volumetric swelling of the hydrogel in thin films, even at temperatures less than the LCST, was similar (within 20%) to the volumetric swelling of the bulk hydrogel, despite the expected significant decrease associated with the hydrogel being constrained by the substrate as predicted by one dimensional Flory-Rehner theory. We attribute this enhancement in swelling compared to theoretical expectations to the ability of the hydrophobic crosslinks to re-arrange under stress, which provides a mechanism to alleviate the decreased dimensionality imposed by the substrate; this mechanism is consistent with a large hysteresis in the swelling when cycling between 35 °C and 5 °C. Unlike the LCST, the swelling ratio increases with decreasing film thickness. At low temperatures (below the LCST), the volume swelling ratio increased from 3.9 to 4.9, while at temperatures above the LCST the swelling ratio increased from 1.5 to 2.5 when the film thickness decreased from 121 nm to 10 nm. The combination of facile processing through solution casting without the need for additional crosslinking chemistry and limited thickness dependent variation of swelling and LCST behavior in these physically crosslinked hydrogels makes these materials attractive for applications requiring thermoresponsive soft

  9. BetaVoid: molecular voids via beta-complexes and Voronoi diagrams.

    PubMed

    Kim, Jae-Kwan; Cho, Youngsong; Laskowski, Roman A; Ryu, Seong Eon; Sugihara, Kokichi; Kim, Deok-Soo

    2014-09-01

    Molecular external structure is important for molecular function, with voids on the surface and interior being one of the most important features. Hence, recognition of molecular voids and accurate computation of their geometrical properties, such as volume, area and topology, are crucial, yet most popular algorithms are based on the crude use of sampling points and thus are approximations even with a significant amount of computation. In this article, we propose an analytic approach to the problem using the Voronoi diagram of atoms and the beta-complex. The correctness and efficiency of the proposed algorithm is mathematically proved and experimentally verified. The benchmark test clearly shows the superiority of BetaVoid to two popular programs: VOIDOO and CASTp. The proposed algorithm is implemented in the BetaVoid program which is freely available at the Voronoi Diagram Research Center (http://voronoi.hanyang.ac.kr). PMID:24677176

  10. The Void Galaxy Survey: Morphology and Star Formation Properties of Void Galaxies

    NASA Astrophysics Data System (ADS)

    Beygu, Burcu; Kreckel, Kathryn; van der Hulst, Thijs; Peletier, Reynier; Jarrett, Tom; van de Weygaert, Rien; van Gorkom, Jacqueline H.; Aragón-Calvo, Miguel

    2016-10-01

    We present the structural and star formation properties of 59 void galaxies as part of the Void Galaxy Survey (VGS). Our aim is to study in detail the physical properties of these void galaxies and study the effect of the void environment on galaxy properties. We use Spitzer 3.6μ and B-band imaging to study the morphology and color of the VGS galaxies. For their star formation properties, we use Hα and GALEX near-UV imaging. We compare our results to a range of galaxies of different morphologies in higher density environments. We find that the VGS galaxies are in general disk dominated and star forming galaxies. Their star formation rates are, however, often less than 1 M⊙ yr-1. There are two early-type galaxies in our sample as well. In re versus MB parameter space, VGS galaxies occupy the same space as dwarf irregulars and spirals.

  11. Molecular accessibility in solvent swelled coal

    SciTech Connect

    Kispert, L.D.

    1991-08-01

    Research continued on the determination of pore size and number distribution changes after swelling the coal samples with various solvents. A paper has just been submitted to the journal Fuel on the Low temperature Swelling of Argonne Premium Coal samples using solvents of varying polarity. The variation in the shape of the pore was followed as a function of temperature and swelling solvent polarity. This change in pore structure was attributed to break-up of the hydrogen bonding network in coal by polar solvents. The modification in pore shape from spherical to cylindrical was attributed to anisotropy in hydrogen bond densities. A copy of this paper has been attached to this report. Wojciech Sady has determine the structural changes in the pores that occur when APCS coal is dehydrated prior to swelling with polar solvents. These changes are different from those that occur in the absence of prior dehydration. He has also completed a study on the variation in the hydrogen bonding character of the pore wall as the coals are swelled with various polar solvents. A statistical analysis of the data is currently underway to determine important trends in his data. 9 refs.

  12. Morphing of geometric composites via residual swelling.

    PubMed

    Pezzulla, Matteo; Shillig, Steven A; Nardinocchi, Paola; Holmes, Douglas P

    2015-08-01

    Understanding and controlling the shape of thin, soft objects has been the focus of significant research efforts among physicists, biologists, and engineers in the last decade. These studies aim to utilize advanced materials in novel, adaptive ways such as fabricating smart actuators or mimicking living tissues. Here, we present the controlled growth-like morphing of 2D sheets into 3D shapes by preparing geometric composite structures that deform by residual swelling. The morphing of these geometric composites is dictated by both swelling and geometry, with diffusion controlling the swelling-induced actuation, and geometric confinement dictating the structure's deformed shape. Building on a simple mechanical analog, we present an analytical model that quantitatively describes how the Gaussian and mean curvatures of a thin disk are affected by the interplay among geometry, mechanics, and swelling. This model is in excellent agreement with our experiments and numerics. We show that the dynamics of residual swelling is dictated by a competition between two characteristic diffusive length scales governed by geometry. Our results provide the first 2D analog of Timoshenko's classical formula for the thermal bending of bimetallic beams - our generalization explains how the Gaussian curvature of a 2D geometric composite is affected by geometry and elasticity. The understanding conferred by these results suggests that the controlled shaping of geometric composites may provide a simple complement to traditional manufacturing techniques. PMID:26076671

  13. Swelling and Contraction of Corn Mitochondria 1

    PubMed Central

    Stoner, C. D.; Hanson, J. B.

    1966-01-01

    A survey has been made of the properties of corn mitochondria in swelling and contraction. The mitochondria swell spontaneously in KCl but not in sucrose. Aged mitochondria will swell rapidly in sucrose if treated with citrate or EDTA. Swelling does not impair oxidative phosphorylation if bovine serum albumin is present. Contraction can be maintained or initiated with ATP + Mg or an oxidizable substrate, contraction being more rapid with the substrate. Magnesium is not required for substrate powered contraction. Contraction powered by ATP is accompanied by the release of phosphate. Oligomycin inhibits both ATP-powered contraction and the release of phosphate. However, it does not affect substrate-powered contraction. Substrate powered contraction is inhibited by electron-transport inhibitors. The uncoupler, carbonyl cyanide m-chlorophenyl hydrazone, accelerates swelling and inhibits both ATP-and substrate-powered contraction. However, the concentrations required are well in excess of those required to produce uncoupling and to accelerate adenosine triphosphatase; the concentrations required inhibit respiration in a phosphorylating medium. Phosphate is a very effective inhibitor of succinate-powered contraction. Neither oligomycin nor Mg affects the phosphate inhibition. Phosphate is less inhibitory with the ATP-powered contraction. The results are discussed in terms of a hypothesis that contraction is associated with a nonphosphorylated high energy intermediate of oxidative phosphorylation. Images PMID:16656248

  14. Swell-Dissipation Function for Wave Models

    NASA Astrophysics Data System (ADS)

    Babanin, A.

    2012-04-01

    In the paper, we will investigate swell attenuation due to production of turbulence by the wave orbital motion. Theoreticaly, potential waves cannot generate the vortex motion, but the scale considerations indicate that if the steepness of waves is not too small, the Reynolds number can exceed the critical values. This means that in presence of initial non-potential disturbances the orbital velocities can generate the vortex motion and turbulence. This problem was investigated by laboratory means, numerical simulations and field observations. As a sink of wave energy, such dissipation is small in presence of wave breaking, but is essential for swell. Swell prediction by spectral wave models is often poor, but is important for offshore and maritime industry, and across a broad range of oceanographic and air-sea interaction applications. Based on the research of wave-induced turbulence, new swell-dissipation function is proposed. It agrees well with satellite observations of long-distance swell propagation and has been employed and tested in spectral wave models.

  15. Theoretical basis for an anomalous temperature coefficient in swelling pressure of rabbit corneal stroma.

    PubMed Central

    Kwok, L S; Klyce, S D

    1990-01-01

    In the rabbit corneal stroma, the swelling pressure, P, has been reported to have an anomalous (negative) temperature coefficient, alpha P, contradicting traditional Donnan swelling theory. A parallel-plate, diffuse double layer Gouy-Chapman model was used to resolve this discrepancy. The present model incorporates the possibility that surface charge, sigma, is temperature dependent. It is shown that negative, zero, or positive coefficients of swelling pressure change with temperature are not mutually exclusive conditions, but can be attributed to the same underlying mechanism. For likely values of alpha P(range -7 x 10(-3) K-1 to +3.2 x 10(-3)K-1), the effective stromal charge has a negative temperature dependency, or dln sigma/dT less than 0. The present formalism is robust against variation in assumed alpha P, and is able to simultaneously satisfy the known values of swelling pressure, its thermal dependency, and stromal charge. These results implicate significant coulombic forces behind P. Predicted stromal surface charge is approximately 0.01 Cm-2. The predictions were confirmed with macrocontinuum Donnan swelling theory, suggesting that Donnan osmotic swelling is the principal macroscopic component of P. PMID:2306510

  16. Phenomenological force and swelling models for rechargeable lithium-ion battery cells

    NASA Astrophysics Data System (ADS)

    Oh, Ki-Yong; Epureanu, Bogdan I.; Siegel, Jason B.; Stefanopoulou, Anna G.

    2016-04-01

    Three phenomenological force and swelling models are developed to predict mechanical phenomena caused by Li-ion intercalation: a 1-D force model, a 1st order relaxation model, and a 3-D swelling model. The 1-D force model can estimate the Li-ion intercalation induced force for actual pack conditions with preloads. The model incorporates a nonlinear elastic stiffness to capture the mechanical consequences of Li-ion intercalation swelling. The model also separates the entire state of charge range into three regions considering phase transitions. The 1st order relaxation model predicts dynamic swelling during relaxation periods. A coefficient of relaxation is estimated from dynamic and quasi-static swelling at operational conditions. The 3-D swelling model predicts the swelling shape on the battery surface for all states of charge. This model introduces an equivalent modulus of elasticity, which is dependent on the state of charge, to capture material transformations of the electrodes, and the orthotropic expansion of the jellyroll in a direction perpendicular to the electrode surfaces. Considering the simplicity of the measurements and direct physical correlations between stress and strain, the proposed models can enhance battery management systems and power management strategies.

  17. Swelling, mechanical and friction properties of PVA/PVP hydrogels after swelling in osmotic pressure solution.

    PubMed

    Shi, Yan; Xiong, Dangsheng; Liu, Yuntong; Wang, Nan; Zhao, Xiaoduo

    2016-08-01

    The potential of polyvinyl alcohol/polyvinylpyrrolidone (PVA/PVP) hydrogels as articular cartilage replacements was in vitro evaluated by using a macromolecule-based solution to mimic the osmotic environment of cartilage tissue. The effects of osmotic pressure solution on the morphology, crystallinity, swelling, mechanical and friction properties of PVA/PVP hydrogels were investigated by swelling them in non-osmotic and osmotic pressure solutions. The results demonstrated that swelling ratio and equilibrium water content were greatly reduced by swelling in osmotic solution, and the swelling process was found to present pseudo-Fickian diffusion character. The crystallization degree of hydrogels after swelling in osmotic solution increased more significantly when it compared with that in non-osmotic solution. After swelling in osmotic solution for 28days, the compressive tangent modulus and storage modulus of hydrogels were significantly increased, and the low friction coefficient was reduced. However, after swelling in the non-osmotic solution, the compressive tangent modulus and friction coefficient of hydrogels were comparable with those of as-prepared hydrogels. The better material properties of hydrogels in vivo than in vitro evaluation demonstrated their potential application in cartilage replacement.

  18. Influence of different alcohols on the swelling behaviour of hydrogels

    NASA Astrophysics Data System (ADS)

    Althans, Daniel; Langenbach, Kai; Enders, Sabine

    2012-06-01

    The swelling equilibrium of cross-linked poly(N-isopropylacrylamide) (PNIPAAm) hydrogels in alcohol solutions as a function of temperature, alcohol concentration, kind of alcohol (C1OH-C3OH) and gel properties was investigated experimentally. Additionally, the swelling degree as a function of the alcohol concentration was modelled with the UNIQUAC-Free Volume model in combination with the Phantom Network theory. The experiments show that, in pure water, the transition temperature is between 303.15 and 308.15 K depending on the properties of the gel and hence on the polymerization conditions. The transition from a swollen to a shrunken state is caused by the polymeric network and the change of polymer chain localization. In a system with hydrogel + water + alcohol, the swelling degree decreases with increasing alcohol concentration until the shrunken state is reached and increases again by further addition of alcohol at constant temperature. With increasing carbon number of the alcohols, the transition from a swollen to a shrunken state and vice versa shifts to lower concentrations at constant temperature. The use of the UNIQUAC-Free Volume model with Phantom Network theory leads to results in good agreement with the experimental data.

  19. Tank SY-101 void fraction instrument functional design criteria

    SciTech Connect

    McWethy, L.M.

    1994-10-18

    This document presents the functional design criteria for design, analysis, fabrication, testing, and installation of a void fraction instrument for Tank SY-101. This instrument will measure the void fraction in the waste in Tank SY-101 at various elevations.

  20. Assembly of filamentary void galaxy configurations

    NASA Astrophysics Data System (ADS)

    Rieder, Steven; van de Weygaert, Rien; Cautun, Marius; Beygu, Burcu; Portegies Zwart, Simon

    2013-10-01

    We study the formation and evolution of filamentary configurations of dark matter haloes in voids. Our investigation uses the high-resolution Λ cold dark matter simulation CosmoGrid to look for void systems resembling the VGS_31 elongated system of three interacting galaxies that was recently discovered by the Void Galaxy Survey inside a large void in the Sloan Digital Sky Survey galaxy redshift survey. H I data revealed these galaxies to be embedded in a common elongated envelope, possibly embedded in intravoid filament. In the CosmoGrid simulation we look for systems similar to VGS_31 in mass, size and environment. We find a total of eight such systems. For these systems, we study the distribution of neighbour haloes, the assembly and evolution of the main haloes and the dynamical evolution of the haloes, as well as the evolution of the large-scale structure in which the systems are embedded. The spatial distribution of the haloes follows that of the dark matter environment. We find that VGS_31-like systems have a large variation in formation time, having formed between 10 Gyr ago and the present epoch. However, the environments in which the systems are embedded evolved to resemble each other substantially. Each of the VGS_31-like systems is embedded in an intravoid wall, that no later than z = 0.5 became the only prominent feature in its environment. While part of the void walls retain a rather featureless character, we find that around half of them are marked by a pronounced and rapidly evolving substructure. Five haloes find themselves in a tenuous filament of a few h-1 Mpc long inside the intravoid wall. Finally, we compare the results to observed data from VGS_31. Our study implies that the VGS_31 galaxies formed in the same (proto)filament, and did not meet just recently. The diversity amongst the simulated halo systems indicates that VGS_31 may not be typical for groups of galaxies in voids.

  1. Neural stimulation for chronic voiding dysfunctions.

    PubMed

    Elabbady, A A; Hassouna, M M; Elhilali, M M

    1994-12-01

    Neural stimulation of the sacral nerve roots could become an acceptable and promising modality in controlling variable forms of difficult voiding dysfunctions. A total of 50 patients who presented with various forms of voiding dysfunction underwent initial screening by percutaneous nerve evaluation of the S3 nerve root guided by movements of the levator ani and toes. Only 17 patients demonstrated a satisfactory response to percutaneous nerve evaluation and subsequent subchronic wire testing for 4 to 5 days, and they were eligible to enter the study. The studied patients (13 women and 4 men) were classified into 2 groups according to presentation. Group 1 included 8 patients who presented mainly with nonobstructive chronic urinary retention. All 8 patients were on intermittent self-catheterization except 1 with a suprapubic tube. The 9 patients in group 2 mainly presented with other forms of voiding dysfunctions, including pain (suprapubic and perineal), frequency and/or urgency. All patients were neurologically free, and had failed pharmacological and surgical attempts to correct the problems. In both groups radiological and ultrasound evaluations of the urinary tract as well as cystourethroscopy were within normal limits. Urodynamic studies were performed preoperatively and postoperatively. Unilateral S3 foramen implantation was performed on the selected side in all patients. Followup ranged from 3 to 52 months. All patients were followed preoperatively and postoperatively by voiding and itemized symptom score diary as well as a quality of life questionnaire. Each symptom and question were given certain grades that reflect the severity or importance to the patient. The symptom scores and the quality of life questionnaires were analyzed preoperatively and postoperatively. In group 1 voided volume (expressed as a percentage of total bladder capacity) was significantly increased at 6 months (23 +/- 7.5% preoperatively versus 81.9 +/- 7.7% postoperatively, p < 0

  2. Postoperative pectoral swelling after shoulder arthroscopy

    PubMed Central

    ERCIN, ERSIN; BILGILI, MUSTAFA GOKHAN; ONES, HALIL NADIR; KURAL, CEMAL

    2015-01-01

    Fluid extravasation is possibly the most common complication of shoulder arthroscopy. Shoulder arthroscopy can lead to major increases in the compartment pressure of adjacent muscles and this phenomenon is significant when an infusion pump is used. This article describes a case of pectoral swelling due to fluid extravasation after shoulder arthroscopy. A 24-year-old male underwent an arthroscopic Bankart repair for recurrent shoulder dislocation. The surgery was performed in the beach chair position and lasted two hours. At the end of the procedure, the patient was found to have left pectoral swelling. A chest radiography showed no abnormality. Pectoral swelling due to fluid extravasation after shoulder arthroscopy has not previously been documented. PMID:26889473

  3. Swelling of pH-sensitive hydrogels.

    PubMed

    Drozdov, A D; deClaville Christiansen, J

    2015-02-01

    A model is derived for the elastic response of polyelectrolyte gels subjected to unconstrained and constrained swelling. A gel is treated as a three-phase medium consisting of a solid phase (polymer network), solvent (water), and solutes (mobile ions). Transport of solvent and solutes is modeled as their diffusion through the network accelerated by an electric field formed by ions and accompanied by chemical reactions (dissociation of functional groups attached to the chains). Constitutive equations (including the van't Hoff law for ionic pressure and the Henderson-Hasselbach equation for ionization of chains) are derived by means of the free energy imbalance inequality. Good agreement is demonstrated between equilibrium swelling diagrams on several pH-sensitive gels and results of simulation. It is revealed that swelling of polyelectrolyte gels is driven by electrostatic repulsion of bound charges, whereas the effect of ionic pressure is of secondary importance. PMID:25768503

  4. Swelling of p H -sensitive hydrogels

    NASA Astrophysics Data System (ADS)

    Drozdov, A. D.; deClaville Christiansen, J.

    2015-02-01

    A model is derived for the elastic response of polyelectrolyte gels subjected to unconstrained and constrained swelling. A gel is treated as a three-phase medium consisting of a solid phase (polymer network), solvent (water), and solutes (mobile ions). Transport of solvent and solutes is modeled as their diffusion through the network accelerated by an electric field formed by ions and accompanied by chemical reactions (dissociation of functional groups attached to the chains). Constitutive equations (including the van't Hoff law for ionic pressure and the Henderson-Hasselbach equation for ionization of chains) are derived by means of the free energy imbalance inequality. Good agreement is demonstrated between equilibrium swelling diagrams on several pH-sensitive gels and results of simulation. It is revealed that swelling of polyelectrolyte gels is driven by electrostatic repulsion of bound charges, whereas the effect of ionic pressure is of secondary importance.

  5. Swelling and Stress Relaxation in Portland Brownstone

    NASA Astrophysics Data System (ADS)

    Jimenez, I.; Scherer, G.

    2003-04-01

    Portland Brownstone (PB) is an arkose sandstone extensively used in the northeast-ern USA during the nineteenth century. This reddish-brown stone contains a fraction of swelling clays that are thought to contribute to its degradation upon cycles of wet-ting and drying. During drying events, contraction of the drying surface leads to stresses approaching the tensile strength of the stone. However, we have found that the magnitude of these stresses is limited by the ability of the stone to undergo stress relaxation. In this paper we describe novel methods to determine the magnitude of the stresses and the rate at which they develop and relax. We also discuss the influ-ence of surfactants on the magnitude of swelling and the rate of the stress relaxation of PB. The implications of our findings for the understanding of damage due to swelling of clays are discussed.

  6. Analysis of the influence of voids and a crack on the ultimate tensile strength of REBCO bulk superconductor

    NASA Astrophysics Data System (ADS)

    Kasaba, K.; Oshida, Y.; Hokari, T.; Katagiri, K.

    2008-09-01

    Since the high Tc rare-earth based bulk superconductor is subjected to the tensile load in radial and circumferential direction by the Lorentz force generated in the magnetization process, the evaluation of the strength by the tensile test is indispensable. Ultimate tensile strength of the bulk superconductor depends on the defects in each sample. Many artificial specimens containing voids were generated for numerical stress calculations. The distribution of the voids diameter in each artificial specimen was based on the observations of Dy123 containing 25 wt% Dy211 (abbreviated as Dy25). Furthermore, the effect of a center crack superposed to the field of the voids on the strength was analytically evaluated. The strength depends on both the size and the location of the voids. The maximum crack length which has eventually no effect on the strength was evaluated. By the evaluation method proposed in this study, it was found that if there had been no void in the Dy25 bulk sample, the tensile strength could have been estimated to be 63 MPa. The voids increase the stress intensity factor at the crack tip. If there is a crack with 0.16 mm or more in the Dy25 superconductor bulk with the porosity 10%, the fracture may not be originated around a void but at a crack tip.

  7. 21 CFR 1305.28 - Canceling and voiding electronic orders.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Canceling and voiding electronic orders. 1305.28... I AND II CONTROLLED SUBSTANCES Electronic Orders § 1305.28 Canceling and voiding electronic orders. (a) A supplier may void all or part of an electronic order by notifying the purchaser of the...

  8. Extended void merging tree algorithm for self-similar models

    NASA Astrophysics Data System (ADS)

    Russell, Esra

    2014-02-01

    In hierarchical evolution, voids exhibit two different behaviours related with their surroundings and environments, they can merge or collapse. These two different types of void processes can be described by the two-barrier excursion set formalism based on Brownian random walks. In this study, the analytical approximate description of the growing void merging algorithm is extended by taking into account the contributions of voids that are embedded into overdense region(s) which are destined to vanish due to gravitational collapse. Following this, to construct a realistic void merging model that consists of both collapse and merging processes, the two-barrier excursion set formalism of the void population is used. Assuming spherical voids in the Einstein-de Sitter Universe, the void merging algorithm which allows us to consider the two main processes of void hierarchy in one formalism is constructed. In addition to this, the merger rates, void survival probabilities, void size distributions in terms of the collapse barrier and finally, the void merging tree algorithm in the self-similar models are defined and derived.

  9. Void Coalescence Processes Quantified Through Atomistic and Multiscale Simulation

    SciTech Connect

    Rudd, R E; Seppala, E T; Dupuy, L M; Belak, J

    2007-01-12

    Simulation of ductile fracture at the atomic scale reveals many aspects of the fracture process including specific mechanisms associated with void nucleation and growth as a precursor to fracture and the plastic deformation of the material surrounding the voids and cracks. Recently we have studied void coalescence in ductile metals using large-scale atomistic and continuum simulations. Here we review that work and present some related investigations. The atomistic simulations involve three-dimensional strain-controlled multi-million atom molecular dynamics simulations of copper. The correlated growth of two voids during the coalescence process leading to fracture is investigated, both in terms of its onset and the ensuing dynamical interactions. Void interactions are quantified through the rate of reduction of the distance between the voids, through the correlated directional growth of the voids, and through correlated shape evolution of the voids. The critical inter-void ligament distance marking the onset of coalescence is shown to be approximately one void radius based on the quantification measurements used, independent of the initial separation distance between the voids and the strain-rate of the expansion of the system. No pronounced shear flow is found in the coalescence process. We also discuss a technique for optimizing the calculation of fine-scale information on the fly for use in a coarse-scale simulation, and discuss the specific case of a fine-scale model that calculates void growth explicitly feeding into a coarse-scale mechanics model to study damage localization.

  10. An Observational Detection of the Bridge Effect of Void Filaments

    NASA Astrophysics Data System (ADS)

    Shim, Junsup; Lee, Jounghun; Hoyle, Fiona

    2015-12-01

    The bridge effect of void filaments is a phrase coined by Park & Lee to explain the correlations found in a numerical experiment between the luminosity of the void galaxies and the degree of straightness of their host filaments. Their numerical finding implies that a straight void filament provides a narrow channel for the efficient transportation of gas and matter particles from the surroundings into void galaxies. Analyzing the Sloan void catalog constructed by Pan et al., we identify the filamentary structures in void regions and determine the specific size of each void filament as a measure of its straightness. To avoid possible spurious signals caused by Malmquist bias, we consider only those void filaments whose redshifts are in the range 0≤slant z≤slant 0.02 and find a clear tendency that the void galaxies located in the straighter filaments are on average more luminous, which is in qualitative agreement with the numerical prediction. It is also shown that the strength of correlation increases with the number of member galaxies in the void filaments, which can be understood physically on the grounds that the more stretched filaments can connect the dense surroundings even to galaxies located deep in the central parts of the voids. This observational evidence may provide a key clue to the puzzling issue of why the void galaxies have higher specific star formation rates and bluer colors than their wall counterparts.

  11. Swelling of plasma-polymerized tetrafluoroethylene films

    SciTech Connect

    Butler, M.A.; Buss, R.J.; Seager, C.H. )

    1991-11-25

    Swelling of micrometer thick-films of plasma-polymerized tetrafluoroethylene has been measured for a range of solvents using an optical-interferometric technique. For low gas-phase concentrations of the solvent, the swelling is found to correlate with the ionization potential of the solvent. Photo-thermal deflection spectroscopy of the films shows optical absorption in the infrared, which changes with exposure to different solvents. Both of these results suggest weak electron transfer from the solvent to the polymer as the dominant interaction mechanism.

  12. Statistics of voids in hierarchical universes

    NASA Technical Reports Server (NTRS)

    Fry, J. N.

    1986-01-01

    As one alternative to the N-point galaxy correlation function statistics, the distribution of holes or the probability that a volume of given size and shape be empty of galaxies can be considered. The probability of voids resulting from a variety of hierarchical patterns of clustering is considered, and these are compared with the results of numerical simulations and with observations. A scaling relation required by the hierarchical pattern of higher order correlation functions is seen to be obeyed in the simulations, and the numerical results show a clear difference between neutrino models and cold-particle models; voids are more likely in neutrino universes. Observational data do not yet distinguish but are close to being able to distinguish between models.

  13. Process Yields Strong, Void-Free Laminates

    NASA Technical Reports Server (NTRS)

    Bryant, L. E.; Covington, E. W., III; Dale, W. J.; Hall, E. T., Jr; Justice, J. E.; Taylor, E. C.; Wilson, M. L.

    1983-01-01

    Need for lightweight materials as structural components for future space transportation systems stimulated development of systematic method for manufacturing a polyimide/graphite composite. Laminates manufactured by process are void-free, exhibit excellent thermo-oxidative stability up to 315 degrees C (600 degrees F) and are 40 percent lighter than aluminum. Process is precise, repeatable, and ideally suited for researchers and small-lot producers of composite materials.

  14. Bilayer mass transport model for determining swelling and diffusion in coated, ultrathin membranes.

    PubMed

    Nadermann, Nichole K; Chan, Edwin P; Stafford, Christopher M

    2015-02-18

    Water transport and swelling properties of an ultrathin, selective polyamide layer with a hydrophilic polymer coating, i.e., a polymer bilayer, are studied using quartz crystal microbalance with dissipation (QCM-D). Specifically, QCM-D is used to measure the dynamic and equilibrium change in mass in a series of differential sorption experiments to determine the dependence of the apparent diffusion coefficient and equilibrium swelling of the bilayer as a function of the water vapor activity. To determine transport properties specific to the polyamide layer, sorption kinetics of the bilayer was modeled with a bilayer mass transport model. The swelling and water diffusion coefficients are interpreted according to the Painter-Shenoy polymer network swelling model and the solution-diffusion model, respectively.

  15. X-ray diffraction study of the kinetics of myelin lattice swelling. Effect of divalent cations.

    PubMed Central

    Padrón, R; Mateu, L; Kirschner, D A

    1979-01-01

    The time-course of myelin lattice swelling and its reversal in dissected peripheral nerves was determined by small-angle x-ray diffraction using a position-sensitive proportional detector. The process of swelling can take place either in several hours or in less than 1 h depending on pretreatment of the nerves. The reversal of swelling was always completed within 1 h. The rapid structural transitions involved the disordering of membrane pairs as indicated by the transient appearance of a continuous intensity distribution similar to the membrane pair transform for myelin. The slow transitions involved the gradual replacement of the discrete reflections from the native structure by the reflections from the swollen lattice. Myelin membrane arrays reformed in normal Ringer's solution were much more stable to subsequent swelling than arrays reformed in Ca+2 and Mg+2-free Ringer's. These results suggest that these ions participate in stabilizing the interactions between the external surfaces of adjacent membrane pairs. PMID:122265

  16. A Functional Representation of the Cosmological Reduced Void Probability Distribution as the Fox H Function

    NASA Astrophysics Data System (ADS)

    Andrew, Keith; Smailhodzic, A.; Carini, M.; Barnaby, D.

    2010-01-01

    We use data from the Sloan Digital Sky Survey, the DEEP2 and 2dF Galaxy Redshift surveys and numerical runs of the Gadget II code to analyze the distribution of cosmological voids in the universe similar to the model proposed by Mekjian.1. The Void Probability Function focuses on a scaling model inspired from percolation theory that gives an analytical form for the distribution function. For large redshifts the early universe was smooth and the probability function has a simple mathematical form that mimics the two point correlation results leading to a generalized power law. As various large scale galactic structures emerge in a given simulation a number of relatively empty regions are isolated and characterized as voids based upon number counts in the associated volume. The number density of these regions is such that the universe has a large scale “sponge-like” appearance with voids of all scales permeating the field of observation. For these data sets we examine the range of critical void probability function parameters that give rise to the best fit to the numerical and observational data. Several expressions for the probability distribution differ at the long end tail of the distribution which is sensitive to the Levy index of the distribution. Almost all of the distributions can be expressed as special cases of the Fox H function which has an asymptotic form whose tail depends upon the Levy index. We analyze the Levy index expressions and link them to the Fox H function parameters and to an anomalous diffusion equation that gives rise to the observed LSS void pattern. We wish to thank the Kentucky Space Grant Consortium for providing the NASA grant funding this research 1. Aram Z. Mekjian , Generalized statistical models of voids and hierarchical structure in cosmology, The Astrophysical Journal, 655: 1-10, 2007, arXiv:0712.1217

  17. Subconjuctival Loa loa with Calabar swelling.

    PubMed

    Cho, Hee-Yoon; Lee, Yoon-Jung; Shin, Sun-Young; Song, Hyun-Ouk; Ahn, Myoung-Hee; Ryu, Jae-Sook

    2008-08-01

    Loa loa is unique among the human filariae in that adult worms are occasionally visible during subconjunctival migration. A 29-yr-old African female student, living in Korea for the past 5 yr without ever visiting her home country, presented with acute eyelid swelling and a sensation of motion on the left eyeball. Her symptoms started one day earlier and became worse over time. Examination revealed a threadlike worm beneath the left upper bulbar conjunctiva with mild eyelid swelling as well as painless swelling of the right forearm. Upon exposure to slit-lamp illumination, a sudden movement of the worm toward the fornix was noted. After surgical extraction, parasitologic analysis confirmed the worm to be a female adult Loa loa with the vulva at the extreme anterior end. On blood smear, the microfilariae had characteristic features of Loa loa, including sheath and body nuclei up to the tip of the tail. The patient also showed eosinophilia (37%) measuring 4,100/microL. She took ivermectin (200 microg/kg) as a single dose and suffered from a mild fever and chills for one day. This patient, to the best of our knowledge, is the first case of subconjunctival loiasis with Calabar swelling in Korea. PMID:18756067

  18. Urodynamic assessment of voiding dysfunction and dysfunctional voiding in girls and women.

    PubMed

    Everaert, K; Van Laecke, E; De Muynck, M; Peeters, H; Hoebeke, P

    2000-01-01

    Voiding dysfunction is defined as impaired bladder emptying, and presents with a mixture of lower urinary tract symptoms. Dysfunctional voiding is a condition in which there is a lack of coordination between the sphincter and detrusor during emptying in a patient without overt uropathy or neuropathy. Assessment of voiding dysfunction is important in women and girls in the prevention and treatment of urinary incontinence, retention, urinary tract infection and subsequent kidney damage. Accurate diagnosis is essential in order to select the correct treatment. Screening can be done by history-taking: symptom scores can help to guide the screening. More objective measures are uroflowmetry, ultrasonography and video-urodynamics. The latter is the gold standard for the diagnosis of voiding dysfunction and consists of simultaneous registration of pressure in the bladder and rectum and external sphincter behavior, either by electromyographic recording of pelvic floor activity or by pressure recording at the external sphincter, during the whole bladder cycle of filling and emptying. On fluoroscopy the bladder can be visualized throughout the filling and emptying phase. In dysfunctional voiding, hypertonicity and instability of the external urethral sphincter during filling cystometry and impaired external sphincter relaxation during emptying are pathognomonic findings. Pressure-flow analysis reveals no obstruction and the detrusor contractility is low.

  19. Void fraction and bubble size in a simulated hydraulic jump

    NASA Astrophysics Data System (ADS)

    Witt, Adam; Gulliver, John; Shen, Lian

    2013-11-01

    Two- and three-dimensional numerical simulations of a hydraulic jump are carried out with the open source software package OpenFOAM using a Volume of Fluid numerical method and a realizable k- ɛ turbulence model. Time-averaged air-water properties are obtained over a 15 second sampling time. Void fraction profiles show good agreement with experimental values in the turbulent shear layer. Sauter mean diameter approaches experimental results in the turbulent shear layer, while showing grid dependence down to a uniform computational cell size of 0.625 mm. Three-dimensional results show a minor improvement in the prediction of entrained air compared to two-dimensional results at a multiple of 341 in increased computational time for the chosen grid. Relative error in bubble diameter is similar between two- and three-dimensional simulations. The results indicate a Volume of Fluid, realizable k- ɛ numerical model accurately predicts the void fraction profile when the Sauter mean diameter to grid size ratio surpasses 8. This research was supported by funding from the U.S. Department of Energy, the Hydro Research Foundation, the University of Minnesota and the University of Minnesota Supercomputing Institute.

  20. Void Coalescence Processes Quantified through Atomistic and Multiscale Simulation

    SciTech Connect

    Rudd, R E; Seppala, E T; Dupuy, L M; Belak, J

    2005-12-31

    Simulation of ductile fracture at the atomic scale reveals many aspects of the fracture process including specific mechanisms associated with void nucleation and growth as a precursor to fracture and the plastic deformation of the material surrounding the voids and cracks. Recently we have studied void coalescence in ductile metals using large-scale atomistic and continuum simulations. Here we review that work and present some related investigations. The atomistic simulations involve three-dimensional strain-controlled multi-million atom molecular dynamics simulations of copper. The correlated growth of two voids during the coalescence process leading to fracture is investigated, both in terms of its onset and the ensuing dynamical interactions. Void interactions are quantified through the rate of reduction of the distance between the voids, through the correlated directional growth of the voids, and through correlated shape evolution of the voids. The critical inter-void ligament distance marking the onset of coalescence is shown to be approximately one void radius based on the quantification measurements used, independent of the initial separation distance between the voids and the strain-rate of the expansion of the system. No pronounced shear flow is found in the coalescence process.

  1. Old Stellar Populations of The VGS Void Galaxies

    NASA Astrophysics Data System (ADS)

    Beygu, Burcu; Jarrett, Thomas; Jarrett, Tom; van de Weygaert, Rien; Kreckel, Kathryn; van der Hulst, Thijs; van Gorkom, Jacqueline

    2011-05-01

    Cosmic voids form an essential ingredient of the Cosmic Web and may harbour a systematically different population of galaxies. Largely unaffected by the complex processes modifying galaxies in high-density environments, the pristine and isolated void regions must hold important clues to the intrinsic process of formation and evolution of galaxies. The Void Galaxy Survey (VGS) is a multi-wavelength program to study 60 void galaxies. Each has been selected from the deepest interior regions of identified voids in the SDSS redshift survey on the basis of a unique geometric technique, with no a prior selection of intrinsic properties of the void galaxies. The project intends to study in detail the gas content, star formation history and stellar content, as well as kinematics and dynamics of void galaxies and their companions in a broad sample of void environments. It involves the HI imaging of the gas distribution in each of the VGS galaxies. Amongst its most tantalizing findings is the possible evidence for cold gas accretion in some of the most interesting objects, amongst which are a polar ring galaxy and a filamentary configuration of void galaxies. An essential aspect for understanding the formation and evolution of void galaxies concerns their star formation history. The current IRAC proposal is meant to study the older stellar population of void galaxies to constrain their assembly history.

  2. The sparkling Universe: the coherent motions of cosmic voids

    NASA Astrophysics Data System (ADS)

    Lambas, Diego García; Lares, Marcelo; Ceccarelli, Laura; Ruiz, Andrés N.; Paz, Dante J.; Maldonado, Victoria E.; Luparello, Heliana E.

    2016-01-01

    We compute the bulk motions of cosmic voids, using a Λ cold dark matter numerical simulation considering the mean velocities of the dark matter inside the void itself and that of the haloes in the surrounding shell. We find coincident values of these two measures in the range ˜300-400 km s-1, not far from the expected mean peculiar velocities of groups and galaxy clusters. When analysing the distribution of the pairwise relative velocities of voids, we find a remarkable bimodal behaviour consistent with an excess of both systematically approaching and receding voids. We determine that the origin of this bimodality resides in the void large-scale environment, since once voids are classified into void-in-void (R-type) or void-in-cloud (S-type), R-types are found mutually receding away, while S-types approach each other. The magnitude of these systematic relative velocities account for more than 100 km s-1, reaching large coherence lengths of up to 200 h-1 Mpc . We have used samples of voids from the Sloan Digital Sky Survey Data Release 7 and the peculiar velocity field inferred from linear theory, finding fully consistent results with the simulation predictions. Thus, their relative motion suggests a scenario of a sparkling universe, with approaching and receding voids according to their local environment.

  3. A cosmic watershed: the WVF void detection technique

    NASA Astrophysics Data System (ADS)

    Platen, Erwin; van de Weygaert, Rien; Jones, Bernard J. T.

    2007-09-01

    On megaparsec scales the Universe is permeated by an intricate filigree of clusters, filaments, sheets and voids, the cosmic web. For the understanding of its dynamical and hierarchical history it is crucial to identify objectively its complex morphological components. One of the most characteristic aspects is that of the dominant underdense voids, the product of a hierarchical process driven by the collapse of minor voids in addition to the merging of large ones. In this study we present an objective void finder technique which involves a minimum of assumptions about the scale, structure and shape of voids. Our void finding method, the watershed void finder (WVF), is based upon the watershed transform, a well-known technique for the segmentation of images. Importantly, the technique has the potential to trace the existing manifestations of a void hierarchy. The basic watershed transform is augmented by a variety of correction procedures to remove spurious structure resulting from sampling noise. This study contains a detailed description of the WVF. We demonstrate how it is able to trace and identify, relatively parameter free, voids and their surrounding (filamentary and planar) boundaries. We test the technique on a set of kinematic Voronoi models, heuristic spatial models for a cellular distribution of matter. Comparison of the WVF segmentations of low-noise and high-noise Voronoi models with the quantitatively known spatial characteristics of the intrinsic Voronoi tessellation shows that the size and shape of the voids are successfully retrieved. WVF manages to even reproduce the full void size distribution function.

  4. On the observability of coupled dark energy with cosmic voids

    NASA Astrophysics Data System (ADS)

    Sutter, P. M.; Carlesi, Edoardo; Wandelt, Benjamin D.; Knebe, Alexander

    2015-01-01

    Taking N-body simulations with volumes and particle densities tuned to match the sloan digital sky survey DR7 spectroscopic main sample, we assess the ability of current void catalogues to distinguish a model of coupled dark matter-dark energy from Λ cold dark matter cosmology using properties of cosmic voids. Identifying voids with the VIDE toolkit, we find no statistically significant differences in the ellipticities, but find that coupling produces a population of significantly larger voids, possibly explaining the recent result of Tavasoli et al. In addition, we use the universal density profile of Hamaus et al. to quantify the relationship between coupling and density profile shape, finding that the coupling produces broader, shallower, undercompensated profiles for large voids by thinning the walls between adjacent medium-scale voids. We find that these differences are potentially measurable with existing void catalogues once effects from survey geometries and peculiar velocities are taken into account.

  5. Void asymmetries in the cosmic web: a mechanism for bulk flows

    NASA Astrophysics Data System (ADS)

    Bland-Hawthorn, J.; Sharma, S.

    2016-10-01

    Bulk flows of galaxies moving with respect to the cosmic microwave background are well established observationally and seen in the most recent ΛCDM simulations. With the aid of an idealised Gadget-2 simulation, we show that void asymmetries in the cosmic web can exacerbate local bulk flows of galaxies. The {\\it Cosmicflows-2} survey, which has mapped in detail the 3D structure of the Local Universe, reveals that the Local Group resides in a ``local sheet'' of galaxies that borders a ``local void'' with a diameter of about 40 Mpc. The void is emptying out at a rate of 16 km s-1 Mpc-1. In a co-moving frame, the Local Sheet is found to be moving away from the Local Void at ~ 260 km s-1. Our model shows how asymmetric collapse due to unbalanced voids on either side of a developing sheet or wall can lead to a systematic movement of the sheet. We conjectured that asymmetries could lead to a large-scale separation of dark matter and baryons, thereby driving a dependence of galaxy properties with environment, but we do {\\it not} find any evidence for this effect.

  6. Critical velocities for deflagration and detonation triggered by voids in a REBO high explosive

    SciTech Connect

    Herring, Stuart Davis; Germann, Timothy C; Jensen, Niels G

    2010-01-01

    The effects of circular voids on the shock sensitivity of a two-dimensional model high explosive crystal are considered. We simulate a piston impact using molecular dynamics simulations with a Reactive Empirical Bond Order (REBO) model potential for a sub-micron, sub-ns exothermic reaction in a diatomic molecular solid. The probability of initiating chemical reactions is found to rise more suddenly with increasing piston velocity for larger voids that collapse more deterministically. A void with radius as small as 10 nm reduces the minimum initiating velocity by a factor of 4. The transition at larger velocities to detonation is studied in a micron-long sample with a single void (and its periodic images). The reaction yield during the shock traversal increases rapidly with velocity, then becomes a prompt, reliable detonation. A void of radius 2.5 nm reduces the critical velocity by 10% from the perfect crystal. A Pop plot of the time-to-detonation at higher velocities shows a characteristic pressure dependence.

  7. Investigation of the swelling behaviour of hydrogels in aqueous acid or alkaline solutions

    NASA Astrophysics Data System (ADS)

    Althans, Daniel; Enders, Sabine

    2014-09-01

    For development of tailor made drug delivery systems using poly(N-isopropylacrylamide) hydrogels, the influence of acids and bases added to the aqueous solution on the swelling behaviour as function of concentration, temperature and kind of acid or base were investigated experimentally. The selected acids are formic, acetic, propionic, lactic, succinic, α-ketoglutaric and citric acid. The applied bases are sodium and potassium hydroxide. The swelling behaviour was characterised by the degree of swelling and by the uptake of acids by the hydrogel in the swollen state. In the case of weak acids the properties of the swollen hydrogel as well as the phase transition temperature and phase transition acid concentration depends on the type of acids, whereas the properties of the shrunken state do not depend on the acid used. In the case of strong bases, the properties of the shrunken and swollen state depend on the ionic strength, but not on the base applied.

  8. The Void Galaxy Survey: Galaxy Evolution and Gas Accretion in Voids

    NASA Astrophysics Data System (ADS)

    Kreckel, Kathryn; van Gorkom, Jacqueline H.; Beygu, Burcu; van de Weygaert, Rien; van der Hulst, J. M.; Aragon-Calvo, Miguel A.; Peletier, Reynier F.

    2016-10-01

    Voids represent a unique environment for the study of galaxy evolution, as the lower density environment is expected to result in shorter merger histories and slower evolution of galaxies. This provides an ideal opportunity to test theories of galaxy formation and evolution. Imaging of the neutral hydrogen, central in both driving and regulating star formation, directly traces the gas reservoir and can reveal interactions and signs of cold gas accretion. For a new Void Galaxy Survey (VGS), we have carefully selected a sample of 59 galaxies that reside in the deepest underdensities of geometrically identified voids within the SDSS at distances of ~100 Mpc, and pursued deep UV, optical, Hα, IR, and HI imaging to study in detail the morphology and kinematics of both the stellar and gaseous components. This sample allows us to not only examine the global statistical properties of void galaxies, but also to explore the details of the dynamical properties. We present an overview of the VGS, and highlight key results on the HI content and individually interesting systems. In general, we find that the void galaxies are gas rich, low luminosity, blue disk galaxies, with optical and HI properties that are not unusual for their luminosity and morphology. We see evidence of both ongoing assembly, through the gas dynamics between interacting systems, and significant gas accretion, seen in extended gas disks and kinematic misalignments. The VGS establishes a local reference sample to be used in future HI surveys (CHILES, DINGO, LADUMA) that will directly observe the HI evolution of void galaxies over cosmic time.

  9. The Void Galaxy Survey: photometry, structure and identity of void galaxies

    NASA Astrophysics Data System (ADS)

    Beygu, B.; Peletier, R. F.; van der Hulst, J. M.; Jarrett, T. H.; Kreckel, K.; van de Weygaert, R.; van Gorkom, J. H.; Aragon-Calvo, M. A.

    2016-09-01

    We analyze photometry from deep B-band images of 59 void galaxies in the Void Galaxy Survey (VGS), together with their near-infrared 3.6μm and 4.5μm Spitzer photometry. The VGS galaxies constitute a sample of void galaxies that were selected by a geometric-topological procedure from the SDSS DR7 data release, and which populate the deep interior of voids. Our void galaxies span a range of absolute B-magnitude from {M_B=-15.5} to {M_B=-20}, while at the 3.6μm band their magnitudes range from {M_{3.6}=-18} to {M_{3.6}=-24}. Their B-[3.6] colour and structural parameters indicate these are star forming galaxies. A good reflection of the old stellar population, the near-infrared band photometry also provide a robust estimate of the stellar mass, which for the VGS galaxies we confirm to be smaller than 3 × 1010 M⊙. In terms of the structural parameters and morphology, our findings align with other studies in that our VGS galaxy sample consists mostly of small late-type galaxies. Most of them are similar to Sd-Sm galaxies, although a few are irregularly shaped galaxies. The sample even includes two early-type galaxies, one of which is an AGN. Their Sérsic indices are nearly all smaller than n = 2 in both bands and they also have small half-light radii. In all, we conclude that the principal impact of the void environment on the galaxies populating them mostly concerns their low stellar mass and small size.

  10. Dynamic swelling behavior of interpenetrating polymer networks in response to temperature and pH

    PubMed Central

    Slaughter, Brandon V.; Blanchard, Aaron T.; Maass, Katie F.; Peppas, Nicholas A.

    2015-01-01

    Temperature responsive hydrogels based on ionic polymers exhibit swelling transitions in aqueous solutions as a function of shifting pH and ionic strength, in addition to temperature. Applying these hydrogels to useful applications, particularly for biomedical purposes such as drug delivery and regenerative medicine, is critically dependent on understanding the hydrogel solution responses as a function of all three parameters together. In this work, interpenetrating polymer network (IPN) hydrogels of polyacrylamide and poly(acrylic acid) were formulated over a broad range of synthesis variables using a fractional factorial design, and were examined for equilibrium temperature responsive swelling in a variety of solution conditions. Due to the acidic nature of these IPN hydrogels, usable upper critical solution temperature (UCST) responses for this system occur in mildly acidic environments. Responses were characterized in terms of maximum equilibrium swelling and temperature-triggered swelling using turbidity and gravimetric measurements. Additionally, synthesis parameters critical to achieving optimal overall swelling, temperature-triggered swelling, and sigmoidal temperature transitions for this IPN system were analyzed based on the fractional factorial design used to formulate these hydrogels. PMID:26405349

  11. Swelling and dissolution of cellulose in amine oxide/water systems

    SciTech Connect

    Chanzy, H.; Noe, P.; Paillet, M.; Smith, P.

    1983-01-01

    The swelling behavior and the dissolution process of various cellulosic fibers, both native and regenerated, in N-methylmorpholine N-oxide (MMNO), dimethylethanolamine N-oxide (DMEAO), and mixtures thereof were studied in the presence of various amounts of water. The principal tools in this investigation were optical microscopy and wide-angle X-ray scattering (WAXS). The two amine oxides could either dissolve or only swell cellulose, depending on the water concentration, which was found to be of critical importance. Three domains of water concentration were found important. When only a few percent water was present, cellulose fibers, such as ramie, cotton, rayon, etc., dissolved readily without noticeable swelling in the amine oxide/water system brought above its melting point. At a relatively high water concentration (e.g., 18% w/w for MMNO), the cellulose fibers exhibited an extensive swelling (up to sevenfold increase in the fiber diameter) but no dissolution. In that case, the removal of the swelling agent showed that the initial native cellulose fibers were converted into an unoriented cellulose II structure. With still greater water content (e.g., 20% and more for MMNO or 15% for DMEAO), only partial swelling was observed, and the native cellulose fibers recovered their initial oriented cellulose I structure after removal of the swelling medium. X-ray investigations provided no evidence forthe formation of cellulose/solvent complexes in the swollen fibers. A relatively large decrease of the cellulose I (110) reflection was found in the WAXS patterns of the gels. This is interpreted as due to a preferential cleavage of the cellulose crystals along the corresponding plane when the cellulose fibers are exposed to the swelling forces of the amine oxide/water systems. 29 references, 13 figures, 1 table.

  12. Void fraction system computer software design description

    SciTech Connect

    Gimera, M.

    1995-02-15

    This document describes the software that controls the void fraction instrument. The format of the document may differ from typical Software Design Reports because it was created with a graphical programming language. Hardware is described in Section 2. The purpose of this document is describe the software, so the hardware description is brief. Software is described in Section 3. LabVIEW was used to develop the viscometer software, so Section 3 begins with an introduction to LabVIEW. This is followed by a description of the main program. Finally each Westinghouse developed subVI (sub program) is discussed.

  13. Surgical Management of Male Voiding Dysfunction.

    PubMed

    Mandeville, Jessica; Mourtzinos, Arthur

    2016-06-01

    Benign prostatic hypertrophy (BPH) is a common cause of voiding dysfunction. BPH may lead to bladder outlet obstruction and resultant troublesome lower urinary tract symptoms. Initial management of BPH and bladder outlet obstruction is typically conservative. However, when symptoms are severe or refractory to medical therapy or when urinary retention, bladder stone formation, recurrent urinary tract infections, or upper urinary tract deterioration occur, surgical intervention is often necessary. Numerous options are available for surgical management of BPH ranging from simple office-based procedures to transurethral operative procedures and even open and robotic surgeries. This article reviews the current, most commonly used techniques available for surgical management of BPH. PMID:27261790

  14. Nanometer voids prevent crack growth in polymer thin films

    NASA Astrophysics Data System (ADS)

    Yokoyama, Hideaki; Dutriez, Cedric; Satoh, Kotaro; Kamigaito, Masami

    2007-03-01

    Macroscopic voids initiate cracks and cause catastrophic failure in brittle materials. The effect of micrometer voids in the mechanical properties of polymeric materials was studied in 1980's and 90's with the expectation that such small voids may initiate crazing, the toughening mechanism in polymer solids, similar to dispersed rubber particles widely used in industry. However, the micrometer voids showed only limited resistance against crack growth, and it was concluded that much smaller voids are necessary for the drastic change in mechanical properties. We have recently succeeded the nondestructive introduction of nanometer voids (30--70 nm) in polymeric materials using block copolymer template and carbon dioxide (CO2) by partitioning CO2 in CO2-philic nanodomains of block copolymers. The reduction of Young's modulus with such nanometer voids was minimal (2 to 1 GPa) due to the (short-range) ordered spherical voids. While the unprocessed copolymer films failed in brittle manner at around 2 % of tensile strain, the processed copolymer films with nanometer voids did not break up to at least 60 %. A microscopic observation under strain of the crack tip revealed that the nanometer voids were deformed under strain and directly converted into the networked fibrils near the crack tip similar to crazing and thus prevented the crack growth.

  15. Electrical Resistivity Monitoring of Voids: Results of Dynamic Modeling Experiments

    NASA Astrophysics Data System (ADS)

    Lane, J. W.; Day-Lewis, F. D.; Singha, K.

    2006-05-01

    Remote, non-invasive detection of voids is a challenging problem for environmental and engineering investigations in karst terrain. Many geophysical methods including gravity, electrical, electromagnetic, magnetic, and seismic have potential to detect voids in the subsurface; lithologic heterogeneity and method- specific sources of noise, however, can mask the geophysical signatures of voids. New developments in automated, autonomous geophysical monitoring technology now allow for void detection using differential geophysics. We propose automated collection of electrical resistivity measurements over time. This dynamic approach exploits changes in subsurface electrical properties related to void growth or water-table fluctuation in order to detect voids that would be difficult or impossible to detect using static imaging approaches. We use a series of synthetic modeling experiments to demonstrate the potential of difference electrical resistivity tomography for finding (1) voids that develop vertically upward under a survey line (e.g., an incipient sinkhole); (2) voids that develop horizontally toward a survey line (e.g., a tunnel); and (3) voids that are influenced by changing hydrologic conditions (e.g., void saturation and draining). Synthetic datasets are simulated with a 3D finite-element model, but the inversion assumes a 2D forward model to mimic conventional practice. The results of the synthetic modeling experiments provide insights useful for planning and implementing field-scale monitoring experiments using electrical methods.

  16. Unambiguous voids in Allende chondrules and refractory inclusions

    SciTech Connect

    Murray, J.; Boesenberg, J.S.; Ebel, D.S.

    2003-03-26

    Void space can be caused by thin section preparation. 3-dimensional tomographic analysis, prior to sectioning, shows that several very different types of voids are abundant in Allende meteorite inclusions. Formation models are proposed for each type. Void spaces in the components of chondritic meteorites have received little attention, perhaps due to ambiguities attendant upon their very existence, and also their origin. Computer-aided microtomography allows the 3-dimensional imaging and analysis of void spaces within solid objects. Several striking examples of void spaces, apparently enclosed by solid material, resulted from our observations of large chondrules and CAIs from the Allende (CV3) meteorite. These voids are 'unambiguous' because their existence cannot be ascribed to plucking during sample preparation, as would be the case in traditional 2-dimensional thin section petrography. Although we focus on large objects in Allende, preliminary observations indicate that void spaces are prevalent in chondrules and refractory inclusions in many meteorites. Voids remain ambiguous, however, because their structure and appearance vary between chondrules and CAIs, suggesting there may be different causes of void formation in particular objects. Some voids appear to have formed as a result of dilation during cooling. Others are evidence of hydrothermal leaching on the parent body followed by partial chemical replacement. Alternatively, vapor-mediated leaching and replacement may have occurred in the nebula. Yet another possibility is internal brecciation caused by impact, while the object was still free floating in the nebula, and perhaps still partially molten.

  17. Voiding Dysfunction after Total Mesorectal Excision in Rectal Cancer

    PubMed Central

    Kim, Jae Heon; Noh, Tae Il; Oh, Mi Mi; Park, Jae Young; Lee, Jeong Gu; Um, Jun Won; Min, Byung Wook

    2011-01-01

    Purpose The aim of this study was to assess the voiding dysfunction after rectal cancer surgery with total mesorectal excision (TME). Methods This was part of a prospective study done in the rectal cancer patients who underwent surgery with TME between November 2006 and June 2008. Consecutive uroflowmetry, post-voided residual volume, and a voiding questionnaire were performed at preoperatively and postoperatively. Results A total of 50 patients were recruited in this study, including 28 male and 22 female. In the comparison of the preoperative data with the postoperative 3-month data, a significant decrease in mean maximal flow rate, voided volume, and post-voided residual volume were found. In the comparison with the postoperative 6-month data, however only the maximal flow rate was decreased with statistical significance (P=0.02). In the comparison between surgical methods, abdominoperineal resection patients showed delayed recovery of maximal flow rate, voided volume, and post-voided residual volume. There was no significant difference in uroflowmetry parameters with advances in rectal cancer stage. Conclusions Voiding dysfunction is common after rectal cancer surgery but can be recovered in 6 months after surgery or earlier. Abdominoperineal resection was shown to be an unfavorable factor for postoperative voiding. Larger prospective study is needed to determine the long-term effect of rectal cancer surgery in relation to male and female baseline voiding condition. PMID:22087426

  18. New Statistical Perspective to Link Void Distributions with Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Russell, Esra; Pycke, Jean-Renaud

    2016-07-01

    Voids dominate the total observed volume of the large scale structure and they are very sensitive to their environments which can strongly affect their shape as well their distributions. Therefore the void size distribution functions may play an important role to understand the dynamical processes affecting the structure formation of the Universe Here, using cosmic void data sets of Sutter et al. (2012) generated by galaxy mock catalogs which are tuned to three SDSS main samples, we obtain the size distribution of voids as a three parameter redshift independent log-normal void probability function. We find that the shape of the three parameter void distribution from the mock data samples is strikingly similar to the galaxy log-normal mass distribution obtained from numerical studies. This similarity of void size and galaxy mass distributions may possibly indicate evidence of large scale nonlinear mechanisms affecting both voids and galaxies, such as large scale accretion and tidal effects. Taking into account that all voids we study are generated by galaxy mock catalogs and they show hierarchical structures at different levels, it may be possible that the same nonlinear mechanisms of mass distribution affect the void size distribution.

  19. A SIMPLE GRAVITATIONAL LENS MODEL FOR COSMIC VOIDS

    SciTech Connect

    Chen, Bin; Kantowski, Ronald; Dai, Xinyu

    2015-05-10

    We present a simple gravitational lens model to illustrate the ease of using the embedded lensing theory when studying cosmic voids. It confirms the previously used repulsive lensing models for deep voids. We start by estimating magnitude fluctuations and weak-lensing shears of background sources lensed by large voids. We find that sources behind large (∼90 Mpc) and deep voids (density contrast about −0.9) can be magnified or demagnified with magnitude fluctuations of up to ∼0.05 mag and that the weak-lensing shear can be up to the ∼10{sup −2} level in the outer regions of large voids. Smaller or shallower voids produce proportionally smaller effects. We investigate the “wiggling” of the primary cosmic microwave background (CMB) temperature anisotropies caused by intervening cosmic voids. The void-wiggling of primary CMB temperature gradients is of the opposite sign to that caused by galaxy clusters. Only extremely large and deep voids can produce wiggling amplitudes similar to galaxy clusters, ∼15 μK by a large void of radius ∼4° and central density contrast −0.9 at redshift 0.5 assuming a CMB background gradient of ∼10 μK arcmin{sup −1}. The dipole signal is spread over the entire void area, and not concentrated at the lens center as it is for clusters. Finally, we use our model to simulate CMB sky maps lensed by large cosmic voids. Our embedded theory can easily be applied to more complicated void models and used to study gravitational lensing of the CMB, to probe dark matter profiles, to reduce the lensing-induced systematics in supernova Hubble diagrams, and to study the integrated Sachs–Wolfe effect.

  20. A New Statistical Perspective on the Cosmic Void Distribution

    NASA Astrophysics Data System (ADS)

    Pycke, J.-R.; Russell, E.

    2016-04-01

    In this study, we obtain the size distribution of voids as a three-parameter redshift-independent log-normal void probability function (VPF) directly from the Cosmic Void Catalog (CVC). Although many statistical models of void distributions are based on the counts in randomly placed cells, the log-normal VPF that we obtain here is independent of the shape of the voids due to the parameter-free void finder of the CVC. We use three void populations drawn from the CVC generated by the Halo Occupation Distribution (HOD) Mocks, which are tuned to three mock SDSS samples to investigate the void distribution statistically and to investigate the effects of the environments on the size distribution. As a result, it is shown that void size distributions obtained from the HOD Mock samples are satisfied by the three-parameter log-normal distribution. In addition, we find that there may be a relation between the hierarchical formation, skewness, and kurtosis of the log-normal distribution for each catalog. We also show that the shape of the three-parameter distribution from the samples is strikingly similar to the galaxy log-normal mass distribution obtained from numerical studies. This similarity between void size and galaxy mass distributions may possibly indicate evidence of nonlinear mechanisms affecting both voids and galaxies, such as large-scale accretion and tidal effects. Considering the fact that in this study, all voids are generated by galaxy mocks and show hierarchical structures in different levels, it may be possible that the same nonlinear mechanisms of mass distribution affect the void size distribution.

  1. Morphological effect on swelling behaviour of hydrogel

    SciTech Connect

    Yacob, Norzita; Hashim, Kamaruddin

    2014-02-12

    Hydrogels are hydrophilic polymer networks that are capable of imbibing large amounts of water. In this work, hydrogels prepared from natural and synthetic polymers were irradiated by using electron beam irradiation. The morphology of hydrogel inter-polymeric network (IPN) was investigated using Scanning Electron Microscopy (SEM). The studies reveal correlations between pore sizes of IPN with degree of cross-linking. This relation also has an effect on swelling properties of the hydrogel. The results indicated that hydrogel with smaller pore size, as a result of much dense IPN, would decrease water uptake capacity. Combination of natural and synthetic polymers to form hydrogel affects the pore size and swelling property of the hydrogel as compared to each component of polymer.

  2. Stress Singularities in Swelling Soft Solids

    NASA Astrophysics Data System (ADS)

    Goriely, Alain; Weickenmeier, Johannes; Kuhl, Ellen

    2016-09-01

    When a swelling soft solid is rigidly constrained on all sides except for a circular opening, it will bulge out to expand as observed during decompressive craniectomy, a surgical procedure used to reduce stresses in swollen brains. While the elastic energy of the solid decreases throughout this process, large stresses develop close to the opening. At the point of contact, the stresses exhibit a singularity similar to the ones found in the classic punch indentation problem. Here, we study the stresses generated by swelling and the evolution of the bulging shape associated with this process. We also consider the possibility of damage triggered by zones of either high shear stresses or high fiber stretches.

  3. Morphological effect on swelling behaviour of hydrogel

    NASA Astrophysics Data System (ADS)

    Yacob, Norzita; Hashim, Kamaruddin

    2014-02-01

    Hydrogels are hydrophilic polymer networks that are capable of imbibing large amounts of water. In this work, hydrogels prepared from natural and synthetic polymers were irradiated by using electron beam irradiation. The morphology of hydrogel inter-polymeric network (IPN) was investigated using Scanning Electron Microscopy (SEM). The studies reveal correlations between pore sizes of IPN with degree of cross-linking. This relation also has an effect on swelling properties of the hydrogel. The results indicated that hydrogel with smaller pore size, as a result of much dense IPN, would decrease water uptake capacity. Combination of natural and synthetic polymers to form hydrogel affects the pore size and swelling property of the hydrogel as compared to each component of polymer.

  4. Evaluating the geochemically induced swelling/shrinkage of the near-field host clay rock using a THC model and the diffuse double layer theory

    NASA Astrophysics Data System (ADS)

    Zheng, L.; Liu, H.; Birkholzer, J. T.; Houseworth, J. E.; Sonnenthal, E. L.

    2011-12-01

    One advantage of emplacing nuclear waste in a clay formation is the potential self-sealing capability due to clay swelling. The swelling properties of the near-field host clay rock can be altered due to geochemical factors, including changes in groundwater geochemistry, proportions of exchangeable cations, and swelling clay mineral abundances. The clay host rock can also undergo geochemical changes due to the interaction with the engineered barrier system (EBS) materials. In this paper, coupled thermal, hydrological, and chemical (THC) models are linked with a swelling model based on diffuse double layer (DDL) theory and changes in the swelling properties of clay host rocks in the near field area are evaluated. Findings based on THC simulations using the reaction-transport code TOUGHREACT include: 1) Significant changes in the swelling pressure could be expected depending on various hydrogeologic and geochemical conditions. The change of hydration rate of the EBS (via the adjustment of tortuosity) could have significant effect on the swelling pressure. 2) Geochemically-induced swelling/shrinkage only occurs in the near-field area, within a few meters from the EBS interface. 3) Swelling/shrinkage induced porosity change is generally much smaller than that caused by mineral precipitation/dissolution. 4) The geochemically-induced swelling/shrinkage of host clay rock is the combined effect of variation in the pore water geochemistry, exchangeable cations, and smectite abundance. Neglecting any of these three latter factors might lead to a miscalculation of the geochemically-induced swelling pressure.

  5. A Void Diffusion Model of Granular Flow

    NASA Astrophysics Data System (ADS)

    Rudra, Jayanta; Vieth, Paul

    2009-03-01

    In an earlier paper^1 we derived a nonlinear diffusion equation to describe the dynamics in granular flow based on a Diffusion Void Model (DVM). The equation was successfully used to describe the flow of a homogeneous granular material through the hole of a container under gravity. It also properly described similar flow in the presence of a flat horizontal barrier placed above the hole. Recently, however, we have found out that the above nonlinear equation does not lead to correct static equilibrium. For example, the stability of the free surface of a granular aggregate cannot be described by the equation. The equation also fails to describe, say, how an unstable vertical column of a granular material will change to a stable λ-shaped pile at the angle of repose. In this paper work we derive an equation using an appropriate current density of voids that can explain all the observed dynamical characteristics of a simple granular state. ^1Jayanta K. Rudra and D. C. Hong, Phys. Rev. E47, R1459(1993).

  6. Early voiding dysfunction associated with prostate brachytherapy.

    PubMed

    Wagner; Nag; Young; Bahnson

    2000-12-15

    Introduction: Transperineal prostate brachytherapy is gaining popularity as a treatment for clinically localized carcinoma of the prostate. Very little prospective data exists addressing the issue of complications associated with this procedure. We present an analysis of the early voiding dysfunction associated with prostate brachytherapy. Materials and Methods: Forty-six consecutive patients who underwent Palladium-103 (Pd-103) seed placement for clinically localized prostate carcinoma were evaluated prospectively for any morbidity associated with the procedure. Twenty-three patients completed an International Prostate Symptom Score (IPSS) questionnaire preoperatively, at their first postoperative visit, and at their second postoperative visit. The total IPSS, each of the seven individual components, and the "bother" score were evaluated separately for each visit, and statistical significance was determined. Results: Urinary retention occurred in 7/46 patients (15%). Of these, 5 were able to void spontaneously after catheter removal. One patient is maintained with a suprapubic tube, and one patient is currently on continuous intermittent catheterization. Baseline IPSS was 7.1 and this went to 20.0 at the first postoperative visit (p<0.001). By the second postoperative visit, the IPSS was 8.0. Conclusions: In our experience, prostate brachytherapy for localized carcinoma of the prostate is associated with a 15% catheterization rate and a significant increase in the IPSS (7.1 to 20.0). This increase in the IPSS seems to be self-limited. Patients need to be educated on these issues prior to prostate brachytherapy. PMID:11113369

  7. Swelling of the vesicle is prerequisite for PTH secretion.

    PubMed

    Lim, S K; Kwon, Y H; Song, Y D; Lee, H C; Ryu, K J; Huh, K B; Park, C S

    1996-02-01

    Unlike most secretory cells, high extra cellular calcium inhibits rather than stimulates hormonal secretion in several cells such as parathyroid cells, Juxtaglomerular cells and osteoclast. To gain further insight into the common but unique stimulus-secretion coupling mechanism in these cells, bovine parathyroid slices were incubated in various conditions of Krebs-Ringer (KR) solution containing essential amino acids. Parathyroid cells showed the inverse dependency of secretion on extra cellular calcium concentration as we expected. Ammonium acetate overcame the inhibitory effect of 2.5 mM of calcium and the maximum effect was as much as the five times of the basal value, while there was a little additive effect under 0 mM CaCl2. PTH secretion was biphasic according to the change of extra cellular osmolarity and the lowest response was observed at 300 mOsm/l. In Na-rich KR solution, high concentration of nigericin (> 10(-4)M) completely overcame the inhibitory effect of 2.5 mM CaCl2 and the maximum stimulatory effect was 8 times greater whereas it was only 2 times greater without CaCl2. In K-rich KR solution that abolished the K-gradient between the extra cellular solution and the cytoplasm, the rate of PTH secretion increased, and furthermore the addition of nigericin increased the rate of secretion significantly. The results above suggested that the osmotic swelling of the secretory vesicle in parathyroid cells might promote exocytosis as in Juxtaglomerular cells. We propose that the swelling of the vesicle is also prerequisite for secretion in several cells inhibited paradoxically by Ca++, whatever the signal transduction pathway for swelling of the secretory granules induced by the lowering of Ca++ in cytoplasm are.

  8. A novel random void model and its application in predicting void content of composites based on ultrasonic attenuation coefficient

    NASA Astrophysics Data System (ADS)

    Lin, Li; Zhang, Xiang; Chen, Jun; Mu, Yunfei; Li, Ximeng

    2011-06-01

    A novel two-dimensional random void model (RVM) based on random medium theory and a statistical method is proposed to describe random voids in composite materials. The spatial autocorrelation function and statistical parameters are used to describe the large-scale heterogeneity from the composite matrix and the small-scale heterogeneities of elastic fluctuations from random voids, the values of which are determined by statistical data from microscopic observations of void morphology. A RVM for CFRP (carbon fiber reinforced polymer) composite specimens with void content of 0.03-4.62% is presented. It is found that the geometric morphology of voids from the RVM presents good matches to the microscopic images. Calculations of ultrasonic attenuation coefficients from the RVM at 5 MHz are much closer to the experiments than those from the previous deterministic model. Furthermore, the RVM can also cover abnormal coefficients from unusually large voids, which unpredictably occur during the composite preparation and have a detrimental effect on the strength and mechanical properties of the components. The significant enhancements in description of void morphology and quantitative correlation between void content and ultrasonic attenuation coefficient make this method a good candidate for predicting void content of composite materials non-destructively.

  9. Real-space density profile reconstruction of stacked voids

    NASA Astrophysics Data System (ADS)

    Pisani, Alice; Sutter, P.; Lavaux, G.; Wandelt, B.

    2016-10-01

    Modern surveys allow us to access to high quality large scale structure measurements. In this framework, cosmic voids appear as a new potential probe of Cosmology. We discuss the use of cosmic voids as standard spheres and their capacity to constrain new physics, dark energy and cosmological models. We introduce the Alcock-Paczyński test and its use with voids. We discuss the main difficulties in treating with cosmic voids: redshift-space distortions, the sparsity of data, and peculiar velocities. We present a method to reconstruct the spherical density profiles of void stacks in real space, without redshift-space distortions. We show its application to a toy model and a dark matter simulation; as well as a first application to reconstruct real cosmic void stacks density profiles in real space from the Sloan Digital Sky Survey.

  10. Void alignment and density profile applied to measuring cosmological parameters

    NASA Astrophysics Data System (ADS)

    Dai, De-Chang

    2015-12-01

    We study the orientation and density profiles of the cosmological voids with Sloan Digital Sky Survey (SDSS; Ahn et al.) 10 data. Using voids to test Alcock-Paczynski effect has been proposed and tested in both simulations and actual SDSS data. Previous observations imply that there exist an empirical stretching factor which plays an important role in the voids' orientation. Simulations indicate that this empirical stretching factor is caused by the void galaxies' peculiar velocities. Recently Hamaus et al. found that voids' density profiles are universal and their average velocities satisfy linear theory very well. In this paper, we first confirm that the stretching effect exists using independent analysis. We then apply the universal density profile to measure the cosmological parameters. We find that the void density profile can be a tool to measure the cosmological parameters.

  11. Ductile damage of porous materials with two populations of voids

    NASA Astrophysics Data System (ADS)

    Vincent, Pierre-Guy; Monerie, Yann; Suquet, Pierre

    2008-01-01

    This study is devoted to the modelling of ductile damage in uranium dioxide. This polycrystalline material contains two populations of voids of well separated size. The problem addressed here is the prediction of the effective flow surface of a Gurson material containing randomly oriented oblate voids. The case of spherical voids is considered first and the variational approach of Gurson is generalized by adding a compressible component to his original velocity field. The case of aligned oblate voids is then considered and a suitable generalization of a velocity field due to Gologanu et al. (ASME J. Engrg. Mater. Technol. 116 (1994) 290-297) is proposed. The extension to randomly oriented voids is achieved by averaging over all orientations. In each case, rigorous upper bounds and approximate estimates are derived and compared (in the case of spherical voids) with Finite Element simulations. To cite this article: P.-G. Vincent et al., C. R. Mecanique 336 (2008).

  12. Comparison of compression properties and swelling of beryllium irradiated at various temperatures

    SciTech Connect

    Beeston, J.M.; Miller, L.G.; Wood, E.L. Jr.; Moir, R.W.

    1983-01-01

    A beryllium cylinder irradiated in Experimental Breeder Reactor (EBR-II) for four years at 700 to 760 K to a neutron fluence of 8.13 x 10/sup 22/ n/cm/sup 2/ (total) or 1 x 10/sup 22/ n/cm/sup 2/ (E > 1 MeV) was cut into samples and tested. Yield strength and plastic strain was determined in compression tests at 300, 723, 823 K and after annealing at 1173 K for one hour. The immersion density and helium content were measured on samples. An equation for swelling was derived from the data by regression analysis. The microstructure showed agglomeration of helium in voids or bubbles at the grain boundaries.

  13. Void deformation and breakup in shearing silica glass.

    PubMed

    Chen, Yi-Chun; Nomura, Ken-ichi; Kalia, Rajiv K; Nakano, Aiichiro; Vashishta, Priya

    2009-07-17

    We study shear deformation and breakup of voids in silica glass using molecular dynamics simulations. With an increase in the shear strain, two kinds of defects--threefold-coordinated silicon and nonbridging oxygen atoms--appear as spherical voids deform elastically into ellipsoidal shapes. For shear strains epsilon>15%, nanocracks appear on void surfaces and voids deform plastically into a threadlike structure. Nanocracks are nucleated by the migration of threefold-coordinated Si and nonbridging O on -Si-O-Si-O- rings. For epsilon>40%, the threadlike structures break up into several fragments. PMID:19659293

  14. Quantifying Effects of Voids in Woven Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldsmith, Marlana B.; Sankar, Bhavani V.; Haftka, Raphael T.; Goldberg, Robert K.

    2013-01-01

    Randomness in woven ceramic matrix composite architecture has been found to cause large variability in stiffness and strength. The inherent voids are an aspect of the architecture that may cause a significant portion of the variability. A study is undertaken to investigate the effects of many voids of random sizes and distributions. Response surface approximations were formulated based on void parameters such as area and length fractions to provide an estimate of the effective stiffness. Obtaining quantitative relationships between the properties of the voids and their effects on stiffness of ceramic matrix composites are of ultimate interest, but the exploratory study presented here starts by first modeling the effects of voids on an isotropic material. Several cases with varying void parameters were modeled which resulted in a large amount of variability of the transverse stiffness and out-of-plane shear stiffness. An investigation into a physical explanation for the stiffness degradation led to the observation that the voids need to be treated as an entity that reduces load bearing capabilities in a space larger than what the void directly occupies through a corrected length fraction or area fraction. This provides explanation as to why void volume fraction is not the only important factor to consider when computing loss of stiffness.

  15. Controlling morphology in swelling-induced wrinkled surfaces

    NASA Astrophysics Data System (ADS)

    Breid, Derek Ronald

    Wrinkles represent a pathway towards the spontaneous generation of ordered surface microstructure for applications in numerous fields. Examples of highly complex ordered wrinkle structures abound in Nature, but the ability to harness this potential for advanced material applications remains limited. This work focuses on understanding the relationship between the patterns on a wrinkled surface and the experimental conditions under which they form. Because wrinkles form in response to applied stresses, particular attention is given to the nature of the stresses in a wrinkling surface. The fundamental insight gained was then utilized to account for observed wrinkle formation phenomena within more complex geometric and kinetic settings. In order to carefully control and measure the applied stresses on a wrinkling film, a swelling-based system was developed using poly(dimethylsiloxane) (PDMS), surface-oxidized with a UV-ozone treatment. The swelling of the oxidized surface upon exposure to an ethanol vapor atmosphere was characterized using beam-bending experiments, allowing quantitative measurements of the applied stress. The wrinkle morphologies were characterized as a function of the overstress, defined as the ratio of the applied swelling stress to the critical buckling stress of the material. A transition in the dominant morphology of the wrinkled surfaces from dimple patterns to ridge patterns was observed at an overstress value of ˜2. The pattern dependence of wrinkles on the ratio of the principal stresses was examined by fabricating samples with a gradient prestress. When swollen, these samples exhibited a smooth morphological transition from non-equibiaxial to equibiaxial patterns, with prestrains as low as 2.5% exhibiting non-equibiaxial characteristics. This transition was seen both in samples with low and high overstresses. To explore the impact of these stress states in more complex geometries, wrinkling hemispherical surfaces with radii of curvature

  16. Effects of helium injection mode on void formation in Fe-Ni-Cr alloys

    NASA Astrophysics Data System (ADS)

    Kimoto, T.; Lee, E. H.; Mansur, L. K.

    1988-09-01

    The effect of the helium injection mode on void formation during ion irradiation of the pure solution-annealing alloys Fe-15Ni-7Cr, Fe-35Ni-7Cr, Fe-45Ni-7Cr, Fe-10Ni-13Cr, Fe-40Ni-13Cr, Fe-45Ni-15Cr was examined. Ion irradiation was carried out with 4 MeV Ni ions at 948 K to doses of 30 to 100 dpa with: (1) no helium injection, (2) simultaneous helium injection and (3) helium preinjection and aging. Swelling variation with helium injection differed among the 7Cr alloys and 13-15Cr alloys. Only the simultaneous helium injection mode produced a bimodal cavity size distribution in the high Ni alloys. The critical radius, as estimated from the cavity size distributions appears to have increased with increasing dose, but no clear variation of the critical radius with composition was observed. Helium preinjection and one-hour aging at 948 K formed helium bubbles along the residual dislocations, while subsequent Ni irradiation caused void formation along the dislocation lines. The calculated helium concentration deduced from observable helium bubbles was low compared with the injected helium concentration in the alloys containing higher Ni and lower Cr.

  17. Swelling Mechanisms of UO2 Lattices with Defect Ingrowths.

    PubMed

    Günay, Seçkin D

    2015-01-01

    The swelling that occurs in uranium dioxide as a result of radiation-induced defect ingrowth is not fully understood. Experimental and theoretical groups have attempted to explain this phenomenon with various complex theories. In this study, experimental lattice expansion and lattice super saturation were accurately reproduced using a molecular dynamics simulation method. Based on their resemblance to experimental data, the simulation results presented here show that fission induces only oxygen Frenkel pairs while alpha particle irradiation results in both oxygen and uranium Frenkel pair defects. Moreover, in this work, defects are divided into two sub-groups, obstruction type defects and distortion type defects. It is shown that obstruction type Frenkel pairs are responsible for both fission- and alpha-particle-induced lattice swelling. Relative lattice expansion was found to vary linearly with the number of obstruction type uranium Frenkel defects. Additionally, at high concentrations, some of the obstruction type uranium Frenkel pairs formed diatomic and triatomic structures with oxygen ions in their octahedral cages, increasing the slope of the linear dependence. PMID:26244777

  18. Swelling Mechanisms of UO2 Lattices with Defect Ingrowths

    PubMed Central

    Günay, Seçkin D.

    2015-01-01

    The swelling that occurs in uranium dioxide as a result of radiation-induced defect ingrowth is not fully understood. Experimental and theoretical groups have attempted to explain this phenomenon with various complex theories. In this study, experimental lattice expansion and lattice super saturation were accurately reproduced using a molecular dynamics simulation method. Based on their resemblance to experimental data, the simulation results presented here show that fission induces only oxygen Frenkel pairs while alpha particle irradiation results in both oxygen and uranium Frenkel pair defects. Moreover, in this work, defects are divided into two sub-groups, obstruction type defects and distortion type defects. It is shown that obstruction type Frenkel pairs are responsible for both fission- and alpha-particle-induced lattice swelling. Relative lattice expansion was found to vary linearly with the number of obstruction type uranium Frenkel defects. Additionally, at high concentrations, some of the obstruction type uranium Frenkel pairs formed diatomic and triatomic structures with oxygen ions in their octahedral cages, increasing the slope of the linear dependence. PMID:26244777

  19. Quantitative analyses of extrudate swell for polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Wang, Kejian; Sun, Chongxiao

    2009-07-01

    The quantitative theory of extrudate swell for nanocomposite and pure polymer is significant either for optimum processing or for understanding their viscoelasticity. Based on Song's die swell theory for entangled polymers, one extrudate swell correlation with material properties and capillary parameters was developed for polymer melt and their nanocomposites when compensating reservoir entry effect. It was the first to find that the composite swell ratio can be the matrix swell ratio multiplied by the concentration shift factor. The factor is the functions of the shear field, filler content, filler internal structure and the surface state as well as the matrix properties. The quantitative model was well fitful for the five kinds of nanoomposites.

  20. Mineralogy-swelling potential relationships for expansive shales

    USGS Publications Warehouse

    Olsen, H.W.; Krosley, L.; Nelson, K.; Chabrillat, S.; Goetz, A.F.H.; Noe, D.C.

    2000-01-01

    The extent to which mineralogy and swelling potential is correlated in the expansive clays and shales is studied. Sites are selected in Cretaceous shales, including Pierre Shale, that are uplifted into steeply dipping strata near the foothills of the Rocky Mountains. Swelling potentials are obtained on limited suites of samples with conventional and labor-intensive schemes including Seed and Chen's schemes, and with swell-consolidation measurements in response to saturation, consolidation, and rebound in an oedometer. The results showing the percent total smectite provide a useful index of swelling potential concept defined by Seed and correlates well with the swelling potential indices developed by Seed, Chen, and McKeen.

  1. Formation of Voids from Negative Density Perturbations

    NASA Astrophysics Data System (ADS)

    de Araujo, J. C. N.; Opher, R.

    1990-11-01

    RESUMEN. Se estudia la formaci6n de huecos a partir de un espectro negativo de perturbaciones, tomando en cuenta la expansi6n del Universo, arrastre por fotones, enfriamiento por fotones, fotoionizaci6n, ioniza- ci6n colisional, enfriamiento Lyman a y la formaci6n y enfriamiento de moleculas H2. Nuestros resultados predicen la existencia de regiones 1/10 de Ia densidad promedio para regiones de masa lO - 1O10M . ABSTRACT. In the present paer we study the formation of voids from a negative spectrum of perturbations taking into account the expansion of the Universe, photon-drag, photon-cooling, photoionization, collisional ionization, Lyman a cooling and the formation and cooling of 112 molecules. Our results predict the existence of regions 1/10 the average density for regions of mass 1O - 1O10M@ : CLUSTERS-GALAXIES - COSMOLOGY

  2. Reconciling the local void with the CMB

    SciTech Connect

    Nadathur, Seshadri; Sarkar, Subir

    2011-03-15

    In the standard cosmological model, the dimming of distant Type Ia supernovae is explained by invoking the existence of repulsive ''dark energy'' which is causing the Hubble expansion to accelerate. However, this may be an artifact of interpreting the data in an (oversimplified) homogeneous model universe. In the simplest inhomogeneous model which fits the SNe Ia Hubble diagram without dark energy, we are located close to the center of a void modeled by a Lemaitre-Tolman-Bondi metric. It has been claimed that such models cannot fit the cosmic microwave background (CMB) and other cosmological data. This is, however, based on the assumption of a scale-free spectrum for the primordial density perturbation. An alternative physically motivated form for the spectrum enables a good fit to both SNe Ia (Constitution/Union2) and CMB (WMAP 7-yr) data, and to the locally measured Hubble parameter. Constraints from baryon acoustic oscillations and primordial nucleosynthesis are also satisfied.

  3. The void galaxy survey: Star formation properties

    NASA Astrophysics Data System (ADS)

    Beygu, B.; Kreckel, K.; van der Hulst, J. M.; Jarrett, T. H.; Peletier, R.; van de Weygaert, R.; van Gorkom, J. H.; Aragon-Calvo, M. A.

    2016-05-01

    We study the star formation properties of 59 void galaxies as part of the Void Galaxy Survey (VGS). Current star formation rates are derived from H α and recent star formation rates from near-UV imaging. In addition, infrared 3.4, 4.6, 12 and 22 μm Wide-field Infrared Survey Explorer emission is used as star formation and mass indicator. Infrared and optical colours show that the VGS sample displays a wide range of dust and metallicity properties. We combine these measurements with stellar and H I masses to measure the specific SFRs (SFR/M*) and star formation efficiencies ({SFR/{M }_H I}). We compare the star formation properties of our sample with galaxies in the more moderate density regions of the cosmic web, `the field'. We find that specific SFRs of the VGS galaxies as a function of stellar and H I mass are similar to those of the galaxies in these field regions. Their SFR α is slightly elevated than the galaxies in the field for a given total H I mass. In the global star formation picture presented by Kennicutt-Schmidt, VGS galaxies fall into the regime of low average star formation and correspondingly low H I surface density. Their mean {SFR α /{M}_{H I} and SFR α/M* are of the order of 10- 9.9 yr- 1. We conclude that while the large-scale underdense environment must play some role in galaxy formation and growth through accretion, we find that even with respect to other galaxies in the more mildly underdense regions, the increase in star formation rate is only marginal.

  4. Swelling transition of a clay induced by heating.

    PubMed

    Hansen, E L; Hemmen, H; Fonseca, D M; Coutant, C; Knudsen, K D; Plivelic, T S; Bonn, D; Fossum, J O

    2012-01-01

    Clays are of paramount importance for soil stability, but also in applications ranging from oil recovery to composites and hydrogels. Generically, clays are divided into two subclasses: macroscopically swelling, 'active' clays that have the capacity for taking up large amounts of water to form stable gels, and 'passive' or non-swelling clays; the former stabilize soils whereas the latter are known to lead to landslides. However, it has been unclear so far what mechanisms underlie clay swelling. Here, we report the first observation of a temperature-induced transition from a passive to an active, swelling clay. We propose a simple description of the swelling transition; while net attractive interactions are dominant at low temperatures so that the clay particles remain attached to each other in stacks, at higher temperatures it is energetically favourable for the clay to swell due to the entropy that is gained by counterions which are liberated during swelling.

  5. Swelling transition of a clay induced by heating.

    PubMed

    Hansen, E L; Hemmen, H; Fonseca, D M; Coutant, C; Knudsen, K D; Plivelic, T S; Bonn, D; Fossum, J O

    2012-01-01

    Clays are of paramount importance for soil stability, but also in applications ranging from oil recovery to composites and hydrogels. Generically, clays are divided into two subclasses: macroscopically swelling, 'active' clays that have the capacity for taking up large amounts of water to form stable gels, and 'passive' or non-swelling clays; the former stabilize soils whereas the latter are known to lead to landslides. However, it has been unclear so far what mechanisms underlie clay swelling. Here, we report the first observation of a temperature-induced transition from a passive to an active, swelling clay. We propose a simple description of the swelling transition; while net attractive interactions are dominant at low temperatures so that the clay particles remain attached to each other in stacks, at higher temperatures it is energetically favourable for the clay to swell due to the entropy that is gained by counterions which are liberated during swelling. PMID:22943004

  6. Sulfonylurea Receptor 1 Contributes to the Astrocyte Swelling and Brain Edema in Acute Liver Failure

    PubMed Central

    Jayakumar, A.R.; Valdes, V.; Tong, X.Y.; Shamaladevi, N.; Gonzalez, W.; Norenberg, M.D.

    2014-01-01

    Astrocyte swelling (cytotoxic brain edema) is the major neurological complication of acute liver failure (ALF), a condition in which ammonia has been strongly implicated in its etiology. Ion channels and transporters are known to be involved in cell volume regulation and a disturbance in these systems may result in cell swelling. One ion channel known to contribute to astrocyte swelling/brain edema in other neurological disorders is the ATP-dependent, non-selective cation channel (NCCa-ATP channel). We therefore examined its potential role in the astrocyte swelling/brain edema associated with ALF. Cultured astrocytes treated with 5 mM ammonia showed a 3-fold increase in the sulfonylurea receptor type 1 (SUR1) protein expression, a marker of NCCa-ATP channel activity. Blocking SUR1 with glibenclamide significantly reduced the ammonia-induced cell swelling in cultured astrocytes. Additionally, overexpression of SUR1 in ammonia-treated cultured astrocytes was significantly reduced by co-treatment of cells with BAY 11-7082, an inhibitor of NF-κB, indicating the involvement of an NF-κB-mediated SUR1 upregulation in the mechanism of ammonia-induced astrocyte swelling. Brain SUR1 mRNA level was also found to be increased in the thioacetamide (TAA) rat model of ALF. Additionally, we found a significant increase in SUR1 protein expression in rat brain cortical astrocytes in TAA-treated rats. Treatment with glibenclamide significantly reduced the brain edema in this model of ALF. These findings strongly suggest the involvement of NCCa-ATP channel in the astrocyte swelling/brain edema in ALF, and that targeting this channel may represent a useful approach for the treatment of the brain edema associated with ALF. PMID:24443056

  7. Swelling induced by alpha decay in monazite and zirconolite ceramics: A XRD and TEM comparative study

    NASA Astrophysics Data System (ADS)

    Deschanels, X.; Seydoux-Guillaume, A. M.; Magnin, V.; Mesbah, A.; Tribet, M.; Moloney, M. P.; Serruys, Y.; Peuget, S.

    2014-05-01

    Zirconolite and monazite matrices are potential ceramics for the containment of actinides (Np, Cm, Am, Pu) which are produced over the reprocessing of spent nuclear fuel. Actinides decay mainly through the emission of alpha particles, which in turn causes most ceramics to undergo structural and textural changes (amorphization and/or swelling). In order to study the effects of alpha decays on the above mentioned ceramics two parallel approaches were set up. The first involved the use of an external irradiation source, Au, which allowed the deposited recoil energy to be simulated. The second was based on short-lived actinide doping with 238Pu, (i.e. an internal source), via the incorporation of plutonium oxide into both the monazite and zirconolite structures during synthesis. In both types of irradiation experiments, the zirconolite samples became amorphous at room temperature with damage close to 0.3 dpa; corresponding to a critical dose of 4 × 1018 α g-1 (i.e. ∼1.3 × 1021 keV cm-3). Both zirconolite samples also showed the same degree of macroscopic swelling at saturation (∼6%), with ballistic processes being the predominant damaging effect. In the case of the monazite however, the macroscopic swelling and amorphization were dependent on the nature of the irradiation. Externally, (Au), irradiated samples became amorphous while also demonstrating a saturation swelling of up to 8%. In contrast to this, the swelling of the 238Pu doped samples was much smaller at ∼1%. Also, unlike the externally (Au) irradiated monazite these 238Pu doped samples remained crystalline up to 7.5 × 1018 α g-1 (0.8 dpa). XRD, TEM and swelling measurements were used to fully characterize and interpret this behavior. The low swelling and the conservation of the crystalline state of 238Pu doped monazite samples indicates that alpha annealing took place within this material.

  8. Void shrinking process and mechanisms of the diffusion bonded Ti-6Al-4V alloy with different surface roughness

    NASA Astrophysics Data System (ADS)

    Li, H.; Li, M. Q.; Kang, P. J.

    2016-01-01

    The diffusion bonding of Ti-6Al-4V alloy with different surface roughness was performed at 5 and 10 MPa. The influence of surface roughness on the void shrinking process and mechanisms was investigated. The average void size increases as the R a increases from 0.33 to 0.44 μm, while it decreases as the R a increases to 0.46 μm because of the decreasing of R λq. The void shrinking mechanisms were analyzed by using the dynamic model of void shrinking. Power-law creep is a dominant mechanism on void shrinking, of which the contribution decreases as the R a increases from 0.33 to 0.44 μm, while it increases as the R a increases to 0.46 μm. The influence of surface roughness on the contribution of plastic deformation and surface source mechanism on void shrinking is not significant while that on the contribution of interface source mechanism is dependent on the imposing pressure. The optimizing surface roughness is with a R a of 0.33 μm and R λq of 5.38 μm in this study.

  9. Prediction of postoperative facial swelling, pain and trismus following third molar surgery based on preoperative variables

    PubMed Central

    de Souza-Santos, Jadson A.; Martins-Filho, Paulo R.; da Silva, Luiz C.; de Oliveira e Silva, Emanuel D.; Gomes, Ana C.

    2013-01-01

    Objective: This paper investigates the relationship between preoperative findings and short-term outcome in third molar surgery. Study design: A prospective study was carried out involving 80 patients who required 160 surgical extractions of impacted mandibular third molars between January 2009 and December 2010. All extractions were performed under local anesthesia by the same dental surgeon. Swelling and maximal inter-incisor distance were measured at 48 h and on the 7th day postoperatively. Mean visual analogue pain scores were determined at four different time periods. Results: One-hundred eight (67.5%) of the 160 extractions were performed on male subjects and 52 (32.5%) were performed on female subjects. Median age was 22.46 years. The amount of facial swelling varied depending on gender and operating time. Trismus varied depending on gender, operating time and tooth sectioning. The influence of age, gender and operating time varied depending on the pain evaluation period (p < 0.05). Conclusions: Short-term outcomes of third molar operations (swelling, trismus and pain) differ depending on the patients’ characteristics (age, gender and body mass index). Moreover, surgery characteristics such as operating time and tooth sectioning were also associated with postoperative variables. Key words:Third molar extraction, pain, swelling, trismus, postoperative findings, prediction. PMID:23229245

  10. The effects of temperature and inhibitors on HCO3-stimulated swelling and ion uptake of monkey cerebral cortex.

    PubMed

    Bourke, R S; Kimelberg, H K; Nelson, L R

    1976-03-26

    In the presence of high concentrations of K+, additions of HCO3- as low as 0.35 mM caused a 23% increase in swelling, and concomitant increases in the chloride content of incubating monkey cerebrocortical slices. The uptake of chloride was accompanied by increased uptake of sodium and was highly temperature dependent, showing a marked activation at approximately 30 degrees C. A similar temperature activation was also found for a Mg2+-dependent, HCO3-stimulated ATPase activity in monkey cerebral cortex, consistent with a possible role for this enzyme in the K+ and HCO3-dependent swelling process and its associated ion movements. K+-dependent, HCO3-stimulated cerebrocortical tissue swelling with uptake of Na+ and Cl- was inhibited by acetazolamide indicating that carbonic anhydrase was also involved. The addition of ouabain also inhibited swelling and K+ and Cl- uptake at low concentrations, but led to increased swelling at higher concentrations ( greater than 10 mum). A similar biphasic effect on swelling was also seen following addition of ethacrynic acid. PMID:130962

  11. Release of Water Soluble Drugs from Dynamically Swelling POLY(2-HYDROXYETHYL Methacrylate - CO - Methacrylic Acid) Hydrogels.

    NASA Astrophysics Data System (ADS)

    Kou, Jim Hwai-Cher

    In this study, ionizable copolymers of HEMA and methacrylic acid (MA) are investigated for their potential use in developing pH dependent oral delivery systems. Because of the MA units, these gels swell extensively at high pH. Since solute diffusion in the hydrophilic polymers depends highly on the water content of the matrix, it is anticipated that the release rate will be modulated by this pH induced swelling. From a practical point of view, the advantage of the present system is that one can minimize drug loss in the stomach and achieve a programmed release in intestine. This approach is expected to improve delivery of acid labile drugs or drugs that cause severe gastrointestinal side effects. This work mainly focuses on the basic understanding of the mechanism involved in drug release from the poly(HEMA -co- MA) gels, especially under dynamic swelling conditions. Equilibrium swelling is first characterized since water content is the major determinant of transport properties in these gels. Phenylpropanolamine (PPA) is chosen as the model drug for the release study and its diffusion characteristics in the gel matrix determined. The data obtained show that the PPA diffusivity follows the free volume theory of Yasuda, which explains the accelerating effect of swelling on drug release. A mathematical model based on a diffusion mechanism has been developed to describe PPA release from the swelling gels. Based on this model, several significant conclusions can be drawn. First, the release rate can be modulated by the aspect ratio of the cylindrical geometry, and this has a practical implication in dosage form design. Second, the release rate can be lowered quite considerably if the dimensional increase due to swelling is significant. Consequently, it is the balance between the drug diffusivity increase and the gel dimensional growth that determines the release rate from the swelling matrix. Third, quasi-steady release kinetics, which are characteristic of swelling

  12. Luminosity distance in 'Swiss cheese' cosmology with randomized voids. I. Single void size

    SciTech Connect

    Vanderveld, R. Ali; Flanagan, Eanna E.; Wasserman, Ira

    2008-10-15

    Recently, there have been suggestions that the Type Ia supernova data can be explained using only general relativity and cold dark matter with no dark energy. In 'Swiss cheese' models of the Universe, the standard Friedmann-Robertson-Walker picture is modified by the introduction of mass-compensating spherical inhomogeneities, typically described by the Lemaitre-Tolman-Bondi metric. If these inhomogeneities correspond to underdense cores surrounded by mass-compensating overdense shells, then they can modify the luminosity distance-redshift relation in a way that can mimic accelerated expansion. It has been argued that this effect could be large enough to explain the supernova data without introducing dark energy or modified gravity. We show that the large apparent acceleration seen in some models can be explained in terms of standard weak field gravitational lensing together with insufficient randomization of void locations. The underdense regions focus the light less than the homogeneous background, thus dimming supernovae in a way that can mimic the effects of acceleration. With insufficient randomization of the spatial location of the voids and of the lines of sight, coherent defocusing can lead to anomalously large demagnification effects. We show that a proper randomization of the voids and lines of sight reduces the effect to the point that it can no longer explain the supernova data.

  13. Luminosity distance in ``Swiss cheese'' cosmology with randomized voids. I. Single void size

    NASA Astrophysics Data System (ADS)

    Vanderveld, R. Ali; Flanagan, Éanna É.; Wasserman, Ira

    2008-10-01

    Recently, there have been suggestions that the Type Ia supernova data can be explained using only general relativity and cold dark matter with no dark energy. In “Swiss cheese” models of the Universe, the standard Friedmann-Robertson-Walker picture is modified by the introduction of mass-compensating spherical inhomogeneities, typically described by the Lemaître-Tolman-Bondi metric. If these inhomogeneities correspond to underdense cores surrounded by mass-compensating overdense shells, then they can modify the luminosity distance-redshift relation in a way that can mimic accelerated expansion. It has been argued that this effect could be large enough to explain the supernova data without introducing dark energy or modified gravity. We show that the large apparent acceleration seen in some models can be explained in terms of standard weak field gravitational lensing together with insufficient randomization of void locations. The underdense regions focus the light less than the homogeneous background, thus dimming supernovae in a way that can mimic the effects of acceleration. With insufficient randomization of the spatial location of the voids and of the lines of sight, coherent defocusing can lead to anomalously large demagnification effects. We show that a proper randomization of the voids and lines of sight reduces the effect to the point that it can no longer explain the supernova data.

  14. Lensing measurements of the mass distribution in SDSS voids

    NASA Astrophysics Data System (ADS)

    Clampitt, Joseph; Jain, Bhuvnesh

    2015-12-01

    We measure weak lensing mass profiles of voids from a volume-limited sample of SDSS Luminous Red Galaxies (LRGs). We find voids using an algorithm designed to maximize the lensing signal by dividing the survey volume into 2D slices, and then finding holes in this 2D distribution of LRGs. We perform a stacked shear measurement on about 20 000 voids with radii between 15 and 55 Mpc h-1, and redshifts between 0.16 and 0.37. We measure the characteristic radial shear signal of voids with a signal to noise of 7. The mass profile corresponds to a fractional underdensity of about -0.4 inside the void radius and a slow approach to the mean density indicating a partially compensated void structure. We compare our measured shape and amplitude with the predictions of Krause et al. Voids in the galaxy distribution have been extensively modelled using simulations and measured in the SDSS. We discuss how the addition of void mass profiles can enable studies of galaxy formation and cosmology.

  15. High gain durable anti-reflective coating with oblate voids

    DOEpatents

    Maghsoodi, Sina; Brophy, Brenor L.; Colson, Thomas E.; Gonsalves, Peter R.; Abrams, Ze'ev

    2016-06-28

    Disclosed herein are single layer transparent coatings with an anti-reflective property, a hydrophobic property, and that are highly abrasion resistant. The single layer transparent coatings contain a plurality of oblate voids. At least 1% of the oblate voids are open to a surface of the single layer transparent coatings.

  16. High Frequency Sacral Root Nerve Block Allows Bladder Voiding

    PubMed Central

    Boger, Adam S.; Bhadra, Narendra; Gustafson, Kenneth J

    2013-01-01

    1) Aims Dyssynergic reflexive external urethral sphincter (EUS) activity following spinal cord injury can prevent bladder voiding, resulting in significant medical complications. Irreversible sphincterotomies or neurotomies can prevent EUS activation and allow bladder voiding, but may cause incontinence or loss of sacral reflexes. We investigated whether kilohertz frequency (KF) electrical conduction block of the sacral roots could prevent EUS activation and allow bladder voiding. 2) Methods The S2 sacral nerve roots were stimulated bilaterally to generate bladder pressure in 6 cats. One S1 nerve root was stimulated proximally (20 Hz biphasic pulse trains) to evoke EUS pressure, simulating worst-case dyssynergic EUS reflexes. KF waveforms (12.5 kHz biphasic square wave) applied to an electrode implanted distally on the S1 nerve root blocked nerve conduction, preventing the increase in EUS pressure and allowing voiding. 3) Results Applying KF waveforms increased bladder voiding in single, limited-duration trials from 3 ± 6% to 59 ± 12%. Voiding could be increased to 82 ± 9% of the initial bladder volume by repeating or increasing the duration of the trials. 4) Conclusions Sacral nerve block can prevent EUS activation and allow complete bladder voiding, potentially eliminating the need for a neurotomy. Eliminating neurotomy requirements could increase patient acceptance of bladder voiding neuroprostheses, increasing patient quality of life and reducing the cost of patient care. PMID:22473837

  17. The relationship between void waves and flow regime transition

    SciTech Connect

    Lahey, R.T. Jr.; Drew, D.A.; Kalkach-Navarro, S.; Park, J.W.

    1992-12-31

    The results of an extensive experimental and analytical study on the relationship between void waves and flow regime transition are presented, in particular, the bubbly/slug flow regime transition. It is shown that void wave instability signals a flow regime transition.

  18. Warmth elevating the depths: shallower voids with warm dark matter

    NASA Astrophysics Data System (ADS)

    Yang, Lin F.; Neyrinck, Mark C.; Aragón-Calvo, Miguel A.; Falck, Bridget; Silk, Joseph

    2015-08-01

    Warm dark matter (WDM) has been proposed as an alternative to cold dark matter (CDM), to resolve issues such as the apparent lack of satellites around the Milky Way. Even if WDM is not the answer to observational issues, it is essential to constrain the nature of the dark matter. The effect of WDM on haloes has been extensively studied, but the small-scale initial smoothing in WDM also affects the present-day cosmic web and voids. It suppresses the cosmic `sub-web' inside voids, and the formation of both void haloes and subvoids. In N-body simulations run with different assumed WDM masses, we identify voids with the ZOBOV algorithm, and cosmic-web components with the ORIGAMI algorithm. As dark-matter warmth increases (i.e. particle mass decreases), void density minima grow shallower, while void edges change little. Also, the number of subvoids decreases. The density field in voids is particularly insensitive to baryonic physics, so if void density profiles and minima could be measured observationally, they would offer a valuable probe of the nature of dark matter. Furthermore, filaments and walls become cleaner, as the substructures in between have been smoothed out; this leads to a clear, mid-range peak in the density PDF.

  19. Measuring the growth rate of structure around cosmic voids

    NASA Astrophysics Data System (ADS)

    Hawken, A. J.; Michelett, D.; Granett, B.; Iovino, A.; Guzzo, L.

    2016-10-01

    Using an algorithm based on searching for empty spheres we identified 245 voids in the VIMOS Public Extragalactic Redshift Survey (VIPERS). We show how by modelling the anisotropic void-galaxy cross correlation function we can probe the growth rate of structure.

  20. Void nucleation in spheroidized steels during tensile deformation

    SciTech Connect

    Fisher, Jr, J R

    1980-04-01

    An investigation was conducted to determine the effects of various mechanical and material parameters on void formation at cementite particles in axisymmetric tensile specimens of spheroidized plain carbon steels. Desired microstructures for each of three steel types were obtained. Observations of void morphology with respect to various microstructural features were made using optical and scanning electron microscopy.

  1. The Local Void: for or against ΛCDM?

    NASA Astrophysics Data System (ADS)

    Xie, Lizhi; Gao, Liang; Guo, Qi

    2014-06-01

    The emptiness of the Local Void has been put forward as a serious challenge to the current standard paradigm of structure formation in Λ cold dark matter (CDM). We use a high-resolution cosmological N-body simulation, the Millennium-II run, combined with a sophisticated semi-analytic galaxy formation model, to explore statistically whether the Local Void is allowed within our current knowledge of galaxy formation in ΛCDM. We find that about 14 per cent of the Local Group analogue systems (11 of 77) in our simulation are associated with nearby low-density regions having size and `emptiness' similar to those of the observed Local Void. This suggests that, rather than a crisis of the ΛCDM, the emptiness of the Local Void is indeed a success of the standard ΛCDM theory. The paucity of faint galaxies in such voids results from a combination of two factors: a lower amplitude of the halo mass function in the voids than in the field, and a lower galaxy formation efficiency in the void haloes due to halo assembly bias effects. While the former is the dominated factor, the later also plays a sizeable role. The halo assembly bias effect results in a stellar mass fraction 25 per cent lower for void galaxies when compared to field galaxies with the same halo mass.

  2. Effects of voids on the reconstruction of the equation of state of dark energy

    SciTech Connect

    Lavallaz, Arnaud de; Fairbairn, Malcolm

    2011-10-15

    We quantify the effects of the voids known to exist in the Universe upon the reconstruction of the dark energy equation of state w. We show that the effect can start to be comparable with some of the other errors taken into account when analyzing supernova data, depending strongly upon the low redshift cutoff used in the sample. For the supernova data alone, the error induced in the reconstruction of w is much larger than the percent level. When the Baryonic Acoustic Oscillations and the Cosmic Microwave Background data are included in the fit, the effect of the voids upon the determination of w is much lessened but is not much smaller than some of the other errors taken into consideration when performing such fits. We also look at the effect of voids upon the estimation of the equation of state when we allow w to vary over time and show that even when supernova, Cosmic Microwave Background, and Baryonic Acoustic Oscillations data are used to constrain the equation of state, the best fit points in parameter space can change at the 10% level due to the presence of voids, and error-bars increase significantly.

  3. Luminosity distance in Swiss-cheese cosmology with randomized voids and galaxy halos

    NASA Astrophysics Data System (ADS)

    Flanagan, Éanna É.; Kumar, Naresh; Wasserman, Ira

    2013-08-01

    We study the fluctuations in luminosity distance due to gravitational lensing produced both by galaxy halos and large-scale voids. Voids are represented via a “Swiss-cheese” model consisting of a ΛCDM Friedmann-Robertson-Walker background from which a number of randomly distributed, spherical regions of comoving radius 35 Mpc are removed. A fraction of the removed mass is then placed on the shells of the spheres, in the form of randomly located halos. The halos are assumed to be nonevolving and are modeled with Navarro-Frenk-White profiles of a fixed mass. The remaining mass is placed in the interior of the spheres, either smoothly distributed or as randomly located halos. We compute the distribution of magnitude shifts using a variant of the method of Holz and Wald [Phys. Rev. D 58, 063501 (1998)], which includes the effect of lensing shear. In the two models we consider, the standard deviation of this distribution is 0.065 and 0.072 magnitudes and the mean is -0.0010 and -0.0013 magnitudes, for voids of radius 35 Mpc and the sources at redshift 1.5, with the voids chosen so that 90% of the mass is on the shell today. The standard deviation due to voids and halos is a factor ˜3 larger than that due to 35 Mpc voids alone with a 1 Mpc shell thickness, which we studied in our previous work. We also study the effect of the existence of evacuated voids, by comparing to a model where all the halos are randomly distributed in the interior of the sphere with none on its surface. This does not significantly change the variance but does significantly change the demagnification tail. To a good approximation, the variance of the distribution depends only on the mean column density of halos (halo mass divided by its projected area), the concentration parameter of the halos, and the fraction of the mass density that is in the form of halos (as opposed to smoothly distributed); it is independent of how the halos are distributed in space. We derive an approximate analytic

  4. Erythrocyte swelling and membrane hole formation in hypotonic media as studied by conductometry.

    PubMed

    Pribush, A; Meyerstein, D; Hatskelzon, L; Kozlov, V; Levi, I; Meyerstein, N

    2013-02-01

    Hypoosmotic swelling of erythrocytes and the formation of membrane holes were studied by measuring the dc conductance (G). In accordance with the theoretical predictions, these processes are manifested by a decrease in G followed by its increase. Thus, unlike the conventional osmotic fragility test, the proposed methodological approach allows investigations of both the kinetics of swelling and the erythrocyte fragility. It is shown that the initial rate of swelling and the equilibrium size of the cells are affected by the tonicity of a hypotonic solution and the membrane rheological properties. Because the rupture of biological membranes is a stochastic process, a time-dependent increase in the conductance follows an integral distribution function of the membrane lifetime. The main conclusion which stems from reported results is that information about rheological properties of red blood cell (RBC) membranes and the resistivity of RBCs to a certain osmotic shock may be extracted from conductance signals. PMID:23343529

  5. Swelling of radiation crosslinked acrylamide-based microgels and their potential applications

    NASA Astrophysics Data System (ADS)

    Abd El-Rehim, H. A.

    2005-10-01

    Crosslinked polyacrylamide PAAm and acrylamide-Na-acrylate P(AAm-Na-AAc) microgels were prepared by electron beam irradiation. It was found that the dose required for crosslinking depends on the polymer moisture content, so that the dose to obtain PAAm of maximum gel fraction was over 40 and 20 kGy for dry and moist PAAm, respectively. The structural changes in irradiated PAAm were investigated using FTIR and SEM. The swelling property of such microgels in distilled water and real urine solution was determined and crosslinked polymers reached their equilibrium swelling state in a few minutes. As the gel content and crosslinking density decrease, the swelling of the microgels increases. The ability of the microgels to absorb and retain large amount of solutions suggested their possible uses in horticulture and in hygienic products such as disposable diapers.

  6. Voids and the Cosmic Web: cosmic depression & spatial complexity

    NASA Astrophysics Data System (ADS)

    van de Weygaert, Rien

    2016-10-01

    Voids form a prominent aspect of the Megaparsec distribution of galaxies and matter. Not only do theyrepresent a key constituent of the Cosmic Web, they also are one of the cleanest probesand measures of global cosmological parameters. The shape and evolution of voids are highly sensitive tothe nature of dark energy, while their substructure and galaxy population provides a direct key to thenature of dark matter. Also, the pristine environment of void interiors is an important testing groundfor our understanding of environmental influences on galaxy formation and evolution. In this paper, we reviewthe key aspects of the structure and dynamics ofvoids, with a particular focus on the hierarchical evolution of the void population. We demonstratehow the rich structural pattern of the Cosmic Web is related to the complex evolution and buildupof voids.

  7. The cosmic web in CosmoGrid void regions

    NASA Astrophysics Data System (ADS)

    Rieder, Steven; van de Weygaert, Rien; Cautun, Marius; Beygu, Burcu; Portegies Zwart, Simon

    2016-10-01

    We study the formation and evolution of the cosmic web, using the high-resolution CosmoGrid ΛCDM simulation. In particular, we investigate the evolution of the large-scale structure around void halo groups, and compare this to observations of the VGS-31 galaxy group, which consists of three interacting galaxies inside a large void. The structure around such haloes shows a great deal of tenuous structure, with most of such systems being embedded in intra-void filaments and walls. We use the Nexus+} algorithm to detect walls and filaments in CosmoGrid, and find them to be present and detectable at every scale. The void regions embed tenuous walls, which in turn embed tenuous filaments. We hypothesize that the void galaxy group of VGS-31 formed in such an environment.

  8. Dust-void formation in a dc glow discharge.

    PubMed

    Fedoseev, A V; Sukhinin, G I; Dosbolayev, M K; Ramazanov, T S

    2015-08-01

    Experimental investigations of dusty plasma parameters of a dc glow discharge were performed in a vertically oriented discharge tube. Under certain conditions, dust-free regions (voids) were formed in the center of the dust particle clouds that levitated in the strong electric field of a stratified positive column. A model for radial distribution of dusty plasma parameters of a dc glow discharge in inert gases was developed. The behavior of void formation was investigated for different discharge conditions (type of gas, discharge pressure, and discharge current) and dust particle parameters (particle radii and particle total number). It was shown that it is the ion drag force radial component that leads to the formation of voids. Both experimental and calculated results show that the higher the discharge current the wider dust-free region (void). The calculations also show that more pronounced voids are formed for dust particles with larger radii and under lower gas pressures.

  9. Distinguishing f(R) gravity with cosmic voids

    NASA Astrophysics Data System (ADS)

    Zivick, P.; Sutter, P. M.

    2016-10-01

    We use properties of void populations identified in N-body simulations to forecast the ability of upcoming galaxy surveys to differentiate models of f(R) gravity from \\lcdm cosmology. We analyze simulations designed to mimic the densities, volumes, and clustering statistics of upcoming surveys, using the public {\\tt VIDE} toolkit. We examine void abundances as a basic probe at redshifts 1.0 and 0.4. We find that stronger f(R) coupling strengths produce voids up to ~20% larger in radius, leading to a significant shift in the void number function. As an initial estimate of the constraining power of voids, we use this change in the number function to forecast a constraint on the coupling strength of Δ fR0 = 10-5.

  10. Simulation study of sulfonate cluster swelling in ionomers

    NASA Astrophysics Data System (ADS)

    Allahyarov, Elshad; Taylor, Philip L.; Löwen, Hartmut

    2009-12-01

    We have performed simulations to study how increasing humidity affects the structure of Nafion-like ionomers under conditions of low sulfonate concentration and low humidity. At the onset of membrane hydration, the clusters split into smaller parts. These subsequently swell, but then maintain constant the number of sulfonates per cluster. We find that the distribution of water in low-sulfonate membranes depends strongly on the sulfonate concentration. For a relatively low sulfonate concentration, nearly all the side-chain terminal groups are within cluster formations, and the average water loading per cluster matches the water content of membrane. However, for a relatively higher sulfonate concentration the water-to-sulfonate ratio becomes nonuniform. The clusters become wetter, while the intercluster bridges become drier. We note the formation of unusual shells of water-rich material that surround the sulfonate clusters.

  11. Time-development of sulphate hydration in anhydritic swelling rocks

    NASA Astrophysics Data System (ADS)

    Serafeimidis, Konstantinos

    2015-04-01

    Anhydritic claystones are among the most problematic rocks in tunnelling due to their distinctive swelling properties. They consist of a clay matrix with distributed anhydrite particles, veins and layers and have caused severe damage to numerous tunnels excavated in the Gypsum Keuper formation in North-Western Switzerland and South-Western Germany. The swelling of anhydritic claystones which is mainly attributed to the transformation of anhydrite into gypsum (a chemical process which leads to an increase in the solids of 61 percent), is a markedly time-dependent process. It may take several decades to complete in nature and is therefore important for the design particularly of the final tunnel lining. Anhydrite occurs either in the form of particles or of layers and veins of different thicknesses and spacings. The particles may have an approximately spherical or rather prismatic form, while their size lies within a wide range (from few micrometer to few centimeter). The shape and size of the anhydrite particles and layers are important for the specific surface of anhydrite and thus for the evolution of its hydration over time. In the present contribution we focus on the kinetics of the chemical reactions in sulphatic rocks, limiting ourselves to closed systems, i.e. without investigating the effects of seepage flow and diffusive transport, which may also be important. In order to achieve this, a consistent and comprehensive dissolution and precipitation model has been developed that accounts for arbitrary geometrical forms of anhydrite as well as for the sealing of anhydrite by a layer of gypsum. The investigations have shown that anhydrite dissolution represents the limiting mechanism if anhydrite occurs in the form of larger particles or thicker veins (> 1 millimeter) and there are sufficient nuclei for gypsum growth (e.g. precipitation takes place on of the surfaces of inert minerals). It has also been indicated that the time required for the whole amount of

  12. Effects of Temperature and Gas Composition on Reduction and Swelling of Magnetite Concentrates

    NASA Astrophysics Data System (ADS)

    Kapelyushin, Yury; Sasaki, Yasushi; Zhang, Jianqiang; Jeong, Sunkwang; Ostrovski, Oleg

    2016-08-01

    The gaseous reduction of magnetite ore concentrates was studied using CO-CO2 and CO-CO2-H2 gas mixtures at different temperatures and gas compositions. The reduction of magnetite ore by CO-CO2 gas mixture was examined at temperatures 973 K to 1173 K (700 °C to 900 °C) at CO/CO2 ratio 80/20, and at varied CO/CO2 ratio from 60/40 to 85/15 at 1023 K (750 °C). In the reduction of magnetite ore by CO-CO2-H2 gas mixture, temperature was 1173 K (800 °C) and hydrogen content changed from 5 to 25 vol pct at constant CO/CO2 ratio of 80/20. Reduction of magnetite ore did not go to completion in both CO-CO2 and CO-CO2-H2 gas mixtures. Addition of H2 to the CO-CO2 gas mixture accelerated the reduction in the first 10 to 30 minutes of reaction. However, the degree of reduction by gas containing 5 to 25 vol pct H2 after 60 to 120 minutes of reaction was in the range 60 to 65 pct, while the degree of reduction by CO-CO2 gas (80 vol pct CO) after 120 minutes of reaction was close to 70 pct. Significant swelling of magnetite ore pellets was observed in the reduction by CO-CO2 gas mixture. Addition of H2 to the CO-CO2 gas mixture decreased swelling. Swelling of magnetite ore during the reduction was attributed to the breakout of iron layer caused by the increase of the inner pressure in the voids at the wüstite/iron phase boundary.

  13. Numerical method for estimating void spaces of rock joints and the evolution of void spaces under different contact states

    NASA Astrophysics Data System (ADS)

    Xia, Caichu; Gui, Yang; Wang, Wei; Du, Shigui

    2014-12-01

    To determine the void spaces of rock joints under different normal stresses and shear displacements, we mainly introduce a numerical method which was developed based on equivalent void space derived from composite topography. The new method requires the 3D surface data of rock joints, and the normal closure data of the compression test under different shear displacements, while in conventional methods, some disparate materials are inserted between the joint surfaces or special equipments are needed for the measurement of the void space of rock joints without shearing occurs. To apply the technique, a modified 3D box counting method that considers the self-affine fractal property of void spaces was employed to calculate the 3D fractal dimension of the void space. Specially designed experiment was conducted on a cylindrical specimen of artificial joints to explore aperture distribution, and the correlations between void space characteristics, 3D fractal dimension and mean aperture, and normal stress under different shear displacements. The present study focuses on the introduction of the new method for estimating void spaces of rock joints, while the void spaces model obtained contains the combined surfaces roughness and aperture information of rock joints under different normal loads and shear displacements is promising in investigating the mechanical and hydraulic properties during the loading process.

  14. Swelling and osmotic flow in a potential host rock

    NASA Astrophysics Data System (ADS)

    Horseman, S. T.; Harrington, J. F.; Noy, D. J.

    Measurements of osmotic and hydraulic permeability are reported for a series of tests conducted on Opalinus Clay samples from the Mt. Terri underground research laboratory in the Jura Mountains of NE Switzerland. Osmotic flow was observed across discs of this clayshale separating 0.245 M NaCl solution from distilled water. Pressure transients monitored during constant flow rate testing were analysed to give permeability and specific storage values. The mean permeability normal to bedding of the two Opalinus Clay specimens was 7.9 × 10 -21 m 2. The mean specific storage based on all reliable determinations was 4.1 × 10 -4 m -1. Values calculated from the steady-state pressure gradients established during constant flow rate testing were very close to those obtained by mathematical analysis of pressure transients. The calculation of the transients was carried out using a new model of flow and solute transport which included terms for the osmotic coupling. The form of the pressure transients and the magnitude of the strain seen during the tests lead to a revision to the definition of solid phase compressibility to incorporate a term dependent upon the osmotic coupling coefficient. Steady-state osmotic flow rates were in the range 0.1-0.6 μL h -1 when the specimens were placed between a sodium chloride solution with a theoretical osmotic pressure of 1.19 MPa and distilled water. Transient flow rates were substantially larger. Membrane efficiencies were found to be relatively low, ranging from 1% to 6% (mean around 4%). The mean osmotic permeability normal to bedding was 3.5 × 10 -22 m 2. Specific storage and pore compressibility values were substantially larger than anticipated, suggesting that the volumetric strain of the clayshale under the conditions of laboratory testing must be largely determined by quasi-elastic deformation processes such as swelling and crack dilation. To test this hypothesis, a 3-D swelling test was performed on a cubic specimen of the same

  15. Seismic Techniques for Subsurface Voids Detection

    NASA Astrophysics Data System (ADS)

    Gritto, Roland; Korneev, Valeri; Elobaid Elnaiem, Ali; Mohamed, Fathelrahman; Sadooni, Fadhil

    2016-04-01

    A major hazards in Qatar is the presence of karst, which is ubiquitous throughout the country including depressions, sinkholes, and caves. Causes for the development of karst include faulting and fracturing where fluids find pathways through limestone and dissolve the host rock to form caverns. Of particular concern in rapidly growing metropolitan areas that expand in heretofore unexplored regions are the collapse of such caverns. Because Qatar has seen a recent boom in construction, including the planning and development of complete new sub-sections of metropolitan areas, the development areas need to be investigated for the presence of karst to determine their suitability for the planned project. In this paper, we present the results of a study to demonstrate a variety of seismic techniques to detect the presence of a karst analog in form of a vertical water-collection shaft located on the campus of Qatar University, Doha, Qatar. Seismic waves are well suited for karst detection and characterization. Voids represent high-contrast seismic objects that exhibit strong responses due to incident seismic waves. However, the complex geometry of karst, including shape and size, makes their imaging nontrivial. While karst detection can be reduced to the simple problem of detecting an anomaly, karst characterization can be complicated by the 3D nature of the problem of unknown scale, where irregular surfaces can generate diffracted waves of different kind. In our presentation we employ a variety of seismic techniques to demonstrate the detection and characterization of a vertical water collection shaft analyzing the phase, amplitude and spectral information of seismic waves that have been scattered by the object. We used the reduction in seismic wave amplitudes and the delay in phase arrival times in the geometrical shadow of the vertical shaft to independently detect and locate the object in space. Additionally, we use narrow band-pass filtered data combining two

  16. Evolution and regularity results for epitaxially strained thin films and material voids

    NASA Astrophysics Data System (ADS)

    Piovano, Paolo

    In this dissertation we study free boundary problems that model the evolution of interfaces in the presence of elasticity, such as thin film profiles and material void boundaries. These problems are characterized by the competition between the elastic bulk energy and the anisotropic surface energy. First, we consider the evolution equation with curvature regularization that models the motion of a two-dimensional thin film by evaporation-condensation on a rigid substrate. The film is strained due to the mismatch between the crystalline lattices of the two materials and anisotropy is taken into account. We present the results contained in [62] where the author establishes short time existence, uniqueness and regularity of the solution using De Giorgi's minimizing movements to exploit the L2-gradient flow structure of the equation. This seems to be the first analytical result for the evaporation-condensation case in the presence of elasticity. Second, we consider the relaxed energy introduced in [20] that depends on admissible pairs (E, u) of sets E and functions u defined only outside of E. For dimension three this energy appears in the study of the material voids in solids, where the pairs (E, u) are interpreted as the admissible configurations that consist of void regions E in the space and of displacements u of the atoms of the crystal. We provide the precise mathematical framework that guarantees the existence of minimal energy pairs (E, u). Then, we establish that for every minimal configuration (E, u), the function u is C1,gloc -regular outside an essentially closed subset of E. No hypothesis of starshapedness is assumed on the voids and all the results that are contained in [18] hold true for every dimension d ≥ 2. Key Words and Sentences: surface energy, elastic bulk energy, minimizing movements, evolution, gradient flow, motion by mean curvature, minimal configurations, existence, uniqueness, regularity, partial regularity, lower density bound, thin film

  17. The influence of ion beam rastering on the swelling of self-ion irradiated pure iron at 450 °C

    NASA Astrophysics Data System (ADS)

    Gigax, Jonathan G.; Aydogan, Eda; Chen, Tianyi; Chen, Di; Shao, Lin; Wu, Y.; Lo, W. Y.; Yang, Y.; Garner, F. A.

    2015-10-01

    Ion beam scanning or "rastering" is a technique that is frequently used to uniformly cover a larger specimen area during ion irradiation. In this study, we addressed the effects of rastered and defocused beams, using 3.5 MeV iron ions to irradiate pure iron at 450 °C to peak doses of 50 and 150 dpa. We focused on a frequency range relevant to pulsed fusion devices and show its importance to ion irradiation experiments used for simulating neutron damage. The beam was scanned at 15.6, 1.94, and 0.244 Hz and the resulting microstructure was compared with that produced by a non-rastered, defocused beam. At 150 dpa, the defocused beam case resulted in the highest observed void swelling of ∼12% at a depth of ∼700 nm, a depth short of the peak dose position at 1000 nm. The swelling at the peak dose position was significantly reduced by the defect imbalance phenomenon. A maximum swelling rate of ∼0.12%/dpa was measured in this specimen at a depth of 600 nm below the ion-incident surface. Rastering led to much lower swelling levels achieved at significantly lower swelling rates, with the greatest rate of decrease occurring below ∼1 Hz. Furthermore, the impact of the defect imbalance arising from interstitial injection and spatial distribution difference of initial interstitial and vacancy defects was strongly pronounced in the non-rastered case with a lesser effect observed with decreasing raster frequency.

  18. Magnetic relaxation: Coal swelling, extraction, pore size

    SciTech Connect

    Doetschman, D.C.

    1992-11-06

    The goals for year I of the grant were to extract the Argonne Coals, to swell them, to reswell their residues, to seal the various samples for measurements, to perform analyses of the samples and to measure their NMR decays. Because of an unexpected characteristic of the extraction process, more detailed analyses of the samples are being done than originally anticipated. The mass spectrometric analyses have not been completed. Because routine NMR analyses needed to be done in greater detail than anticipated, the NMR decay measurements have also been delayed. In order to offset these delays, all of the EPR samples, which were to have been examined in year III, have been prepared and a substantial proportion of the pulsed EPR measurements have been made.

  19. A simple model for the swelling of polymer networks

    SciTech Connect

    Painter, P.C.; Shenoy, S.L. )

    1993-07-15

    The Flory--Rehner approach to the solvent swelling of polymer networks is modified so as to abandon the affine deformation assumption. Instead, it is assumed that swelling occurs by a process of disinterspersion of cross-link junctions, and relationships between chain expansion and segment concentration are established using the ideas of de Gennes. Using this approach, we also examine osmotic deswelling, aspects of phase equilibria, and the maximum observed in differential swelling measurements.

  20. Partial discharges within two spherical voids in an epoxy resin

    NASA Astrophysics Data System (ADS)

    Illias, H. A.; Chen, G.; Bakar, A. H. A.; Mokhlis, H.; Tunio, M. A.

    2013-08-01

    A void in a dielectric insulation material may exist due to imperfection in the insulation manufacturing or long term stressing. Voids have been identified as one of the common sources of partial discharge (PD) activity within an insulation system, such as in cable insulation and power transformers. Therefore, it is important to study PD phenomenon within void cavities in insulation. In this work, a model of PD activity within two spherical voids in a homogeneous dielectric material has been developed using finite element analysis software to study the parameters affecting PD behaviour. The parameters that have been taken into account are the void surface conductivity, electron generation rate and the inception and extinction fields. Measurements of PD activity within two spherical voids in an epoxy resin under ac sinusoidal applied voltage have also been performed. The simulation results have been compared with the measurement data to validate the model and to identify the parameters affecting PD behaviour. Comparison between measurements of PD activity within single and two voids in a dielectric material have also been made to observe the difference of the results under both conditions.

  1. Void nucleation at elevated temperatures under cascade-damage irradiation

    NASA Astrophysics Data System (ADS)

    Semenov, A. A.; Woo, C. H.

    2002-07-01

    The effects on void nucleation of fluctuations respectively due to the randomness of point-defect migratory jumps, the random generation of free point defects in discrete packages, and the fluctuating rate of vacancy emission from voids are considered. It was found that effects of the cascade-induced fluctuations are significant only at sufficiently high total sink strength. At lower sink strengths and elevated temperatures, the fluctuation in the rate of vacancy emission is the dominant factor. Application of the present theory to the void nucleation in annealed pure copper neutron-irradiated at elevated temperatures with doses of 10-4-10-2 NRT dpa showed reasonable agreement between theory and experiment. This application also predicts correctly the temporal development of large-scale spatial heterogeneous microstructure during the void nucleation stage. Comparison between calculated and experimental void nucleation rates in neutron-irradiated molybdenum at temperatures where vacancy emission from voids is negligible showed reasonable agreement as well. It was clearly demonstrated that the athermal shrinkage of relatively large voids experimentally observable in molybdenum at such temperatures may be easily explained in the framework of the present theory.

  2. Theory of Electromigration of Faceted Voids in Aluminum Interconnects

    NASA Astrophysics Data System (ADS)

    Wickham, Lisa K.; Sethna, James P.

    1996-03-01

    Void--induced breakage of micron--sized aluminum wires is an important cause of failure in V.L.S.I. circuits. As an electromigration void travels through a grain in such a wire, a corresponding flux of atoms must leave the front face of the void and move to its other side. We give estimated upper bounds on this flux as a function of current density, temperature, various diffusion barriers, and surface step density. To learn about step density, we discuss ways in which the field changes equilibrium void shape and influences step nucleation rates. We conclude that the field enhances faceting on the leading void face, and find evidence for such behavior in previous experiments. In contrast, diffusion barriers from recent density functional calculations produce particle fluxes from our estimates which fall far below that given by observed void velocities, unless the step density on the leading void face is nearly one. We discuss strain, local heating, and impurity effects which might be responsible for enhanced mobility in real interconnects.

  3. Processes and controls in swelling anhydritic clay rocks

    NASA Astrophysics Data System (ADS)

    Mutschler, Thomas; Blum, Philipp; Butscher, Christoph

    2015-04-01

    Referring to the swelling of anhydritic clay rocks in tunneling, Leopold Müller-Salzburg noted in the third volume on tunneling of his fundamental text book on rock engineering that "a truly coherent explanation of these phenomena is still owing" (Müller-Salzburg 1978, p. 306). This valuation is still true after more than three decades of research in the field of swelling anhydritic clay rocks. One of the reasons is our limited knowledge of the processes involved in the swelling of such rocks, and of the geological, mineralogical, hydraulic, chemical and mechanical controls of the swelling. In this contribution, a review of processes in swelling anhydritic clay rocks and of associated controls is presented. Also numerical models that aim at simulating the swelling processes and controls are included in this review, and some of the remaining open questions are pointed out. By focusing on process-oriented work in this review, the presentation intends to stimulate further research across disciplines in the field of swelling anhydritic clay rocks to finally get a step further in managing the swelling problem in geotechnical engineering projects. Keywords: swelling; anhydritic clay rocks; review

  4. Clay swelling — A challenge in the oilfield

    NASA Astrophysics Data System (ADS)

    Anderson, R. L.; Ratcliffe, I.; Greenwell, H. C.; Williams, P. A.; Cliffe, S.; Coveney, P. V.

    2010-02-01

    Water-based drilling fluids are increasingly being used for oil and gas exploration, and are generally considered to be more environmentally acceptable than oil-based or synthetic-based fluids. Unfortunately, their use facilitates clay hydration and swelling. Clay swelling, which occurs in exposed sedimentary rock formations, can have an adverse impact on drilling operations and may lead to significantly increased oil well construction costs. Minimizing clay swelling is therefore an important area attracting a large amount of interest from both academia and industry. To effectively reduce the extent of clay swelling the mechanism by which clay minerals swell needs to be understood so that efficient swelling inhibitors may be developed. Acceptable clay swelling inhibitors must not only significantly reduce clay hydration, but must also meet increasingly stringent environmental guidelines while remaining cost effective. The development of these inhibitors, which are generally based upon water soluble polymers, therefore represents a challenge to oilfield geochemistry. This review aims to provide a comprehensive understanding of the mechanism by which clay minerals swell and what steps have been taken in the development of effective and environmentally friendly clay swelling inhibitors.

  5. Tracking the attenuation and nonbreaking dissipation of swells using altimeters

    NASA Astrophysics Data System (ADS)

    Jiang, Haoyu; Stopa, Justin E.; Wang, He; Husson, Romain; Mouche, Alexis; Chapron, Bertrand; Chen, Ge

    2016-02-01

    A method for systematically tracking swells across oceanic basins is developed by taking advantage of high-quality data from space-borne altimeters and wave model output. The evolution of swells is observed over large distances based on 202 swell events with periods ranging from 12 to 18 s. An empirical attenuation rate of swell energy of about 4 × 10-7 m-1 is estimated using these observations, and the nonbreaking energy dissipation rates of swells far away from their generating areas are also estimated using a point source model. The resulting acceptance range of nonbreaking dissipation rates is -2.5 to 5.0 × 10-7 m-1, which corresponds to a dissipation e-folding scales of at least 2000 km for steep swells, to almost infinite for small-amplitude swells. These resulting rates are consistent with previous studies using in-situ and synthetic aperture radar (SAR) observations. The frequency dispersion and angular spreading effects during swell propagation are discussed by comparing the results with other studies, demonstrating that they are the two dominant processes for swell height attenuation, especially in the near field. The resulting dissipation rates from these observations can be used as a reference for ocean engineering and wave modeling, and for related studies such as air-sea and wind-wave-turbulence interactions.

  6. The H I mass function and velocity width function of void galaxies in the Arecibo Legacy Fast ALFA Survey

    NASA Astrophysics Data System (ADS)

    Moorman, Crystal M.; Vogeley, Michael S.; Hoyle, Fiona; Pan, Danny C.; Haynes, Martha P.; Giovanelli, Riccardo

    2014-11-01

    We measure the H I mass function (HIMF) and velocity width function (WF) across environments over a range of masses, 7.2voids (void galaxies) and those that live in denser regions (wall galaxies). We find the void HIMF to be well fitted by a Schechter function with normalization Φ* = (1.37 ± 0.1) × 10-2y h3 Mpc-3, characteristic mass log(M_{H {I}^*/M_{⊙}) + 2 log h70 = 9.86 ± 0.02, and low-mass-end slope α = -1.29 ± 0.02. Similarly, for wall galaxies, we find best-fitting parameters Φ* = (1.82 ± 0.03) × 10-2 h3 Mpc-3, log(M_{H I}^*/M_{⊙}) + 2 log h70 = 10.00 ± 0.01, and α = -1.35 ± 0.01. We conclude that void galaxies typically have slightly lower H I masses than their non-void counterparts, which is in agreement with the dark matter (DM) halo mass function shift in voids assuming a simple relationship between DM mass and H I mass. We also find that the low-mass slope of the void HIMF is similar to that of the wall HIMF suggesting that there is either no excess of low-mass galaxies in voids or there is an abundance of intermediate H I mass galaxies. We fit a modified Schechter function to the ALFALFA void WF and determine its best-fitting parameters to be Φ* = 0.21 ± 0.1 h3 Mpc-3, log (W*) = 2.13 ± 0.3, α = 0.52 ± 0.5, and high-width slope β = 1.3 ± 0.4. For wall galaxies, the WF parameters are Φ* = 0.022 ± 0.009 h3 Mpc-3, log (W*) = 2.62 ± 0.5, α = -0.64 ± 0.2, and β = 3.58 ± 1.5. Because of large uncertainties on the void and wall WFs, we cannot conclude whether the WF is dependent on the environment.

  7. Local void and slip model used in BODYFIT-2PE

    SciTech Connect

    Chen, B.C.J.; Chien, T.H.; Kim, J.H.; Lellouche, G.S.

    1983-01-01

    A local void and slip model has been proposed for a two-phase flow without the need of fitting any empirical parameters. This model is based on the assumption that all bubbles have reached their terminal rise velocities in the two-phase region. This simple model seems to provide reasonable calculational results when compared with the experimental data and other void and slip models. It provides a means to account for the void and slip of a two-phase flow on a local basis. This is particularly suitable for a fine mesh thermal-hydraulic computer program such as BODYFIT-2PE.

  8. Contribution of polymeric swelling to the overall response of capacitive gas sensors.

    PubMed

    Altenberend, U; Oprea, A; Barsan, N; Weimar, U

    2013-08-01

    A new method for investigation of the swelling of polymers on exposure to gas or vapour has been devised and tested. It uses an optical profilometer (based on the chromatic aberration of a lens system) which is integrated into a computer-controlled gas-dosing and mixing setup. Gas and/or vapour concentration-dependent measurements have been carried out for thick layers of the polymers commonly used in gravimetric and capacitive gas sensors: poly(acrylic acid) (PAA), poly(vinyl pyrrolidone) (PVP), poly(ether urethane) (PEUT), and polydimethylsiloxane (PDMS). The thickness of PAA, PVP, and PEUT films changed significantly on exposure to humidity. These data have been used to derive the sorption isotherms of the respective polymers, which were found to be Henry or Flory-Huggins isotherms. Comparison of the geometrical (swelling) responses with capacitive responses revealed a strong correlation. The correlation, which occurs because both types of response are proportional to the water content of the polymer, is also valid for polymers with nonlinear gas responses. Finally the geometrical and electrical characteristics of the capacitive samples were used to explain the dependence of the capacitive response of different polymers on the concentration of the target gas or vapour. In this way was deduced that PDMS, which does not swell on exposure to humidity, swells in the presence of 2,3-dimethylpentane, for which no profilometer evaluations are yet available.

  9. Effect of ion beam parameters on engineering of nanoscale voids and their stability under post-growth annealing

    NASA Astrophysics Data System (ADS)

    Hooda, Sonu; Khan, S. A.; Satpati, B.; Stange, D.; Buca, D.; Bala, M.; Pannu, C.; Kanjilal, D.; Kabiraj, Debdulal

    2016-03-01

    Swift heavy ion (SHI) irradiation of damaged germanium (d-Ge) layer results in porous structure with voids aligned along ion trajectory due to local melting and resolidification during high electronic energy deposition. The present study focuses on the irradiation temperature- and incident angle-dependent growth dynamics and shape evolution of these voids due to 100 MeV Ag ions irradiation. The d-Ge layers were prepared by multiple low-energy Ar ion implantations in single crystalline Ge with damage formation of ~7 displacements per atom. Further, these d-Ge layers were irradiated using 100 MeV Ag ions at two different temperatures (77 and 300 K) and three different angles (7°, 30° and 45°). After SHI irradiation, substantial volume expansion of d-Ge layer is detected which is due to formation of nanoscale voids. The volume expansion is observed to be more in the samples irradiated at 77 K as compared to 300 K at a given irradiation fluence. It is observed that the voids are of spherical shape at low ion irradiation fluence. The voids grow in size and change their shape from spherical to prolate spheroid with increasing ion fluence. The major axis of spheroid is observed to be aligned approximately along the ion beam direction which has been confirmed by irradiation at three different angles. The change in shape is a consequence of combination of compressive strain and plastic flow developed due to thermal spike generated along ion track. Post-SHI irradiation annealing shows increase in size of voids and reversal of shape from prolate spheroid towards spherical through strain relaxation. The stability of voids was studied with the effect of post-growth annealing.

  10. The catalytic diversity of zeolites: confinement and solvation effects within voids of molecular dimensions.

    PubMed

    Gounder, Rajamani; Iglesia, Enrique

    2013-05-01

    The ability of molecular sieves to control the access and egress of certain reactants and products and to preferentially contain certain transition states while excluding others based on size were captured as shape selectivity concepts early in the history of zeolite catalysis. The marked consequences for reactivity and selectivity, specifically in acid catalysis, have since inspired and sustained many discoveries of novel silicate frameworks and driven the engineering of hierarchical structures and void size to influence catalysis. The catalytic diversity of microporous voids is explored and extended here in the context of their solvating environments, wherein voids act as hosts and stabilize guests, whether reactive intermediates or transition states, by van der Waals forces. We use specific examples from acid catalysis, including activation of C-C and C-H bonds in alkanes, alkylation and hydrogenation of alkenes, carbonylation of dimethyl ether, and elimination and homologation reactions of alkanols and ethers, which involve transition states and adsorbed precursors of varying size and composition. Mechanistic interpretations of measured turnover rates enable us to assign precise chemical origins to kinetic and thermodynamic constants in rate equations and, in turn, to identify specific steps and intermediates that determine the free energy differences responsible for chemical reactivity and selectivity. These free energy differences reflect the stabilization of transition states and their relevant precursors via electrostatic interactions that depend on acid strength and van der Waals interactions that depend on confinement within voids. Their respective contributions to activation free energies are examined by Born-Haber thermochemical cycles by considering plausible transition states and the relevant precursors. These examples show that zeolite voids solvate transition states and precursors differently, and markedly so for guest moieties of different size and

  11. Quantifying Void Ratio in Granular Materials Using Voronoi Tessellation

    NASA Technical Reports Server (NTRS)

    Alshibli, Khalid A.; El-Saidany, Hany A.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    Voronoi technique was used to calculate the local void ratio distribution of granular materials. It was implemented in an application-oriented image processing and analysis algorithm capable of extracting object edges, separating adjacent particles, obtaining the centroid of each particle, generating Voronoi polygons, and calculating the local void ratio. Details of the algorithm capabilities and features are presented. Verification calculations included performing manual digitization of synthetic images using Oda's method and Voronoi polygon system. The developed algorithm yielded very accurate measurements of the local void ratio distribution. Voronoi tessellation has the advantage, compared to Oda's method, of offering a well-defined polygon generation criterion that can be implemented in an algorithm to automatically calculate local void ratio of particulate materials.

  12. Influence of voids on the strength of wrought materials

    NASA Technical Reports Server (NTRS)

    Shaw, M. C.; Pai, D. M.

    1985-01-01

    Three-dimensional voids, which are present in most materials, may be satisfactorily modelled by two-dimensional holes (i.e., cylindrical voids) in sheet metal. In this study, the influence of certain orientations and shapes of voids upon the mechanical properties and fracture behavior of certain ductile materials has been studied. The presence of voids is found to exert a negligible influence on the ultimate tensile strength, owing to plastic flow neutralizing the stress intensification present before yielding occurs. The shape and orientation of the defects, however, are seen to play an important role relative to strain at fracture. The maximum intensified tensile stress criterion which holds for brittle materials is found to apply to ductile materials as well.

  13. Void Closure in Complex Plasmas under Microgravity Conditions.

    PubMed

    Lipaev, A M; Khrapak, S A; Molotkov, V I; Morfill, G E; Fortov, V E; Ivlev, A V; Thomas, H M; Khrapak, A G; Naumkin, V N; Ivanov, A I; Tretschev, S E; Padalka, G I

    2007-06-29

    We describe the first observation of a void closure in complex plasma experiments under microgravity conditions performed with the Plasma-Kristall (PKE-Nefedov) facility on board the International Space Station. The void--a grain-free region in the central part of the discharge where the complex plasma is generated--has been formed under most of the plasma conditions and thought to be an inevitable effect. However, we demonstrate in this Letter that an appropriate tune of the discharge parameters allows the void to close. This experimental achievement along with its theoretical interpretation opens new perspectives in engineering new experiments with large quasi-isotropic void-free complex plasma clouds in microgravity conditions.

  14. Modeling Void Nucleation in Metals at High Strain-rates

    NASA Astrophysics Data System (ADS)

    Belak, J.; Bales, G. S.; Glosli, J.

    1997-08-01

    Isotropic tension is simulated in nanoscale polycrystalline metals using large-scale molecular dynamics. The nanocrystalline metal is fabricated on the computer by growing randomly oriented grains from random positions or lattice positions in the simulation cell. Constant volume strain rates of 10^7 - 10^9 are considered for systems ranging from 10^5 - 10^7 atoms using an EAM interatomic potential. The spacing between voids for room temperature simulations is found to scale approximately as l ~ 0.005 * Cs / dotɛ, where Cs is the sound speed and dotɛ is the strain rate. The growth of small voids is simulated by cutting a void out of the simulation cell and repeating the isotropic expansion. Results are presented for several microstructures and void sizes and compared to macroscopic models.

  15. Void control in the crystallization of lithium fluoride

    NASA Technical Reports Server (NTRS)

    Jaworske, Donald A.; Perry, William D.

    1991-01-01

    The effect of tungsten-coated graphite fibers on the radiant heat transfer characteristics of salt-fiber composites was studied by measuring the onset of melting as a function of applied furnace power. As the fiber concentration was increased from 0 to 5.40 percent fiber by weight, the furnace temperature required to melt the lithium fluoride also increased. Upon cooling, each of the crystalline salt-fiber composites were cut open with a diamond saw to expose the void. Optical photographs of the voids revealed a trend in void location and size, with the largest void, and the least change in the outer dimension of the boule upon cooling, occurring in the sample with the most fiber.

  16. Void Closure in Complex Plasmas under Microgravity Conditions

    SciTech Connect

    Lipaev, A. M.; Molotkov, V. I.; Fortov, V. E.; Khrapak, A. G.; Naumkin, V. N.; Khrapak, S. A.; Morfill, G. E.; Ivlev, A. V.; Thomas, H. M.; Ivanov, A. I.; Tretschev, S. E.; Padalka, G. I.

    2007-06-29

    We describe the first observation of a void closure in complex plasma experiments under microgravity conditions performed with the Plasma-Kristall (PKE-Nefedov) facility on board the International Space Station. The void--a grain-free region in the central part of the discharge where the complex plasma is generated--has been formed under most of the plasma conditions and thought to be an inevitable effect. However, we demonstrate in this Letter that an appropriate tune of the discharge parameters allows the void to close. This experimental achievement along with its theoretical interpretation opens new perspectives in engineering new experiments with large quasi-isotropic void-free complex plasma clouds in microgravity conditions.

  17. Stress-induced voiding study in integrated circuit interconnects

    NASA Astrophysics Data System (ADS)

    Hou, Yuejin; Tan, Cher Ming

    2008-07-01

    An analytical equation for an ultralarge-scale integration interconnect lifetime due to stress-induced voiding (SIV) is derived from the energy perspective. It is shown that the SIV lifetime is strongly dependent on the passivation quality at the cap layer/interconnect interface, the confinement effect by the surrounding materials to the interconnects, and the available diffusion paths in the interconnects. Contrary to the traditional power-law creep model, we find that the temperature exponent in SIV lifetime formulation is determined by the available diffusion paths for the interconnect atoms and the interconnect geometries. The critical temperature for the SIV is found to be independent of passivation integrity and dielectric confinement effect. Actual stress-free temperature (SFT) during the SIV process is also found to be different from the dielectric/cap layer deposition temperature or the final annealing temperature of the metallization, and it can be evaluated analytically once the activation energy, temperature exponent and critical temperature are determined experimentally. The smaller actual SFT indicates that a strong stress relaxation occurs before the high temperature storage test. Our results show that our SIV lifetime model can be used to predict the SIV lifetime in nano-interconnects.

  18. Effect of Void Distribution Parameter and Axial Power Profile on Boiling Water Reactor Bifurcation Characteristics

    SciTech Connect

    Bragt, D.D.B. van; Rizwan-uddin; Hagen, T.H.J.J. van der

    2000-02-15

    Bifurcation analyses of the impact of the void distribution parameter C{sub 0} and the axial power profile on the stability of boiling water reactors (BWRs) are reported. Bifurcation characteristics of heated channels (without nuclear feedback) appear to be very sensitive to the axial power profile. A turning point bifurcation was detected for a (symmetrically) peaked axial power profile. This kind of bifurcation does not occur for a uniformly heated channel.Both supercritical and subcritical Hopf bifurcations were encountered in a (nuclear-coupled) reactor system, depending on the strength of the void reactivity feedback. Subcritical bifurcations become less likely to occur as C{sub 0} is significantly larger than unity. In BWRs with a strong nuclear feedback, the oscillation amplitude of limit cycles caused by a supercritical bifurcation is very sensitive to both C{sub 0} and the axial power profile.

  19. Elastic, permeability and swelling properties of human intervertebral disc tissues: A benchmark for tissue engineering.

    PubMed

    Cortes, Daniel H; Jacobs, Nathan T; DeLucca, John F; Elliott, Dawn M

    2014-06-27

    The aim of functional tissue engineering is to repair and replace tissues that have a biomechanical function, i.e., connective orthopaedic tissues. To do this, it is necessary to have accurate benchmarks for the elastic, permeability, and swelling (i.e., biphasic-swelling) properties of native tissues. However, in the case of the intervertebral disc, the biphasic-swelling properties of individual tissues reported in the literature exhibit great variation and even span several orders of magnitude. This variation is probably caused by differences in the testing protocols and the constitutive models used to analyze the data. Therefore, the objective of this study was to measure the human lumbar disc annulus fibrosus (AF), nucleus pulposus (NP), and cartilaginous endplates (CEP) biphasic-swelling properties using a consistent experimental protocol and analyses. The testing protocol was composed of a swelling period followed by multiple confined compression ramps. To analyze the confined compression data, the tissues were modeled using a biphasic-swelling model, which augments the standard biphasic model through the addition of a deformation-dependent osmotic pressure term. This model allows considering the swelling deformations and the contribution of osmotic pressure in the analysis of the experimental data. The swelling stretch was not different between the disc regions (AF: 1.28±0.16; NP: 1.73±0.74; CEP: 1.29±0.26), with a total average of 1.42. The aggregate modulus (Ha) of the extra-fibrillar matrix was higher in the CEP (390kPa) compared to the NP (100kPa) or AF (30kPa). The permeability was very different across tissue regions, with the AF permeability (64 E(-16)m(4)/Ns) higher than the NP and CEP (~5.5 E(-16)m(4)/Ns). Additionally, a normalized time-constant (3000s) for the stress relaxation was similar for all the disc tissues. The properties measured in this study are important as benchmarks for tissue engineering and for modeling the disc's mechanical

  20. Void morphology in polyethylene/carbon black composites

    SciTech Connect

    Marr, D.W.M.; Wartenberg, M.; Schwartz, K.B.

    1996-12-31

    A combination of small angle neutron scattering (SANS) and contrast matching techniques is used to determine the size and quantity of voids incorporated during fabrication of polyethylene/carbon black composites. The analysis used to extract void morphology from SANS data is based on the three-phase model of microcrack determination via small angle x-rayscattering (SAXS) developed by W.Wu{sup 12} and applied to particulate reinforced composites.

  1. Excursion sets and non-Gaussian void statistics

    SciTech Connect

    D'Amico, Guido; Musso, Marcello; Paranjape, Aseem; Norena, Jorge

    2011-01-15

    Primordial non-Gaussianity (NG) affects the large scale structure (LSS) of the Universe by leaving an imprint on the distribution of matter at late times. Much attention has been focused on using the distribution of collapsed objects (i.e. dark matter halos and the galaxies and galaxy clusters that reside in them) to probe primordial NG. An equally interesting and complementary probe however is the abundance of extended underdense regions or voids in the LSS. The calculation of the abundance of voids using the excursion set formalism in the presence of primordial NG is subject to the same technical issues as the one for halos, which were discussed e.g. in Ref. [51][G. D'Amico, M. Musso, J. Norena, and A. Paranjape, arXiv:1005.1203.]. However, unlike the excursion set problem for halos which involved random walks in the presence of one barrier {delta}{sub c}, the void excursion set problem involves two barriers {delta}{sub v} and {delta}{sub c}. This leads to a new complication introduced by what is called the 'void-in-cloud' effect discussed in the literature, which is unique to the case of voids. We explore a path integral approach which allows us to carefully account for all these issues, leading to a rigorous derivation of the effects of primordial NG on void abundances. The void-in-cloud issue, in particular, makes the calculation conceptually rather different from the one for halos. However, we show that its final effect can be described by a simple yet accurate approximation. Our final void abundance function is valid on larger scales than the expressions of other authors, while being broadly in agreement with those expressions on smaller scales.

  2. Void Points, Rosettes, and a Brief History of Planetary Astronomy

    NASA Astrophysics Data System (ADS)

    Kosso, Peter

    2013-12-01

    Almost all models of planetary orbits, from Aristotle through Newton, include void points, empty points in space that have an essential role in defining the orbit. By highlighting the role of these void points, as well as the rosette pattern of the orbit that often results, I bring out different features in the history of planetary astronomy and place a different emphasis on its revolutionary changes, different from those rendered in terms of epicycles or the location of the earth.

  3. Role of subcutaneous apomorphine in parkinsonian voiding dysfunction.

    PubMed

    Christmas, T J; Kempster, P A; Chapple, C R; Frankel, J P; Lees, A J; Stern, G M; Milroy, E J

    Ten patients with Parkinson's disease and urinary symptoms underwent urodynamic assessments before and after subcutaneous administration of the dopamine receptor agonist apomorphine. Voiding efficiency improved after apomorphine injection, with an increase in mean and maximum flow rates in nine patients and reduction in post-micturition residual volume in six. Although the effect on detrusor behaviour was variable, subcutaneous apomorphine may be of use in both the assessment and treatment of voiding dysfunction in patients with Parkinson's disease.

  4. Use of biofeedback in treatment of psychogenic voiding dysfunction.

    PubMed

    Christmas, T J; Noble, J G; Watson, G M; Turner-Warwick, R T

    1991-01-01

    A young man with psychologic problems and a long history of social inadequacy presented with voiding dysfunction. Videocystometrography revealed a normal filling phase and normal initiation of voiding interrupted by considerable straining by the patient and marked sphincter electromyographic (EMG) activity. Temporary amelioration was achieved by infiltration of the sphincter with lignocaine hydrochloride and by biofeedback therapy. In such cases optimal results are expected from long-term behavioral therapy.

  5. Analysis and prediction of ocean swell using instrumented buoys

    NASA Technical Reports Server (NTRS)

    Mettlach, Theodore; Wang, David; Wittmann, Paul

    1994-01-01

    During the period 20-23 September 1990, the remnants of Supertyphoon Flo moved into the central North Pacific Ocean with sustained wind speeds of 28 m/s. The strong wind and large fetch area associated with this storm generated long-period swell that propagated to the west coast of North America. National Data Buoy Center moored-buoy stations, located in a network that ranged from the Gulf of Alaska to the California Bight, provided wave spectral estimates of the swell from this storm. The greatest dominant wave periods measured were approximately 20-25 s, and significant wave heights measured ranged from 3 to 8 m. Wave spectra from an array of three nondirectional buoys are used to find the source of the long-period swell. Directional wave spectra from a heave-pitch-roll buoy are also used to make an independent estimate of the source of the swell. The ridge-line method, using time-frequency contour plots of wave spectral energy density, is used to determine the time of swell generation, which is used with the appropriate surface pressure analysis to infer the swell generation area. The diagnosed sources of the swell are also compared with nowcasts from the Global Spectral Ocean Wave Model of the Fleet Numerical Oceanography Center. A simple method of predicting the propagation of ocean swell, by applying a simple kinematic model of wave propagation to the estimated point and time source, is demonstrated.

  6. Nanoscale Electrodes for Flexible Electronics by Swelling Controlled Cracking.

    PubMed

    Zhao, Qiang; Wang, Wenjun; Shao, Jinyou; Li, Xiangming; Tian, Hongmiao; Liu, Lu; Mei, Xuesong; Ding, Yucheng; Lu, Bingheng

    2016-08-01

    Nanogap electrodes are realized using pre-patterned electrodes and a swelling controlled cracking method. Parallel fabrication of nanogap electrodes on flexible substrates can be achieved using this method. This swelling-controlled cracking method is promising for fabricating high-performance flexible electronics. UV photodetectors with ZnO nanoparticle-bridged nanogap electrodes exhibit high responsivity and external quantum efficiency.

  7. Nanoscale Electrodes for Flexible Electronics by Swelling Controlled Cracking.

    PubMed

    Zhao, Qiang; Wang, Wenjun; Shao, Jinyou; Li, Xiangming; Tian, Hongmiao; Liu, Lu; Mei, Xuesong; Ding, Yucheng; Lu, Bingheng

    2016-08-01

    Nanogap electrodes are realized using pre-patterned electrodes and a swelling controlled cracking method. Parallel fabrication of nanogap electrodes on flexible substrates can be achieved using this method. This swelling-controlled cracking method is promising for fabricating high-performance flexible electronics. UV photodetectors with ZnO nanoparticle-bridged nanogap electrodes exhibit high responsivity and external quantum efficiency. PMID:27197807

  8. Weak lensing by voids in modified lensing potentials

    SciTech Connect

    Barreira, Alexandre; Cautun, Marius; Li, Baojiu; Baugh, Carlton M.; Pascoli, Silvia E-mail: m.c.cautun@durham.ac.uk E-mail: c.m.baugh@durham.ac.uk

    2015-08-01

    We study lensing by voids in Cubic Galileon and Nonlocal gravity cosmologies, which are examples of theories of gravity that modify the lensing potential. We find voids in the dark matter and halo density fields of N-body simulations and compute their lensing signal analytically from the void density profiles, which we show are well fit by a simple analytical formula. In the Cubic Galileon model, the modifications to gravity inside voids are not screened and they approximately double the size of the lensing effects compared to GR. The difference is largely determined by the direct effects of the fifth force on lensing and less so by the modified density profiles. For this model, we also discuss the subtle impact on the force and lensing calculations caused by the screening effects of haloes that exist in and around voids. In the Nonlocal model, the impact of the modified density profiles and the direct modifications to lensing are comparable, but they boost the lensing signal by only ≈ 10%, compared with that of GR. Overall, our results suggest that lensing by voids is a promising tool to test models of gravity that modify lensing.

  9. A Least-Squares Transport Equation Compatible with Voids

    SciTech Connect

    Hansen, Jon; Peterson, Jacob; Morel, Jim; Ragusa, Jean; Wang, Yaqi

    2014-12-01

    Standard second-order self-adjoint forms of the transport equation, such as the even-parity, odd-parity, and self-adjoint angular flux equation, cannot be used in voids. Perhaps more important, they experience numerical convergence difficulties in near-voids. Here we present a new form of a second-order self-adjoint transport equation that has an advantage relative to standard forms in that it can be used in voids or near-voids. Our equation is closely related to the standard least-squares form of the transport equation with both equations being applicable in a void and having a nonconservative analytic form. However, unlike the standard least-squares form of the transport equation, our least-squares equation is compatible with source iteration. It has been found that the standard least-squares form of the transport equation with a linear-continuous finite-element spatial discretization has difficulty in the thick diffusion limit. Here we extensively test the 1D slab-geometry version of our scheme with respect to void solutions, spatial convergence rate, and the intermediate and thick diffusion limits. We also define an effective diffusion synthetic acceleration scheme for our discretization. Our conclusion is that our least-squares Sn formulation represents an excellent alternative to existing second-order Sn transport formulations

  10. Adhesive analysis of voids in class II composite resin restorations at the axial and gingival cavity walls restored under in vivo versus in vitro conditions

    PubMed Central

    Purk, John H.; Dusevich, Vladimir; Glaros, Alan; Eick, J. David

    2007-01-01

    Objectives Adhesive analysis, under the scanning electron microscope of microtensile specimens that failed through the adhesive interface, was conducted to evaluate the amount of voids present at the axial versus gingival cavity walls of class II composite restorations restored under in vivo and in vitro conditions. Methods Five patients received class II resin composite restorations, under in vivo and in vitro conditions. A total of 14 premolar teeth yielded 59 (n = 59) microtensile adhesive specimens that fractured through the adhesive interface. The fractured surfaces of all specimens were examined and the % area of voids was measured. Results Voids at the adhesive joint were highly predictive of bond strengths. An increase in the number of voids resulted in a decrease in the microtensile bond strength. The area of voids at the adhesive interface was as follows: in vivo axial 13.6 ± 25.6% (n = 12); in vivo gingival 48.8 ± 29.2% (n = 12); in vitro axial 0.0 ± 0.0% (n = 19) and in vitro gingival 11.7 ± 17.6% (n = 16). Significance Composite resin may bond differently to dentin depending upon the amount of voids and the cavity wall involved. The bond to the gingival wall was not as reliable as the bond to the axial wall. An increase in the amount of surface voids was a major factor for reducing microtensile bond strengths of adhesive to dentin. PMID:16950506

  11. The use of waveguide acoustic probes for void fraction measurement in the evaporator of BN-350-Type reactor

    SciTech Connect

    Melnikov, V.I.; Nigmatulin, B.I.

    1995-09-01

    The present paper deals with some results of the experimental studies which have been carried out to investigate the steam generation dynamics in the Field tubes of sodium-water evaporators used in the BN-350 reactors. The void fraction measurements have been taken with the aid of waveguide acoustic transducers manufactured in accordance with a specially designed technology (waveguide acoustic transducers-WAT technology). Presented in this paper also the transducer design and calibration methods, as well as the diagram showing transducers arrengment in the evaporator. The transducers under test featured a waveguide of about 4 m in length and a 200-mm long sensitive element (probe). Besides, this paper specifies the void fraction data obtained through measurements in diverse points of the evaporator. The studies revealed that the period of observed fluctuations in the void fraction amounted to few seconds and was largely dependent on the level of water in the evaporator.

  12. Skeletogenesis in the swell shark Cephaloscyllium ventriosum.

    PubMed

    Eames, B Frank; Allen, Nancy; Young, Jonathan; Kaplan, Angelo; Helms, Jill A; Schneider, Richard A

    2007-05-01

    Extant chondrichthyans possess a predominantly cartilaginous skeleton, even though primitive chondrichthyans produced bone. To gain insights into this peculiar skeletal evolution, and in particular to evaluate the extent to which chondrichthyan skeletogenesis retains features of an osteogenic programme, we performed a histological, histochemical and immunohistochemical analysis of the entire embryonic skeleton during development of the swell shark Cephaloscyllium ventriosum. Specifically, we compared staining properties among various mineralizing tissues, including neural arches of the vertebrae, dermal tissues supporting oral denticles and Meckel's cartilage of the lower jaw. Patterns of mineralization were predicted by spatially restricted alkaline phosphatase activity earlier in development. Regarding evidence for an osteogenic programme in extant sharks, a mineralized tissue in the perichondrium of C. ventriosum neural arches, and to a lesser extent a tissue supporting the oral denticle, displayed numerous properties of bone. Although we uncovered many differences between tissues in Meckel's cartilage and neural arches of C. ventriosum, both elements impart distinct tissue characteristics to the perichondral region. Considering the evolution of osteogenic processes, shark skeletogenesis may illuminate the transition from perichondrium to periosteum, which is a major bone-forming tissue during the process of endochondral ossification. PMID:17451531

  13. Skeletogenesis in the swell shark Cephaloscyllium ventriosum

    PubMed Central

    Eames, B Frank; Allen, Nancy; Young, Jonathan; Kaplan, Angelo; Helms, Jill A; Schneider, Richard A

    2007-01-01

    Extant chondrichthyans possess a predominantly cartilaginous skeleton, even though primitive chondrichthyans produced bone. To gain insights into this peculiar skeletal evolution, and in particular to evaluate the extent to which chondrichthyan skeletogenesis retains features of an osteogenic programme, we performed a histological, histochemical and immunohistochemical analysis of the entire embryonic skeleton during development of the swell shark Cephaloscyllium ventriosum. Specifically, we compared staining properties among various mineralizing tissues, including neural arches of the vertebrae, dermal tissues supporting oral denticles and Meckel's cartilage of the lower jaw. Patterns of mineralization were predicted by spatially restricted alkaline phosphatase activity earlier in development. Regarding evidence for an osteogenic programme in extant sharks, a mineralized tissue in the perichondrium of C. ventriosum neural arches, and to a lesser extent a tissue supporting the oral denticle, displayed numerous properties of bone. Although we uncovered many differences between tissues in Meckel's cartilage and neural arches of C. ventriosum, both elements impart distinct tissue characteristics to the perichondral region. Considering the evolution of osteogenic processes, shark skeletogenesis may illuminate the transition from perichondrium to periosteum, which is a major bone-forming tissue during the process of endochondral ossification. PMID:17451531

  14. Skeletogenesis in the swell shark Cephaloscyllium ventriosum.

    PubMed

    Eames, B Frank; Allen, Nancy; Young, Jonathan; Kaplan, Angelo; Helms, Jill A; Schneider, Richard A

    2007-05-01

    Extant chondrichthyans possess a predominantly cartilaginous skeleton, even though primitive chondrichthyans produced bone. To gain insights into this peculiar skeletal evolution, and in particular to evaluate the extent to which chondrichthyan skeletogenesis retains features of an osteogenic programme, we performed a histological, histochemical and immunohistochemical analysis of the entire embryonic skeleton during development of the swell shark Cephaloscyllium ventriosum. Specifically, we compared staining properties among various mineralizing tissues, including neural arches of the vertebrae, dermal tissues supporting oral denticles and Meckel's cartilage of the lower jaw. Patterns of mineralization were predicted by spatially restricted alkaline phosphatase activity earlier in development. Regarding evidence for an osteogenic programme in extant sharks, a mineralized tissue in the perichondrium of C. ventriosum neural arches, and to a lesser extent a tissue supporting the oral denticle, displayed numerous properties of bone. Although we uncovered many differences between tissues in Meckel's cartilage and neural arches of C. ventriosum, both elements impart distinct tissue characteristics to the perichondral region. Considering the evolution of osteogenic processes, shark skeletogenesis may illuminate the transition from perichondrium to periosteum, which is a major bone-forming tissue during the process of endochondral ossification.

  15. Effects of Lateral Funiculus Sparing, Spinal Lesion Level, and Gender on Recovery of Bladder Voiding Reflexes and Hematuria in Rats

    PubMed Central

    Ferrero, Sunny L.; Brady, Tiffany D.; Dugan, Victoria P.; Armstrong, James E.; Hubscher, Charles H.

    2015-01-01

    Abstract Deficits in bladder function are complications following spinal cord injury (SCI), severely affecting quality of life. Normal voiding function requires coordinated contraction of bladder and urethral sphincter muscles dependent upon intact lumbosacral reflex arcs and integration of descending and ascending spinal pathways. We previously reported, in electrophysiological recordings, that segmental reflex circuit neurons in anesthetized male rats were modulated by a bilateral spino-bulbo-spinal pathway in the mid-thoracic lateral funiculus. In the present study, behavioral measures of bladder voiding reflexes and hematuria (hemorrhagic cystitis) were obtained to assess the correlation of plasticity-dependent recovery to the degree of lateral funiculus sparing and mid-thoracic lesion level. Adult rats received mid-thoracic-level lesions at one of the following severities: complete spinal transection; bilateral dorsal column lesion; unilateral hemisection; bilateral dorsal hemisection; a bilateral lesion of the lateral funiculi and dorsal columns; or a severe contusion. Voiding function and hematuria were evaluated by determining whether the bladder was areflexic (requiring manual expression, i.e., “crede maneuver”), reflexive (voiding initiated by perineal stroking), or “automatic” (spontaneous voiding without caretaker assistance). Rats with one or both lateral funiculi spared (i.e., bilateral dorsal column lesion or unilateral hemisection) recovered significantly faster than animals with bilateral lateral funiculus lesions, severe contusion, or complete transection. Bladder reflex recovery time was significantly slower the closer a transection lesion was to T10, suggesting that proximity to the segmental sensory and sympathetic innervation of the upper urinary tract (kidney, ureter) should be avoided in the choice of lesion level for SCI studies of micturition pathways. In addition, hematuria duration was significantly longer in males, compared to

  16. Influence of ethanol on swelling and release behaviors of Carbopol(®)-based tablets.

    PubMed

    Rahim, Safwan Abdel; Al-Ghazawi, Mutasim; Al-Zoubi, Nizar

    2013-01-01

    The aim of this work was to investigate the effect of ethanol on the in vitro swelling and release behaviors of Carbopol(®)-based tablets. The swelling behavior of drug-free compacts and the release of model drugs (metformin HCl, caffeine and theophylline) from matrix tablets were evaluated in acidic and buffered media with 0, 20 and 40% (v/v) ethanol. Release data were analyzed by fitting to Higuchi and Peppas models and calculation of similarity factor (f2). ANOVA tests were performed to determine significant factors on swelling and release. It was found that ethanol affects swelling and erosion of drug-free Carbopol(®) compacts, and the effect was highly dependent on medium pH. For matrix tablets, no dose dumping due to ethanol was manifested. The release rate and mechanism, however, were significantly affected by ethanol concentration as indicated by ANOVA applied to the constant, KH, from Higuchi model and the exponent, n, from Peppas model, respectively. The effect of ethanol on release was further confirmed by similarity factor results, which indicated that ethanol led to different release profiles (f2 < 50) in seven of eight cases for matrices containing metformin HCl and in three of eight cases for matrices containing caffeine and theophylline.

  17. Effect of electrolytes on colloidal stability and swelling of hydroxypropyl cellulose microgels

    NASA Astrophysics Data System (ADS)

    Mithra, K.; Khandai, Santripti; Jena, Sidhartha S.

    2016-05-01

    Hydroxypropyl Cellulose (HPC) microgels were prepared by emulsion polymerization method. The volume phase transition temperature (VPTT) and swelling properties were investigated using Dynamic Light Scattering (DLS). The VPTT for the HPC microgels was found to be˜44°C. Microgel particles swelled˜'3' times of their original size on decreasing temperature from 50°C to 25 °C. In addition we have also studied the effect of salts, sodium nitrate and sodium bromide in the Hofmeister series on deswelling and colloidal stability of HPC microgels using DLS and turbidity measurements respectively. M icrogel particles swelled in presence of NaN03 when its concentration was increased from 10-4 to 0.5 M and deswelled beyond it. As oppose to this, swelling of microgels in presence of NaBr was seen only upto 10-3 M and beyond which deswelling of microgels was observed. The results obtained are consistent with Hofmeister series of anions. Turbidity results showed that the colloidal stability of HPC microgel dispersion was dependent on ionic strength and type of added salt. For both salts, stability of microgels was found to decrease with rise in salt concentration.

  18. Swelling of Superabsorbent Poly(Sodium-Acrylate Acrylamide) Hydrogels and Influence of Chemical Structure on Internally Cured Mortar

    NASA Astrophysics Data System (ADS)

    Krafcik, Matthew J.; Erk, Kendra A.

    Superabsorbent hydrogel particles show promise as internal curing agents for high performance concrete (HPC). These gels can absorb and release large volumes of water and offer a solution to the problem of self-dessication in HPC. However, the gels are sensitive to ions naturally present in concrete. This research connects swelling behavior with gel-ion interactions to optimize hydrogel performance for internal curing, reducing the chance of early-age cracking and increasing the durability of HPC. Four different hydrogels of poly(sodium-acrylate acrylamide) are synthesized and characterized with swelling tests in different salt solutions. Depending on solution pH, ionic character, and gel composition, diffrerent swelling behaviors are observed. As weight percent of acrylic acid increases, gels demonstrate higher swelling ratios in reverse osmosis water, but showed substantially decreased swelling when aqueous cations are present. Additionally, in multivalent cation solutions, overshoot peaks are present, whereby the gels have a peak swelling ratio but then deswell. Multivalent cations interact with deprotonated carboxylic acid groups, constricting the gel and expelling water. Mortar containing hydrogels showed reduced autogenous shrinkage and increased relative humidity.

  19. High resolution interferometry as a tool for characterization of swelling of weakly charged hydrogels subjected to amphiphile and cyclodextrin exposure.

    PubMed

    Gao, Ming; Gawel, Kamila; Stokke, Bjørn Torger

    2013-01-15

    A high resolution interferometric technique was used to determine swelling behavior of weakly charged polyacrylamide hydrogels in the presence of oppositely charged surfactants and subsequent exposure to cyclodextrins. Hydrogels of copolymerized acrylamide and 2-acrylamido-2-methyl-1-propanesulfonic acid (0.22, 0.44, 0.88 mol%) crosslinked with bisacrylamide (3, 6, 12 mol%) were employed. The equilibrium swelling and swelling kinetics of the hydrogels were determined with 2nm resolution of the optical length and sampled at approximately 1 Hz. These properties were determined for the hydrogels exposed to cationic surfactants dodecyltrimethylammonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB) at concentrations from 10(-7) up to 2×10(-3)M. The distribution of surfactant within one AAM-co-AMPSA hydrogel equilibrated in CTAB/perylene solution was investigated by confocal laser scanning microscopy. Hydrogels equilibrated at selected surfactant concentrations were subsequently exposed to cyclodextrins (α-CD, β-CD, methyl-β-CD and γ-CD) forming inclusion complexes with the surfactants. The results show different types of behavior for the two surfactants used, arising from the difference in the length of surfactant hydrophobic tail. The changes in the surfactant induced swelling of the hydrogels are suggested to arise from the net effect of electrostatic screening of sulfonic acid-amide group interactions and surfactant micellization. Hydrogels with the largest charge density and the lowest crosslink density yielded the most pronounced changes in swelling properties on exposure to DTAB or CTAB. The hydrogels displayed swelling kinetics on stepwise changes in surfactant concentrations that depended on the surfactant concentration range. The high resolution monitoring of hydrogel swelling associated with supramolecular complex formation in three-component systems hydrogel-amphiphilic molecule-cyclodextrin provides more details on the swelling behavior than

  20. 21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Resorbable calcium salt bone void filler device... salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device is... entitled “Class II Special Controls Guidance: Resorbable Calcium Salt Bone Void Filler Device; Guidance...

  1. Void Management in MEPHISTO and Other Space Experiments

    NASA Technical Reports Server (NTRS)

    deGroh, Henry C., III; Johnston, J. Christopher; Wei, Bingbo

    1998-01-01

    The second flight of NASA's Shuttle Flight experiment program known as MEPHISTO suffered from a void in the liquid portion of the sample, even though a piston arrangement was in place to keep the ampoule filled. In preparations for the next flight of the MEPHISTO furnace an animated computer program, called MEPHISTO Volume Visualizer (MVV), was written to help avoid the formation of unwanted voids. A piston system on MEPHISTO has the ability to move approximately 5 mm in compression, to accommodate expansion of the solid during heating; then from the completely compressed position, the piston can move up to 25 mm in towards the sample, effectively making the ampoule smaller and hopefully eliminating any voids. Due to the nature of the piston design and ampoule and sample arrangement, the piston has gotten stuck during normal directional solidification; this creates the risk of a void. To eliminate such a void, the liquid in the hot zones of the furnace can be heated, thereby expanding the liquid and consuming any void. The problem with this approach is that if the liquid is heated too much an overpressure could result, breaking the ampoule and ending the experiment catastrophically. The MVV has been found to be a useful tool in the assessment of the risks associated with the formation of a void and the additional heating of the liquid in the hot zone of this Bridgman type furnace. The MVV software will be discussed and copies available; it is written in the Delphi 2 programming language and runs under Windows 95 and NT. The strategies used in other flight experiments, such as the Isothermal Dendritic Growth Experiment, will also be presented.

  2. Swelling kinetics of poly(N-isopropylacrylamide) gel.

    PubMed

    Andersson, M; Axelsson, A; Zacchi, G

    1998-01-01

    In many gel applications the swelling and shrinking kinetics are very important, e.g. in controlled/slow release, where the kinetics determined the rate of out-diffusion of the active component, and in gel extraction where the gel is swollen and shrunk several times. In this study swelling kinetics of poly(N-isopropylacrylamide) gel (NiPAAm gel) was determined by monitoring the swelling process using a stereo microscope and a video camera. The swelling of spherical gel bodies could conveniently be studied after a temperature change. The results obtained were treated according to the approach of Tanaka and Fillmore, in which the swelling and shrinking of a gel is described as a motion of the gel network according to the diffusion equation. This was shown to be valid when the temperature changes are kept below the critical point of the gel. However, the model fails to describe the shrinking process when passing from below to above the critical temperature. The collective diffusion coefficient (D), defined as the osmotic bulk modulus divided by the friction factor, was determined by fitting to the experimental data. D was found to increase with temperature according to the Wilke-Chang relation D = 2.0.10(-11) + 7.6.10(-17).T/mu. The results were used to simulate the swelling/shrinking process. The simulations show the importance of having sufficiently small gel bodies to achieve a short swelling time.

  3. Two distinct signaling pathways participate in auxin-induced swelling of pea epidermal protoplasts.

    PubMed

    Yamagami, Mutsumi; Haga, Ken; Napier, Richard M; Iino, Moritoshi

    2004-02-01

    Protoplast swelling was used to investigate auxin signaling in the growth-limiting stem epidermis. The protoplasts of epidermal cells were isolated from elongating internodes of pea (Pisum sativum). These protoplasts swelled in response to auxin, providing the clearest evidence that the epidermis can directly perceive auxin. The swelling response to the natural auxin IAA showed a biphasic dose response curve but that to the synthetic auxin 1-naphthalene acetic acid (NAA) showed a simple bell-shaped dose response curve. The responses to IAA and NAA were further analyzed using antibodies raised against ABP1 (auxin-binding protein 1), and their dependency on extracellular ions was investigated. Two signaling pathways were resolved for IAA, an ABP1-dependent pathway and an ABP1-independent pathway that is much more sensitive to IAA than the former. The response by the ABP1 pathway was eliminated by anti-ABP1 antibodies, had a higher sensitivity to NAA, and did not depend on extracellular Ca(2+). In contrast, the response by the non-ABP1 pathway was not affected by anti-ABP1 antibodies, had no sensitivity to NAA, and depended on extracellular Ca(2+). The swelling by either pathway required extracellular K(+) and Cl(-). The auxin-induced growth of pea internode segments showed similar response patterns, including the occurrence of two peaks in the dose response curve for IAA and the difference in Ca(2+) requirements. It is suggested that two signaling pathways participate in auxin-induced internode growth and that the non-ABP1 pathway is more likely to be involved in the control of growth by constitutive concentrations of endogenous auxin. PMID:14764902

  4. Two Distinct Signaling Pathways Participate in Auxin-Induced Swelling of Pea Epidermal Protoplasts

    PubMed Central

    Yamagami, Mutsumi; Haga, Ken; Napier, Richard M.; Iino, Moritoshi

    2004-01-01

    Protoplast swelling was used to investigate auxin signaling in the growth-limiting stem epidermis. The protoplasts of epidermal cells were isolated from elongating internodes of pea (Pisum sativum). These protoplasts swelled in response to auxin, providing the clearest evidence that the epidermis can directly perceive auxin. The swelling response to the natural auxin IAA showed a biphasic dose response curve but that to the synthetic auxin 1-naphthalene acetic acid (NAA) showed a simple bell-shaped dose response curve. The responses to IAA and NAA were further analyzed using antibodies raised against ABP1 (auxin-binding protein 1), and their dependency on extracellular ions was investigated. Two signaling pathways were resolved for IAA, an ABP1-dependent pathway and an ABP1-independent pathway that is much more sensitive to IAA than the former. The response by the ABP1 pathway was eliminated by anti-ABP1 antibodies, had a higher sensitivity to NAA, and did not depend on extracellular Ca2+. In contrast, the response by the non-ABP1 pathway was not affected by anti-ABP1 antibodies, had no sensitivity to NAA, and depended on extracellular Ca2+. The swelling by either pathway required extracellular K+ and Cl–. The auxin-induced growth of pea internode segments showed similar response patterns, including the occurrence of two peaks in the dose response curve for IAA and the difference in Ca2+ requirements. It is suggested that two signaling pathways participate in auxin-induced internode growth and that the non-ABP1 pathway is more likely to be involved in the control of growth by constitutive concentrations of endogenous auxin. PMID:14764902

  5. Automated air-void system characterization of hardened concrete: Helping computers to count air-voids like people count air-voids---Methods for flatbed scanner calibration

    NASA Astrophysics Data System (ADS)

    Peterson, Karl

    Since the discovery in the late 1930s that air entrainment can improve the durability of concrete, it has been important for people to know the quantity, spacial distribution, and size distribution of the air-voids in their concrete mixes in order to ensure a durable final product. The task of air-void system characterization has fallen on the microscopist, who, according to a standard test method laid forth by the American Society of Testing and Materials, must meticulously count or measure about a thousand air-voids per sample as exposed on a cut and polished cross-section of concrete. The equipment used to perform this task has traditionally included a stereomicroscope, a mechanical stage, and a tally counter. Over the past 30 years, with the availability of computers and digital imaging, automated methods have been introduced to perform the same task, but using the same basic equipment. The method described here replaces the microscope and mechanical stage with an ordinary flatbed desktop scanner, and replaces the microscopist and tally counter with a personal computer; two pieces of equipment much more readily available than a microscope with a mechanical stage, and certainly easier to find than a person willing to sit for extended periods of time counting air-voids. Most laboratories that perform air-void system characterization typically have cabinets full of prepared samples with corresponding results from manual operators. Proponents of automated methods often take advantage of this fact by analyzing the same samples and comparing the results. A similar iterative approach is described here where scanned images collected from a significant number of samples are analyzed, the results compared to those of the manual operator, and the settings optimized to best approximate the results of the manual operator. The results of this calibration procedure are compared to an alternative calibration procedure based on the more rigorous digital image accuracy

  6. Effects of α1-adrenoceptor agonist phenylephrine on swelling-activated chloride currents in human atrial myocytes.

    PubMed

    Li, Yetao; Du, Xinling

    2015-02-01

    Swelling-activated chloride currents (ICl.swell) play an important role in cardiac electrophysiology and arrhythmogenesis. However, the regulation of these currents has not been clarified to date. In this research, we focused on the function of phenylephrine, an α1-adrenoceptor agonist, in the regulation of I(Cl.swell) in human atrial myocytes. We recorded I(Cl.swell) evoked by a hypotonic bath solution with the whole-cell patch-clamp technique. We found that I(Cl.swell) increased over time, and it was difficult to achieve absolute steady state. Phenylephrine potentiated I(Cl.swell) from -1.00 ± 0.51 pA/pF at -90 mV and 2.58 ± 1.17 pA/pF at +40 mV to -1.46 ± 0.70 and 3.84 ± 1.67 pA/pF, respectively (P < 0.05, n = 6), and the upward trend in ICl.swell was slowed after washout. This effect was concentration-dependent, and the α1-adrenoceptor antagonist prazosin shifted the dose-effect curve rightward. Addition of prazosin or the protein kinase C (PKC) inhibitor bisindolylmaleimide (BIM) attenuated the effect of phenylephrine. The PKC activator phorbol 12,13-dibutyrate (PDBu) activated I(Cl.swell) from -1.69 ± 1.67 pA/pF at -90 mV and 5.58 ± 6.36 pA/pF at +40 mV to -2.41 ± 1.95 pA/pF and 7.05 ± 6.99 pA/pF, respectively (P < 0.01 at -90 mV and P < 0.05 at +40 mV; n = 6). In conclusion, the α1-adrenoceptor agonist phenylephrine augmented I(Cl.swell), a result that differs from previous reports in other animal species. The effect was attenuated by BIM and mimicked by PDBu, which indicates that phenylephrine might modulate I(Cl,swell) in a PKC-dependent manner.

  7. Nuclear Energy Research Initiative Program (NERI) Quarterly Progress Report; New Design Equations for Swelling and Irradiation Creep in Generation IV Reactors

    SciTech Connect

    Wolfer, W G; Surh, M P; Garner, F A; Chrzan, D C; Schaldach, C; Sturgeon, J B

    2003-02-13

    The objectives of this research project are to significantly extend the theoretical foundation and the modeling of radiation-induced microstructural changes in structural materials used in Generation IV nuclear reactors, and to derive from these microstructure models the constitutive laws for void swelling, irradiation creep and stress-induced swelling, as well as changes in mechanical properties. The need for the proposed research is based on three major developments and advances over the past two decades. First, new experimental discoveries have been made on void swelling and irradiation creep which invalidate previous theoretical models and empirical constitutive laws for swelling and irradiation creep. Second, recent advances in computational methods and power make it now possible to model the complex processes of microstructure evolution over long-term neutron exposures. Third, it is now required that radiation-induced changes in structural materials over extended lifetimes be predicted and incorporated in the design of Generation IV reactors. Our approach to modeling and data analysis is a dual one in accord with both the objectives to simulate the evolution of the microstructure and to develop design equations for macroscopic properties. Validation of the models through data analysis is therefore carried out at both the microscopic and the macroscopic levels. For the microstructure models, we utilize the transmission electron microscopy results from steels irradiated in reactors and from model materials irradiated by neutrons as well as ion bombardments. The macroscopic constitutive laws will be tested and validated by analyzing density data, irradiation creep data, diameter changes of fuel elements, and post-irradiation tensile data. Validation of both microstructure models and macroscopic constitutive laws is a more stringent test of the internal consistency of the underlying science for radiation effects in structural materials for nuclear reactors.

  8. Seasonality of Ankle Swelling: Population Symptom Reporting Using Google Trends.

    PubMed

    Liu, Fangwei; Allan, G Michael; Korownyk, Christina; Kolber, Michael; Flook, Nigel; Sternberg, Harvey; Garrison, Scott

    2016-07-01

    In our experience, complaints of ankle swelling are more common in summer, typically from patients with no obvious cardiovascular disease. Surprisingly, this observation has never been reported. To objectively establish this phenomenon, we sought evidence of seasonality in the public's Internet searches for ankle swelling. Our data, obtained from Google Trends, consisted of all related Google searches in the United States from January 4, 2004, to January 26, 2016. Consistent with our expectations and confirmed by similar data for Australia, Internet searches for information on ankle swelling are highly seasonal (highest in midsummer), with seasonality explaining 86% of search volume variability.

  9. Molecular accessibility in solvent swelled coal. Quarterly report

    SciTech Connect

    Kispert, L.D.

    1992-11-01

    To expand the information base on molecular accessibility in solvent swelled coal, Argonne Premium Coal Samples (APCS) were swelled in polar, basic solvents before and after moisture loss and upon air oxidation. So far studies have been reported on the changes in pore size distribution as a function of temperature when polar basic swelling solvents are used. Additional studies employing EPR spin probe techniques performed on the breaking up of the hydrogen bonding between bedding planes were later confirmed by magnetic resonance imaging at Argonne National Lab and the University of Illinois.

  10. Seasonality of Ankle Swelling: Population Symptom Reporting Using Google Trends.

    PubMed

    Liu, Fangwei; Allan, G Michael; Korownyk, Christina; Kolber, Michael; Flook, Nigel; Sternberg, Harvey; Garrison, Scott

    2016-07-01

    In our experience, complaints of ankle swelling are more common in summer, typically from patients with no obvious cardiovascular disease. Surprisingly, this observation has never been reported. To objectively establish this phenomenon, we sought evidence of seasonality in the public's Internet searches for ankle swelling. Our data, obtained from Google Trends, consisted of all related Google searches in the United States from January 4, 2004, to January 26, 2016. Consistent with our expectations and confirmed by similar data for Australia, Internet searches for information on ankle swelling are highly seasonal (highest in midsummer), with seasonality explaining 86% of search volume variability. PMID:27401424

  11. Swelling and Contraction of Phaseolus Hypocotyl Mitochondria 1

    PubMed Central

    Earnshaw, M. J.; Truelove, B.

    1968-01-01

    Isolated Phaseolus mitochondria will swell spontaneously in buffered KCl and contract with an oxidizable substrate or ATP + Mg2+. The conditions under which the mitochondria are swollen affect subsequent contraction, substrate oxidation and ion accumulation, but not their oxidative phosphorylation ability. Bovine serum albumin reduces the rate of swelling and promotes substrate oxidation, contraction and ion accumulation. Swelling of these mitochondria is associated with the release of malic dehydrogenase and a loss of membrane integrity. The beneficial effects of bovine serum albumin in preserving the energy linked functions of Phaseolus mitochondria is discussed. PMID:16656729

  12. Autonomous robot for detecting subsurface voids and tunnels using microgravity

    NASA Astrophysics Data System (ADS)

    Wilson, Stacy S.; Crawford, Nicholas C.; Croft, Leigh Ann; Howard, Michael; Miller, Stephen; Rippy, Thomas

    2006-05-01

    Tunnels have been used to evade security of defensive positions both during times of war and peace for hundreds of years. Tunnels are presently being built under the Mexican Border by drug smugglers and possibly terrorists. Several have been discovered at the border crossing at Nogales near Tucson, Arizona, along with others at other border towns. During this war on terror, tunnels under the Mexican Border pose a significant threat for the security of the United States. It is also possible that terrorists will attempt to tunnel under strategic buildings and possibly discharge explosives. The Center for Cave and Karst Study (CCKS) at Western Kentucky University has a long and successful history of determining the location of caves and subsurface voids using microgravity technology. Currently, the CCKS is developing a remotely controlled robot which will be used to locate voids underground. The robot will be a remotely controlled vehicle that will use microgravity and GPS to accurately detect and measure voids below the surface. It is hoped that this robot will also be used in military applications to locate other types of voids underground such as tunnels and bunkers. It is anticipated that the robot will be able to function up to a mile from the operator. This paper will describe the construction of the robot and the use of microgravity technology to locate subsurface voids with the robot.

  13. SIMULATED VOID GALAXIES IN THE STANDARD COLD DARK MATTER MODEL

    SciTech Connect

    Kreckel, Kathryn; Ryan Joung, M.; Cen Renyue

    2011-07-10

    We analyze a (120 h{sup -1} Mpc){sup 3} adaptive mesh refinement hydrodynamic simulation that contains a higher resolution 31 x 31 x 35 h{sup -3} Mpc subvolume centered on a {approx}30 Mpc diameter void. Our detailed {approx}1 kpc resolution allows us to identify 1300 galaxies within this void to a limiting halo mass of {approx}10{sup 10} M{sub sun}. Nearly 1000 galaxies are found to be in underdense regions, with 300 galaxies residing in regions less than half the mean density of the simulation volume. We construct mock observations of the stellar and gas properties of these systems and reproduce the range of colors and luminosities observed in the Sloan Digital Sky Survey for nearby (z < 0.03) galaxies. We find no trends with density for the most luminous (M{sub r} < -18) galaxies, however our dwarf void galaxies (M{sub r} > -16), though they are less reliably resolved, typically appear bluer, with higher rates of star formation and specific star formation and lower mean stellar ages than galaxies in average density environments. We find a significant population of low-luminosity (M{sub r} {approx} -14) dwarf galaxies that is preferentially located in low-density regions and specifically in the void center. This population may help to reduce, but not remove, the discrepancy between the predicted and observed number of void galaxies.

  14. Constraints on Cosmology and Gravity from the Dynamics of Voids

    NASA Astrophysics Data System (ADS)

    Hamaus, Nico; Pisani, Alice; Sutter, P. M.; Lavaux, Guilhem; Escoffier, Stéphanie; Wandelt, Benjamin D.; Weller, Jochen

    2016-08-01

    The Universe is mostly composed of large and relatively empty domains known as cosmic voids, whereas its matter content is predominantly distributed along their boundaries. The remaining material inside them, either dark or luminous matter, is attracted to these boundaries and causes voids to expand faster and to grow emptier over time. Using the distribution of galaxies centered on voids identified in the Sloan Digital Sky Survey and adopting minimal assumptions on the statistical motion of these galaxies, we constrain the average matter content Ωm=0.281 ±0.031 in the Universe today, as well as the linear growth rate of structure f /b =0.417 ±0.089 at median redshift z ¯=0.57 , where b is the galaxy bias (68% C.L.). These values originate from a percent-level measurement of the anisotropic distortion in the void-galaxy cross-correlation function, ɛ =1.003 ±0.012 , and are robust to consistency tests with bootstraps of the data and simulated mock catalogs within an additional systematic uncertainty of half that size. They surpass (and are complementary to) existing constraints by unlocking cosmological information on smaller scales through an accurate model of nonlinear clustering and dynamics in void environments. As such, our analysis furnishes a powerful probe of deviations from Einstein's general relativity in the low-density regime which has largely remained untested so far. We find no evidence for such deviations in the data at hand.

  15. Surveying for Dwarf Galaxies Within Void FN8

    NASA Astrophysics Data System (ADS)

    McNeil, Stephen R.

    2016-06-01

    The dwarf galaxy population in low density volumes, or voids, is a test of galaxy formation models and how they treat dark matter; some models say dwarf galaxies cannot be in void centers while others say they can. Since it appears many dwarf galaxies are H-alpha emitters, a well-designed deep survey through a nearby void center will either find nothing, and thus constrain the population there to be at some percentage below the mean, or it will find H-alpha emitters and significantly challenge several otherwise successful theories. Either result is a significant step in better understanding galaxy formation and large-scale structure. In 2013, a redshifted H-alpha imaging survey was begun for dwarf galaxies with ‑14.0 ≤ Mr ≤ ‑12.0 in the heart and back of the void FN8. Our first results have been surprising, furnishing significantly more candidate objects than anticipated. Through the Gemini Fast Turnaround Program, seven spectrum have been obtained, with one spectrum being a strong candidate for habitation within the center of the void.

  16. On the origin of the voids in the galaxy distribution

    NASA Astrophysics Data System (ADS)

    Hoffman, Y.; Shaham, J.

    1982-11-01

    The distribution of galaxies on scales larger than approximately 10 Mpc/h seems to be characterized by large voids, (20-40) Mpc/h in diameter and of amplitude delta approximately -(0.7-0.8). It was previously argued that the mere existence of such voids poses a severe problem to all dissipationless clustering theories. Here it is shown that the voids may, in fact, be a natural outcome of a dissipationless clustering scenario if both adiabatic and isothermal density perturbations exist primordially. When the nonlinear evolution of spherical voids of this type is followed for adiabatic perturbations with an index n greater than -1, it is seen that they become surrounded by a shell of positive density contrast. Their structure is insensitive to Omega 0 while their dynamics is quite sensitive to it. The maximum peculiar velocity (relative to Hubble flow) within the void is found to be: v(p)/v(H) approximately (0.4-0.5) for Omega 0 = 1.0, approximately (0.2-0.25) for Omega 0 = 0.45, and approximately equal to or less than 0.09 for Omega 0 = 0.1.

  17. Swelling, irradiation creep and growth of pure rhenium irradiated with fast neutrons at 1030-1330 degrees C

    SciTech Connect

    Garner, F.A.; Toloczko, Mychailo B. ); Greenwood, Lawrence R. ); Eiholzer, Cheryl R. ); Paxton, M M.; Puigh, Raymond J.

    2000-01-01

    This paper discusses the results of two series of experiments conducted on pure hcp rhenium in the EBR-II and FFTF fast reactors. In FFTF, density change data were derived from open tubes and solid rods irradiated at temperatures and fluences in the range of 1020-1250?C and 4.4-8.3?1022 n cm-2, respectively (E > 0.1 MeV). Both density change and diametral change data were obtained from pressurized tubes irradiated in EBR-II to 0.65 and 5.1?1022 n cm-2 at temperatures between 1030?C and 1330?C. Analysis of the data shows that four concurrent processes contribute to the radiation-induced strains observed in these experiments. These are void swelling, transmutation-induced densification via production of osmium, irradiation creep and irradiation growth.

  18. MOELCULAR SIZE EXCLUSION BY SOIL ORGANIC MATERIALS ESTIMATED FROM THEIR SWELLING IN ORGANIC SOLVENTS

    EPA Science Inventory

    A published method previously developed to measure the swelling characteristics of pow dered coal samples has been adapted for swelling measurements on various peat, pollen, chain, and cellulose samples The swelling of these macromolecular materials is the volumetric manifestatio...

  19. Generation of Continental Rifts, Basins and Swells by Lithosphere Instabilities

    NASA Astrophysics Data System (ADS)

    Milelli, L.; Fourel, L.; Jaupart, C. P.

    2012-12-01

    blocks of finite size that became unstable due to cooling from above and describe the peculiar horizontal planform that developed. Dynamical behaviour depends on three dimensionless numbers, a Rayleigh number for the unstable block, a buoyancy number that scales the intrinsic density contrast to the thermal one and the aspect ratio of the block. Within the block, instability develops in two different ways in an outer annulus and in an inner region. In the outer annulus, upwellings and downwellings take the form of radial rolls spaced regularly. In the interior region, the planform adopts the more familiar form of polygonal cells. Translated to geological conditions, such instabilities should manifest themselves as linear rifts striking at a right angle to the continent-ocean boundary and an array of domal uplifts, volcanic swells and basins in the continental interior. The laboratory data lead to simple scaling laws for the dimensions and spacings of the convective structures. For the sub-continental lithospheric mantle, these dimensions and distances take values in the 500-1000 km range, close to geological examples. The large intrinsic buoyancy of Archean lithospheric roots prevents this type of instability, which explains why the widespread volcanic activity that currently affects Western Africa is confined to post-Archean domains.

  20. Testing cosmic geometry without dynamic distortions using voids

    SciTech Connect

    Hamaus, Nico; Sutter, P.M.; Lavaux, Guilhem; Wandelt, Benjamin D. E-mail: sutter@iap.fr E-mail: wandelt@iap.fr

    2014-12-01

    We propose a novel technique to probe the expansion history of the Universe based on the clustering statistics of cosmic voids. In particular, we compute their two-point statistics in redshift space on the basis of realistic mock galaxy catalogs and apply the Alcock-Paczynski test. In contrast to galaxies, we find void auto-correlations to be marginally affected by peculiar motions, providing a model-independent measure of cosmological parameters without systematics from redshift-space distortions. Because only galaxy-galaxy and void-galaxy correlations have been considered in these types of studies before, the presented method improves both statistical and systematic uncertainties on the product of angular diameter distance and Hubble rate, furnishing the potentially cleanest probe of cosmic geometry available to date.

  1. Voids as a precision probe of dark energy

    SciTech Connect

    Biswas, Rahul; Alizadeh, Esfandiar; Wandelt, Benjamin D.

    2010-07-15

    The shapes of cosmic voids, as measured in spectroscopic galaxy redshift surveys, constitute a promising new probe of dark energy (DE). We forecast constraints on the DE equation of state and its variation from current and future surveys and find that the promise of void shape measurements compares favorably to that of standard methods such as supernovae and cluster counts even for currently available data. Owing to the complementary nature of the constraints, void shape measurements improve the Dark Energy Task Force figure of merit by 2 orders of magnitude for a future large scale experiment such as EUCLID when combined with other probes of dark energy available on a similar time scale. Modeling several observational and theoretical systematics has only moderate effects on these forecasts. We discuss additional systematics which will require further study using simulations.

  2. Quantifying Void Ratio Variation in Sand using Computed Tomography

    NASA Technical Reports Server (NTRS)

    Alshibli, Khalid A.; Batiste, Susan N.; Swanson, Roy A.; Sture, Stein; Costes, Nicholas C.; Lankton, Mark R.

    1999-01-01

    A series of displacement-controlled, conventional, drained axisymmetric (triaxial) experiments were conducted on dry Ottawa sand specimens at very low effective confining stresses in a microgravity environment aboard the Space Shuttle during the NASA STS-89 mission. Post-flight analysis included studying the internal fabric and failure patterns of these specimens using Computed Tomography (CT). The CT scans of three specimens subjected to different compression levels (uncompressed specimen, a specimen compressed to 3.3% nominal axial strain (epsilon(sub a)), and a specimen compressed to 25% epsilon(sub a)) are presented to investigate the evolution of instability patterns and to quantify void ratio variation. The progress of failure is described and discussed. Also, specimens' densities were calibrated using standard ASTM procedures and void ratio spatial variation was calculated and represented by contour maps and histograms. The CT technique demonstrated good ability to detect specimen inhomogeneities, localization patterns, and quantifying void ratio variation within sand specimens.

  3. Voronoi and void statistics for superhomogeneous point processes.

    PubMed

    Gabrielli, Andrea; Torquato, Salvatore

    2004-10-01

    We study the Voronoi and void statistics of superhomogeneous (or hyperuniform) point patterns in which the infinite-wavelength density fluctuations vanish. Superhomogeneous or hyperuniform point patterns arise in one-component plasmas, primordial density fluctuations in the Universe, and jammed hard-particle packings. We specifically analyze a certain one-dimensional model by studying size fluctuations and correlations of the associated Voronoi cells. We derive exact results for the complete joint statistics of the size of two Voronoi cells. We also provide a sum rule that the correlation matrix for the Voronoi cells must obey in any space dimension. In contrast to the conventional picture of superhomogeneous systems, we show that infinitely large Voronoi cells or voids can exist in superhomogeneous point processes in any dimension. We also present two heuristic conditions to identify and classify any superhomogeneous point process in terms of the asymptotic behavior of the void size distribution. PMID:15600395

  4. Tunnel and Subsurface Void Detection and Range to Target Measurement

    SciTech Connect

    Phillip B. West

    2009-06-01

    Engineers and technicians at the Idaho National Laboratory invented, designed, built and tested a device capable of detecting and measuring the distance to, an underground void, or tunnel. Preliminary tests demonstrated positive detection of, and range to, a void thru as much as 30 meters of top-soil earth. Device uses acoustic driving point impedance principles pioneered by the Laboratory for well-bore physical properties logging. Data receipts recorded by the device indicates constructive-destructive interference patterns characteristic of acoustic wave reflection from a downward step-change in impedance mismatch. Prototype tests demonstrated that interference patterns in receipt waves could depict the patterns indicative of specific distances. A tool with this capability can quickly (in seconds) indicate the presence and depth/distance of a void or tunnel. Using such a device, border security and military personnel can identify threats of intrusion or weapons caches in most all soil conditions including moist and rocky.

  5. Postoperative Submandibular Gland Swelling following Craniotomy under General Anesthesia.

    PubMed

    Nakanishi, Haruka; Tono, Tetsuya; Ibusuki, Shoichiro

    2015-01-01

    Objective. Reporting of a rare case of postoperative submandibular gland swelling following craniotomy. Case Report. A 33-year-old male underwent resection for a brain tumor under general anesthesia. The tumor was resected via a retrosigmoid suboccipital approach and the patient was placed in a lateral position with his face down and turned to the right. Slight swelling of the right submandibular gland was observed just after the surgery. Seven hours after surgery, edematous change around the submandibular gland worsened and he required emergent reintubation due to airway compromise. The cause of submandibular gland swelling seemed to be an obstruction of the salivary duct due to surgical positioning. Conclusion. Once submandibular swelling and edematous change around the submandibular gland occur, they can worsen and compromise the air way within several hours after operation. Adequate precaution must be taken for any predisposing skull-base surgery that requires strong cervical rotation and flexion. PMID:26697254

  6. Postoperative Submandibular Gland Swelling following Craniotomy under General Anesthesia

    PubMed Central

    Nakanishi, Haruka; Tono, Tetsuya; Ibusuki, Shoichiro

    2015-01-01

    Objective. Reporting of a rare case of postoperative submandibular gland swelling following craniotomy. Case Report. A 33-year-old male underwent resection for a brain tumor under general anesthesia. The tumor was resected via a retrosigmoid suboccipital approach and the patient was placed in a lateral position with his face down and turned to the right. Slight swelling of the right submandibular gland was observed just after the surgery. Seven hours after surgery, edematous change around the submandibular gland worsened and he required emergent reintubation due to airway compromise. The cause of submandibular gland swelling seemed to be an obstruction of the salivary duct due to surgical positioning. Conclusion. Once submandibular swelling and edematous change around the submandibular gland occur, they can worsen and compromise the air way within several hours after operation. Adequate precaution must be taken for any predisposing skull-base surgery that requires strong cervical rotation and flexion. PMID:26697254

  7. Apparatus measures swelling of membranes in electrochemical cells

    NASA Technical Reports Server (NTRS)

    Hennigan, T. J.

    1965-01-01

    Apparatus consisting of a pressure plate unit, four springs of known spring constant and a micrometer measures the swelling and force exerted by the polymer membranes of alkaline electrochemical cells.

  8. Fission induced swelling of U-Mo/Al dispersion fuel

    NASA Astrophysics Data System (ADS)

    Kim, Yeon Soo; Jeong, G. Y.; Park, J. M.; Robinson, A. B.

    2015-10-01

    Fission-induced swelling of U-Mo/Al dispersion fuel meat was measured using microscopy images obtained from post-irradiation examination. The data of reduced-size plate-type test samples and rod-type test samples were employed for this work. A model to predict the meat swelling of U-Mo/Al dispersion fuel was developed. This model is composed of several submodels including a model for interaction layer (IL) growth between U-Mo and Al matrix, a model for IL thickness to IL volume conversion, a correlation for the fission-induced swelling of U-Mo alloy particles, a correlation for the fission-induced swelling of IL, and models of U-Mo and Al consumption by IL growth. The model was validated using full-size plate data that were not included in the model development.

  9. Detecting the integrated Sachs-Wolfe effect with stacked voids

    NASA Astrophysics Data System (ADS)

    Ilić, Stéphane; Langer, Mathieu; Douspis, Marian

    2013-08-01

    The stacking of cosmic microwave background (CMB) patches has been recently used to detect the integrated Sachs-Wolfe effect (iSW). When focusing on the locations of superstructures identified in the Sloan Digital Sky Survey (SDSS), Granett et al. (2008a, ApJ, 683, L99, Gr08) found a signal with strong significance and an amplitude reportedly higher than expected within the ΛCDM paradigm. We revisit the analysis using our own robust protocol, and extend the study to the two most recent and largest catalogues of voids publicly available. We quantify and subtract the level of foreground contamination in the stacked images and determine the contribution on the largest angular scales from the first multipoles of the CMB. We obtain the radial temperature and photometry profiles from the stacked images. Using a Monte Carlo approach, we computed the statistical significance of the profiles for each catalogue and identified the angular scale at which the signal-to-noise ratio (S/N) is maximum. We essentially confirm the signal detection reported by Gr08, but for the other two catalogues, a rescaling of the voids to the same size on the stacked image is needed to find any significant signal (with a maximum at ~2.4σ). This procedure reveals that the photometry peaks at unexpectedly large angles in the case of the Gr08 voids, in contrast to voids from other catalogues. Conversely, the photometry profiles derived from the stacked voids of these other catalogues contain small central hot spots of uncertain origin. We also stress the importance of a posteriori selection effects that might arise when intending to increase the S/N, and we discuss the possible impact of void overlap and alignment effects. We argue that the interpretation in terms of an iSW effect of any detected signal via the stacking method is far from obvious.

  10. Voiding trial outcome following pelvic floor repair without incontinence procedures

    PubMed Central

    Wang, Rui; Won, Sara; Haviland, Miriam J.; Bargen, Emily Von; Hacker, Michele R.; Li, Janet

    2016-01-01

    Introduction and hypothesis Our aim was to identify predictors of postoperative voiding trial failure among patients who had a pelvic floor repair without a concurrent incontinence procedure in order to identify low-risk patients in whom postoperative voiding trials may be modified. Methods We conducted a retrospective cohort study of women who underwent pelvic floor repair without concurrent incontinence procedures at two institutions from 1 November 2011 through 13 October 2013 after abstracting demographic and clinical data from medical records. The primary outcome was postoperative retrograde voiding trial failure. We used modified Poisson regression to calculate the risk ratio (RR) and 95 % confidence interval (CI). Results Of the 371 women who met eligibility criteria, 294 (79.2 %) had complete data on the variables of interest. Forty nine (16.7%) failed the trial, and those women were less likely to be white (p = 0.04), more likely to have had an anterior colporrhaphy (p = 0.001), and more likely to have had a preoperative postvoid residual (PVR) ≥150 ml (p = 0.001). After adjusting for race, women were more likely to fail their voiding trial if they had a preoperative PVR of ≥150 ml (RR: 1.9; 95 % CI: 1.1–3.2); institution also was associated with voiding trial failure (RR: 3.0; 95 % CI: 1.6–5.4). Conclusions Among our cohort, postoperative voiding trial failure was associated with a PVR of ≥150 ml and institution at which the surgery was performed. PMID:26886553

  11. Towards understanding the structure of voids in the cosmic web

    NASA Astrophysics Data System (ADS)

    Einasto, J.; Suhhonenko, I.; Hütsi, G.; Saar, E.; Einasto, M.; Liivamägi, L. J.; Müller, V.; Starobinsky, A. A.; Tago, E.; Tempel, E.

    2011-10-01

    Context. According to the modern cosmological paradigm, cosmic voids form in low density regions between filaments of galaxies and superclusters. Aims: Our goal is to see how density waves of different scale combine to form voids between galaxy systems of various scales. Methods: We perform numerical simulations of structure formation in cubes of size 100, and 256 h-1Mpc, with resolutions 2563 and 5123 particles and cells. To understand the role of density perturbations of various scale, we cut power spectra on scales from 8 to 128 h-1Mpc, using otherwise in all cases identical initial random realisations. Results: We find that small haloes and short filaments form all over the simulation box, if perturbations only on scales as large as 8 h-1Mpc are present. We define density waves of scale ≥ 64 h-1Mpc as large, waves of scale ≃ 32 h-1Mpc as medium scale, and waves of scale ≃ 8 h-1Mpc as small scale, within a factor of two. Voids form in regions where medium- and large-scale density perturbations combine in negative parts of the waves because of the synchronisation of phases of medium- and large-scale density perturbations. In voids, the growth of potential haloes (formed in the absence of large-scale perturbations) is suppressed by the combined negative sections of medium- and large-scale density perturbations, so that their densities are less than the mean density, and thus during the evolution their densities do not increase. Conclusions: The phenomenon of large multi-scale voids in the cosmic web requires the presence of an extended spectrum of primordial density perturbations. The void phenomenon is due to the action of two processes: the synchronisation of density perturbations of medium and large scales, and the suppression of galaxy formation in low-density regions by the combined action of negative sections of medium- and large-scale density perturbations.

  12. ONLY THE LONELY: H I IMAGING OF VOID GALAXIES

    SciTech Connect

    Kreckel, K.; Van Gorkom, J. H.; Platen, E.; Van de Weygaert, R.; Van der Hulst, J. M.; Aragon-Calvo, M. A.; Yip, C.-W.; Kovac, K.; Peebles, P. J. E.

    2011-01-15

    Void galaxies, residing within the deepest underdensities of the Cosmic Web, present an ideal population for the study of galaxy formation and evolution in an environment undisturbed by the complex processes modifying galaxies in clusters and groups, as well as provide an observational test for theories of cosmological structure formation. We have completed a pilot survey for the H I imaging aspects of a new Void Galaxy Survey (VGS), imaging 15 void galaxies in H I in local (d < 100 Mpc) voids. H I masses range from 3.5 x 10{sup 8} to 3.8 x 10{sup 9} M{sub sun}, with one nondetection with an upper limit of 2.1 x 10{sup 8} M{sub sun}. Our galaxies were selected using a structural and geometric technique to produce a sample that is purely environmentally selected and uniformly represents the void galaxy population. In addition, we use a powerful new backend of the Westerbork Synthesis Radio Telescope that allows us to probe a large volume around each targeted galaxy, simultaneously providing an environmentally constrained sample of fore- and background control samples of galaxies while still resolving individual galaxy kinematics and detecting faint companions in H I. This small sample makes up a surprisingly interesting collection of perturbed and interacting galaxies, all with small stellar disks. Four galaxies have significantly perturbed H I disks, five have previously unidentified companions at distances ranging from 50 to 200 kpc, two are in interacting systems, and one was found to have a polar H I disk. Our initial findings suggest void galaxies are a gas-rich, dynamic population which present evidence of ongoing gas accretion, major and minor interactions, and filamentary alignment despite the surrounding underdense environment.

  13. Molecular accessibility in solvent swelled coal. Quarterly report, November 1991

    SciTech Connect

    Kispert, L.D.

    1991-12-31

    The EPR-spin probe method was used to study the swelling of covalently cross-linked 2%, 4%, 6%, 8% and 12% polystyrene-divinyl benzene copolymers, used as models of APCS coal structural elements. The results were compared with swelling studies on APCS coals and confirmed results showing that coal was polymeric, that it had covalent cross-links increasing with rank, that it was structurally anisotropic, and that its swelling was anisotropic. The low temperature swelling of Argonne Premium Coal Samples using solvents of varying polarity was investigated. The variation in the shape of the pore was followed as a function of temperature and swelling solvent polarity. This change in pore structure was attributed to break-up of the hydrogen bonding network in coal by polar solvents. The modification in pore shape from spherical to cylindrical was attributed to anisotropy in hydrogen bond densities. The structural changes in coal pores that occur when APCS coal is dehydrated prior to swelling with polar solvents has been determined. These changes are different from those that occur in the absence of prior dehydration. Most impressive is the huge change that occurs in lignite coal (Beulah-Zap). It appears that this coal has collapsed upon dehydration preventing any spin probe from being trapped in the dehydrated lignite upon swelling. Various sized probes have been studied. A study on the variation in the hydrogen bonding character of the pore wall as the coals are swelled with various polar solvents has also been completed. A statistical analysis of the data has been completed to determine important trends in the data. 9 refs.

  14. Interaction of voids and nanoductility in silica glass.

    PubMed

    Chen, Yi-Chun; Lu, Zhen; Nomura, Ken-Ichi; Wang, Weiqiang; Kalia, Rajiv K; Nakano, Aiichiro; Vashishta, Priya

    2007-10-12

    Multimillion-to-billion-atom molecular dynamics simulations are performed to investigate the interaction of voids in silica glass under hydrostatic tension. Nanometer size cavities nucleate in intervoid ligaments as a result of the expansion of Si-O rings due to a bond-switching mechanism, which involves bond breaking between Si-O and bond formation between that Si and a nonbridging O. With further increase in strain, nanocracks form on void surfaces and ligaments fracture through the growth and coalescence of ligament nanocavities in a manner similar to that observed in ductile metallic alloys. PMID:17995183

  15. Dimensionality effects in void-induced explosive sensitivity

    DOE PAGESBeta

    Herring, Stuart Davis; Germann, Timothy Clark; Gronbech-Jensen, Niels

    2016-07-06

    Here, the dimensionality of defects in high explosives controls their heat generation and the expansion of deflagrations from them. We compare the behaviour of spherical voids in three dimensions to that of circular voids in two dimensions. The behaviour is qualitatively similar, but the additional focusing along the extra transverse dimension significantly reduces the piston velocity needed to initiate reactions. However, the reactions do not grow as well in three dimensions, so detonations require larger piston velocities. Pressure exponents are seen to be similar to those for the two-dimensional system.

  16. Competition between adsorption-induced swelling and elastic compression of coal at CO2 pressures up to 100 MPa

    NASA Astrophysics Data System (ADS)

    Hol, Sander; Spiers, Christopher J.

    2012-11-01

    coal swelling, which expresses the net volumetric strain as the sum of the adsorption-induced swelling strain and the elastic compression with the adsorption-induced swelling being taken as linearly related to adsorbed CO2 concentration. A comparison of experimentally determined adsorption-induced swelling strain with the adsorbed concentration of CO2 (data Gensterblum et al., 2010) confirms the assumed linear dependence. We go on to compare our experimentally determined adsorption-induced swelling strains to those calculated from an adsorbed concentration model. Good agreement was found over the full range of CO2 pressures up to 100 MPa. This shows that combining this thermodynamically based model for adsorbed concentration with the elastic compression of our samples, obtained from their bulk modulus, provides a good description of the measured volumetric behaviour of our samples, and suggests that the physical basis for the model is also valid. The implications of our results for ECBM operations are that compliant coals (low K), which exhibit little adsorption-induced swelling (hence low dependence C), will show relatively small reductions or even increases in permeability due to competition between swelling and compression when CO2 pressure increases during ECBM operations. These coals will tend to be more suitable for ECBM operations. Coals exhibiting high stiffness (K) and high adsorption capacity are less suitable for ECBM.

  17. Swelling of four glove materials challenged by six metalworking fluids.

    PubMed

    Xu, Wenhai; Que Hee, Shane S

    2008-01-01

    The performance of protective gloves against metalworking fluids (MWFs) has rarely been studied because of the difficult chemical analysis associated with complex MWFs. In the present study, glove swelling was used as a screening parameter of glove compatibility after challenge of the outer surfaces of chloroprene, latex, nitrile, and vinyl disposable gloves by six MWF concentrates for 2 hours in an ASTM F-739-type permeation cell without collection medium. Swelling relative to original thickness was up to 39% for latex, 7.6% for chloroprene, and 3.5% for nitrile. Shrinking up to 9.3% occurred for vinyl. Chloroprene and latex did not swell significantly for the semisynthetic and synthetic MWFs. Vinyl, previously not tested, was a good candidate for MWFs other than the soluble oil type. Although nitrile was recommended by the National Institute for the Occupational Safety and Health (NIOSH) for all types of MWFs, its swelling after 2-hour challenge was significant with Student t-tests for the soluble oil, synthetic, and semisynthetic MWFs. Glove swelling can be used as a screening chemical degradation method for mixtures such as MWFs with difficult chemical analysis. Further studies need to be conducted on the relationship between permeation and glove swelling.

  18. Microchannel deformations due to solvent-induced PDMS swelling.

    PubMed

    Dangla, Rémi; Gallaire, François; Baroud, Charles N

    2010-11-01

    The compatibility of polydimethylsiloxane (PDMS) channels with certain solvents is a well known problem of soft lithography techniques, in particular when it leads to the swelling of the PDMS blocks. However, little is known about the modification of microchannel geometries when they are subjected to swelling solvents. Here, we experimentally measure the deformations of the roof of PDMS microchannels due to such solvents. The dynamics of impregnation of the solvents in PDMS and its relation to volume dilation are first addressed in a model experiment, allowing the precise measurement of the diffusion coefficients of oils in PDMS. When Hexadecane, a swelling solvent, fills a microchannel 1 mm in width and 50 μm in height, we measure that the channel roof bends inwards and takes a parabolic shape with a maximum deformation of 7 μm. The amplitude of the subsidence is found to increase with the channel width, reaching 28 μm for a 2 mm wide test section. On the other hand, perfluorinated oils do not swell the PDMS and the microchannel geometry is not affected by the presence of perfluorodecalin. Finally, we observe that the trajectories of droplets flowing in this microchannel are strongly affected by the deformations: drops carried by swelling oils are pushed towards the edges of the channel while those carried by non-swelling oils remain in the channel center. PMID:20848011

  19. Swelling of four glove materials challenged by six metalworking fluids.

    PubMed

    Xu, Wenhai; Que Hee, Shane S

    2008-01-01

    The performance of protective gloves against metalworking fluids (MWFs) has rarely been studied because of the difficult chemical analysis associated with complex MWFs. In the present study, glove swelling was used as a screening parameter of glove compatibility after challenge of the outer surfaces of chloroprene, latex, nitrile, and vinyl disposable gloves by six MWF concentrates for 2 hours in an ASTM F-739-type permeation cell without collection medium. Swelling relative to original thickness was up to 39% for latex, 7.6% for chloroprene, and 3.5% for nitrile. Shrinking up to 9.3% occurred for vinyl. Chloroprene and latex did not swell significantly for the semisynthetic and synthetic MWFs. Vinyl, previously not tested, was a good candidate for MWFs other than the soluble oil type. Although nitrile was recommended by the National Institute for the Occupational Safety and Health (NIOSH) for all types of MWFs, its swelling after 2-hour challenge was significant with Student t-tests for the soluble oil, synthetic, and semisynthetic MWFs. Glove swelling can be used as a screening chemical degradation method for mixtures such as MWFs with difficult chemical analysis. Further studies need to be conducted on the relationship between permeation and glove swelling. PMID:17680173

  20. In situ nanomechanical characterization of the early stages of swelling and degradation of a biodegradable polymer

    NASA Astrophysics Data System (ADS)

    Dumitru, A. C.; Espinosa, F. M.; Garcia, R.; Foschi, G.; Tortorella, S.; Valle, F.; Dallavalle, M.; Zerbetto, F.; Biscarini, F.

    2015-03-01

    The interactions of a biodegradable scaffold with cells or living tissues depend on the time-evolution of the nanoscale properties of the scaffold. We present an in situ quantitative study on the early-stage swelling and degradation of poly(lactic-co-glycolic acid) (PLGA). A novel metrology scheme based on force microscopy measurements of the patterns of PLGA nanostructures is developed to characterize the evolution of topography, volume and nanomechanical properties. The volume and nanoscale roughness show an oscillating behaviour during the first eight days of immersion; at a later stage, we observe a continuous decrease of the volume. The effective Young's modulus exhibits a monotonic decrease from an initial value of about 2.4 GPa down to 9 MPa at day 14. The oscillating behaviour of the volume before the onset of full degradation is explained by a coupled diffusion-swelling mechanism. The appearance of a second maximum in the volume evolution results from the competition between swelling and degradation.The interactions of a biodegradable scaffold with cells or living tissues depend on the time-evolution of the nanoscale properties of the scaffold. We present an in situ quantitative study on the early-stage swelling and degradation of poly(lactic-co-glycolic acid) (PLGA). A novel metrology scheme based on force microscopy measurements of the patterns of PLGA nanostructures is developed to characterize the evolution of topography, volume and nanomechanical properties. The volume and nanoscale roughness show an oscillating behaviour during the first eight days of immersion; at a later stage, we observe a continuous decrease of the volume. The effective Young's modulus exhibits a monotonic decrease from an initial value of about 2.4 GPa down to 9 MPa at day 14. The oscillating behaviour of the volume before the onset of full degradation is explained by a coupled diffusion-swelling mechanism. The appearance of a second maximum in the volume evolution results from

  1. A transverse isotropic model for microporous solids: Application to coal matrix adsorption and swelling

    NASA Astrophysics Data System (ADS)

    Espinoza, D. N.; Vandamme, M.; Dangla, P.; Pereira, J.-M.; Vidal-Gilbert, S.

    2013-12-01

    Understanding the adsorption-induced swelling in coal is critical for predictable and enhanced coal bed methane production. The coal matrix is a natural anisotropic disordered microporous solid. We develop an elastic transverse isotropic poromechanical model for microporous solids which couples adsorption and strain through adsorption stress functions and expresses the adsorption isotherm as a multivariate function depending on fluid pressure and solid strains. Experimental data from the literature help invert the anisotropic adsorptive-mechanical properties of Brzeszcze coal samples exposed to CO2. The main findings include the following: (1) adsorption-induced swelling can be modeled by including fluid-specific and pressure-dependent adsorption stress functions into equilibrium equations, (2) modeling results suggest that swelling anisotropy is mostly caused by anisotropy of the solid mechanical properties, and (3) the total amount of adsorbed gas measured by immersing coal in the adsorbate overestimates adsorption amount compared to in situ conditions up to ˜20%. The developed fully coupled model can be upscaled to determine the coal seam permeability through permeability-stress relationships.

  2. Visual Diagnosis: An Adolescent Male With Severe Facial Swelling and Scalp Infection.

    PubMed

    Riney, Lauren C; Shah, Meera; Lopez Domowicz, Denise A

    2015-11-01

    Scalp eruptions are common in infants, children, and adolescents and the etiology can be broad. Allergic contact dermatitis can result after multiple non eventful uses of a hair care product, including shampoo, relaxers, and coloring agents. Symptoms of allergic contact dermatitis include intense pruritus with weeping, pain, and stinging sensations. Signs on physical examination include swelling with scaly erythematous plaques as well as bullae with vesicles and pustules in severe cases. The forehead, eyelids, and postauricular areas also are subject to swelling. Definitive diagnosis of allergic dermatitis involves patch testing to determine the specific allergen. Education about avoidance of the allergen and recommendations for allergen-free products are the most important aspects of managing patients with allergic contact dermatitis. Treatment depends on the severity and extent of involvement. First-line treatment is topical corticosteroids, followed by topical calcineurin inhibitors. For more extensive dermatitis, systemic corticosteroids are beneficial. PMID:26527634

  3. Features of rubber swelling in transformer oil, according to NMR data

    NASA Astrophysics Data System (ADS)

    Bavin, R. R.; Fursov, D. I.; Vasil'ev, S. G.; Tarasov, V. P.; Zabrodin, V. A.; Volkov, V. I.

    2016-08-01

    NMR spectroscopy, NMR relaxation, and NMR with a pulsed magnetic field gradient methods are used to study the swelling of the elastomers based on ethylene-propylene rubber, butadiene-nitrile rubber, and fluororubber SKF-26 in transformer oil. Components corresponding to the fractions of oil and polymer network are identified. It is shown that the affinity of the polymers toward transformer oil displays an increase in the orderly sequence of ethylene-propylene rubber, fluororubber, and butadiene-nitrile rubber; the stability of the polymers towards carbon tetrachloride falls in the same sequence. Based on an analysis of the spin-spin relaxation time depending on the degree of swelling, it is found that fluororubber elastomers are characterized by the formation of a polymer network that prevents further sorption, In contrast, elastomer based on ethylene-propylene rubber gives no indication of the formation of a rigid polymer network.

  4. Model for incorporating fuel swelling and clad shrinkage effects in diffusion theory calculations (LWBR Development Program)

    SciTech Connect

    Schick, W.C. Jr.; Milani, S.; Duncombe, E.

    1980-03-01

    A model has been devised for incorporating into the thermal feedback procedure of the PDQ few-group diffusion theory computer program the explicit calculation of depletion and temperature dependent fuel-rod shrinkage and swelling at each mesh point. The model determines the effect on reactivity of the change in hydrogen concentration caused by the variation in coolant channel area as the rods contract and expand. The calculation of fuel temperature, and hence of Doppler-broadened cross sections, is improved by correcting the heat transfer coefficient of the fuel-clad gap for the effects of clad creep, fuel densification and swelling, and release of fission-product gases into the gap. An approximate calculation of clad stress is also included in the model.

  5. Swelling or erosion on the surface of patterned GaN damaged by heavy ion implantation

    SciTech Connect

    Gao, Yuan; Lan, Chune; Xue, Jianming; Yan, Sha; Wang, Yugang; Xu, Fujun; Shen, Bo; Zhang, Yanwen

    2010-06-08

    Wurtzite undoped GaN epilayers (0 0 0 1) was implanted with 500 keV Au+ ions at room temperature under different doses, respectively. Ion implantation was performed through photoresist masks on GaN to produce alternating strips. The experimental results showed that the step height of swelling and decomposition in implanted GaN depended on ion dose and annealing temperature, i.e., damage level and its evolution. This damage evolution is contributed to implantation-induced defect production, and defect migration/accumulation occurred at different levels of displacement per atom. The results suggest that the swelling is due to the formation of porous structures in the amorphous region of implanted GaN. The decomposition of implanted area can be attributed to the disorder saturation and the diffusion of surface amorphous layer.

  6. Influence of suction cycles on the soil fabric of compacted swelling soil

    NASA Astrophysics Data System (ADS)

    Nowamooz, Hossein; Masrouri, Farimah

    2010-12-01

    The soil fabric plays an important role in complex hydromechanical behaviour of the expansive soils. This article addresses the influence of the wetting and drying paths on the soil fabric of compacted bentonite and silt mixtures at two different initial dry densities corresponding to loose and dense states. To obtain the hydric response of the soil, two suction imposition techniques were used: osmotic technique for the suction range less than 8.5 MPa and the vapour equilibrium or the salt solution technique for the suction range between 8.5 and 287.9 MPa. Additionally, the soil fabric analysis was performed using mercury intrusion porosimetry (MIP) and nitrogen gas adsorption (BET) techniques. The dense samples produced cumulative swelling strains during the suction cycles, while shrinkage was observed for the loose samples. The suction cycles induced an equilibrium state indicative of the elastic behaviour of the samples. The soil fabric analysis showed that regardless of the soil's initial state (loose or dense), the samples obtained the same soil fabric at the equilibrium state. The experimental results illustrated also the existence of an elastic void ratio ( e0el) where the compacted soils at this state present an elastic hydric behaviour during the successive suction cycles.

  7. Studies of selected voids. Surface photometry of faint galaxies in the direction of 1600+18 in Hercules void.

    NASA Astrophysics Data System (ADS)

    Petrov, Georgi

    Surface photometry, coordinates, magnitudes m(B), diameters, position angles and some morphological parameters are presented for ca. 1850 faint galaxies in a field of one square degree centered at 1600+18 (1950) (Hercules void). The distribution of the magnitudes of the galaxies in this direction is compared with ''Log Normal'' and ''Gauss'' ones and with similar results from SDDS studies of galaxies. Some candidates for primeval galaxies -- 38 large Low surface brightness galaxies were detected in the direction of the void. Major axes luminosity profiles are analyzed. Comparison between two different methods for automatic selection and classification -- a new package, based on MIDAS INVENTORY and SExtractor packages have been made.

  8. [Reduction of postoperative swelling. Objective measurement of swelling of the upper ankle joint in treatment with serrapeptase-- a prospective study].

    PubMed

    Esch, P M; Gerngross, H; Fabian, A

    1989-02-10

    Using a quantitative standardized procedure, the swelling of the ankle produced by supination trauma was measured. In the 66 patients with fresh rupture of the lateral ligament treated surgically at our Department between December 1986 and April 1987, a prospective study of the effect of serrapeptase (Aniflazym) on post-operative swelling and pain was carried out in 3 randomized groups of patients. In the group receiving the test substance, the swelling had decreased by 50% on the third post-operative day, while in the other two control groups (elevation of the leg, bed rest, with and without the application of ice) no reduction in swelling had occurred at that time. The difference is statistically significant (p = 0.013). Decreasing pain correlated for the most part with the reduction in swelling. Thus, the patients receiving the test substance more rapidly became pain-free than did the control groups. On the basis of these results, serrapeptase would appear to be an effective preparation for the post-operative reduction of swelling, in comparison with the classical conservative measures, for example, the application of ice.

  9. Entropic trapping of macromolecules by mesoscopic periodic voids in a polymer hydrogel.

    PubMed

    Liu, L; Li, P; Asher, S A

    1999-01-14

    The separation of macromolecules such as polymers and DNA by means of electrophoresis, gel permeation chromatography or filtration exploits size-dependent differences in the time it takes for the molecules to migrate through a random porous network. Transport through the gel matrices, which usually consist of full swollen crosslinked polymers, depends on the relative size of the macromolecule compared with the pore radius. Sufficiently small molecules are thought to adopt an approximately spherical conformation when diffusing through the gel matrix, whereas larger ones are forced to migrate in a snake-like fashion. Molecules of intermediate size, however, can get temporarily trapped in the largest pores of the matrix, where the molecule can extend and thus maximize its conformational entropy. This 'entropic trapping' is thought to increase the dependence of diffusion rate on molecular size. Here we report the direct experimental verification of this phenomenon. Bragg diffraction from a hydrogel containing a periodic array of monodisperse water voids confirms that polymers of different weights partition between the hydrogel matrix and the water voids according to the predictions of the entropic trapping theory. Our approach might also lead to the design of improved separation media based on entropic trapping.

  10. Compensation for air voids in photoacoustic computed tomography image reconstruction

    NASA Astrophysics Data System (ADS)

    Matthews, Thomas P.; Li, Lei; Wang, Lihong V.; Anastasio, Mark A.

    2016-03-01

    Most image reconstruction methods in photoacoustic computed tomography (PACT) assume that the acoustic properties of the object and the surrounding medium are homogeneous. This can lead to strong artifacts in the reconstructed images when there are significant variations in sound speed or density. Air voids represent a particular challenge due to the severity of the differences between the acoustic properties of air and water. In whole-body small animal imaging, the presence of air voids in the lungs, stomach, and gastrointestinal system can limit image quality over large regions of the object. Iterative reconstruction methods based on the photoacoustic wave equation can account for these acoustic variations, leading to improved resolution, improved contrast, and a reduction in the number of imaging artifacts. However, the strong acoustic heterogeneities can lead to instability or errors in the numerical wave solver. Here, the impact of air voids on PACT image reconstruction is investigated, and procedures for their compensation are proposed. The contributions of sound speed and density variations to the numerical stability of the wave solver are considered, and a novel approach for mitigating the impact of air voids while reducing the computational burden of image reconstruction is identified. These results are verified by application to an experimental phantom.

  11. Answers from the Void: VIDE and its Applications

    NASA Astrophysics Data System (ADS)

    Sutter, P. M.; Hamaus, N.; Pisani, A.; Lavaux, G.; Wandelt, B. D.

    2016-10-01

    We discuss various applications ofvide, the Void IDentification and Examination toolkit, anopen-source Python/C++ code for finding cosmic voids in galaxy redshift surveysand $N$-body simulations.Based on a substantially enhanced version of ZOBOV, vide not only finds voids, but alsosummarizes their properties, extracts statisticalinformation, and providesa Python-based platform for more detailed analysis, such asmanipulating void catalogs and particle members, filtering, plotting,computing clustering statistics, stacking, comparing catalogs, andfitting density profiles.vide also provides significant additional functionality forpre-processing inputs: for example, vide can work with volume- ormagnitude-limited galaxy samples with arbitrary survey geometries,or darkmatter particles or halo catalogs in a variety of common formats.It can also randomly subsample inputsand includes a Halo Occupation Distribution model forconstructing mock galaxy populations.vide has been used for a wide variety of applications, fromdiscovering a universal density profile to estimatingprimordial magnetic fields, andis publicly available athttp://bitbucket.org/cosmicvoids/vide\\_publicandhttp://www.cosmicvoids.net.

  12. Voids in Jovian magnetosphere revisited - Evidence of spacecraft charging

    NASA Technical Reports Server (NTRS)

    Khurana, K. K.; Kivelson, M. G.; Walker, R. J.; Armstrong, T. P.

    1987-01-01

    The Voyager 2 Plasma Science Instrument (PLS) measuring cold plasma number density observed about a dozen 'voids', lasting from a few minutes to 20 min, in the vicinity of the Ganymede-orbit crossing, when the low-energy ion and electron fluxes recorded fell to very low levels. Original interpretations associated these 'voids' with Ganymede wake effects. In the present study, the PLS data are reexamined, in conjunction with data from the magnetic field experiment and the low-energy charged particle (LECP) experiment. The LECP data showed that the PLS voids were accompanied by large enhancements of the flux of energetic electrons and ions, while the magnetic data exhibited no systematic signatures. It is suggested that increased energetic electron fluxes in the void regions intermittently charged the spacecraft negatively to values between a few kV and a few tens of kV, and that spacecraft charging could have produce dropouts in the measured cold ion and electron fluxes and enhancements in the measured fluxes of hot particles consistent with the observations.

  13. POLAR DISK GALAXY FOUND IN WALL BETWEEN VOIDS

    SciTech Connect

    Stanonik, K.; Van Gorkom, J. H.; Platen, E.; Van de Weygaert, R.; Van der Hulst, J. M.; Aragon-Calvo, M. A.; Peebles, P. J. E.

    2009-05-01

    We have found an isolated polar disk galaxy in what appears to be a cosmological wall situated between two voids. This void galaxy is unique as its polar disk was discovered serendipitously in an H I survey of SDSS void galaxies, with no optical counterpart to the H I polar disk. Yet the H I mass in the disk is comparable to the stellar mass in the galaxy. This suggests slow accretion of the H I material at a relatively recent time. There is also a hint of a warp in the outer parts of the H I disk. The central, stellar disk appears relatively blue, with faint near-UV emission, and is oriented (roughly) parallel to the surrounding wall, implying gas accretion from the voids. The considerable gas mass and apparent lack of stars in the polar disk, coupled with the general underdensity of the environment, supports recent theories of cold flow accretion as an alternate formation mechanism for polar disk galaxies.

  14. The Effect of Random Voids in the Modified Gurson Model

    NASA Astrophysics Data System (ADS)

    Fei, Huiyang; Yazzie, Kyle; Chawla, Nikhilesh; Jiang, Hanqing

    2012-02-01

    The porous plasticity model (usually referred to as the Gurson-Tvergaard-Needleman model or modified Gurson model) has been widely used in the study of microvoid-induced ductile fracture. In this paper, we studied the effects of random voids on the porous plasticity model. Finite-element simulations were conducted to study a copper/tin/copper joint bar under uniaxial tension using the commercial finite-element package ABAQUS. A randomly distributed initial void volume fraction with different types of distribution was introduced, and the effects of this randomness on the crack path and macroscopic stress-strain behavior were studied. It was found that consideration of the random voids is able to capture more detailed and localized deformation features, such as different crack paths and different ultimate tensile strengths, and meanwhile does not change the macroscopic stress-strain behavior. It seems that the random voids are able to qualitatively explain the scattered observations in experiments while keeping the macroscopic measurements consistent.

  15. Liquid crystals detect voids in fiber glass laminates

    NASA Technical Reports Server (NTRS)

    Hollar, W. T.

    1967-01-01

    Liquid crystal solution nondestructively detects voids or poor bond lines in fiber glass laminates. A thin coating of the solution is applied by spray or brush to the test article surface, and when heated indicates the exact location of defects by differences in color.

  16. Molecular Gas and Star Formation in Void Galaxies

    NASA Astrophysics Data System (ADS)

    Das, M.; Saito, T.; Iono, D.; Honey, M.; Ramya, S.

    2016-10-01

    We present the detection of molecular gas using CO(1-0) line emission and followup Hα imaging observations of galaxies located in nearby voids. The CO(1-0) observations were done using the 45m telescope of the Nobeyama Radio Observatory (NRO) and the optical observations were done using the Himalayan Chandra Telescope (HCT). Although void galaxies lie in the most underdense parts of our universe, a significant fraction of them are gas rich, spiral galaxies that show signatures of ongoing star formation. Not much is known about their cold gas content or star formation properties. In this study we searched for molecular gas in five void galaxies using the NRO. The galaxies were selected based on their relatively higher IRAS fluxes or Hα line luminosities. CO(1-0) emission was detected in four galaxies and the derived molecular gas masses lie between (1 - 8)×109 M⊙. The Hα imaging observations of three galaxies detected in CO emission indicates ongoing star formation and the derived star formation rates vary between from 0.2 - 1.0 M7odot; yr -1, which is similar to that observed in local galaxies. Our study shows that although void galaxies reside in underdense regions, their disks may contain molecular gas and have star formation rates similar to galaxies in denser environments.

  17. Kinetic Monte Carlo simulations of void lattice formation during irradiation

    NASA Astrophysics Data System (ADS)

    Heinisch, H. L.; Singh, B. N.

    2003-11-01

    Over the last decade, molecular dynamics simulations of displacement cascades have revealed that glissile clusters of self-interstitial crowdions are formed directly in cascades and that they migrate one-dimensionally along close-packed directions with extremely low activation energies. Occasionally, under various conditions, a crowdion cluster can change its Burgers vector and glide along a different close-packed direction. The recently developed production bias model (PBM) of microstructure evolution under irradiation has been structured specifically to take into account the unique properties of the vacancy and interstitial clusters produced in the cascades. Atomic-scale kinetic Monte Carlo (KMC) simulations have played a useful role in understanding the defect reaction kinetics of one-dimensionally migrating crowdion clusters as a function of the frequency of direction changes. This has made it possible to incorporate the migration properties of crowdion clusters and changes in reaction kinetics into the PBM. In the present paper we utilize similar KMC simulations to investigate the significant role that crowdion clusters can play in the formation and stability of void lattices. The creation of stable void lattices, starting from a random distribution of voids, is simulated by a KMC model in which vacancies migrate three-dimensionally and self-interstitial atom (SIA) clusters migrate one-dimensionally, interrupted by directional changes. The necessity of both one-dimensional migration and Burgers vectors changes of SIA clusters for the production of stable void lattices is demonstrated, and the effects of the frequency of Burgers vector changes are described.

  18. Swelling of root cell walls as an indicator of their functional state.

    PubMed

    Meychik, N R; Yermakov, I P

    2001-02-01

    The swelling capacity of cell walls isolated from different parts of lupine root was investigated. The water content in fragments of intact roots (Q) and swelling coefficient of standardized samples of cell walls (Kcw) were determined, and the dependences of Q and Kcw on the distance from the root tip (L) were plotted. It was shown that the change in Q value along the stretch of the lupine root reaches its maximum at distances of 1.5-6 cm or 7-12 cm from the root tip in 7-day-old and 14-day-old seedlings, respectively, whereas the Kcw value distribution over the root length is virtually invariable. In the radial direction, both the Q and Kcw values in cortex tissues are about twice higher than in the central cylinder. In our opinion, the changes of both Q and Kcw in the radial direction are associated with different degrees of cross-linking between polymer chains in cell wall structures of root cortex and central cylinder. The results of measurement of the Kcw value are consistent with the widely accepted mechanisms of water transport in roots in the radial direction. These data show that water transport through apoplast to the border between the cortex and central cylinder is accompanied by an increase in the resistance to water flow. Among other factors, this increase is due to a greater degree of cross-linking between cell wall polymers in the central cylinder. The results of measurement of the swelling coefficient of standardized cell wall samples in water and in 10 mM KCl at different pH values show that the swelling capacity of root cell walls varies according to the physicochemical properties of synthetic ion exchangers. Cell walls shrink (cell wall volume decreases) as ion concentration in solution increases and pH decreases. This causes an increase in the hydraulic resistance (or a decrease in the hydraulic conductivity) of apoplast. It was concluded that swelling is determined by the physicochemical properties of the cell wall, whereas the change in the

  19. Constraints on Cosmology and Gravity from the Dynamics of Voids.

    PubMed

    Hamaus, Nico; Pisani, Alice; Sutter, P M; Lavaux, Guilhem; Escoffier, Stéphanie; Wandelt, Benjamin D; Weller, Jochen

    2016-08-26

    The Universe is mostly composed of large and relatively empty domains known as cosmic voids, whereas its matter content is predominantly distributed along their boundaries. The remaining material inside them, either dark or luminous matter, is attracted to these boundaries and causes voids to expand faster and to grow emptier over time. Using the distribution of galaxies centered on voids identified in the Sloan Digital Sky Survey and adopting minimal assumptions on the statistical motion of these galaxies, we constrain the average matter content Ω_{m}=0.281±0.031 in the Universe today, as well as the linear growth rate of structure f/b=0.417±0.089 at median redshift z[over ¯]=0.57, where b is the galaxy bias (68% C.L.). These values originate from a percent-level measurement of the anisotropic distortion in the void-galaxy cross-correlation function, ϵ=1.003±0.012, and are robust to consistency tests with bootstraps of the data and simulated mock catalogs within an additional systematic uncertainty of half that size. They surpass (and are complementary to) existing constraints by unlocking cosmological information on smaller scales through an accurate model of nonlinear clustering and dynamics in void environments. As such, our analysis furnishes a powerful probe of deviations from Einstein's general relativity in the low-density regime which has largely remained untested so far. We find no evidence for such deviations in the data at hand. PMID:27610841

  20. Constraints on Cosmology and Gravity from the Dynamics of Voids.

    PubMed

    Hamaus, Nico; Pisani, Alice; Sutter, P M; Lavaux, Guilhem; Escoffier, Stéphanie; Wandelt, Benjamin D; Weller, Jochen

    2016-08-26

    The Universe is mostly composed of large and relatively empty domains known as cosmic voids, whereas its matter content is predominantly distributed along their boundaries. The remaining material inside them, either dark or luminous matter, is attracted to these boundaries and causes voids to expand faster and to grow emptier over time. Using the distribution of galaxies centered on voids identified in the Sloan Digital Sky Survey and adopting minimal assumptions on the statistical motion of these galaxies, we constrain the average matter content Ω_{m}=0.281±0.031 in the Universe today, as well as the linear growth rate of structure f/b=0.417±0.089 at median redshift z[over ¯]=0.57, where b is the galaxy bias (68% C.L.). These values originate from a percent-level measurement of the anisotropic distortion in the void-galaxy cross-correlation function, ϵ=1.003±0.012, and are robust to consistency tests with bootstraps of the data and simulated mock catalogs within an additional systematic uncertainty of half that size. They surpass (and are complementary to) existing constraints by unlocking cosmological information on smaller scales through an accurate model of nonlinear clustering and dynamics in void environments. As such, our analysis furnishes a powerful probe of deviations from Einstein's general relativity in the low-density regime which has largely remained untested so far. We find no evidence for such deviations in the data at hand.

  1. A constitutive model for elastoplastic solids containing primary and secondary voids

    NASA Astrophysics Data System (ADS)

    Fabrègue, D.; Pardoen, T.

    In many ductile metallic alloys, the damage process controlled by the growth and coalescence of primary voids nucleated on particles with a size varying typically between 1 and 100 μm, is affected by the growth of much smaller secondary voids nucleated on inclusions with a size varying typically between 0.1 and 3 μm. The goal of this work is first to quantify the potential effect of the growth of these secondary voids on the coalescence of primary voids using finite element (FE) unit cell calculations and second to formulate a new constitutive model incorporating this effect. The nucleation and growth of secondary voids do essentially not affect the growth of the primary voids but mainly accelerate the void coalescence process. The drop of the ductility caused by the presence of secondary voids increases if the nucleation strain decreases and/or if their volume fraction increases and/or if the primary voids are flat. A strong coupling is indeed observed between the shape of the primary voids and the growth of the second population enhancing the anisotropy of the ductility induced by void shape effects. The new micromechanics-based coalescence condition for internal necking introduces the softening induced by secondary voids growing in the ligament between two primary voids. The FE cell calculations were used to guide and assess the development of this model. The use of the coalescence condition relies on a closed-form model for estimating the evolution of the secondary voids in the vicinity of a primary cavity. This coalescence criterion is connected to an extended Gurson model for the first population including the effect of the void aspect ratio. With respect to classical models for single void population, this new constitutive model improves the predictive potential of damage constitutive models devoted to ductile metal while requiring only two new parameters, i.e. the initial porosity of second population and a void nucleation stress, without any additional

  2. Molecular accessibility in solvent swelled coals. Final report

    SciTech Connect

    Kispert, L.D.

    1994-04-01

    The conversion of coal by an economically feasible catalytic method requires the catalyst to diffuse into the coal sample so that hydrogenation catalysis can occur from within as well as the normal surface catalysis. Thus an estimate of the size, shape, and reactivity, of the pores in the coal before and after the swelling with different solvents is needed so that an optimum sized catalyst will be used. This study characterizes the accessible area found in Argonne Premium Coal Samples (APCS) using a EPR spin probe technique. The properties deduced in this manner correlate well with the findings deduced from SANS, NMR, SEM, SAXS and light scattering measurements. The use of nitroxide spin probes with swelling solvents is a simple way in which to gain an understanding of the pore structure of coals, how it changes in the presence of swelling solvents and the chemistry that occurs at the pore wall. Hydrogen bonding sites occur primarily in low-rank coals and vary in reactive strength as rank is varied. Unswelled coals contain small, spherical pores which disappear when coal is swelled in the presence of polar solvents. Swelling studies of polystyrene-divinyl benzene copolymers implied that coal is polymeric, contains significant quantities of covalent cross-links and the covalent cross-link density increases with rank.

  3. In Situ Void Fraction and Gas Volume in Hanford Tank 241-SY-101 as Measured with the Void Fraction Instrument

    SciTech Connect

    CW Stewart; G Chen; JM Alzheimer; PA Meyer

    1998-11-10

    The void fraction instrument (WI) was deployed in Tank 241-SY-101 three times in 1998 to confm and locate the retained gas (void) postulated to be causing the accelerating waste level rise observed since 1995. The design, operation, and data reduction model of the WI are described along with validation testing and potential sources of uncertainty. The test plans, field observations and void measurements are described in detail, including the total gas volume calculations and the gas volume model. Based on 1998 data, the void fraction averaged 0.013 i 0.001 in the mixed slurry and 0.30 ~ 0.04 in the crust. This gives gas volumes (at standard pressure and temperature) of 87 t 9 scm in the slurry and 138 ~ 22 scm in the crust for a total retained gas volume of221 *25 scm. This represents an increase of about 74 scm in the crust and a decrease of about 34 scm in the slurry from 1994/95 results. The overall conclusion is that the gas retention is occurring mainly in the crust layer and there is very little gas in the mixed slurry and loosely settled layers below. New insights on crust behavior are also revealed.

  4. Water state characterization, swelling behavior, thermal and mechanical properties of chitosan based networks.

    PubMed

    Khalid, M N; Agnely, F; Yagoubi, N; Grossiord, J L; Couarraze, G

    2002-06-01

    Two kinds of chitosan-based hydrogels, a crosslinked chitosan reference gel and a chitosan-poly(ethylene oxide) semi-interpenetrating network (semi-IPN), with potential pH-sensitive swelling and drug delivery properties are characterized. Swelling studies were performed on the two kinds of hydrogels by differential scanning calorimetry (DSC) at pH 1.2 and by the gravimetric method at pH 1.2 and pH 7.2. Both methods lead to similar results. If pH-dependent swelling properties were observed with both hydrogels, they were however improved for the semi-IPN. The amount of bound water in the xerogels could be determined from DSC measurements and a thermogravimetric analysis. The results obtained by both techniques were in good agreement and indicated that the semi-IPN contained more bound water than the reference gel probably due to the presence of the hydrophilic poly(ethylene oxide) chains. Young modulus of the swollen hydrogels was determined by indentation analysis. The semi-IPN displayed improved mechanical properties compared to the reference gel.

  5. MELCOR 1.8.3 assessment: GE large vessel blowdown and level swell experiments

    SciTech Connect

    Kmetyk, L.N.

    1994-07-01

    MELCOR is a fully integrated, engineering-level computer code, being developed at Sandia National Laboratories for the USNRC, that models the entire spectrum of severe accident phenomena in a unified framework for both BWRs and PWRS. As part of an ongoing assessment program, the MELCOR computer code has been used to analyze a series of blowdown tests performed in the early 1980s at General Electric. The GE large vessel blowdown and level swell experiments are a set of primary system thermal/hydraulic separate effects tests studying the level swell phenomenon for BWR transients and LOCAS; analysis of these GE tests is intended to validate the new implicit bubble separation algorithm added since the release of MELCOR 1.8.2. Basecase MELCOR results are compared to test data, and a number of sensitivity studies on input modelling parameters and options have been done. MELCOR results for these experiments also are compared to MAAP and TRAC-B qualification analyses for the same tests. Time-step and machine-dependency calculations were done to identify whether any numeric effects exist in our GE large vessel blowdown and level swell assessment analyses.

  6. Tuning of cellulose fibres' structure and surface topography: Influence of swelling and various drying procedures.

    PubMed

    Hribernik, Silvo; Stana Kleinschek, Karin; Rihm, Rainer; Ganster, Johannes; Fink, Hans-Peter; Sfiligoj Smole, Majda

    2016-09-01

    Presented study deals with the pre-treatment of cellulose fibres with the aim to activate their surface and to enlarge their pore system, leading to an enhancement of fibres' affinity for subsequent functionalization processes. Swelling of fibres in aqueous solutions of sodium hydroxide opens their fibrillar structure, while freezing and freeze-drying retain this enlargement of the pore system, in contrast with conventional air or elevated temperature drying. Effect of different pre-treatment procedures on fibres' supramolecular structure, enlargement of their pore system, surface topography, zeta potential and mechanical properties was investigated. Degree of enhancement of the pore system depends on the concentration of sodium hydroxide and type of freezing; higher alkali concentrations are more effective, but at the cost of extensive deterioration of mechanical properties. Swelling of fibres in lower concentrations of NaOH, in combination with freeze drying, offers an acceptable compromise between enhancement of the fibres' pore system, changes in surface potential and tensile properties of treated fibres. Design of a suitable regime of swelling and drying of cellulose fibres results in an effective procedure for controlled tuning of their surface topography in combination with an increase of the available internal surface area and pore volume.

  7. In situ nanomechanical characterization of the early stages of swelling and degradation of a biodegradable polymer.

    PubMed

    Dumitru, A C; Espinosa, F M; Garcia, R; Foschi, G; Tortorella, S; Valle, F; Dallavalle, M; Zerbetto, F; Biscarini, F

    2015-03-12

    The interactions of a biodegradable scaffold with cells or living tissues depend on the time-evolution of the nanoscale properties of the scaffold. We present an in situ quantitative study on the early-stage swelling and degradation of poly(lactic-co-glycolic acid) (PLGA). A novel metrology scheme based on force microscopy measurements of the patterns of PLGA nanostructures is developed to characterize the evolution of topography, volume and nanomechanical properties. The volume and nanoscale roughness show an oscillating behaviour during the first eight days of immersion; at a later stage, we observe a continuous decrease of the volume. The effective Young's modulus exhibits a monotonic decrease from an initial value of about 2.4 GPa down to 9 MPa at day 14. The oscillating behaviour of the volume before the onset of full degradation is explained by a coupled diffusion-swelling mechanism. The appearance of a second maximum in the volume evolution results from the competition between swelling and degradation.

  8. Tuning of cellulose fibres' structure and surface topography: Influence of swelling and various drying procedures.

    PubMed

    Hribernik, Silvo; Stana Kleinschek, Karin; Rihm, Rainer; Ganster, Johannes; Fink, Hans-Peter; Sfiligoj Smole, Majda

    2016-09-01

    Presented study deals with the pre-treatment of cellulose fibres with the aim to activate their surface and to enlarge their pore system, leading to an enhancement of fibres' affinity for subsequent functionalization processes. Swelling of fibres in aqueous solutions of sodium hydroxide opens their fibrillar structure, while freezing and freeze-drying retain this enlargement of the pore system, in contrast with conventional air or elevated temperature drying. Effect of different pre-treatment procedures on fibres' supramolecular structure, enlargement of their pore system, surface topography, zeta potential and mechanical properties was investigated. Degree of enhancement of the pore system depends on the concentration of sodium hydroxide and type of freezing; higher alkali concentrations are more effective, but at the cost of extensive deterioration of mechanical properties. Swelling of fibres in lower concentrations of NaOH, in combination with freeze drying, offers an acceptable compromise between enhancement of the fibres' pore system, changes in surface potential and tensile properties of treated fibres. Design of a suitable regime of swelling and drying of cellulose fibres results in an effective procedure for controlled tuning of their surface topography in combination with an increase of the available internal surface area and pore volume. PMID:27185135

  9. A new scleroglucan/borax hydrogel: swelling and drug release studies.

    PubMed

    Coviello, Tommasina; Grassi, Mario; Palleschi, Antonio; Bocchinfuso, Gianfranco; Coluzzi, Gina; Banishoeib, Fateme; Alhaique, Franco

    2005-01-31

    The aim of the work was the characterization of a new polysaccharidic physical hydrogel, obtained from Scleroglucan (Sclg) and borax, following water uptake and dimension variations during the swelling process. Furthermore, the release of molecules of different size (Theophylline (TPH), Vitamin B12 (Vit. B12) and Myoglobin (MGB)) from the gel and from the dried system used as a matrix for tablets was studied. The increase of weight of the tablets with and without the loaded drugs was followed together with the relative variation of the dimensions. The dry matrix, in the form of tablets was capable, during the swelling process, to incorporate a relevant amount of solvent (ca. 20 g water/g dried matrix), without dissolving in the medium, leading to a surprisingly noticeable anisotropic swelling that can be correlated with a peculiar supramolecular structure of the system induced by compression. Obtained results indicate that the new hydrogel can be suitable for sustained drug release formulations. The delivery from the matrix is deeply dependent on the size of the tested model drugs. The experimental release data obtained from the gel were satisfactorily fitted by an appropriate theoretical approach and the relative drug diffusion coefficients in the hydrogel were estimated. The release profiles of TPH, Vit. B12 and MGB from the tablets have been analyzed in terms of a new mathematical approach that allows calculating of permeability values of the loaded drugs.

  10. Hypobaric Conditions Within Rock Void Spaces on Mars will Likely Inhibit the Replication of Terrestrial Microorganisms

    NASA Astrophysics Data System (ADS)

    Schuerger, A. C.; Britt, D.

    2011-03-01

    Internal void spaces within rocks outgas rapidly under simulated martian conditions. Water activity and pressure within rock void spaces are not sufficient to permit the replication of terrestrial microorganisms from spacecraft on Mars.

  11. Collagen VI regulates pericellular matrix properties, chondrocyte swelling, and mechanotransduction in articular cartilage

    PubMed Central

    Zelenski, Nicole A.; Leddy, Holly A.; Sanchez-Adams, Johannah; Zhang, Jinzi; Bonaldo, Paolo; Liedtke, Wolfgang; Guilak, Farshid

    2015-01-01

    Objective Mechanical factors play a critical role in the physiology and pathology of articular cartilage, although the mechanisms of mechanical signal transduction are not fully understood. We examined the hypothesis that type VI collagen is necessary for mechanotransduction in articular cartilage, by determining the effects of type VI collagen knockout on the activation of the mechano-osmosensitive calcium-permeable channel, transient receptor potential vanilloid 4 (TRPV4), osmotically-induced chondrocyte swelling, and pericellular matrix (PCM) mechanical properties. Methods Confocal laser scanning microscopy was used to image TRPV4-mediated calcium signaling and osmotically-induced cell swelling in intact femora from 2 and 9 month old wild type (WT) and type VI collagen deficient (Col6a1−/−) mice. Immunofluorescence-guided atomic force microscopy was used to map PCM mechanical properties based on the presence of perlecan. Results Hypo-osmotic stress induced TRPV4-mediated calcium signaling was increased in Col6a1−/− mice relative to WT controls at 2 months. Col6a1−/− mice exhibited significantly increased osmotically-induced cell swelling and decreased PCM moduli relative to WT controls at both ages. Conclusion In contrast to our original hypothesis, type VI collagen was not required for TRPV4-mediated Ca2+ signaling; however, knockout of type VI collagen altered the mechanical properties of the PCM, which in turn increased the extent of cell swelling and osmotically-induced TRPV4 signaling in an age-dependent manner. These findings emphasize the role of the PCM as a transducer of mechanical and physicochemical signals, and suggest that alterations in PCM properties, as may occur with aging or osteoarthritis, can influence mechanotransduction via TRPV4 or other ion channels. PMID:25604429

  12. Swelling equilibria for temperature-sensitive ampholytic hydrogels

    SciTech Connect

    Baker, J.P.; Stephens, D.R.; Blanch, H.W.; Prausnitz, J.M.

    1992-09-01

    Temperature-sensitive N-isopropylacrylamide (NIPA)-based ampho-lytic hydrogels were synthesized by copolymerizing NIPA with the cationic monomer methacrylamidopropyl trimethylammonium chloride (MAPTAC) and the anionic monomer sodium styrene sulfonate (SSS). The total nominal charge density of the hydrogels was held constant at 8 mol % (dry basis), while the molar ratio of anionic to cationic moieties within the hydrogels was varied. Swelling equilibria were measured in water at 6C, and in aqueous sodium chloride solutions ranging in concentration from 10{sup {minus}5}to 5 M and temperature ranging from 6 to 56C. Consistent with expectations, the swelling behavior of the hydrogels was found to be controlled by temperature at low salt concentrations; as the sodium chloride concentration increased, temperature control of hydrogel swelling decreased. Slight antipolyelectrolyte behavior was observed for the hydrogel prepared with equal molar amounts of MAPTAC and SSS.

  13. Depleting depletion: Polymer swelling in poor solvent mixtures

    NASA Astrophysics Data System (ADS)

    Mukherji, Debashish; Marques, Carlos; Stuehn, Torsten; Kremer, Kurt

    A polymer collapses in a solvent when the solvent particles dislike monomers more than the repulsion between monomers. This leads to an effective attraction between monomers, also referred to as depletion induced attraction. This attraction is the key factor behind standard polymer collapse in poor solvents. Strikingly, even if a polymer exhibits poor solvent condition in two different solvents, it can also swell in mixtures of these two poor solvents. This collapse-swelling-collapse scenario is displayed by poly(methyl methacrylate) (PMMA) in aqueous alcohol. Using molecular dynamics simulations of a thermodynamically consistent generic model and theoretical arguments, we unveil the microscopic origin of this phenomenon. Our analysis suggests that a subtle interplay of the bulk solution properties and the local depletion forces reduces depletion effects, thus dictating polymer swelling in poor solvent mixtures.

  14. Swelling of several commercial alloys following high fluence neutron irradiation

    SciTech Connect

    Powell, R.W.; Peterson, D.T.; Zimmerschied, M.K.; Bates, J.F.

    1981-01-01

    Swelling values have been determined for a set of commercial alloys irradiated to a peak fluence of 17.8 x 10/sup 22/ n/cm/sup 2/ (E > 0.1 MeV) over the temperature range of 400 to 650/sup 0/C. The alloys studied fall into three classes: the ferritic alloys AISI 430F, AISI 416, EM-12, H-11 and 2 1/4 Cr-1 Mo; the superalloys Inconel 718 and Inconel X-750; and the refractory alloys TZM and Nb-1 Zr. After irradiation to a peak fluence approaching goal exposures envisioned for advanced fusion reactor first walls, all of the alloys display swelling resistance far superior to cold worked AISI 316. Of the three alloy classes examined the swelling resistance of the ferritics is the least sensitive to composition.

  15. Adsorption and strain: The CO 2-induced swelling of coal

    NASA Astrophysics Data System (ADS)

    Vandamme, M.; Brochard, L.; Lecampion, B.; Coussy, O.

    2010-10-01

    Enhanced coal bed methane recovery (ECBM) consists in injecting carbon dioxide in coal bed methane reservoirs in order to facilitate the recovery of the methane. The injected carbon dioxide gets adsorbed at the surface of the coal pores, which causes the coal to swell. This swelling in confined conditions leads to a closure of the coal reservoir cleat system, which hinders further injection. In this work we provide a comprehensive framework to calculate the macroscopic strains induced by adsorption in a porous medium from the molecular level. Using a thermodynamic approach we extend the realm of poromechanics to surface energy and surface stress. We then focus on how the surface stress is modified by adsorption and on how to estimate adsorption behavior with molecular simulations. The developed framework is here applied to the specific case of the swelling of CO 2-injected coal, although it is relevant to any problem in which adsorption in a porous medium causes strains.

  16. Non-breaking swell dissipation from synthethic aperture radar

    NASA Astrophysics Data System (ADS)

    Stopa, Justin; Husson, Romain; Ardhuin, Fabrice; Collard, Fabrice; Chapron, Bertrand

    2015-04-01

    Swells have the unique ability to propagate away from their generation region with very little attenuation. Only one study exists in the ocean wave literature that measures the decay rate by following a swell with in-situ measurements along its great circle route. More recently used space-borne synthetic aperture radar (SAR) to measure the attenuation. They estimated the dissipation rate from SAR with a limited number of cases: 11 storms with 22 total events. The present work extrapolates their technique to more events since ENVISAT has collected SAR data from 2002-2012. The dissipation rate is then determined in a two step process. First swell sources are identified from density maps of back-propagated waves at their group velocity along great circles. Next a "point-source" model is assumed and the waves from all directions and frequencies are propagated forward to find matching SAR observations. Relatively small directional bins are used to group observations creating transects from a given swell event. This ensemble of tracks is the basic dataset used to calculate a more statistically robust measure of the dissipation rate. Individual tracks and the swell behavior are explored through this dataset. Our results are in agreement with previous findings and it is verified that swells are very persistent with e-folding scales larger than 20,000 km and they behave nonlinearly as a function of wave frequency. The results are discussed in terms of their implications in spectral wave models as well as identify limitations of the remotely sensed wave spectra. The wind's role on the dissipation rate cannot be determined from this analysis stressing the need for concurrent wind and wave observations.

  17. Swelling of cross-linked polystyrene spheres in toluene vapor

    SciTech Connect

    Zhang, R.; Graf, K.; Berger, R.

    2006-11-27

    The swelling behavior of individual micron-sized polystyrene (PS) spheres in toluene vapor was studied via mass loading by means of micromechanical cantilever sensors. For 4%-8% cross-linked PS a mass increase of 180% in saturated toluene vapor was measured. The mass of the swollen PS sphere decreases with increasing exposure time to ultraviolet light. In addition, the swelling response is significantly different between the first and the second exposure to toluene vapor. This is attributed to the formation of a cross-linked shell at the surface of the PS spheres. Shape persistent parts were observed for locally irradiated PS spheres.

  18. Compression and swelling of activated sludge cakes during dewatering.

    PubMed

    Sveegaard, Steffen Gralert; Keiding, Kristian; Christensen, Morten Lykkegaard

    2012-10-15

    A drainage/filtration apparatus was developed for automatically determining sedimentation velocity and dewatering rate. Pressure-step testing was used to study filter cake compressibility, resistance, and swelling. Activated sludge was analysed, and the data indicate that the sludge is highly compressible even at low pressures (10 kPa). Furthermore, compressed sludge cakes swell if the pressure is released. Hence, the average specific cake resistance decreases if the pressure is released, though the resistance is higher after the compression cycle than before. Sludge must be dewatered under low pressure, because higher pressure only compresses the cake and does not improve the dewatering rate.

  19. 21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Resorbable calcium salt bone void filler device... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3045 Resorbable calcium salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device...

  20. 21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Resorbable calcium salt bone void filler device... SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3045 Resorbable calcium salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device...

  1. 46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam,...

  2. 46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam,...

  3. 46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam,...

  4. 46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam,...

  5. 46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam,...

  6. Nondestructive Creation of Ordered Nanopores by Selective Swelling of Block Copolymers: Toward Homoporous Membranes.

    PubMed

    Wang, Yong

    2016-07-19

    Pores regulate the entry and exit of substances based on the differences in physical sizes or chemical affinities. Pore uniformity, ordering, and the homogeneity of the surface chemistry of the pore walls are vital for maximizing the performance of a porous material because any scattering in these parameters weakens the capability of pores to discriminate foreign substances. Most strategies for the creation of homogeneous pores are destructive, and sacrificial components in the precursor materials must be selectively removed to generate porosities. The incorporation and subsequent removal of the sacrificial components frequently make the pore-making process complicated and inefficient and impose greater uncertainty in the control of the pore homogeneity. Block copolymers (BCPs) have been demonstrated to be promising precursors in the fabrication of highly ordered nanoporous structures. Unfortunately, BCP-derived porosities are also predominantly dependent on destructive pore-making processes (e.g., etching or extraction). To address this problem, we have developed a swelling-based nondestructive strategy. In this swelling process, one simply needs to immerse BCP materials in a solvent selective for the minority blocks for hours. After removing the BCPs from the solvent followed by air drying, pores are generated throughout the BCP materials in the positions where the minority blocks initially dwell. This Account discusses our recent discoveries, new insights, and emerging applications of this burgeoning pore-making method with a focus on the development of ordered porosities in bulk BCP materials. The initial morphology and orientation of the minority phases in BCPs determine the pore orientation and geometry in the produced porous materials. For nonaligned BCPs, three-dimensionally interconnected pores with sizes scattering in the 10-50 nm range are produced after swelling. There is a morphology evolution of BCP materials from the initial nonporous structure to

  7. Thermodynamic model for swelling of unconfined coal due to adsorption of mixed gases

    NASA Astrophysics Data System (ADS)

    Liu, Jinfeng; Peach, Colin; Spiers, Christopher

    2013-04-01

    gases, the adsorbed concentrations predicted reduce to the Langmuir isotherm for mixed gases. 3) Preferential adsorption sites model. This assumes adsorption sites show selectivity towards one gas, i.e. nsα adsorption sites can be occupied by both gases (cf. 2) while only (nsα -nsβ) adsorption sites can be occupied by gas β ( cf. 1). This model can be treated as a combination of Models 1 and 2. We compared these models to experimental measurements of swelling of an Australian sub-bituminous coal exposed to CH4, CO2 and to their mixtures at pressures up to 15 MPa, performed by Day et al. (2012, IJCG, 93, 40-48). Compared to other two models, the preferential adsorption sites model describes the experimental results best. This finding complies with the conventional view that CH4 is displaced by CO2 due to both depletion of CH4 partial pressure and preferential CO2 adsorption. However, our findings contradict the proposal by Day et al., based on their experiments, that CH4 and CO2 have access to all adsorption sites and that swelling solely depends on partial pressures. Additional experiments on different rank coals and gas species are underway to evaluate our models further.

  8. On the void explanation of the Cold Spot

    NASA Astrophysics Data System (ADS)

    Marcos-Caballero, A.; Fernández-Cobos, R.; Martínez-González, E.; Vielva, P.

    2016-07-01

    The integrated Sachs-Wolfe (ISW) contribution induced on the cosmic microwave background by the presence of a supervoid as the one detected by Szapudi et al. (2015) is reviewed in this letter in order to check whether it could explain the Cold Spot (CS) anomaly. Two different models, previously used for the same purpose, are considered to describe the matter density profile of the void: a top hat function and a compensated profile produced by a Gaussian potential. The analysis shows that, even enabling ellipticity changes or different values for the dark-energy equation of state parameter ω, the ISW contribution due to the presence of the void does not reproduce the properties of the CS.

  9. Shock wave induced damage of a protein by void collapse

    DOE PAGESBeta

    Lau, Edmond Y.; Berkowitz, Max L.; Schwegler, Eric R.

    2016-01-05

    In this study, we report on a series of molecular dynamics simulations that were used to examine the effects of shockwaves on a membrane bound ion channel. A planar shockwave was found to compress the ion channel upon impact but the protein geometry resembles the initial structure as soon as the solvent density begins to dissipate. When a void was placed in close proximity to the membrane, the shockwave proved to be much more destructive to the protein due to formation of a nanojet that results from the asymmetric collapse of the void. The nanojet was able to cause significantmore » structural changes to the protein even at low particle velocities that are not able to directly cause poration of the membrane.« less

  10. The ISW imprints of voids and superclusters on the CMB

    NASA Astrophysics Data System (ADS)

    Hotchkiss, S.; Nadathur, S.; Gottlöber, S.; Iliev, I. T.; Knebe, A.; Watson, W. A.; Yepes, G.

    2016-10-01

    We examine the stacked integrated Sachs-Wolfe (ISW) imprints on the CMB along the lines of sight of voids and superclusters in galaxy surveys, using the Jubilee ISW simulation and mock luminous red galaxy (LRG) catalogues. We show that the expected signal in the concordance \\Lam CDM model is much smaller than the primary anisotropies arising at the last scattering surface and therefore any currently claimed detections of such an imprint cannot be caused by the ISW effect in \\Lam CDM. We look for the existence of such a signal in the Planck CMB using a catalogue of voids and superclusters from the Sloan Digital Sky Survey (SDSS), but find a result completely consistent with \\Lam CDM - i.e., a null detection.

  11. Simulated diabetic ketoacidosis therapy in vitro elicits brain cell swelling via sodium-hydrogen exchange and anion transport.

    PubMed

    Rose, Keeley L; Watson, Andrew J; Drysdale, Thomas A; Cepinskas, Gediminas; Chan, Melissa; Rupar, C Anthony; Fraser, Douglas D

    2015-08-15

    A common complication of type 1 diabetes mellitus is diabetic ketoacidosis (DKA), a state of severe insulin deficiency. A potentially harmful consequence of DKA therapy in children is cerebral edema (DKA-CE); however, the mechanisms of therapy-induced DKA-CE are unknown. Our aims were to identify the DKA treatment factors and membrane mechanisms that might contribute specifically to brain cell swelling. To this end, DKA was induced in juvenile mice with the administration of the pancreatic toxins streptozocin and alloxan. Brain slices were prepared and exposed to DKA-like conditions in vitro. Cell volume changes were imaged in response to simulated DKA therapy. Our experiments showed that cell swelling was elicited with isolated DKA treatment components, including alkalinization, insulin/alkalinization, and rapid reductions in osmolality. Methyl-isobutyl-amiloride, a nonselective inhibitor of sodium-hydrogen exchangers (NHEs), reduced cell swelling in brain slices elicited with simulated DKA therapy (in vitro) and decreased brain water content in juvenile DKA mice administered insulin and rehydration therapy (in vivo). Specific pharmacological inhibition of the NHE1 isoform with cariporide also inhibited cell swelling, but only in the presence of the anion transport (AT) inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid. DKA did not alter brain NHE1 isoform expression, suggesting that the cell swelling attributed to the NHE1 was activity dependent. In conclusion, our data raise the possibility that brain cell swelling can be elicited by DKA treatment factors and that it is mediated by NHEs and/or coactivation of NHE1 and AT.

  12. A new least-squares transport equation compatible with voids

    SciTech Connect

    Hansen, J. B.; Morel, J. E.

    2013-07-01

    We define a new least-squares transport equation that is applicable in voids, can be solved using source iteration with diffusion-synthetic acceleration, and requires only the solution of an independent set of second-order self-adjoint equations for each direction during each source iteration. We derive the equation, discretize it using the S{sub n} method in conjunction with a linear-continuous finite-element method in space, and computationally demonstrate various of its properties. (authors)

  13. Stem cell therapy for voiding and erectile dysfunction

    PubMed Central

    Vaegler, Martin; Lenis, Andrew T; Daum, Lisa; Renninger, M; Bastian, Amend; Stenzl, Arnulf; Damaser, Margot S; Sievert, Karl-Dietrich

    2013-01-01

    Voiding dysfunction comprises a variety of disorders, including stress urinary incontinence and overactive bladder, and affects millions of men and women worldwide. Erectile dysfunction (ED) also decreases quality of life for millions of men, as well as for their partners. Advanced age and diabetes are common comorbidities that can exacerbate and negatively impact upon the development of these disorders. Therapies that target the pathophysiology of these conditions to halt progression are not currently available. However, stem cell therapy could fill this therapeutic void. Stem cells can reduce inflammation, prevent fibrosis, promote angiogenesis, recruit endogenous progenitor cells, and differentiate to replace damaged cells. Adult multipotent stem cell therapy, in particular, has shown promise in case reports and preclinical animal studies. Stem cells have also enabled advances in urological tissue engineering by facilitating ex vivo construction of bladder wall and urethral tissue (using a patient's own cells) prior to transplantation. More recent studies have focused on bioactive factor secretion and homing of stem cells. In the future, clinicians are likely to utilize allogeneic stem cell sources, intravenous systemic delivery, and ex vivo cell enhancement to treat voiding dysfunction and ED. PMID:22710667

  14. The distribution of IRAS galaxies towards the Bootes void

    NASA Technical Reports Server (NTRS)

    Strauss, Michael A.; Huchra, John

    1988-01-01

    A redshift survey was completed for 342 galaxies detected by the IRAS in the direction of the Bootes void discovered by Kirshner et al. The number density of IRAS galaxies is well determined from the shallower full-sky redshift survey of Strauss et al. Four IRAS galaxies are found within the void as defined by Kirshner et al., of which three are part of a complete sample, implying a density depression of a factor of 4. The underdense region continues to a distance of at least 4000 km/s from the nominal center of the void. Three of the IRAS galaxies studied in this paper were previously unknown. These galaxies have emission-line spectra characteristic of H II regions, and red continuum magnitudes ranging from 16 to 17.5 mag, and thus are bright enough to have been detected in a wide-angle redshift survey as deep as that of Kirshner et al. The luminosity function derived from this sample is in good agreement with that of Lawrence et al.

  15. Nebular metallicities in two isolated local void dwarf galaxies

    SciTech Connect

    Nicholls, David C.; Jerjen, Helmut; Dopita, Michael A.; Basurah, Hassan

    2014-01-01

    Isolated dwarf galaxies, especially those situated in voids, may provide insight into primordial conditions in the universe and the physical processes that govern star formation in undisturbed stellar systems. The metallicity of H II regions in such galaxies is key to investigating this possibility. From the SIGRID sample of isolated dwarf galaxies, we have identified two exceptionally isolated objects, the Local Void galaxy [KK98]246 (ESO 461-G036) and another somewhat larger dwarf irregular on the edge of the Local Void, MCG-01-41-006 (HIPASS J1609-04). We report our measurements of the nebular metallicities in these objects. The first object has a single low luminosity H II region, while the second is in a more vigorous star forming phase with several bright H II regions. We find that the metallicities in both galaxies are typical for galaxies of this size, and do not indicate the presence of any primordial gas, despite (for [KK98]246) the known surrounding large reservoir of neutral hydrogen.

  16. A method for determining void arrangements in inverse opals.

    PubMed

    Blanford, C F; Carter, C B; Stein, A

    2004-12-01

    The periodic arrangement of voids in ceramic materials templated by colloidal crystal arrays (inverse opals) has been analysed by transmission electron microscopy. Individual particles consisting of an approximately spherical array of at least 100 voids were tilted through 90 degrees along a single axis within the transmission electron microscope. The bright-field images of these particles at high-symmetry points, their diffractograms calculated by fast Fourier transforms, and the transmission electron microscope goniometer angles were compared with model face-centred cubic, body-centred cubic, hexagonal close-packed, and simple cubic lattices in real and reciprocal space. The spatial periodicities were calculated for two-dimensional projections. The systematic absences in these diffractograms differed from those found in diffraction patterns from three-dimensional objects. The experimental data matched only the model face-centred cubic lattice, so it was concluded that the packing of the voids (and, thus, the polymer spheres that composed the original colloidal crystals) was face-centred cubic. In face-centred cubic structures, the stacking-fault displacement vector is a/6<211> . No stacking faults were observed when viewing the inverse opal structure along the orthogonal <110>-type directions, eliminating the possibility of a random hexagonally close-packed structure for the particles observed. This technique complements synchrotron X-ray scattering work on colloidal crystals by allowing both real-space and reciprocal-space analysis to be carried out on a smaller cross-sectional area.

  17. Piezoelectric performance of fluor polymer sandwiches with different void structures

    NASA Astrophysics Data System (ADS)

    Lou, Kexing; Zhang, Xiaoqing; Xia, Zhongfu

    2012-06-01

    Film sandwiches, consisting of two outer layers of fluoroethylenepropylene and one middle layer of patterned porous polytetrafluoroethylene, were prepared by patterning and fusion bonding. Contact charging was conducted to render the films piezoelectric. The critical voltage to trigger air breakdown in the inner voids in the fabricated films was investigated. The piezoelectric d 33 coefficients were measured employing the quasistatic method and dielectric resonance spectrum. The results show that the critical voltage for air breakdown in the inner voids is associated with the void microstructure of the films. For the films with patterning factors of 0%, 25% and 44%, the critical values are 300, 230 and 230 kV/cm, respectively. With an increase in the patterning factor, both the piezoelectric d 33 coefficients determined from the dielectric resonance spectra and those determined from quasistatic measurements increase, which might be due to a decrease in Young's modulus for the films. The nonlinearity of d 33 becomes increasingly obvious as the patterning factor increases.

  18. How does a flexible chain of active particles swell?

    PubMed

    Kaiser, Andreas; Babel, Sonja; ten Hagen, Borge; von Ferber, Christian; Löwen, Hartmut

    2015-03-28

    We study the swelling of a flexible linear chain composed of active particles by analytical theory and computer simulation. Three different situations are considered: a free chain, a chain confined to an external harmonic trap, and a chain dragged at one end. First, we consider an ideal chain with harmonic springs and no excluded volume between the monomers. The Rouse model of polymers is generalized to the case of self-propelled monomers and solved analytically. The swelling, as characterized by the spatial extension of the chain, scales with the monomer number defining a Flory exponent ν which is ν = 1/2, 0, 1 in the three different situations. As a result, we find that activity does not change the Flory exponent but affects the prefactor of the scaling law. This can be quantitatively understood by mapping the system onto an equilibrium chain with a higher effective temperature such that the chain swells under an increase of the self-propulsion strength. We then use computer simulations to study the effect of self-avoidance on active polymer swelling. In the three different situations, the Flory exponent is now ν = 3/4, 1/4, 1 and again unchanged under self-propulsion. However, the chain extension behaves non-monotonic in the self-propulsion strength.

  19. Swelling and drug release from oral thin films (OTFs)

    NASA Astrophysics Data System (ADS)

    Adrover, A.; Casadei, M. A.; Paolicelli, P.; Petralito, S.; Varani, G.

    2016-05-01

    We investigate the characteristic time-scales for swelling and drug release from polymeric thin films for buccal delivery. In this work, novel OTFs were prepared combining Gellan gum, a natural polysaccharide well known in the pharmaceutical field, along with Glycerol, used as plasticizer. A new millifluidic flow-through device is adopted for in-vitro release tests.

  20. Linear Viscoelasticity and Swelling of Polyelectrolyte Complex Coacervates

    NASA Astrophysics Data System (ADS)

    Hamad, Fawzi; Colby, Ralph

    2012-02-01

    The addition of near equimolar amounts of poly(diallyldimethylammonium chloride) to poly(isobutylene-alt-maleate sodium), results in formation of a polyelectrolyte complex coacervate. Zeta-potential titrations conclude that these PE-complexes are nearly charge-neutral. Swelling and rheological properties are studied at different salt concentrations in the surrounding solution. The enhanced swelling observed at high salt concentration suggests the system behaves like a polyampholyte gel, and weaker swelling at very low salt concentrations implies polyelectrolyte gel behavior. Linear viscoelastic oscillatory shear measurements indicate that the coacervates are viscoelastic liquids and that increasing ionic strength of the medium weakens the electrostatic interactions between charged units, lowering the relaxation time and viscosity. We use the time-salt superposition idea recently proposed by Spruijt, et al., allowing us to construct master curves for these soft materials. Similar swelling properties observed when varying molecular weights. Rheological measurements reveal that PE-complexes with increasing molecular weight polyelectrolytes form a network with higher crosslink density, suggesting time-molecular weight superposition idea.

  1. Impedimetric transduction of swelling in pH-responsive hydrogels.

    PubMed

    Mac Kenna, Nicky; Calvert, Paul; Morrin, Aoife

    2015-05-01

    A pH-responsive hydrogel composed of an aliphatic diamine cross-linked with polyethylene glycol diglycidyl ether (PEGDGE) using a single, rapid polymerisation step has been used to detect glucose by entrapping glucose oxidase (GOx) within its cationic network. The swelling response of hydrogel disks on exposure to glucose were optimised through variation of factors including the cross-linking density of the network, GOx loading and the addition of catalase. Hydrogel-modified carbon cloth electrodes were also prepared and characterised using voltammetric and impedimetric techniques. Non-faradaic electrochemical impedance spectroscopy (EIS) and gravimetry were both employed to track the swelling response of the gels quantitatively. The clear potential of utilising impedance to transduce hydrogel swelling was demonstrated where a linear decrease in gel resistance (Rgel) corresponding to the swelling response was observed in the range 1 to 100 μM. A dramatic increase in the limit of detection of six orders of magnitude over the gravimetric measurement was achieved (from 0.33 mM to 0.08 μM). This increased sensitivity, coupled with the textile-based electrode substrate approach opens the potential applicability of this system for monitoring glucose concentration via the skin by sweat or interstitial fluid (ISF). PMID:25768307

  2. Impedimetric transduction of swelling in pH-responsive hydrogels.

    PubMed

    Mac Kenna, Nicky; Calvert, Paul; Morrin, Aoife

    2015-05-01

    A pH-responsive hydrogel composed of an aliphatic diamine cross-linked with polyethylene glycol diglycidyl ether (PEGDGE) using a single, rapid polymerisation step has been used to detect glucose by entrapping glucose oxidase (GOx) within its cationic network. The swelling response of hydrogel disks on exposure to glucose were optimised through variation of factors including the cross-linking density of the network, GOx loading and the addition of catalase. Hydrogel-modified carbon cloth electrodes were also prepared and characterised using voltammetric and impedimetric techniques. Non-faradaic electrochemical impedance spectroscopy (EIS) and gravimetry were both employed to track the swelling response of the gels quantitatively. The clear potential of utilising impedance to transduce hydrogel swelling was demonstrated where a linear decrease in gel resistance (Rgel) corresponding to the swelling response was observed in the range 1 to 100 μM. A dramatic increase in the limit of detection of six orders of magnitude over the gravimetric measurement was achieved (from 0.33 mM to 0.08 μM). This increased sensitivity, coupled with the textile-based electrode substrate approach opens the potential applicability of this system for monitoring glucose concentration via the skin by sweat or interstitial fluid (ISF).

  3. Shrink-swell behavior of soil across a vertisol catena

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shrinking and swelling of soils and the associated formation and closing of cracks can vary spatially within the smallest hydrologic unit subdivision utilized in surface hydrology models. Usually in the application of surface hydrology models, cracking is not considered to vary within a hydrologic u...

  4. A 47-year-old man with tongue swelling.

    PubMed

    Rodríguez-Roa, Maristely; Nazario, Sylvette; Ramos, Cristina

    2016-07-01

    Intermittent tongue angioedema can be the initial presentation of several disorders including angiotensin-converting-enzyme inhibitor induced angioedema and hereditary angioedema. Persistent angioedema on the other hand, can be associated with amyloidosis, tumors, thyroid disorders and acromegaly. We present a case of intermittent episodes of tongue swelling progressing to macroglossia. PMID:27401321

  5. Lupus erythematosus--a case of facial swelling.

    PubMed

    Loescher, A; Edmondson, H D

    1988-04-01

    A case is reported of acute facial swelling following tooth extraction that failed to respond in a normal manner. The patient developed systemic signs and symptoms ultimately revealing the diagnosis of lupus erythematosus. The possibility of soft tissue lesions arising in some forms of lupus is emphasised by this report. PMID:3163493

  6. The Swelling and Destabilization of a Coronal Mass Ejection (abstract)

    NASA Technical Reports Server (NTRS)

    Martin, S. F.; Feynman, J.

    1993-01-01

    We will present and discuss data for a bugle that was particularly well observed. Apparently the swelling of the bugle and its destabilization were caused by the newly emerging flux and its interaction with the pre-existing active regions and coronal structures.

  7. Demonstration of Solvent Differences by Visible Polymer Swelling.

    ERIC Educational Resources Information Center

    Ross, Joseph H.

    1983-01-01

    Effect of the "polarity" of low-polarity solvents on the amount of swelling produced in a solid polymer (demonstrated in an organic chemistry lecture) is also suitable as a laboratory experiment. Students can be assigned to a small group of solvents from the list provided. Procedures and materials needed are included. (Author/JN)

  8. [A former bodybuilder with a swelling on the forearm].

    PubMed

    Strijbos, Ruben M; Zwaard, Ton M

    2015-01-01

    A 56-year-old man came to the general practitioner with a solitary compressible swelling on his left forearm, which enlarged during exercise. The patient reported a history of bodybuilding and he worked as a plasterer. Physical examination revealed primary varicose of the upper extremity, a rare localisation of a common vascular disease.

  9. Anomalous swelling behavior of FM 5055 carbon phenolic composite

    NASA Technical Reports Server (NTRS)

    Stokes, E. H.

    1992-01-01

    The swelling response of a typical carbon phenolic composite was measured in the three primary material directions. The data obtained sugrest that at low and high relative humidities the incremental increase in moisture absorption can be attributed primarily to the resin. At intermediate relative humidities, the water is moving largely into the carbonized fibers.

  10. Advanced liquefaction using coal swelling and catalyst dispersion techniques

    SciTech Connect

    Curtis, C.W. ); Gutterman, C. ); Chander, S. )

    1992-08-26

    Research in this project centers upon developing a new approach to the direct liquefaction of coal to produce an all-distillate product slate at a sizable cost reduction over current technology. The approach integrates all aspects of the coal liquefaction process including coal selection, pretreatment, coal swelling with catalyst impregnation, coal liquefaction experimentation, product recovery with characterization, alternate bottoms processing, and a technical assessment including an economic evaluation. The project is being carried out under contract to the United States Department of Energy. On May 28, 1992, the Department of Energy authorized starting the experimental aspects of this projects; therefore, experimentation at Amoco started late in this quarterly report period. Research contracts with Auburn University, Pennsylvania State University, and Foster Wheeler Development Corporation were signed during June, 1992, so their work was just getting underway. Their work will be summarized in future quarterly reports. A set of coal samples were sent to Hazen Research for beneficiation. The samples were received and have been analyzed. The literature search covering coal swelling has been up-dated, and preliminary coal swelling experiments were carried out. Further swelling experimentation is underway. An up-date of the literature on the liquefaction of coal using dispersed catalysts is nearing completion; it will be included in the next quarterly report.

  11. Case of a non-pulsatile groin swelling.

    PubMed

    Razif, M A Mohamed; Rajasingam, V; Abdullah, B J J

    2002-12-01

    We report a case of a non-pulsatile groin swelling in a 38 years old male drug addict without the typical clinical signs of an aneurysm. Ultrasound revealed a left femoral artery pseudo-aneurysm. He was surgically treated and the vessels were ligated without revascularisation.

  12. Hindered nanoparticle diffusion and void accessibility in a three-dimensional porous medium.

    PubMed

    Skaug, Michael J; Wang, Liang; Ding, Yifu; Schwartz, Daniel K

    2015-02-24

    The inherent pore-scale heterogeneity of many natural and synthetic porous materials can make it difficult to model and predict porous transport because the underlying microscopic processes are often poorly understood. Here we present the results of single-particle tracking experiments in which we followed the pore-scale diffusion of individual nanoparticles, deep within a three-dimensional porous material of moderate porosity. We observed significant hydrodynamic damping of particle motion at subpore length scales, resulting in heterogeneous and spatially dependent mobility. The accessibility of the void space was strongly dependent on particle size, and related to the heterogeneous hydrodynamics. Our results suggest that pore-scale diffusion is more heterogeneous and volume accessibility more limited than previously expected. The method demonstrated here will enable studies of a broad new class of materials including porous polymers of technological interest.

  13. Note: Void effects on eddy current distortion in two-phase liquid metal.

    PubMed

    Kumar, M; Tordjeman, Ph; Bergez, W; Cavaro, M

    2015-10-01

    A model based on the first order perturbation expansion of magnetic flux in a two-phase liquid metal flow has been developed for low magnetic Reynolds number Rem. This model takes into account the distortion of the induced eddy currents due to the presence of void in the conducting medium. Specific experiments with an eddy current flow meter have been realized for two periodic void distributions. The results have shown, in agreement with the model, that the effects of velocity and void on the emf modulation are decoupled. The magnitude of the void fraction and the void spatial frequency can be determined from the spectral density of the demodulated emf. PMID:26521001

  14. Is the far border of the Local Void expanding?

    NASA Astrophysics Data System (ADS)

    Iwata, I.; Chamaraux, P.

    2011-07-01

    Context. According to models of evolution in the hierarchical structure formation scenarios, voids of galaxies are expected to expand. The Local Void (LV) is the closest large void, and it provides a unique opportunity to test observationally such an expansion. It has been found that the Local Group, which is on the border of the LV, is running away from the void center at ~260 km s-1. Aims: In this study we investigate the motion of the galaxies at the far-side border of the LV to examine the presence of a possible expansion. Methods: We selected late-type, edge-on spiral galaxies with radial velocities between 3000 km s-1 and 5000 km s-1, and carried out HI 21 cm line and H-band imaging observations. The near-infrared Tully-Fisher relation was calibrated with a large sample of galaxies and carefully corrected for Malmquist bias. It was used to compute the distances and the peculiar velocities of the LV sample galaxies. Among the 36 sample LV galaxies with good quality HI line width measurements, only 15 galaxies were selected for measuring their distances and peculiar velocities, in order to avoid the effect of Malmquist bias. Results: The average peculiar velocity of these 15 galaxies is found to be -419+208-251 km s-1, which is not significantly different from zero. Conclusions: Due to the intrinsically large scatter of Tully-Fisher relation, we cannot conclude whether there is a systematic motion against the center of the LV for the galaxies at the far-side boundary of the void. However, our result is consistent with the hypothesis that those galaxies at the far-side boundary have an average velocity of ~260 km s-1 equivalent to what is found at the position of the Local Group. Based on data taken at Nançay radiotelescope operated by Observatoire de Paris, CNRS and Université d'Orléans, Infrared Survey Facility (IRSF) which is operated by Nagoya university under the cooperation of South African Astronomical Observatory, Kyoto University, and National

  15. Direct evidence of void passivation in Cu(InGa)(SSe)2 absorber layers

    NASA Astrophysics Data System (ADS)

    Lee, Dongho; Lee, Jaehan; Heo, Sung; Park, Jong-Bong; Kim, Young-Su; Mo, Chan B.; Huh, Kwangsoo; Yang, JungYup; Nam, Junggyu; Baek, Dohyun; Park, Sungchan; Kim, ByoungJune; Kim, Dongseop; Kang, Yoonmook

    2015-02-01

    We have investigated the charge collection condition around voids in copper indium gallium sulfur selenide (CIGSSe) solar cells fabricated by sputter and a sequential process of selenization/sulfurization. In this study, we found direct evidence of void passivation by using the junction electron beam induced current method, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The high sulfur concentration at the void surface plays an important role in the performance enhancement of the device. The recombination around voids is effectively suppressed by field-assisted void passivation. Hence, the generated carriers are easily collected by the electrodes. Therefore, when the S/(S + Se) ratio at the void surface is over 8% at room temperature, the device performance degradation caused by the recombination at the voids is negligible at the CIGSSe layer.

  16. THE WEIGHT OF EMPTINESS: THE GRAVITATIONAL LENSING SIGNAL OF STACKED VOIDS

    SciTech Connect

    Krause, Elisabeth; Dore, Olivier; Chang, Tzu-Ching; Umetsu, Keiichi

    2013-01-10

    The upcoming new generation of spectroscopic galaxy redshift surveys will provide large samples of cosmic voids, large distinct, underdense structures in the universe. Combining these with future galaxy imaging surveys, we study the prospects of probing the underlying matter distribution in and around cosmic voids via the weak gravitational lensing effects of stacked voids, utilizing both shear and magnification information. The statistical precision is greatly improved by stacking a large number of voids along different lines of sight, even when taking into account the impact of inherent miscentering and projection effects. We show that Dark Energy Task Force Stage IV surveys, such as the Euclid satellite and the Large Synoptic Survey Telescope, should be able to detect the void lensing signal with sufficient precision from stacking abundant medium-sized voids, thus providing direct constraints on the matter density profile of voids independent of assumptions on galaxy bias.

  17. Involvement of both sodium influx and potassium efflux in ciguatoxin-induced nodal swelling of frog myelinated axons.

    PubMed

    Mattei, César; Molgó, Jordi; Benoit, Evelyne

    2014-10-01

    Ciguatoxins, mainly produced by benthic dinoflagellate Gambierdiscus species, are responsible for a complex human poisoning known as ciguatera. Previous pharmacological studies revealed that these toxins activate voltage-gated Na+ channels. In frog nodes of Ranvier, ciguatoxins induce spontaneous and repetitive action potentials (APs) and increase axonal volume that may explain alterations of nerve functioning in intoxicated humans. The present study aimed determining the ionic mechanisms involved in Pacific ciguatoxin-1B (P-CTX-1B)-induced membrane hyperexcitability and subsequent volume increase in frog nodes of Ranvier, using electrophysiology and confocal microscopy. The results reveal that P-CTX-1B action is not dependent on external Cl- ions since it was not affected by substituting Cl- by methylsulfate ions. In contrast, substitution of external Na+ by Li+ ions suppressed spontaneous APs and prevented nodal swelling. This suggests that P-CTX-1B-modified Na+ channels are not selective to Li+ ions and/or are blocked by these ions, and that Na+ influx through Na+ channels opened during spontaneous APs is required for axonal swelling. The fact that the K+ channel blocker tetraethylammonium modified, but did not suppress, spontaneous APs and greatly reduced nodal swelling induced by P-CTX-1B indicates that K+ efflux might also be involved. This is supported by the fact that P-CTX-1B, when tested in the presence of both tetraethylammonium and the K+ ionophore valinomycin, produced the characteristic nodal swelling. It is concluded that, during the action of P-CTX-1B, water movements responsible for axonal swelling depend on both Na+ influx and K+ efflux. These results pave the way for further studies regarding ciguatera treatment. PMID:24950451

  18. Irradiation creep and swelling of various austenitic alloys irradiated in PFR and FFTF

    SciTech Connect

    Garner, F.A.; Toloczko, M.B.

    1996-10-01

    In order to use data from surrogate neutron spectra for fusion applications, it is necessary to analyze the impact of environmental differences on property development. This is of particular importance in the study of irradiation creep and its interactions with void swelling, especially with respect to the difficulty of separation of creep strains from various non-creep strains. As part of an on-going creep data rescue and analysis effort, the current study focuses on comparative irradiations conducted on identical gas-pressurized tubes produced and constructed in the United States from austenitic steels (20% CW 316 and 20% CW D9), but irradiated in either the Prototype Fast Reactor (PFR) in the United Kingdom or the Fast Flux Test Facility in the United States. In PFR, Demountable Subassemblies (DMSA) serving as heat pipes were used without active temperature control. In FFTF the specimens were irradiated with active ({+-}{degrees}5C) temperature control. Whereas the FFTF irradiations involved a series of successive side-by-side irradiation, measurement and reinsertion of the same series of tubes, the PFR experiment utilized simultaneous irradiation at two axial positions in the heat pipe to achieve different fluences at different flux levels. The smaller size of the DMSA also necessitated a separation of the tubes at a given flux level into two groups (low-stress and high-stress) at slightly different axial positions, where the flux between the two groups varied {le}10%. Of particular interest in this study was the potential impact of the two types of separation on the derivation of creep coefficients.

  19. In situ microscopy reveals reversible cell wall swelling in kelp sieve tubes: one mechanism for turgor generation and flow control?

    PubMed

    Knoblauch, Jan; Tepler Drobnitch, Sarah; Peters, Winfried S; Knoblauch, Michael

    2016-08-01

    Kelps, brown algae (Phaeophyceae) of the order Laminariales, possess sieve tubes for the symplasmic long-distance transport of photoassimilates that are evolutionarily unrelated but structurally similar to the tubes in the phloem of vascular plants. We visualized sieve tube structure and wound responses in fully functional, intact Bull Kelp (Nereocystis luetkeana [K. Mertens] Postels & Ruprecht 1840). In injured tubes, apparent slime plugs formed but were unlikely to cause sieve tube occlusion as they assembled at the downstream side of sieve plates. Cell walls expanded massively in the radial direction, reducing the volume of the wounded sieve elements by up to 90%. Ultrastructural examination showed that a layer of the immediate cell wall characterized by circumferential cellulose fibrils was responsible for swelling and suggested that alginates, abundant gelatinous polymers of the cell wall matrix, were involved. Wall swelling was rapid, reversible and depended on intracellular pressure, as demonstrated by pressure-injection of silicon oil. Our results revive the concept of turgor generation and buffering by swelling cell walls, which had fallen into oblivion over the last century. Because sieve tube transport is pressure-driven and controlled physically by tube diameter, a regulatory role of wall swelling in photoassimilate distribution is implied in kelps.

  20. In situ microscopy reveals reversible cell wall swelling in kelp sieve tubes: one mechanism for turgor generation and flow control?

    PubMed

    Knoblauch, Jan; Tepler Drobnitch, Sarah; Peters, Winfried S; Knoblauch, Michael

    2016-08-01

    Kelps, brown algae (Phaeophyceae) of the order Laminariales, possess sieve tubes for the symplasmic long-distance transport of photoassimilates that are evolutionarily unrelated but structurally similar to the tubes in the phloem of vascular plants. We visualized sieve tube structure and wound responses in fully functional, intact Bull Kelp (Nereocystis luetkeana [K. Mertens] Postels & Ruprecht 1840). In injured tubes, apparent slime plugs formed but were unlikely to cause sieve tube occlusion as they assembled at the downstream side of sieve plates. Cell walls expanded massively in the radial direction, reducing the volume of the wounded sieve elements by up to 90%. Ultrastructural examination showed that a layer of the immediate cell wall characterized by circumferential cellulose fibrils was responsible for swelling and suggested that alginates, abundant gelatinous polymers of the cell wall matrix, were involved. Wall swelling was rapid, reversible and depended on intracellular pressure, as demonstrated by pressure-injection of silicon oil. Our results revive the concept of turgor generation and buffering by swelling cell walls, which had fallen into oblivion over the last century. Because sieve tube transport is pressure-driven and controlled physically by tube diameter, a regulatory role of wall swelling in photoassimilate distribution is implied in kelps. PMID:26991892