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1

Impact of the proposed core melt policy  

SciTech Connect

Recent encounters with FEMA/NRC and New Jersey have focused our attention on the proposed severe core melt policy. Currently, these federal agencies make the supposition that an automatic evacuation out to 5 miles upon a General Emergency declaration would provide greater protection to the public than an independent grounded assessment which would include the option to shelter. This policy appears to be contrary to EPA-400 and supportable decision making. This talk discusses the policy.

Tosch, K. [Bureau of Nuclear Engineering, Trenton, NJ (United States)

1995-12-31

2

The Annular Core Research Reactor (ACRR) postulated limiting event initial and building source terms  

SciTech Connect

As part of the update of the Safety analysis Report (SAR) for the Annular Core Research Reactor (ACRR), operational limiting events under the category of inadvertent withdrawal of an experiment while at power or during a power pulse were determined to be the most limiting event(s) for this reactor. This report provides a summary of the assumptions, modeling, and results in evaluation of: Reactivity and thermal hydraulics analysis to determine the amount of fuel melt or fuel damage ratios; The reactor inventories following the limiting event; A literature review of post NUREG-0772 release fraction experiment results on severe fuel damages; Decontamination factors due to in-pool transport; and In-building transport modeling and building source term analysis.

Restrepo, L F

1992-08-01

3

The Annular Core Research Reactor (ACRR) postulated limiting event initial and building source terms  

Microsoft Academic Search

As part of the update of the Safety analysis Report (SAR) for the Annular Core Research Reactor (ACRR), operational limiting events under the category of inadvertent withdrawal of an experiment while at power or during a power pulse were determined to be the most limiting event(s) for this reactor. This report provides a summary of the assumptions, modeling, and results

Restrepo

1992-01-01

4

Isotope thermometry in melt-affected ice cores  

NASA Astrophysics Data System (ADS)

A statistically significant relationship is observed between stable water isotopes (?18O) and melt amounts in a melt-affected firn core (SSummit) taken from the Prince of Wales Icefield, Ellesmere Island, Canada. By contrast, a low-melt firn core taken from a higher-elevation, higher-latitude location on the same icefield shows no relationship between these variables. We interpret this as evidence for meltwater-induced isotopic enrichment at SSummit. A percent melt-based correction slope is applied to isotopic values from SSummit. Uncorrected and corrected temperature records derived from the raw and corrected ?18O values are compared to bias-corrected temperature data from the NCEP Reanalysis. Improvements are observed in the isotopic reconstruction of SSummit annual precipitation-weighted temperatures when we correct for meltwater enrichment, with a reduction from +0.6°C to 0.0°C in the mean annual error and a decrease in root-mean-square error from 1.8°C to 1.6°C. The correction factor appears to overcorrect isotopic modification during high melt years such as 1999, during which SSummit experienced nearly 70% more melt than the average from 1975 to 2000. Excluding 1999 data from the correction analysis results in a slight reduction in mean absolute error from 1.4°C to 1.3°C. These results suggest that melt-induced isotopic modification cannot be corrected in very high melt years.

Moran, T.; Marshall, S. J.; Sharp, M. J.

2011-06-01

5

Melting of subducted basalt at the core-mantle boundary.  

PubMed

The geological materials in Earth's lowermost mantle control the characteristics and interpretation of seismic ultra-low velocity zones at the base of the core-mantle boundary. Partial melting of the bulk lower mantle is often advocated as the cause, but this does not explain the nonubiquitous character of these regional seismic features. We explored the melting properties of mid-oceanic ridge basalt (MORB), which can reach the lowermost mantle after subduction of oceanic crust. At a pressure representative of the core-mantle boundary (135 gigapascals), the onset of melting occurs at ~3800 kelvin, which is ~350 kelvin below the mantle solidus. The SiO2-rich liquid generated either remains trapped in the MORB material or solidifies after reacting with the surrounding MgO-rich mantle, remixing subducted MORB with the lowermost mantle. PMID:24855266

Andrault, Denis; Pesce, Giacomo; Bouhifd, Mohamed Ali; Bolfan-Casanova, Nathalie; Hénot, Jean-Marc; Mezouar, Mohamed

2014-05-23

6

Reevaluation of the reconstruction of summer temperatures from melt features in Belukha ice cores, Siberian Altai  

Microsoft Academic Search

In a previous study, past summer temperatures were reconstructed from melt features in the Belukha ice core, Siberian Altai. We evaluated the climatic representativeness of net accumulation and melt features by comparing two Belukha ice cores retrieved at neighboring sites by different institutions and dated by different methods. Melt features in both cores showed a significant correlation, but the trends

Sachiko Okamoto; Koji Fujita; Hideki Narita; Jun Uetake; Nozomu Takeuchi; Takayuki Miyake; Fumio Nakazawa; Vladimir B. Aizen; Stanislav A. Nikitin; Masayoshi Nakawo

2011-01-01

7

Termination of light-water reactor core-melt accidents with a chemical core catcher: the core-melt source reduction system (COMSORS)  

SciTech Connect

The Core-Melt Source Reduction System (COMSORS) is a new approach to terminate light-water reactor core melt accidents and ensure containment integrity. A special dissolution glass is placed under the reactor vessel. If core debris is released onto the glass, the glass melts and the debris dissolves into the molten glass, thus creating a homogeneous molten glass. The molten glass, with dissolved core debris, spreads into a wide pool, distributing the heat for removal by radiation to the reactor cavity above or by transfer to water on top of the molten glass. Expected equilibrium glass temperatures are approximately 600 degrees C. The creation of a low-temperature, homogeneous molten glass with known geometry permits cooling of the glass without threatening containment integrity. This report describes the technology, initial experiments to measure key glass properties, and modeling of COMSORS operations.

Forsberg, C.W.; Parker, G.W.; Rudolph, J.C.; Osborne-Lee, I.W. [Oak Ridge National Lab., TN (United States); Kenton, M.A. [Dames and Moore, Westmont, IL (United States)

1996-09-01

8

Source-term evaluations from recent core-melt experiments  

SciTech Connect

Predicted consequences of hypothetical severe reactor accidents resulting in core meltdown appear to be too conservatively projected because of the simplistic concepts often assumed for the intricate and highly variable phenomena involved. Recent demonstration work on a modest scale (1-kg) has already revealed significant variations in the mode and temperature for clad failure, in the rates of formation of zirconium alloys, in the nature of the UO/sub 2/-ZrO/sub 2/ eutectic mixtures, and in aerosol generation rates. The current series of core-melt demonstration experiments (at the 10-kg scale) seem to confirm that an increase in size of the meltdown mass will lead to an even further reduction in the amount of vaporized components. Source terms that are based on older release evaluations could be up to an order of magnitude too large. 6 refs., 6 figs., 2 tabs.

Parker, G.W.; Creek, G.E.; Sutton, A.L. Jr.

1985-01-01

9

Seismic velocity decrement ratios for regions of partial melt near the core-mantle boundary  

Microsoft Academic Search

For regions of partial melt in the lower mantle, both compressional and shear wave ve- locities decrease monotonically with increasing melt volume fraction. It has been ob- served that regions close to the core-mantle boundary thought to contain partial melt have a velocity decrement ratio (relative change in shear velocity over relative change of com- pressional velocity) of about 3.

James G. Berryman

1999-01-01

10

Temperatures in the earth's core from melting-point measurements of iron at high static pressures  

Microsoft Academic Search

The most reliable method for determining the temperature gradient at the earth's core is the estimation of Fe and Fe-rich compounds' melting temperature at the pressure of the inner core boundary. Attention is presently given to melting-point measurements on Fe and Fe-O compounds at up to 2 Mbar. An extrapolation of these results to 3.3 Mbar yields an inner core

R. Boehler

1993-01-01

11

Modeling of melt retention in EU-APR1400 ex-vessel core catcher  

SciTech Connect

A core catcher is adopted in the EU-APR1400 reactor design for management and mitigation of severe accidents with reactor core melting. The core catcher concept incorporates a number of engineering solutions used in the catcher designs of European EPR and Russian WER-1000 reactors, such as thin-layer corium spreading for better cooling, retention of the melt in a water-cooled steel vessel, and use of sacrificial material (SM) to control the melt properties. SM is one of the key elements of the catcher design and its performance is critical for melt retention efficiency. This SM consists of oxide components, but the core catcher also includes sacrificial steel which reacts with the metal melt of the molten corium to reduce its temperature. The paper describes the required properties of SM. The melt retention capability of the core catcher can be confirmed by modeling the heat fluxes to the catcher vessel to show that it will not fail. The fulfillment of this requirement is demonstrated on the example of LBLOCA severe accident. Thermal and physicochemical interactions between the oxide and metal melts, interactions of the melts with SM, sacrificial steel and vessel, core catcher external cooling by water and release of non-condensable gases are modeled. (authors)

Granovsky, V. S.; Sulatsky, A. A.; Khabensky, V. B.; Sulatskaya, M. B. [Alexandrov Research Inst. of Technology NITI, Sosnovy Bor (Russian Federation); Gusarov, V. V.; Almyashev, V. I.; Komlev, A. A. [Saint Petersburg State Technological Univ. SPbSTU, St.Petersburg (Russian Federation); Bechta, S. [KTH, Stockholm (Sweden); Kim, Y. S. [KHNP, 1312 Gil 70, Yuseongdaero, Yuseong-gu, Daejeon (Korea, Republic of); Park, R. J.; Kim, H. Y.; Song, J. H. [KAERI, 989 Gil 111, Daedeokdaero, Yuseong-gu, Daejeon (Korea, Republic of)

2012-07-01

12

Core-melt materials interactions evaluations. Final report, April 1980April 1983  

Microsoft Academic Search

This final report describes work performed on a variety of topics related to the materials interactions that would occur following a postulated core-meltdown accident in a Light Water Reactor. The main topics addressed include: (1) an evaluation of candidate core-retention-system materials for the Zion and Indian Point (Z\\/IP) nuclear reactors; (2) an examination of various core-retention-system concepts with emphasis on

D. G. Swanson; J. N. Castle; P. D. Anderson; I. Catton

1983-01-01

13

Melting induced stratification above the Earth's inner core due to convective translation  

E-print Network

to the Earth's inner core: asymmetry between the eastern and west- ern hemispheres 2­6 and a layer of reducedMelting induced stratification above the Earth's inner core due to convective translation Thierry seismic velocity at the base of the outer core 6­12 . This 250 km thick layer has been interpreted

Boyer, Edmond

14

CORMLT modeling of severe fuel damage in postulated accidents  

SciTech Connect

Recently, the capabilities of the CORMLT code, which was designed to predict heatup, degradation, and meltdown of core and Reactor Pressure VEssel (RPV) internals during postulated severe accidents, were enhanced to enable tracking of individual fission product species during core meltdown. In addition, a mechanistic treatment of the release and flow of molten materials was developed to replace the engineering models developed earlier. In the present paper, the improved models are described and predictions of melt progression for a postullated accident sequence (TMLB') are discussed. A key issue in the new modeling is the mechanical behavior of fuel pellet stacks during run-off of molten cladding. One view is that capillary forces result in ''welding'' of porous fuel, thereby promoting free-standing pellet stacks; another is that rubblization and slumping of fuel take place. Results are reported for the first view point and its impact on the timings for core collapse into the bottom-head is addressed.

Denny, V.E.; Mertol, A.; Sehgal, B.R.

1987-01-01

15

Examination of offsite radiological emergency protective measures for nuclear reactor accidents involving core melt  

E-print Network

Evacuation, sheltering followed by population relocation, and iodine prophylaxis are evaluated as offsite public protective measures in response to nuclear reactor accidents involving core-melt. Evaluations were conducted ...

Aldrich, David C.

1979-01-01

16

Redistribution of Core-forming Melt During Shear Deformation of Partially Molten Peridotite  

NASA Technical Reports Server (NTRS)

To investigate the role of deformation on the distribution of core-forming melt in a partially molten peridotite, samples of olivine-basalt-iron sulfide were sheared to large strains. Dramatic redistribution of sulfide and silicate melts occur during deformation. Additional information is contained in the original extended abstract.

Hustoft, J. W.; Kohlstedt, D. L.

2002-01-01

17

Contribution of Anticipated Transients Without Scram (ATWS) to core melt at United States nuclear power plants  

SciTech Connect

This report looks at WASH-1400 and several other Probabilistic Risk Assessments (PRAs) and Probabilistic Safety Studies (PSSs) to determine the contribution of Anticipated Transients Without Scram (ATWS) events to the total core melt probability at eight nuclear power plants in the United States. After considering each plant individually, the results are compared from plant to plant to see if any generic conclusions regarding ATWS, or core melt in general, can be made. 8 refs., 34 tabs.

Giachetti, R.T. (Giachetti (Richard T.), Ann Arbor, MI (USA))

1989-09-01

18

A numerical and experimental study of water ingression phenomena in melt pool coolability  

Microsoft Academic Search

During a postulated severe accident, the core can melt and the melt can fail the reactor vessel. Subsequently, the molten corium can be relocated in the containment cavity forming a melt pool. The melt pool can be flooded with water at the top for quenching it. However, the question that arises is to what extent the water can ingress in

Arun Kumar Nayak; Raj Kumar Singh; Parimal P. Kulkarni; Bal Raj Sehgal

2009-01-01

19

INFLUENCE OF CORED WIRE MELTING MODE AT ARC SPRAYING ON COATING PROPERTIES  

Microsoft Academic Search

Jointly analysis of melting model of core wire at arc spraying and form- ing coating structure properties was done. Influence of physicochemical parameters of initial materials and atomization modes as well was established. Basing on investiga- tion results a row of core wires for wear-resistant application was developed. Coatings from such materials are successfully used with reference to parts to

Yu. Korobov; M. Filippov; V. Shymiakov; M. Shalimov

20

Melting of the Fe-O-S system and reaction between olivine and iron melt at the lunar core conditions: Implications for the structure of the lunar core  

NASA Astrophysics Data System (ADS)

Despite recent observations on the Moon from satellite sensing and analyses of Apollo-era seismic data, there are still several unsolved issues on the deep lunar interior. Recent studies suggest the presence of a solid inner core and liquid outer core in the Moon (1). If we could constrain the temperature and composition of the lunar outer core, this would help us to better understand the lunar interior. Here, we focused on the interaction between liquid iron-alloys and solid silicates, and revealed the nature of the core of the Moon. The lunar mantle is characterized by high FeO content (2). This implies that the Moon is more oxidizing compared to the Earth and thus the lunar core could be composed of Fe-O-S alloys. It is known that there is a liquid immiscibility in the Fe-O-S system, thus one of the aims of our study is to clarify whether the Moon has an immiscible liquid core or not. We performed oxygen partition experiments between the lunar silicate mantle and molten metal at 5 GPa and calculated the distribution coefficient, D, of oxygen between liquid metal and olivine crystals. Using this value, the amount of O in the lunar liquid core is calculated to be 4.45 at.% at 1000 °C and 5.56 at.% at 1400 °C when the mantle Mg number is 80, which is the assumed lunar core (2). This high amount of oxygen strongly indicates that the lunar core coexisting with the FeO-rich mantle is composed of the two immiscible liquids (FeO-rich melt and Fe-FeS melt). Estimations from the existing data on the density of FeO-rich melt and liquid Fe-FeS indicate that the liquid Fe-FeS is denser than the FeO-rich melt suggesting that the lunar liquid core is stratified to an upper FeO-rich layer and a lower Fe-FeS layer. The upper FeO-rich layer is reactive with the olivine rich lunar mantle to form magnesiowustite and could cause the partially molten low Q (high damping) region at the CMB of the Moon. (1) Weber, R.C., Lin. P., Garnero, E.J., Williams, Q., Lognonné, P., Science 331, 309-312, (2011) (2) Taylor, S.R., Solar system evolution, A new Perspective. Cambridge University Press, New York, 307 (1992)

Akamatsu, H.; Ohtani, E.; Suzuki, A.

2013-12-01

21

Crystallization of ion clouds in octupole traps: Structural transitions, core melting, and scaling laws  

SciTech Connect

The stable structures and melting properties of ion clouds in isotropic octupole traps are investigated using a combination of semianalytical and numerical models, with a particular emphasis at finite-size scaling effects. Small-size clouds are found to be hollow and arranged in shells corresponding approximately to the solutions of the Thomson problem. The shell structure is lost in clusters containing more than a few thousands of ions, the inner parts of the cloud becoming soft and amorphous. While melting is triggered in the core shells, the melting temperature follows the rule expected for three-dimensional dense particles, with a depression scaling linearly with the inverse radius.

Calvo, F.; Champenois, C.; Yurtsever, E. [LASIM, Universite Claude Bernard Lyon 1 and CNRS, UMR 5579, 43 Boulevard du 11 Novembre 1918, F69622 Villeurbanne Cedex (France); PIIM, UMR 6633, Universite de Provence and CNRS, Campus Universitaire de Saint-Jerome C21, F13397 Marseille Cedex 20 (France); Koc University, Rumelifeneriyolu, Sariyer, Istanbul 34450 (Turkey)

2009-12-15

22

Chemical Convention in the Lunar Core from Melting Experiments on the Ironsulfur System  

SciTech Connect

By reanalyzing Apollo lunar seismograms using array-processing methods, a recent study suggests that the Moon has a solid inner core and a fluid outer core, much like the Earth. The volume fraction of the lunar inner core is 38%, compared with 4% for the Earth. The pressure at the Moon's core-mantle boundary is 4.8 GPa, and that at the ICB is 5.2 GPa. The partially molten state of the lunar core provides constraints on the thermal and chemical states of the Moon: The temperature at the inner core boundary (ICB) corresponds to the liquidus of the outer core composition, and the mass fraction of the solid core allows us to infer the bulk composition of the core from an estimated thermal profile. Moreover, knowledge on the extent of core solidification can be used to evaluate the role of chemical convection in the origin of early lunar core dynamo. Sulfur is considered an antifreeze component in the lunar core. Here we investigate the melting behavior of the Fe-S system at the pressure conditions of the lunar core, using the multi-anvil apparatus and synchrotron and laboratory-based analytical methods. Our goal is to understand compositionally driven convection in the lunar core and assess its role in generating an internal magnetic field in the early history of the Moon.

Li, J.; Liu, J.; Chen, B.; Li, Z.; Wang, Y. (Michigan); (UC)

2012-03-26

23

Expert opinion and statistical evidence: an application to reactor core melt frequency  

Microsoft Academic Search

A model for the evaluation of probabilities of rare events by combining the available experience with expert opinion is developed, using the core melt frequency of nuclear power reactors as an example. A distribution for this frequency is assessed using the statistical evidence and including near misses. this distribution is subsequently modified, via Bayes' theorem, to include the estimate derived

G. Apostolakis; A. Mosleh

1979-01-01

24

Contribution of Anticipated Transients Without Scram (ATWS) to core melt at United States nuclear power plants  

Microsoft Academic Search

This report looks at WASH-1400 and several other Probabilistic Risk Assessments (PRAs) and Probabilistic Safety Studies (PSSs) to determine the contribution of Anticipated Transients Without Scram (ATWS) events to the total core melt probability at eight nuclear power plants in the United States. After considering each plant individually, the results are compared from plant to plant to see if any

Giachetti

1989-01-01

25

Melt spreading code assessment, modifications, and application to the EPR core catcher design.  

SciTech Connect

The Evolutionary Power Reactor (EPR) is under consideration by various utilities in the United States to provide base load electrical production, and as a result the design is undergoing a certification review by the U.S. Nuclear Regulatory Commission (NRC). The severe accident design philosophy for this reactor is based upon the fact that the projected power rating results in a narrow margin for in-vessel melt retention by external cooling of the reactor vessel. As a result, the design addresses ex-vessel core melt stabilization using a mitigation strategy that includes: (1) an external core melt retention system to temporarily hold core melt released from the vessel; (2) a layer of 'sacrificial' material that is admixed with the melt while in the core melt retention system; (3) a melt plug in the lower part of the retention system that, when failed, provides a pathway for the mixture to spread to a large core spreading chamber; and finally, (4) cooling and stabilization of the spread melt by controlled top and bottom flooding. The overall concept is illustrated in Figure 1.1. The melt spreading process relies heavily on inertial flow of a low-viscosity admixed melt to a segmented spreading chamber, and assumes that the melt mass will be distributed to a uniform height in the chamber. The spreading phenomenon thus needs to be modeled properly in order to adequately assess the EPR design. The MELTSPREAD code, developed at Argonne National Laboratory, can model segmented, and both uniform and nonuniform spreading. The NRC is thus utilizing MELTSPREAD to evaluate melt spreading in the EPR design. MELTSPREAD was originally developed to support resolution of the Mark I containment shell vulnerability issue. Following closure of this issue, development of MELTSPREAD ceased in the early 1990's, at which time the melt spreading database upon which the code had been validated was rather limited. In particular, the database that was utilized for initial validation consisted of: (1) comparison to an analytical solution for the dam break problem, (2) water spreading tests in a 1/10 linear scale model of the Mark I containment by Theofanous et al., and (3) steel spreading tests by Suzuki et al. that were also conducted in a geometry similar to the Mark I. The objective of this work was to utilize the MELTSPREAD code to check the assumption of uniform melt spreading in the EPR core catcher design. As a starting point for the project, the code was validated against the worldwide melt spreading database that emerged after the code was originally written in the very early 1990's. As part of this exercise, the code was extensively modified and upgraded to incorporate findings from these various analytical and experiment programs. In terms of expanding the ability of the code to analyze various melt simulant experiments, the options to input user-specified melt and/or substrate material properties was added. The ability to perform invisicid and/or adiabatic spreading analysis was also added so that comparisons with analytical solutions and isothermal spreading tests could be carried out. In terms of refining the capability to carry out reactor material melt spreading analyses, the code was upgraded with a new melt viscosity model; the capability was added to treat situations in which solid fraction buildup between the liquidus-solidus is non-linear; and finally, the ability to treat an interfacial heat transfer resistance between the melt and substrate was incorporated. This last set of changes substantially improved the predictive capability of the code in terms of addressing reactor material melt spreading tests. Aside from improvements and upgrades, a method was developed to fit the model to the various melt spreading tests in a manner that allowed uncertainties in the model predictions to be statistically characterized. With these results, a sensitivity study was performed to investigate the assumption of uniform spreading in the EPR core catcher that addressed parametric variations in: (1) melt pour mass, (2) melt composition, (3) me

Farmer, M. T .; Nuclear Engineering Division

2009-03-30

26

Is Core-Formation Enhanced by Deformation? Olivine-FeS Melt Experiments With the Deformation-DIA  

NASA Astrophysics Data System (ADS)

Contrary to most common silicate melt phases, a high dihedral angle (>60°) between metallic melt and silicate minerals leads to an early breakdown of the grain-scale melt network before complete melt extraction by porous flow can be achieved. This inefficient segregation from a solid matrix provides important support for the magma ocean model of core formation, which allows molten metal droplets to segregate from silicate melt by gravitational settling. However, some authors have demonstrated that deformation can dynamically enhance melt connectivity so that extensive melting of the silicate proto-earth may not have been necessary. In this study, deformation experiments with FeS melt in a matrix of synthetic olivine (Fo90) were performed to investigate a potentially enhanced dynamic melt segregation as a function of strain rate and melt fraction. The experiments were performed with a deformation-DIA, a cubic multi-anvil device, at a confining pressure of 3 GPa and at a temperature of 1400°C using a wide range of melt fractions (1-15 vol. %) and strain rates (10-2-10-6 s-1). The samples were quenched rapidly to preserve the dynamic melt geometry. Our results show that despite local wetting of grain boundaries, especially during high strain rate experiments, no interconnected melt networks were present at melt fractions below ~3 vol. %. Thus, melt migration by continuous porous flow should be inhibited. However, deformation has a significant effect on melt distribution. Compared to statically annealed samples, the amount of melt in large melt pockets (> 200 mm2) decreases, while the amount of melt in smaller pockets increases, i.e. deformation disperses melt more evenly throughout the grain matrix. At the same time, the overall melt fraction decreases to an apparently stable value of ~1.5 vol. %. Segregated melt can often be observed at the side of the capsule. Although no continuous melt pathways were observed in the low melt-fraction experiments, individual melt patches must have still been mobilized during deformation. Thus, although deformation can aid melt segregation to a certain extent, a decrease of melt-fraction below ~1.5 vol.% did not occur in our experiments so that deformation could not have been the sole mechanism for an efficient core formation.

Walte, N. P.; Frost, D. J.; Rubie, D. C.

2005-12-01

27

Influence of zircaloy oxidation and melting behavior on core behavior during a severe accident  

SciTech Connect

The influence of zircaloy oxidation and melting on core temperatures, hydrogen generation, and fission product release is examined. The uncertainties in phenomena important to the modeling of zircaloy oxidation and melting processes including zircaloy oxidation kinetics, hydrogen blanketing, UO/sub 2/-zircaloy interactions, and ZrO/sub 2/ failure are estimated. These uncertainties are then applied to a sensitivity study of a boiloff-initiated severe accident similar to that which may have occurred in TMI-2. Results indicate that the major uncertainties are in the oxidation kinetics which can contribute a factor of ten to the uncertainties in fission product release and can affect the timing of that release.

Allison, C.M.; Hagrman, D.L.; Berna, G.A.

1984-01-01

28

Anomalous Melting Scenario of the Two-Dimensional Core-Softened System  

NASA Astrophysics Data System (ADS)

We present a computer simulation study of the phase behavior of two-dimensional (2D) classical particles repelling each other through an isotropic core-softened potential. As in the analogous three-dimensional (3D) case, a reentrant-melting transition occurs upon compression for not too high pressures, along with a spectrum of waterlike anomalies in the fluid phase. However, in two dimensions in the low density part of the phase diagram melting is a continuous two-stage transition, with an intermediate hexatic phase. All available evidence supports the Kosterlitz-Thouless-Halperin-Nelson-Young scenario for this melting transition. On the other hand, at the high density part of the phase diagram one first-order transition takes place.

Dudalov, D. E.; Fomin, Yu. D.; Tsiok, E. N.; Ryzhov, V. N.

2014-04-01

29

The structure of melting mushy zones, with implications for Earth's inner core (Invited)  

NASA Astrophysics Data System (ADS)

Seismologists have inferred hemispherical differences in the isotropic wavespeed, the elastic anisotropy, the attenuation, and the attenuation anisotropy of Earth's inner core. One hypothesis for these hemispherical differences involves an east-west translation of the inner core, with enhanced solidification on one side and melting on the other. Another hypothesis is that long term mantle control over outer core convection can lead to hemispherical variations in solidification that could even result in melting in some regions of the inner core boundary. It has also been hypothesized that the inner core is growing dendritically, resulting in an inner core that has the structure of a mushy zone (albeit one with a high solid fraction). It would therefore be helpful to understand how the structure of a melting mushy zone might look in comparison with one that is solidifying, in an effort to help interpret the seismic inferences. We have carried out experiments on the solidification of ammonium chloride from an aqueous solution, yielding a mushy zone. The experiments run in a centrifuge, in order to reach a more realistic ratio of convective velocity to phase change rate, expected to be very large at the boundary of the inner core. Hypergravity thus increases the experimental solid fraction of the mush. So far the maximum gravity we have achieved is 200 g. A Peltier cell provides cooling at one end of the cell, and after the mushy zone has grown we turn on a heater at the other end. Probes monitor the temperature along the height of the cell. As ammonium chloride in the mushy zone melts it produces more dense fluid, which results in convection in the mushy zone, a greater ammonium chloride concentration deeper in the mushy zone, and hence enhanced solidification there. This thus changes the solid fraction profile from that during solidification, which may be observable in the lab experiments using ultrasonic transducers and post-mortem under a microscope. The melting may also change the propagation of chimney convection. It remains unclear whether these changes will be observable seismically.

Bergman, M. I.; Huguet, L.; Alboussiere, T.

2013-12-01

30

Melting of iron close to Earth's inner core boundary conditions and beyond  

E-print Network

Several important geophysical features such as heat flux at the Core-Mantle Boundary or geodynamo production are intimately related with the temperature profile in the Earth's core. However, measuring the melting curve of iron at conditions corresponding to the Earth inner core boundary under pressure of 330 GPa has eluded scientists for several decades. Significant discrepancies in previously reported iron melting temperatures at high pressure have called into question the validity of dynamic measurements. We report measurements made with a novel approach using X-ray absorption spectroscopy using an X-ray free electron laser source coupled to a laser shock experiment. We determine the state of iron along the shock Hugoniot up to 420 GPa (+/- 50) and 10800 K (+/- 1390) and find an upper boundary for the melting curve of iron by detecting solid iron at 130 GPa and molten at 260, 380 and 420 GPa along the shock Hugoniot. Our result establishes unambiguous agreement between dynamic measurement and recent extrapo...

Harmand, M; Mazevet, S; Bouchet, J; Denoeud, A; Dorchies, F; Feng, Y; Fourment, C; Galtier, E; Gaudin, J; Guyot, F; Kodama, R; Koenig, M; Lee, H J; Miyanishi, K; Morard, G; Musella, R; Nagler, B; Nakatsutsumi, M; Ozaki, N; Recoules, V; Toleikis, S; Vinci, T; Zastrau, U; Zhu, D; Benuzzi-Mounaix, A

2014-01-01

31

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

NASA Technical Reports Server (NTRS)

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

Holzheid, Astrid; Grove, Timothy L.

2002-01-01

32

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

NASA Technical Reports Server (NTRS)

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

Holzheid, Astrid; Grove, Timothy L.

2003-01-01

33

The role of partial melting and extensional strain rates in the development of metamorphic core complexes  

NASA Astrophysics Data System (ADS)

Orogenic collapse involves extension and thinning of thick and hot (partially molten) crust, leading to the formation of metamorphic core complexes (MCC) that are commonly cored by migmatite domes. Two-dimensional thermo-mechanical Ellipsis models evaluate the parameters that likely control the formation and evolution of MCC: the nature and geometry of the heterogeneity that localizes MCC, the presence/absence of a partially molten layer in the lower crust, and the rate of extension. When the localizing heterogeneity is a normal fault in the upper crust, the migmatite core remains in the footwall of the fault, resulting in an asymmetric MCC; if the localizing heterogeneity is point like region within the upper crust, the MCC remains symmetric throughout its development. Therefore, asymmetrically located migmatite domes likely reflect the dip of the original normal fault system that generated the MCC. Modeling of a severe viscosity drop owing to the presence of a partially molten layer, compared to a crust with no melt, demonstrates that the presence of melt slightly enhances upward advection of material and heat. Our experiments show that, when associated with boundary-driven extension, far-field horizontal extension provides space for the domes. Therefore, the buoyancy of migmatite cores contributes little to the outer envelope of metamorphic core complexes, although it may play a significant role in the internal dynamics of the partially molten layer. The presence of melt also favors heterogeneous bulk pure shear of the dome as opposed to the bulk simple shear, which dominates in melt-absent experiments. Melt presence affects the shape of P-T-t paths only slightly for material located near the top of the low-viscosity layer but leads to more complex flow paths for material inside the layer. The effect of extension rate is significant: at high extension rate (cm yr - 1 in the core complex region), partially molten crust crystallizes and cools along a high geothermal gradient (35 to 65 °C km - 1 ); material remains partially molten in the dome during ascent. At low strain rate (mm yr - 1 in the core complex region), the partially molten crust crystallizes at high pressure; this material is subsequently deformed in the solid-state along a cooler geothermal gradient (20 to 35 °C km - 1 ) during ascent. Therefore, the models predict distinct crystallization versus exhumation histories of migmatite cores as a function of extensional strain rates. The Shuswap metamorphic core complex (British Columbia, Canada) exemplifies a metamorphic core complex in which an asymmetric, detachment-controlled migmatite dome records rapid exhumation and cooling likely related to faster rates of extension. In contrast the Ruby Mountain-East Humboldt Ranges (Nevada, U.S.A.) exhibits characteristics associated with slower metamorphic core complexes.

Rey, P. F.; Teyssier, C.; Whitney, D. L.

2009-11-01

34

Heat Transfer Processes in Reactor Vessel Lower Plenum During Late Phase of In-Vessel Core Melt Progression  

Microsoft Academic Search

Late phase in-vessel core melt progression during the course of a hypothetical severe (melt-down) accident in a light water\\u000a reactor (LWR) is considered, with particular emphasis on thermal processes occurring in the lower plenum of the reactor pressure\\u000a vessel (RPV). The formation of a melt pool, from the initial state of a uniform composition, dried out, debris bed, is investigated.

B. R. Sehgal; V. A. Bui; T. N. Dinh; R. R. Nourgaliev

35

Chemical Convection in the Lunar Core from Melting Experiments on the Fe-Ni-S System  

NASA Astrophysics Data System (ADS)

The thermal and chemical states of the lunar interior are directly related to the origin and evolution of the Moon. Recent seismic study suggested the lunar core is partially molten, consisting of a liquid outer shell and a solid inner sphere (Weber et al., 2011). The volume fraction of the lunar inner core is 38%, which is much higher than that for the Earth (~ 4%). This volume fraction can be used to establish the relation between the bulk composition of the lunar core and its temperature profile if the liquidi of relevant compositions at lunar inner core boundary (ICB) pressure (~ 5.1 GPa) are known. Moreover, knowledge on the extent of core solidification can be used to evaluate the role of compositional convection in the origin of early lunar core dynamo (Stegman et al., 2003). We have conducted melting experiments at 5.1 GPa and 900-1600 °C for the Fe-rich portion of Fe-Ni-S system, using the multi-anvil apparatus and synchrotron and laboratory-based analytical methods. Our data show that in the iron-rich portion of the Fe-S binary system, the liquidus curve reflects nearly ideal mixing between iron and FeS end-members. In contrast, the liquidus curve of the Fe-Ni-S ternary contains two inflection points with a turning point at a sulfur content of 10 wt.%, resulting from a departure from ideal solution behavior. Given that the compositional buoyancy force scales with the slope of the liquidus curve at the ICB pressure and temperature, the contribution of compositional convection to sustain the early lunar dynamo can be estimated from our data: for a simplified model of Fe-S binary core, the role of chemical convection was probably negligible in the early history of the Moon and would have remained nearly constant since the inception of the inner core. The lunar core, however, likely contains nickel, the turning points in liquidus curve of the Fe-Ni-S ternary system may lead to dynamo initiation if the sulfur content of the bulk lunar core is less than 10 wt.% or cessation if the bulk lunar core contains more than 10 wt.% sulfur. References Stegman, D.R., Jellinek, A.M., Zatman, S.A., Baumgardner, J.R., and Richards, M.A. (2003) An early lunar core dynamo driven by thermochemical mantle convection. Nature, 421(6919), 143-146. Weber, R.C., Lin, P.Y., Garnero, E.J., Williams, Q., and Lognonne, P. (2011) Seismic Detection of the Lunar Core. Science, 331(6015), 309-312.

Liu, J.; Chen, B.; Wang, Y.; Jing, Z.; Li, Z.; Li, J.

2012-12-01

36

Diverse Melting Modes and Structural Collapse of Hollow Bimetallic Core-Shell Nanoparticles: A Perspective from Molecular Dynamics Simulations  

PubMed Central

Introducing hollow structures into metallic nanoparticles has become a promising route to improve their catalytic performances. A fundamental understanding of thermal stability of these novel nanostructures is of significance for their syntheses and applications. In this article, molecular dynamics simulations have been employed to offer insights into the thermodynamic evolution of hollow bimetallic core-shell nanoparticles. Our investigation reveals that for hollow Pt-core/Au-shell nanoparticle, premelting originates at the exterior surface, and a typical two-stage melting behavior is exhibited, similar to the solid ones. However, since the interior surface provides facilitation for the premelting initiating at the core, the two-stage melting is also observed in hollow Au-core/Pt-shell nanoparticle, remarkably different from the solid one. Furthermore, the collapse of hollow structure is accompanied with the overall melting of the hollow Pt-core/Au-shell nanoparticle while it occurs prior to that of the hollow Au-core/Pt-shell nanoparticle and leads to the formation of a liquid-core/solid-shell structure, although both of them finally transform into a mixing alloy with Au-dominated surface. Additionally, the existence of stacking faults in the hollow Pt-core/Au-shell nanoparticle distinctly lowers its melting point. This study could be of great importance to the design and development of novel nanocatalysts with both high activity and excellent stability. PMID:25394424

Huang, Rao; Shao, Gui-Fang; Zeng, Xiang-Ming; Wen, Yu-Hua

2014-01-01

37

Diverse melting modes and structural collapse of hollow bimetallic core-shell nanoparticles: a perspective from molecular dynamics simulations.  

PubMed

Introducing hollow structures into metallic nanoparticles has become a promising route to improve their catalytic performances. A fundamental understanding of thermal stability of these novel nanostructures is of significance for their syntheses and applications. In this article, molecular dynamics simulations have been employed to offer insights into the thermodynamic evolution of hollow bimetallic core-shell nanoparticles. Our investigation reveals that for hollow Pt-core/Au-shell nanoparticle, premelting originates at the exterior surface, and a typical two-stage melting behavior is exhibited, similar to the solid ones. However, since the interior surface provides facilitation for the premelting initiating at the core, the two-stage melting is also observed in hollow Au-core/Pt-shell nanoparticle, remarkably different from the solid one. Furthermore, the collapse of hollow structure is accompanied with the overall melting of the hollow Pt-core/Au-shell nanoparticle while it occurs prior to that of the hollow Au-core/Pt-shell nanoparticle and leads to the formation of a liquid-core/solid-shell structure, although both of them finally transform into a mixing alloy with Au-dominated surface. Additionally, the existence of stacking faults in the hollow Pt-core/Au-shell nanoparticle distinctly lowers its melting point. This study could be of great importance to the design and development of novel nanocatalysts with both high activity and excellent stability. PMID:25394424

Huang, Rao; Shao, Gui-Fang; Zeng, Xiang-Ming; Wen, Yu-Hua

2014-01-01

38

Phase relations, melting and thermoelastic properties in FeS: Application to the Martian core  

NASA Astrophysics Data System (ADS)

The phase stability and equations of state of the NiAs superstructured FeS IV phase and the high-temperature NiAs structured FeS V phase (space group P63/mmc) have implications for the structure and dynamics of planetary cores, such as that of Mars. The FeS VI phase (space group Pnma) is stable to the conditions of the deep Earth, and has implications specifically for the Earth's liquid outer core, including the nature of the light-element component required to match the density deficit relative to pure Fe in the core. A suite of high-pressure, high-temperature X-ray diffraction data were collected on stoichiometric FeS at pressures and temperature conditions of terrestrial planetary interiors using a laser-heated diamond anvil cell. Experiments were performed at beamline 13-ID-D (GSECARS) at the Advanced Photon Source. We refined the high-temperature, high-pressure phase boundaries of the FeS IV, FeS V and FeS VI polymorphs, and also established their thermal equations of state. The phase transition from FeS IV to FeS V is indicated by the disappearance of some or all of the following FeS IV reflections: 110, 210, 112, 211, 300, 302, 303. Fixing K?0 at 4 and q at 1, we find V0 = 16.4 cc mol-1 and 16.9 cc mol-1, K0T = 98.7 GPa and 91.6 GPa, and ?0 = 2.15 and 1.47 for the FeS IV and FeS V phases, respectively. Using a combination of static compression measurements in Ne and high-temperature PVT measurements, our data suggest a higher FeS VI transition pressure than previous studies. Comparing our results to the Martian core, we find that the stable phase at the core-mantle boundary is FeS IV, with a possible transition to FeS V occurring deeper in the Martian core, while the stability field of FeS VI exceeds PT conditions of the Martian core. At approximately 40 GPa, we observe melting of FeS V consistent with the melting curve of Boehler (1992).

Reaman, D. M.; Campbell, A. J.; Fischer, R. A.; Heinz, D. L.; Prakapenka, V.

2012-12-01

39

Nickel and helium evidence for melt above the core-mantle boundary.  

PubMed

High (3)He/(4)He ratios in some basalts have generally been interpreted as originating in an incompletely degassed lower-mantle source. This helium source may have been isolated at the core-mantle boundary region since Earth's accretion. Alternatively, it may have taken part in whole-mantle convection and crust production over the age of the Earth; if so, it is now either a primitive refugium at the core-mantle boundary or is distributed throughout the lower mantle. Here we constrain the problem using lavas from Baffin Island, West Greenland, the Ontong Java Plateau, Isla Gorgona and Fernandina (Galapagos). Olivine phenocryst compositions show that these lavas originated from a peridotite source that was about 20 per cent higher in nickel content than in the modern mid-ocean-ridge basalt source. Where data are available, these lavas also have high (3)He/(4)He. We propose that a less-degassed nickel-rich source formed by core-mantle interaction during the crystallization of a melt-rich layer or basal magma ocean, and that this source continues to be sampled by mantle plumes. The spatial distribution of this source may be constrained by nickel partitioning experiments at the pressures of the core-mantle boundary. PMID:23302797

Herzberg, Claude; Asimow, Paul D; Ionov, Dmitri A; Vidito, Chris; Jackson, Matthew G; Geist, Dennis

2013-01-17

40

In-situ rock melting applied to lunar base construction and for exploration drilling and coring on the moon  

SciTech Connect

An excavation technology based upon melting of rock and soil has been extensively developed at the prototype hardware and conceptual design levels for terrestrial conditions. Laboratory and field tests of rock-melting penetration have conclusively indicated that this excavation method is insensitive to rock, soil types, and conditions. Especially significant is the ability to form in-place glass linings or casings on the walls of boreholes, tunnels, and shafts. These factors indicate the unique potential for in situ construction of primary lunar base facilities. Drilling and coring equipment for resource exploration on the moon can also be devised that are largely automated and remotely operated. It is also very likely that lunar melt-glasses will have changed mechanical properties when formed in anhydrous and hard vacuum conditions. Rock melting experiments and prototype hardware designs for lunar rock-melting excavation applications are suggested.

Rowley, J.C.; Neudecker, J.W.

1984-01-01

41

Partitioning of Moderately Siderophile Elements Among Olivine, Silicate Melt, and Sulfide Melt: Constraints on Core Formation in the Earth and Mars  

NASA Technical Reports Server (NTRS)

This study investigates the effects of Variations in the fugacities of oxygen and sulfur on the partitioning of first series transition metals (V, Cr, Mn, Fe, Co, Ni. and Cu) and W among coexisting sulfide melt, silicate melt, and olivine. Experiments were performed at 1 atm pressure, 1350 C, with the fugacities of oxygen and sulfur controlled by mixing CO2, CO, and SO2 gases. Starting compositions consisted of a CaO-MgO-Al2O3-SiO2-FeO-Na2O analog for a barred olivine chondrule from an ordinary chondrite and a synthetic komatiite. The f(sub O2)/f(sub S2), conditions ranged from log of f(sub O2) = -7.9 to - 10.6, with log of f(sub S2) values ranging from - 1.0 to -2.5. Our experimental results demonstrate that the f(sub O2)/f(sub S2) dependencies of sulfide melt/silicate melt partition coefficients for the first series transition metals arc proportional to their valence states. The f(sub O2)/f(sub S2) dependencies for the partitioning of Fe, Co, Ni, and Cu are weaker than predicted on the basis of their valence states. Variations in conditions have no significant effect on olivine/melt partitioning other than those resulting from f(sub O2)-induced changes in the valence state of a given element. The strong f(sub O2)/f(sub S2) dependence for the olivine/silicate melt partitioning of V is attributable to a change of valence state, from 4+ to 3+, with decreasing f(sub O2). Our experimentally determined partition coefficients are used to develop models for the segregation of sulfide and metal from the silicate portion of the early Earth and the Shergottite parent body (Mars). We find that the influence of S is not sufficient to explain the overabundance of siderophile and chalcophile elements that remained in the mantle of the Earth following core formation. Important constraints on core formation in Mars are provided by our experimental determination of the partitioning of Cu between silicate and sulfide melts. When combined with existing estimates for siderophile element abundances in the Martian mantle and a mass balance constraint from Fe, the experiments allow a determination of the mass of the Martian core (approx. 17 to 22 wt% of the planet) and its S content (approx.0.4 wt%). These modeling results indicate that Mars is depleted in S, and that its core is solid.

Gaetani, Glenn A.; Grove, Timothy L.

1997-01-01

42

Melting curve of the deep mantle applied to properties of early magma ocean and actual core-mantle boundary  

NASA Astrophysics Data System (ADS)

Our planet experienced partial melting early in its history as a consequence of energy release due to accretion. Partial mantle melting could still happen today in the lowermost mantle. Occurrence of melting is primordial for the chemical segregation between the different Earth's reservoirs and for the dynamics of the whole planet. Melting of iron-alloys is relatively easy to achieve, but the silicated mantle happens to be more refractory. We investigated experimentally melting properties of two starting material, forsterite and chondritic-mantle, at pressures ranging from 25 to 140 GPa, using laser-heated diamond anvil cell coupled with synchrotron radiation. We show that partial melting in the lowermost mantle, as suggested by seismology on the basis of the ultra-low velocity zones (ULVZ), requires temperatures above 4200 K at the core-mantle boundary. At low pressures, our curve plots significantly lower than previous reports. Compared to recent estimates of mantle geotherm, while this temperature remains possible if the Earth's core is very hot, it is more likely that ULVZs correspond to high concentration of incompatible elements driven down to the D"-layer by subducting slabs or extracted out from the outer core. When our chondritic melting curve is coupled with recent isentropic temperature profiles for a magma ocean, we obtain a correlation between magma ocean depth and the potential temperature (Tp) at its surface; an ocean depth of 1000 km (equivalent to ~40 GPa) corresponds to Tp=2000 K, which happens to be significantly hotter than the estimated surface temperature of a sustained magma ocean. It emphasizes the importance of a lid at the magma ocean surface at an epoch as early as that of core-mantle segregation.

Andrault, Denis; Lo Nigro, Giacomo; Bolfan-Casanova, Nathalie; Bouhifd, Mohamed A.; Garbarino, Gaston; Mezouar, Mohamed

2010-05-01

43

Metal/Silicate Partitioning, Melt Speciation, Accretion, and Core Formation in the Earth  

NASA Astrophysics Data System (ADS)

Core formation in terrestrial planets was concomitant with accretion. Siderophile and chalcophile element signatures in the mantles of planets are the result of these processes. For Earth, abundances of most siderophile and chalcophile elements are elevated relative to predictions from simple metal/silicate equilibria at low pressures [1]. This observation has led to three hypotheses for how these abundances were established: heterogeneous accretion [2], inefficient core formation [3], and metal/silicate equilibria at magma ocean pressures and temperatures [4]. Knowledge of speciation of siderophile elements in silicate melts in equilibrium with metal may help distinguish between these hypotheses. But there is some uncertainty regarding speciation. For example, Ni and Co have been reported to be present as 1+ or zero valence species in silicate melts at redox states appropriate to planetary accretion, rather than the expected 2+ state [5-7]. Independent metal/silicate partitioning experiments by three members of this group using two different experimental designs on both synthetic and natural compositions do not show evidence for Ni and Co in valence states other than 2+ over a wide range of redox states. For example, solid metal/silicate melt partition coefficients for Ni at 1260 degrees C obtained by VJH from experiments investigating the partitioning of Ni, Co, Mo, W, and P are indistinguishable from those obtained by JAD in similar experiments investigating the partitioning of Ni, Ge, and Sn. Both datasets define a line with the equation: log D(Ni) = - 0.54log fO2 - 3.14 with r^2 > 0.995. (Note that fO2 was calculated in both studies from thermodynamic data and phase compositions. A small, systematic offset from the true fO2 as measured by a solid electrolyte cell affects both equations similarly, but does not diminish their close agreement.) The valence of Ni in the silicate melt is obtained by multiplying the slope of the line by -4, indicating divalent Ni in both studies. Experiments by [8] between 1300 degrees C and 1550 degrees C and fO2 from air to just below iron-wustite in which Ni and Co are partitioned between Pt metal and CaO-Al2O3-SiO2 silicate melt also show evidence only for 2+ valence. Capobianco et al. [1] have noted that reliable extrapolation from current laboratory temperatures (1190 degrees C-1600 degrees C) to magma ocean temperatures is not possible. The hypothesis that siderophile and chalcophile element abundances in the mantle of Earth were established by metal/silicate equilibria at magma ocean pressures and temperatures needs to be tested using direct experimental measurements at magma ocean temperatures and pressures. Such experiments are currently being conducted. References: [1] Capobianco et al. (1993) J. Geophys. Res., 98, 5433. [2] Wanke (1981) Phil. Trans. R. Soc. London, A303, 287. [3] Jones and Drake (1986) Nature, 322, 221. [4] Murthy (1991) Science, 253, 303. [5] Schmitt et al. (1989) GCA, 53, 173. [6] Ehlers et al. (1993) GCA, 56, 3733. [7] Colson (1992) Nature, 357, 65. [8] Capobianco and Amelin (1993) GCA, 56 (in press).

Drake, M. J.; Hillgren, V. J.; Dearo, J. A.; Capobianco, C. J.

1993-07-01

44

Melting behavior of the iron-sulfur system and chemical convection in iron-rich planetary cores  

SciTech Connect

We present experimental data on the high-pressure melting behavior of the Fe-S system from a synchrotron x-ray radiography study using the large volume press, with implications for the role of chemical convection in sulfur-bearing planetary cores. At present, Earth, Mercury and Ganymede are the only three solid bodies in the Solar System that possess intrinsic global magnetic fields. Dynamo simulation reveal that chemical buoyancy force associated with the formation of a solid inner core is critical for sustaining the Earth's magnetic field. Fluid motions in Mercury and Ganymede may be partially driven by chemical buoyancy force as well. The style of chemical convection and its influence on the thermal and chemical state and evolution of iron-rich cores are determined in part by the melting behavior of potential core-forming materials. Sulfur is widely accepted as a candidate light element in iron-rich planetary cores. In order to understand the role of chemical convection in sulfur-bearing cores, we studied the high-pressure melting behavior of Fe-S mixtures containing 9 wt% sulfur using the synchrotron x-ray radiographic method in a large volume press.

Li, J.; Chen, B. (UIUC)

2009-03-26

45

Melting Scenario of the Two-Dimensional Core-Softened System: First-Order or Continuous Transition?  

NASA Astrophysics Data System (ADS)

We present a computer simulation study of the phase behavior of two-dimensional classical particles repelling each other through an isotropic core-softened potential. As in the analogous three dimensional case, a reentrant-melting transition occurs upon compression for not too high pressures. However, in two dimensions in the low density part of the phase diagram melting is a continuous two-stage transition, with an intermediate hexatic phase. All available evidence supports the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) scenario for this melting transition. On the other hand, at high density part of the phase diagram one first-order transition takes place. We expect that such a phenomenology can be checked in confined monolayers of charge-stabilized colloids with a softened core and water confined between two hydrophobic plates.

Dudalov, D. E.; Fomin, Yu D.; Tsiok, E. N.; Ryzhov, V. N.

2014-05-01

46

Stability and melting of Fe3C at high pressure and temperature: Implication for the carbon in the Earth's core  

NASA Astrophysics Data System (ADS)

The Earth's core is regarded as an Fe-Ni alloy but its density is lower than that of pure Fe at the core conditions. Therefore, the Earth's core is supposed to contain light elements and carbon is one of the candidates of the light elements to explain the density deficit of the Earth's core. Nakajima et al. (2009) reported the melting temperature of Fe3C up to around 30 GPa based on textual observations, the chemical analysis of the quenched run products and in situ X-ray diffraction experiments using a Kawai-type multi anvil apparatus. Lord et al. (2009) reported melting temperatures of Fe3C up to 70 GPa, which was determined by the temperature plateau during increasing laser power using a laser-heated diamond anvil cell. They also suggested Fe+Fe7C3 is a stable subsolidus phase. There are obvious discrepancies between the melting curve and the stable subsolidus phase reported by Nakajima et al. (2009) and those reported by Lord et al. (2009). In this study, the melting temperatures of Fe3C and a subsolidus phase relation were determined based on in situ X-ray diffraction experiments. This study aims to reveal the stability field of Fe3C and the melting temperature of Fe3C and to discuss the behaviors of carbon in the Earth's core. We have performed experiments using a laser-heated diamond anvil cell combined with in situ X-ray diffraction experiment at BL10XU beamline, SPring-8 synchrotron facility. An NaCl powder and a rhenium or tungsten foil were used for the insulator and gasket, respectively. Melting of the sample was determined by disappearance of the X-ray diffraction peaks. We determined the melting relation of Fe3C up to 145 GPa by in situ X-ray diffraction experiments. Present results are close to Nakajima et al. (2009) up to 30 GPa but become close to that reported by Lord et al. (2009) at higher pressure conditions. The solidus temperature extrapolated to the ICB pressure, 330 GPa, is 5400 K. We also confirmed that Fe3C is stable as a subsolidus phase at least up to 237 GPa and 4100 K. This strongly suggests that Fe3C is a potential candidate of the Earth's inner core although we need further studies at the inner core conditions.

Takahashi, S.; Ohtani, E.; Sakai, T.; Hirao, N.; Ohishi, Y.

2012-12-01

47

A concept of a small controlled, filtered venting system and an add-on decay heat removal system to mitigate the consequences of core-melt accidents  

Microsoft Academic Search

Core-melt accidents as modeled in risk studies result in severe consequences to the environment of a nuclear power plant, only if the containment function of the plant is assumed to fail during the accident. To protect the containment function of a pressurized water reactor with double containment during a core-melt accident against the dominant late failure modes, a relief condenser

S. Chakraborty; B. Covelli; P. M. Herttrich

1986-01-01

48

Uranium partitioning between liquid iron and silicate melt at high pressures: implications for uranium solubility in planetary cores  

E-print Network

We have investigated the partitioning of U between silicate melt and Fe liquid at pressures of 3.0 to14.5 GPa and temperatures of 1660 to 2500 oC. The solubility of U in liquid Fe is in the range of 0.6 to 800 ppm and increases with temperature (T) and pressure (P). When P = or > 7 GPa and T > Tmelt of the silicate phase (olivine), the U concentration in Fe is 3 to 5 times greater than for run products where T Tmelt of the silicate phase), then > 2.4 ppb U could have entered the core. Alternatively, if a core with same composition formed by percolation (T Uranium; partition coefficients; high pressure; dynamos; planetary cores; heat sources, LA-ICP-MS.

Xuezhao Bao; Richard A. Secco; Joel E. Gagnon; Brian J. Fryer

2006-06-29

49

QUANTUM MECHANICS WITHOUT STATISTICAL POSTULATES  

SciTech Connect

The Bohmian formulation of quantum mechanics describes the measurement process in an intuitive way without a reduction postulate. Due to the chaotic motion of the hidden classical particle all statistical features of quantum mechanics during a sequence of repeated measurements can be derived in the framework of a deterministic single system theory.

G. GEIGER; ET AL

2000-11-01

50

Rapid Detection of KIT Mutations in Core-Binding Factor Acute Myeloid Leukemia Using High-Resolution Melting Analysis  

PubMed Central

The most frequent KIT mutations reported in core-binding factor acute myeloid leukemia are point mutations and insertions/deletions in exons 17 and 8. The vast majority of KIT mutation detection procedures are time-consuming, costly, or with a high lower limit of detection. High-resolution melting (HRM) is a gene scanning method that combines simplicity and rapid identification of genetic variants. We describe an HRM method for the simultaneous screening of exons 8 and 17 KIT mutations and report the results obtained in 69 core-binding factor acute myeloid leukemia patients. Mutation detection was compared with sequencing as the gold standard. The HRM method used high-resolution melting master reagents (Roche) and the LightCycler 480 (Roche) platform. HRM was reproducible, showed a lower limit of detection of 1%, and discriminated all patients with mutated KIT from controls without false positive or false negative results. Additionally, most of the mutations were differentiated from the other mutations. KIT mutations were present in 15.9% of patients, showing a higher incidence in inv(16) (25.8%) than in t(8;21) (7.9%). The presence of a KIT mutation was associated with a high white blood cell count, and adult patients with an exon 17 mutation had a higher incidence of relapse. These findings verify that HRM is a reliable, rapid, and sensitive method for KIT mutation screening. Furthermore, our study corroborates the unfavorable prognosis associated with exon 17 KIT mutations. PMID:19644024

Fuster, Óscar; Barragán, Eva; Bolufer, Pascual; Cervera, José; Larráyoz, Maria José; Jiménez-Velasco, Antonio; Martínez-López, Joaquín; Valencia, Ana; Moscardó, Federico; Sanz, Miguel Ángel

2009-01-01

51

Accident analyses and passive measures reducing the consequences of a core-melt in CAPRA\\/CADRA reactor cores  

Microsoft Academic Search

As part of the Combustion Améliorée du Plutonium dans les Réacteurs Avancés\\/Consommation D'Actinides et de Déchets dans les Réacteurs Avancés (CAPRA\\/CADRA) program the feasibility of reactor systems with different neutron spectra and coolants is investigated to burn plutonium and also to destruct minor actinides and long lived fission products. In this paper, we deal with reactor cores with fast spectrum

W Maschek; D Struwe

2000-01-01

52

LWR source terms for loss-of-coolant and core melt accidents  

SciTech Connect

Fission product source terms for loss-of-coolant and core meltdown accidents in light water reactors are reviewed. The results presented in the Reactor Safety Study are summarized, and modifications of these results, due to more recent experimental studies, are described.

Malinauskas, A.P.; Lorenz, R.A.; Albrecht, H.; Wild, H.

1980-01-01

53

Silicate glasses and sulfide melts in the ICDP-USGS Eyreville B core, Chesapeake Bay impact structure, Virginia, USA  

USGS Publications Warehouse

Optical and electron-beam petrography of melt-rich suevite and melt-rock clasts from selected samples from the Eyreville B core, Chesapeake Bay impact structure, reveal a variety of silicate glasses and coexisting sulfur-rich melts, now quenched to various sulfi de minerals (??iron). The glasses show a wide variety of textures, fl ow banding, compositions, devitrifi cation, and hydration states. Electron-microprobe analyses yield a compositional range of glasses from high SiO2 (>90 wt%) through a range of lower SiO2 (55-75 wt%) with no relationship to depth of sample. Some samples show spherical globules of different composition with sharp menisci, suggesting immiscibility at the time of quenching. Isotropic globules of higher interfacial tension glass (64 wt% SiO2) are in sharp contact with lower-surface-tension, high-silica glass (95 wt% SiO2). Immiscible glass-pair composition relationships show that the immiscibility is not stable and probably represents incomplete mixing. Devitrifi cation varies and some low-silica, high-iron glasses appear to have formed Fe-rich smectite; other glass compositions have formed rapid quench textures of corundum, orthopyroxene, clinopyroxene, magnetite, K-feldspar, plagioclase, chrome-spinel, and hercynite. Hydration (H2O by difference) varies from ~10 wt% to essentially anhydrous; high-SiO2 glasses tend to contain less H2O. Petrographic relationships show decomposition of pyrite and melting of pyrrhotite through the transformation series; pyrite? pyrrhotite? troilite??? iron. Spheres (~1 to ~50 ??m) of quenched immiscible sulfi de melt in silicate glass show a range of compositions and include phases such as pentlandite, chalcopyrite, Ni-As, monosulfi de solid solution, troilite, and rare Ni-Fe. Other sulfi de spheres contain small blebs of pure iron and exhibit a continuum with increasing iron content to spheres that consist of pure iron with small, remnant blebs of Fe-sulfi de. The Ni-rich sulfi de phases can be explained by melting and/or concentrating targetderived Ni without requiring an asteroid impactor source component. The presence of locally unaltered glasses in these rocks suggests that in some rock volumes, isolation from postimpact hydrothermal systems was suffi cient for glass preservation. Pressure and temperature indicators suggest that, on a thin-section scale, the suevites record rapid mixing and accumulation of particles that sustained widely different peak temperatures, from clasts that never exceeded 300 ?? 50 ??C, to the bulk of the glasses where melted sulfi de and unmelted monazite suggest temperatures of 1500 ?? 200 ??C. The presence of coesite in some glass-bearing samples suggests that pressures exceeded ~3 GPa. ?? 2009 Geological Society of America.

Belkin, H.E.; Horton, J.W., Jr.

2009-01-01

54

Melting curve of the deep mantle applied to properties of early magma ocean and actual core-mantle boundary  

Microsoft Academic Search

Our planet experienced partial melting early in its history as a consequence of energy release due to accretion. Partial mantle melting could still happen today in the lowermost mantle. Occurrence of melting is primordial for the chemical segregation between the different Earth's reservoirs and for the dynamics of the whole planet. Melting of iron-alloys is relatively easy to achieve, but

Denis Andrault; Giacomo Lo Nigro; Nathalie Bolfan-Casanova; Mohamed A. Bouhifd; Gaston Garbarino; Mohamed Mezouar

2010-01-01

55

Using the PC software PCTRAN for IPE core-melt sequence analysis at TMI-1  

SciTech Connect

In preparing for the individual plant examination (IPE) of Three Mile Island Unit I (TMI-1), two events that contribute significantly to the level-I core damage risk are station black- out (SBO) and steam generator tube rupture (SGTR). For an SBO, it is assumed that both the off-site power and on-site diesel generators fail to supply alternating-current power for the plant systems. Timing to core uncovery is important because either the off-site or on-site power may be recovered during the course of the event. For an SGTR, proper operator action may mitigate the consequences and prevent core damage. Traditional system transient analysis codes are not practical to conduct transient prediction of these events because of their long running time and the large number of cases to be analyzed. The personal computer-based plant analyzer code PCTRAN was used because of its simplicity and fast turn-around time. The code and the Babcock and Wilcox-designed pressurized water reactor plant, model have been previously verified against real plant data. With the exception of the large-break loss-of-coolant accident, for which the sudden momentum effect is not accounted for by the simple mass and energy balance equations, PCTRAN can generally reproduce operational transients and slowly varying accidents with reasonable accuracy in a faster-than-real-time mode.

Cliff Po, Li-Chi (GPU Nuclear Corp., Parsippany, NJ (United States))

1993-01-01

56

A Simple Lab Exercise Demonstrating Koch's Postulates.  

ERIC Educational Resources Information Center

Describes a laboratory exercise which applies Koch's Postulates to a plant disease, bacterial speck. Includes an explanation of Koch's Postulate, list of equipment needed, advance preparation, outline of the three-week activity, and variations of the laboratory exercise. (DS)

Fulton, Michael M.

1981-01-01

57

Petrology of impactites from El'gygytgyn crater: Breccias in ICDP-drill core 1C, glassy impact melt rocks and spherules  

E-print Network

Petrology of impactites from El'gygytgyn crater: Breccias in ICDP-drill core 1C, glassy impact melt intercalations of polymict breccia and mafic inclusions. These lithologies are overlain by 89 m of polymict breccia whose components occasionally exhibit scarce, low-degree shock metamorphic features. This unit

Claeys, Philippe

58

Melting relationships of the Fe-S-Si system up to 60 GPa: Implications for the thermal structure of the Earth's core  

NASA Astrophysics Data System (ADS)

The Earth's core is mainly composed of iron alloy, however the lighter elements are required in the core to account for the core density deficit (Birch, 1964). The potential light elements have been considered to be S, Si, O, C, and H (Poirier, 1994). Alloying light elements significantly affects the physical properties of iron and depresses its melting temperature(e.g., Boehler, 1996b). Sulfur and silicon are considered as major light element components based on cosmochemical study (McDonough, 2003) and high pressure partitioning experiments (e.g., Sakai et al., 2006), therefore the melting relationship of the Fe-S-Si system is the key information to clarify the thermal and compositional structure of the Earth's core. Many melting experiments of Fe-light elements alloys have been performed under high pressure corresponding Earth's core using diamond anvil cell. However in the case of the Fe-S-Si ternary system, there are no experimental data at high pressure and the phase and melting relations have not been clarified in detail under core conditions. In this study, the phase relationships and the solidus temperature of the Fe-S-Si system were determined up to 60 GPa using a laser-heated diamond anvil cell combined with in situ X-ray diffraction technique. The sample composition used for this study were Fe80.1S12.7Si7.2(Fe-8wt.%S-4wt.%Si) and Fe74.4S18.5Si7.1(Fe-12wt.%S-4wt.%Si), which are in the range of the amounts of the light elements to explain the density deficit in the Earth's core (Chen et al., 2007). In situ X-ray diffraction experiments were conducted at the BL10XU beamline at the SPring-8 facility (Ohishi et al., 2008). On the basis of diffraction patterns, Fe(hcp/fcc) which contains silicon and Fe3S are stable phases under subsolidus conditions. First Fe3S phase melts at the solidus temperature, and Fe-Si alloy coexists with partial melts above the eutectic temperature in this system. This melting sequence is consistent with the study of the Fe-Fe3S system observed earlier by Kamada et al. (2010). The solidus temperature is significantly lower than the melting temperature of pure Fe (Ma et al., 2004) and close to the eutectic point of the Fe-Fe3S system (Morard et al., 2008), suggesting that the effect of 7.2 at.% silicon on the eutectic temperature in the Fe-Fe3S system is minor. In order to draw the solidus curve as a function of pressure, we fitted the present results using the Simon's law. The obtained fitting parameters are a=104(16) and c=0.88(1). Based on our results of the melting relationship, the temperature at the core-mantle boundary should be greater than 2900(200) K and the temperature at the boundary of the inner and outer cores is estimated to be 5680(350) K, assuming that sulfur and silicon are the light elements in the Earth's core. The results in this study provide important constraints on the thermal structure of the Earth's core.

Sakairi, T.; Ohtani, E.; Sakai, T.; Kamada, S.; Miyahara, M.; Hirao, N.; Ohishi, Y.

2012-12-01

59

Transcrystalline Migration of Metallic Melt in (Mg,Fe)O: Implications for the Core-Mantle Interaction  

NASA Astrophysics Data System (ADS)

Penetration of metallic materials has been invoked at the core-mantle-boundary to explain relatively strong magnetic coupling and some geochemical signature of core materials. However, all previously proposed models fail to explain an extensive penetration (10s of km) required to explain these phenomena. We report a discovery of a new process of metallic melt entrainment into the mantle minerals that might provide a clue to explain inferred extensive core-mantle chemical interaction. When a mineral and molten metal co-exist at a large scale, the chemical equilibrium is attained only near the interface and the bulk of the system is out of equilibrium. Under these conditions, the gradient in chemical potential exists and the interface between these two phases becomes unstable against some morphological perturbation and one phase may penetrate into another. We found that such a process occurs between (Mg,Fe)O single crystal and molten metals (Mo-rich and Fe-rich metals). When such a system is annealed, morphological instability occurred and the interface became serrated. The serrated region grew and pinched off to become an isolated metal-rich blob. These blobs migrate into a crystal with the speed much faster than expected by diffusion-controlled processes. For example, after annealing at P=15 GPa, T=2000 K for 2 hours, a whole ~1 mm size (Mg,Fe)O was penetrated by metallic blobs. The morphological instability of such an interface was explained by a theory of Mullins and Sekerka (1963, 1964). On the bases of their theory, we developed a model to explain the evolution of a metal-rich layer. In this model, the compositions of both migrating metallic blobs and surrounding mineral will change as a metallic blob migrates, and the migration will terminate when the composition becomes the equilibrium composition. Our model predicts that such a metal-rich layer could extend 10s of km at the core-mantle boundary but the nature of such a layer depends on the properties of mantle minerals and will differ among different planets with different mineralogy.

Otsuka, K.; Karato, S.

2012-04-01

60

Stability and melting relations of Fe3C up to 3 Mbar: Implication for the carbon in the Earth's inner core  

NASA Astrophysics Data System (ADS)

The Earth's core is regarded as an Fe-Ni alloy but its density is lower than that of pure Fe at the core conditions. Therefore, the Earth's core is supposed to contain light elements and carbon is one of the candidates of the light elements to explain the density deficit of the Earth's core. Nakajima et al. (2009) reported the melting temperature of Fe3C up to around 30 GPa based on textual observations, the chemical analysis of the quenched run products and in situ X-ray diffraction experiments using a Kawai-type multi anvil apparatus. Lord et al. (2009) reported melting temperatures of Fe3C up to 70 GPa, which was determined by the temperature plateau during increasing laser power using a laser-heated diamond anvil cell. They also suggested Fe+Fe7C3 is a stable subsolidus phase. There are obvious discrepancies between the melting curve and the stable subsolidus phase reported by Nakajima et al. (2009) and those reported by Lord et al. (2009). In this study, the melting temperatures of Fe3C and a subsolidus phase relation were determined based on in situ X-ray diffraction experiments and observations of the recovered sample. This study aims to reveal the stability field of Fe3C and the melting temperature of Fe3C and to discuss the behaviors of carbon in the Earth's core. We have performed experiments using a laser-heated diamond anvil cell combined with in situ X-ray diffraction experiment at BL10XU beamline, SPring-8 synchrotron facility. We also conducted quench experiments for observation of the recovered sample at Tohoku University. Synthesized Fe3C or Fe+Fe3C (C = 5.2 wt.%) were sandwiched by NaCl or SiO2 glass layers, which were used as the thermal insulator and the pressure medium. Melting of the sample was determined by disappearance of the X-ray diffraction peaks and textual observations. We determined the melting relation of Fe3C up to 200 GPa by in situ X-ray diffraction experiments and textual observations of recovered samples. The melting temperature extrapolated to the ICB pressure, 330 GPa, is 5100 K. We also confirmed that Fe3C is stable as a subsolidus phase at least up to 340 GPa. This strongly suggests that Fe3C is a potential candidate of the Earth's inner core although we need further studies at the inner core conditions. However, if the core has a carbon-rich composition and the inner core crystalized by cooling of the outer core from above 5100 K, the inner core is indicated to be composed of Fe7C3, initially.

Takahashi, S.; Ohtani, E.; Sakai, T.; Mashino, I.; Kamada, S.; Miyahara, M.; Sakamaki, T.; Hirao, N.; Ohishi, Y.

2013-12-01

61

High Pressure Melting, Phase Diagrams, and Equations of State in the Fe-FeSi System with Application to Earth's Core  

NASA Astrophysics Data System (ADS)

The Earth's core is comprised mostly of iron, with some nickel and several weight percent of one or more light elements. The light element(s) dictate phase relations, structure, and dynamic behaviour, so it is crucial to evaluate various candidates at conditions of planetary interiors. We present results on high P-T phase diagrams and equations of state in the Fe-FeSi system with application to the structure and composition of Earth's core. X-ray diffraction measurements were performed on stoichiometric FeSi and on Fe-Si alloys containing 9 and 16 wt% silicon in a laser-heated diamond anvil cell at the APS, NSLS, and ALS. Pressures were determined from the lattice parameter of KBr. We have investigated the phase diagram of Fe-9Si to 100 GPa and over 3000 K. Our melting curve agrees with previous results on similar alloys [1,2], as demonstrated using multiple methods of detecting melting. Our subsolidus results are similar to those of Lin et al. [3], though we find the B2 structure instead of bcc, and a shallower slope for the hcp+B2 to fcc+B2 boundary. We studied phase relations of Fe-16Si to over 135 GPa, finding agreement with previous melting curves [2,4]. Below 45 GPa, this alloy has the D0_3 structure. At high pressures, Fe-16Si breaks down into a mixture of B2 and hcp phases, with this mixture stable to pressures of the Earth's outer core. This is the first study on the B2 phase of FeSi with in situ X-ray diffraction at high pressures and temperatures. We report a wide B2+B20 two-phase field in FeSi, with complete conversion to the B2 structure by ~42 GPa. A melting experiment on FeSi agrees with the results of Lord et al. [5]. We have synthesized our results with previous studies to construct T-X and P-X phase diagrams, and we have determined thermal equations of state of each alloy. Our measured densities can be used to constrain the maximum amount of silicon in the Earth's outer core by comparison to the equation of state of hcp-Fe [6] and the seismologically-determined density. Assuming a core-mantle boundary (CMB) temperature of 4000 +/- 500 K and a 1-2% density decrease upon melting, the amount of silicon in the outer core required to match PREM at the CMB is 11.3 +/- 1.5 weight percent, under the simplifying assumption of a purely Fe-Ni-Si outer core. The minimum temperature of an Fe-Si outer core is 4380 K, based on the eutectic melting point of Fe-FeSi alloys, and silicon is shown not to significantly depress the melting point of iron at core conditions. At the highest pressures reached, only the hcp and B2 structures are seen in the Fe-FeSi system. We predict that alloys containing more than ~4-8 wt% Si will convert to an hcp+B2 mixture and later to the hcp structure with increasing pressure, and that an iron-silicon alloy in the Earth's inner core would most likely be a mixture of hcp and B2 phases. [1] Kuwayama and Hirose (2004) Am Mineral 89, 273-276 [2] Morard et al. (2011) PCM 38, 767-776 [3] Lin et al (2002) Science 295, 313-315 [4] Asanuma et al. (2010) PCM 37, 353-359 [5] Lord et al. (2010) JGR 115, B06208 [6] Dewaele et al. (2006) PRL 97, 215504

Fischer, R. A.; Campbell, A. J.; Reaman, D. M.; Heinz, D. L.; Dera, P. K.; Prakapenka, V.

2012-12-01

62

Petrography, geochemistry, and 40Ar-39Ar ages of impact melt rocks and breccias from the Ames Impact Structure, Oklahoma: The Nicor Chestnut 18-4 drill core  

NASA Astrophysics Data System (ADS)

The 15-km-diameter Ames structure in northwestern Oklahoma is located 2.75 km below surface in Cambro-Ordovician Arbuckle dolomite, which is overlain by Middle Ordovician Oil Creek Formation shale. The feature is marked by two concentric ring structures, with the inner ring of about 5 km diameter probably representing the collapsed remnant of a structural uplift composed of brecciated Precambrian granite and Arbuckle dolomite. Wells from both the crater rim and the central uplift are oil- and gas-producing, making Ames one of the economically important impact structures. Petrographic, geochemical, and age data were obtained on samples from the Nicor Chestnut 18-4 drill core, off the NW flank of the central uplift. These samples represent the largest and best examples of impact melt breccia obtained so far from the Ames structure. They contain carbonate rocks which, therefore, are derived from the target sequence. The chemical composition of the impact melt breccias is similar to that of target granite, with variable carbonate admixture. Some impact melt rocks are enriched in siderophile elements indicating the possible presence of a meteoritic component. Based on stratigraphic arguments, the age of the crater was estimated at 470 Ma. Previous 40Ar-39Ar dating attempts of impact melt breccias from the Dorothy 1-19 core yielded plateau ages of about 285 Ma, which is in conflict with the stratigraphic age. The new 40Ar-39Ar age data obtained on the melt breccias from the Nicor Chestnut core by UV laser spot analysis, resulted in a range of ages with maxima around 300 Ma. These data could reflect processes related either the regional Nemaha Uplift or resetting due to hot brines active on a midcontinent-wide scale, perhaps in related to the Alleghenian and Ouachita orogenies. The age data indicate an extended burial phase associated with thermal overprint during Late Pennsylvanian-Permian.

Koeberl, Christian; Reimold, Wolf Uwe; Kelley, Simon P.

2001-05-01

63

Informational approach to the quantum symmetrization postulate  

NASA Astrophysics Data System (ADS)

A remarkable feature of quantum theory is that particles with identical intrinsic properties must be treated as indistinguishable if the theory is to give valid predictions in all cases. In the quantum formalism, indistinguishability is expressed via the symmetrization postulate (Dirac P 1926 Proc. R. Soc. A 112 661, Heisenberg W 1926 Z. Phys. 38 411), which restricts a system of identical particles to the set of symmetric states (‘bosons’) or the set of antisymmetric states (‘fermions’). However, the physical basis and range of validity of the symmetrization postulate has not been established. A well-known topological derivation of the postulate implies that its validity depends on the dimensionality of the space in which the particles move (Laidlaw M and DeWitt C 1971 Phys. Rev. D 3 1375–8, Leinaas J M and Myrheim J 1977 Il Nuovo Cimento B 37 1–23). Here we show that the symmetrization postulate can be derived by strictly adhering to the informational requirement that particles which cannot be experimentally distinguished from one another are not labelled. Our key novel postulate is the operational indistinguishability postulate, which posits that the amplitude of a process involving several indistinguishable particles is determined by the amplitudes of all possible transitions of these particles when treated as distinguishable. The symmetrization postulate follows by requiring consistency with the rest of the quantum formalism. The derivation implies that the symmetrization postulate admits no natural variants. In particular, the possibility that identical particles generically exhibit anyonic behavior in two dimensions is excluded.

Goyal, Philip

2015-01-01

64

Melt layer statistic of two firn cores recently drilled at Dye3 and South dome in the dry snow zone of Southern Greenland  

NASA Astrophysics Data System (ADS)

In the last couple of years remote sensing data have shown large areas of wet snow in the Southern part of the Greenland ice sheet. These melt features are attributed to the overall warming trend. Persistent warming implies changes in the firn layer as well. Even in areas of the dry snow zone one can observe sporadically a few ice lenses within the firn column indicating refrozen meltwater from warm events in the past. In our contribution we want to close the gap between investigations of firn cores drilled in the 70's and the observational record of remote sensing data over the last decade in South Greenland. The focus lies on firn of the dry snow zone which is sensitive against changes in a warming atmosphere and cold enough to prevent a longway percolation path of meltwater to several firn layers. To this end we had drilled two 45m-long firn cores at the former drilling sites of DYE3 (65°11'N, 43°49'W) and South Dome (SD) (63°32'N, 44°34'W) during a aircraft-supported field campaign 2012. The retrieved 3inch-firn core segments of 1m length are measured by a X-ray-scanning routine with the means of the core-scale AWI-ICE-CT. The 2d-density fields are calculated and allow to distinguish between refreezing meltwater and compacted firn. The depth-scales are converted to time-scales by using DEP (dielectric profiling) and (in case of DYE3) discrete sampled d18O measurements. Number density of melt layers and relative amount of melt show an synchronized behavior with an general increase over the last 30 years. Local maxima are observed in both sites at around 6-9m and 25m at DYE3 and 5-8m, 22m and 40m at SD.

Freitag, Johannes; Kipfstsuhl, Sepp; Hoerz, Sebastian; Eling, Lukas; Vinther, Bo; Popp, Trevor

2014-05-01

65

Hot-melt co-extrusion for the production of fixed-dose combination products with a controlled release ethylcellulose matrix core.  

PubMed

In this study, hot-melt co-extrusion was evaluated as a technique for the production of fixed-dose combination products, using ethylcellulose as a core matrix former to control the release of metoprolol tartrate and a polyethylene oxide-based coat formulation to obtain immediate release of hydrochlorothiazide. By lowering the concentration of the hydrophilic additive polyethylene oxide in the plasticized ethylcellulose matrix or by lowering the drug load, the in vitro metoprolol tartrate release from the core was substantially sustained. The in vitro release of hydrochlorothiazide from the polyethylene oxide/polyethylene glycol coat was completed within 45 min for all formulations. Tensile testing of the core/coat mini-matrices revealed an adequate adhesion between the two layers. Raman mapping showed no migration of active substances. Solid state characterization indicated that the crystalline state of metoprolol tartrate was not affected by thermal processing via hot-melt extrusion, while hydrochlorothiazide was amorphous in the coat. These solid state characteristics were confirmed during the stability study. Considering the bioavailability of metoprolol tartrate after oral administration to dogs, the different co-extruded formulations offered a range of sustained release characteristics. Moreover, high metoprolol tartrate plasma concentrations were reached in dogs allowing the administered dose to be halved. PMID:24486558

Vynckier, A-K; Dierickx, L; Saerens, L; Voorspoels, J; Gonnissen, Y; De Beer, T; Vervaet, C; Remon, J P

2014-04-10

66

Calculation of the individual and population doses on Danish territory resulting from hypothetical core-melt accidents at the Barsebäck reactor.  

PubMed

Individual and population doses on Danish territory are calculated from hypothetical, severe core-melt accidents at the Swedish nuclear plant at Barsebäck. The release fractions for these accidents are taken from WASH-1400. Based on parametric studies, doses are calculated for very unfavourable, but not incredible weather conditions. The probability of such conditions in combination with wind direction towards Danish territory is estimated. Doses to bone marrow, lungs, GI-tract and thyroid are calculated using dose models developed at Risø. These doses are found to be consistent with doses calculated with the models used in WASH-1400. PMID:597357

Jensen, P H; Petersen, E L; Thykier-Nielsen, S; Vinther, F H

1977-10-01

67

Final results of the XR2-1 BWR metallic melt relocation experiment  

SciTech Connect

This report documents the final results of the XR2-1 boiling water reactor (BWR) metallic melt relocation experiment, conducted at Sandia National Laboratories for the U.S. Nuclear Regulatory Commission. The objective of this experiment was to investigate the material relocation processes and relocation pathways in a dry BWR core following a severe nuclear reactor accident such as an unrecovered station blackout accident. The imposed test conditions (initial thermal state and the melt generation rates) simulated the conditions for the postulated accident scenario and the prototypic design of the lower core test section (in composition and in geometry) ensured that thermal masses and physical flow barriers were modeled adequately. The experiment has shown that, under dry core conditions, the metallic core materials that melt and drain from the upper core regions can drain from the core region entirely without formation of robust coherent blockages in the lower core. Temporary blockages that suspended pools of molten metal later melted, allowing the metals to continue draining downward. The test facility and instrumentation are described in detail. The test progression and results are presented and compared to MERIS code analyses. 6 refs., 55 figs., 4 tabs.

Gauntt, R.O.; Humphries, L.L.

1997-08-01

68

Radiological Impact Assessment (RIA) following a postulated accident in PHWRS  

SciTech Connect

Radiological Impact Assessment (RIA) following postulated accident i.e Loss of Coolant Accident (LOCA) with failed Emergency Core Cooling System (ECCS), performed as part of the reactor safety analysis of a typical 700 MWe Indian Pressurized Heavy Water Reactor(PHWR). The rationale behind the assessment is that the public needs to be protected in the event that the postulated accident results in radionuclide release outside containment. Radionuclides deliver dose to the human body through various pathways namely, plume submersion, exposure due to ground deposition, inhalation and ingestion. The total exposure dose measured in terms of total effective dose equivalent (TEDE) is the sum of doses to a hypothetical adult human at exclusion zone boundary by all the exposure pathways. The analysis provides the important inputs to decide upon the type of emergency counter measures to be adopted during the postulated accident. The importance of the various pathways in terms of contribution to the total effective dose equivalent(TEDE) is also assessed with respect to time of exposure. Inhalation and plume gamma dose are the major contributors towards TEDE during initial period of accident whereas ingestion and ground shine dose start dominating in TEDE in the extended period of exposure. Moreover, TEDE is initially dominated by I-131, Kr-88, Te-132, I-133 and Sr-89, whereas, as time progresses, Xe-133,I-131 and Te-132 become the main contributors. (authors)

Soni, N.; Kansal, M.; Rammohan, H. P.; Malhotra, P. K. [Reactor Safety and Analysis, Nuclear Power Corporation of India Ltd., Nabhkiya Urja Bhavan, Anushakti Nagar, Mumbai Maharashtra 400094 (India)

2012-07-01

69

Equivalence Postulate and Quantum Origin of Gravitation  

Microsoft Academic Search

We suggest that quantum mechanics and gravity are intimately related. In particular, we investigate the quantum Hamilton-Jacobi equation in the case of two free particles and show that the quantum potential, which is attractive, may generate the gravitational potential. The investigation, related to the formulation of quantum mechanics based on the equivalence postulate, is based on the analysis of the

Marco Matone; G. Galilei

2000-01-01

70

Low energy nuclear reaction polyplasmon postulate  

Microsoft Academic Search

An explanation is proposed for the nuclear reactions that occur in the electrolysis class of LENR processes. The proposed explanation postulates that a proton, or deuteron, dissolved in the hydrogen bearing metal cathode, absorbs its associated atomic electron to become a short lived state of the neutron with the resulting neutrino in a singular wave function centered on the neutron.

John L. Russell

2008-01-01

71

Ringwoodite rim around olivine core in shock-induced melt veins of Antarctic chondrite : Mechanisms of transformation and Fe-Mg diffusion  

NASA Astrophysics Data System (ADS)

Introduction: High-pressure minerals, produced by shock metamorphism, are common in and around melt veins in highly shocked chondrites. The shock duration can be constrained by using transformation kinetics, such as the crystallization rate of the melt-vein matrix[1-2], or growth rate of the high-pressure minerals [3-4], or using elements diffusion rate between two minerals [5]. Using transformation kinetics to constrain shock duration de-pend on the details of the transformation mechanism. For example, growth of topotaxial ringwoodite in olivine with coherent interfaces is slower than growth of inclusions with incoherent interfaces [4-5]. Similarly, diffusion-controlled growth, where rates are determined by long-range diffusion, is generally much slower than interface-controlled growth, which is only dependent on diffusion across the interface [6-8]. The occurrences of the high-pressure mineral rims were recently reported in shock-induced melt veins in several heavily shocked (S6) chondrites, ALH78003, Peace River and GRV052049 [9-11]. Here we report EMAP and Raman results of the ringwoodite rims around olivine cores in shock veins of the Antarctic chondrites GRV 022321, and to elucidate the mechanisms of transformation and Mg-Fe diffusion of the olivine to ringwoodite. Results: GRV022321 has a network of black veins which enclose abundant host-rock fragments. The enclosed fragments have sizes ranging from 5 µm to 30 µm, with a brighter rim up to several µm wide and a dark core in reflected light and BSE image. The Raman data reveal that the rim mineral is ringwoodite signature, and the core minerals are dominated by olivine and mixed minor ringwoodite. EMAP data confirm that the ringwoodite in rim is richer in faylite (Fa) than the olivine core. The Fa values range from 50 to 10 with the outer rim having highest Fa value, and the inside darker area with a lower value. Discussion: The occurrence of the rounded shape grains with smooth edges embedded in the fine matrix in shock-induced melt veins suggest that they are enclosed host-rock fragments and that the ringwoodite in the rim was transformed by solid-state transformation from previous olivine. The variable extent of transformation is likely a result of temperature variations during shock, with the hottest outer olivine forming the ringwoodite rim. The outer hotter ringwoodite attract more Fe than inside cooler olivine, and Mg-Fe diffusion occurs in rapid transformation at high pressure and temperature over up to 10 µm distance. The sample is unique because we can test and double check different shock duration constraints in future work. References: [1] Langenhorst and Poirier (2000) EPSL 184, 37-55. [2] Xie, Z. et al. (2006) GCA, 70. 504-515. [3] Ohtani et al. (2004) EPSL 227(3-4), 505-515. [4] Xie and Sharp (2007), EPLS, 433-445. [5] Beck, et al. (2005) Nature 435, 1071-1074. [6] Kerschhofer et al. (1996) Science 274 (5284), 79-81. [7] Kerschhofer et al. (2000) PEPI 121, 59-76. [8] Sharp and DeCarli (2006) MESS II, 653-677. [9] Ohtani et al. (2006), Shock Waves, 16:45-52. [10] Miyahara et al. (2008) Proceedings. of NAS 105,8542-8547. [11] Feng et al. (2007), MAPS 42, A45.

Xie, Z.; Li, X.; Sharp, T. G.; de Carli, P. S.

2009-12-01

72

Testing the ureilite projectile hypothesis for the El'gygytgyn impact: Determination of siderophile element abundances and Os isotope ratios in ICDP drill core samples and melt rocks  

NASA Astrophysics Data System (ADS)

The geochemical nature of the impactites from International Continental Scientific Drilling Project—El'gygytgyn lake drill core 1C is compared with that of impact melt rock fragments collected near the western rim of the structure and literature data. Concentrations of major and trace elements, with special focus on siderophile metals Cr, Co, Ni, and the platinum group elements, and isotope ratios of osmium (Os), were determined to test the hypothesis of an ureilite impactor at El'gygytgyn. Least squares mixing calculations suggest that the upper volcanic succession of rhyolites, dacites, and andesites were the main contributors to the polymict impact breccias. Additions of 2-13.5 vol% of basaltic inclusions recovered from drill core intervals between 391.6 and 423.0 mblf can almost entirely account for the compositional differences observed for the bottom of a reworked fallout deposit at 318.9 mblf, a polymict impact breccia at 471.4 mblf, and three impact melt rock fragments. However, the measured Os isotope ratios and slightly elevated PGE content (up to 0.262 ng g-1 Ir) of certain impactite samples, for which the CI-normalized logarithmic PGE signature displays a relatively flat (i.e., chondritic) pattern, can only be explained by the incorporation of a small meteoritic contribution. This component is also required to explain the exceptionally high siderophile element contents and corresponding Ni/Cr, Ni/Co, and Cr/Co ratios of impact glass spherules and spherule fragments that were recovered from the reworked fallout deposits and from terrace outcrops of the Enmyvaam River approximately 10 km southeast of the crater center. Mixing calculations support the presence of approximately 0.05 wt% and 0.50-18 wt% of ordinary chondrite (possibly type-LL) in several impactites and in the glassy spherules, respectively. The heterogeneous distribution of the meteoritic component provides clues for emplacement mechanisms of the various impactite units.

Goderis, S.; Wittmann, A.; Zaiss, J.; Elburg, M.; Ravizza, G.; Vanhaecke, F.; Deutsch, A.; Claeys, P.

2013-07-01

73

Megablocks and melt pockets in the Chesapeake Bay impact structure constrained by magnetic field measurements and properties of the Eyreville and Cape Charles cores  

USGS Publications Warehouse

We use magnetic susceptibility and remanent magnetization measurements of the Eyreville and Cape Charles cores in combination with new and previously collected magnetic field data in order to constrain structural features within the inner basin of the Chesapeake Bay impact structure. The Eyreville core shows the first evidence of several-hundred-meter-thick basement-derived megablocks that have been transported possibly kilometers from their pre-impact location. The magnetic anomaly map of the structure exhibits numerous short-wavelength (<2 km) variations that indicate the presence of magnetic sources within the crater fill. With core magnetic properties and seismic reflection and refraction results as constraints, forward models of the magnetic field show that these sources may represent basementderived megablocks that are a few hundred meters thick or melt bodies that are a few dozen meters thick. Larger-scale magnetic field properties suggest that these bodies overlie deeper, pre-impact basement contacts between materials with different magnetic properties such as gneiss and schist or gneiss and granite. The distribution of the short-wavelength magnetic anomalies in combination with observations of small-scale (1-2 mGal) gravity field variations suggest that basement-derived megablocks are preferentially distributed on the eastern side of the inner crater, not far from the Eyreville core, at depths of around 1-2 km. A scenario where additional basement-derived blocks between 2 and 3 km depth are distributed throughout the inner basin-and are composed of more magnetic materials, such as granite and schist, toward the east over a large-scale magnetic anomaly high and less magnetic materials, such as gneiss, toward the west where the magnetic anomaly is lower-provides a good model fi t to the observed magnetic anomalies in a manner that is consistent with both gravity and seismic-refraction data. ?? 2009 The Geological Society of America.

Shah, A.K.; Daniels, D.L.; Kontny, A.; Brozena, J.

2009-01-01

74

Boundary pressure of inter-connection of Fe-Ni-S melt in olivine based on in-situ X-ray tomography: Implication to core formation in asteroids  

NASA Astrophysics Data System (ADS)

Interconnectivity of Fe-alloy melt in crystalline silicates is important property for the core formation mechanism in planetary interior. In previous studies, the interconnectivity of Fe-alloy melt has been studied based on textural observation of recovered samples from high pressure and temperature. However, there is no observation under high pressure and temperature. We have developed 80-ton uni-axial press for X-ray computed micro-tomography (X-CT) and performed X-CT measurement under high pressure (Urakawa et al. 2010). Here we report X-CT measurement of Fe-Ni-S melt in crystalline olivine and interconnectivity of the melt up to 3.5 GPa and 1273 K. X-CT measurements were carried out at BL20B2 beamline, SPring-8 synchrotron facility. The sample was powder mixture of Fe-Ni-S and olivine, which was enclosed in graphite capsule. Heating was performed using a cylindrical graphite furnace. Pressure was generated using opposed toroidal-shape WC anvil. The uni-axial press was set on the rotational stage and X-ray radiography image of the sample was collected using CCD camera from 0°to 180°with 0.3° step. 3-D image of the sample was obtained by reconstructing the 2-D radiography image. The 3-D CT image shows that the size of the Fe-Ni-S melt increased significantly compared to that before melting below 2.5 GPa, suggesting that the melt was interconnected in olivine crystals. On the other hand, 3-D texture of the sample at 3.5 GPa did not show difference from that before melting. Therefore, the boundary of inter-connection of Fe-Ni-S melt is likely to locate between 2.5 and 3.5 GPa. This result is important application for the core formation mechanism especially in small bodies, such as differentiated asteroids.

Terasaki, H.; Urakawa, S.; Uesugi, K.; Nakatsuka, A.; Funakoshi, K.; Ohtani, E.

2011-12-01

75

Nonlinear damage analysis: Postulate and evaluation  

NASA Technical Reports Server (NTRS)

The objective of this program is to assess the viability of a damage postulate which asserts that the fatigue resistance curve of a metal is history dependent due to inelastic action. The study focusses on OFE copper because this simple model material accentuates the inelastic action central to the damage postulate. Data relevant to damage evolution and crack initiation are developed via a study of surface topography. The effects of surface layer residual stresses are explored via comparative testing as were the effects in initial prestraining. The results of the study very clearly show the deformation history dependence of the fatigue resistance of OFE copper. Furthermore the concept of deformation history dependence is shown to qualitatively explain the fatigue resistance of all histories considered. Likewise quantitative predictions for block cycle histories are found to accurately track the observed results. In this respect the assertion that damage per cycle for a given level of the damage parameter is deformation history dependent appears to be physically justified.

Leis, B. N.; Forte, T. P.

1983-01-01

76

Special Relativity in a Nutshell Basic Postulates: Einstein 1905  

E-print Network

COSMOLOGY Special Relativity in a Nutshell Basic Postulates: Einstein 1905 All observers moving Lect. 4 R 138 #12;COSMOLOGY Special Relativity in a Nutshell Basic Postulates: Einstein 1905 All;COSMOLOGY Special Relativity in a Nutshell Basic Postulates: Einstein 1905 All observers moving uniformly

Peters, Achim

77

Signal and noise in four ice-core records from the Agassiz Ice Cap, Ellesmere Island, Canada: details of the last millennium for stable isotopes, melt and solid conductivity  

Microsoft Academic Search

Four ice cores and two deep pit\\/auger sequences from the top of the Agassiz Ice Cap have been variously analysed for ?(O18), ECM (solid conductivity) and ice melt-layer stratigraphy. The high- resolution data are presented on time scales covering about the last 1000 years. The 8 time series are compared and the noise examined in terms of snow-drifting and wind-scouring

David A. Fisher; Roy M. Koerner

1994-01-01

78

Ringwoodite rim around olivine core in shock-induced melt veins of Antarctic chondrite : Mechanisms of transformation and Fe-Mg diffusion  

Microsoft Academic Search

Introduction: High-pressure minerals, produced by shock metamorphism, are common in and around melt veins in highly shocked chondrites. The shock duration can be constrained by using transformation kinetics, such as the crystallization rate of the melt-vein matrix[1-2], or growth rate of the high-pressure minerals [3-4], or using elements diffusion rate between two minerals [5]. Using transformation kinetics to constrain shock

Z. Xie; X. Li; T. G. Sharp; P. S. de Carli

2009-01-01

79

A proof of von Neumann's postulate in Quantum Mechanics  

SciTech Connect

A Clifford algebraic analysis is explained. It gives proof of von Neumann's postulate on quantum measurement. It is of basic significance to explain the problem of quantum wave function reduction in quantum mechanics.

Conte, Elio [Department of Pharmacology and Human Physiology, TIRES-Center for Innovative Technologies for Signal Detection and Processing, Department of Physics, University of Bari (Italy) and School of Advanced International Studies for Applied Theoretical and Non Linear Methodologies of Physics, Bari (Italy)

2010-05-04

80

Melting Ice  

NSDL National Science Digital Library

Monitor the temperature of a melting ice cube and use temperature probes to electronically plot the data on graphs. Investigate what temperature the ice is as it melts in addition to monitoring the temperature of liquid the ice is submerged in.

2012-07-19

81

Melting Icebergs  

NSDL National Science Digital Library

This formative assessment item uncovers student ideas and misconceptions about melting icebergs. It determines if students believe that water levels will rise due to melting icebergs. Resources provided will assist teachers. It gives instructional support as well as information for teachers. This probe is aligned to National Science Education Standards (NSES).

Jessica Fries-Gaither

82

Von Neumann and Luders postulates and quantum information theory  

E-print Network

This note is devoted to some foundational aspects of quantum mechanics (QM) related to quantum information (QI) theory, especially quantum teleportation and ``one way quantum computing.'' We emphasize the role of the projection postulate (determining post-measurement states) in QI and the difference between its L\\"uders and von Neumann versions. These projection postulates differ crucially in the case of observables with degenerate spectra. Such observables play the fundamental role in operations with entangled states: any measurement on one subsystem is represented by an observable with degenerate spectrum in the Hilbert space of a composite system. If von Neumann was right and L\\"uders was wrong the canonical schemes of quantum teleportation and ``one way quantum computing'' would not work. Surprisingly, we found that, in fact, von Neumann's description of measurements via refinement implies (under natural assumptions) L\\"uders projection postulate. It seems that this important observation was missed during last 70 years. This result closed the problem of the proper use of the projection postulate in quantum information theory. One can proceed with L\\"uders postulate (as people in quantum information really do).

Andrei Khrennikov

2009-05-27

83

Glacier Melt  

NSDL National Science Digital Library

This short video shows an example of melting alpine glaciers in the Austrian Alps (Goldberg Glacier). Disappearing alpine glaciers have social and environmental impacts, including the decline of fresh water supplies and contributing to sea level rise.

National Geographic

84

One Hair Postulate for Hawking Radiation as Tunneling Process  

NASA Astrophysics Data System (ADS)

For Hawking radiation, treated as a tunneling process, the no-hair theorem of black hole together with the law of energy conservation is utilized to postulate that the tunneling rate only depends on the external qualities (e.g., the mass for the Schwarzschild black hole) and the energy of the radiated particle. This postulate is justified by the WKB approximation for calculating the tunneling probability. Based on this postulate, a general formula for the tunneling probability is derived without referring to the concrete form of black hole metric. This formula implies an intrinsic correlation between the successive processes of the black hole radiation of two or more particles. It also suggests a kind of entropy conservation and thus resolves the puzzle of black hole information loss in some sense.

Dong, Hui; Cai, Qing-Yu; Liu, Xu-Feng; Sun, Chang-Pu

2014-03-01

85

One Hair Postulate for Hawking Radiation as Tunneling Process  

E-print Network

For Hawking radiation, treated as a tunneling process, the no-hair theorem of black hole together with the law of energy conservation is utilized to postulate that the tunneling rate only depends on the external qualities (e.g., the mass for the Schwarzschild black hole) and the energy of the radiated particle. This postulate is justified by the WKB approximation for calculating the tunneling probability. Based on this postulate, a general formula for the tunneling probability is derived without referring to the concrete form of black hole metric. This formula implies an intrinsic correlation between the successive processes of the black hole radiation of two or more particles. It also suggests a kind of entropy conservation and thus resolves the puzzle of black hole information loss in some sense.

H. Dong; Qing-yu Cai; X. F. Liu; C. P. Sun

2009-07-13

86

Melting in super-earths.  

PubMed

We examine the possible extent of melting in rock-iron super-earths, focusing on those in the habitable zone. We consider the energetics of accretion and core formation, the timescale of cooling and its dependence on viscosity and partial melting, thermal regulation via the temperature dependence of viscosity, and the melting curves of rock and iron components at the ultra-high pressures characteristic of super-earths. We find that the efficiency of kinetic energy deposition during accretion increases with planetary mass; considering the likely role of giant impacts and core formation, we find that super-earths probably complete their accretionary phase in an entirely molten state. Considerations of thermal regulation lead us to propose model temperature profiles of super-earths that are controlled by silicate melting. We estimate melting curves of iron and rock components up to the extreme pressures characteristic of super-earth interiors based on existing experimental and ab initio results and scaling laws. We construct super-earth thermal models by solving the equations of mass conservation and hydrostatic equilibrium, together with equations of state of rock and iron components. We set the potential temperature at the core-mantle boundary and at the surface to the local silicate melting temperature. We find that ancient (?4?Gyr) super-earths may be partially molten at the top and bottom of their mantles, and that mantle convection is sufficiently vigorous to sustain dynamo action over the whole range of super-earth masses. PMID:24664915

Stixrude, Lars

2014-04-28

87

Safely Teaching Koch's Postulates on the Causation of Infectious Disease.  

ERIC Educational Resources Information Center

Described is an activity in which the interactions between a parasite and its host may be demonstrated using the relationship between yogurt and two species of bacteria. Background information on Koch's postulates is provided. Materials, laboratory procedures, and results are discussed. (CW)

Stewart, Peter R.

1990-01-01

88

How to Teach the Postulates of Quantum Mechanics without Enigma.  

ERIC Educational Resources Information Center

Shows how a statistical approach can help students accept postulates of quantum mechanics. The approach, which also makes students aware of the philosophical/humanistic implications of quantum mechanics, involves the following sequence: (1) important experiments in quantum mechanics; (2) conventional statistical interpretation; (3) mathematical…

Teixeira-Dias, Jose J. C.

1983-01-01

89

A Conceptual Derivation of Einstein's Postulates of Special Relativity.  

ERIC Educational Resources Information Center

This document presents a discussion and conceptual derivation of Einstein's postulates of special relativity. The perceptron approach appears to be a fundamentally new manner of regarding physical phenomena and it is hoped that physicists will interest themselves in the concept. (Author)

Bearden, Thomas E.

90

Fission product transport and behavior during two postulated loss of flow transients in the air  

SciTech Connect

This document discusses fission product behavior during two postulated loss-of-flow accidents (leading to high- and low-pressure core degradation, respectively) in the Advanced Test Reactor (ATR). These transients are designated ATR Transient LCPI5 (high-pressure) and LPP9 (low-pressure). Normally, transients of this nature would be easily mitigated using existing safety systems and procedures. In these analyses, failure of these safety systems was assumed so that core degradation and fission product release could be analyzed. A probabilistic risk assessment indicated that the probability of occurrence for these two transients is of the order of 10{sup {minus}5 }and 10{sup {minus}7} per reactor year for LCP15 and LPP9, respectively.

Adams, J.P.; Carboneau, M.L.

1991-01-01

91

Time-Scales of Melt Generation in the Ama Drime and Leo Pargil Domes: Quantifying Links Between Mid-Crustal Anatexis and Exhumation in the Core of the Himalayan Orogen  

NASA Astrophysics Data System (ADS)

Miocene crustal anatectic events within the core of the Himalayan orogen have been implicated by some researchers as a key driver of rapid, large-scale extrusion and exhumation of mid-crustal rocks from beneath the southern margin of the Tibetan plateau. However, it remains unclear whether melting is the primary driving force behind exhumation, or whether exhumation, forced by orogen-scale tectonic events, triggers melting. Domes exhumed during orogen-parallel extension within the high Himalaya such as Ama Drime Massif (ADM) in southern Tibet and Leo Pargil dome (LPD) in NW India provide a unique opportunity to integrate field, petrologic and geochronologic datasets that link the timing and duration of leucogranite formation to specific structural, thermal and exhumation events. These data also yield detailed knowledge of the temporal- and spatial-scales over which anatexis occurs within the mid-crust. Our data from the ADM, located c. 60km east of Mt. Everest indicate the presence of a relatively simple melt chronology that post-dates anatexis in the overlying Greater Himalayan Series (GHS) by 8 - 3 Ma. Initial syn-kinematic melting of granitic orthogneiss at granulite-facies Pressure-Temperature (P-T) conditions of 750°C and 0.8GPA occurred at 13 - 12 Ma. This was immediately followed by emplacement of post-kinematic dykes along steep semi-brittle structures at 12-11 Ma. We interpret these data to record rapid melt-present exhumation of deep crustal material in the footwall of north-striking normal-fault systems. Exhumation occurred concomitantly with, and is directly related to, orogen-parallel flow that post-dates movement on the South Tibetan Detachment system - Main Central Thrust system. Rocks preserved within the ADM may therefore represent a good analogue for modern melt generation that, as argued by some, is potentially occurring beneath the Tibetan plateau today. In contrast, observations from the LPD indicate the presence of multiple (in some cases greater than five) generations of leucogranite at the outcrop-scale. Other key observations include: 1) the density-distribution of leucogranites is heterogeneous throughout the dome; 2) an apparent spread in crystallization ages from c. 26 to 16 Ma; 3) variations in chemical and mineralogical composition of leucogranites; and 4) differences in the timing of leucogranite emplacement relative to major kinematic and metamorphic events. When combined these observations suggest that the LPD has a protracted thermal and structural history with multiple phases of melt-generation under differing P-T conditions and kinematic configurations. At the orogen-scale, data from the ADM and LPD imply that Himalayan leucogranites provide key geologic evidence for changes in mid-crustal rheology (effective bulk viscosity) and therefore offer a proxy for estimating crustal strength through time. These data are therefore crucial input into large-scale geodynamic models that attempt to explain spatial and temporal scales of flow in the mid-crust.

Cottle, J. M.; Jessup, M. J.

2009-12-01

92

OPERA data and The Equivalence Postulate of Quantum Mechanics  

E-print Network

An interpretation of the recent results reported by the OPERA collaboration is that neutrinos propagation in vacuum exceeds the speed of light. It has been further been suggested that this interpretation can be attributed to the variation of the particle speed arising from the Relativistic Quantum Hamilton Jacobi Equation. I show that this is in general not the case. I derive an expression for the quantum correction to the instantaneous relativistic velocity in the framework of the relativistic quantum Hamilton-Jacobi equation, which is derived from the equivalence postulate of quantum mechanics. While the quantum correction does indicate deviations from the classical energy--momentum relation, it does not necessarily lead to superluminal speeds. The quantum correction found herein has a non-trivial dependence on the energy and mass of the particle, as well as on distance travelled. I speculate on other possible observational consequences of the equivalence postulate approach.

Alon E. Faraggi

2011-10-24

93

The Four Postulates of Freudian Unconscious Neurocognitive Convergences  

PubMed Central

In the 1980s, the terms “cognitive unconscious” were invented to denominate a perspective on unconscious mental processes independent from the psychoanalytical views. For several reasons, the two approaches to unconscious are generally conceived as irreducible. Nowadays, we are witnessing a certain convergence between both fields. The aim of this paper consists in examining the four basic postulates of Freudian unconscious at the light of neurocognitive sciences. They posit: (1) that some psychological processes are unconsciously performed and causally determine conscious processes, (2) that they are governed by their own cognitive rules, (3) that they set out their own intentions, (4) and that they lead to a conflicting organization of psyche. We show that each of these postulates is the subject of empirical and theoretical works. If the two fields refer to more or less similar mechanisms, we propose that their opposition rests on an epistemological misunderstanding. As a conclusion, we promote a conservative reunification of the two perspectives. PMID:21734896

Arminjon, Mathieu

2011-01-01

94

Equivalence Postulate and the Quantum Potential of Two Free Particles  

Microsoft Academic Search

Commutativity of the diagram of the maps connecting three one--particle\\u000astate, implied by the Equivalence Postulate (EP), gives a cocycle condition\\u000awhich unequivocally leads to the quantum Hamilton--Jacobi equation. Energy\\u000aquantization is a direct consequences of the local homeomorphicity of the\\u000atrivializing map. We review the EP and show that the quantum potential for two\\u000afree particles, which depends on

Marco Matone; G. Galilei

2002-01-01

95

Melting Glaciers  

NSDL National Science Digital Library

Due to the potential disastrous consequences to the environment and to numerous societies, scientists, governments, and civilians are concerned with the growing trend of glacial melt. This topic-in-depth explores various geographic regions where this phenomenon has recently been observed. Providing background into the study of glaciology, this report begins with a Web site (1) discussing the unique features of glaciers. The US Army Corps of Engineers offers visitors an insight to glacial properties including their locations, movements, and influences; along with a series educational images. The second site (2) explains the exceptionality of the two hundred sixty six glaciers at Glacier National Park. Through a collection of images, animations, and pictures provided by the National Park Service, users can learn about ice dams, climatic impacts, and the erosive powers of ice and water. The rest of the topic-in-depth discusses findings of glacial melting from around the world. NASA (3) addresses the Artic warming's affects on glacier formations. This Web site provides a few animations displaying ice sheet extent and the cracking of icebergs. On a positive note, visitors can learn how the decrease in glaciers has opened up new habitat for some Artic species. The next Web site (4), also by NASA, discusses the findings of a twenty-five year study of Patagonia's glaciers. Educators and students can discover how NASA utilized the Space Shuttle Endeavor to study the entire 17,200 square kilometer region. The site also discusses potential causes of the melting in this region, which has contributed to almost ten percent of the global sea-level change from mountain glaciers. As reported by the BBC (5), Dr. Harrison at the University of Oxford has determined that the glaciers in parts of Kazakhstan have been decreasing annually by almost two cubic kilometers between 1955 and 2000. Visitors can learn how the melting of these four hundred sixteen glaciers will adversely affect the region's rivers and its water supply. The Taipei Times (6) reports that the Swiss Alpine glacial melting has probably intensified due to this summer's record-breaking heat wave. This Web site provides short, intriguing descriptions of consequences of the "rush of melt water streaming from the ice wall." Users can learn about predictions in the 1990s that the glaciers would shrink to ten percent of their 1850 size by the end of the twenty first century. In the next Web site (7), the BBC provides a captivating illustration of the effects the Peruvian glacial melts may have on tourism, the country's water supply, and more. Students and educators can learn about NASA studies showing cracks in the ice, which could lead to the flooding of large cities. Visitors can also find out how the recent glacier recessions have affected some ancient spiritual traditions. The last site, by the USGS, (8) features excerpts from Myrna Hall and Daniel Fagre's 2003 research paper in BioScience. Visitors can discover the melt rate and spatial distributions of glaciers for two possible future climate situations. Providing an amazing animation, users will be amazed by the changes predicted by the model.

Enright, Rachel

96

Repeated measurements from unitary evolution: avoiding the projection postulate  

E-print Network

Repeated measurements as typically occurring in two-time correlators rely on von Neumann's projection postulate, telling how to restart the system after a measurement. We describe an alternative procedure where co-evolving quantum memories extract system information through entanglement, combined with a final readout of the memories according to Born's rule. We apply this procedure to the calculation of the electron charge correlator in mesoscopic physics and the photon intensity correlator in quantum optics. While our approach to repeated quantum measurements deals with any system-memory coupling, we show that the limits of strong (weak) measurements are correctly reproduced at strong (weak) coupling.

David Oehri; Andrei V. Lebedev; Gordey B. Lesovik; Gianni Blatter

2015-02-10

97

Analysis of hydrodynamic phenomena in simulant experiments investigating cavity interactions following postulated vessel meltthrough  

SciTech Connect

An analysis of hydrodynamic phenomena in simulant experiments examining aspects of ex-vessel material interactions in a PWR reactor cavity following postulated core meltdown and localized breaching of the reactor vessel has been carried out. While previous analyses of the tests examined thresholds for the onset of sweepout of fluid from the cavity, the present analysis considers the progression of specific hydrodynamic phenomena involved in the dispersal process: crater formation due to gas jet impingement, radial wave motion and growth, entrainment and transport of liquid droplets, liquid layer formation due to droplet recombination, fluidization of liquid remaining in the cavity, removal of fluidized liquid droplets from the cavity, and the ultimate removal of the remaining liquid layer within the tunnel passageway. Phenomenological models which may be used to predict the phenomena are presented.

Sienicki, J.J.; Spencer, B.W.

1984-01-01

98

Hidden carbon in Earth's inner core revealed by shear softening in dense Fe7C3.  

PubMed

Earth's inner core is known to consist of crystalline iron alloyed with a small amount of nickel and lighter elements, but the shear wave (S wave) travels through the inner core at about half the speed expected for most iron-rich alloys under relevant pressures. The anomalously low S-wave velocity (vS) has been attributed to the presence of liquid, hence questioning the solidity of the inner core. Here we report new experimental data up to core pressures on iron carbide Fe7C3, a candidate component of the inner core, showing that its sound velocities dropped significantly near the end of a pressure-induced spin-pairing transition, which took place gradually between 10 GPa and 53 GPa. Following the transition, the sound velocities increased with density at an exceptionally low rate. Extrapolating the data to the inner core pressure and accounting for the temperature effect, we found that low-spin Fe7C3 can reproduce the observed vS of the inner core, thus eliminating the need to invoke partial melting or a postulated large temperature effect. The model of a carbon-rich inner core may be consistent with existing constraints on the Earth's carbon budget and would imply that as much as two thirds of the planet's carbon is hidden in its center sphere. PMID:25453077

Chen, Bin; Li, Zeyu; Zhang, Dongzhou; Liu, Jiachao; Hu, Michael Y; Zhao, Jiyong; Bi, Wenli; Alp, E Ercan; Xiao, Yuming; Chow, Paul; Li, Jie

2014-12-16

99

Melting Ice  

NSDL National Science Digital Library

In this lesson, students explore a discrepant event when they design an experiment to measure the rate that ice melts when in pure water versus salt water. It is designed to help students realize that a carefully-designed experiment may yield unexpected results, due to unseen events, even though the experiment is precisely planned and executed. The addition of a new technology may clarify factors in the experiment which were previously unknown. Note: the experiment requires advance preparation the day before: two buckets of water are set-up (one with plain tap water, the other with as much salt dissolved in it as possible), which need to be at room temperature. It also requires ice cubes of uniform shape (e.g., from an ice maker or ice trays filled to uniform capacity). This lesson is part of the Cosmic Times teachers guide and is intended to be used in conjunction with the 1993 Cosmic Times Poster.

2012-08-03

100

Causation and Disease: The Henle-Koch Postulates Revisited 1  

PubMed Central

The Henle-Koch postulates are reviewed in terms of their full validity in Koch's day and in light of subsequent developments. The changing guidelines developed for viral diseases, for viruses in relation to cancer and to chronic central nervous system infection, and for causative agents in chronic diseases are discussed chronologically. A set of guidelines for both acute infectious and chronic diseases is presented. The need for recognizing the role of the host and the spectrum of host responses, for sound biologic sense in evaluating causal roles of agents in disease, and for flexibility in adapting our guidelines to new knowledge are emphasized. ImagesFIG. 1FIG. 2FIG. 3FIG. 4FIG. 5FIG. 6FIG. 7FIG. 8 PMID:782050

Evans, Alfred S.

1976-01-01

101

A random spatial network model based on elementary postulates  

USGS Publications Warehouse

In contrast to the random topology model, this model ascribes a unique spatial specification to generated drainage networks, a distinguishing property of some network growth models. The simplicity of the postulates creates an opportunity for potential analytic investigations of the probabilistic structure of the drainage networks, while the spatial specification enables analyses of spatially dependent network properties. In the random topology model all drainage networks, conditioned on magnitude (number of first-order streams), are equally likely, whereas in this model all spanning trees of a grid, conditioned on area and drainage density, are equally likely. As a result, link lengths in the generated networks are not independent, as usually assumed in the random topology model. -from Authors

Karlinger, M.R.; Troutman, B.M.

1989-01-01

102

Skylab M551 metals melting experiment  

NASA Technical Reports Server (NTRS)

The objectives of the M551 Metals Melting Experiment were to: (1) study behavior of molten metal, (2) characterize metals melted and solidified in the low gravity space environment compared to one-gravity of earth, and (3) determine feasibility of joining metals in space. The experiment used the electron beam (EB) and chamber of the M512 apparatus to make a dwell puddle and a melt in a rotating disc of varying thickness. Hence, the EB performed cut-through, full and partial penetration melts, in addition to a resolidified button. The three disc materials were aluminum 2219-T87, 304 stainless steel, and pure tantalum to provide a wide range of density and melting conditions. Observations to date include the proof that EB welding, cutting, and melting can be done successfully in low gravity. Earlier, some welding authorities had postulated that without gravity the EB would force the molten puddle out of contact. However, the experiment proved that surface tension forces predominate. From the viewpoint of cast-solidification, small, equiaxed grains in Skylab specimens compared to large, elongated grains in ground based specimens were observed. The former are thought to be associated with constitutional supercooling and nucleation where the latter are associated with dendritic solidification. In further support of the more equiaxed grain growth in Skylab, symmetric subgrain patterns were frequently observed where there was much less symmetry in ground based specimens.

Poorman, R. M.

1975-01-01

103

Testing the symmetrization postulate of quantum mechanics and the spin-statistics connection  

E-print Network

Recent experimental tests of the symmetrization postulate of quantum mechanics are discussed. It is shown that in a strict sense these experiments cannot test the validity of the symmetrization postulate, but in most cases do test the spin-statistics connection. An experiment is proposed that would allow to search for possible violations of the symmetrization postulate.

G. M. Tino

1999-07-08

104

Translating Koch's postulates to identify matrix metalloproteinase roles in postmyocardial infarction remodeling: cardiac metalloproteinase actions (CarMA) postulates.  

PubMed

The first matrix metalloproteinase (MMP) was described in 1962; and since the 1990s, cardiovascular research has focused on understanding how MMPs regulate many aspects of cardiovascular pathology from atherosclerosis formation to myocardial infarction and stroke. Although much information has been gleaned by these past reports, to a large degree MMP cardiovascular biology remains observational, with few studies homing in on cause and effect relationships. Koch's postulates were first developed in the 19th century as a way to establish microorganism function and were modified in the 20th century to include methods to establish molecular causality. In this review, we outline the concept for establishing a similar approach to determine causality in terms of MMP functions. We use left ventricular remodeling postmyocardial infarction as an example, but this approach will have broad applicability across both the cardiovascular and the MMP fields. PMID:24577966

Iyer, Rugmani Padmanabhan; de Castro Brás, Lisandra E; Jin, Yu-Fang; Lindsey, Merry L

2014-02-28

105

The effects of sulfur, silicon, water, and oxygen fugacity on carbon solubility and partitioning in Fe-rich alloy and silicate melt systems at 3 GPa and 1600 °C: Implications for core-mantle differentiation and degassing of magma oceans and reduced planetary mantles  

NASA Astrophysics Data System (ADS)

The partition coefficient of carbon between Fe-rich alloy melt and silicate melt, DCmetal/silicate and solubility of C-O-H volatiles in reduced silicate melts are key parameters that need to be quantified in order to constrain the budget and origin of carbon in different planetary reservoirs and subsequent evolution of volatiles in magma oceans (MO) and silicate mantles. In this study, three sets of graphite-saturated experiments have been performed at 3 GPa and 1600 °C to investigate the effects of oxygen fugacity (fO2), sulfur, silicon, and water on the dissolution and partitioning of carbon between Fe-rich alloy melt and silicate melt. The results show that the presence of 0-5 wt% sulfur in alloy melt does not have considerable effect on carbon solubility (?5.6 wt%) in alloy melt, determined by electron microprobe, whereas the presence of 0-10 wt% silicon decreases the carbon solubility from ?5.6 wt% to 1.8 wt%. Carbon solubility (11-192 ppm) in silicate melt, determined by SIMS, is strongly controlled by fO2 and the bulk water content. Decreasing log ? fO2 from IW-0.6 to IW-4.7 or increasing bulk water content from 0.07 to 0.55 wt% results in significant increase of carbon solubility in silicate melt. Raman and FTIR spectroscopic analyses of silicate glasses show that the carbon species is mostly methane, which is further confirmed by the strong, positive correlation between the non-carbonate carbon and non-hydroxyl hydrogen in silicate melt. The DCmetal/silicate ranging from 180 to 4600 decreases with decreasing fO2 or increasing bulk water in silicate melt. In addition, increasing Si in alloy melt also decreases DCmetal/silicate. Our results demonstrate that fO2 and bulk water contents in silicate melt play an important role in determining the fractionation of carbon in planetary MO. A reduced, hydrous MO may have led to a considerable fraction of carbon retained in the silicate mantle, whereas an oxidized, dry MO may have lost almost its entire carbon into the core. If delivery of bulk Earth carbon predominantly occurred after >90% of accretion, i.e., in a relatively oxidized MO (IW-2 to IW-1), then with applicable DCmetal/silicate > 1000, most early Earth carbon would also enter the segregating core. Finally, the predominance of methane in reduced silicate melt with fO2 below IW-1 also indicates that degassing of a hydrous, solidifying MO may have created a reduced early atmosphere, and degassing from lunar and Martian mantle may have released much more methane than carbon dioxide.

Li, Yuan; Dasgupta, Rajdeep; Tsuno, Kyusei

2015-04-01

106

Economic Analysis of a Postulated space Tourism Transportation System  

NASA Astrophysics Data System (ADS)

Design concepts and associated costs were defined for a family of launch vehicles supporting a space tourism endeavor requiring the weekly transport of space tourists to and from an Earth- orbiting facility. The stated business goal for the Space Tourist Transportation System (STTS) element of the proposed commercial space venture was to transport and return ~50 passengers a week to LEO at a cost of roughly 50 K per seat commencing in 2005. This paper summarizes the economic analyses conducted within a broader Systems Engineering study of the postulated concept. Parametric costs were derived using TransCostSystems' (TCS) Cost Engineering Handbook, version 7. Costs were developed as a function of critical system characteristics and selected business scenarios. Various economic strategies directed toward achieving a cost of ~50 K per seat were identified and examined. The study indicated that with a `nominal' business scenario, the initial cost for developing and producing a fully reusable, 2-stage STTS element for a baseline of 46-passengers was about 15.5 B assuming a plausible `commercialization factor' of 0.333. The associated per-seat ticket cost was ~890 K, more than an order of magnitude higher than desired. If the system is enlarged to 104 passengers for better efficiency, the STTS initial cost for the nominal business scenario is increased to about 19.8 B and the per-seat ticket cost is reduced to ~530 K. It was concluded that achieving the desired ticket cost of 50 K per seat is not feasible unless the size of the STTS, and therefore of the entire system, is substantially increased. However, for the specified operational characteristics, it was shown that a system capacity of thousands of passengers per week is required. This implies an extremely high total system development cost, which is not very realistic as a commercial venture, especially in the proposed time frame. These results suggested that ambitious commercial space ventures may have to rely on sizeable government subsidies for economic viability. For example, in this study a hypothesized government subsidy of half the STTS development cost reduced the per-seat ticket cost by about 35%. A number of other business scenarios were also investigated, including `expensing' the entire program initial cost. These analyses showed that even greater government participation, additional aggressive business strategies and/or very low commercialization factors (in the range of 1/9 to 1/30) must be implemented or attained to achieve the desired per-seat cost of 50 K per passenger with reasonably sized vehicles.

Hill, Allan S.

2002-01-01

107

Recent melt rates of Canadian arctic ice caps are the highest in four millennia  

NASA Astrophysics Data System (ADS)

There has been a rapid acceleration in ice-cap melt rates over the last few decades across the entire Canadian Arctic. Present melt rates exceed the past rates for many millennia. New shallow cores at old sites bring their melt series up-to-date. The melt-percentage series from the Devon Island and Agassiz (Ellesmere Island) ice caps are well correlated with the Devon net mass balance and show a large increase in melt since the middle 1990s. Arctic ice core melt series (latitude range of 67 to 81 N) show the last quarter century has had the highest melt in two millennia and The Holocene-long Agassiz melt record shows that the last 25 years has the highest melt in 4200 years. The Agassiz melt rates since the middle 1990s resemble those of the early Holocene thermal maximum over 9000 years ago.

Fisher, David; Zheng, James; Burgess, David; Zdanowicz, Christian; Kinnard, Christophe; Sharp, Martin; Bourgeois, Jocelyne

2012-03-01

108

Testing the Symmetrization Postulate of Quantum Mechanics and the Spin-Statistics Connection  

Microsoft Academic Search

Recent experimental tests of the symmetrization postulate of quantum\\u000amechanics are discussed. It is shown that in a strict sense these experiments\\u000acannot test the validity of the symmetrization postulate, but in most cases do\\u000atest the spin-statistics connection. An experiment is proposed that would allow\\u000ato search for possible violations of the symmetrization postulate.

Guglielmo M. Tino

2000-01-01

109

Laser experiments producing melt  

Microsoft Academic Search

An initiative is underway at the Omega, Vulcan and Helen lasers to produce and detect melt transitions in targets using decaying shock waves. We present data and analysis for experiments performed at Vulcan and Helen to detect melt in Al, Pb and Fe. We show an analytic study and of diamond melt experiments performed at the Omega laser. For the

Jon Eggert; David Bradley; Damien Hicks; Steve Moon; Gilbert Collins; Peter Celliers; Jave Kane; Walter Unites; Tom Beat; Alan Jankowski; Jeff Hayes; Steve Rothman; Andrew Evans

2002-01-01

110

6.2. Pure death processes 6.2.1. Postulates of pure death processes.  

E-print Network

45 6.2. Pure death processes 6.2.1. Postulates of pure death processes. {X(t) : t [0, )} is called a pure death process with parameters µ0 = 0, µ1, ..., µN , and state space {0, 1, ..., N are equivalent, but Postulate 2 is incomplete and cannot be considered as a definition for pure death process. 6

Chen, Kani

111

Melting of peridotite to 140 gigapascals.  

PubMed

Interrogating physical processes that occur within the lowermost mantle is a key to understanding Earth's evolution and present-day inner composition. Among such processes, partial melting has been proposed to explain mantle regions with ultralow seismic velocities near the core-mantle boundary, but experimental validation at the appropriate temperature and pressure regimes remains challenging. Using laser-heated diamond anvil cells, we constructed the solidus curve of a natural fertile peridotite between 36 and 140 gigapascals. Melting at core-mantle boundary pressures occurs at 4180 ± 150 kelvin, which is a value that matches estimated mantle geotherms. Molten regions may therefore exist at the base of the present-day mantle. Melting phase relations and element partitioning data also show that these liquids could host many incompatible elements at the base of the mantle. PMID:20847269

Fiquet, G; Auzende, A L; Siebert, J; Corgne, A; Bureau, H; Ozawa, H; Garbarino, G

2010-09-17

112

Melt segregation in migmatites  

NASA Astrophysics Data System (ADS)

Anatectic stromatic migmatites have a symmetrical layered structure with a low ratio of thickness to length and a periodicity, features that have not been explained satisfactorily but which are related to physical processes of melt segregation. We evaluate the compaction model for segregation as it applies to migmatites and develop models for melt segregation based upon convection driven by volume change and upon advection down pressure gradients that result from applied differential stress acting on an anisotropic multilayer protolith. Compaction by gravity-driven two-phase flow results in asymmetric separation, yields calculated segregation times that are slow or geologically unreasonable, and yields relative volumes that are not consistent with the abundance of leucosome seen in natural migmatites. Although calculated segregation times for "very wet" granite might allow segregation by compaction, some driving force in addition to gravity is needed to cause widespread melt segregation in the crust. For segregation at low volume fraction of melt, we develop a two-dimensional two-phase (matrix and fluid) viscous flow cell model (length much greater than thickness) with phase changes which predicts either expansion or contraction convection (depending on whether volume change, ?Vr, is positive or negative). Convection leads to melt segregation to form a stromatic structure in a geologically reasonable timescale. At moderate volume fraction of melt, segregation may occur by filter pressing in compositionally layered rocks in response to applied differential stress. Melt migration is by porous medium flow driven by differences in mean normal stress between the layers, as a consequence of differences in rheology, and shear-enhanced matrix collapse. Calculated segregation rates are fast, and the model yields adequate volume of leucosome. The positive ?Vr for volatile phase-absent melting reactions under crustal pressures promotes melt escape, unless extensional deformation facilitates melt accumulation. If the rate of melt production exceeds the rate of melt escape, then the increase in melt pressure may lead to melt-enhanced embrittlement and fracture, and melt may migrate out of the system. In contrast, water-rich volatile phase-present melt-producing reactions have a negative ?Vr, which promotes melt retention after segregation, unless deformation generates melt escape pathways. Evolution of stromatic structure through anatectic erosion of mesosome by increasing the melt fraction in situ may lead to breakdown of the solid matrix and will lead to instability due to buoyancy, and magma may become mobile and entrain residual material ("restite").

Brown, Michael; Averkin, Yuri A.; McLellan, Eileen L.; Sawyer, Edward W.

1995-08-01

113

Melting in the Fe-Ni system  

NASA Astrophysics Data System (ADS)

The melting temperature of the Fe-rich core alloy at the inner core boundary (ICB) condition of 330 GPa is a key geophysical parameter because it represents an anchor point on the geotherm. An accurate knowledge of the melting curves of candidate alloys is therefore highly desirable. In spite of this, there is still considerable uncertainty in the melting point even of pure Fe at these conditions; estimates range from as low as 4850K based on one laser heated diamond anvil cell (LHDAC) study [1] to as high as 6900K based on recent quantum Monte Carlo calculations [2]. In reality we expect that the bulk core alloy may contain 5-10 wt% Ni (based on cosmochemical and meteoritic arguments) and up to 10 wt% of an as yet undetermined mix of light elements (with Si, S, C and O being the most likely candidates). While some recent studies have looked at the effects of light elements on the melting curve of Fe [e.g.: 3,4] with some of these studies including a small amount of Ni in their starting material, to date there has been no systematic study of melting temperatures in the Fe-Ni system. To address this issue, we have embarked upon just such a study. Using the LHDAC we have determined the melting curve of the pure Ni end-member to 180 GPa, and that of pure Fe to 50 GPa, using perturbations in the power vs. temperature function as the melting criterion [5]. Ar or NaCl were employed as pressure media while temperature was measured using standard spectroradiometric techniques [6]. In the case of Ni, perturbations were observed for both the sample and the Ar medium, allowing us to determine the melting curve of Ar and Ni simultaneously. Our results thus far for Ni and Ar agree closely with all of the available data, while extending the melting curves by a factor of two in pressure. In the case of Fe, our current dataset is also in good agreement with previous studies [2,7]. The agreement of all three melting curves with the literature data as well as other materials previously tested [see 5] gives us confidence in the accuracy of our techniques. In the case of Ni, we observe no change in slope, strongly suggesting that Ni remains in the fcc structure to inner core conditions, as opposed to Fe, which converts to the hcp structure at 60-100 GPa. Below this pressure, the Fe and Ni melting curves are nearly indistinguishable, but above it the Fe melting curve becomes much steeper, such that by 330 GPa, the difference between the two is 1500-3600K depending on which iron melting curve is chosen from the literature [1,2]. The addition of Ni to Fe expands the fcc field and pushes the fcc-hcp-liquid triple point to higher pressures [e.g.: 8] delaying the point at which the melting curve begins to steepen, which could lead to a significant melting point depression at the ICB. We hope to present additional data at the meeting to test this hypothesis, including further data on pure Fe, as well as one or more intermediate alloy compositions (up to 200 GPa). [1] Boehler, R. (1993). Nature 363, 534-536 [2] Alfè, D. & Sola, E. (2009). PRL 103, 078501 [3] Morard, G. et al. (2011). PCM 38, 767-776. [4] Asanuma, H. et al. (2010). PCM 37, 353-359. [5] Lord, O. T. et al. (2010). JGR 115, B06208. [6] Walter, M. J. & Koga, K. T. (2004). PEPI. 143-144, 541-558. [7] Shen, G. et al. (1998). GRL 25, 373-376. [8] Kuwayama, Y. et al. (2008). EPSL, 273, 379-385.

Lord, O. T.; Walter, M. J.; Vocadlo, L.; Wood, I. G.; Dobson, D. P.

2012-12-01

114

Experimental studies on melting Earth's lower mantle minerals  

NASA Astrophysics Data System (ADS)

Melting in Earth's lower mantle and its phase relations during melting has great implications for many geophysical processes and the thermochemical evolution of the planet including: magma ocean crystallization, ultralow velocity zones, and core formation. Due to experimental and theoretical challenges, these properties are poorly constrained. In this study, we take advantage of several new techniques to better constrain melting temperatures of lower mantle minerals and their phase relations. Combining two-dimensional, 4-color temperature mapping (Campbell, 2008) during flash heating (Yang et al., 2012), with ex-situ SEM/BSE images (Du et al., 2013), we are able to accurately measure the melting temperatures of lower mantle minerals and assemblages.

Du, Z.; Lee, K. K.

2013-12-01

115

Melt containment member  

SciTech Connect

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

Rieken, Joel R.; Heidloff, Andrew J.

2014-09-09

116

Modeling energy balance and melt layer formation on the Kahiltna Glacier, Alaska  

Microsoft Academic Search

Understanding melt on alpine glaciers is required both for accurate mass balance modeling and ice core paleoclimate reconstruction. In alpine regions with complex meteorology and topography, modeling melt through the quantification and balance of all identifiable energy fluxes is the most complete way of describing how local meteorology influences melt layer formation and snowpack evolution. To meet this goal at

D. A. Winski; K. J. Kreutz; E. C. Osterberg; S. W. Campbell

2010-01-01

117

Experimental melting curve of iron revisited  

NASA Astrophysics Data System (ADS)

With new experimental data presented in the last 2 years, it becomes possible to resolve conflicts in the data sets used in constructing the melting curve of iron, Tm(P). On the basis of these new data, several data sets have been dropped: the Williams et al. [1987] melting curve up to 100 GPa and the Bass et al [1987] and Yoo et al. [1993] shock-wave-derived Tm(P) in the 200-300 GPa range based on light emissivity measurements. The Boehler [1993] Tm(P) curve to 200 GPa and the Brown and McQueen [1986] shock-wave-determined Tm(240) remain, leaving a gap between 240 and 330 GPa. We fill this gap using the Lindemann law of melting. The Lindemann law and the temperature values along the Brown and McQueen [1986] Hugoniot require the value of the Grüneisen ratio, ?; thus ? connects Tm at 330 GPa with Tm found for values of the Hugoniot. It is further shown that the heat of crystallization, ?Hm, is dependent on ?. Thus, through 7, a connection is made between the melting curve and the power generated within the inner core. The effect of all these connections of physical properties through ? leads us to recommend 5600-6500 K as the Tm of iron at inner-outer core boundary conditions. Though argument continues concerning the amount and nature of alloying elements, there remains little ground for doubting that both inner and outer cores consist mainly of iron.

Anderson, Orson L.; Duba, Al

1997-10-01

118

Derivation of the postulates of quantum mechanics from the first principles of scale relativity  

E-print Network

Quantum mechanics is based on a series of postulates which lead to a very good description of the microphysical realm but which have, up to now, not been derived from first principles. In the present work, we suggest such a derivation in the framework of the theory of scale relativity. After having analyzed the actual status of the various postulates, rules and principles that underlie the present axiomatic foundation of quantum mechanics (in terms of main postulates, secondary rules and derived `principles'), we attempt to provide the reader with an exhaustive view of the matter, by both gathering here results which are already available in the literature, and deriving new ones which complete the postulate list.

Laurent Nottale; Marie-Noëlle Célérier

2007-11-15

119

Postulated Human Sperm Count Decline May Involve Historic Elimination of Juvenile Iodine Deficiency: A New Hypothesis  

E-print Network

Postulated Human Sperm Count Decline May Involve Historic Elimination of Juvenile Iodine Deficiency, historic dietary iodination, and an animal model where neonatal goitrogen administration causes counts. We present the hypothesis with a supporting study extending the model to include iodine

Hess, Rex A.

120

The Relationship between Lattice Enthalpy and Melting Point in Magnesium and Aluminium Oxides. Science Notes  

ERIC Educational Resources Information Center

This "Science Note" presents a study by Christopher Talbot and Lydia Yap, who teach IB Chemistry at Anglo-Chinese School (Independent), Republic of Singapore, to pre-university students. Pre-university students may postulate the correlation between the magnitude of the lattice enthalpy compound and its melting point, since both…

Talbot, Christopher; Yap, Lydia

2013-01-01

121

Ash melting treatment by rotating type surface melting furnace  

Microsoft Academic Search

Results of melting treatment of fly ash from municipal solid waste incinerators are described, and safety and an effective use of slag discharged from the melting treatment are studied. The fly ash has an average particle size of 22 ?m and a melting fluidity point of 1280–1330°C and was able to be melted by using a Kubota melting furnace without

Sei-ichi Abe; Fumiaki Kambayashi; Masaharu Okada

1996-01-01

122

Melting as a dislocation-mediated phase transition  

SciTech Connect

We present a theory of the melting of elements as a dislocation-mediated phase transition. We model dislocations near the melt as noninteracting closed loops on a lattice. In this framework we derive simple expressions for the melting temperature and latent heat of fusion that depend on the dislocation density at melt. We use experimental data for more than half the elements in the periodic table to determine the dislocation density from both relations. Melting temperatures yield a dislocation density of (0.61{+-}0.20)b{sup -2}, in good agreement with the density obtained from latent heats, (0.66{+-}0.11)b{sup -2}, where b is the length of the smallest perfect-dislocation Burgers vector. Melting corresponds to the situation where, on average, half of the atoms are within a dislocation core. (c) 2000 The American Physical Society.

Burakovsky, Leonid [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Preston, Dean L. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Silbar, Richard R. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2000-06-01

123

Melting Glaciers Threaten Peru  

NSDL National Science Digital Library

Thousands of people in the Andes mountains of Peru are having their lives affected in both a practical and cultural way by climate change, which is causing the region's glaciers to melt. This document explores the causes of the glacial melt and its impacts on the local cultures.

2003-10-09

124

Melting experiments on peridotite to lowermost mantle conditions  

NASA Astrophysics Data System (ADS)

Melting experiments on a pyrolitic mantle material were performed in a pressure range from 34 to 179 GPa based on laser-heated diamond-anvil cell (DAC) techniques. The textural and chemical characterizations of quenched samples were made by using field-emission-type electron microprobe (FE-EPMA). Melts formed by 46 to 77 wt.% partial melting in this study were ultrabasic in composition and became more depleted in SiO2 and more enriched in FeO with increasing pressure. Melting textures indicate that the liquidus phase changed from ferropericlase to MgSiO3-rich perovskite at least above 34 GPa and further to post-perovskite. The first phase to melt (disappear) changed from CaSiO3 perovskite to (Mg,Fe)O ferropericlase between 68 and 82 GPa. The stability of ferropericlase above solidus temperature shrinks with increasing pressure (melting last below 34 GPa and first 82 GPa), resulting in higher (MgO + FeO)/SiO2 ratio in partial melt at higher pressure. Additionally, the Fe-Mg distribution coefficients (KD) between perovskite/post-perovskite and melt decreased considerably with increasing pressure, leading to strong Fe-enrichment in partial melts. It supports dense partial melts in a deep lower mantle, which migrate downward to the core mantle boundary (CMB).

Tateno, Shigehiko; Hirose, Kei; Ohishi, Yasuo

2014-06-01

125

Molybdenum Valence in Basaltic Silicate Melts  

NASA Technical Reports Server (NTRS)

The moderately siderophile element molybdenum has been used as an indicator in planetary differentiation processes, and is particularly relevant to core formation [for example, 1-6]. However, models that apply experimental data to an equilibrium differentiation scenario infer the oxidation state of molybdenum from solubility data or from multivariable coefficients from metal-silicate partitioning data [1,3,7]. Partitioning behavior of molybdenum, a multivalent element with a transition near the J02 of interest for core formation (IW-2) will be sensitive to changes in JO2 of the system and silicate melt structure. In a silicate melt, Mo can occur in either 4+ or 6+ valence state, and Mo6+ can be either octahedrally or tetrahedrally coordinated. Here we present first XANES measurements of Mo valence in basaltic run products at a range of P, T, and JO2 and further quantify the valence transition of Mo.

Danielson, L. R.; Righter, K.; Newville, M.; Sutton, S.; Pando, K.

2010-01-01

126

Plasma Melting Technology and Applications  

NASA Astrophysics Data System (ADS)

A plasma arc melter is a modular high-intensity skull melter capable of rapidly melting a wide variety of materials, both conductive and nonconductive. Although its commercial use to melt and process metals is well known, the method is less well known as a method of melting glass. Extensive research has been conducted by several organizations into the use of skull melting of glass using plasma arcs. This research has shown plasma melting to be a promising technology that can achieve high efficiencies, high temperatures, extreme flexibility, low capital cost, rapid changeovers of glass formulas, and minimal scrap. Plasma melting lends itself to modular melting in which each step of the glass melting process is partitioned into functional modules, which can greatly improve melting efficiency and throughput. Also, plasma arc melting has been shown to be a promising technology for rapidly and inexpensively producing "synthetic minerals" melted from common commercial oxides.

Gonterman, J. Ronald; Weinstein, M. A.

127

Dislocation theory of melting for iron, revisited  

SciTech Connect

Melting point T{sub m} of iron at conditions of the Earth`s inner core boundary (ICB) has been calculated from dislocation theory of melting in metals. Monte Carlo calculations were used to estimate uncertainties introduced by uncertainty in the geophysical parameters that are used in the calculations. These calculations take into account the effects of pressure at ICB conditions and of possible freezing point depression resulting from dilution of pure iron in the outer core. With this approach T{sub m} of pure {var_epsilon}-Fe at a pressure of 330 GPa and without freezing point depression is 6160 {plus_minus} 250 K; for a 1000 K freezing point depression it is 6110 K. T{sub m} of pure {gamma}-Fe is 6060 K, a value that is not significantly different. A possible {alpha}{prime} phase would melt at 5600 K. These values agree with calculated shock wave determinations of T{sub m}. Although calculated T{sub m} of the pure phase is little affected by assumptions about the extent of freezing point depression, the estimated temperature of the inner core boundary is lower by the breezing point depression, perhaps 500--1000 K less than T{sub m} of a pure phase.

Poirier, J.P. [Inst., de Physique du Globe de Paris (France); Shankland, T.J. [Los Alamos National Lab., NM (United States)

1993-11-01

128

Dislocation theory of melting for iron, revisited  

SciTech Connect

The melting point T[sub m] of iron at conditions of the Earth's inner core boundary (ICB) has been calculated from the dislocation theory of melting in metals. Monte Carlo calculations were used to estimate uncertainties introduced by uncertainty in the geophysical parameters that are used in the calculations. These calculations take into account the effects of pressure at ICB conditions and of possible freezing point depression resulting from dilution of pure iron in the outer core. With this approach T[sub m] of pure [epsilon]-Fe at a pressure of 330 GPa and without freezing point depression is 6160[plus minus]250 K; for a 1000 K freezing point depression it is 6110 K. T[sub m] of pure [gamma]-Fe is 6060 K, a value that is not significantly different. A possible [alpha][prime] phase would melt at 5600 K. These values agree with calculated shock wave determinations of T[sub m]. Although calculated T[sub m] of the pure phase is little affected by assumptions about the extent of freezing point depression, the estimated temperature of the inner core boundary is lower by the freezing point depression, perhaps 500--1000 K less than T[sub m] of a pure phase. [copyright] 1994 American Institute of Physics

Poirier, J. (Departement des Geomateriaux, Institut de Physique du Globe de Paris, 75252 Paris Cedex 05 (France)); Shankland, T.J. (Earth and Environmental Sciences Division, MS D443, Los Alamos National Laboratory, Los Alamos, New Mexico 84545 (United States))

1994-07-10

129

What does it take to satisfy Koch's postulates two centuries later? Microbial genomics and Propionibacteria acnes.  

PubMed

For two centuries, Koch's postulates have set the gold standard for establishing the microbiological etiology of infection and disease. Genomic sequencing now brings finer resolution to both bacterial strain variation and the host genetic state that may predispose to disease. In this issue of the JID, Fitz-Gibbons and colleagues present strain-based resolution of Propionibacterium acnes and its association with the common teenage malady acne vulgaris. Here I examine how Koch's postulates were envisioned and incorporate this finer resolution of both host and microbial states. PMID:23842116

Segre, Julia A

2013-09-01

130

Reactive melt migration in mantle rocks: an experimental study  

NASA Astrophysics Data System (ADS)

Several physical and chemical driving forces are important during the segregation and focusing of melt from a partially molten mantle toward a mid-oceanic spreading center. We performed a series of experiments to investigate the coupling between stress-driven and reaction-driven melt segregation. A core of melt-rich source material containing olivine, chromite and 20 vol% alkali basalt was placed within a ring of melt-poor sink containing olivine, enstatite, chromite and 4 vol% of alkali basalt. The gradient in silica activity at the source-sink interface provides a chemical driving force for melt migration. These source-sink couples were deformed in torsion in a gas-medium deformation apparatus at 1200°C, 300 MPa confining pressure and shear strain rates of ~10-4 s-1 to different finite shear strains (? = 0 - 5). Microstructural observations of tangential sections show that at low strains (? ? 2) melt aligns along grain boundaries in the sink at ~45° antithetic to the shear plane (parallel to ?1). At higher strains (? > 3.5), melt-rich bands develop at 0 to 20° antithetic to the shear direction with a mean spacing between bands of 100 to 250 ?m. The melt-rich bands contain 20 - 30% melt in the form of individual melt pockets (dequ ? 2.5 ?m) aligned 10 - 45° with respect to the applied shear. Typically, a band contains 2 to 10 euhedral to rounded, small, mostly olivine grains (dequ ? 3 ?m) almost entirely surrounded by melt. Bands terminate at melt-depleted lenses (< 1 vol% melt) in a zone 2 - 4 grains wide containing ~2 vol% melt in small (?1 ?m) pockets. Melt-rich zones do not develop in the sink at the source-sink interface after annealing a sample hydrostatically for >9 h. However, once melt bands are well developed by stress-driven melt segregation (? ? 3.5) dissolution of enstatite reaches ~200 ?m into the sink from the source-sink interface. For the pressure-temperature conditions and timescales of our experiments, the observations indicate that segregation of melt is driven by a combination of deformation and chemical driving forces and not by chemical driving force alone.

Pec, M.; Kohlstedt, D. L.; Zimmerman, M. E.; Holtzman, B. K.

2013-12-01

131

Development of a fuel-rod simulator and small-diameter thermocouples for high-temperature, high-heat-flux tests in the Gas-Cooled Fast Reactor Core Flow Test Loop  

SciTech Connect

The Core Flow Test Loop was constructed to perform many of the safety, core design, and mechanical interaction tests in support of the Gas-Cooled Fast Reactor (GCFR) using electrically heated fuel rod simulators (FRSs). Operation includes many off-normal or postulated accident sequences including transient, high-power, and high-temperature operation. The FRS was developed to survive: (1) hundreds of hours of operation at 200 W/cm/sup 2/, 1000/sup 0/C cladding temperature, and (2) 40 h at 40 W/cm/sup 2/, 1200/sup 0/C cladding temperature. Six 0.5-mm type K sheathed thermocouples were placed inside the FRS cladding to measure steady-state and transient temperatures through clad melting at 1370/sup 0/C.

McCulloch, R.W.; MacPherson, R.E.

1983-03-01

132

Using Pliocene palaeoclimatic data to postulate dispersal pathways of early hominins  

Microsoft Academic Search

A Geographic Information System (GIS) simulation is used here to test postulated early hominin expansions into Eurasia. To understand fully Plio–Pleistocene hominin dispersals, that is the increasing geographic range of hominins, a number of interacting factors must be examined. The most important variables affecting the first hominin dispersals would have been environmental, and it is thus imperative that appropriate climatic

Kathryn M. Holmes

2007-01-01

133

Mining MEDLINE: Postulating a Beneficial Role for Curcumin Longa in Retinal Diseases  

E-print Network

Mining MEDLINE: Postulating a Beneficial Role for Curcumin Longa in Retinal Diseases Padmini supporting the suggested connection between curcumin and retinal diseases. In particular, curcumin influ, the evidence suggests that curcumin may have a beneficial and therapeutic role in the context of these dis

Srinivasan, Padmini

134

A Postulated Mechanism That Leads to Materialization and Dematerialization of Matter and to Antigravity.  

ERIC Educational Resources Information Center

This document presents a discussion of the postulated mechanism that leads to the materialization and dematerialization of matter and to antigravity. The mechanism also explains why an orbital electron does not radiate energy, in contradiction to classical electromagnetic theory. One of the paradoxes of special relativity is explained. A new model…

Bearden, Thomas E.

135

Sequence-based identification of microbial pathogens: a reconsideration of Koch's postulates.  

PubMed Central

Over 100 years ago, Robert Koch introduced his ideas about how to prove a causal relationship between a microorganism and a disease. Koch's postulates created a scientific standard for causal evidence that established the credibility of microbes as pathogens and led to the development of modern microbiology. In more recent times, Koch's postulates have evolved to accommodate a broader understanding of the host-parasite relationship as well as experimental advances. Techniques such as in situ hybridization, PCR, and representational difference analysis reveal previously uncharacterized, fastidious or uncultivated, microbial pathogens that resist the application of Koch's original postulates, but they also provide new approaches for proving disease causation. In particular, the increasing reliance on sequence-based methods for microbial identification requires a reassessment of the original postulates and the rationale that guided Koch and later revisionists. Recent investigations of Whipple's disease, human ehrlichiosis, hepatitis C, hantavirus pulmonary syndrome, and Kaposi's sarcoma illustrate some of these issues. A set of molecular guidelines for establishing disease causation with sequence-based technology is proposed, and the importance of the scientific concordance of evidence in supporting causal associations is emphasized. PMID:8665474

Fredericks, D N; Relman, D A

1996-01-01

136

INTRODUCTION Cryptomonad algae are postulated to be a chimaera of two  

E-print Network

INTRODUCTION Cryptomonad algae are postulated to be a chimaera of two different eukaryotic cells incorporating cryptomonad endosymbiont gene sequences ally them loosely with red algae (Douglas et al., 1991a that the endosymbiont was an early evolutionary intermediate that pre-dates the red algae (Cavalier-Smith, 1992

McFadden, Geoff

137

An Inexpensive and Safe Experiment to Demonstrate Koch's Postulates Using Citrus Fruit  

ERIC Educational Resources Information Center

Citrus fruit (oranges, tangerines, grapefruit or lemons) purchased in a grocery store can be experimentally infected with readily-available sources of "Penicillium digitatum" to demonstrate the four basic steps of Koch's postulates, also known as proof of pathogenicity. The mould is isolated from naturally-infected citrus fruit into pure culture…

Jakobi, Steven

2010-01-01

138

Ramanujan and Erdos Two Proofs of Bertrand's Postulate March 23, 2012  

E-print Network

conjectured the following postulate in 1845 after testing it for numbers till three million:1 For every n, and derives a contradiction. Ramanujan's proof, on the other hand, not only shows the existence of primes we see that the term attains its minimum at the point x = k/(n - k). Since the value attained

Sharma, Vikram

139

Fun Microbiology: Using a Plant Pathogenic Fungus To Demonstrate Koch's Postulates.  

ERIC Educational Resources Information Center

Describes an experiment using a plant pathogenic fungus in which students learn to follow aseptic techniques, grow and produce spores of a fungus, use a hemacytometer for enumerating spores, prepare serial dilutions, grow and inoculate plants, isolate a pure culture using agar streak plates, and demonstrate the four steps of Koch's postulates.…

Mitchell, James K.; Orsted, Kathy M.; Warnes, Carl E.

1997-01-01

140

Transient security dispatch for the concurrent optimization of plural postulated contingencies  

Microsoft Academic Search

The implementation. of a transient security dispatch (TSD) algorithm for real-time applications is presented. The algorithm, based on the generalized reduced gradient (GRG) method, processes collectively a set of contingencies in order to ensure transient stability for all postulated cases. The massive computation has been decomposed on a cluster of workstations, exploiting the decoupled nature of the GRG method and

Sergio Bruno; E. De Tuglie; M. La Scala

2002-01-01

141

Maxwell's macroscopic equations, the energy-momentum postulates, and the Lorentz law of force.  

PubMed

We argue that the classical theory of electromagnetism is based on Maxwell's macroscopic equations, an energy postulate, a momentum postulate, and a generalized form of the Lorentz law of force. These seven postulates constitute the foundation of a complete and consistent theory, thus eliminating the need for actual (i.e., physical) models of polarization P and magnetization M , these being the distinguishing features of Maxwell's macroscopic equations. In the proposed formulation, P(r,t) and M(r,t) are arbitrary functions of space and time, their physical properties being embedded in the seven postulates of the theory. The postulates are self-consistent, comply with the requirements of the special theory of relativity, and satisfy the laws of conservation of energy, linear momentum, and angular momentum. One advantage of the proposed formulation is that it sidesteps the long-standing Abraham-Minkowski controversy surrounding the electromagnetic momentum inside a material medium by simply "assigning" the Abraham momentum density E(r,t)xH(r,t)/c2 to the electromagnetic field. This well-defined momentum is thus taken to be universal as it does not depend on whether the field is propagating or evanescent, and whether or not the host medium is homogeneous, transparent, isotropic, dispersive, magnetic, linear, etc. In other words, the local and instantaneous momentum density is uniquely and unambiguously specified at each and every point of the material system in terms of the E and H fields residing at that point. Any variation with time of the total electromagnetic momentum of a closed system results in a force exerted on the material media within the system in accordance with the generalized Lorentz law. PMID:19391864

Mansuripur, Masud; Zakharian, Armis R

2009-02-01

142

The role of von Neumann and Lüders postulates in the EPR-Bohm-Bell considerations: Did EPR make a mistake?  

E-print Network

We show that the projection postulate plays a crucial role in the discussion on the so called "quantum nonlocality", in particular in the EPR-argument. We stress that the original von Neumann projection postulate was crucially modified by extending it to observables with degenerate spectra (the L\\"uders postulate) and we show that this modification is highly questionable from a physical point of view, and it is the real source of "quantum nonlocality". The use of the original von Neumann postulate eliminates this problem: instead of "action at the distance"-nonlocality, we obtain a classical measurement nonlocality. It seems that EPR did mistake in their 1935-paper: if one uses correctly von Neumann projection postulate, no ``elements of reality'' can be assigned to entangled systems. Our analysis of the EPR and projection postulate makes clearer Bohr's considerations in his reply to Einstein.

Andrei Khrennikov

2008-06-01

143

Concord Consortium: Melting Ice  

NSDL National Science Digital Library

This activity combines a hands-on lab with a computer simulation, as students investigate and graph the changing temperature of a melting ice cube. In the first step, learners use a sensor to monitor temperature as ice melts in a cup of water. In the second step, the ice cube is melted in a cup of salt water. Interactive graphs allow easy plotting of Temperature vs. Time. The activity concludes with a simulation of the atomic structure of a hot liquid and a cold liquid. Click "Withdraw the Barrier" and watch the changing kinetic energy of the cold liquid particles as they mix with the hot liquid. This item is part of the Concord Consortium, a nonprofit research and development organization dedicated to transforming education through technology.

144

Core-Cutoff Tool  

NASA Technical Reports Server (NTRS)

A tool makes a cut perpendicular to the cylindrical axis of a core hole at a predetermined depth to free the core at that depth. The tool does not damage the surrounding material from which the core was cut, and it operates within the core-hole kerf. Coring usually begins with use of a hole saw or a hollow cylindrical abrasive cutting tool to make an annular hole that leaves the core (sometimes called the plug ) in place. In this approach to coring as practiced heretofore, the core is removed forcibly in a manner chosen to shear the core, preferably at or near the greatest depth of the core hole. Unfortunately, such forcible removal often damages both the core and the surrounding material (see Figure 1). In an alternative prior approach, especially applicable to toxic or fragile material, a core is formed and freed by means of milling operations that generate much material waste. In contrast, the present tool eliminates the damage associated with the hole-saw approach and reduces the extent of milling operations (and, hence, reduces the waste) associated with the milling approach. The present tool (see Figure 2) includes an inner sleeve and an outer sleeve and resembles the hollow cylindrical tool used to cut the core hole. The sleeves are thin enough that this tool fits within the kerf of the core hole. The inner sleeve is attached to a shaft that, in turn, can be attached to a drill motor or handle for turning the tool. This tool also includes a cutting wire attached to the distal ends of both sleeves. The cutting wire is long enough that with sufficient relative rotation of the inner and outer sleeves, the wire can cut all the way to the center of the core. The tool is inserted in the kerf until its distal end is seated at the full depth. The inner sleeve is then turned. During turning, frictional drag on the outer core pulls the cutting wire into contact with the core. The cutting force of the wire against the core increases with the tension in the wire and, hence, with the frictional drag acting on the outer sleeve. As the wire cuts toward the center of the core, the inner sleeve rotates farther with respect to the outer sleeve. Once the wire has cut to the center of the core, the tool and the core can be removed from the hole. The proper choice of cutting wire depends on the properties of the core material. For a sufficiently soft core material, a nonmetallic monofilament can be used. For a rubber-like core material, a metal wire can be used. For a harder core material, it is necessary to use an abrasive wire, and the efficiency of the tool can be increased greatly by vacuuming away the particles generated during cutting. For a core material that can readily be melted or otherwise cut by use of heat, it could be preferable to use an electrically heated cutting wire. In such a case, electric current can be supplied to the cutting wire, from an electrically isolated source, via rotating contact rings mounted on the sleeves.

Gheen, Darrell

2007-01-01

145

Melting Sea Ice  

NSDL National Science Digital Library

This activity uses a mix of multimedia resources and hands-on activities to support a storyline of investigation into melting sea ice. The lesson begins with a group viewing of a video designed to get students to consider both the local and global effects of climate change. The class then divides into small groups for inquiry activities on related topics followed by a presentation of the findings to the entire class. A final class discussion reveals a more complex understanding of both the local and global impacts of melting sea ice.

WGBH Educational Foundation Teachers' Domain

146

Melting Sea Ice  

NSDL National Science Digital Library

This activity uses a mix of multimedia resources and hands-on activities to support a storyline of investigation into melting sea ice. The lesson begins with a group viewing of a video designed to get students to consider both the local and global effects of climate change. The class then divides into small groups for inquiry activities on related topics followed by a presentation of the findings to the entire class. A final class discussion reveals a more complex understanding of both the local and global impacts of melting sea ice.

2007-01-01

147

Translating Koch’s Postulates to Identify Matrix Metalloproteinase Roles in Post-Myocardial Infarction Remodeling: The Cardiac Metalloproteinase Actions (CarMA) Postulates  

PubMed Central

The first matrix metalloproteinase (MMP) was described in 1962; and since the 1990’s, cardiovascular research has focused on understanding how MMPs regulate many aspects of cardiovascular pathology from atherosclerosis formation to myocardial infarction and stroke. While much information has been gleaned by these past reports, to a large degree MMP cardiovascular biology remains observational, with few studies homing in on cause and effect relationships. Koch’s postulates were first developed in the 19th century as a way to establish microorganism function and were modified in the 20th century to include methods to establish molecular causality. In this review, we outline the concept for establishing a similar approach to determine causality in terms of MMP functions. We use left ventricular remodeling post-myocardial infarction as an example, but this approach will have broad applicability across both the cardiovascular and MMP fields. PMID:24577966

Iyer, Rugmani Padmanabhan; de Castro Brás, Lisandra E.; Jin, Yu-Fang; Lindsey, Merry L.

2014-01-01

148

Viscosity Measurement for Tellurium Melt  

NASA Technical Reports Server (NTRS)

The viscosity of high temperature Te melt was measured using a new technique in which a rotating magnetic field was applied to the melt sealed in a suspended ampoule, and the torque exerted by rotating melt flow on the ampoule wall was measured. Governing equations for the coupled melt flow and ampoule torsional oscillation were solved, and the viscosity was extracted from the experimental data by numerical fitting. The computational result showed good agreement with experimental data. The melt velocity transient initiated by the rotating magnetic field reached a stable condition quickly, allowing the viscosity and electrical conductivity of the melt to be determined in a short period.

Lin, Bochuan; Li, Chao; Ban, Heng; Scripa, Rosalia N.; Su, Ching-Hua; Lehoczky, Sandor L.

2006-01-01

149

Thermoacoustic Streaming and Ultrasonic Processing of Low Melting Melts  

NASA Technical Reports Server (NTRS)

Ultrasonic levitation allows the processing of low melting materials both in 1 G as well as in microgravity. The free suspension of the melts also facilitates undercooling, permitting the measurements of the physical properties of the metastable liquids.

Trinh, E. H.

1997-01-01

150

Arctic Melt Charlie Zender  

E-print Network

's Greenhouse Effect Thesur face cools by radiating heat energyupward. ©2004, ACIA #12;IMPACTS OF A WARMING Most of the heat energy emitted from the surface is absorbed by greenhouse gases which radiate heat#12;Arctic Melt Charlie Zender Department of Earth System Science University

Zender, Charles

151

Is Greenland Melting?  

NSDL National Science Digital Library

Data-centric activity where students explore the connections between an observable change in the cryosphere and its potential impact in the hydrosphere and atmosphere. Students analyze the melt extents on the Greenland ice sheet from 1992-2003. Students also learn about how scientists collect the data.

Betsy Youngman

152

Melting Mountain Glaciers  

NSDL National Science Digital Library

The world's glaciers are shrinking at alarming rates, and many scientists believe it is due to changes in climate. Dr. Lonnie Thompson of Ohio State University and Dr. Douglas Hardy of UMass-Amherst discuss glaciers and how they melt, and pay special attention to Africa's tallest mountain, Mt. Kilimanjaro. "Changing Planet" is produced in partnership with the National Science Foundation.

NBC Learn

2010-10-07

153

Evolution of the CPT Invariance into a Basic Postulate in Physics  

E-print Network

Einstein-Podolsky-Rosen's paper in 1935 is discussed in parallel with an EPR experiment on $K^0\\bar{K}^0$ system in 1998, yielding a strong hint of distinction in both wave-function and operators between particle and antiparticle at the level of quantum mechanics (QM). Then it is proposed that the CPT invariance in particle physics leads naturally to a basic postulate that the (newly defined) space-time inversion (${\\bf x}\\to -{\\bf x},t\\to -t$) is equivalent to the transformation between particle and its antiparticle. The evolution of this postulate from nonrelativistic QM via relativistic QM till the quantum field theory is discussed in some detail. The Klein paradox for both Klein-Gordon equation and Dirac equation is also discussed. Keywords: CPT invariance, Antiparticle, Quantum mechanics, Quantum field theory

Guang-jiong Ni; Suqing Chen; Jianjun Xu

2012-07-23

154

Preliminary results of sulfide melt/silicate wetting experiments in a partially melted ordinary chondrite  

NASA Technical Reports Server (NTRS)

Recently, mechanisms for core formation in planetary bodies have received considerable attention. Most current theories emphasize the need for large degrees of silicate partial melting to facilitate the coalescence and sinking of sulfide-metal liquid blebs through a low strength semi-crystalline silicate mush. This scenario is based upon observations that sulfide-metal liquid tends to form circular blebs in partially molten meteorites during laboratory experiments. However, recent experimental work by Herpfer and Larimer indicates that some sulfide-Fe liquids have wetting angles at and slightly below 60 deg in an olivine aggregate, implying an interconnected melt structure at any melt fraction. Such melt interconnectivity provides a means for gravitational compaction and extraction of the majority of a sulfide liquid phase in small planetary bodies without invoking large degrees of silicate partial melting. Because of the important ramifications of these results, we conducted a series of experiments using H-chondrite starting material in order to evaluate sulfide-liquid/silicate wetting behavior in a more complex natural system.

Jurewicz, Stephen R.; Jones, John H.

1994-01-01

155

Impact of Violations and Deviations in Hardy-Weinberg Equilibrium on Postulated Gene-Disease Associations  

Microsoft Academic Search

The authors evaluated whether statistically significant violations of Hardy-Weinberg equilibrium (HWE) or the magnitude of deviations from HWE may contribute to the problem of replicating postulated gene-disease associ- ations across different studies. Forty-two gene-disease associations assessed in meta-analyses of 591 studies were examined. Studies with disease-free controls in which HWE was violated gave significantly different results from HWE-conforming studies in

Thomas A. Trikalinos; Georgia Salanti; Muin J. Khoury; John P. A. Ioannidis

2006-01-01

156

The Light-Velocity Postulate: The Essential Difference between the Theories of Lorentz-Poincare and Einstein  

ERIC Educational Resources Information Center

Einstein, who had already developed the light-quantum theory, knew the inadequacy of Maxwell's theory in the microscopic sphere. Therefore, in writing his paper on special relativity, he had to set up the light-velocity postulate independently of the relativity postulate in order to make the electromagnetic foundation of physics compatible with…

Abiko, Seiya

2005-01-01

157

Ferrocyanide Safety Program: Analysis of postulated energetic reactions and resultant aerosol generation in Hanford Site Waste Tanks  

Microsoft Academic Search

This report reviews work done to estimate the possible consequences of postulated energetic reactions in ferrocyanide waste stored in underground tanks at the Hanford Site. The issue of explosive reactions was raised in the 1987 Environmental Impact Statement (EIS), where a detonation-like explosion was postulated for the purpose of defining an upper bound on dose consequences for various disposal options.

A. K. Postma; D. R. Dickinson

1995-01-01

158

NON-EUCLIDEAN GEOMETRIES In the previous chapter we began by adding Euclid's Fifth Postulate to his five common  

E-print Network

1 Chapter 3 NON-EUCLIDEAN GEOMETRIES In the previous chapter we began by adding Euclid's Fifth-dimensional canvas. Both Euclidean and hyperbolic geometry can be realized in this way, as later sections will show Postulate to his five common notions and first four postulates. This produced the familiar geometry

159

Orogenic processes in convergent margins: Constraints from partial melting experiments  

NASA Astrophysics Data System (ADS)

Convergent and collisional continental margins are characterized by metamorphism, magmatism and distributed zones of deformation, all of which contribute to the formation of convergent orogenic belts. Convergent regimes produce a variety of pressure-temperature conditions and one mechanism that greatly influences both the chemical and rheologic evolution of an orogenic belt is the presence of partial melt. The presence of a melt phase can produce focused, yet transient zones of thermal weakening and depending on melt fraction, different types of rheologic behavior. Magma production however, is dependent on a number of variables. The principal factor determining the melt-producing capacity is the fertility of the source assemblage, which is a function of bulk composition. In mica-bearing, quartzo-feldspathic rocks, melting will increase melt proportion as a function of temperature. Additional factors include the ratio of mica relative to quartz-feldspar eutectics, the temperature of the mica fluid-absent melting reaction and the pressure, which helps determine the anorthite component of the reacting feldspar. In this study we present the results from a series of fluid-absent partial melting experiments conducted on different crustal rock types under both static and dynamic (deformation) conditions. The experimental results allow us to compare the partial melting behavior of a fertile metapelite bearing two mica phases (muscovite and biotite) with a mafic clinozoisite, hornblende-rich metadiorite. These rock types represent the middle and lower crust, respectively. We have focused on the effects of static vs. dynamic conditions on total melt volume and the geochemistry of the melt phase. In particular we have determined the initial trace element concentration of the reactant hydrous phases on their influence on trace element chemistry of the product melt phase. Results show that reactant phase trace element abundance and associated micro-inclusions of accessory phases (particularly in the pelite experiments) control the initial REE signature of the melt phase. Initial major and trace element signatures are then modified by the mechanism of melt segregation and transport (crack network vs. shear zones) which influence the degree of equilibration between melt and source residue. Melt volume results show that partial melt volumes in the static metadiorite is low (<2 vol% at 800^oC to 12.3 vol.% at 950^oC) compared to those of the static core metapelite experiments (<5 vol% at 740^oC to >15 vol.% at 850^oC). These results, plus the strength results from the deformation experiments, suggests mafic lower crust can remain significantly stronger rheologically when compared to a mid-crust rich in metapelite during initial melting. An additional observation is that in the dynamic experiments on the metapelite, melt volume increases by a factor of 2 or more when compared to static core experiments at a given temperature. We observe the breakdown of biotite at a lower temperature in the dynamic experiments, which in turn produces the larger melt volume.

Rushmer, T.; Antignano, A., IV

2003-04-01

160

Thermodynamics of Oligonucleotide Duplex Melting  

ERIC Educational Resources Information Center

Melting temperatures of oligonucleotides are useful for a number of molecular biology applications, such as the polymerase chain reaction (PCR). Although melting temperatures are often calculated with simplistic empirical equations, application of thermodynamics provides more accurate melting temperatures and an opportunity for students to apply…

Schreiber-Gosche, Sherrie; Edwards, Robert A.

2009-01-01

161

The melting curve of Ni to 1 Mbar  

NASA Astrophysics Data System (ADS)

The melting curve of Ni has been determined to 125 GPa using laser-heated diamond anvil cell (LH-DAC) experiments in which two melting criteria were used: firstly, the appearance of liquid diffuse scattering (LDS) during in situ X-ray diffraction (XRD) and secondly, plateaux in temperature vs. laser power functions in both in situ and off-line experiments. Our new melting curve, defined by a Simon-Glatzel fit to the data where TM (K) =[ (PM/18.78±10.20 + 1) ] 1 / 2.42 ± 0.66 × 1726, is in good agreement with the majority of the theoretical studies on Ni melting and matches closely the available shock wave melting data. It is however dramatically steeper than the previous off-line LH-DAC studies in which determination of melting was based on the visual observation of motion aided by the laser speckle method. We estimate the melting point (TM) of Ni at the inner-core boundary (ICB) pressure of 330 GPa to be TM = 5800 ± 700 K (2 ?), within error of the value for Fe of TM = 6230 ± 500 K determined in a recent in situ LH-DAC study by similar methods to those employed here. This similarity suggests that the alloying of 5-10 wt.% Ni with the Fe-rich core alloy is unlikely to have any significant effect on the temperature of the ICB, though this is dependent on the details of the topology of the Fe-Ni binary phase diagram at core pressures. Our melting temperature for Ni at 330 GPa is ?2500 K higher than that found in previous experimental studies employing the laser speckle method. We find that those earlier melting curves coincide with the onset of rapid sub-solidus recrystallization, suggesting that visual observations of motion may have misinterpreted dynamic recrystallization as convective motion of a melt. This finding has significant implications for our understanding of the high-pressure melting behaviour of a number of other transition metals.

Lord, Oliver T.; Wood, Ian G.; Dobson, David P.; Vo?adlo, Lidunka; Wang, Weiwei; Thomson, Andrew R.; Wann, Elizabeth T. H.; Morard, Guillaume; Mezouar, Mohamed; Walter, Michael J.

2014-12-01

162

Experiments on in-vessel melt coolability in the EC-FOREVER program  

Microsoft Academic Search

This paper reports the results from the experiments conducted on the coolability of corium melt during a severe accident scenario when the bottom head is full of the core melt, undergoing natural circulation. These experiments are part of the EC-FOREVER Program in which vessel failure experiments have also been performed. The experiments are performed in a 1\\/10. scale vessel (

B. R. Sehgal; A. Giri; U. Chikkanagoudar; A. Karbojian

2004-01-01

163

Simeco Tests in a Melt Stratified Pool  

SciTech Connect

In the last phase of the core degradation, an oxidic melt pool of mainly UO{sub 2}; ZrO{sub 2}, and unoxidized Zircaloy and stain-less steel will form in the lower head of the RPV (Theofanous et al., 1996). A molten metal layer (composed mainly of Fe and Zr) will rest on the top of the crust of the oxidic pool. A thin oxidic crust layer of frozen core material is formed on the vessel's inside wall. In this bounding configuration, thermal loads to the RPV walls are determined by natural convection heat transfer driven by internal heat sources. Decay heat from fission products is assumed to be generated uniformly within the oxidic pool and generally no heat generation is considered in the upper metallic layer. For example, in a hypothetical severe accident scenario for an AP600-like reactor, the following values can be expected: volumetric heat generation Q{sub v} {approx} 1 MW/m{sup 3}, volume of the oxidic pool V {approx} 10 m{sup 3}, radius R = 2 m, temperatures in the oxidic pool T {approx} 2700 deg. C, temperatures in the metal layer T {approx} 2000 deg. C, maximum depth ratio of the metal layer to the oxidic pool L{sub 12} {approx} 0:3, properties of the oxidic pool, depending on melt composition, as characterized by the Prandtl number, Pr {approx} 0:6, properties of the metallic layer Pr < 0:1, the intensity of convective motion, as characterized by the Rayleigh number, Ra {approx} 10{sup 15} - 10{sup 16} (Theofanous et al., 1996). The time scale of core melt pool formation is estimated as 1/2 to 1 hour (Sehgal, 1999). Indeed, these estimates could vary, depending very much on the accident scenario and the type of reactor. (authors)

Gubaidullin, A.A.; Sehgal, B.R. [Royal Institute of Technology (KTH), Drottning Kristinas vaeg 33 A, 100 44, Stockholm (Sweden)

2002-07-01

164

Are polymer melts “ideal”?  

NASA Astrophysics Data System (ADS)

It is commonly accepted that in concentrated solutions or melts high-molecular weight polymers display random-walk conformational properties without long-range correlations between subsequent bonds. This absence of memory means, for instance, that the bond-bond correlation function, P(s), of two bonds separated by s monomers along the chain should exponentially decay with s. Presenting numerical results and theoretical arguments for both monodisperse chains and self-assembled (essentially Flory size-distributed) equilibrium polymers we demonstrate that some long-range correlations remain due to self-interactions of the chains caused by the chain connectivity and the incompressibility of the melt. Suggesting a profound analogy with the well-known long-range velocity correlations in liquids we find, for instance, P(s) to decay algebraically as s. Our study suggests a precise method for obtaining the statistical segment length b in a computer experiment.

Wittmer, J. P.; Beckrich, P.; Crevel, F.; Huang, C. C.; Cavallo, A.; Kreer, T.; Meyer, H.

2007-07-01

165

Melting Beneath Our Feet  

NSDL National Science Digital Library

This radio broadcast discusses how permafrost (permanently frozen ground) in Alaska and the Arctic has been melting, and what the potential consequences might be. These include damage to many engineering structures and coastlines and the release of gases into the atmosphere which may compound the problem of climate warming. About two-thirds of Alaska is covered by permafrost and a recent report says a higher priority should be given to studying it. The clip is about 4 minutes in length.

166

Melting Ice Caps  

NSDL National Science Digital Library

From the remote village of Gambell, Alaska, listener Bob Woolf can see the polar ice melting, and emailed us to ask if global warming would ever become irreversible. According to senior scientist Warren Washington of the National Center for Atmospheric Research, it probably already is, at least for the short term. That's because the greenhouse gases that are in the atmosphere now can last for decades or even centuries.

Science Update (AAAS; )

2006-08-15

167

Melt Modification of Polyamides  

Microsoft Academic Search

\\u000a Polyamides are engineering plastics with a wide application area. The first part of this contribution deals with the degradation\\u000a of polyamides including the discussion of degradation mechanism. The fast, controlled degradation reaction in the melt occurs\\u000a upon addition of carboxylic acid and carboxylic anhydride compounds. Oligoamides with a defined molecular weight and a narrow\\u000a molecular weight distribution could be obtained

Dieter Lehmann

168

Solubility of CH4 in a synthetic basaltic melt, with applications to atmosphere-magma ocean-core partitioning of volatiles and to the evolution of the Martian atmosphere  

NASA Astrophysics Data System (ADS)

We employ a double capsule technique to determine the solubility of CH4 in haplobasaltic (Fe-free) liquid under conditions of constrained methane fugacity, f, at pressures of 0.7-3 GPa at 1400-1450 °C. Dissolved C-O-H species are examined with FTIR and Raman spectroscopy, and CH4 and CH3- are the only C-bearing species detected. Carbon solubilities are quantified using SIMS, range from 70 to 480 ppm when calculated as CH4, and increase with pressure. Concentrations are parameterized with a thermodynamic model and are found to be related to f and pressure. Application of this thermodynamic model shows dissolved CH4 contents of graphite-saturated magmas are little-influenced by pressure for conditions of fixed f relative to metal-oxide buffers and fixed total H content. Because f of graphite-saturated systems increases with the square of hydrogen fugacity, dissolved f increases with decreasing f and increases exponentially with increasing total H content. The experimentally-observed increase with pressure is related to variations in f and H content. Dissolved CH4 contents of Martian magmas in their source regions are small, such that it is unlikely that magmatic CH4 is a principal contributor to greenhouse conditions early in Martian history. Concentrations of dissolved C-O-H volatiles in a magma ocean early in the history of a terrestrial planet may be diminished by reducing conditions, leading to development of a massive atmosphere and a greatly decreased inventory of volatiles stored in planetary interiors at the outset of planetary history. Dissolution of methane may enhance the retention of C in the silicate Earth during core formation, but experimental evaluation of its influence on metal/silicate partitioning of C requires careful matching of the magmatic H concentration between experiments and natural systems.

Ardia, P.; Hirschmann, M. M.; Withers, A. C.; Stanley, B. D.

2013-08-01

169

Phenocrystal variations in melt rocks from Tenoumer impact crater, Mauretania: indicators for varying target contribution and melt mixing.  

NASA Astrophysics Data System (ADS)

Impact melt rocks from the relatively small (1.9 km in diameter) Tenoumer impact crater (Mauretania) show heterogeneities regarding whole rock chemistry, lithoclast components, their shock deformation degree, amount of vesiculation (melt degassing), and contribution of carbonate melt phases mingled into silicate melt matrix. These heterogeneities have two main reasons: First, due to the restricted size of the impact crater there was probably no coherent melt pool where a homogeneous mixture of the target rocks could be achieved. Therefore, impact melting of target lithologies resulted in locally different, often incomplete mixing of melts from chemically very diverse target rocks. Second, melt rock heterogeneity occurs at the thin section scale and is due to fast cooling during and after the dynamic ejection and emplacement process. The overall period of crystal growth has been extremely short, so that chemical equilibration of the phases could not be achieved. Melt mixing processes involved in impact melt formation are, thus, recorded in non-equilibrium growth features. Mixing processes between chemically different melt phases and the formation of hybrid melts can be observed in the case of Tenoumer impact melts on a millimeter scale. Due to extreme cooling rates, different mixing stages are preserved in the varied parageneses and mineral chemistry of phenocrysts. Different silicate melt matrices show different phenocryst parageneses in response to slight variation of whole-rock chemistry and, thus, represents a useful indicator of precursor rock contribution to different impact melts. Basalt-andesitic (Mg,Fe-rich) melt matrices are after all composed of up to 20 vol% of forsterite-rich olivine-microphenocrysts. Decreasing Fe,Mg-amounts of melt matrix results in decreasing modal abundance of olivine, which shows progressively higher fayalite composition. These observations correlate with changing amounts of felsic and basic lithoclasts (granite, granitic gneiss, and gabbro). Different pyroxene generations occur including significant compositional zonation with widely variable CaO, MgO and FeO contents (En7-80, Wo4-50, Fs9-41). Pyroxene evolution (core-rim-zonation) changes from En-Di to Di-Hd as CaO content of the melt matrix oversteps 9 wt%. Strong variations in CaO content that do not correlate with increasing MgO and FeO contents are interpreted as incorporation of CaO from carbonate melts into the silicate melt phase. The presents of intermingled carbonate melt schlieren support this hypothesis. New 40Ar/39Ar dating on three of the studied melt rock samples resulted in a - preferred - age of 1.57 ± 0.14 Ma for the Tenoumer impact event. This impact age is significantly different from previous dating results of 21 ± 10 ka and 2.5 ± 0.5 Ma.

Schultze, Dina; Jourdan, Fred; Hecht, Lutz; Reimold, Uwe

2014-05-01

170

Melt spinning study  

NASA Technical Reports Server (NTRS)

Containerless processing of materials provides an excellent opportunity to study nucleation phenomena and produce unique materials, primarily through the formation of metastable phases and deep undercoolings. Deep undercoolings can be readily achieved in falling drops of molten material. Extended solute solubilities and greatly refined microstructures can also be obtained in containerless processing experiments. The Drop Tube Facility at Marshall Space Flight Center has played an important role in enhancing that area of research. Previous experiments performed in the Drop Tube with refractory metals has shown very interesting microstructural changes associated with deep undercoolings. It is apparent also that the microstructure of the deep undercooled species may be changing due to the release of the latent heat of fusion during recalescence. For scientific purposes, it is important to be able to differentiate between the microstructures of the two types of metallic species. A review of the literature shows that although significant advances have been made with respect to the engineering aspects of rapid solidification phenomena, there is still much to be learned in terms of understanding the basic phenomena. The two major ways in which rapid solidification processing provides improved structures and hence improved properties are: (1) production of refined structures such as fine dendrites and eutectics, and (2) production of new alloy compositions, microstructures, and phases through extended solid solubility, new phase reaction sequences, and the formation of metallic-glass microstructures. The objective of this work has been to determine the optimal methodology required to extract this excess energy without affecting the thermo-physical parameters of the under-cooled melt. In normal containerless processing experiments recalescence occurs as the melt returns toward the melting point in order to solidify. A new type of experiment is sought in which the resultant microstructure of the undercooled species is frozen in without going through the melting point regime and subsequent near equilibrium solidification of the remaining liquid. This experimental approach entails the design of an appropriate melt spinning system which is compatible with Drop Tube operations and processing constraints. That work is the goal of this study.

Workman, Gary L.; Rathz, Thomas

1993-01-01

171

Melt spinning study  

NASA Astrophysics Data System (ADS)

Containerless processing of materials provides an excellent opportunity to study nucleation phenomena and produce unique materials, primarily through the formation of metastable phases and deep undercoolings. Deep undercoolings can be readily achieved in falling drops of molten material. Extended solute solubilities and greatly refined microstructures can also be obtained in containerless processing experiments. The Drop Tube Facility at Marshall Space Flight Center has played an important role in enhancing that area of research. Previous experiments performed in the Drop Tube with refractory metals has shown very interesting microstructural changes associated with deep undercoolings. It is apparent also that the microstructure of the deep undercooled species may be changing due to the release of the latent heat of fusion during recalescence. For scientific purposes, it is important to be able to differentiate between the microstructures of the two types of metallic species. A review of the literature shows that although significant advances have been made with respect to the engineering aspects of rapid solidification phenomena, there is still much to be learned in terms of understanding the basic phenomena. The two major ways in which rapid solidification processing provides improved structures and hence improved properties are: (1) production of refined structures such as fine dendrites and eutectics, and (2) production of new alloy compositions, microstructures, and phases through extended solid solubility, new phase reaction sequences, and the formation of metallic-glass microstructures. The objective of this work has been to determine the optimal methodology required to extract this excess energy without affecting the thermo-physical parameters of the under-cooled melt. In normal containerless processing experiments recalescence occurs as the melt returns toward the melting point in order to solidify. A new type of experiment is sought in which the resultant microstructure of the undercooled species is frozen in without going through the melting point regime and subsequent near equilibrium solidification of the remaining liquid. This experimental approach entails the design of an appropriate melt spinning system which is compatible with Drop Tube operations and processing constraints. That work is the goal of this study.

Workman, Gary L.; Rathz, Thomas

1993-04-01

172

Thermal-hydraulic studies on molten core-concrete interactions  

SciTech Connect

This report discusses studies carried out in connection with light water power reactor accidents. Recent assessments have indicated that the consequences of molten-core concrete interactions dominate the considerations of severe accidents. The two areas of interest that have been investigated are interlayer heat and mass transfer and liquid-liquid boiling. Interlayer heat and mass transfer refers to processes that occur within a core melt between the stratified, immiscible phases of core oxides and metals. Liquid-liquid boiling refers to processes that occur at the melt-concrete on melt-coolant interface. (JDH)

Greene, G.A.

1986-10-01

173

Modeling and analyses of postulated UF{sub 6} release accidents in gaseous diffusion plant  

SciTech Connect

Computer models have been developed to simulate the transient behavior of aerosols and vapors as a result of a postulated accident involving the release of uranium hexafluoride (UF{sub 6}) into the process building of a gaseous diffusion plant. UF{sub 6} undergoes an exothermic chemical reaction with moisture (H{sub 2}O) in the air to form hydrogen fluoride (HF) and radioactive uranyl fluoride (UO{sub 2}F{sub 2}). As part of a facility-wide safety evaluation, this study evaluated source terms consisting of UO{sub 2}F{sub 2} as well as HF during a postulated UF{sub 6} release accident in a process building. In the postulated accident scenario, {approximately}7900 kg (17,500 lb) of hot UF{sub 6} vapor is released over a 5 min period from the process piping into the atmosphere of a large process building. UO{sub 2}F{sub 2} mainly remains as airborne-solid particles (aerosols), and HF is in a vapor form. Some UO{sub 2}F{sub 2} aerosols are removed from the air flow due to gravitational settling. The HF and the remaining UO{sub 2}F{sub 2} are mixed with air and exhausted through the building ventilation system. The MELCOR computer code was selected for simulating aerosols and vapor transport in the process building. MELCOR model was first used to develop a single volume representation of a process building and its results were compared with those from past lumped parameter models specifically developed for studying UF{sub 6} release accidents. Preliminary results indicate that MELCOR predicted results (using a lumped formulation) are comparable with those from previously developed models.

Kim, S.H.; Taleyarkhan, R.P.; Keith, K.D.; Schmidt, R.W. [Oak Ridge National Lab., TN (United States); Carter, J.C. [J.C. Carter Associates, Inc., Oak Ridge, TN (United States); Dyer, R.H. [Dyer Enterprises, Oak Ridge, TN (United States)

1995-10-01

174

Melt quenching and coolability by water injection from below: Co-injection of water and non-condensable gas  

Microsoft Academic Search

The interaction and mixing of high-temperature melt and water is the important technical issue in the safety assessment of water-cooled reactors to achieve ultimate core coolability. For specific advanced light water reactor (ALWR) designs, deliberate mixing of the core melt and water is being considered as a mitigative measure, to assure ex-vessel core coolability. The goal of our work is

Dae H. Cho; Richard J. Page; Sherif H. Abdulla; Mark H. Anderson; Helge B. Klockow; Michael L. Corradini

2006-01-01

175

Silicate melt inclusions in clinopyroxene phenocrysts from mafic dikes in the eastern North China Craton: Constraints on melt evolution  

NASA Astrophysics Data System (ADS)

Silicate melt inclusions (SMIs) in magmatic minerals provide key information on the chemical and mineralogical evolution of source magmas. The widespread Cretaceous mafic dikes in the Jiaojia region of the eastern North China Craton contain abundant SMIs within clinopyroxene phenocrysts. The daughter minerals in these SMIs include amphibole, plagioclase, pyrite and ilmenite, together with CO2 + CH4 and CH4 as the major volatile phase. The total homogenization temperatures of the SMIs range between 1280 and 1300 °C. The host clinopyroxene phenocrysts in these dolerite dikes are dominantly augite with minor diopside. From LA-ICPMS analyses of the SMIs, we identify two compositional groups: (1) low-MgO (6.0-7.6 wt.%) SMIs and (2) high-MgO (11.2-13.9 wt.%) SMIs. The Low-MgO group exhibits higher concentrations of TiO2, Al2O3, Na2O, P2O5 and lower CaO and CaO/Al2O3 ratio as compared to the high-MgO SMIs. The trace element patterns of the two types of SMIs are similar to those of the host mafic dikes. However, the low-MgO SMIs and host mafic dikes are clearly more enriched in all the trace elements as compared to the high-MgO type, especially with regard to the highly incompatible elements. The estimated capture temperatures and pressures are 1351-1400 °C and 1.6-2.1 GPa for the high-MgO SMIs and 1177-1215 °C and 0.6-1.1GPa for the low-MgO type. The high-MgO and low-MgO SMIs were trapped at depths of ?51-68 km and ?20-35 km, respectively. Computations show that the parental melt is mafic with SiO2 content 49.6 wt% and Mg# 80.0 with relatively low total alkali contents (1.35 wt% Na2O + K2O) and high CaO (15.2 wt%). Exploratory runs with the program MELTS and pMELTS show that the low-MgO and high-MgO SMIs were derived from the same parental melt through different degrees of crystallization. Clinopyroxene and a small amount of olivine were the fractionating phases during the evolution from parental melts to high MgO melts, while the low MgO melts experienced significant fractional crystallization of olivine and clinopyroxene. We postulate the newly accreted lithospheric clinopyroxenite as the major source for the Jiaojia dolerite dikes, with melting of the source at a depth of ?68-80 km.

Cai, Ya-Chun; Fan, Hong-Rui; Santosh, M.; Hu, Fang-Fang; Yang, Kui-Feng; Liu, Xuan; Liu, Yongsheng

2015-01-01

176

Attempt at clarification of Einstein's postulate of constancy of light velocity  

E-print Network

We have realized that under Lorentz transformations the tick number of a moving common clock remains unchanged, that is, the hand of the clock never runs slow, but the time interval between its two consecutive ticks contracts, so the relative time has to be recorded by using the tau-clocks required by the transformations, instead of unreal slowing clocks. Thus it is argued that using rest common clocks or the equivalent the measured velocity of light emitted by a moving source, which is quasi-velocity of foreign light, is dependent of the source velocity. Nevertheless, the velocity of foreign light that should be measured by using tau-clocks is independent of the source velocity. The velocity of native light emitted by a rest source obeys the postulate of relativity in accordance with both Maxwell equations and the result of Michelson-Morley experiment. On the other hand, the velocity of foreign light obeys both Ritz's emission theory except the Lorentz factor and the postulate of constancy of light velocity if measured by using tau-clocks. Thus the emission theory does not conflict with special relativity. The present argument leads to a logical consequence that the so-called positive conclusions from experiments testing constancy of the velocity of light emitted by moving sources if using common clocks or the equivalent, instead of tau-clocks, exactly contradicts Lorentz transformations.

Wang Guowen

2005-12-05

177

Investigation of reactions postulated to occur during inhibition of ribonucleotide reductases by 2?-azido-2?-deoxynucleotides  

PubMed Central

Model 3?-azido-3?-deoxynucleosides with thiol or vicinal dithiol substituents at C2? or C5? were synthesized to study reactions postulated to occur during inhibition of ribonucleotide reductases by 2?-azido-2?-deoxynucleotides. Esterification of 5?-(tert-butyldiphenylsilyl)-3?-azido-3?-deoxyadenosine and 3?-azido-3?-deoxythymidine (AZT) with 2,3-S-isopropylidene-2,3-dimercaptopropanoic acid or N-Boc-S-trityl-L-cysteine and deprotection gave 3?-azido-3?-deoxy-2?-O-(2,3-dimercaptopropanoyl or cysteinyl)adenosine and the 3?-azido-3?-deoxy-5?-O-(2,3-dimercaptopropanoyl or cysteinyl)thymidine analogs. Density functional calculations predicted that intramolecular reactions between generated thiyl radicals and an azido group on such model compounds would be exothermic by 33.6-41.2 kcal/mol and have low energy barriers of 10.4-13.5 kcal/mol. Reduction of the azido group occurred to give 3?-amino-3?-deoxythymidine, which was postulated to occur with thiyl radicals generated by treatment of 3?-azido-3?-deoxy-5?-O-(2,3-dimercaptopropanoyl)thymidine with 2,2?-azobis-(2-methyl-2-propionamidine) dihydrochloride. Gamma radiolysis of N2O-saturated aqueous solutions of AZT and cysteine produced 3?-amino-3?-deoxythymidine and thymine most likely by both radical and ionic processes. PMID:22711937

Dang, Thao P.; Sobczak, Adam J.; Mebel, Alexander M.; Chatgilialoglu, Chryssostomos; Wnuk, Stanislaw F.

2012-01-01

178

Are polymer melts \\  

Microsoft Academic Search

It is commonly accepted that in concentrated solutions or melts\\u000ahigh-molecular weight polymers display random-walk conformational properties\\u000awithout long-range correlations between subsequent bonds. This absence of\\u000amemory means, for instance, that the bond-bond correlation function, $P(s)$, of\\u000atwo bonds separated by $s$ monomers along the chain should exponentially decay\\u000awith $s$. Presenting numerical results and theoretical arguments for both\\u000amonodisperse

J. P. Wittmer; P. Beckrich; F. Crevel; C. C. Huang; A. Cavallo; T. Kreer; H. Meyer

2007-01-01

179

An integral approach to investigate planetary cores  

NASA Astrophysics Data System (ADS)

The same core-mantle differentiation process was in operation during the early formation of the terrestrial planets, but it led to unique cores for the Earth, Venus, Mars, and Mercury, with different magnetic fields, reflecting their different dynamic, physical, and chemical states. Assuming all terrestrial planets shared the same materials of the building block, the differences must be resulted from the different conditions of the early accretion and the subsequent planetary evolution unique to each planet. The pressures at the core-mantle boundary of the terrestrial planets range from as low as 7 GPa to 136 GPa. The physical state (liquid or solid) for each planetary core is closely tied to the melting and chemical composition of the cores. In order to determine the minimal temperature of a liquid core or the maximal temperature of a solid core, we have systematically investigated melting relations in the binary systems Fe-FeS, Fe-C, and Fe-FeSi, move toward unravelling the crystallization sequence and element partitioning between solid and liquid metal in the ternary and quaternary systems up to 25 GPa, using multi-anvil apparatus. We have developed new techniques to analyze the quenched samples recovered from laser-heating diamond-anvil cell experiments using combination of focus ion beam (FIB) milling, high-resolution SEM imaging, and quantitative chemical analysis with silicon drift detector EDS. With precision milling of the laser-heating spot, we determined melting using quenching texture criteria imaged with high-resolution SEM and the sulfur partitioning between solid and liquid at submicron spatial resolution. We have also re-constructed 3D image of the laser-heating spot at multi-megabar pressures to better constrain melting point and understanding melting process. The new techniques allow us to extend precise measurements of melting relations to core pressures in the laser-heating diamond-anvil cell. In addition to the static experiments, we also used shockwave compression to determine density, sound velocity, and melting of core materials up to liquid outer core conditions. The integration of the static and dynamic compression data provides an extensive dataset over a wide pressure and temperature range that is necessary for establishing a comprehensive model of the planetary cores, providing the best fit to the geophysical, cosmochemial, and geochemical observations.

Fei, Y.

2012-12-01

180

Melting of Ice under Pressure  

SciTech Connect

The melting of ice under pressure is investigated with a series of first principles molecular dynamics simulations. In particular, a two-phase approach is used to determine the melting temperature of the ice-VII phase in the range of 10 to 50 GPa. Our computed melting temperatures are consistent with existing diamond anvil cell experiments. We find that for pressures between 10 to 40 GPa, ice melts as a molecular solid. For pressures above {approx}45 GPa there is a sharp increase in the slope of the melting curve due to the presence of molecular dissociation and proton diffusion in the solid, prior to melting. The onset of significant proton diffusion in ice-VII as a function of increasing temperature is found to be gradual and bears many similarities to that of a type-II superionic solid.

Schwegler, E; Sharma, M; Gygi, F; Galli, G

2008-07-31

181

Melting of ice under pressure  

PubMed Central

The melting of ice under pressure is investigated with a series of first-principles molecular dynamics simulations. In particular, a two-phase approach is used to determine the melting temperature of the ice-VII phase in the range of 10–50 GPa. Our computed melting temperatures are consistent with existing diamond anvil cell experiments. We find that for pressures between 10 and 40 GPa, ice melts as a molecular solid. For pressures above ?45 Gpa, there is a sharp increase in the slope of the melting curve because of the presence of molecular dissociation and proton diffusion in the solid before melting. The onset of significant proton diffusion in ice-VII as a function of increasing temperature is found to be gradual and bears many similarities to that of a type-II superionic solid. PMID:18809909

Schwegler, Eric; Sharma, Manu; Gygi, François; Galli, Giulia

2008-01-01

182

Analysis of the role of von Neumann's projection postulate in the canonical scheme of quantum teleportation and main quantum algorithms  

E-print Network

Modern development of quantum technologies based on quantum information theory stimulated analysis of proposed computational, cryptographic and teleportational schemes from the viewpoint of quantum foundations. It is evident that not all mathematical calculations performed in complex Hilbert space can be directly realized in physical space. Recently by analyzing the original EPR paper we found that they argument was based on the misuse of the von Neumann's projection postulate. Opposite to von Neumann, Einstein, Podolsky and Rosen (EPR) applied this postulate to observables represented by operators with degenerate spectra. It was completely forbidden by von Neumann's axiomatics of QM. It is impossible to repeat the EPR considerations in the von Neumann's framework. In this note we analyze quantum teleportation by taking into account von Neumann's projection postulate. Our analysis shows that so called quantum teleportation is impossible in von Neumann's framework. On the other hand, our analysis implies that the main quantum algorithms are totally consistent with von Neumann's projection postulate.

Andrei Khrennikov

2008-05-23

183

Chicxulub Impact Melts: Geochemical Signatures of Target Lithology Mixing and Post-Impact Hydrothermal Fluid Processes  

NASA Technical Reports Server (NTRS)

Impact melts within complex impact craters are generally homogeneous, unless they differentiated, contain immiscible melt components, or were hydrothermally altered while cooling. The details of these processes, however, and their chemical consequences, are poorly understood. The best opportunity to unravel them may lie with the Chicxulub impact structure, because it is the world s most pristine (albeit buried) large impact crater. The Chicxulub Scientific Drilling Project recovered approx. 100 meters of impactites in a continuous core from the Yaxcopoil-1 (YAX-1) borehole. This dramatically increased the amount of melt available for analyses, which was previously limited to two small samples N17 and N19) recovered from the Yucatan-6 (Y-6) borehole and one sample (N10) recovered from the Chicxulub-1 (C-1) borehole. In this study, we describe the chemical compositions of six melt samples over an approx. 40 m section of the core and compare them to previous melt samples from the Y-6 and C-1 boreholes.

Kring, David A.; Zurcher, Lukas; Horz, Freidrich; Mertzmann, Stanley A.

2004-01-01

184

Holographic Meson Melting  

E-print Network

The plasma phase at high temperatures of a strongly coupled gauge theory can be holographically modelled by an AdS black hole. Matter in the fundamental representation and in the quenched approximation is introduced through embedding D7-branes in the AdS-Schwarzschild background. Low spin mesons correspond to the fluctuations of the D7-brane world volume. As is well known by now, there are two different kinds of embeddings, either reaching down to the black hole horizon or staying outside of it. In the latter case the fluctuations of the D7-brane world volume represent stable low spin mesons. In the plasma phase we do not expect mesons to be stable but to melt at sufficiently high temperature. We model the late stages of this meson melting by the quasinormal modes of D7-brane fluctuations for the embeddings that do reach down to the horizon. The inverse of the imaginary part of the quasinormal frequency gives the typical relaxation time back to equilibrium of the meson perturbation in the hot plasma. We briefly comment on the possible application of our model to quarkonium suppression.

Carlos Hoyos; Karl Landsteiner; Sergio Montero

2007-07-11

185

Holographic Meson Melting  

E-print Network

The plasma phase at high temperatures of a strongly coupled gauge theory can be holographically modelled by an AdS black hole. Matter in the fundamental representation and in the quenched approximation is introduced through embedding D7-branes in the AdS-Schwarzschild background. Low spin mesons correspond to the fluctuations of the D7-brane world volume. As is well known by now, there are two different kinds of embeddings, either reaching down to the black hole horizon or staying outside of it. In the latter case the fluctuations of the D7-brane world volume represent stable low spin mesons. In the plasma phase we do not expect mesons to be stable but to melt at sufficiently high temperature. We model this meson melting by the quasinormal modes of D7-brane fluctuations for the embeddings that do reach down to the horizon. The inverse of the imaginary part of the quasinormal frequency gives the lifetime of the meson in the hot plasma. We briefly comment on the possible application of our model to quarkonium s...

Hoyos, C; Montero, S; Hoyos, Carlos; Landsteiner, Karl; Montero, Sergio

2007-01-01

186

Lunar highland melt rocks - Chemistry, petrology and silicate mineralogy  

NASA Technical Reports Server (NTRS)

A selected suite containing several of the largest samples of lunar highland melt rocks includes impact melt specimens (anorthositic gabbro, low-K Fra Mauro) and volcanic specimens (intermediate-K Fra Mauro). Although previous assumptions of LKFM volcanism have fallen into disfavor, no fatal arguments against this hypothesis have been presented, and the evidence of a possibly 'inherited igneous' olivine-plagioclase cosaturation provides cause for keeping a volcanic LKFM hypothesis viable. Comparisons of silicate mineralogy with melt rock compositions provide information on the specimen's composition and cooling history. Plagioclase-rock compositions can be matched to the experimentally determined equilibria for appropriate samples to identify melt rocks with refractory anorthitic clasts. Olivine-rock compositions indicate that melt rock vitrophyres precipitate anomalously Fe-rich olivine; the cause of this anomaly is not immediately evident. The Al-Ti and Ca-Fe-Mg zonation in pyroxene provide information on relative cooling rates of highland melt rocks, but Cr- and Al-content (where Al-rich low-Ca pyroxene cores are preserved in rapidly cooled samples) can be correlated with composition of the host rock.

Vaniman, D. T.; Papike, J. J.

1980-01-01

187

Molecular dynamics simulations of the melting of KCl nanoparticles  

NASA Astrophysics Data System (ADS)

Molecular dynamics (MD) simulations are used to investigate the thermodynamic properties and structural changes of KCl spherical nanoparticles at various sizes (1064, 1736, 2800, 3648, 4224 and 5832 ions) upon heating. The melting temperature is dependent on both the size and shape of KCl models, and the behaviour of the first order phase transition is also found in the present work. The surface melting found here is different from the melting phenomena of KCl models or other alkali halides studied in the past. In the premelting stage, a mixed phase containing liquid and solid ions covers the surface of nanoparticles. The only peak of heat capacity spreads out a significant segment of temperature, probably exhibiting both heterogeneous melting on the surface and homogeneous melting in the core. The coexistence of two melting mechanisms, homogeneous and heterogeneous ones, in our model is unlike those considered previously. We also found that the critical Lindemann ratio of the KCl nanoparticle becomes much more stable when the size of the nanoparticle is of the order of thousands of ions. A picture of the structural evolution upon heating is studied in more detail via the radial distribution function (RDF) and coordination numbers. Our results are in a good agreement with previous MD simulations and experimental observations.

Sang, Le Van; Huong, Ta Thi Thuy; Minh, Le Nguyen Tue

2014-10-01

188

Geometric calculus-based postulates for the derivation and extension of the Maxwell equations  

NASA Astrophysics Data System (ADS)

Clifford analysis, particularly application of the geometric algebra of three-dimensional physical space and its associated geometric calculus, enables a compact formulation of Maxwell's electromagnetic (EM) equations from a set of physically relevant and mathematically pleasing postulates. This formulation results in a natural extension of the Maxwell equations yielding wave solutions in addition to the usual EM waves. These additional solutions do not contradict experiment and have three properties in common with the apparent properties of dark energy. These three properties are that the wave solutions 1) propagate at the speed of light, 2) do not interact with ordinary electric charges or currents, and 3) possess retrograde momentum. By retrograde momentum, we mean that the momentum carried by such a wave is directed oppositely to the direction of energy transport. A "gas" of such waves generates negative pressure.

McClellan, Gene E.

2012-09-01

189

Fritz Zwicky's Postulate of Freedom from Prejudice Considered from the Standpoint of the Theory of Knowledge  

NASA Astrophysics Data System (ADS)

What can we say about unprejudiced thinking as postulated by Ritz Zwicky? Freedom from prejudice in opposition to stamped by theory. How does knowledge come about? Through sense perception and thought. The phenomenon is always mediated by organs, respectively by technical instruments. Which conclusion can we draw from this fact? Is the organ of knowledge by which we know nature a part of nature? Can the dialectic materialism explain the processes of human consciousness? What is the fundamental difference between think and perceive? Has human consciousness only a share in nature or also in the spiritual world? The role of the observer in the Copenhagen interpretation. Is the quantum theory applicable to psychic phenomena?

Lutz, Markus

190

Estimation of Downstream Cesium Concentrations Following a Postulated PAR Pond Dam Break  

SciTech Connect

Following a postulated PAR Pond dam break, some of the PAR Pond sediment including the cesium could be eroded and be transported downstream to the Savannah River through the Lower Three Runs Creek. Studies showed that most of the eroded sediment including the cesium would deposit in the Lower Three Runs Creek and the remainder would discharge to the Savannah River from the mouth of Lower Three Runs Creek. A WASP5 model was developed to simulate the eroded sediment and cesium transport from the Lower Three Runs Creek mouth to the Atlantic coast. The dissolved cesium concentrations at the Highway 301 bridge and near the City of Savannah Industrial and Domestic Water Supply Plant are 30 and 27 pCi/l, respectively. The concentrations at both locations are less than the U. S. Environmental Protection Agency drinking water standard of 200 pCi/l.

Chen, K.F.

2002-07-08

191

Existence of an information unit as a postulate of quantum theory.  

PubMed

Does information play a significant role in the foundations of physics? Information is the abstraction that allows us to refer to the states of systems when we choose to ignore the systems themselves. This is only possible in very particular frameworks, like in classical or quantum theory, or more generally, whenever there exists an information unit such that the state of any system can be reversibly encoded in a sufficient number of such units. In this work, we show how the abstract formalism of quantum theory can be deduced solely from the existence of an information unit with suitable properties, together with two further natural assumptions: the continuity and reversibility of dynamics, and the possibility of characterizing the state of a composite system by local measurements. This constitutes a set of postulates for quantum theory with a simple and direct physical meaning, like the ones of special relativity or thermodynamics, and it articulates a strong connection between physics and information. PMID:24062431

Masanes, Lluís; Müller, Markus P; Augusiak, Remigiusz; Pérez-García, David

2013-10-01

192

Melt pool dynamics during selective electron beam melting  

NASA Astrophysics Data System (ADS)

Electron beam melting is a promising additive manufacturing technique for metal parts. Nevertheless, the process is still poorly understood making further investigations indispensable to allow a prediction of the part's quality. To improve the understanding of the process especially the beam powder interaction, process observation at the relevant time scale is necessary. Due to the difficult accessibility of the building area, the high temperatures, radiation and the very high scanning speeds during the melting process the observation requires an augmented effort in the observation equipment. A high speed camera in combination with an illumination laser, band pass filter and mirror system is suitable for the observation of the electron beam melting process. The equipment allows to observe the melting process with a high spatial and temporal resolution. In this paper the adjustment of the equipment and results of the lifetime and the oscillation frequencies of the melt pool for a simple geometry are presented.

Scharowsky, T.; Osmanlic, F.; Singer, R. F.; Körner, C.

2014-03-01

193

Manicouagan and the Moon: Reassessing Impact Melt - Crater Affiliations  

NASA Astrophysics Data System (ADS)

When Apollo samples were first returned to Earth, comparisons were made with several terrestrial impact melt sheets to aid in the interpretation of the samples. Manicouagan was considered representative of a 60 to 100 km size complex crater with a supposedly undifferentiated, chemically homogeneous, although somewhat texturally heterogeneous, impact-melt sheet. Based on the belief that craters in the size range of Manicouagan produced chemically homogeneous melt sheets, Simonds et al. (1976) identified four distinct compositions of lunar melt in Apollo 16 breccia samples, attributing each to four different impact-melt sheets formed during discrete cratering events. However, recent drilling activities at Manicouagan, combined with surface sampling and geochemical analysis, have revealed that its impact-melt sheet is not of uniform composition as suggested by past field work. This calls into question previously held assumptions regarding the identification and interpretation of lunar impact melts. Drilling has revealed an unexpectedly varied topography to the melt sheet-basement contact in the centre of the structure at Manicouagan. An elongate, impact-melt filled, N-S trough extending at least 8 km from the southern flanks of the uplifted Mont de Babel anorthosite has been identified. The trough varies in depth from 600 m at the northern and southern extremes, to 1430 m in the middle, resulting in substantially thicker melt sections than previously identified by field work, which estimated current impact-melt sheet thickness to be 200 to 300 m. Our geochemical analysis of 88 core and field impact melt samples reveal that the more typical 300 m thick sections and the newly discovered 600 m thick sections intersected within the central trough in drill holes MAN0501 and 0511, exhibit a homogeneous, quartz monzodiorite composition comparable with previous average impact melt compositions. In contrast, the 1100 m clast-free melt sequence encountered in the centre of the graben in hole MAN0608 is segregated into two compositionally distinct layers, separated by a transition zone: a 450 m thick lower monzodiorite; a 180 m thick transition zone of quartz monzodiorite (the same as the average composition of the impact-melt sheet intersected in the other drill holes), and a 450 m thick upper quartz monzonite. The identification of a thicker, fractionated impact-melt sheet section at a crater the size of Manicouagan (90 km) has implications for the interpretation of lunar samples. It is apparent that samples previously assigned to separate impact events on the Moon may be differentiates of a common impact-melt sheet. Critically, this may occur at smaller diameters than previously considered. Simonds, C.H., Warner, J.L. and Phinney, W.C. 1976. Thermal regimes in cratered terrains with emphasis on the role of impact melt. Am. Mineral. 61, 569-577.

Spray, J. G.; Thompson, L. M.; O'Connell-Cooper, C.

2009-05-01

194

Pressure melting and ice skating  

Microsoft Academic Search

Pressure melting cannot be responsible for the low friction of ice. The pressure needed to reach the melting temperature is above the compressive failure stress and, if it did occur, high squeeze losses would result in very thin films. Pure liquid water cannot coexist with ice much below -20 °C at any pressure and friction does not increase suddenly in

S. C. Colbeck

1995-01-01

195

Water solubility in aluminosilicate melts  

Microsoft Academic Search

We have compiled water solubility data for a wide range of natural and synthetic aluminosilicate melts in a search for correlations between melt composition and solubility. The published data reveal some interesting systematics. For example, molar water solubility increases with decreasing silica content in binary and pseudobinary silicates, and much higher solubilities are associated with alkali systems compared to alkaline

Paul F. McMillan; John R. Holloway

1987-01-01

196

EUCLIDEAN PARALLEL POSTULATE 2.1 INTRODUCTION. There is a well-developed theory for a geometry based solely on the  

E-print Network

on the geometry of the Euclidean plane taught in high school. It is more instructive to begin with an axiom Postulate. A geometry based on the Common Notions, the first four Postulates and the Euclidean Parallel Postulate will thus be called Euclidean (plane) geometry. In the next chapter Hyperbolic (plane) geometry

197

Melt Redistribution in Dynamic Systems: Applications to Core Formation  

NASA Technical Reports Server (NTRS)

Samples of olivine + Fe-S were fabricated by hot-pressing a mechanical mixture of the two phases. Olivine powders with a starting grain size of approx. 10 microns were prepared by crushing crystals of San Carlos olivine followed by pulverization in a fluid energy mill. Iron sulfide powder with a particle size of approx. 5 microns was prepared from a 2:1 mixture of reagent grade iron sulfide (FeS) plus iron. Rods 20 mm in length by 10 mm in diameter were cold-pressed into iron capsules with a uniaxial stress of approx. 200 MPa. These rods were then hot-pressed at 1523 K and 300 MPa for 4 h to obtain a starting material with <2% porosity. Samples for shear experiments were cut perpendicular to the long axis of these rods. The discs were shaped into ellipses approx. 6 mm by approx. 8 mm with a thickness ranging from 0.6 to 1.0 mm. An iron foil strain marker was inserted into a cut made along the minor axis. The sample was placed between two thoriated tungsten pistons cut at 45 deg to the long axis and then placed into an iron sleeve capped by alumina discs. The sample was then sheared in a gas pressure-medium apparatus at a temperature of 1523 K and a confining pressure of 300 MPa.

Hustoft, J. W.; Kohlstedt, D. L.

2003-01-01

198

The growth of hygroscopic particles during severe core melt accidents  

Microsoft Academic Search

Fission products and other compounds released during severe nuclear power plant accidents will form aerosol particles, which include water-soluble compounds such as cesium hydroxide (CsOH), cesium carbonate, and cesium iodide. These hygroscopic particles will grow in a humid environment, and thus their settling rate is increased significantly at high relative humidities. This paper evaluates the hygroscopicity of CsOH and other

Jokiniemi

1988-01-01

199

SCDAP: a computer code for analyzing light-water-reactor severe core damage  

Microsoft Academic Search

The Severe Core Damage Analysis Package (SCDAP) computer code is being developed at the Idaho National Engineering Laboratory under the sponsorship of the US Nuclear Regulatory Commission, Office of Nuclear Regulatory Research. SCDAP models the progression of light water reactor core damage including core heatup, core disruption, debris formation, debris heatup, and debris melting. SCDAP is being used to help

C. M. Allison; E. R. Carlson; R. H. Smith

1983-01-01

200

Granulite Migmatization and Retrogression: Result of Pervasive Melt Influx? (Invited)  

NASA Astrophysics Data System (ADS)

The Blanský les granulite massif (BLG) is large (ca. 270 km2) lower crust exposure in Bohemian Massif in Czech Republic. It consists of felsic granulites in various degrees of retrogression and small bodies of eclogites, mafic granulites and ultrabasites. Peak granulitic conditions were estimated at ca. 16-18 kbar and 850-1100°C. This granulite massif was later, during exhumation, heterogeneously retrogressed in amphibolite facies conditions (ca. 5-7 kbar and 700-800°C). The degree of granulite retrogression increases continuously from the core towards the margin of the BLG massif. The question raised in this work is the nature of the retrogression. In core of the massif retrogression is manifested only by plagioclase and spinel coronas around kyanite. Towards the margin granulite gets progressively hydrated, has gneissic look and stable mineral assemblage of Qtz + Kfs + Pl + Bt + Sill × Grt. Retrograde granulite reveals higher amount of biotite, which forms at expanse of garnet and kyanite break down to sillimanite. Along the margin the transformation is accompanied by presence of melt, resulting into formation of migmatitic gneisses. The detailed field and microstructural observations revealed a gradual transition from mylonitic gneiss with only incipient amount of melt to migmatitic gneisses with no relict of gneissosity and high proportion of melt. This transition is accompanied by textural changes as well as changes in mineral chemistry (increase of XFe in biotite and garnet, increase of Na in plagioclase) and mineral proportions (decrease of garnet %, increase of biotite and feldspars %). During the exhumation, the granulite was dry, thus melt present in the granulite cannot be produced in-situ. We suggest that the hot dry granulite released and 'attracted' water from colder underlying metasedimentary sequence. This water flux caused extensive melting along the massif margins. This melt then further pervasively migrated towards the core of the massif causing heterogeneous migmatization and retrogression of the granulite. Moreover, we suggest that at an outcrop-scale leucosome distribution controls the extent of the retrogression. Distribution gradient created by the water-saturated melt in leucosomes is spatially limited. Thus granulite closer to the leucosome will reveal higher degree of retrogression than further from the leucosome. Importantly, melt presence in the granulite will play important role for the rheology at lower-middle crust interface.

Hasalova, P.; Štípská, P.; Weinberg, R. F.; Fran?k, J.; Schulmann, K.

2013-12-01

201

Crystallization and Melting of Diopside - Anorthite  

NSDL National Science Digital Library

This short exercise introduces students to phase diagrams that have a eutectic and a peritectic. After learning about such phase diagrams, students answer questions about melt composition, temperature, cooling and melting, crystalization, and melt:crystal ratios.

Dexter Perkins

202

Liquid entrainment by an expanding core disruptive accident bubble—a Kelvin\\/Helmholtz phenomenon  

Microsoft Academic Search

The final stage of a postulated energetic core disruptive accident (CDA) in a liquid metal fast breeder reactor is believed to involve the expansion of a high-pressure core-material bubble against the overlying pool of sodium. Some of the sodium will be entrained by the CDA bubble which may influence the mechanical energy available for damage to the reactor vessel. The

Michael Epstein; Hans K. Fauske; Shigenobu Kubo; Toshio Nakamura; Kazuya Koyama

2001-01-01

203

Modeling of residual stresses in core shroud structures  

SciTech Connect

A BWR core shroud is a cylindrical shell that surrounds the reactor core. Feedwater for the reactor is introduced into the annulus between the reactor vessel wall and the shroud. The shroud separates the feedwater from the cooling water flowing up through the reactor core. The shroud also supports the top guide which provides lateral support to the fuel assemblies and maintains core geometry during operational transients and postulated accidents to permit control rod insertion and provides the refloodable volume needed to ensure safe shutdown and cooling of the core during postulated accident conditions. Core shrouds were fabricated from welded Type 304 or 304L stainless steel plates and are supported at the top and bottom by forged ring support structures. In 1990, cracking was reported in the core shroud of a non-U.S. BWR. The cracks were located in the heat-affected zone (HAZ) of a circumferential core shroud weld. Subsequent inspections in U.S. BWRs have revealed the presence of numerous flaw indications in some BWR core shrouds, primarily in weld HAZs. In several instances, this cracking was quite extensive, with the cracks extending 75% or more around the circumference of some welds. However, because the applied stresses on the shroud are low during operation and postulated accidents and because of the high fracture toughness of stainless steel, adequate structural margins can be preserved even in the presence of extensive cracking. Although assessments by the USNRC staff of the potential significance of this cracking have shown that core shroud cracking does not pose a high degree of risk in the short term, the staff concluded that the cracking was a safety concern for the long term because of the uncertainties associated with the behavior of core shrouds with complete 360{degrees} through-wall cracks under accident conditions and because it could eliminate a layer of defense-in-depth.

Zhang, J.; Dong, P.; Brust, F.W.; Mayfield, M.; McNeil, M.; Shack, W.J.

1997-10-01

204

The Human Genomic Melting Map  

PubMed Central

In a living cell, the antiparallel double-stranded helix of DNA is a dynamically changing structure. The structure relates to interactions between and within the DNA strands, and the array of other macromolecules that constitutes functional chromatin. It is only through its changing conformations that DNA can organize and structure a large number of cellular functions. In particular, DNA must locally uncoil, or melt, and become single-stranded for DNA replication, repair, recombination, and transcription to occur. It has previously been shown that this melting occurs cooperatively, whereby several base pairs act in concert to generate melting bubbles, and in this way constitute a domain that behaves as a unit with respect to local DNA single-strandedness. We have applied a melting map calculation to the complete human genome, which provides information about the propensities of forming local bubbles determined from the whole sequence, and present a first report on its basic features, the extent of cooperativity, and correlations to various physical and biological features of the human genome. Globally, the melting map covaries very strongly with GC content. Most importantly, however, cooperativity of DNA denaturation causes this correlation to be weaker at resolutions fewer than 500 bps. This is also the resolution level at which most structural and biological processes occur, signifying the importance of the informational content inherent in the genomic melting map. The human DNA melting map may be further explored at http://meltmap.uio.no. PMID:17511513

Liu, Fang; Tøstesen, Eivind; Sundet, Jostein K; Jenssen, Tor-Kristian; Bock, Christoph; Jerstad, Geir Ivar; Thilly, William G; Hovig, Eivind

2007-01-01

205

International Conference on Microwave and High Frequency Heating, AMPERE-2013 Nottingham, UK, September 2013 Basalt Melting by Localized-Microwave  

E-print Network

, September 2013 255 Basalt Melting by Localized-Microwave Thermal-Runaway Instability E. Jerby*, Y. Meir, M an experimental and theoretical study of the thermal-runaway instability induced by localized microwaves in basalt stones. This effect leads to the inner melting of the basalt core, and further to its eruption similarly

Jerby, Eli

206

Hot melt adhesive attachment pad  

NASA Technical Reports Server (NTRS)

A hot melt adhesive attachment pad for releasably securing distinct elements together is described which is particularly useful in the construction industry or a spatial vacuum environment. The attachment pad consists primarily of a cloth selectively impregnated with a charge of hot melt adhesive, a thermo-foil heater, and a thermo-cooler. These components are securely mounted in a mounting assembly. In operation, the operator activates the heating cycle transforming the hot melt adhesive to a substantially liquid state, positions the pad against the attachment surface, and activates the cooling cycle solidifying the adhesive and forming a strong, releasable bond.

Fox, R. L.; Frizzill, A. W.; Little, B. D.; Progar, D. J.; Coultrip, R. H.; Couch, R. H.; Gleason, J. R.; Stein, B. A.; Buckley, J. D.; St.clair, T. L. (inventors)

1984-01-01

207

Polar basal melting on Mars  

NASA Astrophysics Data System (ADS)

The potential importance of basal melting on Mars is illustrated through the discussion of four examples: (1) the origin of the major polar reentrants, (2) the removal and storage of an ancient Martian ice sheet, (3) the mass balance of the polar terrains, and (4) the possibility of basal melting at temperate latitudes. This analysis suggests that the process of basal melting may play a key role in understanding the evolution of the Martian polar terrains and the long-term climatic behavior of water on Mars.

Clifford, S. M.

1987-08-01

208

Temperament, recalled parenting styles, and self-regulation: testing the developmental postulates of self-discrepancy theory.  

PubMed

Self-discrepancy theory (SDT) postulates that self-regulatory systems corresponding to the ideal and ought self-domains emerge from the influences of temperament (e.g., sensitivity to stimuli for positive vs. negative outcomes) and socialization (e.g., parenting behaviors and interpersonal outcome contingencies). This article reports 2 studies testing the developmental postulates of SDT concurrently and retrospectively. Study 1 showed that self-regulation with reference to the ideal vs. the ought domain was differentially associated with recollections of parenting styles of warmth and rejection, respectively. In Study 2, these findings were replicated, and self-regulation with reference to the ideal vs. ought domain was discriminantly associated with questionnaire measures of positive vs. negative temperament. Findings support the developmental postulates of SDT, despite the limitations of retrospective studies. PMID:9866190

Manian, N; Strauman, T J; Denney, N

1998-11-01

209

Secular evolution of partial melting and melt stagnation during the formation of Godzilla Mullion, Philippine Sea  

NASA Astrophysics Data System (ADS)

Godzilla Mullion is a large-scale low angle detachment fault (or OCC, Oceanic Core Complex) formed during backarc spreading in the Parece Vela Rift behind the Mariana arc system. Detachment spreading occurred during the time interval 15-12 Ma, before the Parece Vela Rift became extinct and the locus of back arc spreading in the system shifted to the East, to the Mariana Trough. During this time, the spreading rate varied from ~70-88 mm/year to zero (at extinction). The decline in the spreading rate, should have had profound effects on the thermal structure of the lithosphere in the rift, including include progressive thickening, decreasing degree of partial melting, and increasing melt stagnation. We have combined our preliminary data on mantle peridotite mineral chemistry to form a preliminary test of this hypothesis based on mantle peridotites from (currently) 10 sampling stations along the mullion from the cruises CSS33, KR03-01, KH07-02 and YK09-05. This test is for now based primarily on abyssal peridotite spinel chemistry (Dick and Bullen, 1982; Dick 1989). We can distinguish three distinct regions within the mullion based on spinel chemistry: (1) The Distal GM region, including sites KR03-01-D6, KH07-02-D17 and KH07-02-D7. These have a moderately depleted character, with minimum Cr-numbers between 30 and 40, and few samples with high TiO2 (an indicator of melt impregnation). (2) The Medial GM region, including stations KH07-02-D6, KR03-01-D7, KH07-02-D21 and YK09-05-6K#1142. These have a more fertile character, with minimum Cr-numbers between 14 and 22, and with the exception of KH07-02-21 (which may belong to the next group) little evidence of melt stagnation. (3) The Proximal GM region, including sites KR0301-D9 and D10 and CSS33-D1. These spinels show abundant evidence for melt reaction, including plagioclase pseudomorphs (See abstract by Loocke et al., this session) and pervasively elevated TiO2 contents and Cr-numbers in the spinels. We can interpret these variations in the framework of a declining magmatic system as described above. The Distal GM represents the mantle of a robust magmatic system underlying and feeding normal abyssal hill topography to the SW of the GM breakaway. The Medial GM represents mantle that has a lowered melt productivity, but has not yet switched from thin-lithospheric, eruptive magmatism to active melt stagnation. The proximal GM region represents mantle from near the end of Parece Vela Rift spreading, in which the lithosphere has thickened sufficiently to trap some or most of the melts arising from the melting zone, resulting in Cr-numbers that are elevated once again along with pervasive TiO2 enrichments thought to be typical of extensive melt stagnation.

Snow, J. E.; Ohara, Y.; Harigane, Y.; Michibayashi, K.; Hellebrand, E.; von der Handt, A.; Loocke, M.; Ishii, T.

2009-12-01

210

Melting granites to make granites  

NASA Astrophysics Data System (ADS)

Large-scale partial melting in the continental crust is widely attributed to fluid-absent incongruent breakdown of hydrous minerals in the case of pelites, greywackes and meta-mafic rocks. Granite is a far more common rock in the continental crust, but fluid-absent hydrate-breakdown melting is unlikely to result in significant melting in granites because of their low modal abundance of mica or amphibole. Experiments show that fluid-present melting can produce ~30% melt at low temperatures (690°C). Thus, granites and leucogranites can be very fertile if H2O-present melting occurs via reactions such as plagioclase + quartz + K-feldspar + H2O = melt, because of their high modal proportions of the reactant phases. Our study investigates the Kinawa Migmatite in the São Francisco Craton, southeastern Brazil. This migmatite is derived from an Archaean TTG sequence and can be divided into; 1) pink diatexites, 2) leucosomes, 3) grey gneisses and 4) amphibolites. The migmatite records upper-amphibolite to beginning of granulite facies metamorphism in a P-T range from 5.1-6.6 kbar and ~650-780°C. Pink diatexites are the most abundant rocks, and their appearance varies depending on the amount of melt they contained. Three types are recognised: residual diatexites (low melt fraction (Mf)), schlieren diatexites (moderate Mf) and homogeneous diatexites (high Mf). They are very closely related spatially in the field, with mostly transitional contacts. There is a sequence with progressive loss of ferromagnesian minerals, schollen and schlieren through the sequence to the most melt-rich parts of the diatexites as magmatic flow became more intense. There are fewer ferromagnesian minerals, thus the melt becomes cleaner (more leucocratic) and, because the schlieren have disaggregated the aspect is more homogeneous. These parts are texturally similar to leucogranites in which the biotite is randomly distributed and pre-melting structures are completely destroyed. The likely protolith for the migmatites was a leucocratic granodiorite (with modal K-feldspar up to 30% and biotite up to 5%), and from geochemical modelling the degree of partial melting ranged from 0.21 to 0.25. Furthermore, the residual diatexites show a complementary low modal proportion, or even absence, of K-feldspar, but an increase in modal plagioclase, quartz (up to 56 and 37% respectively) and biotite (5-16%). This suggests that the melting reaction did not involve biotite and that plagioclase and quartz were in excess. As result the melt generated is fairly leucocratic, and most of the mafic phases in it are inherited. Anatectic melts in the Kinawa Migmatite were mildly metaluminous and distinctly leucocratic (A/CNK from 0.97 to 1.01; SiO2 from 72.8 to 75.65%; (FeOT+MgO+TiO2) from 0.49 to 2.3%). Since most granites have a higher (FeOT+MgO+TiO2), additional processes must add the "mafic component" to these melts before they form plutons.

Carvalho, Bruna B.; Sawyer, Edward W.; Janasi, Valdecir de A.

2014-05-01

211

DUBLIN CORE  

EPA Science Inventory

The Dublin Core is a metadata element set intended to facilitate discovery of electronic resources. It was originally conceived for author-generated descriptions of Web resources, and the Dublin Core has attracted broad ranging international and interdisciplinary support. The cha...

212

Analysis of a Schnute postulate-based unified growth mode for model selection in evolutionary computations  

PubMed Central

In order to evaluate the feasibility of a combined evolutionary algorithm-information theoretic approach to select the best model from a set of candidate invasive species models in ecology, and/or to evolve the most parsimonious model from a suite of competing models by comparing their relative performance, it is prudent to use a unified model that covers a myriad of situations. Using Schnute’s postulates as a starting point, we present a single, unified model for growth that can be successfully utilized for model selection in evolutionary computations. Depending on the parameter settings, the unified equation can describe several growth mechanisms. Such a generalized model mechanism, which encompasses a suite of competing models, can be successfully implemented in evolutionary computational algorithms to evolve the most parsimonious model that best fits ground truth data. We have done exactly this by testing the effectiveness of our reaction-diffusion-advection (RDA) model in an evolutionary computation model selection algorithm. The algorithm was validated (with success) against field data sets of the Zebra mussel invasion of Lake Champlain in the United States. PMID:17197072

Bentil, D.E.; Osei, B.M.; Ellingwood, C.D.; Hoffmann, J.P.

2007-01-01

213

Analysis of a Schnute postulate-based unified growth model for model selection in evolutionary computations.  

PubMed

In order to evaluate the feasibility of a combined evolutionary algorithm-information theoretic approach to select the best model from a set of candidate invasive species models in ecology, and/or to evolve the most parsimonious model from a suite of competing models by comparing their relative performance, it is prudent to use a unified model that covers a myriad of situations. Using Schnute's postulates as a starting point [Schnute, J., 1981. A versatile growth model with statistically stable parameters, Can. J. Fish Aquat. Sci. 38, 1128-1140], we present a single, unified model for growth that can be successfully utilized for model selection in evolutionary computations. Depending on the parameter settings, the unified equation can describe several growth mechanisms. Such a generalized model mechanism, which encompasses a suite of competing models, can be successfully implemented in evolutionary computational algorithms to evolve the most parsimonious model that best fits ground truth data. We have done exactly this by testing the effectiveness of our reaction-diffusion-advection (RDA) model in an evolutionary computation model selection algorithm. The algorithm was validated (with success) against field data sets of the Zebra mussel invasion of Lake Champlain in the United States. PMID:17197072

Bentil, D E; Osei, B M; Ellingwood, C D; Hoffmann, J P

2007-01-01

214

Serum-derived bovine immunoglobulin/protein isolate: postulated mechanism of action for management of enteropathy  

PubMed Central

The health and performance of the gastrointestinal tract is influenced by the interaction of a variety of factors, including diet, nutritional status, genetics, environment, stress, the intestinal microbiota, immune status, and gut barrier. Disruptions in one or more of these factors can lead to enteropathy or intestinal disorders that are known to occur in concert with certain disease states or conditions such as irritable bowel syndrome or human immunodeficiency virus (HIV) infection. Nutritional support in the form of a medical food along with current therapies could help manage the adverse effects of enteropathy, which include effects on nutrient digestion, absorption, and metabolism, as well as utilization of nutrients from foodstuffs. Numerous studies have demonstrated that oral administration of plasma- or serum-derived protein concentrates containing high levels of immunoglobulins can improve weight management, normalize gut barrier function, and reduce the severity of enteropathy in animals. Recent trials in humans provide preliminary evidence that a serum-derived bovine immunoglobulin/protein isolate is safe and improves symptoms, nutritional status, and various biomarkers associated with enteropathy in patients with HIV infection or diarrhea-predominant irritable bowel syndrome. This review summarizes data from preclinical and clinical studies with immunoglobulin-containing plasma/serum protein concentrates, with a focus on the postulated mode of action of serum-derived bovine immunoglobulin/protein isolate for patients with enteropathy. PMID:24904221

Petschow, Bryon W; Burnett, Bruce; Shaw, Audrey L; Weaver, Eric M; Klein, Gerald L

2014-01-01

215

An Ambiguous Statement Called 'Tetrad Postulate' and the Correct Field Equations Satisfied by the Tetrad Fields  

E-print Network

The names tetrad, tetrads, cotetrads, have been used with many different meanings in the physical literature, not all of them, equivalent from the mathematical point of view. In this paper we introduce unambiguous definitions for each one of those terms, and show how the old miscellanea made many authors to introduce in their formalism an ambiguous statement called `tetrad postulate', which has been source of many misunderstandings, as we show explicitly examining examples found in the literature. Since formulating Einstein's field equations intrinsically in terms of cotetrad fields theta^{a}, a = 0,1,2,3 is an worth enterprise, we derive the equation of motion of each theta^{a} using modern mathematical tools (the Clifford bundle formalism and the theory of the square of the Dirac operator). Indeed, we identify (giving all details and theorems) from the square of the Dirac operator some noticeable mathematical objects, namely, the Ricci, Einstein, covariant D'Alembertian and the Hodge Laplacian operators, which permit to show that each theta^{a} satisfies a well defined wave equation. Also, we present for completeness a detailed derivation of the cotetrad wave equations from a variational principal. We compare the cotetrad wave equation satisfied by each theta^{a} with some others appearing in the literature, and which are unfortunately in error.

Waldyr A. Rodrigues Jr.; Quintino A. Gomes de Souza

2008-01-06

216

Nuclear reactor melt-retention structure to mitigate direct containment heating  

DOEpatents

A light water nuclear reactor melt-retention structure to mitigate the extent of direct containment heating of the reactor containment building. The structure includes a retention chamber for retaining molten core material away from the upper regions of the reactor containment building when a severe accident causes the bottom of the pressure vessel of the reactor to fail and discharge such molten material under high pressure through the reactor cavity into the retention chamber. In combination with the melt-retention chamber there is provided a passageway that includes molten core droplet deflector vanes and has gas vent means in its upper surface, which means are operable to deflect molten core droplets into the retention chamber while allowing high pressure steam and gases to be vented into the upper regions of the containment building. A plurality of platforms are mounted within the passageway and the melt-retention structure to direct the flow of molten core material and help retain it within the melt-retention chamber. In addition, ribs are mounted at spaced positions on the floor of the melt-retention chamber, and grid means are positioned at the entrance side of the retention chamber. The grid means develop gas back pressure that helps separate the molten core droplets from discharged high pressure steam and gases, thereby forcing the steam and gases to vent into the upper regions of the reactor containment building.

Tutu, Narinder K. (Manorville, NY); Ginsberg, Theodore (East Setauket, NY); Klages, John R. (Mattituck, NY)

1991-01-01

217

The Rheologic Implications of Partial Melting in Continental Plateaux  

NASA Astrophysics Data System (ADS)

Partial melting plays a fundamental role in the evolution of orogens and continental plateaux. When crustal material partially melts during high-grade metamorphism or crystallizes during cooling and exhumation, its viscosity abruptly changes by several orders of magnitude. Using Ellipsis, a 2D Lagrangian integration point finite-element code, we investigate the effect a melt-fraction dependent viscosity has on temperature, density, and overall dynamics of orogens and continental plateaux. One series of experiments (EXP-1) investigates the dynamics of continental plateaux with the goal to better understand the role of lateral (channel) flow of partially molten crust from the plateau to the foreland (channel extrusion) relative to other mechanisms of orogenic collapse. Another set of experiments (EXP-2) zooms in the extension of thick crust and the development of metamorphic core complexes that are commonly cored by migmatite domes (crystallized partial melt). (EXP-1) The transition dynamics from orogenic plateau to foreland is modeled for the cases of fixed-boundary collapse, where material is redistributed internally, slow-convergence collapse, and slow- to fast-divergence collapse. Fixed and convergent collapse illustrate the dynamic links between plateau extension and foreland contraction; the partially molten crust flows laterally and “intrudes” the foreland crust in the form of a midcrustal channel that reaches a maximum of 150 km from the plateau-foreland boundary. In divergent collapse, lateral flow of the partially molten crust is inhibited by extension in the plateau upper crust that makes room for the partially molten crust to flow, creating a migmatite-cored metamorphic core complex, particularly when buoyancy forces are taken into account. Results indicate that cooling of the extruded channel, plateau extension, and buoyancy of partially molten crust are limiting factors for channel extrusion, which cannot be a plateau-building mechanism. (EXP-2) The role of extensional strain rates is considered because heat advection, which is related to both extension rate and the buoyant transfer of lower crust into upper crust, competes with the conductive cooling of the thinning crust. By comparing model results with natural examples of metamorphic core complexes we show that the position of the migmatite core complexes, the depth at which crystallization occurs, the shape of pressure-temperature-time (P-T-t) paths, the particle flow paths, and the finite strain are critically dependent on extensional strain rates and to a lesser extent on melt fraction.

Teyssier, C.; Whitney, D. L.; Rey, P. F.

2009-12-01

218

Postcumulus Processes in Oceanic-Type Olivine-Rich Cumulates: the Role of Melt Entrapment vs. Melt-Rock Interaction  

NASA Astrophysics Data System (ADS)

Evaluation of postcumulus processes in cumulate rocks can provide insights on the mechanisms and scales of melt migration and interaction within the crust, thus contributing to define crustal accretion models. Here we present a microstructural-geochemical study on MORB-type primitive olivine-rich cumulates intruded in the Erro-Tobbio (ET) mantle peridotites (Voltri Massif, Ligurian Alps, Italy), an on-land analogue of (ultra-) slow spreading settings. Postcumulus crystallization is indicated by the occurrence of accessory interstitial minerals (Ti- pargasite, opx , Fe-Ti oxides), and by chemical zoning in intercumulus clinopyroxene related to its textural occurence, i.e. marked REE, Ti, Zr enrichment at almost constant Mg-numbers (88-90) and LREE depletion, from core to rim of coarse anhedral clinopyroxene, to thin vermicular cpx grains. Interstitial pargasites have high Nb, Zr, REE contents although preserving "primitive" major element compositions (Mgvalue = 0.86-0.89) and LREE depletion. Significant trace element enrichment at almost constant LREE fractionation in interstitial clinopyroxenes and Ti-rich pargasites argue against the infiltration of exotic evolved melts and indicate that interstitial minerals were mainly related to close-system trapped melt crystallization. Geochemical modeling shows that crystallization of less than 5% trapped melt is sufficient to produce the REE enrichments observed in cpx. The progressive increase in (REE-Zr-Ti) abundances from core to rim of large clinopyroxene grains is accounted by an "in-situ" fractional crystallization process. Anomalous Zr enrichment is observed in thin (< 400 µm) interstitial and vermicular clinopyroxenes and pargasitic amphiboles, representing the very last melt fraction (reasonably < 2%). At this final crystallization stage, the low residual porosity likely inhibited large-scale melt migration. AFC modeling indicates that the high Zr/Nd ratios in cpx could be related to small-scale migration and interaction between residual, evolved, low melt fractions and the olivine cumulus matrix, consistent with textural evidence of lobate contacts between vermicular clinopyroxenes and cumulus olivine, indicative of partial olivine resorption. Our study points that small amount of melt trapped in an olivine-rich matrix can induce significant trace element enrichment in minerals. Such an evidence argue against large-scale residual melt migration, this latter being controlled by porosity and permeability of the crystal mush, and indicates that compaction was very efficient. This could have been favoured by the interplay of different factors, i.e. slow cooling rates and low thermal gradients, and synkinematic deformation (Natland and Dick, 2001, J. V. G. Res, 110, 191-233). The ET cumulates could thus represent the base of a stack of cumulates (3-5 Kb intrusion depth) from which differentiated melts migrated upwards and crystallized at shallower lithospheric environments. Overall, this indicates that different melt transport and interaction processes may act during crust accretion at very slow spreading settings, e.g. low melt fraction entrapment of indigenous melts in compaction-dominated deep-seated gabbroic intrusions vs. migration of exotic evolved melts through uppermost crustal levels.

Borghini, G.; Rampone, E.

2008-12-01

219

A discontinuous melt sheet in the Manson impact structure  

NASA Technical Reports Server (NTRS)

Petrologic studies of the core recovered from holes drilled in the Manson, Iowa, buried impact structure may unravel the thermal history of the crater-fill debris. We made a cursory examination of about 200 m of core recovered from the M-1 bore hole. The M-1 bore hole was the first of 12 holes drilled as part of a cooperative drilling program between the U.S. Geological Survey and the Iowa Geological Survey Bureau. The M-1 core hole is about 6 km northeast of the center of the impact structure, apparently on the flank of its central peak. We developed a working hypothesis that a 30-m-thick breccia unit within a 53-m-thick unit previously termed the 'crystalline clast breccia with glassy matrix' is part of a discontinuous melt sheet in the crater-fill impact debris. The 30-m-thick breccia unit reached temperatures sufficient to partially melt some small breccia clasts and convert the fine-grained breccia matrix into a silicate melt that cooled to a greenish-black, flinty, microcrystalline rock. The results of the investigation of this unit are presented.

Izett, G. A.; Reynolds, R. L.; Rosenbaum, J. G.; Nishi, J. M.

1993-01-01

220

Evidence for fractional crystallization of wadsleyite and ringwoodite from olivine melts in chondrules entrained in shock-melt veins.  

PubMed

Peace River is one of the few shocked members of the L-chondrites clan that contains both high-pressure polymorphs of olivine, ringwoodite and wadsleyite, in diverse textures and settings in fragments entrained in shock-melt veins. Among these settings are complete olivine porphyritic chondrules. We encountered few squeezed and flattened olivine porphyritic chondrules entrained in shock-melt veins of this meteorite with novel textures and composition. The former chemically unzoned (Fa(24-26)) olivine porphyritic crystals are heavily flattened and display a concentric intergrowth with Mg-rich wadsleyite of a very narrow compositional range (Fa(6)-Fa(10)) in the core. Wadsleyite core is surrounded by a Mg-poor and chemically stark zoned ringwoodite (Fa(28)-Fa(38)) belt. The wadsleyite-ringwoodite interface denotes a compositional gap of up to 32 mol % fayalite. A transmission electron microscopy study of focused ion beam slices in both regions indicates that the wadsleyite core and ringwoodite belt consist of granoblastic-like intergrowth of polygonal crystallites of both ringwoodite and wadsleyite, with wadsleyite crystallites dominating in the core and ringwoodite crystallites dominating in the belt. Texture and compositions of both high-pressure polymorphs are strongly suggestive of formation by a fractional crystallization of the olivine melt of a narrow composition (Fa(24-26)), starting with Mg-rich wadsleyite followed by the Mg-poor ringwoodite from a shock-induced melt of olivine composition (Fa(24-26)). Our findings could erase the possibility of the resulting unrealistic time scales of the high-pressure regime reported recently from other shocked L-6 chondrites. PMID:18562280

Miyahara, Masaaki; El Goresy, Ahmed; Ohtani, Eiji; Nagase, Toshiro; Nishijima, Masahiko; Vashaei, Zahra; Ferroir, Tristan; Gillet, Philippe; Dubrovinsky, Leonid; Simionovici, Alexandre

2008-06-24

221

Evidence for fractional crystallization of wadsleyite and ringwoodite from olivine melts in chondrules entrained in shock-melt veins  

PubMed Central

Peace River is one of the few shocked members of the L-chondrites clan that contains both high-pressure polymorphs of olivine, ringwoodite and wadsleyite, in diverse textures and settings in fragments entrained in shock-melt veins. Among these settings are complete olivine porphyritic chondrules. We encountered few squeezed and flattened olivine porphyritic chondrules entrained in shock-melt veins of this meteorite with novel textures and composition. The former chemically unzoned (Fa24–26) olivine porphyritic crystals are heavily flattened and display a concentric intergrowth with Mg-rich wadsleyite of a very narrow compositional range (Fa6–Fa10) in the core. Wadsleyite core is surrounded by a Mg-poor and chemically stark zoned ringwoodite (Fa28–Fa38) belt. The wadsleyite–ringwoodite interface denotes a compositional gap of up to 32 mol % fayalite. A transmission electron microscopy study of focused ion beam slices in both regions indicates that the wadsleyite core and ringwoodite belt consist of granoblastic-like intergrowth of polygonal crystallites of both ringwoodite and wadsleyite, with wadsleyite crystallites dominating in the core and ringwoodite crystallites dominating in the belt. Texture and compositions of both high-pressure polymorphs are strongly suggestive of formation by a fractional crystallization of the olivine melt of a narrow composition (Fa24–26), starting with Mg-rich wadsleyite followed by the Mg-poor ringwoodite from a shock-induced melt of olivine composition (Fa24–26). Our findings could erase the possibility of the resulting unrealistic time scales of the high-pressure regime reported recently from other shocked L-6 chondrites. PMID:18562280

Miyahara, Masaaki; El Goresy, Ahmed; Ohtani, Eiji; Nagase, Toshiro; Nishijima, Masahiko; Vashaei, Zahra; Ferroir, Tristan; Gillet, Philippe; Dubrovinsky, Leonid; Simionovici, Alexandre

2008-01-01

222

Starless Cores  

E-print Network

Dense low mass cores in nearby clouds like Taurus and Auriga are some of the simplest sites currently forming stars like our Sun. Because of their simplicity and proximity, dense cores offer the clearest view of the different phases of star formation, in particular the conditions prior to the onset of gravitational collapse. Thanks to the combined analysis of the emission from molecular lines and the emission/absorption from dust grains, the last several years have seen a very rapid progress in our understanding of the structure and chemical composition of starless cores. Previous contradictions between molecular tracers are now understood to arise from core chemical inhomogeneities, which are caused by the selective freeze out of molecules onto cold dust grains. The analysis of the dust emission and absorption, in addition, has allowed us to derive accurate density profiles, and has made finally possible to carry out self consistent modeling of the internal structure of starless cores. In this paper I briefly review the evolution of core studies previous to the current golden age, and show how multi-tracer emission can now be modeled in a systematic manner. Finally I show how we can start to reconstruct the early history of core formation taking advantage of the chemical changes in the gas.

Mario Tafalla

2005-04-23

223

Scaleable Clean Aluminum Melting Systems  

SciTech Connect

The project entitled 'Scaleable Clean Aluminum Melting Systems' was a Cooperative Research and Development Agreements (CRADAs) between Oak Ridge National Laboratory (ORNL) and Secat Inc. The three-year project was initially funded for the first year and was then canceled due to funding cuts at the DOE headquarters. The limited funds allowed the research team to visit industrial sites and investigate the status of using immersion heaters for aluminum melting applications. Primary concepts were proposed on the design of furnaces using immersion heaters for melting. The proposed project can continue if the funding agency resumes the funds to this research. The objective of this project was to develop and demonstrate integrated, retrofitable technologies for clean melting systems for aluminum in both the Metal Casting and integrated aluminum processing industries. The scope focused on immersion heating coupled with metal circulation systems that provide significant opportunity for energy savings as well as reduction of melt loss in the form of dross. The project aimed at the development and integration of technologies that would enable significant reduction in the energy consumption and environmental impacts of melting aluminum through substitution of immersion heating for the conventional radiant burner methods used in reverberatory furnaces. Specifically, the program would couple heater improvements with furnace modeling that would enable cost-effective retrofits to a range of existing furnace sizes, reducing the economic barrier to application.

Han, Q.; Das, S.K. (Secat, Inc.)

2008-02-15

224

Modeling energy balance and melt layer formation on the Kahiltna Glacier, Alaska  

NASA Astrophysics Data System (ADS)

Understanding melt on alpine glaciers is required both for accurate mass balance modeling and ice core paleoclimate reconstruction. In alpine regions with complex meteorology and topography, modeling melt through the quantification and balance of all identifiable energy fluxes is the most complete way of describing how local meteorology influences melt layer formation and snowpack evolution. To meet this goal at our field site on the Kahiltna glacier, located in the Central Alaska Range, Denali National Park, we have developed an energy balance model from two years of meteorological data from Kahiltna Base Camp (2100 m elevation, 63.25 degrees N, 151 degrees W). Current model results show the dominance of turbulent heat transfer at the study site and the importance of surface roughness and albedo in controlling melt. Preliminary data show a 30 percent overestimation of melt flux from the surface into the snowpack although an albedo submodel is being developed which may address this. Sampling of the snowpack across the glacier for analysis of stratigraphic and chemical evolution shows an isothermal near surface snowpack (to at least 1m) at 2100 meters in elevation in the early melt season with increasing density and melt layer abundance as the summer progresses. This suggests that a large amount of the meltwater remains in the snowpack after surface melting. We will discuss further the model’s accuracy in relation to ablation stake measurements as well as the major environmental controls on physical and chemical snowpack evolution into the melt season as additional results are processed.

Winski, D. A.; Kreutz, K. J.; Osterberg, E. C.; Campbell, S. W.; Denali Ice Core Team

2010-12-01

225

Westinghouse Small Modular Reactor passive safety system response to postulated events  

SciTech Connect

The Westinghouse Small Modular Reactor (SMR) is an 800 MWt (>225 MWe) integral pressurized water reactor. This paper is part of a series of four describing the design and safety features of the Westinghouse SMR. This paper focuses in particular upon the passive safety features and the safety system response of the Westinghouse SMR. The Westinghouse SMR design incorporates many features to minimize the effects of, and in some cases eliminates the possibility of postulated accidents. The small size of the reactor and the low power density limits the potential consequences of an accident relative to a large plant. The integral design eliminates large loop piping, which significantly reduces the flow area of postulated loss of coolant accidents (LOCAs). The Westinghouse SMR containment is a high-pressure, compact design that normally operates at a partial vacuum. This facilitates heat removal from the containment during LOCA events. The containment is submerged in water which also aides the heat removal and provides an additional radionuclide filter. The Westinghouse SMR safety system design is passive, is based largely on the passive safety systems used in the AP1000{sup R} reactor, and provides mitigation of all design basis accidents without the need for AC electrical power for a period of seven days. Frequent faults, such as reactivity insertion events and loss of power events, are protected by first shutting down the nuclear reaction by inserting control rods, then providing cold, borated water through a passive, buoyancy-driven flow. Decay heat removal is provided using a layered approach that includes the passive removal of heat by the steam drum and independent passive heat removal system that transfers heat from the primary system to the environment. Less frequent faults such as loss of coolant accidents are mitigated by passive injection of a large quantity of water that is readily available inside containment. An automatic depressurization system is used to reduce the reactor pressure in a controlled manner to facilitate the passive injection. Long-term decay heat removal is accomplished using the passive heat removal systems augmented by heat transfer through the containment vessel to the environment. The passive injection systems are designed so that the fuel remains covered and effectively cooled throughout the event. Like during the frequent faults, the passive systems provide effective cooling without the need for ac power for seven days following the accident. Connections are available to add additional water to indefinitely cool the plant. The response of the safety systems of the Westinghouse SMR to various initiating faults has been examined. Among them, two accidents; an extended station blackout event, and a LOCA event have been evaluated to demonstrate how the plant will remain safe in the unlikely event that either should occur. (authors)

Smith, M. C.; Wright, R. F. [Westinghouse Electric Company, 600 Cranberry Woods Drive (United States)

2012-07-01

226

Frictional melting and stick-slip behavior in volcanic conduits  

NASA Astrophysics Data System (ADS)

Dome-building eruptions have catastrophic potential, with dome collapse leading to devastating pyroclastic flows with almost no precursory warning. During dome growth, the driving forces of the buoyant magma may be superseded by controls along conduit margins; where brittle fracture and sliding can lead to formation of lubricating cataclasite and gouge. Under extreme friction, pseudotachylyte may form at the conduit margin. Understanding the conduit margin processes is vital to understanding the continuation of an eruption and we postulate that pseudotachylyte generation could be the underlying cause of stick-slip motion and associated seismic "drumbeats", which are so commonly observed at dome-building volcanoes. This view is supported by field evidence in the form of pseudotachylytes identified in lava dome products at Soufrière Hills (Montserrat) and Mount St. Helens (USA). Both eruptions were characterised by repetitive, periodic seismicity and lava spine extrusion of highly viscous magma. High velocity rotary shear (HVR) experiments demonstrate the propensity for melting of the andesitic and dacitic material (from Soufrière Hills and Mount St. Helens respectively) at upper conduit stress conditions (<10 MPa). Starting from room temperature, frictional melting of the magmas occurs in under 1 s (<< 1 m) at 1.5 m/s (a speed that is achievable during stick-slip motion). At lower velocities melting occurs comparatively later due to dissipation of heat from the slip zone (e.g. 8-15 m at 0.1 m/s). Hence, given the ease with which melting is achieved in volcanic rocks, and considering the high ambient temperatures in volcanic conduits, frictional melting may thus be an inevitable consequence of viscous magma ascent. The shear resistance of the slip zone during the experiment is also monitored. Frictional melting induces a higher resistance to sliding than rock on rock, and viscous processes control the slip zone properties. Variable-rate HVR experiments which mimic rapid velocity fluctuations in stick-slip behavior demonstrate velocity-weakening behavior of melt, with a tendency for unstable slip. During ascent, magma may slip and undergo melting along the conduit margin. In the process the shear resistance of the slip zone is increased, acting as a viscous brake halting slip (the "stick" of stick-slip motion). Sufficient buoyancy-driven pressures from ascending magma below eventually overcome resistance to produce a rapid slip event (the "slip") along the melt-bearing slip zone, which is temporarily lubricated due to velocity-weakening. New magma below experiences the same slip event more slowly (as the magma decompresses) to produce a viscous brake and the process is repeated. This allows a fixed spatial locus that explains the repetitive drumbeat seismicity and the occurrence of "families" of similar seismic events. We conclude that stick-slip motion in volcanic conduits is a self-driving, frictional-melt-regulated force common to many dome building volcanoes.

Kendrick, Jackie Evan; Lavallee, Yan; Hirose, Takehiro; di Toro, Giulio; Hornby, Adrian Jakob; Hess, Kai-Uwe; Dingwell, Donald Bruce

2013-04-01

227

An adult zebrafish model for Laribacter hongkongensis infection: Koch's postulates fulfilled  

PubMed Central

Laribacter hongkongensis is a gram-negative emerging bacterium associated with invasive bacteremic infections in patients with liver disease and fish-borne community-acquired gastroenteritis and traveler's diarrhea. Although the complete genome of L. hongkongensis has been sequenced, no animal model is available for further study of its pathogenicity mechanisms. In this study, we showed that adult zebrafish infected with L. hongkongensis by immersion following dermal abrasion or intraperitoneal injection suffered mortality in a dose-dependent manner, with lethal dose 50 (LD50) of 2.1×104 and 1.9×104?colony-forming units (CFU)/mL, respectively. All mortalities occurred in the first four days post-infection. Zebrafish that died showed characteristic clinicopathological features: swimming near water surface, marked lethargy and sidestroke; abdominal hemorrhage, ulcers and marked swelling with ascites; and hydropic degeneration and necrosis of hepatocytes around central vein and inflammatory cells infiltration. L. hongkongensis was recovered from the ascitic fluid and tissues of zebrafish that died. Of the 30 zebrafish infected with 2.1×104?CFU/mL (LD50) L. hongkongensis isolated from dead zebrafish using the immersion following dermal abrasion method, 18 (60%) died. All zebrafish that died also showed the characteristic clinical and pathological features. Histopathological studies also showed dilation of hepatic central vein and hydropic degeneration. L. hongkongensis was isolated from the zebrafish that died. The Koch's postulates for L. hongkongensis as an infectious agent have been fulfilled. This highly reproducible and effective zebrafish model is of crucial importance for future studies on virulence factors for L. hongkongensis infection.

Xie, Jun; He, Jia-Bei; Shi, Jia-Wei; Xiao, Qiang; Li, Ling; Woo, Patrick CY

2014-01-01

228

Implications of dairy systems on enteric methane and postulated effects on total greenhouse gas emission.  

PubMed

The effects of feeding total mixed ration (TMR) or pasture forage from a perennial sward under a management intensive grazing (MIG) regimen on grain intake and enteric methane (EM) emission were measured using chambers. Chamber measurement of EM was compared with that of SF6 employed both within chamber and when cows grazed in the field. The impacts of the diet on farm gate greenhouse gas (GHG) emission were also postulated using the results of existing life cycle assessments. Emission of EM was measured in gas collection chambers in Spring and Fall. In Spring, pasture forage fiber quality was higher than that of the silage used in the TMR (47.5% v. 56.3% NDF; 24.3% v. 37.9% ADF). Higher forage quality from MIG subsequently resulted in 25% less grain use relative to TMR (0.24 v. 0.32 kg dry matter/kg milk) for MIG compared with TMR. The Fall forage fiber quality was still better, but the higher quality of MIG pasture was not as pronounced as that in Spring. Neither yield of fat-corrected milk (FCM) which averaged 28.3 kg/day, nor EM emission which averaged 18.9 g/kg dry matter intake (DMI) were significantly affected by diet in Spring. However, in the Fall, FCM from MIG (21.3 kg/day) was significantly lower than that from TMR (23.4 kg/day). Despite the differences in FCM yield, in terms of EM emission that averaged 21.9 g/kg DMI was not significantly different between the diets. In this study, grain requirement, but not EM, was a distinguishing feature of pasture and confinement systems. Considering the increased predicted GHG emissions arising from the production and use of grain needed to boost milk yield in confinement systems, EM intensity alone is a poor predictor of the potential impact of a dairy system on climate forcing. PMID:23896042

Fredeen, A; Juurlink, S; Main, M; Astatkie, T; Martin, R C

2013-11-01

229

24. A CORE WORKER DISPLAYS THE CORE BOX AND CORES ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

24. A CORE WORKER DISPLAYS THE CORE BOX AND CORES FOR A BRASS GATE VALVE BODY MADE ON A CORE BOX, CA. 1950. - Stockham Pipe & Fittings Company, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

230

Melting Point, Density, and Reactivity of Metals  

Microsoft Academic Search

The density and melting point of a metal, taken together, can give a useful qualitative guide to the chemical reactivity of the metal. A high density and high melting point indicate a low reactivity; conversely, low density and low melting point indicate high reactivity. The melting point is allied to the heat of sublimation; the density gives a guide to

Michael Laing

2001-01-01

231

Downward melt drag twin roll caster  

Microsoft Academic Search

A downward melt drag twin roll caster was devised as a base caster for a composite strip caster. A clad strip and a wire-inserted strip can be cast using the downward melt drag twin roll caster. The downward melt drag twin roll caster is one of the horizontal types twin roll caster. In the downward melt drag twin roll caster,

T. Haga; K. Takahashi

2004-01-01

232

Partitioning coefficients between olivine and silicate melts  

Microsoft Academic Search

Variation of Nernst partition coefficients (D) between olivine and silicate melts cannot be neglected when modeling partial melting and fractional crystallization. Published natural and experimental olivine\\/liquidD data were examined for covariation with pressure, temperature, olivine forsterite content, and melt SiO2, H2O, MgO and MgO\\/MgO+FeOtotal. Values of olivine\\/liquidD generally increase with decreasing temperature and melt MgO content, and with increasing melt

J. H. Bédard

2005-01-01

233

How does the mantle melt?How does the mantle melt? 1) Increase the temperature  

E-print Network

;2) Lower the pressure ­ Adiabatic rise of mantle with no conductive heat loss ­ Decompression melting could isothermal decompression How does the mantle melt?How does the mantle melt? #12;Why does the mantle melt? ...because of upwelling and isothermal decompression of the melt #12;Magma Formation · Two major mechanisms

Siebel, Wolfgang

234

Climate change and forest fires synergistically drive widespread melt events of the Greenland Ice Sheet.  

PubMed

In July 2012, over 97% of the Greenland Ice Sheet experienced surface melt, the first widespread melt during the era of satellite remote sensing. Analysis of six Greenland shallow firn cores from the dry snow region confirms that the most recent prior widespread melt occurred in 1889. A firn core from the center of the ice sheet demonstrated that exceptionally warm temperatures combined with black carbon sediments from Northern Hemisphere forest fires reduced albedo below a critical threshold in the dry snow region, and caused the melting events in both 1889 and 2012. We use these data to project the frequency of widespread melt into the year 2100. Since Arctic temperatures and the frequency of forest fires are both expected to rise with climate change, our results suggest that widespread melt events on the Greenland Ice Sheet may begin to occur almost annually by the end of century. These events are likely to alter the surface mass balance of the ice sheet, leaving the surface susceptible to further melting. PMID:24843158

Keegan, Kaitlin M; Albert, Mary R; McConnell, Joseph R; Baker, Ian

2014-06-01

235

Fundamentals of Melt-Water Interfacial Transport Phenomena: Improved Understanding for Innovative Safety Technologies in ALWRs  

SciTech Connect

The interaction and mixing of high-temperature melt and water is the important technical issue in the safety assessment of water-cooled reactors to achieve ultimate core coolability. For specific advanced light water reactor (ALWR) designs, deliberate mixing of the core-melt and water is being considered as a mitigative measure, to assure ex-vessel core coolability. The goal of this work is to provide the fundamental understanding needed for melt-water interfacial transport phenomena, thus enabling the development of innovative safety technologies for advanced LWRs that will assure ex-vessel core coolability. The work considers the ex-vessel coolability phenomena in two stages. The first stage is the melt quenching process and is being addressed by Argonne National Lab and University of Wisconsin in modified test facilities. Given a quenched melt in the form of solidified debris, the second stage is to characterize the long-term debris cooling process and is being addressed by Korean Maritime University in via test and analyses. We then address the appropriate scaling and design methodologies for reactor applications.

M. Anderson; M. Corradini; K.Y. Bank; R. Bonazza; D. Cho

2005-04-26

236

Impact melt generation and transport  

NASA Technical Reports Server (NTRS)

The results from the first two calculations in a series of continuum mechanics computer code calculations, investigating the effects of variations in impactor mass and velocity on the generation and transport of impact melt, are reported. In the present calculations, the impactor is modeled as a spherical iron projectile with a mass of one trillion grams, and the target as a gabbroic anorthosite (GA) half-space, where the cases calculated have impact velocities of 5 and 15.8 km/sec. Early-time ejection velocities are 1-2 km/sec in both cases. The first calculation results in 0.07 projectile masses of GA being partly or completely melted, with all the melted GA being ejected from the crater, and a maximum impact range for the ejected melted material of 30 km. The second calculation yields 10.4 projectile masses of melted GA, 50% of which is ejected from the crater to ranges of up to about 130 km. Peak shock pressure attenuation with depth is reported for both cases, and transient cavity dynamics are described and compared to that for surface and near-surface explosions.

Orphal, D. L.; Borden, W. F.; Larson, S. A.; Schultz, P. H.

1980-01-01

237

Explosive volcanism and the compositions of cores of differentiated asteroids  

NASA Technical Reports Server (NTRS)

Eleven iron meteorite groups show correlations between Ni and siderophile trace elements that are predictable by distribution coefficients between liquid and solid metal in fractionally crystallizing metal magmas. These meteorites are interpreted to be fragments of the fractionally crystallized cores of eleven differentiated asteroids. Many of these groups crystallized from S-depleted magmas which we propose resulted from removal of the first partial melt (the Fe,Ni-FeS cotectic melt) by explosive pyroclastic volcanism of the type envisaged by Wilson and Keil (1991). We show that these dense, negatively buoyant melts can be driven to asteroidal surfaces due to the presence of excess pressure in the melt and the presence of buoyant bubbles of gas which decrease the density of the melt. We also show that, in typical asteroidal materials, veins will form which grow into dikes and serve as pathways for migration of melt and gas to asteroidal surfaces. Since cotectic Fe, Ni-FeS melt consists of about 85 wt pct FeS and 15 wt pct Fe, Ni, removal of small volumes of eutectic melts results in major loss of S but only minor loss of Fe,Ni, thus leaving sufficient Fe,Ni to form sizeable asteroidal cores.

Keil, Klaus; Wilson, Lionel

1993-01-01

238

Explosive volcanism and the compositions of cores of differentiated asteroids  

NASA Astrophysics Data System (ADS)

Eleven iron meteorite groups show correlations between Ni and siderophile trace elements that are predictable by distribution coefficients between liquid and solid metal in fractionally crystallizing metal magmas. These meteorites are interpreted to be fragments of the fractionally crystallized cores of eleven differentiated asteroids. Many of these groups crystallized from S-depleted magmas which we propose resulted from removal of the first partial melt (the Fe,Ni-FeS cotectic melt) by explosive pyroclastic volcanism of the type envisaged by Wilson and Keil (1991). We show that these dense, negatively buoyant melts can be driven to asteroidal surfaces due to the presence of excess pressure in the melt and the presence of buoyant bubbles of gas which decrease the density of the melt. We also show that, in typical asteroidal materials, veins will form which grow into dikes and serve as pathways for migration of melt and gas to asteroidal surfaces. Since cotectic Fe, Ni-FeS melt consists of about 85 wt pct FeS and 15 wt pct Fe, Ni, removal of small volumes of eutectic melts results in major loss of S but only minor loss of Fe,Ni, thus leaving sufficient Fe,Ni to form sizeable asteroidal cores.

Keil, K.; Wilson, L.

1993-05-01

239

Thermal convection in Earth's inner core with phase change at its boundary  

NASA Astrophysics Data System (ADS)

Inner core translation, with solidification on one hemisphere and melting on the other, provides a promising basis for understanding the hemispherical dichotomy of the inner core, as well as the anomalous stable layer observed at the base of the outer core-the so-called F-layer-which might be sustained by continuous melting of inner core material. In this paper, we study in details the dynamics of inner core thermal convection when dynamically induced melting and freezing of the inner core boundary (ICB) are taken into account. If the inner core is unstably stratified, linear stability analysis and numerical simulations consistently show that the translation mode dominates only if the viscosity ? is large enough, with a critical viscosity value, of order ˜3 × 1018 Pa s, depending on the ability of outer core convection to supply or remove the latent heat of melting or solidification. If ? is smaller, the dynamic effect of melting and freezing is small. Convection takes a more classical form, with a one-cell axisymmetric mode at the onset and chaotic plume convection at large Rayleigh number. ? being poorly known, either mode seems equally possible. We derive analytical expressions for the rates of translation and melting for the translation mode, and a scaling theory for high Rayleigh number plume convection. Coupling our dynamic models with a model of inner core thermal evolution, we predict the convection mode and melting rate as functions of inner core age, thermal conductivity, and viscosity. If the inner core is indeed in the translation regime, the predicted melting rate is high enough, according to Alboussière et al.'s experiments, to allow the formation of a stratified layer above the ICB. In the plume convection regime, the melting rate, although smaller than in the translation regime, can still be significant if ? is not too small. Thermal convection requires that a superadiabatic temperature profile is maintained in the inner core, which depends on a competition between extraction of the inner core internal heat by conduction and cooling at the ICB. Inner core thermal convection appears very likely with the low thermal conductivity value proposed by Stacey & Loper, but nearly impossible with the much higher thermal conductivity recently put forward by Sha & Cohen, de Koker et al. and Pozzo et al. We argue however that the formation of an iron-rich layer above the ICB may have a positive feedback on inner core convection: it implies that the inner core crystallized from an increasingly iron-rich liquid, resulting in an unstable compositional stratification which could drive inner core convection, perhaps even if the inner core is subadiabatic.

Deguen, Renaud; Alboussière, Thierry; Cardin, Philippe

2013-09-01

240

Accident progression event tree analysis for postulated severe accidents at N Reactor  

SciTech Connect

A Level II/III probabilistic risk assessment (PRA) has been performed for N Reactor, a Department of Energy (DOE) production reactor located on the Hanford reservation in Washington. The accident progression analysis documented in this report determines how core damage accidents identified in the Level I PRA progress from fuel damage to confinement response and potential releases the environment. The objectives of the study are to generate accident progression data for the Level II/III PRA source term model and to identify changes that could improve plant response under accident conditions. The scope of the analysis is comprehensive, excluding only sabotage and operator errors of commission. State-of-the-art methodology is employed based largely on the methods developed by Sandia for the US Nuclear Regulatory Commission in support of the NUREG-1150 study. The accident progression model allows complex interactions and dependencies between systems to be explicitly considered. Latin Hypecube sampling was used to assess the phenomenological and systemic uncertainties associated with the primary and confinement system responses to the core damage accident. The results of the analysis show that the N Reactor confinement concept provides significant radiological protection for most of the accident progression pathways studied.

Wyss, G.D.; Camp, A.L.; Miller, L.A.; Dingman, S.E.; Kunsman, D.M. (Sandia National Labs., Albuquerque, NM (USA)); Medford, G.T. (Science Applications International Corp., Albuquerque, NM (USA))

1990-06-01

241

Challenges in Melt Furnace Tests  

NASA Astrophysics Data System (ADS)

Measurement is a critical part of running a cast house. Key performance indicators such as energy intensity, production (or melt rate), downtime (or OEE), and melt loss must all be understood and monitored on a weekly or monthly basis. Continuous process variables such as bath temperature, flue temperature, and furnace pressure should be used to control the furnace systems along with storing the values in databases for later analysis. While using measurement to track furnace performance over time is important, there is also a time and place for short-term tests.

Belt, Cynthia

2014-09-01

242

Oxygen and silicon partitioning between molten iron and silicate melts  

NASA Astrophysics Data System (ADS)

The Earth’s core is mainly composed of a Fe-Ni alloy. The core density deficit compared to the density of pure iron requires the presence of light elements in addition to Fe and Ni. Si and O are among the likely candidates. Previous experimental studies have focused on the system Fe-(Mg, Fe)O to interpret the behavior of oxygen in iron melts, (Mg,Fe)O being used as a proxy for the silicate phase. In this study, we investigated directly the partitioning of oxygen and silicon between molten iron and silicate melts. We used 2 starting materials, prepared by mixing Fe and FeO, MgO and SiO2 in different proportions. Experiments were performed in MgO capsules at 2, 7, 14, and 21 GPa at temperatures of 2273, 2573, and 2873 K, using piston cylinder and multi-anvil presses. Recovered samples were analyzed with an electron microprobe. The partition coefficients of oxygen and silicon between metal and silicate were determined as a function of pressure, temperature and oxygen fugacity. The measured data are used with literature data to parameterize thermodynamically the partitioning of oxygen and silicon. The derived relationships reveal significant influence of oxygen fugacity on the partitioning of oxygen and silicon. Silicon partitioning depends more strongly on pressure than temperature, and the inverse is observed for oxygen. if the observed trends are valid at higher pressures, considering continuous core segregation under progressively oxidizing conditions as recently proposed, the core would contain about 8 wt% Si and less than 0.5 wt% O. In this case, Si would be the main contributor to the light element budget in the core. In comparison, for a single-stage scenario at oxygen fugacity of IW-2 and equilibration pressure of 40 GPa, the core would only contain about 2 wt% Si and 1 wt% O.

Ricolleau, A.; Fei, Y.; Siebert, J.; Corgne, A.; Badro, J.

2010-12-01

243

A Wave Interpretation of the Compton Effect As a Further Demonstration of the Postulates of de Broglie  

E-print Network

The Compton effect is commonly cited as a demonstration of the particle feature of light, while the wave nature of matter has been proposed by de Broglie and demonstrated by Davisson and Germer with the Bragg diffraction of electron beams. In this investigation, we present an entirely different interpretation of the Compton effect based on the postulates of de Broglie and on an interaction between electromagnetic and matter waves. The speeds of interacting electrons in the Compton scattering are quite fast and its mechanism relies heavily on the mass variation. Thus, based on this wave interpretation, the Compton effect can be viewed as a further demonstration of the postulates of de Broglie for high-speed particles. In addition to the scattered wave, a direct radiation depending on the mass variation is predicted, which provides a means to test the wave interpretation.

Ching-Chuan Su

2006-01-02

244

Ferrocyanide Safety Program: Analysis of postulated energetic reactions and resultant aerosol generation in Hanford Site Waste Tanks  

SciTech Connect

This report reviews work done to estimate the possible consequences of postulated energetic reactions in ferrocyanide waste stored in underground tanks at the Hanford Site. The issue of explosive reactions was raised in the 1987 Environmental Impact Statement (EIS), where a detonation-like explosion was postulated for the purpose of defining an upper bound on dose consequences for various disposal options. A review of the explosion scenario by the General Accounting Office (GAO) indicated that the aerosol generation and consequent radioactive doses projected for the explosion postulated in the EIS were understated by one to two orders of magnitude. The US DOE has sponsored an extensive study of the hazard posed by uncontrolled exothermic reactions in ferrocyanide waste, and results obtained during the past three years have allowed this hazard to be more realistically assessed. The objective of this report is to summarize the improved knowledge base that now indicates that explosive or vigorous chemical reactions are not credible in the ferrocyanide waste stored in underground tanks. This improved understanding supports the decision not to proceed with further analyses or predictions of the consequences of such an event or with aerosol tests in support of such predictions. 53 refs., 2 tabs.

Postma, A.K. [G and P Consulting, Inc., Dallas, OR (United States); Dickinson, D.R. [Westinghouse Hanford Co., Richland, WA (United States)

1995-09-01

245

Plama Torches Melt the Rock  

USGS Multimedia Gallery

Plasma torches at Zybek Advanced Products blaze at over 37,000 degrees Fahrenheit, melting the rock mixture. __________ The USGS has created man-made moon dirt, or regolith, to help NASA prepare for upcoming moon explorations. Four tons of the simulant is expected to be made by this summer of 2009...

246

Why does salt melt ice?  

NSDL National Science Digital Library

This tutorial on the chemical interaction between salt and ice explains how molecules on the surface of the ice escape into the water (melting), and how molecules of water are captured on the surface of the ice (freezing). It was created by the Chemistry Department at Frostburg State University (no, really).

Fred Senese

247

Redox viscometry of ferropicrite melt  

NASA Astrophysics Data System (ADS)

The rheology governs the dynamics of magmas at all scales (i.e. partial melting, magmatic chamber emplacement, lava flow behavior). It is also a fundamental constraint on volcanic morphology and landforms. Most terrestrial volcanic flows have moderate iron contents up to 10 wt% but some basalts show contain up to 16 wt%. These ferropicrites range from the Archean to recent, typically forming thin isolated flows near the base of thick lava piles in large igneous provinces, are not well understood. Although ferropicrites are rare on Earth's surface they are believed to be abundant on Mars. Analyses of Martian rocks (from remote sensing data, in situ measurements and meteorite analyses) display up to 20 wt% FeO. Studying these compositions will help to constrain the physical nature and evolution of the volcanism on Mars. The influence of iron on the structure and properties of magmatic melts, remains controversial. Simple system investigations indicate an as yet insufficiently parameterized influence of the oxidation state of iron on the rheology and other properties of silicate melts. The dependence of shear viscosity on the oxidation state of ferrosilicate melts has been measured using the concentric cylinder method and a gas mixing furnace. Previously, two different simple Fe-bearing systems have been studied: (i) anorthite-diopside eutectic composition (AnDi) with variable amount of Fe (up to 20 wt%) as a basalt analog and (ii) sodium disilicate (NS2) with up to 30 wt % Fe. Two natural compositions have been previously investigated, a phonolite and a pantellerite. Here, the compositional range has been extended to the more complex ferropicrite composition using the Adirondack class rock, a typical martian basalt (with low Al content and Fe up to 18,7 wt%). The experimental procedure involves a continuous measurement of viscosity at constant temperature during stepwise reduction state. The melt is reduced by flowing CO2 and then successively reducing mixtures of CO2-CO. The composition and oxidation state of the melt is monitored by obtaining a melt sample after each redox equilibrium step. The melts are sampled by dipping an alumina rod into the sample and drawing out a drop of liquid, which is then plunged into water for quenching. The resulting glasses are analyzed by electron microprobe, and the volumetric potassium dichromate titration is employed to determine FeO content. So far we observed a very low viscosity for high iron content samples and a decrease of the viscosity with increasing Fe content. Moreover, the viscosity of all melts investigated to date decreases with melt reduction. The viscosity decrease is, in general, a nonlinear function of oxidation state expressed as Fe2+/Fetot and can be fitted using logarithmic equation. The range of viscosity is compared to previous experimental studies and will help to understand morphological observations.

Oryaëlle Chevrel, Magdalena; Potuzak, Marcel; Dingwell, Donald B.; Hess, Kai-Uwe

2010-05-01

248

Ethics CORE  

NSDL National Science Digital Library

The Ethics CORE Digital Library, funded by the National Science Foundation, "brings together information on best practices in research, ethics instruction and responding to ethical problems that arise in research and professional life." It's a remarkable site where visitors can make their way through ethics resources for dozens of different professions and activities. The Resources by Discipline area is a great place to start. Here you will find materials related to the biological sciences, business, computer & information science, along with 14 additional disciplines. The Current News area is a great place to learn about the latest updates from the field. Of note, these pieces can easily be used in the classroom or shared with colleagues. The dynamism of the site can be found at the Interact with Ethics CORE area. Active learning exercises can be found here, along with instructional materials and visitors' own lessons learned.

249

Partitioning coefficients between olivine and silicate melts  

Microsoft Academic Search

Variation of Nernst partition coefficients (D) between olivine and silicate melts cannot be neglected when modeling partial melting and fractional crystallization. Published natural and experimental olivine\\/liquidD data were examined for covariation with pressure, temperature, olivine forsterite content, and melt SiO2, H2O, MgO and MgO\\/MgO + FeOtotal. Values of olivine\\/liquidD generally increase with decreasing temperature and melt MgO content, and with

J. H. Bédard

2005-01-01

250

The nature of the earth's core  

NASA Technical Reports Server (NTRS)

The properties of the earth's core are overviewed with emphasis on seismologically determined regions and pressures and seismologically measured density, elastic wave velocities, and gravitational acceleration. Attention is given to solid-state convection of the inner core, and it is noted that though seismological results do not conclusively prove that the inner core is convective, the occurrence and magnitude of seismic anisotropy are explained by the effects of solid-state convection. Igneous petrology and geochemistry of the inner core, a layer at the base of the mantle and contact metasomatism at the core-mantle boundary, and evolution of the core-mantle system are discussed. It is pointed out that high-pressure melting experiments indicate that the temperature of the core is ranging from 4500 to 6500 K, and a major implication of such high temperature is that the tectonics and convection of the mantle, as well as the resulting geological processes observed at the surface, are powered by heat from the core. As a result of the high temperatures, along with the compositional contrast between silicates and iron alloy, the core-mantle boundary is considered to be most chemically active region of the earth.

Jeanloz, Raymond

1990-01-01

251

How Does Melting Ice Affect Sea Level?  

NSDL National Science Digital Library

In this activity, students investigate how sea levels might rise when ice sheets and ice caps melt by constructing a pair of models and seeing the effects of ice melt in two different situations. Students should use their markers to predict the increase of water in each box before the ice melts.

LuAnn Dahlman

252

Frictional melting of peridotite and seismic slip  

Microsoft Academic Search

The evolution of the frictional strength along a fault at seismic slip rates (about 1 m\\/s) is a key factor controlling earthquake mechanics. At mantle depths, friction-induced melting and melt lubrication may influence earthquake slip and seismological data. We report on laboratory experiments designed to investigate dynamic fault strength and frictional melting processes in mantle rocks. We performed 20 experiments

P. Del Gaudio; G. Di Toro; R. Han; T. Hirose; S. Nielsen; T. Shimamoto; A. Cavallo

2009-01-01

253

Melting Point, Boiling Point, and Symmetry  

Microsoft Academic Search

The relationship between the melting point of a compound and its chemical structure remains poorly understood. The melting point of a compound can be related to certain of its other physical chemical properties. The boiling point of a compound can be determined from additive constitutive properties, but the melting point can be estimated only with the aid of nonadditive constitutive

Robert Abramowitz; Samuel H. Yalkowsky

1990-01-01

254

Certain petrological features of impact melts  

Microsoft Academic Search

A cluster analysis of impactites and target rocks of the Zhamanshin and Manicouagan astroblemes was carried out. Two types of impact melts were found to exist: (1) highly homogeneous melts resulting from intense mixing during motion in the crater cavity and (2) heterogeneous melts which consist mainly of a single rock and result from ejections of matter that did not

V. I. Fel'Dman; V. M. Riakhovskii

1989-01-01

255

Proton spin dynamics in polymer melts: new perspectives for experimental investigations of polymer dynamics  

E-print Network

Significant progress was made in recent years in the understanding of the proton spin kinetics in polymer melts. Generally, the proton spin kinetics is determined by intramolecular and intermolecular magnetic dipole-dipole contributions of proton spins. During many decades it was postulated that the main contribution is a result of intramolecular magnetic dipole-dipole interactions of protons belonging to the same polymer segment. It appears that this postulate is far from reality. The relative weights of intra- and intermolecular contributions are time dependent and sensitive to details of polymer chain dynamics. It is shown that for isotropic models of polymer dynamics the influence of the intermolecular magnetic dipole-dipole interactions increases faster with increasing evolution time (i.e. decreasing frequency) than the corresponding influence of the intramolecular counterpart. On the other hand, an inverted situation is predicted by the tube-reptation model: here the influence of the intramolecular magnetic dipole-dipole interactions increases faster with time than the contribution from intermolecular interactions. The intermolecular contribution in the proton relaxation of polymer melts can experimentally be isolated using the isotope dilution technique and this opens a new perspective for experimental investigations of polymer dynamics by proton NMR.

N. Fatkullin; S. Stapf; M. Hofmann; R. Meierc; E. A. Roessler

2014-05-25

256

Proton spin dynamics in polymer melts: New perspectives for experimental investigations of polymer dynamics  

NASA Astrophysics Data System (ADS)

Significant progress was made in recent years in the understanding of the proton spin kinetics in polymer melts. Generally, the proton spin kinetics is determined by intramolecular and intermolecular magnetic dipole-dipole contributions of proton spins. During many decades it was postulated that the main contribution is a result of intramolecular magnetic dipole-dipole interactions of protons belonging to the same polymer segment. It appears that this postulate is far from reality. The relative weights of intra- and intermolecular contributions are time dependent and sensitive to details of polymer chain dynamics. It is shown that for isotropic models of polymer dynamics the influence of the intermolecular magnetic dipole-dipole interactions increases faster with increasing evolution time (i.e. decreasing frequency) than the corresponding influence of the intramolecular counterpart. On the other hand, an inverted situation is predicted by the tube-reptation model: here the influence of the intramolecular magnetic dipole-dipole interactions increases faster with time than the contribution from intermolecular interactions. The intermolecular contribution in the proton relaxation of polymer melts can experimentally be isolated using the isotope dilution technique and this opens a new perspective for experimental investigations of polymer dynamics by proton NMR.

Fatkullin, N.; Stapf, S.; Hofmann, M.; Meier, R.; Rössler, E. A.

2015-01-01

257

Optimization of the Materials Composition in External Core Catchers for Nuclear Reactors  

Microsoft Academic Search

Existing schemes of core melt retention apparatus for water-cooled water-moderated nuclear reactors are analyzed. In-shaft variants of melt catchers at nuclear power plants with VVÉR-1000 reactors are proposed. It is shown that TiO2- and Nd2O3-based materials increase the operational reliability of the retention apparatus by modifying the processes occurring in the melt and by preserving the integrity of refractory coatings

V. N. Mineev; F. A. Akopov; A. S. Vlasov; Yu. A. Zeigarnik; O. M. Traktuev

2002-01-01

258

Viscosity of Iron-rich Martian Basaltic Melts  

NASA Astrophysics Data System (ADS)

Differences in the chemical compositions of planetary mantles can contribute to the large diversity of volcanic melts. In particular, differences in oxidation state during core-mantle differentiation result in significant variations of iron oxide concentration in the mantle, the most oxidized bodies having the most iron-rich mantles (e.g., Mars). The viscosity of silicate liquids extracted from these mantles is the most important parameter controlling magma ascent and emplacement during eruption. To date, empirical models for prediction of the effect of temperature and composition on the viscosity of silicate melts are based on experiments spanning the range of terrestrial compositions of volcanic rocks. This study extends the capability of those models to predict the viscosity of melts with iron-rich Martian compositions (up to 20 wt.% FeO). The investigated compositions comprise the in-situ analysed Adirondack, Backstay and Irvine rocks (Gusev crater, Mars) and two compositions representing respectively the Amazonian volcanism and Hesperian volcanism (Baratoux et al., 2011). The dry viscosity at high temperature was determined via the concentric cylinder method in air and under reduced conditions and the low temperature viscosities were estimated from the glass transition temperature determined with a differential scanning calorimeter. The investigation of iron-rich Martian melt viscosity is experimentally challenging because of liquid-liquid immiscibility and rapid crystallisation during quenching. The viscosity values at high temperatures are as low as for lunar basalts and under-saturated terrestrial rocks and are affected by the iron redox state. Viscosities of supercooled melts show significant discrepancies to existing models possibly resulting from the effect of iron-oxidation state on glass transition temperature.

Chevrel, M. O.; Baratoux, D.; Hess, K.; Dingwell, D. B.

2012-12-01

259

The influence of melting and melt drainage on crustal rheology during orogenesis  

NASA Astrophysics Data System (ADS)

Partial melting significantly weakens crustal rocks by introducing a low-viscosity liquid phase. However, near-concomitant melt drainage can remove this weak phase, potentially reversing the rheological effects such that the strength of a specific lithology depends on when the prograde pressure-temperature path intersects a melting reaction, how much melt is produced, and how long this melt is retained before it is lost. Phase equilibria and mixed rheology modeling of typical metapelite and metagreywacke compositions indicate that these rocks undergo continuous but pulsed melt production during prograde metamorphism. Depending on whether melt removal is continuous or episodic, and assuming geological strain rates, the lithologies can retain a very low strength less than 1 MPa or transiently strengthen to ˜5 MPa following melt loss. Lithologies undergoing episodic melt loss can therefore cycle between being relatively weak and relatively strong components within a composite crustal section. Melt production, retention, and weakening in the middle to lower crust as a whole is more sustained during heating and melt production, consistent with geodynamic inferences of weak, melt-bearing lower crust. However, the long-term consequence of melting and melt loss is a 50-400% increase in the strength of residual lithologies. The strengthening is more pronounced in metapelite than metagreywacke and is achieved through a combination of dehydration and the removal of the weak mica framework coupled to increased proportions of strong feldspars and garnet. Despite prolonged weakness, melting and melt loss therefore ultimately result in a dry and elastic lower crust.

Diener, Johann F. A.; Fagereng, Åke

2014-08-01

260

Planetary science. Shock compression of stishovite and melting of silica at planetary interior conditions.  

PubMed

Deep inside planets, extreme density, pressure, and temperature strongly modify the properties of the constituent materials. In particular, how much heat solids can sustain before melting under pressure is key to determining a planet's internal structure and evolution. We report laser-driven shock experiments on fused silica, ?-quartz, and stishovite yielding equation-of-state and electronic conductivity data at unprecedented conditions and showing that the melting temperature of SiO2 rises to 8300 K at a pressure of 500 gigapascals, comparable to the core-mantle boundary conditions for a 5-Earth mass super-Earth. We show that mantle silicates and core metal have comparable melting temperatures above 500 to 700 gigapascals, which could favor long-lived magma oceans for large terrestrial planets with implications for planetary magnetic-field generation in silicate magma layers deep inside such planets. PMID:25613887

Millot, M; Dubrovinskaia, N; ?ernok, A; Blaha, S; Dubrovinsky, L; Braun, D G; Celliers, P M; Collins, G W; Eggert, J H; Jeanloz, R

2015-01-23

261

Shock compression of stishovite and melting of silica at planetary interior conditions  

NASA Astrophysics Data System (ADS)

Deep inside planets, extreme density, pressure, and temperature strongly modify the properties of the constituent materials. In particular, how much heat solids can sustain before melting under pressure is key to determining a planet’s internal structure and evolution. We report laser-driven shock experiments on fused silica, ?-quartz, and stishovite yielding equation-of-state and electronic conductivity data at unprecedented conditions and showing that the melting temperature of SiO2 rises to 8300 K at a pressure of 500 gigapascals, comparable to the core-mantle boundary conditions for a 5–Earth mass super-Earth. We show that mantle silicates and core metal have comparable melting temperatures above 500 to 700 gigapascals, which could favor long-lived magma oceans for large terrestrial planets with implications for planetary magnetic-field generation in silicate magma layers deep inside such planets.

Millot, M.; Dubrovinskaia, N.; ?ernok, A.; Blaha, S.; Dubrovinsky, L.; Braun, D. G.; Celliers, P. M.; Collins, G. W.; Eggert, J. H.; Jeanloz, R.

2015-01-01

262

Melting curve of molecular hydrogen  

NASA Astrophysics Data System (ADS)

More than 70 years ago Wigner and Huntington predicted that at sufficiently high pressures hydrogen will become an atomic metallic solid. Metallic hydrogen has not yet been observed at pressures exceeding 3 Mbar at low temperatures. Recent calculations predict a maximum in the melting line of hydrogen. Extrapolations to higher pressures suggest that metallic hydrogen may be a liquid at T=0 K with interesting quantum properties. Confining hydrogen at elevated temperatures is challenging as hydrogen tends to diffuse out of the cell. Combination of static pressure techniques with dynamic temperature variations can be used to suppress the diffusion of the sample out of the pressure cell. We have extended the melting line of hydrogen and observed the predicted peak and shall discuss this, the unusual properties of hydrogen, and it's various phases.

Deemyad, Shanti

2009-06-01

263

Dynamic crystallization of silicate melts  

NASA Technical Reports Server (NTRS)

Two types of furnaces with differing temperature range capabilities were used to provide variations in melt temperatures and cooling rates in a study of the effects of heterogeneous nucleation on crystallization. Materials of chondrule composition were used to further understanding of how the disequilibrium features displayed by minerals in rocks are formed. Results show that the textures of natural chondrules were duplicated. It is concluded that the melt history is dominant over cooling rate and composition in controlling texture. The importance of nuclei, which are most readily derived from preexisting crystalline material, support an origin for natural chondrules based on remelting of crystalline material. This would be compatible with a simple, uniform chondrule forming process having only slight variations in thermal histories resulting in the wide range of textures.

Russell, W. J.

1984-01-01

264

Thermoplastic/Melt-Processable Polyimides  

NASA Technical Reports Server (NTRS)

Several polyimides were prepared which show promise for aircraft composite applications. This was achieved through a systematic polymer synthesis program where the glass transition temperatures were greatly lowered when compared to the older polyimide systems. Several of the materials were shown to be hot-melt processable and are attractive matrix resin candidates especially in light of their high g(sub Ic) values. At least two of these polyimides are available for evaluation and others are on the research horizon.

St.clair, T. L.; Burks, H. D.

1984-01-01

265

Melting And Purification Of Niobium  

SciTech Connect

The aspects involved in the purification of niobium in Electron Beam Furnaces will be outlined and correlated with practical experience accumulated over 17 years of continuously producing high purity niobium metal and niobium-zirconium ingots at CBMM, meeting the needs for a wide range of uses. This paper also reports some comments regarding raw material requirements, the experience on cold hearth operation melting niobium and the production of large grains niobium ingots by CBMM with some comments of their main characteristics.

Salles Moura, Hernane R.; Moura, Lourenco de [CBMM - Companhia Brasileira de Metalurgia e Mineracao, Fazenda Corrego da Mata, P.O. BOX 8, 38.183.903 - Araxa, MG (Brazil)

2007-08-09

266

Melting of foaming batches: Nuclear waste glass  

SciTech Connect

A simple model is presented for the rate of melting of a batch blanket in an electric glassmelting furnace. The melting process is assumed to be jointly controlled by the heat transfer from the pool of molten glass and the batch-to-glass conversion kinetics. Factors affecting the melting rate in the conversion-controlled regime are discussed. Attention is paid to gas evolution from redox reactions in waste glass batches and component accumulation within the blanket. It is suggested that the high rate of the blanket-free melting in a mechanically agitated furnace is made possible by increasing the rate of melt surface renewal. 27 refs.

Hrma, P.

1990-10-01

267

Martian mantle primary melts - An experimental study of iron-rich garnet lherzolite minimum melt composition  

NASA Technical Reports Server (NTRS)

The minimum melt composition in equilibrium with an iron-rich garnet lherzolite assemblage is ascertained from a study of the liquidus relations of iron-rich basaltic compositions at 23 kb. The experimentally determined primary melt composition and its calculated sodium content reveal that Martian garnet lherzolite minimum melts are picritic alkali olivine basalts. Martian primary melts are found to be more picritic than terrestrial garnet lherzolite primary melts.

Bertka, Constance M.; Holloway, John R.

1988-01-01

268

Coeval Ar40\\/Ar39 ages of 65.0 million years ago from Chicxulub crater melt rock and Cretaceous-Tertiary boundary tektites  

Microsoft Academic Search

Ar-40\\/Ar-39 dating of drill-core samples of a glassy melt rock recovered from beneath a massive impact breccia contained with the 180-kilometer subsurface Chicxulub crater yields well-behaved incremental heating spectra with a mean plateau age of 64.98 +\\/- 0.05 million years ago (Ma). The glassy melt rock of andesitic composition was obtained from core 9 (1390 to 1393 meters) in the

Carl C. Swisher III; Jose M. Grajales-Nishimura; Alessandro Montanari; Stanley V. Margolis; Philippe Claeys; Walter Alvarez; Paul Renne; Esteban Cedillo-Pardo; Florentin J.-M. R. Maurrasse; Garniss H. Curtis; J. Smit; M. O. McWilliams

1992-01-01

269

Melting by temperature-modulated calorimetry  

SciTech Connect

Well-crystallized macromolecules melt irreversibly due to the need of molecular nucleation, while small molecules melt reversibly as long as crystal nuclei are present to assist crystallization. Furthermore, imperfect crystals of low-molar-mass polymers may have a sufficiently small region of metastability between crystallization and melting to show a reversing heat-flow component due to melting of poor crystals followed by crystallization of imperfect crystals which have insufficient time to perfect before the modulation switches to heating and melts the imperfect crystals. Many metals, in turn. melt sharply and reversibly as long as nuclei remain after melting for subsequent crystallization during the cooling cycle. Their analysis is complicated, however, due to thermal conductivity limitations of the calorimeters. Polymers of sufficiently high molar mass, finally, show a small amount of reversible. local melting that may be linked to partial melting of individual molecules. Experiments by temperature-modulated calorimetry and model calculations are presented. The samples measured included poly(ethylene terephthalate)s, poly(ethylene oxide)s, and indium. Two unsolved problems that arose from this research involve the origin of a high, seemingly stable, reversible heat capacity of polymers in the melting region, and a smoothing of melting and crystallization into a close-to-elliptical Lissajous figure in a heat-flow versus sample-temperature plot.

Wunderlich, B.; Okazaki, Iwao; Ishikiriyama, Kazuhiko; Boller, A. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry]|[Oak Ridge National Lab., TN (United States)

1997-09-01

270

Who Done It? Or what's that brown fuzzy stuff on my plum?: Koch's Postulates for Proof of Pathogenicity  

NSDL National Science Digital Library

In this lab, learners explore Koch's Postulates, the critical step used to prove that a particular microbe is the cause of a specific disease in a host organism (plant or animal). This is accomplished by examining the brown fuzzy stuff (a fungal pathogen) growing on a plum and experimentally showing, step by step, whether or not it is the cause of the observed disease. This lesson guide includes background information, instructions for leading a simplified (less time intensive) demonstration of the Germ Theory, study questions and answers, suggestions for additional experiments, and supplemental information and references. Adult supervision recommended.

Claudia A. Jasalavich

2011-01-01

271

Garnet melt viscosity, surface tension and drainage  

NASA Technical Reports Server (NTRS)

Good surface morphology and layer uniformity of LPE-grown Bi YIG films are favored by fast melt removal after growth. Three flux modifying oxides: MoO3, V2O3, and WO3 are compared with respect to their effect on viscosity, surface tension and melt drainage. All three oxides increased the viscosities of Bi-garnet melts, but the viscosities and drainage times of V2O3 and MoO3 modified melts were smaller than those of WO3 modified melts. The liquid-gas surface tension was found to be temperature independent. The drainage process was strongly temperature dependent, 40 to 60 kcal/mol, whereas the viscosities of melts had activation energies of 11 to 16 kcal/mol. Contact angles of 16 + or - 2 deg were measured on frozen melt drops.

Luther, L. C.

1986-01-01

272

The behavior of ANGRA 2 nuclear power plant core for a small break LOCA simulated with RELAP5 code  

NASA Astrophysics Data System (ADS)

This work discusses the behavior of Angra 2 nuclear power plant core, for a postulate Loss of Coolant Accident (LOCA) in the primary circuit for Small Break Loss Of Coolant Accident (SBLOCA). A pipe break of the hot leg Emergency Core Cooling System (ECCS) was simulated with RELAP 5 code. The considered rupture area is 380 cm2, which represents 100% of the ECCS pipe flow area. Results showed that the cooling is enough to guarantee the integrity of the reactor core.

Sabundjian, Gaianê; Andrade, Delvonei A.; Belchior, Antonio, Jr.; da Silva Rocha, Marcelo; Conti, Thadeu N.; Torres, Walmir M.; Macedo, Luiz A.; Umbehaun, Pedro E.; Mesquita, Roberto N.; Masotti, Paulo H. F.; de Souza Lima, Ana Cecília

2013-05-01

273

Fe-based nanocrystalline powder cores with ultra-low core loss  

NASA Astrophysics Data System (ADS)

Melt-spun amorphous Fe73.5Cu1Nb3Si15.5B7 alloy strip was crushed to make flake-shaped fine powders. The passivated powders by phosphoric acid were mixed with organic and inorganic binder, followed by cold compaction to form toroid-shaped bonded powder-metallurgical magnets. The powder cores were heat-treated to crystallize the amorphous structure and to control the nano-grain structure. Well-coated phosphate-oxide insulation layer on the powder surface decreased the the core loss with the insulation of each powder. FeCuNbSiB nanocrystalline alloy powder core prepared from the powder having phosphate-oxide layer exhibits a stable permeability up to high frequency range over 2 MHz. Especially, the core loss could be reduced remarkably. At the other hand, the softened inorganic binder in the annealing process could effectively improve the intensity of powder cores.

Wang, Xiangyue; Lu, Zhichao; Lu, Caowei; Li, Deren

2013-12-01

274

Rheology of Earth's Inner Core  

NASA Astrophysics Data System (ADS)

Here I use mineral physics constraints to evaluate the viscosity and creep mechanisms of iron at the conditions of the inner core. At low to intermediate stresses and temperatures near the melting point solid materials may deform by any of three mechanisms: power law creep, diffusion creep and Harper-Dorn creep. Both power law and Harper-Dorn creep are dislocation processes, and the transition between the two occurs at a stress level on the order of the Peierls stress, with power law creep dominating at higher stresses. The transition stress is predicted to be ~3 MPa for hcp-Fe at inner core conditions, which is far higher than the stresses of ~102 to 103 Pa expected from magnetic or gravitational forces. Harper-Dorn creep dominates diffusion creep above a certain grain size, which is predicted to be ~200 microns for hcp-Fe. At the high temperatures and low stresses of the inner core the grain size is expected to be several orders of magnitude larger than the transition value. Harper-Dorn creep is therefore predicted to be the dominant deformation mechanism in the inner core. Harper-Dorn creep is accomplished by the motion of dislocations and can lead to strong lattice preferred orientation. The viscosity in this regime is Newtonian and is given by ? = (kT)/(ADb) where k is Boltzmann's constant, T is temperature, D is the self-diffusion coefficient, b is the Burgers vector and A is a dimensionless constant predicted to have a value of ~1.7 x 1011 for hcp-Fe. No diffusion data exist for hcp-Fe, but metals with similar structure all have nearly the same self-diffusion coefficient at the same homologous temperature. Assuming an inner core temperature of 5700 K and melting temperature for pure iron of 6200 K, the diffusivity is predicted to be ~4 × 10-13 m2 s-1 and the viscosity ~6 × 1013 Pa s. The corresponding strain rate for a shear stress of 100 Pa is ~2 × 10-12 s-1, implying that large strains are possible on timescales less than 100,000 years. It is therefore likely that the anisotropy in the inner core is the result of lattice preferred orientation developed during active or very recent deformation.

van Orman, J. A.

2004-05-01

275

Late-phase melt progression experiment: MP-2. Results and analysis  

SciTech Connect

In-pile experiments addressing late-phase processes in Light Water Reactors (LWRs) were performed in the Annular Core Research Reactor (ACRR) at Sandia National Laboratories. Melt Progression (MP) experiments were designed to provide information to develop and verify computer models for analysis of LWR core damage in severe accidents. Experiments examine the formation and motion of ceramic molten pools in disrupted reactor core regions. The MP-2 experiment assembly consisted of: (1) a rubble bed of enriched UO{sub 2} and ZrO{sub 2} simulating severely disrupted reactor core regions, (2) a ceramic/metallic crust representing blockage formed by early phase melting, relocation, and refreezing of core components, and (3) an intact rod stub region that remained in place below the blockage region. The test assembly was fission heated in the central cavity of the ACRR at an average rate of about 0.2 KA, reaching a peak molten pool temperature around 3400 K. Melting of the debris bed ceramic components was initiated near the center of the bed. The molten material relocated downward, refreezing to form a ceramic crust near the bottom of the rubble bed. As power levels were increased, the crust gradually remelted and reformed at progressively lower positions in the bed until late in the experiment when it penetrated into and attacked the ceramic/metallic blockage. The metallic components of the blockage region melted and relocated to the bottom of the intact rod stub region before the ceramic melt penetrated the blockage region from above. The ceramic pool penetrated halfway into the blockage region by the end of the experiment. Measurements of thermal response and material relocation are compared to the results of the computer simulations. Postexperiment examination of the assembly with the associated material interactions and metallurgy are also discussed in detail with the analyses and interpretation of results. 16 refs., 206 figs., 24 tabs.

Gasser, R.D.; Gauntt, R.O.; Bourcier, S.C. [and others

1997-05-01

276

A Monazite-bearing clast in Apollo 17 melt breccia  

NASA Technical Reports Server (NTRS)

A phosphate-rich clast in a pigeonite-plagioclase mineral assemblage occurs in Apollo 17 impact-melt breccia 76503,7025. The clast, measuring 0.9 x 0.4 mm in thin section, contains 3.3 percent (volume) apatite (Ca5P3O12(F,Cl)), 0.8 percent whitlockite (Ca16(Mg,Fe)2REE2P14O56), and trace monazite ((LREE)PO4). Major minerals include 26 percent pigeonite, En53-57FS34-35W08-13, and 69 percent plagioclase, An84-92Ab7-15Oro.6-1.1. Troilite, ilmenite, and other accessory minerals constitute less than 1 percent of the assemblage and Fe-metal occurs along fractures. Also present in the melt breccia as a separate clast is a fragment of felsite. Based on the association of these clasts and their assemblages, a parent lithology of alkali-anorthositic monzogabbro is postulated. Monazite occurs in the phosphate-bearing clast as two less than 10 micron grains intergrown with whitlockite. The concentration of combined REE oxides in monazite is 63.5 percent and the chondrite-normalized REE pattern is strongly enriched in LREE, similar to lunar monazite in 10047,68 and terrestrial monazite. Thorium concentration was not measured in monazite, but based on oxide analyses of approximately 100 percent (including interpolated values for REE not measured), substantial Th concentration is not indicated, similar to monazite in 10047,68. Measured monazite/whitlockite REE ratios are La: 11, Ce: 8, Sm: 3.6, Y: 0.9, and Yb: 0.5. Compositions of monazite and coexisting whitlockite and apatite are given.

Jolliff, Bradley L.

1993-01-01

277

Molecular dynamics simulation of Coulomb explosion, melting and shock wave creation in silicon after an ionization pulse  

SciTech Connect

Strong electronic stopping power of swift ions in a semiconducting or insulating substrate can lead to localized electron stripping. The subsequent repulsive interactions among charged target atoms can cause Coulomb explosion. Using molecular dynamics simulation, we simulate Coulomb explosion in silicon by introducing an ionization pulse lasting for different periods, and at different substrate temperatures. We find that the longer the pulse period, the larger the melting radius. The observation can be explained by a critical energy density model assuming that melting required thermal energy density is a constant value and the total thermal energy gained from Coulomb explosion is linearly proportional to the ionization period. Our studies also show that melting radius is larger at higher substrate temperatures. The temperature effect is explained due to a longer structural relaxation above the melting temperature at original ionization boundary due to lower heat dissipation rates. Furthermore, simulations show the formation of shock waves, created due to the compression from the melting core.

Li, Zhongyu; Shao, Lin, E-mail: lshao@tamu.edu [Fundamental Science on Nuclear Safety and Simulation Technology Laboratory, Harbin Engineering University, Harbin 150001 (China); Chen, Di [Department of Nuclear Engineering, Texas A and M University, College Station, Texas 77843 (United States); Wang, Jing [Department of Materials Science and Engineering, Texas A and M University, College Station, Texas 77843 (United States)

2014-04-14

278

Simulation studies on architecture dependence of unentangled polymer melts.  

PubMed

The dependences of the properties of linear, ring, star, and H-shaped polymer melts on architecture are investigated by nonequilibrium molecular dynamics simulations. We find that zero-shear viscosities ?0 for various architectures follow a universal relation, ?0=C??Rg0 (2)?, where C? is a constant and ?Rg0 (2)? the equilibrium mean-square radius of gyration, in the unentangled regime. This law is also found valid for asymmetrical polymers but invalid for polymers with a hard core, such as stars with many arms and short arm lengths. In the unentangled regime, from the point of view of polymer size, the relaxation times show weak dependences on architecture, but the architecture dependence of the diffusion coefficient is still apparent. Then, we examine unentangled melts of various architectures having the same size over a wide range of shear rates covering linear and nonlinear viscoelastic regimes and find that the rheological quantities, namely, viscosity, first and second normal stress differences, are independent of architecture. In contrast, the polymer deformation shows an apparent dependence on architecture in the nonlinear regime. These findings shall shed significant light on the nature of rheological behaviors of unentangled melts. PMID:25702027

Xu, Xiaolei; Chen, Jizhong; An, Lijia

2015-02-21

279

Simulation studies on architecture dependence of unentangled polymer melts  

NASA Astrophysics Data System (ADS)

The dependences of the properties of linear, ring, star, and H-shaped polymer melts on architecture are investigated by nonequilibrium molecular dynamics simulations. We find that zero-shear viscosities ?0 for various architectures follow a universal relation, ? 0 = C ? < Rg 0 2 > , where C? is a constant and < Rg 0 2 > the equilibrium mean-square radius of gyration, in the unentangled regime. This law is also found valid for asymmetrical polymers but invalid for polymers with a hard core, such as stars with many arms and short arm lengths. In the unentangled regime, from the point of view of polymer size, the relaxation times show weak dependences on architecture, but the architecture dependence of the diffusion coefficient is still apparent. Then, we examine unentangled melts of various architectures having the same size over a wide range of shear rates covering linear and nonlinear viscoelastic regimes and find that the rheological quantities, namely, viscosity, first and second normal stress differences, are independent of architecture. In contrast, the polymer deformation shows an apparent dependence on architecture in the nonlinear regime. These findings shall shed significant light on the nature of rheological behaviors of unentangled melts.

Xu, Xiaolei; Chen, Jizhong; An, Lijia

2015-02-01

280

Electrical Conductivity and Tomographic Imaging of Olivine-FeS Partial-Melts  

NASA Astrophysics Data System (ADS)

The presence, distribution, and composition of melt affect the physical properties of polycrystalline ultramafic rock and are important to our interpretation of the Earth's lower crust and upper mantle, and to our understanding of planetary core formation via liquid-metal segregation. A key issue in models of planetary core formation is the interconnectness of molten iron-sulfides in contact with silicates at high temperature and pressure. Olivine-FeS partial-melts are also considered to be possible explanations for anomalously high conductivity regions beneath mountain ranges such as the Pyrenees and Andes. The interconnectivity and tortuosity of the melt phase, in combination with the properties of the individual melt and crystal phases, have bearing on the extractability of the melt, and on the rheology, and electrical conductivity of the bulk material. We have begun an integrated study of the electrical conductivity-texture-permeability relationships of olivine-sulfide partial-melt samples. Olivine-sulfide partial-melts containing 0, 1, 3, 6, and 10% by weight non-wetting compositions (Fe64S36) and wetting compositions (Fe34S19Ni47+O2) in a San Carlos olivine matrix (Fo91) have been synthesized in a piston cylinder apparatus at 1250 C and 1 to 2 GPa. Electrical conductivity measurements of the partial-melt and the individual melt and crystalline phases have been performed in a 1-atmosphere gas-mixing furnace up to 1400 C. Additional measurements in solid medium-pressure apparatus (D-DIA, piston cylinder) have begun. Samples are characterized using X-ray microtomographic (XRCT) performed at the Advanced Light Source with spatial resolution approaching 2 microns. Determination of the 3-D structure and interconnectedness of the melt phase, combined with the electrical conductivity measurements have been used to estimate the permeability of the mixtures at various experimental conditions. Results indicate sulfur fugacity is an important parameter controlling the wettability and interconnectivity of the melt phase. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract W-7405-ENG-48 and supported specifically by Laboratory Directed Research and Development funding

Roberts, J.; Mei, S.; Ryerson, R.; Kinney, J.

2005-05-01

281

An idealized transient model for melt dispersal from reactor cavities during pressurized melt ejection accident scenarios  

SciTech Connect

The direct Containment Heating (DCH) calculations require that the transient rate at which the melt is ejected from the reactor cavity during hypothetical pressurized melt ejection accident scenarios be calculated. However, at present no models, that are able to predict the available melt dispersal data from small scale reactor cavity models, are available. In this report, a simple idealized model of the melt dispersal process within a reactor cavity during a pressurized melt ejection accident scenario is presented. The predictions from the model agree reasonably well with the integral data obtained from the melt dispersal experiments using a small scale model of the Surry reactor cavity. 17 refs., 15 figs.

Tutu, N.K.

1991-06-01

282

Modeling non-linear variations in melt productivity in mantle melt regimes  

NASA Astrophysics Data System (ADS)

Efforts to better understand the dynamic mantle processes that lead to mid-ocean ridge basalt (MORB) generation and the formation of new crust require robust constraints on factors that influence variations in the melting process. Here we apply existing and new numerical modeling methods to the complex problem of mantle melting to better understand the role of variations in mineral/melt partitioning behavior and melt productivity in the generation of melts. Through this work we can place new constraints on the MORB melting process. Using a one-dimensional continuous dynamic melting model code, as well as existing code for one-dimensional reactive porous flow melting provided by Spiegelman [2000, Geochem. Geophys. Geosys. v. 1, 10.1029/1999GC000030], we calculate time-dependent {^238}U-{^230}Th-{^226}Ra and {^235}U-{^231}Pa disequilibria resulting from melting both peridotitic and eclogitic mantle sources in a series of upwelling mantle columns, over a range of solid upwelling rates and maximum residual porosity values. We explicitly consider the effects of non-linear changes in mineral mode and melt fraction during melting for both porous flow and continuous dynamic melting. Preliminary results from continuous and incremental models suggest that previously observed effects of porous flow melting in two layer peridotitic models, namely the inability to preserve high ({^230}Th/{^238}U) activity ratios in a progressive melt column that enters the spinel peridotite melt regime, are enhanced by expected variations in melt productivity. This outcome demonstrates that two-dimensional approaches are necessary for the porous flow melt regime. This effect is less substantial for dynamic melts, but does still lead to difficulties generating sufficiently high ({^230}Th/{^238}U) ratios to explain global MORB data. We find that the {^235}U-{^231}Pa system is particularly sensitive to the presence of eclogite in the source: both porous flow and dynamic melts of eclogitic sources generate lower ({^231}Pa/{^235}U) ratios than peridotitic melts due to the increased melt rates and overall melt fractions invoked by eclogite melting. Further work should explore two-dimensional regimes while explicitly considering both lithologic heterogeneity and expected variations in melt productivity and partition coefficients.

Elkins, L. J.; Sims, K. W.

2011-12-01

283

Probing depth dependencies of melt emplacement on time dependent quantities in a continental rift scenario with melting and melt extraction  

NASA Astrophysics Data System (ADS)

Since some years seismological observations provide increasing evidence of a discontinuity near the mid of older mantle lithosphere. Explanation may be a melt infiltration front (MIF) as upper margin of an evolving network of veins. These are formed by crystallized melt supplied by episodic melting events in the asthenosphere. To test this concept geodynamically we performed numerical modelling applying melting, extraction of melt and emplacement in a viscous matrix. Thereupon, we were faced to the problem defining an intrusion level for the melt. Findings of prior studies led to the need of movable, process dependent boundaries of the emplacement zone additionally making the process probably more self-consistent. Here we present a preliminary study exploring several empirical attempts to relate time dependent states to an upward moving boundary for intrusion. Modeled physics is based on thermo-mechanics of visco-plastic flow. The equations of conservation of mass, momentum and energy are solved for a multi component (crust-mantle) and two phase (melt-matrix) system. Rheology is temperature-, pressure-, and stress-dependent. In consideration of depletion and enrichment melting and solidification are controlled by a simplified linear binary solid solution model. The Compaction Boussinesq Approximation and the high Prandtl number approximation are used, elasticity is neglected and geometry is restricted to 2D. Approximation is done with the Finite Difference Method with markers in an Eulerian formulation (FDCON). Model guiding scenario is a extending thick lithosphere associated to by updoming asthenosphere probably additionally heated by a plume nearby. As the P-T conditions in the asthenosphere are near the solidus caused changes may increase melting and generate partial melt. Against conventional expectations on permeability at lithosphere-asthenosphere boundary (LAB) depth a fast melt transport into and sometimes through the lithosphere often is observed. The intruded or infiltrated, solidified melt modifies composition and physical properties of the affected lithosphere. Above a critical fraction limit melt is extracted and intruded above. The uppermost front of extraction, petrophysically seen as LAB, defines the lower boundary of the emplacement zone. The upper boundary is related to various quantities, particularly temperature, melt curve, melt front, stress, dynamic pressure and more. Changes of intrusion level imply different convection patterns affecting intensity of erosion of the lower lithosphere, doming rate of asthenosphere and melt-induced weakening. Thus, the shape and location and therefore its dependence influences intensively the dynamics of rifting.

Wallner, Herbert; Schmeling, Harro

2014-05-01

284

A History of one Olivine Crystal: Microsampling Melt Inclusions by Wire Saw  

NASA Astrophysics Data System (ADS)

Melt inclusions record magma composition, magma volatiles and magma depth (from volatile saturation pressures), but multiple melt inclusions are difficult to study within a single crystal. Often the sample geometry and preparation requirements (e.g. FTIR wafer) limit sampling density to one melt inclusion per crystal. Thus suites of crystals are studied but the relationship between multiple crystals and their melt inclusions must be inferred. Crystal mass has been used as a temporal constraint for melt inclusions (EPSL 187 p.221), but questions remain about crystal growth mechanisms, growth rates and possible hybridism. This study uses microsampling to investigate the melt inclusion record preserved within a single phenocryst. A large euhedral olivine crystal (2.2 x 4.5 mm) from the 1999 eruption of Cerro Negro volcano, Nicaragua has been sectioned with a wire saw to isolate multiple melt inclusions. The size of the host crystal and the wide spatial distribution of the melt inclusions indicate that inclusion formation occurred repeatedly throughout the crystal's growth history rather than during a single event. The crystal was first photographed to record melt inclusion position and then sectioned to recover 22 individual melt inclusions and several gas inclusions. The host phenocryst is unzoned (Fo82) except for slight zoning at the rim (Fo77). Locally the rim is resorbed or displays unsealed hourglass inclusions. Most melt inclusions have a single vapor bubble and the volume, as percentage of total volume, is lowest near the core of the crystal (1.8%\\ ) and shows an apparent increase outward (3-4%\\ ). All seven identified gas inclusions, containing little or no silicate glass, occur near the outer crystal edge consistent with the observed bubble volume trend in silicate inclusions. Melt inclusion compositions are restricted (all but four 0.18 to 0.26 wt.%\\ K2O, others 0.41 to 0.43 wt.%\\ K2O) relative to those found in more common, small to moderate-size phenocrysts from the same eruptive unit (0.18 to 0.72 wt.%\\ K2O). The melt inclusions with elevated K2O (> 0.40 wt.%\\ ) are located near the core of the crystal and are also distinguished by high S and low Cl relative to melt inclusions in small to moderate-size phenocrysts. This compositional pattern apparently records an early perturbation (decreased K2O, S and moderate Cl increase) followed by relatively stable conditions. The variation can be explained by fractional crystallization and repeated magma recharge. The high K2O and sulfur within interior melt inclusions is interpreted as due to early closed-system enrichment, although low Cl requires previous gas loss. Later recharge events produced relatively constant K2O, sulfur and chlorine. FTIR measurements on microsampled melt inclusions are currently under investigation and will be compared to associated small and moderate-size phenocrysts hosting compositionally similar melt inclusions. It is expected that the results for the large phenocryst will exceed volatile saturation pressures (H2O and CO2) of associated small and moderate-size phenocrysts ( ˜1.5 to 3 kb) indicating deep magma storage and movement prior to the 1999 earthquake and eruption sequence.

Roggensack, K.; Hervig, R. L.

2003-12-01

285

Transcrystalline melt migration and Earth's mantle.  

PubMed

Plate tectonics and volcanism involve the formation, migration, and interaction of magma and gas. Experiments show that melt inclusions subjected to a thermal gradient migrate through olivine crystals, under the kinetic control of crystal-melt interface mechanisms. Exsolved gas bubbles remain fixed and eventually separate from the melt. Scaled to thermal gradients in Earth's mantle and geological times, our results account for the grain-scale segregation of primitive melts, reinterpret CO2-rich fluid inclusions as escaped from melt, and question the existence of a free, deeply percolating fluid phase. Melt migration experiments also allow us to quantify crystal growth kinetics at very low undercoolings in conditions appropriate to many natural systems. PMID:17095697

Schiano, Pierre; Provost, Ariel; Clocchiatti, Roberto; Faure, François

2006-11-10

286

450 kW plasma melting system  

NASA Astrophysics Data System (ADS)

Plasma melting technology can be used to meet the scrap recycle needs of reactive metals, superalloys and refractory materials such as titanium, zirconium and uranium alloys. Fabrication involving these reactive metals, share the common problem of generating a large amount of scrap where both low and high density inclusions become highly prevalent. Plasma melting technology can be used for re-melting, refining and production of premium grade metal ingot. 450kW multi-torch plasma melting furnace is developed and commissioned by Laser & Plasma Technology Division for the re-melting and refining of metals and scraps under controlled environment. This paper presents the vacuum system design for 450 kW plasma melting furnace. The efficacy of vacuum system in cold condition is also tested and the results are included in the paper. The vacuum feed through design for the plasma torch handling mechanism is also discussed.

Jha, M. N.; Sahashrabuddhe, S. N.; Murthy, P. S. S.; Bapat, A. V.; Das, A. K.

2008-05-01

287

Numerical simulation of a Hypothetical Core Disruptive Accident in a small-scale model of a nuclear reactor  

Microsoft Academic Search

In the case of a Hypothetical Core Disruptive Accident (HCDA) in a Liquid Metal Fast Breeder Reactor, it is assumed that the core of the nuclear reactor has melted partially and that the chemical interaction between molten fuel and liquid sodium has created a high-pressure gas bubble in the core. The violent expansion of this bubble loads and deforms the

M. F. Robbe; M. Lepareux; E. Treille; Y. Cariou

2003-01-01

288

Conformal quivers and melting molecules  

NASA Astrophysics Data System (ADS)

Quiver quantum mechanics describes the low energy dynamics of a system of wrapped D-branes. It captures several aspects of single and multicentered BPS black hole geometries in four-dimensional = 2 supergravity such as the presence of bound states and an exponential growth of microstates. The Coulomb branch of an Abelian three node quiver is obtained by integrating out the massive strings connecting the D-particles. It allows for a scaling regime corresponding to a deep AdS2 throat on the gravity side. In this scaling regime, the Coulomb branch is shown to be an SL(2, ?) invariant multi-particle superconformal quantum mechanics. Finally, we integrate out the strings at finite temperature — rather than in their ground state — and show how the Coulomb branch `melts' into the Higgs branch at high enough temperatures. For scaling solutions the melting occurs for arbitrarily small temperatures, whereas bound states can be metastable and thus long lived. Throughout the paper, we discuss how far the analogy between the quiver model and the gravity picture, particularly within the AdS2 throat, can be taken.

Anninos, Dionysios; Anous, Tarek; de Lange, Paul; Konstantinidis, George

2015-03-01

289

Conformal Quivers and Melting Molecules  

E-print Network

Quiver quantum mechanics describes the low energy dynamics of a system of wrapped D-branes. It captures several aspects of single and multicentered BPS black hole geometries in four-dimensional $\\mathcal{N} = 2$ supergravity such as the presence of bound states and an exponential growth of microstates. The Coulomb branch of an Abelian three node quiver is obtained by integrating out the massive strings connecting the D-particles. It allows for a scaling regime corresponding to a deep AdS$_2$ throat on the gravity side. In this scaling regime, the Coulomb branch is shown to be an $SL(2,\\mathbb{R})$ invariant multi-particle superconformal quantum mechanics. Finally, we integrate out the strings at finite temperature---rather than in their ground state---and show how the Coulomb branch `melts' into the Higgs branch at high enough temperatures. For scaling solutions the melting occurs for arbitrarily small temperatures, whereas bound states can be metastable and thus long lived. Throughout the paper, we discuss how far the analogy between the quiver model and the gravity picture, particularly within the AdS$_2$ throat, can be taken.

Dionysios Anninos; Tarek Anous; Paul de Lange; George Konstantinidis

2013-10-29

290

Melting a Sample within TEMPUS  

NASA Technical Reports Server (NTRS)

One of the final runs of the TEMPUS experiment shows heating of a sample on STS-94, July 15, 1997, MET:14/11:01 (approximate) and the flows on the surface. At the point this image was taken, the sample was in the process of melting. The surface of the sample is begirning to flow, looking like the motion of plate tectonics on the surface of a planet. During this mission, TEMPUS was able to run than 120 melting cycles with zirconium, with a maximum temperature of 2,000 degrees C, and was able to undercool by 340 degrees -- the highest temperature and largest undercooling ever achieved in space. The TEMPUS investigators also have provided the first measurements of viscosity of palladium-silicon alloys in the undercooled liquid alloy which are not possible on Earth. TEMPUS (stands for Tiegelfreies Elektromagnetisches Prozessiere unter Schwerelosigkeit (containerless electromagnetic processing under weightlessness). It was developed by the German Space Agency (DARA) for flight aboard Spacelab. The DARA project scientist was Igon Egry. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). DARA and NASA are exploring the possibility of flying an advanced version of TEMPUS on the International Space Station.(176KB JPEG, 1350 x 1516 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300193.html.

2003-01-01

291

Allanite behaviour during incipient melting in the southern Central Alps  

NASA Astrophysics Data System (ADS)

The response of allanite to incipient melting was investigated in migmatites from the Tertiary Barrovian-type sequence of the Central Alps (southern Switzerland, northern Italy). Inheritance and new mineral growth were recorded in composite allanite grains sampled from meta-granitoids and leucosomes. Ion microprobe (SHRIMP) dating of high Th/U allanite cores in meta-granitoids yield Permian ages consistent with magmatic crystallisation dating protolith intrusion. In contrast, low Th/U allanite overgrowths and weakly-zoned allanite in meta-granitoids and leucosomes yield Alpine U-Pb intercept ages between 30 ± 4 and 20 ± 5 Ma; these date allanite formation during the Barrovian cycle. Major and accessory mineral REE compositions suggest that Alpine allanite crystallised in the presence of a low-temperature melt. Whereas new zircon growth is rare in the migmatites, allanite readily recorded growth during the Alpine cycle. Allanite U-Th-Pb isotopes may therefore present a complementary approach to zircon for dating low-temperature partial melting, where the preservation of allanite is aided by low LREE solubility in hydrous granitic melt. The Th-Pb age is preferred to date high-Th magmatic allanite, however the U-Pb and Th-Pb ages of allanite overgrowths may differ (by up to 25%), and this demands a comparison of both U-Pb and Th-Pb isotopic systems to obtain a best estimate for the timing of low-Th allanite crystallisation. Protolith allanite preserves a substantial memory of its initial age in spite of upper amphibolite facies re-working during migmatisation (T = 620-700 °C), which places strong constraints on Pb closure temperature. Magmatic allanite contains <30% of initial (non-radiogenic) Pb, allanite in migmatites is characterised by an initial Pb of 20-70%, and subsolidus allanite has >60% of initial Pb. Therefore, the initial Pb may be useful as a sensor for the amount of melt present during allanite formation. The Pb isotope composition of allanite overgrowths indicates ?5% inherited radiogenic Pb from precursor allanite, which suggests efficient redistribution and homogenisation of Pb isotopes during the Alpine partial melting period.

Gregory, C. J.; Rubatto, D.; Hermann, J.; Berger, A.; Engi, M.

2012-05-01

292

Seismogenic frictional melting in the magmatic column as the driving force of stick-slip motion  

NASA Astrophysics Data System (ADS)

Lava dome eruptions subjected to high extrusion rates commonly evolve from endogenous to exogenous growth and limits to their structural stability hold catastrophic potential as explosive eruption triggers. In the conduit strain localisation in magma, accompanied by seismogenic failure, marks the onset of brittle magma ascent dynamics. The rock record of exogenous dome structures preserves vestiges of cataclastic processes and of thermal anomalies, key to unravelling subsurface processes. A combined structural, thermal and magnetic investigation of shear bands from Mount St. Helens (MSH) and Soufrière Hills volcano (SHV) reveal evidence of faulting and frictional melting within the magmatic column. High velocity rotary shear (HVR) experiments demonstrate the propensity for melting of andesitic and dacitic material (from SHV and MSH respectively) at upper conduit stress conditions. Such melting events may be linked to the step-wise extrusion of magma accompanied by repetitive long-period (LP) seismicity. Using a source duration calculated from the waveforms at seismic stations around SHV, and slip distance per drumbeat calculated from extrusion rate, frictional melting of SHV andesite in a high velocity rotary shear apparatus can be achieved at small slip distances (<15cm) in 0.15 s from 800°C magma (at 10MPa). The shear resistance of the slip zone during the experiments is also monitored. Frictional melting induces a higher resistance to sliding than rock on rock, and viscous processes control the slip zone properties. Variable-rate HVR experiments which mimic rapid velocity fluctuations in stick-slip behavior demonstrate velocity-weakening behavior of melt, with a tendency for unstable slip. We postulate that pseudotachylyte generation could be the underlying cause of stick-slip motion and associated seismic 'drumbeats', which are so commonly observed at dome-building volcanoes, allowing for a fixed spatial locus and the occurrence of 'families' of similar seismic events. We conclude that, given the ease with which melting is achieved in volcanic rocks, and considering the high ambient temperatures in volcanic conduits, frictional melting is a highly probable consequence of viscous magma ascent.

Kendrick, J. E.; Lavallee, Y.; Hirose, T.; Di Toro, G.; Hornby, A.; De Angelis, S.; Henton De Angelis, S.; Ferk, A.; Hess, K.; Leonhardt, R.; Dingwell, D. B.

2013-12-01

293

Aluminium control of argon solubility in silicate melts under pressure.  

PubMed

Understanding of the crystal chemistry of the Earth's deep mantle has evolved rapidly recently with the gradual acceptance of the importance of the effect of minor elements such as aluminium on the properties of major phases such as perovskite. In the early Earth, during its formation and segregation into rocky mantle and iron-rich core, it is likely that silicate liquids played a large part in the transport of volatiles to or from the deep interior. The importance of aluminium on solubility mechanisms at high pressure has so far received little attention, even though aluminium has long been recognized as exerting strong control on liquid structures at ambient conditions. Here we present constraints on the solubility of argon in aluminosilicate melt compositions up to 25 GPa and 3,000 K, using a laser-heated diamond-anvil cell. The argon contents reach a maximum that persists to pressures as high as 17 GPa (up to 500 km deep in an early magma ocean), well above that expected on the basis of Al-free melt experiments. A distinct drop in argon solubility observed over a narrow pressure range correlates well with the expected void loss in the melt structure predicted by recent molecular dynamics simulations. These results provide a process for noble gas sequestration in the mantle at various depths in a cooling magma ocean. The concept of shallow partial melting as a unique process for extracting noble gases from the early Earth, thereby defining the initial atmospheric abundance, may therefore be oversimplified. PMID:16495996

Bouhifd, M Ali; Jephcoat, Andrew P

2006-02-23

294

Melt pelletization in high shear mixer using a hydrophobic melt binder: influence of some apparatus and process variables.  

PubMed

The effects of process conditions and the apparatus variables on the granulometric characteristics of a formulation containing a hydrophobic binder (stearic acid), lactose and paracetamol prepared by melt pelletization process were investigated in a 10-litre high shear mixer. The factors under investigation were: impeller speed, massing time, type of impeller blades and presence of the deflector and their reciprocal interactions. Two granule characteristics were analysed: the percentage of aggregates larger than 3000 microm (Y(1)) and the yield of the 2000-microm pellet size fraction (Y(2)). In order to estimate simultaneously the above-mentioned factors, a particular experimental design was adopted, that allowed the reduction of the number of trials from 378 to 35 and took into consideration other uncontrolled factors with the aid of a block variable. Using the postulated model, we found the optimal operating conditions to minimize Y(1) and increase Y(2) by selecting the type of impeller, and by using an impeller speed lower than 300 rpm, a massing time of 8-9 min and by not using the deflector. Finally, the validity of the adopted strategy has been proved with an additional check point. PMID:11677073

Voinovich, D; Moneghini, M; Perissutti, B; Franceschinis, E

2001-11-01

295

Stone castings from low iron melts  

Microsoft Academic Search

Castings of the basalt-melt type have a high chemical and adequate mechanical strength, but low thermal-shock resistance, and are prone to form cracks at high temperatures. The production of large castings 80-120 mm thick, from such melts is very difficult, The use of silicate melts with very low contents of iron oxides increases the thermal-shock resistance, and somewhat extends the

B. Kh. Khan; I. I. Bykov; S. V. Ladokhin; Zh. D. Bogatyreva; P. P. Panyushkin

1967-01-01

296

Certain petrological features of impact melts  

NASA Astrophysics Data System (ADS)

A cluster analysis of impactites and target rocks of the Zhamanshin and Manicouagan astroblemes was carried out. Two types of impact melts were found to exist: (1) highly homogeneous melts resulting from intense mixing during motion in the crater cavity and (2) heterogeneous melts which consist mainly of a single rock and result from ejections of matter that did not have the time to become homogeneous prior to the ejection.

Fel'Dman, V. I.; Riakhovskii, V. M.

297

Surface melting on ice shelves and icebergs  

NASA Astrophysics Data System (ADS)

Disintegration of Larsen Ice Shelf A and B, in 1995 and 2002, respectively, were preceded by two decades of extended summer melt seasons and by surface melt-water accumulation in ponds, surface crevasses and depressions produced by the elastic flexure of the ice. The extraordinary rapidity of ice-shelf fragmentation into large iceberg plumes following the appearance of surface melt water implies that the mechanical effects of surface melt water accumulation may represent an unforeseen process allowing abrupt, large-scale change of Antarctica's ice mass. The present study of surface melting and subsequent movement of melt water, both vertically (i.e., downward percolation into underlying firn) and horizontally (e.g., into crevasses and surface depressions created by ice-shelf flexure in response to both side boundary conditions and the melt-water load itself), is motivated by the need to further describe the energy, mass and momentum balances associated with ice shelves and their surrogates-large tabular icebergs-in the face of unprecedented changes in surface mass balance. The goal of this dissertation is to examine both the thermodynamic and mechanical aspects of surface melting on ice shelves and icebergs subject to sudden changes in climate conditions (e.g ., global warming). Thermodynamic aspects of the study include the development and application of surface energy balance models capable of describing the process of surface melting and subsequent vertical movement of melt water through a porous firn. Mechanical aspects of this study include the analysis of vertical melt-water flow, and more particularly, the elastic flexure response of the ice shelf or iceberg to the melt-water loads. Work presented here involves three methodologies, numerical modeling, field observation, and mathematical analysis (e.g., development of analytic solutions to simple, idealized ice-shelf flexure problems).

Sergienko, Olga V.

298

Water-Fluxed Melting of Continental Crust  

NASA Astrophysics Data System (ADS)

A difficulty in understanding water present melting in continental crust is the question of how to get water inside hot rocks. Here, we investigate this process in exposures of the High Himalayan Crystalline (HHC) in Zanskar region, NW India. This is a sequence of medium- to high-grade rocks intruded by leucogranites. Rocks underwent early dehydration melting that was later overprinted by water-fluxed melting producing extensive migmatites. Each event is recognizable in the field: early dehydration melting has produced leucosomes with peritectic garnet and sillimanite, in contrast to tourmaline-rich, two-mica leucosomes and leucogranites associated with later water-fluxed melting. Potential water source here are the underlying cooler rocks that were heated and dehydrated by the thrusting of the hot rocks of the HHC. This water migrated upwards causing extensive melting of the overlying hot rocks. We conclude that water is driven into hot rocks by channels, either fractures or magma channels where water is carried by saturated melts or as a separate fluid phase in oversaturated melts. From these channels, water is driven further into the rock mass by water activity gradients which leads to outcrop-scale variation in volume of melt produced, recorded by the preserved mineral composition record in garnet and monazite. Thus, rocks that underwent the same P-T history have preserved a mixed signal related to fluctuation in water content of activity, rather than to changes in P-T conditions.

Weinberg, R. F.; Hasalova, P.

2012-12-01

299

Disequilibrium melt distributions during static recrystallisation  

NASA Astrophysics Data System (ADS)

DISEQUILIBRIUM MELT DISTRIBUTIONS DURING STATIC RECRYSTALLISATION N.P. Walte (1), P.D. Bons (2), C.W. Passchier (1), D. Koehn (1), J. Arnold (1) (1) Institute for Earth Sciences, Johannes Gutenberg-University, Mainz, Germany, (2) Institute for Earth Sciences, Eberhard Karls University, Tübingen, Germany (walte@mail.uni-mainz.de) The geometry of melt-filled pores in a partially molten rock strongly controls the permeability, rheology and initial segregation of melt. Current theory for monomineralic aggregates, using only the wetting angle and melt fraction as parameters, predicts a perfectly regular melt framework or equally shaped melt inclusions on grain boundary junctions. However, published melt-present high-temperature experiments with rock forming minerals such as quartz or olivine show considerable deviations from this predicted regular equilibrium melt geometry. Disequilibrium features, such as fully wetted grain boundaries, melt lenses, and large melt patches have been described, and were attributed to surface energy anisotropy of the minerals. This study used static analogue experiments with norcamphor plus ethanol liquid, that allow continuous in-situ observation of the evolving distribution of melt during static recrystallisation. The liquid-crystal surface energy of norcamphor is effectively isotropic. For the experiments an approximately 0.1 mm thin sample of norcamphor plus ethanole was placed between two glass plates and observed with a miroscope. Ethanol was used as a melt analogue because it allows to run experiments at room temperature, avoiding any temperature gradients. The wetting angle is approximately 15°, which is well below 60° and within the range reported for quartz and olivine plus melt experiments. The experiments show that all described disequilibrium features can form during fluid-enhanced static recrystallisation, especially where surrounding grains consume small, few-sided grains. These features are unstable and transient: a fully wetted grain boundary may, for example, evolve to a trapped melt lens. Our experiments demonstrate that the effect of static recrystallisation alone suffices to explain the deviations from predicted ideal melt distributions. There is no need to invoke surface energy anisotropy, although this would enhance the effect. Current wetting-angle-based theory is therefore not sufficient to predict permeability and transport of melt or fluids and the rheology of partially molten rocks.

Walte, N. P.; Bons, P. D.; Passchier, C. W.; Koehn, D.; Arnold, J.

2003-04-01

300

Lunar Simple Crater Impact Melt Volumes  

NASA Technical Reports Server (NTRS)

Impact melt is observed in simple lunar craters having diameters as small as less than 200 m. The presence of ponds of impact melt on the floor of such small craters is interpreted to indicate vertical impacts. Data from the LRO LROC and LOLA experiments allow quantitative estimates of the volume of impact melt in simple crater. Such estimates allow for validation of theoretical models of impact melt generation and examination of target effects. Preliminary data have considerable scatter but are broadly consistent with the models.

Plescia, Jeffrey B.; Barnouin, O. S.; Cintala, Mark J.

2013-01-01

301

Impact Melt in Small Lunar Highlands Craters  

NASA Technical Reports Server (NTRS)

Impact-melt deposits are a typical characteristic of complex impact craters, occurring as thick pools on the crater floor, ponds on wall terraces, veneers on the walls, and flows outside and inside the rim. Studies of the distribution of impact melt suggested that such deposits are rare to absent in and around small (km to sub-km), simple impact craters. noted that the smallest lunar crater observed with impact melt was approximately 750 m in diameter. Similarly, theoretical models suggest that the amount of melt formed is a tiny fraction (<1%) of the total crater volume and thus significant deposits would not be expected for small lunar craters. LRO LROC images show that impact-melt deposits can be recognized associated with many simple craters to diameters down to approximately 200 m. The melt forms pools on the crater floor, veneer on the crater walls or ejecta outside the crater. Such melt deposits are relatively rare, and can be recognized only in some fresh craters. These observations indicate that identifiable quantities of impact melt can be produced in small impacts and the presence of such deposits shows that the material can be aggregated into recognizable deposits. Further, the present of such melt indicates that small craters could be reliably radiometrically dated helping to constrain the recent impact flux.

Plescia, J. B.; Cintala, M. J.; Robinson, M. S.; Barnouin, O.; Hawke, B. R.

2011-01-01

302

Melting of Sn to 1 Mbar  

NASA Astrophysics Data System (ADS)

The melting point of Sn was determined between 20-105 GPa using laser-heated diamond anvil cell experiments, coupled with in situ synchrotron X-ray diffraction studies. In agreement with previous LH-DAC speckle experiments, we observe a flattening of the melting slope between P = 40-60 GPa. However, we also observe that this plateau is followed by a further increase in the melting slope above P ~ 70 GPa, leading to a remarkably high melting point of Tm = 5500 K by P = 105 GPa.

Briggs, R.; Daisenberger, D.; Salamat, A.; Garbarino, G.; Mezouar, M.; Wilson, M.; McMillan, P. F.

2012-07-01

303

Potential health risks from postulated accidents involving the Pu-238 RTG (radioisotope thermoelectric generator) on the Ulysses solar exploration mission  

SciTech Connect

Potential radiation impacts from launch of the Ulysses solar exploration experiment were evaluated using eight postulated accident scenarios. Lifetime individual dose estimates rarely exceeded 1 mrem. Most of the potential health effects would come from inhalation exposures immediately after an accident, rather than from ingestion of contaminated food or water, or from inhalation of resuspended plutonium from contaminated ground. For local Florida accidents (that is, during the first minute after launch), an average source term accident was estimated to cause a total added cancer risk of up to 0.2 deaths. For accidents at later times after launch, a worldwide cancer risk of up to three cases was calculated (with a four in a million probability). Upper bound estimates were calculated to be about 10 times higher. 83 refs.

Goldman, M. (California Univ., Davis, CA (USA)); Nelson, R.C. (EG and G Idaho, Inc., Idaho Falls, ID (USA)); Bollinger, L. (Air Force Inspection and Safety Center, Kirtland AFB, NM (USA)); Hoover, M.D. (Lovelace Biomedical and Environmental Research Inst., Albuquerque, NM (USA). Inhalation Toxicology Research Inst.); Templeton, W. (Pacific Northwest Lab., Richland, WA (USA)); Anspaugh, L. (Lawren

1990-11-02

304

Potential health risks from postulated accidents involving the Pu-238 RTG on the Ulysses solar exploration mission  

NASA Technical Reports Server (NTRS)

Potential radiation impacts from launch of the Ulysses solar exploration experiment were evaluated using eight postulated accident scenarios. Lifetime individual dose estimates rarely exceeded 1 mrem. Most of the potential health effects would come from inhalation exposures immediately after an accident, rather than from ingestion of contaminated food or water, or from inhalation of resuspended plutonium from contaminated ground. For local Florida accidents (that is, during the first minute after launch), an average source term accident was estimated to cause a total added cancer risk of up to 0.2 deaths. For accidents at later time after launch, a worldwide cancer risk of up to three cases was calculated (with a four in a million probability). Upper bound estimates were calculated to be about 10 times higher.

Goldman, Marvin; Hoover, Mark D.; Nelson, Robert C.; Templeton, William; Bollinger, Lance; Anspaugh, Lynn

1991-01-01

305

Does Mercury have a molten core  

NASA Technical Reports Server (NTRS)

The question of whether or not Mercury could contain a molten metallic core is investigated by studying the possible thermal evolution of a metallic core in that planet. The calculations involve the solution of the equation of heat conduction for a spherically symmetric body with internal heat sources, modifications to take account of the latent heat of fusion as well as the redistribution of radioactive heat sources as a consequence of melting, the terrestrial Fe/U ratio, and a Th/U ratio of 3.7. The temperature profile predicted by the calculations for a period of 4.6 billion years indicates that the inner 1400 km of the core would now be solid while the outer 500 km would be molten. It is emphasized that this result is a direct consequence of a discontinuity in melting temperatures at the core-mantle boundary and that although a dynamo is possible, it would have to be driven mechanically rather than by thermal convection.

Fricker, P. E.; Reynolds, R. T.; Summers, A. L.; Cassen, P. M.

1976-01-01

306

NREL Scientists Reveal Origin of Diverse Melting Behaviors of Aluminum Nanoclusters (Fact Sheet)  

SciTech Connect

Research reveals active role of cluster symmetries on the size-sensitive, diverse melting behaviors of metallic nanoclusters, providing insight to understanding phase changes of nanoparticles for thermal energy storage. Unlike macroscopic bulk materials, intermediate-sized nanoclusters with around 55 atoms inherently exhibit size-sensitive melting changes: adding just a single atom to a nanocluster can cause a dramatic change in melting behavior. Microscopic understanding of thermal behaviors of metal nanoclusters is important for nanoscale catalysis and thermal energy storage applications. However, it is a challenge to obtain a structural interpretation at the atomic level from measured thermodynamic quantities such as heat capacity. Using ab initio molecular dynamics simulations, scientists at the National Renewable Energy Laboratory (NREL) revealed a clear correlation between the diverse melting behaviors of aluminum nanoclusters and cluster core symmetries. These simulations reproduced, for the first time, the size-sensitive heat capacities of aluminum nanoclusters, which exhibit several distinctive shapes associated with the diverse melting behaviors of the clusters. The size-dependent, diverse melting behaviors of the aluminum clusters are attributed to the reduced symmetry (from Td {yields} D2d {yields} Cs) with increasing the cluster sizes and can be used to help design thermal storage materials.

Not Available

2011-10-01

307

Molecular dynamics simulation of melting of fcc Lennard-Jones nanoparticles  

NASA Astrophysics Data System (ADS)

Melting of fcc Lennard-Jones (LJ) nanoparticles is studied by heating up models from low temperature toward liquid phase using molecular dynamics (MD) simulation. Atomic mechanism of melting is analyzed via temperature dependence of potential energy, heat capacity, analysis of the spatio-temporal arrangements of liquidlike atoms occurred during the heating process. Moreover, radial distribution function (RDF), mean-squared displacement (MSD) of atoms and radial density profile are also used for deeper analyzing melting. Surface melting is under much attention. We also analyze the evolution of structure of nanoparticles upon heating via the global order parameter Q6 and Honeycutt-Andersen (HA) analysis. We find previously unreported information as follows. At temperature far below a melting point, a quasi-liquid layer containing both liquidlike and solidlike atoms occurs in the surface shell of nanoparticles unlike that thought in the past. Further heating leads to the formation of a purely liquid layer at the surface and homogeneous occurrence/growth of liquidlike atoms throughout the interior of nanoparticles. Melting proceeds further via two different mechanisms: homogeneous one in the interior and propagation of liquid front from the surface into the core leading to fast collapse of crystalline matrix.

Van Sang, Le; Van Hoang, Vo; Thi Thuy Hang, Nguyen

2013-03-01

308

Quantum model for psychological measurements: from the projection postulate to interference of mental observables represented as positive operator valued measures  

E-print Network

Recently foundational issues of applicability of the formalism of quantum mechanics (QM) to cognitive psychology, decision making, and psychophysics attracted a lot of interest. In particular, in \\cite{DKBB} the possibility to use of the projection postulate and representation of "mental observables" by Hermitian operators was discussed in very detail. The main conclusion of the recent discussions on the foundations of "quantum(-like) cognitive psychology" is that one has to be careful in determination of conditions of applicability of the projection postulate as a mathematical tool for description of measurements of observables represented by Hermitian operators. To represent some statistical experimental data (both physical and mental) in the quantum(-like) way, one has to use generalized quantum observables given by positive operator-valued measures (POVMs). This paper contains a brief review on POVMs which can be useful for newcomers to the field of quantum(-like) studies. Especially interesting for cognitive psychology is a variant of the formula of total probability (FTP) with the interference term derived for incompatible observables given by POVMs. We present an interpretation of the interference term from the psychological viewpoint. As was shown before, the appearance of such a term (perturbing classical FTP) plays the important role in cognitive psychology, e.g., recognition of ambiguous figures and the disjunction effect. The interference term for observables given by POVMs has much more complicated structure than the corresponding term for observables given by Hermitian operators. We elaborate cognitive interpretations of different components of the POVMs-interference term and apply our analysis to a quantum(-like) model of decision making.

Andrei Khrennikov; Irina Basieva

2014-05-06

309

Systematics of melt stagnation in peridotites from the Godzilla Megamullion  

NASA Astrophysics Data System (ADS)

The Godzilla Megamullion (GM) Massif is the largest known example of an Oceanic Core Complex (OCC) or the exhumed footwall of a low angle-large offset oceanic detachment fault. It lies on the extinct Parece Vela Rift spreading center within the Parece Vela Back-arc Basin of the Philippine Sea. This has thus allowed for sampling of a young back-arc mantle section. Sampling of the massif has returned a dominantly ultramafic lithology, divided petrographically into depleted, fertile, and melt-percolated groups (1). Petrographic analysis of the extant peridotite thin section collection found that 44% of all GM peridotites (71 out of 161) exhibit evidence of plagioclase impregnation compared to the worldwide abyssal peridotite average of ~20% (2). The mullion is divided up into three regions, the proximal region ( closest to termination of spreading), the medial region, and the distal region (furthest from the termination of spreading)(3).Observations by region provide that 53% ( 62 out of 116 samples) in the proximal region (15 dredges), 12% ( 2 out of 17 samples) in the medial mullion (3 dredges), and 25% (7 out of 28) in the distal mullion (5 dredges) show of evidence of plagioclase impregnation (4). Major element analyses of spinels were completed using the Cameca SX-50 Electron Microprobe facility at the University of Houston. The Cr# [100 x Cr/(Cr + Al)] ranges from 10 to 65 with TiO2 concentrations ranging from less than 0.01 up to 1.6 wt%. When the Cr#s of the samples are plotted along the massif, a pattern of melt depletion exists that is consistent with the degree of plagioclase impregnation. In the distal region, Cr#s start at around an average of 35 and range up to 65 for melt percolated samples. In the medial region, a drop off in Cr# of about 1 Cr# per kilometer is observed with the trend bottoming out at around a Cr# of 10. In the proximal region, Cr#s closer to the medial region are observed as having more fertile values of around 20 but are found amongst melt-impregnated samples with values ranging up to 50. This range is seen as having increasing minimum and maximum values with distance away from the medial section until it reaches its peak at a base Cr# of 30 with a maximum of 65. From this trend, a general model for the secular evolution of the GM mantle section can be established (5). The ridge segment experienced normal mid-oceanic ridge growth with robust mantle melting during the time period represented by the distal region. At the boundary to the medial region, a steep drop-off in melt productivity was experienced, leading to minimal mantle melting during the time period represented by the medial region. Soon thereafter, melting began again, but was trapped in a thickened and cooling lithosphere, causing the melt to pool and react with its host peridotite. (1) Ohara, et al., (2003) G3. 4 (7), 8611, 10.1029/2002GC000469. (2) Dick (1989) Geol Soc. Lond. Spec. Pub. 42:71-105. (3) Ohara, et al., (2009), Eos Trans. AGU, 90(52), Fall Meet. Suppl. Abst.Num. T33D-06 (4) Loocke, et al., (2009), Eos Trans. AGU, 90(52), Fall Meet. Suppl. Abst.Num. T21A-1776 (5) Snow, et al., (2009), Eos Trans. AGU, 90(52), Fall Meet. Suppl. Abst.Num. T33D-07

Loocke, M.; Snow, J. E.; Ohara, Y.

2010-12-01

310

Partitioning REE between minerals and coexisting melts during partial melting of a garnet lherzolite  

NASA Technical Reports Server (NTRS)

Partition coefficients for Ce, Sm, and Tm between garnet, clinopyroxene, orthopyroxene, olivine, and melt are determined at 35 kbar for 2.3, 8, 20, and 37.7% melting of a garnet lherzolite nodule with chondritic REE abundances. Partition coefficients are found to increase as the degree of partial melting increases. From 2.3 to 8% melting, this increase is for the most part a consequence of non-Henry's law behavior of REE in minerals.

Harrison, W. J.

1981-01-01

311

Manufacturing by combining Selective Laser Melting and Selective Laser Erosion\\/laser re-melting  

Microsoft Academic Search

This study presents an experimental investigation to improve Selective Laser Melting (SLM) regarding aspects such as surface roughness, density, precision and micro machining capability by employing secondary processes such as Selective Laser Erosion (SLE) and laser re-melting. SLM is a layered additive manufacturing technique for the direct fabrication of functional parts by fusing together metal powder particles. Laser re-melting, applied

E. Yasa; J.-P. Kruth; J. Deckers

2011-01-01

312

Main results of study on the interaction between the corium melt and steel in the VVER-1000 reactor vessel during a severe accident performed under the MASCA project  

NASA Astrophysics Data System (ADS)

The interactions that take place in the corium melt in the reactor vessel in the case of a severe accident at a nuclear power plant were investigated in accordance with the MASCA international program. Results of the interaction between the oxide melt and iron (steel), partition of the main components [U, Zr, Fe (stainless steel)] between the oxide and the metal phases of the melt, partition of low-volatile simulators of fission products between the phases of the stratified core melt pool, and impact of the oxidizing atmosphere on the melt stratification are presented. The results obtained were used for prediction of thermodynamic properties of the melts belonging to the U-Zr-Fe-O system.

Asmolov, V. G.; Zagryazkin, V. N.; Tsurikov, D. F.; Vishnevsky, V. Yu.; D'Yakov, Ye. K.; Kotov, A. Yu.; Repnikov, V. M.

2010-12-01

313

Preventing melt-water explosions  

NASA Astrophysics Data System (ADS)

Explosive interactions between molten aluminum and water are being studied at the Oak Ridge National Laboratory to determine the causes of explosion triggers and the extent of protection provided from various coatings in order to develop a fundamental, cost-effective methodology for prevention. The study includes experimentation and mathematical modeling of the interactions between molten metals and water on various coated and uncoated surfaces. Phenomenological issues related to surface wettability, gas generation from coatings, charring of coatings, inertial constraint, melt temperature, water temperature, and external shocks are being investigated systematically to gage their relative impact on the triggerability of surface-assisted steam explosions. A physics-based novel prevention methodology based on enhancing system stability via air (gas) injection at vulnerable locations has been developed and tested at Oak Ridge National Laboratory.

Taleyarkhan, R. P.

1998-02-01

314

Surface melting of electronic order.  

SciTech Connect

We report temperature-dependent surface x-ray scattering studies of the orbital ordered surface in La{sub 0.5}Sr{sub 1.5}MnO{sub 4}. We find that as the bulk ordering temperature is approached from below the thickness of the interface between the electronically ordered and electronically disordered regions at the surface grows, though the bulk correlation length remains unchanged. Close to the transition, the surface is so rough that there is no well-defined electronic surface, despite the presence of bulk electronic order. That is, the electronic ordering at the surface has melted. Above the bulk transition, long-range ordering in the bulk is destroyed but finite-sized isotropic fluctuations persist, with a correlation length roughly equal to that of the low-temperature in-plane surface correlation length.

Wilkins, S. B.; Liu, X.; Wakabayashi, Y.; Kim, J.-W.; Ryan, P. J.; Mitchell, J. F.; Hill, J. P. (Materials Science Division); ( XSD); (BNL); (Osaka Univ.)

2011-01-01

315

Transition metals in superheat melts  

NASA Technical Reports Server (NTRS)

A series of experiments with silicate melts doped with transition element oxides was carried out at atmospheric pressures of inert gas at temperatures exceeding liquidus. As predicted from the shape of fO2 buffer curves in T-fO2 diagrams the reducing conditions for a particular oxide-metal pair can be achieved through the T increase if the released oxygen is continuously removed. Experimental studies suggest that transition metals such as Cr or V behave as siderophile elements at temperatures exceeding liquidus temperatures if the system is not buffered by the presence of other oxide of more siderophile element. For example the presence of FeO prevents the reduction of Cr2O3. The sequence of decreasing siderophility of transition elements at superheat conditions (Mo, Ni, Fe, Cr) matches the decreasing degree of depletion of siderophile elements in mantle rocks as compared to chondrites.

Jakes, Petr; Wolfbauer, Michael-Patrick

1993-01-01

316

M551 metals melting experiment  

NASA Technical Reports Server (NTRS)

Electron beam welding studies were conducted in the Skylab M551 metals melting experiment, on three different materials; namely 2219-T87 aluminum alloy, 304L stainless steel, and commercially pure tantalum (0.5 wt % columbium). Welds were made in both one gravity and zero gravity (Skylab) environments. Segments from each of the welds were investigated by microhardness, optical microscopy, scanning microscopy, and electron probe techniques. In the 2219-T87 aluminum alloy samples, macroscopic banding and the presence of an eutectic phase in the grain boundaries of the heat affected zone were observed. The stainless steel samples exhibited a sharp weld interface and macroscopic bands. The primary microstructural features found in the tantalum were the presence of either columnar grains (ground base) or equiaxed grains (Skylab). The factors contributing to these effects are discussed and the role of reduced gravity in welding is considered.

Busch, G.

1977-01-01

317

Metal-Silicate Segregation in Deforming Dunitic Rocks: Applications to Core Formation in Europa and Ganymede  

NASA Technical Reports Server (NTRS)

Core formation is an important event in the evolution of a planetary body, affecting both the geochemical and geophysical properties of the body. Metal-silicate segregation could have proceeded either by settling of liquid metal through a magma ocean or by percolation of liquid metal through a solid silicate mantle. Percolation of metallic melt had previously been excluded as a viable segregation mechanism because metallic melts do not form an interconnected network under hydrostatic conditions, except at high melt fraction (>5 vol%), due to the high dihedral angle between metals and silicates (>60 ). Without an interconnected network, porous flow of metallic melt is impossible, leaving the magma ocean scenario as the only mechanism to form the core. Moment-of-inertia measurements of Europa and Ganymede from the Galileo probe indicate that they are differentiated. This evidence suggests that a method for segregating metals and silicates at temperatures low enough to retain volatile compounds must exist. We have investigated the effect of deformation on the distribution of metallic melts in silicates. We have deformed samples of olivine + 5-9 vol% Fe-S to strains of 2.5 in simple shear and find that the metallic melt segregates into melt-rich planes oriented at 20 to the shear plane. These metallic melt-rich bands are similar in structure to the silicate melt-rich bands reported by Holtzman, indicating that deformation can interconnect isolated metallic melt pockets and allow porous flow of non-wetting melts. Such a core formation process could have occurred in the jovian satellites.

Hustoft, J. W.; Kohlstedt, D. L.

2004-01-01

318

Experimental Peridotite - melt reaction at one atmosphere: A textural and chemical study.  

NASA Astrophysics Data System (ADS)

Sieve-textured clinopyroxene and spinel are common in mantle xenoliths and have been interpreted to be the result of partial melting, mantle metasomatism and host magma - xenolith reaction during transport. In this paper we test the latter hypothesis with a series of reduced and oxidized experiments at 1200 and 1156 C at one atmosphere using a synthetic leucitite melt and discs of natural peridotite. The experiments were performed at atmospheric pressure so that large sample volumes could be used; this allowed us to use natural peridotite with a grain size of several millimeters which facilitates sample preparation and analysis. The peridotite used in the reaction couples was cored from a 30 cm diameter anhydrous lherzolite xenolith from Meerfelder Maar in the West Eifel volcanic field, Germany (see Witt-Eickschen et al., 1998) for a detailed description of the xenoliths from this locality). The melt used was a synthetic version of a leucitite from the Rockeskyller Kopf volcano, also in the West Eifel. Our results show that sieve texture development on clinopyroxene and spinel in mantle xenoliths is the result of a multistage reaction process. In the first step, orthopyroxene undergoes incongruent dissolution to produce a silica- and alkali-rich melt together with olivine. As this melt migrates along grain boundaries it causes incongruent dissolution of clinopyroxene and spinel. The incongruent dissolution mechanism involves complete dissolution of the clinopyroxene or spinel followed by nucleation and growth of a secondary clinopyroxene or spinel once the reacting melt is saturated. The reaction of orthopyroxene, clinopyroxene and spinel with infiltrated host magma results in a range of melt compositions that are very similar to those observed in nature that have been interpreted to be due to very small degrees of partial melting.

Shaw, C. J.; Dingwell, D. B.

2007-12-01

319

Buoyant melting instabilities beneath extending lithosphere  

E-print Network

. Introduction [2] Upwelling fertile mantle beneath extending litho- sphere may undergo decompression partial melting, and is the typical source of volcanism in most extensional prov- inces on Earth. Decompression unstable behavior. This phenomenon has also been termed a ``decompression melting instability'' by Raddick

Tackley, Paul J.

320

Hot-Melt Extrusion Technique: A Review  

Microsoft Academic Search

Hot-melt extrusion is one of the most widely applied processing technologies in the plastic, rubber and food industry. Today this technology has found its place in the array of pharmaceutical manufacturing operations. Melt extrusion process are currently applied in the pharmaceutical field for the manufacture of a variety of dosage forms and formulations such as granules, pellets, tablets, suppositories, implants,

Rina Chokshi; Hossein Zia

321

Recharging "Hot-Melt" Adhesive Film  

NASA Technical Reports Server (NTRS)

Technique for recharging surface with "hot-melt" film makes use of one sided, high-temperature, pressure-sensitive adhesive tape. Purpose of the one-sided tape is to hold hot-melt charge in place until fused to surface. After adhesive has fused to surface and cooled, tape is removed, leaving adhesive on surface.

Progar, D. J.

1983-01-01

322

Oceanic slab melting and mantle metasomatism.  

PubMed

Modern plate tectonic brings down oceanic crust along subduction zones where it either dehydrates or melts. Those hydrous fluids or melts migrate into the overlying mantle wedge trigerring its melting which produces arc magmas and thus additional continental crust. Nowadays, melting seems to be restricted to cases of young (< 50 Ma) subducted plates. Slab melts are silicic and strongly sodic (trondhjemitic). They are produced at low temperatures (< 1000 degrees C) and under water excess conditions. Their interaction with mantle peridotite produces hydrous metasomatic phases such as amphibole and phlogopite that can be more or less sodium rich. Upon interaction the slab melt becomes less silicic (dacitic to andesitic), and Mg, Ni and Cr richer. Virtually all exposed slab melts display geochemical evidence of ingestion of mantle material. Modern slab melts are thus unlike Archean Trondhjemite-Tonalite-Granodiorite rocks (TTG), which suggests that both types of magmas were generated via different petrogenetic pathways which may imply an Archean tectonic model of crust production different from that of the present-day, subduction-related, one. PMID:11838241

Scaillet, B; Prouteau, G

2001-01-01

323

Natural melting within a spherical shell  

NASA Technical Reports Server (NTRS)

Fundamental heat transfer experiments were performed on the melting of a phase change medium in a spherical shell. Free expansion of the medium into a void space within the sphere was permitted. A step function temperature jump on the outer shell wall was imposed and the timewise evolution of the melting process and the position of the solid-liquid interface was photographically recorded. Numerical integration of the interface position data yielded information about the melted mass and the energy of melting. It was found that the rate of melting and the heat transfer were significantly affected by the movement of the solid medium to the base of the sphere due to gravity. The energy transfer associated with melting was substantially higher than that predicted by the conduction model. Furthermore, the radio of the measured values of sensible energy in the liquid melt to the energy of melting were nearly proportional to the Stefan number. The experimental results are in agreement with a theory set forth in an earlier paper.

Bahrami, Parviz A.

1990-01-01

324

Recent Changes in the Arctic Melt Season  

NASA Technical Reports Server (NTRS)

Melt-season duration, melt-onset and freeze-up dates are derived from satellite passive microwave data and analyzed from 1979 to 2005 over Arctic sea ice. Results indicate a shift towards a longer melt season, particularly north of Alaska and Siberia, corresponding to large retreats of sea ice observed in these regions. Although there is large interannual and regional variability in the length of the melt season, the Arctic is experiencing an overall lengthening of the melt season at a rate of about 2 weeks decade(sup -1). In fact, all regions in the Arctic (except for the central Arctic) have statistically significant (at the 99% level or higher) longer melt seasons by greater than 1 week decade(sup -1). The central Arctic shows a statistically significant trend (at the 98% level) of 5.4 days decade(sup -1). In 2005 the Arctic experienced its longest melt season, corresponding with the least amount of sea ice since 1979 and the warmest temperatures since the 1880s. Overall, the length of the melt season is inversely correlated with the lack of sea ice seen in September north of Alaska and Siberia, with a mean correlation of -0.8.

Stroeve, Julienne; Markus, Thorsten; Meier, Walter N.; Miller, Jeff

2007-01-01

325

Purification of tantalum by plasma arc melting  

DOEpatents

Purification of tantalum by plasma arc melting. The level of oxygen and carbon impurities in tantalum was reduced by plasma arc melting the tantalum using a flowing plasma gas generated from a gas mixture of helium and hydrogen. The flowing plasma gases of the present invention were found to be superior to other known flowing plasma gases used for this purpose.

Dunn, Paul S. (Santa Fe, NM); Korzekwa, Deniece R. (Los Alamos, NM)

1999-01-01

326

Melt dumping in string stabilized ribbon growth  

DOEpatents

A method and apparatus for stabilizing the edge positions of a ribbon drawn from a melt includes the use of wettable strings drawn in parallel up through the melt surface, the ribbon being grown between the strings. A furnace and various features of the crucible used therein permit continuous automatic growth of flat ribbons without close temperature control or the need for visual inspection.

Sachs, Emanuel M. (42 Old Middlesex Rd., Belmont, MA 02178)

1986-12-09

327

Oxidation and melting of aluminum nanopowders.  

PubMed

Recently, nanometer-sized aluminum powders became available commercially, and their use as potential additives to propellants, explosives, and pyrotechnics has attracted significant interest. It has been suggested that very low melting temperatures are expected for nanosized aluminum powders and that such low melting temperatures could accelerate oxidation and trigger ignition much earlier than for regular, micron-sized aluminum powders. The objective of this work was to investigate experimentally the melting and oxidation behavior of nanosized aluminum powders. Powder samples with three different nominal sizes of 44, 80, and 121 nm were provided by Nanotechnologies Inc. The particle size distributions were measured using small-angle X-ray scattering. Melting was studied by differential scanning calorimetry where the powders were heated from room temperature to 750 degrees C in an argon environment. Thermogravimetric analysis was used to measure the mass increase indicative of oxidation while the powders were heated in an oxygen-argon gas mixture. The measured melting curves were compared to those computed using the experimental particle size distributions and thermodynamic models describing the melting temperature and enthalpy as functions of the particle size. The melting behavior predicted by different models correlated with the experimental observations only qualitatively. Characteristic stepwise oxidation was observed for all studied nanopowders. The observed oxidation behavior was well interpreted considering the recently established kinetics of oxidation of micron-sized aluminum powders. No correlation was found between the melting and oxidation of aluminum nanopowders. PMID:16805619

Trunov, Mikhaylo A; Umbrajkar, Swati M; Schoenitz, Mirko; Mang, Joseph T; Dreizin, Edward L

2006-07-01

328

Method and apparatus for melting glass batch  

DOEpatents

A glass melting system involving preheating, precalcining, and prefluxing of batch materials prior to injection into a glass furnace. The precursors are heated by convection rather than by radiation in present furnaces. Upon injection into the furnace, batch materials are intimately coated with molten flux so as to undergo or at least begin the process of dissolution reaction prior to entering the melt pool.

Fassbender, Alexander G. (Kennewick, WA); Walkup, Paul C. (Richland, WA); Mudge, Lyle K. (Richland, WA)

1988-01-01

329

Ice-Shelf Melting Around Antarctica  

NASA Astrophysics Data System (ADS)

We compare the volume flux divergence of Antarctic ice shelves in 2007 and 2008 with 1979 to 2010 surface accumulation and 2003 to 2008 thinning to determine their rates of melting and mass balance. Basal melt of 1325 ± 235 gigatons per year (Gt/year) exceeds a calving flux of 1089 ± 139 Gt/year, making ice-shelf melting the largest ablation process in Antarctica. The giant cold-cavity Ross, Filchner, and Ronne ice shelves covering two-thirds of the total ice-shelf area account for only 15% of net melting. Half of the meltwater comes from 10 small, warm-cavity Southeast Pacific ice shelves occupying 8% of the area. A similar high melt/area ratio is found for six East Antarctic ice shelves, implying undocumented strong ocean thermal forcing on their deep grounding lines.

Rignot, E.; Jacobs, S.; Mouginot, J.; Scheuchl, B.

2013-07-01

330

Melting Point, Density, and Reactivity of Metals  

NASA Astrophysics Data System (ADS)

The density and melting point of a metal, taken together, can give a useful qualitative guide to the chemical reactivity of the metal. A high density and high melting point indicate a low reactivity; conversely, low density and low melting point indicate high reactivity. The melting point is allied to the heat of sublimation; the density gives a guide to the magnitude of the ionization energy. These two thermodynamic energy quantities are common to the Born-Haber cycles for the standard electrode potential, enthalpy of formation of the oxide, and reaction with water, which are commonly accepted thermodynamic measures of reactivity. Kinetic effects also play a role, not easy to quantify. A sharp discontinuity in the general trend of either melting point or density in the middle of a long period points to anomalous or unusual chemical reactivity of the metal.

Laing, Michael

2001-08-01

331

Nanotexturing of surfaces to reduce melting point.  

SciTech Connect

This investigation examined the use of nano-patterned structures on Silicon-on-Insulator (SOI) material to reduce the bulk material melting point (1414 C). It has been found that sharp-tipped and other similar structures have a propensity to move to the lower energy states of spherical structures and as a result exhibit lower melting points than the bulk material. Such a reduction of the melting point would offer a number of interesting opportunities for bonding in microsystems packaging applications. Nano patterning process capabilities were developed to create the required structures for the investigation. One of the technical challenges of the project was understanding and creating the specialized conditions required to observe the melting and reshaping phenomena. Through systematic experimentation and review of the literature these conditions were determined and used to conduct phase change experiments. Melting temperatures as low as 1030 C were observed.

Garcia, Ernest J.; Zubia, David (University of Texas at El Paso El Paso, TX); Mireles, Jose (Universidad Aut%C3%94onoma de Ciudad Ju%C3%94arez Ciudad Ju%C3%94arez, Mexico); Marquez, Noel (University of Texas at El Paso El Paso, TX); Quinones, Stella (University of Texas at El Paso El Paso, TX)

2011-11-01

332

The contribution of glacier melt to streamflow  

SciTech Connect

Ongoing and projected future changes in glacier extent and water storage globally have lead to concerns about the implications for water supplies. However, the current magnitude of glacier contributions to river runoff is not well known, nor is the population at risk to future glacier changes. We estimate an upper bound on glacier melt contribution to seasonal streamflow by computing the energy balance of glaciers globally. Melt water quantities are computed as a fraction of total streamflow simulated using a hydrology model and the melt fraction is tracked down the stream network. In general, our estimates of the glacier melt contribution to streamflow are lower than previously published values. Nonetheless, we find that globally an estimated 225 (36) million people live in river basins where maximum seasonal glacier melt contributes at least 10% (25%) of streamflow, mostly in the High Asia region.

Schaner, Neil; Voisin, Nathalie; Nijssen, Bart; Lettenmaier, D. P.

2012-09-13

333

Melting in Monolayers : Hexatic and Fluid Phases  

E-print Network

There are strong evidences that the melting in two dimensions depends crucially on the form and range of the interaction potentials between particles. We study with Monte Carlo simulations the phase diagram and the melting of a monolayer of point-particles interacting with repulsive Inverse Power Law Interactions, $V(r)=Q^2(\\sigma/r)^n$ where $n$ can take any real positive value ($n$-OCP monolayer). As $n$ is varied from 0 to $\\infty$ (Hard Disks), including Coulomb ($n=1$) and Dipolar ($n=3$), melting occurs with different mechanisms and the overall picture permits to understand the diversity of mechanisms found experimentally or in computer simulations for 2D melting. The empirical transition curves for $n\\leq 3$ and the excellent qualitative and semi-quantitative agreements with the KTHNY theory found for the melting of $n$-OCP monolayers with $n\\leq 3$ are the main results of the present work.

Martial Mazars

2013-01-08

334

Melt Rate Improvement for DWPF MB3: Melt Rate Furnace Testing  

SciTech Connect

The Defense Waste Processing Facility (DWPF) would like to increase its canister production rate. The goal of this study is to improve the melt rate in DWPF specifically for Macrobatch 3. However, the knowledge gained may result in improved melting efficiencies translating to future DWPF macrobatches and in higher throughput for other Department of Energy's (DOE) melters. Increased melting efficiencies decrease overall operational costs by reducing the immobilization campaign time for a particular waste stream. For melt rate limited systems, a small increase in melting efficiency translates into significant hard dollar savings by reducing life cycle operational costs.

Stone, M.E.

2001-07-24

335

Aluminosilicate melts: structure, composition and temperature  

NASA Astrophysics Data System (ADS)

The anionic structure of aluminosilicate melts of intermediate degree of polymerization (NBO/T = 0.5) and with along the composition join (LS4-LA4) has been examined in-situ to 1480°C, and compared with recent data for melts along the analog composition join and with less polymerized melts along the join and O_5. With , the anionic equilibrium, (1) , adequately describes the structure. With , a second expression, (2) , is required because an additional structural unit, Q1, is stabilized in the melts. The enthalpy, , of reaction (1) increases from - 36 +/-4 kJ/mol in the absence of aluminum to 34+/- 5 kJ/mol at and 64 +/- 4 kJ/mol at Al/(Al + Si) = 0.45. Similar trends are reported for other alkali aluminosilicate melts. Least-squares fitting of abundance of structural units as a function of temperature and bulk composition has been conducted. The unit abundance is dominantly a function of temperature, Al/(Al +Si), and bulk melt polymerization. Configurational entropy and heat capacity of mixing of melts above their glass transition temperatures have been calculated with the aid of the least-squares fitted equations. The values of these parameters indicate that as the ionization potential of the metal cations increases, configurational heat capacity of alkali aluminosilicate melts becomes temperature dependent. As a result, transport properties (viscosity, diffusivity, and conductivity) of such melts will not show Arrhenian behavior even in the high-temperature range. Further, discontinuous changes in entropy and heat capacity of mixing results from temperature-induced changes in types of structural units in the melts. Such discontinuous changes would also be reflected in discontinuous changes of temperature-dependent transport properties.

Mysen, B.

336

Rheology of Melt-bearing Crustal Rocks  

NASA Astrophysics Data System (ADS)

A review and reinterpretation of previous experimental data on the deformation of melt-bearing crustal rocks (Rosenberg and Handy, 2005) revealed that the relationship of aggregate strength to melt fraction is non-linear, even if plotted on a linear ordinate and abscissa. At melt fractions, ? 0.07, the dependence of aggregate strength on ? is significantly greater than at ? > 0.07. This melt fraction (?= 0.07) marks the transition from a significant increase in the proportion of melt-bearing grain boundaries up to this point to a minor increase thereafter. Therefore, we suggest that the increase of melt-interconnectivity causes the dramatic strength drop between the solidus and a melt fraction of 0.07. A second strength drop occurs at higher melt fractions and corresponds to the breakdown of the solid (crystal) framework, corresponding to the well-known "rheologically critical melt percentage" (RCMP; Arzi, 1978). Although the strength drop at the RCMP is about 4 orders of magnitude, the absolute value of this drop is small compared to the absolute strength of the unmelted aggregate, rendering the RCMP invisible in a linear aggregate strength vs. melt fraction diagram. Predicting the rheological properties and thresholds of melt-bearing crust on the basis of the results and interpretations above is very difficult, because the rheological data base was obtained from experiments performed at undrained conditions in the brittle field. These conditions are unlikely to represent the flow of partially melted crust. The measured strength of most of the experimentally deformed, partially-melted samples corresponds to their maximum differential stress, before the onset of brittle failure, not to their viscous strength during "ductile" (viscous) flow. To overcome these problems, we extrapolated a theoretically-derived flow law for partially melted granite deforming by diffusion-accommodated grain-boundary sliding (Paterson, 2001) and an experimentally-derived flow law for quartz deforming in the dislocation creep regime in the presence of 1-2 % of melt (Gleason and Tullis, 1995). In addition, we compared these data with deformation experiments on olivine plus basalt melt, also conducted in the ductile (viscous) field (Hirth and Kohlstedt, 2003). All these data show a dramatic decrease in viscosity for melt fractions < 0.06. Therefore, they are consistent with the aforementioned results of experimentally deformed granite in the brittle field. Extrapolation of these results to natural conditions suggests that localisation of deformation should effectively coincide with the onset of melting, or with very small melt fractions (0.06-0.07), which may not always be detected in the field. References: Arzi, A. 1978. Tectonophysics, 44: 173-184. Hirth, G. and D. Kohlstedt. 2003. Geophysical Monograph, 138: 83-105. Gleason, G.C. and Tullis, J., 1995. Tectonophysics, 247: 1-23. Paterson, M.S. 2001. Tectonophysics, 335: 51-61. Rosenberg, C.L., and M.R. Handy. 2005. Journal of Metamorphic Geology, 23:19-28.

Rosenberg, C. L.; Medvedev, S.; Handy, M. R.

2006-12-01

337

Core formation, evolution, and convection: A geophysical model  

NASA Technical Reports Server (NTRS)

A model is proposed for the formation and evolution of the Earth's core which provides an adequate energy source for maintaining the geodynamo. A modified inhomogeneous accretion model is proposed which leads to initial iron and refractory enrichment at the center of the planet. The probable heat source for melting of the core is the decay of Al. The refractory material is emplaced irregularly in the lowermost mantle with uranium and thorium serving as a long lived heat source. Fluid motions in the core are driven by the differential heating from above and the resulting cyclonic motions may be the source of the geodynamo.

Ruff, L.; Anderson, D. L.

1978-01-01

338

Core formation, evolution, and convection - A geophysical model  

NASA Technical Reports Server (NTRS)

A model for the formation and evolution of the earth's core, which provides an adequate energy source for maintaining the geodynamo, is proposed. A modified inhomogeneous accretion model is proposed which leads to initial iron and refractory enrichment at the center of the planet. The probable heat source for melting of the core is the decay of Al-26. The refractory material is emplaced irregularly in the lowermost mantle with uranium and thorium serving as a long-lived heat source. Fluid motions in the core are driven by the differential heating from above and the resulting cyclonic motions may be the source of the geodynamo.

Ruff, L.; Anderson, D. L.

1980-01-01

339

Si and O partitioning between core metal and lower mantle minerals during core formation  

NASA Astrophysics Data System (ADS)

In addition to Fe and Ni, the Earth’s core contains light alloying elements (e.g., H, C, O, Si, and/or S) in order to explain the 10% core density deficit (e.g., Birch, 1964, JGR). Experimental data on the partitioning behavior of siderophile elements such as Ni and Co between liquid Fe and mantle minerals indicate that equilibration between core-forming metal and a silicate magma ocean likely occurred at lower-mantle pressures (e.g., Li and Agee, 1996 Nature). If core-mantle differentiation has occurred under such conditions, significant quantities of O or Si could have entered the core. At these conditions the nature of the dominant light element in the core will depend strongly on the oxygen fugacity at which equilibration occurred. High pressure experiments were carried out at 25 GPa and 2400-2950 K using a Kawai-type multi-anvil apparatus in order to investigate the partitioning of Si and O between liquid Fe and (Mg,Fe)SiO3 perovskite (Pv), silicate melt, and (Mg,Fe)O ferropericlace (Fp). Starting materials consisting of metallic Fe (+-Si) and olivine (Fo70-95) were contained in single-crystal MgO capsules. Over the oxygen fugacity range IW-0.5 to -3, the Si molar partition coefficient D* (= [Si]metal /[Si]silicate) between metal and Pv increases linearly with decreasing oxygen fugacity at a fixed given temperature. The partition coefficient between metal and silicate melt is of a similar magnitude but is less dependent on the oxygen fugacity. The obtained oxygen distribution coefficient Kd (= [Fe]metal[O]metal /[FeO]Fp) is in agreement with that determined in the Fe-Fp binary system (Asahara et al., 2007 EPSL) below the silicate liquidus temperature. In contrast, a correlation between the O partitioning and Si concentration in Fe is observed above 2700 K where liquid metal coexists with silicate melt + Fp. With an increasing concentration of Si in the liquid metal, O partitioning into Fp is strongly enhanced. Five atomic% Si in the metal reduces the metal-silicate O partition coefficient by about 1 order magnitude. Near the base of a deep magma ocean where pressures exceed 20 GPa, liquid metal could have coexisted with silicate melt, Pv, and Fp. Our results show that Si would readily partitioned into core-forming metal from both perovskite and silicate liquid at a relevant oxygen fugacity (e.g., IW-2). Simultaneously, the Si solubility would hinder the dissolution of O in the liquid metal. This implies that the presence of Si in liquid metal must be included in models of O partitioning.

Nakajima, Y.; Frost, D. J.; Rubie, D. C.

2010-12-01

340

OECD MCCI project Melt Eruption Test (MET) design report, Rev. 2. April 15, 2003.  

SciTech Connect

The Melt Attack and Coolability Experiments (MACE) program at Argonne National Laboratory addressed the issue of the ability of water to cool and thermally stabilize a molten core-concrete interaction when the reactants are flooded from above. These tests provided data regarding the nature of corium interactions with concrete, the heat transfer rates from the melt to the overlying water pool, and the role of noncondensable gases in the mixing processes that contribute to melt quenching. The Melt Coolability and Concrete Interaction (MCCI) program is pursuing separate effect tests to examine the viability of the melt coolability mechanisms identified as part of the MACE program. These mechanisms include bulk cooling, water ingression, volcanic eruptions, and crust breach. At the second PRG meeting held at ANL on 22-23 October 2002, a preliminary design1 for a separate effects test to investigate the melt eruption cooling mechanism was presented for PRG review. At this meeting, NUPEC made several recommendations on the experiment approach aimed at optimizing the chances of achieving a floating crust boundary condition in this test. The principal recommendation was to incorporate a mortar sidewall liner into the test design, since data from the COTELS experiment program indicates that corium does not form a strong mechanical bond with this material. Other recommendations included: (i) reduction of the electrode elevation to well below the melt upper surface elevation (since the crust may bond to these solid surfaces), and (ii) favorably taper the mortar liner to facilitate crust detachment and relocation during the experiment. Finally, as a precursor to implementing these modifications, the PRG recommended the development of a design for a small-scale scoping test intended to verify the ability of the mortar liner to preclude formation of an anchored bridge crust under core-concrete interaction conditions. This revised Melt Eruption Test (MET) plan is intended to satisfy these PRG recommendations. Specifically, the revised plan focuses on providing data on the extent of crust growth and melt eruptions as a function of gas sparging rate under well-controlled experiment conditions, including a floating crust boundary condition. The overall objective of MET is to determine to what extent core debris is rendered coolable by eruptive-type processes that breach the crust that rests upon the melt. The specific objectives of this test are as follows: (1) Evaluate the augmentation in surface heat flux during periods of melt eruption; (2) Evaluate the melt entrainment coefficient from the heat flux and gas flow rate data for input into models that calculate ex-vessel debris coolability; (3) Characterize the morphology and coolability of debris resulting from eruptive processes that transport melt into overlying water; and (4) Discriminate between periods when eruptions take the form of particle ejections into overlying water, leading to a porous particle bed, and single-phase extrusions, which lead to volcano-type structures.

Farmer, M. T.; Lomperski, S.; Kilsdonk, D. J.; Aeschlimann, R. W.; Basu, S. (Nuclear Engineering Division); (NRC)

2011-05-23

341

Terrestrial impact melt rocks and glasses  

NASA Astrophysics Data System (ADS)

The effects of meteorite and comet impact on Earth are rock brecciation, the formation of shock metamorphic features, rock melting, and the formation of impact structures, i.e. simple craters, complex craters, and multi-ring basins. Large events, such as the 65-Ma Chicxulub impact, are believed to have had catastrophic environmental effects that profoundly influenced the development of life on Earth. In this review, an attempt is made to summarize some of the voluminous literature on impact melting, one important aspect of planetary impact, provide some comments on this process, and to make suggestions for future research. The products of impact melting are glasses, impact melt rocks, and pseudotachylites. Our treatise deals mainly with the geological setting, petrography, and major-element chemistry of melt rocks and glasses. Impact glasses, in several petrographic aspects, are similar to volcanic glasses, but they are associated with shock metamorphosed mineral and rock fragments and, in places, with siderophile element anomalies suggestive of meteoritic contamination. They are found in allogenic breccia deposits within (fall-back 'suevite') and outside (fall-out 'suevite') impact craters and, as spherules, in distal ejecta. Large events, such as the K/T boundary Chicxulub impact, are responsible for the formation of worldwide ejecta horizons which are associated with siderophile element anomalies and shock metamorphosed mineral and rock debris. Impact glasses have a bulk chemical composition that is homogeneous but exemptions to this rule are common. On a microscopic scale, however, impact glasses are commonly strikingly heterogeneous. Tektites are glasses ejected from craters over large distances. They are characterized by very low water and volatile contents and element abundances and ratios that are evidence that tektites formed by melting of upper crustal, sedimentary rocks. Four tektite strewn-fields are known, three of which can be tied to specific impact craters. Impact melt rocks form sheets, lenses, and dike-like bodies within or beneath allogenic fallback breccia deposits in the impact crater and possibly on crater terraces and flanks. Dikes of impact melt rocks also intrude the rocks of the crater floor. They commonly contain shock metamorphosed target rock and mineral fragments in various stages of assimilation and are glassy or fine- to coarse-grained. Chemically, they are strikingly homogeneous, but as with impact glasses, exemptions to this rule do exist. Large and thick melt bodies, such as the Sudbury Igneous Complex (SIC), are differentiated or may represent a combination of impact melt rocks sensu-strictu and impact-triggered, deep-crustal melts. A concerted, multidisciplinary approach to future research on impact melting and on other aspects of meteorite and comet impact is advocated. Impact models are models only and uncritical reliance on their validity will not lead to a better understanding of impact processes—especially of melting, excavation, and deposition of allogenic breccias and the spatial position of breccias in relation to sheets and lenses of melt rocks within the crater. Impact-triggered pressure-release melting of target rocks beneath the excavation cavity may be responsible for the existence of melt rocks beneath the impact melt rocks sensu-strictu. This controversial idea needs to be tested by a re-evaluation of existing data and models, be they based on field or laboratory research. Only a relatively small number of terrestrial impact structures has been investigated in sufficient detail as it relates to geological and geophysical mapping. In this review, we summarize observations made on impact melt rocks and impact glasses in a number of North American (Brent, Haughton, Manicouagan, New Quebec, Sudbury, Wanapitei, all in Canada), Asian (Popigai, Russia; Zhamanshin, Kazakhstan), two South African structures (Morokweng and Vredefort), the Henbury crater field of Australia, and one European crater (Ries, Germany). Our tables listing major-element chemical compositions of impact

Dressler, B. O.; Reimold, W. U.

2001-12-01

342

Global distribution of lunar impact melt flows  

NASA Astrophysics Data System (ADS)

In this study, we analyzed the distribution and properties of 146 craters with impact melt deposits exterior to their rims. Many of these craters were only recently discovered due to their unusual radar properties in the near-global Mini-RF data set. We find that most craters with exterior deposits of impact melt are small, ?20 km, and that the smallest craters have the longest melt flows relative to their size. In addition, exterior deposits of impact melt are more common in the highlands than the mare. This may be the result of differing target properties in the highlands and mare, the difference in titanium content, or the greater variation of topography in the highlands. We find that 80% of complex craters and 60% of simple craters have melt directions that are coincident or nearly coincident with the lowest point in their rim, implying that pre-existing topography plays a dominant role in melt emplacement. This is likely due to movement during crater modification (complex craters) or breached crater rims (simple craters). We also find that impact melt flows have very high circular polarization ratios compared to other features on the Moon. This suggests that their surfaces are some of the roughest material on the Moon at the centimeter to decimeter scale, even though they appear smooth at the meter scale.

Neish, C. D.; Madden, J.; Carter, L. M.; Hawke, B. R.; Giguere, T.; Bray, V. J.; Osinski, G. R.; Cahill, J. T. S.

2014-09-01

343

Generation of liquid water on Mars through the melting of a dusty snowpack  

USGS Publications Warehouse

The possibility that snowmelt could have provided liquid water for valley network formation early in the history of Mars is investigated using an optical-thermal model developed for dusty snowpacks at temperate latitudes. The heating of the postulated snow is assumed to be driven primarily by the absorption of solar radiation during clear sky conditions. Radiative heating rates are predicted as a function of depth and shown to be sensitive to the dust concentration and the size of the ice grains while the thermal conductivity is controlled by temperature, atmospheric pressure, and bulk density. Rates of metamorphism indicate that fresh fine-grained snow on Mars would evolve into moderately coarse snow during a single summer season. Results from global climate models are used to constrain the mean-annual surface temperatures for snow and the atmospheric exchange terms in the surface energy balance. Mean-annual temperatures within Martian snowpacks fail to reach the melting point for all atmospheric pressures below 1000 mbar despite a predicted temperature enhancement beneath the surface of the snowpacks. When seasonal and diurnal variations in the incident solar flux are included in the model, melting occurs at midday during the summer for a wide range of snow types and atmospheric pressures if the dust levels in the snow exceed 100 ppmw (parts per million by weight). The optimum dust concentration appears to be about 1000 ppmw. With this dust load, melting can occur in the upper few centimeters of a dense coarse-grained snow at atmospheric pressures as low as 7 mbar. Snowpack thickness and the thermal conductivity of the underlying substrate determine whether the generated snow-melt can penetrate to the snowpack base, survive basal ice formation, and subsequently become available for runoff. Under favorable conditions, liquid water becomes available for runoff at atmospheric pressures as low as 30 to 100 mbar if the substrate is composed of regolith, as is expected in the ancient cratered terrain of Mars. ?? 1987.

Clow, G.D.

1987-01-01

344

Water diffusion in phonolite melts  

NASA Astrophysics Data System (ADS)

We report an experimental study of total water diffusion (irrespective of water speciation) in two different phonolite melts, which are representative of Montaña Blanca, Tenerife, Spain (MBP) and Laacher See, East Eifel, Germany (LSP-II). Both phonolites have Na-rich compositions, but differ in their alumina saturation index, with MBP being peralkaline and LSP-II being slightly peraluminous. Diffusion couple experiments for MBP were performed at 200-250 MPa in the temperature range of 800-1050 °C and water contents between 1 and 6.5 wt.%. Due to higher liquidus temperatures of LSP-II, the accessible temperature and water concentration range was reduced to 875-1050 °C and 3-6.5 wt.% water. All experiments were performed in rapid quench cold-seal pressure vessels, which enabled rapid heating and quenching of the samples within seconds. Compared to the run durations of 30-90 min, these short heating and cooling periods can be neglected and no corrections needed to be applied for the calculation of the diffusion coefficients. Water diffusion profiles were determined by FT-IR micro-spectroscopy on doubly polished glass sections and the diffusion coefficients were determined by Boltzmann-Matano analysis. Water diffusion increases with increasing water content and temperature and follows the empirical relations:

Schmidt, Burkhard C.; Blum-Oeste, Nils; Flagmeier, Jens

2013-04-01

345

Physics of deep plume melting: komatiitic melt accumulation and segregation in the transition zone  

NASA Astrophysics Data System (ADS)

Komatiites are assumed to be produced in very hot mantle upwellings or plumes. Under such conditions, melting will take place deep within the upper mantle or even within or below the mantle transition zone. Due to its compressibility at such pressures, melt has a higher density than olivine. Whether it would remain buoyant with respect to a peridotitic mantle both above and below the olivine-wadsleyite phase boundary because of the presence of denser garnet remains an open issue, particularly in view of recent X-ray refraction data on molten basalts by Sanloup et al. (2013). We studied the physics of melting and melt segregation within hot upwelling mantle passing through the transition zone, with particular emphasis on the effect of depth-dependent density contrasts between melt and the ambient mantle. Assuming a 1D plume, we solved the two-phase flow equations of the melt-matrix system accounting for matrix compaction and porosity-dependent shear and bulk viscosity. We assumed a constant ascent velocity leading to a constant rate of melt generation. In a first model series, the level of neutral buoyancy zneutral is assumed to lie above the depth of onset of melting, i.e. there exists a region where dense melt may lag behind the solid phases within the rising plume. Depending on two non-dimensional numbers (accumulation number Ac, compaction resistance number Cr) we find four regimes: 1) time-dependent melt accumulation in standing and broadening porosity waves that scale with the compaction length, 2) steady-state weak melt accumulation near zneutral, 3) no melt accumulation due to small density contrast, 4) no melt accumulation due to high matrix viscosity. In regime 4 the high mantle viscosity prevents the opening of pore space and the accumulation of melt. In a second series, the rising mantle crosses the olivine-wadsleyite phase boundary, which imposes a jump in density contrast between melt and ambient mantle. In this case, a sharp melt fraction contrast develops and a large melt fraction accumulates immediately above the phase boundary. In a third set of models, a hot 1D plume head is assumed to move through the transition zone. The top of the plume head remains below the solidus temperature and the melt density is always less than that of the ambient mantle. In this case melt percolates upwards and accumulates near the top of the plume head within a very thin layer, reaching up to 100% melt fraction. These models show 1) that not only melt density, but also porosity dependent matrix viscosity controls the melt ascent or accumulation, 2) that there are parameter ranges and physical conditions which may lead to the accumulation of very large melt fractions (> degree of melting), 3) that in spite of melt being denser than olivine at some depths, in general these melts escape these regions and continue to percolate upward faster than the rising mantle.

Schmeling, Harro; Arndt, Nick; Kohl, Svenja

2014-05-01

346

Postulated mechanisms of resistance of B-cell non-Hodgkin lymphoma to rituximab treatment regimens: strategies to overcome resistance.  

PubMed

Antibody-mediated immunotherapy has gained significant momentum since 1997 when the US Food and Drug Administration approved the first monoclonal antibody (mAb) for the treatment of B-cell non-Hodgkin lymphoma (B-NHL), namely, rituximab (chimeric anti-CD20 mAb). Subsequently, more than 20 approved mAbs have been in use clinically for the treatment of various cancers and several non-cancer-related diseases. Further, the combination treatment of mAbs with chemotherapy, immunotherapy, proteaosome inhibitors, and other inhibitors has resulted in synergistic anti-tumor activity with significant objective clinical responses. Despite their successful clinical use, the underlying mechanisms of rituximab's in vivo activities remain elusive. Further, it is not clear why a subset of patients is initially unresponsive and many responding patients become refractory and resistant to further treatments; hence, the underlying mechanisms of resistance are not known, Attempts have been made to develop model systems to investigate resistance to mAb therapy with the hope to apply the findings in both the generation of new therapeutics and in their use as new prognostic biomarkers. This review focuses on the development of resistance to rituximab treatments and discusses possible underlying mechanisms of action, postulated mechanisms of resistance in model systems, and suggested means to overcome resistance. Several prior reviews on the subject of rituximab resistance have been published and the present review both complements as well as adds new topics of relevance. PMID:25440611

Bonavida, Benjamin

2014-10-01

347

Melt migration through Io's convecting mantle  

NASA Astrophysics Data System (ADS)

The extensive volcanism occurring on the surface of Io suggests that its interior must contain at least some partial melt. Unlike Earth, Io cannot lose its internal heat through convection alone [1]. Instead, melt moving through the solid mantle helps remove heat from Io's interior by carrying its latent heat towards the surface as it buoyantly ascends through the mantle. We investigate this process by considering melt migration in a column of rock rising through the mantle between downwelling plumes. Convective scaling laws provide the upwelling velocity and the temperature of the rising mantle. Properties of melt migration in this rising mantle are calculated using porous flow equations and an equation for the conservation of energy which includes latent heat consumption, heat advection and heat conduction [2]. This combination of convective scaling laws and porous flow laws allows us to self-consistently determine the radial melt fraction profile in Io's interior, the average melt fraction in Io's interior and the heat flux due to advection of melt. The average melt fraction can be compared to the melt fraction constraints calculated by [3] from Galileo magnetometer measurements. The surface heat flux calculations can be compared to the value of Io's observed surface heat flux which ranges with observation from 1.5-4 W m-2 [4]. [1] Moore W. B. (2003) J. Geophys. Res., 108, E8, 15-1. [2] Hewitt I. J. and Fowler A. C. (2008) Proc. R. Soc. A., 464, 2467-2491. [3] Khurana K. K. et al. (2011) Science, 332, 1186-1189. [4] Moore, W. B. et al. (2007) In: Io After Galileo, Springer-Praxis, 89-108.

Elder, C. M.; Showman, A. P.

2013-12-01

348

Melting of a finite-sized two-dimensional colloidal crystal  

NASA Astrophysics Data System (ADS)

We have studied the melting process of a finite-sized two-dimensional colloidal crystal by video microscopy. The local area fraction ? and the local hexatic orientational order parameter ?6 have been evaluated for respective Voronoi cells in the crystal. The histogram of ? exhibits a peak and the peak ? continuously decreases with the time elapsed. The histogram of |?6| shows an abrupt broadening for ? <0.65. This critical value of ? is the transition point between the hexatic and dense liquid phases in finite crystal. We have also evaluated ? and |?6| as a function of the distance from the center of the crystal r. ? (r) is almost constant within the crystal and monotonously decreases with the time elapsed. |?6(r)| gradually decreases with r but there is the core with |?6|=1 at earlier time stage. The temporal change of the average ? within the crystal is qualitatively explained by the slow diffusion of the particles situated at the crystal edge. The steric repulsion between the particles within the crystal enhances the expansion rate of the crystal edge. Overall melting behavior is same in the crystals with different sizes. We have also studied the melting of a finite-sized crystal composed of soft-core particles by Brownian dynamics simulation and verified the finite-size effect on the melting process. The simulated behavior is qualitatively in good agreement with the experimental results.

Tanaka, Sayuri; Oki, Yuma; Kimura, Yasuyuki

2014-05-01

349

Experimental alteration of artificial and natural impact melt rock from the Chesapeake Bay impact structure  

USGS Publications Warehouse

The alteration or transformation of impact melt rock to clay minerals, particularly smectite, has been recognized in several impact structures (e.g., Ries, Chicxulub, Mj??lnir). We studied the experimental alteration of two natural impact melt rocks from suevite clasts that were recovered from drill cores into the Chesapeake Bay impact structure and two synthetic glasses. These experiments were conducted at hydrothermal temperature (265 ??C) in order to reproduce conditions found in meltbearing deposits in the first thousand years after deposition. The experimental results were compared to geochemical modeling (PHREEQC) of the same alteration and to original mineral assemblages in the natural melt rock samples. In the alteration experiments, clay minerals formed on the surfaces of the melt particles and as fine-grained suspended material. Authigenic expanding clay minerals (saponite and Ca-smectite) and vermiculite/chlorite (clinochlore) were identified in addition to analcime. Ferripyrophyllite was formed in three of four experiments. Comparable minerals were predicted in the PHREEQC modeling. A comparison between the phases formed in our experiments and those in the cores suggests that the natural alteration occurred under hydrothermal conditions similar to those reproduced in the experiment. ?? 2009 The Geological Society of America.

Declercq, J.; Dypvik, H.; Aagaard, P.; Jahren, J.; Ferrell, R.E., Jr.; Horton, J. Wright, Jr.

2009-01-01

350

Rapidly solidified titanium alloys by melt overflow  

NASA Technical Reports Server (NTRS)

A pilot plant scale furnace was designed and constructed for casting titanium alloy strips. The furnace combines plasma arc skull melting techniques with melt overflow rapid solidification technology. A mathematical model of the melting and casting process was developed. The furnace cast strip of a suitable length and width for use with honeycomb structures. Titanium alloys Ti-6Al-4V and Ti-14Al-21 Nb were successfully cast into strips. The strips were evaluated by optical metallography, microhardness measurements, chemical analysis, and cold rolling.

Gaspar, Thomas A.; Bruce, Thomas J., Jr.; Hackman, Lloyd E.; Brasmer, Susan E.; Dantzig, Jonathan A.; Baeslack, William A., III

1989-01-01

351

Genotyping by high-resolution melting analysis.  

PubMed

High-resolution melting (HRM) analysis is a simple, closed tube, post-PCR method used to identify genetic variation. The method is highly sensitive and can discriminate DNA sequence variants based on length (such as insertions or deletions), composition (such as single nucleotide polymorphisms, i.e., SNP) or strand complementarity (such as heterozygous or homozygous material). The technique involves PCR amplification of a target sequence in the presence of a fluorescent double-stranded DNA (dsDNA) binding dye, melting of the fluorescent amplicons, and subsequent interpretation of melt curve profiles. Here, we describe general considerations for assay design, PCR amplification, and HRM analysis. PMID:24816659

Tucker, Elise J; Huynh, Bao Lam

2014-01-01

352

Force induced melting of the constrained DNA  

E-print Network

We develop a simple model to study the effects of an applied force on the melting of a double stranded DNA (dsDNA). Using this model, we could study the stretching, unzipping, rupture and slippage like transition in a dsDNA. We show that in absence of an applied force, the melting temperature and the melting profile of dsDNA strongly depend on the constrained imposed on the ends of dsDNA. The nature of the phase boundary which separates the zipped and the open state for the shearing like transition is remarkably different than the DNA unzipping

Amit Raj Singh; D. Giri; S. Kumar

2009-12-12

353

Electrohydrodynamic quenching in polymer melt electrospinning  

NASA Astrophysics Data System (ADS)

Infrared thermal measurements on polymer melt jets in electrospinning have revealed rapid quenching by ambient air, an order of magnitude faster than predicted by the classical Kase and Matsuo correlation. This drastic heat transfer enhancement can be linked to electrohydrodynamic (EHD) effects. Analysis of EHD-driven air flow was performed and included into a comprehensive model for polymer melt electrospinning. The analysis was validated by excellent agreement of both predicted jet radius and temperature profiles with experimental results for electrospinning of Nylon-6 (N6), polypropylene (PP), and polylactic acid (PLA) melts. Based on this analysis, several methods that can be used to inhibit or enhance the quenching are described.

Zhmayev, Eduard; Cho, Daehwan; Lak Joo, Yong

2011-07-01

354

Core-core and core-valence correlation  

NASA Technical Reports Server (NTRS)

The effect of (1s) core correlation on properties and energy separations was analyzed using full configuration-interaction (FCI) calculations. The Be 1 S - 1 P, the C 3 P - 5 S and CH+ 1 Sigma + or - 1 Pi separations, and CH+ spectroscopic constants, dipole moment and 1 Sigma + - 1 Pi transition dipole moment were studied. The results of the FCI calculations are compared to those obtained using approximate methods. In addition, the generation of atomic natural orbital (ANO) basis sets, as a method for contracting a primitive basis set for both valence and core correlation, is discussed. When both core-core and core-valence correlation are included in the calculation, no suitable truncated CI approach consistently reproduces the FCI, and contraction of the basis set is very difficult. If the (nearly constant) core-core correlation is eliminated, and only the core-valence correlation is included, CASSCF/MRCI approached reproduce the FCI results and basis set contraction is significantly easier.

Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.

1988-01-01

355

Geochemical Comparison of Four Cores from the Manson Impact Structure  

NASA Technical Reports Server (NTRS)

Concentrations of 33 elements were determined in relatively unaltered, matrix-rich samples of impact breccia at approximately 3-m-depth intervals in the M-1 core from the Manson impact structure, Iowa. In addition, 46 matrix-rich samples from visibly altered regions of the M-7, M-8, and M-10 cores were studied, along with 42 small clasts from all four cores. Major element compositions were determined for a subset of impact breccias from the M-1 core, including matrix-rich impact-melt breccia. Major- and trace-element compositions were also determined for a suite of likely target rocks. In the M-1 core, different breccia units identified from lithologic examination of cores are compositionally distinct. There is a sharp compositional discontinuity at the boundary between the Keweenawan-shale-clast breccia and the underlying unit of impact-melt breccia (IMB) for most elements, suggesting minimal physical mixing between the two units during emplacement. Samples from the 40-m-thick IMB (M-1) are all similar to each other in composition, although there are slight increases in concentration with depth for those elements that have high concentrations in the underlying fragmental-matrix suevite breccia (SB) (e.g., Na, Ca, Fe, Sc), presumably as a result of greater clast proportions at the bottom margin of the unit of impact-melt breccia. The high degree of compositional similarity we observe in the impact-melt breccias supports the interpretation that the matrix of this unit represents impact melt. That our analyses show such compositional similarity results in part from our technique for sampling these breccias: for each sample we analyzed a few small fragments (total mass: approximately 200 mg) selected to be relatively free of large clasts and visible signs of alteration instead of subsamples of powders prepared from a large mass of breccia. The mean composition of the matrix-rich part of impact-melt breccia from the M-1 core can be modeled as a mixture of approximately 35% shale and siltstone (Proterozoic "Red Clastics"), 23% granite, 40% hornblende-biotite gneiss, and a small component (less than 2%) of mafic-dike rocks.

Korotev, Randy L.; Rockow, Kaylynn M.; Jolliff, Bradley L.; Haskin, Larry A.; McCarville, Peter; Crossey, Laura J.

1996-01-01

356

Modification of Melt-Spun Isotactic Polypropylene and Poly(lactic acid) Bicomponent Filaments with a Premade Block Copolymer  

E-print Network

Modification of Melt-Spun Isotactic Polypropylene and Poly(lactic acid) Bicomponent Filaments copoly- mer to core-sheath filaments consisting of isotactic poly- propylene (iPP) and poly(lactic acid. Polylactide, or poly(lactic acid), (PLA) is produced from lactide monomer, which is obtained from agricultural

Khan, Saad A.

357

Models and correlations of the DEBRIS Late-Phase Melt Progression Model  

SciTech Connect

The DEBRIS Late Phase Melt Progression Model is an assembly of models, embodied in a computer code, which is designed to treat late-phase melt progression in dry rubble (or debris) regions that can form as a consequence of a severe core uncover accident in a commercial light water nuclear reactor. The approach is fully two-dimensional, and incorporates a porous medium modeling framework together with conservation and constitutive relationships to simulate the time-dependent evolution of such regions as various physical processes act upon the materials. The objective of the code is to accurately model these processes so that the late-phase melt progression that would occur in different hypothetical severe nuclear reactor accidents can be better understood and characterized. In this report the models and correlations incorporated and used within the current version of DEBRIS are described. These include the global conservation equations solved, heat transfer and fission heating models, melting and refreezing models (including material interactions), liquid and solid relocation models, gas flow and pressure field models, and the temperature and compositionally dependent material properties employed. The specific models described here have been used in the experiment design analysis of the Phebus FPT-4 debris-bed fission-product release experiment. An earlier DEBRIS code version was used to analyze the MP-1 and MP-2 late-phase melt progression experiments conducted at Sandia National Laboratories for the US Nuclear Regulatory Commission.

Schmidt, R.C.; Gasser, R.D. [Sandia National Labs., Albuquerque, NM (United States). Reactor Safety Experiments Dept.

1997-09-01

358

Continental heat anomalies and the extreme melting of the Greenland ice surface in 2012 and 1889  

NASA Astrophysics Data System (ADS)

Recent decades have seen increased melting of the Greenland ice sheet. On 11 July 2012, nearly the entire surface of the ice sheet melted; such rare events last occurred in 1889 and, prior to that, during the Medieval Climate Anomaly. Studies of the 2012 event associated the presence of a thin, warm elevated liquid cloud layer with surface temperatures rising above the melting point at Summit Station, some 3212 m above sea level. Here we explore other potential factors in July 2012 associated with this unusual melting. These include (1) warm air originating from a record North American heat wave, (2) transitions in the Arctic Oscillation, (3) transport of water vapor via an Atmospheric River over the Atlantic to Greenland, and (4) the presence of warm ocean waters south of Greenland. For the 1889 episode, the Twentieth Century Reanalysis and historical records showed similar factors at work. However, markers of biomass burning were evident in ice cores from 1889 which may reflect another possible factor in these rare events. We suggest that extreme Greenland summer melt episodes, such as those recorded recently and in the late Holocene, could have involved a similar combination of slow climate processes, including prolonged North American droughts/heat waves and North Atlantic warm oceanic temperature anomalies, together with fast processes, such as excursions of the Arctic Oscillation, and transport of warm, humid air in Atmospheric Rivers to Greenland. It is the fast processes that underlie the rarity of such events and influence their predictability.

Neff, William; Compo, Gilbert P.; Martin Ralph, F.; Shupe, Matthew D.

2014-06-01

359

On the thermal and magnetic histories of Earth and Venus: Influences of melting, radioactivity, and conductivity  

NASA Astrophysics Data System (ADS)

The study of the thermal evolution of Earth's interior is uncertain and controversial in many respects, from the interpretation of petrologic observations used to infer the temperature and dynamics of the interior, to the physics and material properties governing heat transport. The thermal history of Venus is even more uncertain, but the lack of a dynamo at present in an otherwise similar planet may provide additional constraints on terrestrial planet evolution. In this paper a one dimensional thermal history model is derived that includes heat loss due to mantle melt eruption at the surface to explore its influence on the thermal and magnetic history of Earth and Venus. We show that the thermal catastrophe of Earth's mantle, which occurs for a present day Urey ratio of 1/3 and convective heat loss exponent of ?=1/3, can be avoided by assuming a rather high core heat flow of ?15 TW. This core heat flow also avoids the new core paradox by allowing for the geodynamo to be thermally powered prior to inner core growth for core thermal conductivities as high as 130 Wm K. Dynamo regime diagrams demonstrate that the mantle melt eruption rate has a minor effect on the history of mobile lid planets due to the efficiency of plate tectonic convective heat loss. However, if Earth were in a stagnant lid regime prior to 2.5 Ga, as has been proposed, then at least ?5% of mantle melt is required to erupt in order to thermally power the paleodynamo at that time. Dynamo regime diagrams for stagnant lid Venus models indicate that more than half of the melt generated in the mantle is required to erupt in order to overcome the insulation imposed by the stagnant lid and drive a dynamo. This implies that with an Earth-like mantle radioactivity the Venusian dynamo shut down ?0.3 Ga for an eruption efficiency of 50%, and ?3 Ga for an eruption efficiency of zero. Consequently, a stagnant lid alone does not prevent a core dynamo if melting of the upper mantle provides a substantial mantle heat sink.

Driscoll, P.; Bercovici, D.

2014-11-01

360

Microstructures and petrology of melt inclusions in the anatectic sequence of Jubrique (Betic Cordillera, S Spain): Implications for crustal anatexis  

NASA Astrophysics Data System (ADS)

We report a new occurrence of melt inclusions in polymetamorphic granulitic gneisses of the Jubrique unit, a complete though strongly thinned crustal section located above the Ronda peridotite slab (Betic Cordillera, S Spain). The gneissic sequence is composed of mylonitic gneisses at the bottom and in contact with the peridotites, and porphyroblastic gneisses on top. Mylonitic gneisses are strongly deformed rocks with abundant garnet and rare biotite. Except for the presence of melt inclusions, microstructures indicating the former presence of melt are rare or absent. Upwards in the sequence, garnet decreases whereas biotite increases in modal proportion. Melt inclusions are present from cores to rims of garnets throughout the entire sequence. Most of the former melt inclusions are now totally crystallized and correspond to nanogranites, whereas some of them are partially made of glass or, more rarely, are totally glassy. They show negative crystal shapes and range in size from ? 5 to 200 ?m, with a mean size of ? 30-40 ?m. Daughter phases in nanogranites and partially crystallized melt inclusions include quartz, feldspars, biotite and muscovite; accidental minerals include kyanite, graphite, zircon, monazite, rutile and ilmenite; glass has a granitic composition. Melt inclusions are mostly similar throughout all the gneissic sequence. Some fluid inclusions, of possible primary origin, are spatially associated with melt inclusions, indicating that at some point during the suprasolidus history of these rocks granitic melt and fluid coexisted. Thermodynamic modeling and conventional thermobarometry of mylonitic gneisses provide peak conditions of ? 850 °C and 12-14 kbar, corresponding to cores of large garnets with inclusions of kyanite and rutile. Post-peak conditions of ? 800-850 °C and 5-6 kbar are represented by rim regions of large garnets with inclusions of sillimanite and ilmenite, cordierite-quartz-biotite coronas replacing garnet rims, and the matrix with oriented sillimanite. Previous conventional petrologic studies on these strongly deformed rocks have proposed that anatexis started during decompression from peak to post-peak conditions and in the field of sillimanite. The study of melt inclusions shows, however, that melt was already present in the system at peak conditions, and that most garnet grew in the presence of melt.

Barich, Amel; Acosta-Vigil, Antonio; Garrido, Carlos J.; Cesare, Bernardo; Taj?manová, Lucie; Bartoli, Omar

2014-10-01

361

(Energetics of silicate melts from thermal diffusion studies)  

SciTech Connect

The first year of this three year renewal award has been used to continue data collection and analysis of thermal (Soret) diffusion in silicate liquid and explore the related process of thermal migration in subliquidus magmas and isothermal interdiffusion. Data collection efforts have been materially aided by advances in thermal insulation in the pressure media outside our pressurized cylindrical heaters. BaCO{sub 3} is very effective in protecting the pressure vessel core from thermal deterioration with the result that the heater inside and outside diameters can be substantially increased. This permits several charges to be run simultaneously in an axisymmetric cluster around a double or triple junction thermocouple which can measure axial thermal gradients in situ. Research during the past year has concentrated in four major areas: Modelling thermal diffusion in multi-component silicate liquids, Soret fractionation of major and minor chemical components, characterization of thermal diffusion in naturally-occurring magmas with an emphasis on volatile bearing rhyolitic melts, and the effects of thermal gradients on silicate magma in the melting interval.

Not Available

1990-01-01

362

Energy Saving Melting and Revert Reduction Technology (E-SMARRT): Melting Efficiency Improvement  

SciTech Connect

Steel foundries melt recycled scrap in electric furnaces and typically consume 35-100% excess energy from the theoretical energy requirement required to pour metal castings. This excess melting energy is multiplied by yield losses during casting and finishing operations resulting in the embodied energy in a cast product typically being three to six times the theoretical energy requirement. The purpose of this research project was to study steel foundry melting operations to understand energy use and requirements for casting operations, define variations in energy consumption, determine technologies and practices that are successful in reducing melting energy and develop new melting techniques and tools to improve the energy efficiency of melting in steel foundry operations.

Principal Investigator Kent Peaslee; Co-PIà ƒ  ¢Ã ‚  € à ‚  ™ s: Von Richards, Jeffrey Smith

2012-07-31

363

Isothermal compressibility in binary platinum based melts  

NASA Astrophysics Data System (ADS)

The method based on concentration dependences of density and formation heat values for determination of fluctuation structure factors and isothermal compressibility has been used for binary Pt-Si and Pt-Sn melts.

Kosnureva, I. G.; Spiridonov, M. A.; Mitko, M. M.; Chentsov, V. P.

2008-02-01

364

A Short Course in The Melting Pot.  

ERIC Educational Resources Information Center

Describes how the events of a week of outdoor education for 40 migrant teenagers of various cultural backgrounds moved from racial and geographic discord to cooperation, proving that the melting pot is still working. (SB)

Cuff, Bill; Churchard, Tim

1983-01-01

365

Melting of monatomic glass with free surfaces.  

PubMed

Melting of monatomic glass with free surfaces has been studied by molecular dynamics simulations in models with Lennard-Jones-Gauss interatomic potential. Models have been heated up from a glassy state toward a normal liquid state. Atomic mechanism of melting has been analyzed via monitoring spatio-temporal arrangements of liquid-like atoms occurred during heating process. Liquid-like atoms are detected via the Lindemann criterion of melting. It is clear that the transition from glass into supercooled liquid of our "ordinary" glass with free surfaces exhibits a non-heterogeneous behavior, i.e., although liquid-like atoms initiate/grow mainly in the surface shell, significant amount of liquid-like atoms also initiates/grows simultaneously in the interior during heating process. We found three characteristic temperatures of melting of glass with a free surface. Temperature dependence of structure and various thermodynamic quantities of the system upon heating is also presented and discussed. PMID:22423847

Hoang, Vo Van; Dong, To Quy

2012-03-14

366

The beginnings of hydrous mantle wedge melting  

NASA Astrophysics Data System (ADS)

This study presents new phase equilibrium data on primitive mantle peridotite (0.33 wt% Na2O, 0.03 wt% K2O) in the presence of excess H2O (14.5 wt% H2O) from 740 to 1,200°C at 3.2-6 GPa. Based on textural and chemical evidence, we find that the H2O-saturated peridotite solidus remains isothermal between 800 and 820°C at 3-6 GPa. We identify both quenched solute from the H2O-rich fluid phase and quenched silicate melt in supersolidus experiments. Chlorite is stable on and above the H2O-saturated solidus from 2 to 3.6 GPa, and chlorite peridotite melting experiments (containing ~6 wt% chlorite) show that melting occurs at the chlorite-out boundary over this pressure range, which is within 20°C of the H2O-saturated melting curve. Chlorite can therefore provide sufficient H2O upon breakdown to trigger dehydration melting in the mantle wedge or perpetuate ongoing H2O-saturated melting. Constraints from recent geodynamic models of hot subduction zones like Cascadia suggest that significantly more H2O is fluxed from the subducting slab near 100 km depth than can be bound in a layer of chloritized peridotite ~ 1 km thick at the base of the mantle wedge. Therefore, the dehydration of serpentinized mantle in the subducted lithosphere supplies free H2O to trigger melting at the H2O-saturated solidus in the lowermost mantle wedge. Alternatively, in cool subduction zones like the Northern Marianas, a layer of chloritized peridotite up to 1.5 km thick could contain all the H2O fluxed from the slab every million years near 100 km depth, which suggests that the dominant form of melting below arcs in cool subduction zones is chlorite dehydration melting. Slab P- T paths from recent geodynamic models also allow for melts of subducted sediment, oceanic crust, and/or sediment diapirs to interact with hydrous mantle melts within the mantle wedge at intermediate to hot subduction zones.

Till, Christy B.; Grove, Timothy L.; Withers, Anthony C.

2012-04-01

367

The melting behavior of aluminum nanoparticles  

Microsoft Academic Search

The melting behavior of aluminum nanoparticles having an oxide passivation layer is examined using a differential scanning calorimetry (DSC). Both broad and narrow size-distributed particles are studied, and the weight-average particle radius ranges from 8 to 50nm. With decreasing particle size, the melting response moves towards lower temperatures and the heat of fusion decreases. The effect of the oxide coating

J. Sun; S. L. Simon

2007-01-01

368

On the initiation of melt fracture.  

NASA Technical Reports Server (NTRS)

Discussion of a problem encountered in the processing of viscoelastic materials that is caused by the presence of a hydrodynamic instability in the extrusion of polymer melts. The importance of the so-called Weissenberg number in determining the onset of the melt fracture is examined using classical linearized hydrodynamic stability analysis. It is shown that the simple shearing flow of a viscoelastic fluid becomes unstable at a critical value of the Weissenberg number. Implications for the extrusion processing of polymers are reviewed.

Mcintire, L. V.

1972-01-01

369

Josephson vortex lattice melting in Bi-2212  

SciTech Connect

The B-T diagram of Josephson vortex lattice melting in Bi-2212 is analyzed (B is magnetic induction parallel to the layers, T is temperature). It is shown that the Josephson vortex lattice melting at B > B* = 0.6-0.7 T is associated with Berezinsky-Kosterlitz-Thouless transition in individual Bi-2212 superconducting layers and is a second-order phase transition.

Latyshev, Yu. I.; Pavlenko, V. N., E-mail: vit@cplire.ru; Orlov, A. P. [Russian Academy of Sciences, Institute of Radio Engineering and Electronics (Russian Federation)

2007-07-15

370

DWPF Macrobatch 2 Melt Rate Tests  

SciTech Connect

The Defense Waste Processing Facility (DWPF) canister production rate must be increased to meet canister production goals. Although a number of factors exist that could potentially increase melt rate, this study focused on two: (1) changes in frit composition and (2) changes to the feed preparation process to alter the redox of the melter feed. These two factors were investigated for Macrobatch 2 (sludge batch 1B) utilizing crucible studies and a specially designed ''melt rate'' furnace. Other potential factors that could increase melt rate include: mechanical mixing via stirring or the use of bubblers, changing the power skewing to redistribute the power input to the melter, and elimination of heat loss (e.g. air in leakage). The melt rate testing in FY00 demonstrated that melt rate can be improved by adding a different frit or producing a much more reducing glass by the addition of sugar as a reductant. The frit that melted the fastest in the melt rate testing was Frit 165. A paper stud y was performed using the Product Composition Control System (PCCS) to determine the impact on predicted glass viscosity, liquidus, durability, and operating window if the frit was changed from Frit 200 to Frit 165. PCCS indicated that the window was very similar for both frits. In addition, the predicted viscosity of the frit 165 glass was 46 poise versus 84 poise for the Frit 200 glass. As a result, a change from Frit 200 to Frit 165 is expected to increase the melt rate in DWPF without decreasing waste loading.

Stone, M.E.

2001-01-03

371

Frustration and Melting of Colloidal Molecular Crystals  

E-print Network

Using numerical simulations we show that a variety of novel colloidal crystalline states and multi-step melting phenomena occur on square and triangular two-dimensional periodic substrates. At half-integer fillings different kinds of frustration effects can be realized. A two-step melting transition can occur in which individual colloidal molecules initially rotate, destroying the overall orientational order, followed by the onset of interwell colloidal hopping, in good agreement with recent experiments.

C. J. Olson Reichhardt; C. Reichhardt

2002-10-14

372

Mineral\\/melt partitioning of trace elements during hydrous peridotite partial melting  

Microsoft Academic Search

This experimental study examines the mineral\\/melt partitioning of incompatible trace elements among high-Ca clinopyroxene, garnet, and hydrous silicate melt at upper mantle pressure and temperature conditions. Experiments were performed at pressures of 1.2 and 1.6 GPa and temperatures of 1,185 to 1,370 °C. Experimentally produced silicate melts contain up to 6.3 wt% dissolved H 2O, and are saturated with an upper mantle peridotite

Glenn A. Gaetani; Adam J. R. Kent; Timothy L. Grove; Ian D. Hutcheon; Edward M. Stolper

2003-01-01

373

On the rheologically critical melt fraction  

NASA Astrophysics Data System (ADS)

With increasing melt fraction ( ?), the strength of partially molten granite decreases from a value characteristic of solid, competent rock to a value nearly equal to that of the melt. Previously published mechanical and microstructural data indicate that deformation in partially molten rocks often involves brittle processes. Thus, the pressure in the melt is expected to be important in determining strength. When the volume changes during deformation, strength and fluid flow will be coupled by such parameters as permeability ( k), storage capacity per unit volume or storativity ( ?s), melt compressibility ( ?f), grain size ( d), fluid viscosity ( ?), and strain rate ( ??). Experiments on brittle rock at low temperatures show that the strain rate at which the internal fluid pressure can be maintained constant is approximately proportional to k/( ??s). An evaluation of published experimental data suggests that this relation also holds for partially molten granites, indicating that the strength of these rocks depends on their transport properties. Since the permeability is related to ?, below a critical melt fraction ( ?rcmf), the melt pressure will change if deformation is not iso-volumetric. By assuming a power-law relationship between k and ?, we estimate that ? rcmf?( ???? f/d m) 1/(n-1)where m and n relate permeability to grain size and ?, respectively.

Renner, Jörg; Evans, Brian; Hirth, Greg

2000-09-01

374

Volcanism by melt-driven Rayleigh-Taylor instabilities and possible consequences of melting for admittance ratios on Venus  

NASA Technical Reports Server (NTRS)

A large number of volcanic features exist on Venus, ranging from tens of thousands of small domes to large shields and coronae. It is difficult to reconcile all these with an explanation involving deep mantle plumes, since a number of separate arguments lead to the conclusion that deep mantle plumes reaching the base of the lithosphere must exceed a certain size. In addition, the fraction of basal heating in Venus' mantle may be significantly lower than in Earth's mantle reducing the number of strong plumes from the core-mantle boundary. In three-dimensional convection simulations with mainly internal heating, weak, distributed upwellings are usually observed. We present an alternative mechanism for such volcanism, originally proposed for the Earth and for Venus, involving Rayleigh-Taylor instabilities driven by melt buoyancy, occurring spontaneously in partially or incipiently molten regions.

Tackley, P. J.; Stevenson, D. J.; Scott, D. R.

1992-01-01

375

Melt inclusions in pegmatite quartz: complete miscibility between silicate melts and hydrous fluids at low pressure  

Microsoft Academic Search

Fluorine-, boron- and phosphorus-rich pegmatites of the Variscan Ehrenfriedersdorf complex crystallized over a temperature\\u000a range from about 700 to 500?°C at a pressure of about 1?kbar. Pegmatite quartz crystals continuously trapped two different\\u000a types of melt inclusions during cooling and growth: a silicate-rich H2O-poor melt and a silicate-poor H2O-rich melt. Both melts were simultaneously trapped on the solvus boundaries of

R. Thomas; J. D. Webster; W. Heinrich

2000-01-01

376

Supplementary documentation for an Environmental Impact Statement regarding the Pantex Plant: radiological consequences of immediate inhalation of plutonium dispersed by postulated accidents  

Microsoft Academic Search

This report documents work performed in support of preparation of an Environmental Impact Statement (EIS) regarding the Department of Energy's (DOE) Pantex Plant near Amarillo, Texas. It describes methods used to estimate potential health consequences offsite resulting from inhalation of plutonium dispersed by each of several postulated accidents. The primary topic of this report is the delayed health effects of

J. C. Elder; R. H. Olsher; J. M. Graf

1982-01-01

377

Review of experiments to evaluate the ability of electrical heater rods to simulate nuclear fuel rod behavior during postulated loss-of-coolant accidents in light water reactors  

SciTech Connect

Issues related to using electrical fuel rod simulators to simulate nuclear fuel rod behavior during postulated loss-of-coolant accident (LOCA) conditions in light water reactors are summarized. Experimental programs which will provide a data base for comparing electrical heater rod and nuclear fuel rod LOCA responses are reviewed.

McPherson, G D; Tolman, E L

1980-01-01

378

Genesis of platinum-bearing ultrabasic massifs in the plutonic chambers: evidence from melt inclusions  

NASA Astrophysics Data System (ADS)

Platinum-bearing ultramafic massifs occur as bodies of concentrically zonal inner structures due to the successive replacement of dunite with pyroxenite and gabbro from their cores to margins. A most important peculiarity of such massifs is their dunite cores, to which commercial Pt deposits are related. There are a different opinions about genesis of these massifs and geological, petrological, geochemical methods not always can solve this question. We found melt inclusions in Cr-spinel from dunites of the platinum-bearing Konder and Inagli massifs (Siberian Platform) and this provides direct evidence of the participation of magmatic systems in the crystallization of ultrabasic rocks. Contents of most major chemical components in the heated and quenched melt inclusions are close to those in biotite-pyroxene picrite and this testifies dunite crystallization from ultrabasic alkaline magma. Ion probe analyses of melt inclusions in Cr-spinel yielded relatively high water concentration in ultrabasic melts of the Konder (0.45-0.53 wt %) and Inagli (up to 0.63 wt %) massifs. These data are generally close to the water contents in magma that produced dunites of ophiolites (0.58-0.65 wt %) (Simonov et al., 2009). The REE patterns of inclusions in Cr-spinel from the Konder and Inagli dunites show a pronounced negative slope with strong enrichment of LREE relative to HREE, as is typical of plume-related magmatic systems of oceanic islands and continental hotspots. The values of such indicator ratios as Nb/U (23.4), Zr/Nb (7.20), and Th/U (3.0) of inclusions practically exactly coincide with those of glasses from areas of continental hotspots (Naumov et al., 2010). At the Nb/Y-Zr/Y diagram the data points of the inclusions plot within the field of melts with a plume source. As a whole the patterns of trace elements and REE in melt inclusions in the Cr-spinel provide evidence that mantle plumes affected the magmatic events, that produced dunites of the studied platinum-bearing ultramafic massifs. Our simulations on the basis of melt inclusion compositions by the PLUTON program package (Lavrenchuk, 2004) allowed to evaluate the crystallization temperature of dunites in the intrusive chambers. The most part of olivine was crystallized at 1460-1300°C and then, when the melt became less magnesian, this mineral continued to crystallize until to 1230°. The parameters evaluated with the help of another program (PETROLOG; Danyushevsky, 2001), based on data on melt inclusions, indicate that minimum temperature of the melts, from which olivine crystallized, was approximately 1230°. The model melt compositions (PLUTON program) are in good agreement with data on inclusions in Cr-spinel. For example, the calculated melt composition with 25.5 wt % MgO corresponds to 2.82 wt % 2, respectively, and melt inclusions with the same MgO (25.7 wt %) contain practically exactly coinciding K2O concentration of 2.7 wt %.

Simonov, V.; Prikhod'ko, V.

2012-04-01

379

Cooperative atomic motions and core rearrangement in dislocation cross slip  

NASA Astrophysics Data System (ADS)

Atomistic study of cross slip of a screw dislocation in copper is presented using the action-optimization numerical technique which seeks the most probable dynamic pathway on the potential-energy surface of the atomic system during the cross-slip process. The observed mechanism reveals features of both competing mechanisms postulated in literature, i.e., the Fleischer mechanism and the Friedel-Escaig mechanism. Due to cooperative atomic motions and complex core rearrangement during the process, the activation energies of the current cross-slip mechanism are around 0.5eV less than the lowest ever reported in corresponding studies using atomistic numerical techniques.

Pendurti, Srinivas; Jun, Sukky; Lee, In-Ho; Prasad, Vish

2006-05-01

380

Melting and Phase Relations in the FeO-FeS System at High Pressure  

NASA Astrophysics Data System (ADS)

Terrestrial planetary cores, like that of the Earth, are composed of iron alloys with light elements such as O, S, Si, and/or C, and therefore the phase relations of these iron-rich systems are essential to understanding the structure, composition, and evolution of planetary cores. Binary Fe-X phase diagrams are largely established up to approximately Earth's core-mantle boundary pressures at least, but the relevant ternary and higher order phase equilibria are less well understood. Here we present phase relations, including melting, on the FeO-FeS join to better constrain the Fe-FeO-FeS system that may be important to planetary cores, including Earth's. We performed synchrotron X-ray diffraction experiments to monitor the phases present in FeO:FeS mixtures up to 60 GPa and >2500 K. A basic result is that FeO and FeS do coexist at high pressures and temperatures, with no evidence of a new phase forming between the two. At pressures near 46 GPa the eutectic composition lies on the FeS-rich side of this binary, as indicated by the loss of FeS diffraction and persistence of FeO diffraction in a 1:1 FeO:FeS mixture. Melting in the FeO-FeS binary at high pressures occurs at temperatures within ~100-200 K of the FeS melting curve [1]. Building upon earlier work on the structural (e.g., [1,2]) and binary melting (e.g., [3,4]) behavior in the Fe-FeS and Fe-FeO systems, these results help define the ternary Fe-FeO-FeS system under P,T conditions relevant to terrestrial planetary cores. In particular, the P,T conditions of the Martian core are covered by this study, and the FeO-FeS system may be especially relevant there because of its high mantle FeO content and its low core density, suggesting a relatively high sulfur content. [1] Reaman et al., AGU Fall Meeting 2012. [2] Fischer et al., Geophys. Res. Lett. 38, L24301, 2011. [3] Campbell et al., Phys. Earth Planet. Int. 162, 119-128, 2007. [4] Seagle et al., Earth Planet. Sci. Lett. 265, 655-665, 2008.

Campbell, A. J.; Reaman, D. M.; Fischer, R. A.; Chidester, B.; Myers, G.; Heinz, D. L.; Prakapenka, V.

2013-12-01

381

Academic Rigor: The Core of the Core  

ERIC Educational Resources Information Center

Some educators see the Common Core State Standards as reason for stress, most recognize the positive possibilities associated with them and are willing to make the professional commitment to implementing them so that academic rigor for all students will increase. But business leaders, parents, and the authors of the Common Core are not the only…

Brunner, Judy

2013-01-01

382

Reconstruction of Past Temperatures of Glaciers Subjected to Subsurface Melting  

Microsoft Academic Search

Many glaciers are subjected to melting due to high summer air temperatures. Melt water percolates into the snow-firn sequences. Melting intensity during summer months is proportional to the third power of the mean air temperature. Hence, small changes of summer air temperatures induce large changes of the active layer temperatures. The refreezing of melt water results in the sub-surface heat

O. V. Nagornov; Y. Konovalov; O. Sergienko

2002-01-01

383

Microstructural evidence of melting in crustal rocks (Invited)  

Microsoft Academic Search

The signature of the former presence of melt on a microscopic scale is highly variable, subject to modification both during the melting event and during its subsequent history. Static pyrometamorphism results in melt films on grain boundaries between reactant phases. If a volume increase is involved, melting results in hydrofracture. On a longer timescale, as demonstrated by fragments of the

M. B. Holness; B. Cesare; E. W. Sawyer

2010-01-01

384

Heat recovery and melting system for scrap metals  

Microsoft Academic Search

Metallic scrap contaminated with combustibles is melted in a reverberatory melting furnace having two communicating wells; one being an enclosed sidewell, which is the receiving well for scrap material during melting, and the other being an enclosed main holding well for molten metal. The main well has burner means to provide heat for melting the metal and treating the scrap

R. E. Jenson; J. C. Pryor

1982-01-01

385

Exploratory study of molten core material\\/concrete interactions, July 1975March 1977. [BWR; PWR  

Microsoft Academic Search

An experimental study of the interaction between high-temperature molten materials and structural concrete is described. The experimental efforts focused on the interaction of melts of reactor core materials weighing 12 to 200 kg at temperatures 1700 to 2800°C with calcareous and basaltic concrete representative of that found in existing light-water nuclear reactors. Observations concerning the rate and mode of melt

D. A. Powers; D. A. Dahlgren; J. F. Muir; W. D. Murfin

1978-01-01

386

The Energy Crisis in the Earth's Core (Invited)  

NASA Astrophysics Data System (ADS)

Calculations of the core's thermal history and power required to drive the dynamo have, in the past, suffered from uncertainties in some of the key physical properties. Recent ab initio calculations, some of which have been confirmed by high pressure experiments, have removed much of this uncertainty. Unfortunately the new numbers require a large amount of heat to cross the core-mantle boundary (CMB) into the mantle: the Gruneissen constant and melting point at the inner core boundary determine a steep adiabatic gradient and the thermal and electrical conductivities are 2-4 times higher than the values in recent use. High electrical conductivity means the dynamo requires less power to sustain the magnetic field, but high thermal conductivity means more heat leaks away down the steep adiabatic gradient. It is hard to explain current geomagnetic secular variation without fluid upwelling within about 100 km of the core surface, requiring the core to be adiabatic throughout most of its depth. Here we calculate the cooling rate required to balance the entropy of thermal conduction down the adiabat. This is a lower bound because it ignores all other entropy changes associated with diffusion, notably magnetic and molecular. The heat flux across the CMB is then found from the cooling rate. The largest remaining uncertainty is the seismologically-determined density jump at the inner core boundary, which governs the fraction of light elements in the outer core, the strength of compositional convection, the melting temperature of the mixture at the inner core boundary (ICB), and the adiabatic gradient. A high density jump means more light elements are released on freezing, the higher concentration of light elements lowers the melting point, which in turn lowers the temperature throughout the core and shallows the adiabatic gradient. Unfortunately, calculations of the acoustic velocity of candidate mixtures corresponding to a high density jump do not fit the seismic models well, limiting how high the jump can be. Our minimum heat flux is less than the heat conducted down the adiabat at the CMB. Compositional convection could stir the core to within 100 km of the surface, although the severe thermal stratification makes this seem unlikely. However, heat flux across the CMB, as determined by mantle convection, can vary from place to place by a factor of 10 or more. The adiabat only needs to be exceeded in one spot for convection to stir the core everywhere, albeit weakly, the mean heat flux remaining subadiabatic. This mode of convection could explain the low secular variation in the Pacific, where the mantle is hot and heat flux is low. The dynamo is be driven deep within the core where compositional convection is most vigorous.

Gubbins, D.; Davies, C.; Alfe, D.

2013-12-01

387

Shock-Melted Regions in the Krymka (LL3) Chondrite  

NASA Astrophysics Data System (ADS)

Shock effects of various intensities are common in all kinds of meteorites, but, in ordinary chondrites, the most severe ones are observed mostly in metamorphosed chondrites (petrologic types 5 and 6), and they are rare in type 3 [1]. However, we report here observations of strong shock effects in a specimen of the Krymka (LL3.1/S3) chondrite, one of the three most primitive ordinary chondrites. Examination of various samples of Krymka in the Ukrainian meteorite collection has already revealed evidences of shock effects, indicative of pressures of 25-45 GPa (assuming non-porous material) and temperatures <= 500 degrees C, with local excursions to >=988 degrees C (melting of Fe-FeS eutectic) [2]. Sample N1290/29 (134 g), from the same collection, contains light-colored, friable, completely melted zones. Observations were made on 6 polished sections from that specimen, with a total area of 14 cm2. In 4 of these, 4 melted regions occupy a total of ~3 cm2. They are chondrule-free and consist of porphyritic and skeletal silicates (mainly olivine) in a cryptocrystalline mesostasis, along with metal-troilite mixtures with dendritic and cellular structures. Olivine composition is variable (Fa(sub)10-26) but to a lesser extent than in Krymka chondrules (Fa(sub)0-35). The mesostasis is also inhomogeneous. Apart from a few notable exceptions, olivine crystals are normally zoned, with FeO increasing from core to rim. Fe-Ni cells are zoned as well, consisting of a core with 11.2-22.6 wt%Ni and 0.83-0.96 wt%Co (probably martensite), and a Ni-rich rim (up to 51.3 wt%Ni, probably tetrataenite). The metal contains P (0.12-0.43 wt%), which seems to be, at least in part, in tiny schreibersite inclusions, and the troilite contains Ni (0.05- 4.2 wt%Ni). Metal-troilite mixtures contain abundant globules (up to 15 microns in diameter) of a Fe-Na phosphate (maybe maricite). These globules are usually rimmed with numerous euhedral micrometer-sized chromites. Larger euhedral chromites also occur isolated in metal-troilite. The melted regions are surrounded by a transition zone with chondritic texture, containing completely melted troilite and partially melted metal. The highly variable Co concentration (0.2-13.0 wt%) of the metal grains in this zone reflects the high degree of unequilibration of the Krymka chondrite. Shock pressure in the range 75-90 GPa is normally required to induce local complete melting of chondritic matter, but, in the present case, pressure as low as 30 GPa may be responsible for the observed effects, because of the porous nature of type 3 material [1]. In any case, the temperature must have been larger than 1450 degrees C. Experimental data on zoning trends in olivine [3] and Ni content in troilite [4] suggest a cooling rate of at least 100 degrees C/h. The association of P and Cr with metal-troilite reflects their association with metal in the host: Ca- phosphates are common at the boundaries of Krymka metal grains and many of these contain myriads of tiny chromites [5]. P and Cr were probably reduced at high temperature and they dissolved in metal-troilite liquid. Upon cooling, they reoxidized and crystallised. The unusual phosphate may result from higher volatility and mobility of Na relative to Ca. Mechanical deformations (shear) of some of these phosphate globules and of melted troilite attest that, after complete solidification of the melted regions, Krymka was subjected to other, less intense shock(s). References: [1] St"ffler D. et al. (1991) GCA, 55, 3845. [2] Semenenko V. P. et al. (1987) The Meteorites of Ukraine, 218 pp., Naukova Dumka (in Russian). [3] Radomsky P. M. and Hewins R. H. (1990) GCA, 54, 3475. [4] Smith B. A. and Goldstein J. I. (1977) GCA, 41, 1061. [5] Perron C. and Bourot-Denise M. (1992) LPS XXIII, 1055.

Semenenko, V. P.; Perron, C.

1995-09-01

388

An empirical method for calculating melt compositions produced beneath mid-ocean ridges: Application for axis and off-axis (seamounts) melting  

NASA Astrophysics Data System (ADS)

We present a new method for calculating the major element compositions of primary melts parental to mid-ocean ridge basalt (MORB). This model is based on the experimental data of Jaques and Green (1980), Falloon et al. (1988), and Falloon and Green (1987, 1988) which are ideal for this purpose. Our method is empirical and employs solid-liquid partition coefficients (Di) from the experiments. We empirically determine Di = ƒ(P,F) and use this to calculate melt compositions produced by decompression-induced melting along an adiabat (column melting). Results indicate that most MORBs can be generated by 10-20% partial melting at initial pressures (P0) of 12-21 kbar. Our primary MORB melts have MgO = 10-12 wt %. We fractionate these at low pressure to an MgO content of 8.0 wt % in order to interpret natural MORB liquids. This model allows us to calculate Po, Pƒ, To, Tƒ, and F for natural MORB melts. We apply the model to interpret MORB compositions and mantle upwelling patterns beneath a fast ridge (East Pacific Rise (EPR)8°N to 14°N), a slow ridge (mid-Atlantic Ridge (MAR) at 26°S), and seamounts near the EPR (Lament seamount chain). We find mantle temperature differences of up to 50°-60°C over distances of 30-50 km both across axis and along axis at the EPR. We propose that these are due to upward mantle flow in a weakly conductive (versus adiabatic) temperature gradient. We suggest that the EPR is fed by a wide (-100 km) zone of upwelling due to plate separation but has a central core of faster buoyant flow. An along-axis thermal dome between the Siqueiros transform and the 11°45' Overlapping Spreading center (OSC) may represent such an upwelling; however, in general there is a poor correlation between mantle temperature, topography, and the segmentation pattern at the EPR. For the Lament seamounts we find regular across-axis changes in Po and F suggesting that the melt zone pinches out off axis. This observation supports the idea that the EPR is fed by a broad upwelling which diminishes in vigor off axis. In contrast with the EPR axis, mantle temperature correlates well with topography at the MAR, and there is less melting under offsets. The data are consistent with weaker upwelling under offsets and an adiabatic temperature gradient in the sub axial mantle away from offsets. The MAR at 26°S exhibits the so-called local trend of Klein and Langmuir (1989). Our model indicates that the local trend cannot be due solely to intracolumn melting processes. The local trend seems to be genetically associated with slow-spreading ridges, and we suggest it is due to melting of multiple individual domains that differ in initial and final melting pressure within segments fed by buoyant focused mantle flow.

Niu, Yaoling; Batiza, Rodey

1991-12-01

389

An empirical method for calculating melt compositions produced beneath mid-ocean ridges: for axis and off-axis (seamounts) melting application  

NASA Astrophysics Data System (ADS)

We present a new method for calculating the major element compositions of primary melts parental to mid-ocean ridge basalt (MORB). This model is based on the experimental data of Jaques and Green (1980), Falloon et al. (1988), and Falloon and Green (1987, 1988) which are ideal for this purpose. Our method is empirical and employs solid-liquid partition coefficients (Di) from the experiments. We empirically determine Di=f(P,F) and use this to calculate melt compositions produced by decompression-induced melting along an adiabat (column melting). Results indicate that most MORBs can be generated by 10-20% partial melting at initial pressures (P0) of 12-21 kbar. Our primary MORB melts have MgO=10-12 wt %. We fractionate these at low pressure to an MgO content of 8.0 wt% in order to interpret natural MORB liquids. This model allows us to calculate Po, Pf, To, Tf, and F for natural MORB melts. We apply the model to interpret MORB compositions and mantle upwelling patterns beneath a fast ridge (East Pacific Rise (EPR) 8°N to 14°N), a slow ridge (mid-Atlantic Ridge (MAR) at 26°S), and seamounts near the EPR (Lamont seamount chain). We find mantle temperature differences of up to 50°-60°C over distances of 30-50 km both across axis and along axis at the EPR. We propose that these are due to upward mantle flow in a weakly conductive (versus adiabatic) temperature gradient. We suggest that the EPR is fed by a wide (~100 km) zone of upwelling due to plate separation but has a central core of faster buoyant flow. An along-axis thermal dome between the Siqueiros transform and the 11°45' Overlapping Spreading Center (OSC) may represent such an upwelling; however, in general there is a poor correlation between mantle temperature, topography, and the segmentation pattern at the EPR. For the Lamont seamounts we find regular across-axis changes in Po and F suggesting that the melt zone pinches out off axis. This observation supports the idea that the EPR is fed by a broad upwelling which diminishes in vigor off axis. In contrast with the EPR axis, mantle temperature correlates well with topography at the MAR, and there is less melting under offsets. The data are consistent with weaker upwelling under offsets and a adiabatic temperature gradient in the subaxial mantle away from offsets. The MAR at 26°S exhibits the so-called local trend of Klein and Langmuir (1989). Our model indicates that the local trend cannot be due solely to intracolumn melting processes. The local trend seems to be genetically associated with slow-spreading ridges, and we suggest it is due to melting of multiple individual domains that differ in initial and final melting pressure within segments fed by buoyant focused mantle flow.

Batiza, Rodey

1991-12-01

390

Materials Science and Engineering A 442 (2006) 170174 Contrasting viscoelastic behavior of melt-free and melt-bearing olivine  

E-print Network

-free and melt-bearing olivine: Implications for the nature of grain-boundary sliding Ian Jacksona,, Ulrich H bstract Melt-free and basaltic (complex alumino-silicate) melt-bearing specimens of fine oscillation and microcreep, display markedly different behavior. For the melt-bearing aterials, superimposed

391

Materials Science and Engineering A 442 (2006) 170174 Contrasting viscoelastic behavior of melt-free and melt-bearing olivine  

E-print Network

-free and melt-bearing olivine: Implications for the nature of grain-boundary sliding Ian Jacksona,, Ulrich H Abstract Melt-free and basaltic (complex alumino-silicate) melt-bearing specimens of fine oscillation and microcreep, display markedly different behavior. For the melt-bearing materials, superimposed

392

The Bloomington (LL6) chondrite and its shock melt glasses  

NASA Astrophysics Data System (ADS)

The shock melt glasses of the Bloomington LL-group chondrite were examined using electron-beam microscopy and compared with data from studies of other shock melt glasses. Petrologic and mineralogic characterizations were also performed of the samples. The metal contents of the meteorite were almost wholly Ni-rich martensite. The glasses resembled shock melt glasses in L-group chondrites, and were indicative of isochemical melting during one melt phase, i.e., a very simple history.

Dodd, R.; Olsen, E. J.; Clarke, R. S., Jr.

1985-09-01

393

Impact induced melting and the development of large igneous provinces  

Microsoft Academic Search

We use hydrodynamic modelling combined with known data on mantle melting behaviour to examine the potential for decompression melting of lithosphere beneath a large terrestrial impact crater. This mechanism may generate sufficient quantity of melt to auto-obliterate the crater. Melting would initiate almost instantaneously, but the effects of such massive mantle melting may trigger long-lived mantle up-welling that could potentially

Adrian P. Jones; G. David Price; Neville J. Price; Paul S. Decarli; Richard A. Clegg

2002-01-01

394

Mantle melts, metasomatism and diamond formation: Insights from melt inclusions in xenoliths from Diavik, Slave Craton  

Microsoft Academic Search

Abundant carbonatitic to ultramafic melt inclusions 0.2–2.5mm in diameter occur in the Cr–diopside of megacrystalline lherzolite xenoliths from the A154 kimberlite of the Diavik mine, Lac de Gras area. The melts range from carbonatitic (50–97% carbonate) to Ca–Mg–silicic (10–50% carbonate) to Mg–silicic (

D. P. Araújo; W. L. Griffin; S. Y. O'Reilly

2009-01-01

395

Olivine-hosted melt inclusions in Hawaiian picrites: equilibration, melting, and plume source characteristics  

E-print Network

Olivine-hosted melt inclusions in Hawaiian picrites: equilibration, melting, and plume source Hawaiian volcanoes (Koolau, Mauna Loa, Kilauea, Loihi, and Hualalai) have major and trace element that distinguish Hawaiian shield volcanoes, but with considerably greater diversity than whole rock compositions

Kurapov, Alexander

396

Energy Saving Melting and Revert Reduction Technology: Melting Efficiency in Die Casting Operations  

SciTech Connect

This project addressed multiple aspects of the aluminum melting and handling in die casting operations, with the objective of increasing the energy efficiency while improving the quality of the molten metal. The efficiency of melting has always played an important role in the profitability of aluminum die casting operations. Consequently, die casters need to make careful choices in selecting and operating melting equipment and procedures. The capital cost of new melting equipment with higher efficiency can sometimes be recovered relatively fast when it replaces old melting equipment with lower efficiency. Upgrades designed to improve energy efficiency of existing equipment may be well justified. Energy efficiency is however not the only factor in optimizing melting operations. Melt losses and metal quality are also very important. Selection of melting equipment has to take into consideration the specific conditions at the die casting shop such as availability of floor space, average quantity of metal used as well as the ability to supply more metal during peaks in demand. In all these cases, it is essential to make informed decisions based on the best available data.

David Schwam

2012-12-15

397

Trapped Melt in theJosephine Peridotite: Implications for Permeability and Melt  

E-print Network

Trapped Melt in theJosephine Peridotite: Implications for Permeability and Melt Extraction NOVEMBER 25, 2009 ADVANCE ACCESS PUBLICATION JANUARY 15, 2010 Tabular dunites in the Josephine peridotite within these channels during cooling and exhumation of the peridotite massif was calculated using a mass

398

Leaching characteristics of lead from melting furnace fly ash generated by melting of incineration fly ash.  

PubMed

This study investigated the effect of the chemical composition of incineration fly ash on the leaching characteristics of Pb from melting furnace fly ash generated by melting incineration fly ash. Melting furnace fly ash from both a real-scale melting process and lab-scale melting experiments was analyzed. In addition, the theoretical behavior of Cl that affects the leaching characteristics of Pb was simulated by a thermodynamic equilibrium calculation. Proportions of water-soluble Pb in the melting furnace fly ash were correlated with equivalent ratios of total Pb in the ash and Cl transferred to gas. The amount of Cl in the gas increased with an increase in the molar ratio of Cl to Na and K in the incineration fly ash. The thermodynamic calculation predicted that HCl generation is promoted by the increase in the molar ratio, and X-ray photoelectron spectroscopy indicated a possible presence of PbCl(2) in the melting furnace fly ash. These results implied that the formation of water-soluble PbCl(2) with HCl was affected by the relationships among the amounts of Na, K, and Cl in the incineration fly ash. This is highly significant in determining the leaching characteristics of Pb from the melting furnace fly ash. PMID:22789656

Okada, Takashi; Tomikawa, Hiroki

2012-11-15

399

Internal stress-induced melting below melting temperature at high-rate laser heating  

SciTech Connect

In this Letter, continuum thermodynamic and phase field approaches (PFAs) predicted internal stress-induced reduction in melting temperature for laser-irradiated heating of a nanolayer. Internal stresses appear due to thermal strain under constrained conditions and completely relax during melting, producing an additional thermodynamic driving force for melting. Thermodynamic melting temperature for Al reduces from 933.67?K for a stress-free condition down to 898.1?K for uniaxial strain and to 920.8?K for plane strain. Our PFA simulations demonstrated barrierless surface-induced melt nucleation below these temperatures and propagation of two solid-melt interfaces toward each other at the temperatures very close to the corresponding predicted thermodynamic equilibrium temperatures for the heating rate Q?1.51×10{sup 10}K/s. At higher heating rates, kinetic superheating competes with a reduction in melting temperature and melting under uniaxial strain occurs at 902.1?K for Q?=?1.51?×?10{sup 11?}K/s and 936.9?K for Q?=?1.46?×?10{sup 12?}K/s.

Hwang, Yong Seok, E-mail: yshwang@iastate.edu [Department of Aerospace Engineering, Iowa State University, Ames, Iowa 50011 (United States); Levitas, Valery I., E-mail: vlevitas@iastate.edu [Departments of Aerospace Engineering, Mechanical Engineering, and Material Science and Engineering, Iowa State University, Ames, Iowa 50011 (United States)

2014-06-30

400

Statistical extraction of volcanic sulphate from nonpolar ice cores  

NASA Astrophysics Data System (ADS)

Ice cores from outside the Greenland and Antarctic ice sheets are difficult to date because of seasonal melting and multiple sources (terrestrial, marine, biogenic and anthropogenic) of sulfates deposited onto the ice. Here we present a method of volcanic sulfate extraction that relies on fitting sulfate profiles to other ion species measured along the cores in moving windows in log space. We verify the method with a well dated section of the Belukha ice core from central Eurasia. There are excellent matches to volcanoes in the preindustrial, and clear extraction of volcanic peaks in the post-1940 period when a simple method based on calcium as a proxy for terrestrial sulfate fails due to anthropogenic sulfate deposition. We then attempt to use the same statistical scheme to locate volcanic sulfate horizons within three ice cores from Svalbard and a core from Mount Everest. Volcanic sulfate is <5% of the sulfate budget in every core, and differences in eruption signals extracted reflect the large differences in environment between western, northern and central regions of Svalbard. The Lomonosovfonna and Vestfonna cores span about the last 1000 years, with good extraction of volcanic signals, while Holtedahlfonna which extends to about AD1700 appears to lack a clear record. The Mount Everest core allows clean volcanic signal extraction and the core extends back to about AD700, slightly older than a previous flow model has suggested. The method may thus be used to extract historical volcanic records from a more diverse geographical range than hitherto.

Moore, J. C.; Beaudon, E.; Kang, Shichang; Divine, D.; Isaksson, E.; Pohjola, V. A.; van de Wal, R. S. W.

2012-02-01

401

REVIEWS OF TOPICAL PROBLEMS: Experimental methods for determining the melting temperature and the heat of melting of clusters and nanoparticles  

NASA Astrophysics Data System (ADS)

Unlike macroscopic objects, clusters and nanoparticles lack a definite melting temperature at a given pressure but rather have their solid and liquid phases coexistent in a certain temperature range and their melting temperature dependent on the particle size. As the particle size decreases, the melting temperature becomes fundamentally difficult to define. This review examines methods for measuring the melting temperature and the heat of melting of clusters and nanoparticles. The temperature (internal energy) of the particles is defined and how it affects the properties of and processes involving the particles is discussed. The melting features of clusters and nanoparticles versus bulk materials are examined. Early methods of determining the melting temperature of large clusters are described. New precision methods of measuring the melting temperature and the heat of melting of clusters are discussed, which use the clusters themselves as 'high-sensitivity calorimeters' to measure energy. Laser-based nanoparticle melting techniques are outlined.

Makarov, Grigorii N.

2010-05-01

402

The lunar highland melt-rock suite  

NASA Technical Reports Server (NTRS)

Size can be used as a criterion to select 18 large (larger than 1 cm) samples from among 148 melt-rock fragments of all sizes. This selection provides a suite of large samples which represent the important chemical variants among highland melt rocks; each large sample has enough material for a number of sample-destructive studies, as well as for future reference. Cluster analysis of the total data base of 148 highland melt rocks shows six distinct groups: anorthosite, gabbroic anorthosite, anorthositic gabbro ('highland basalt'), low K Fra Mauro, intermediate-K Fra Mauro, and high-K. Large samples are available for four of the melt-rock groups (gabbroic anorthosite, anorthositic gabbro, low-K Fra Mauro, and intermediate-K Fra Mauro). This sample selection reveals two subgroups of anorthositic gabbro (one anorthite-poor with negative Eu anomaly and one anorthite-rich without Eu anomaly). There is a sharp distinction between those Apollo 16 melt rocks and glasses which have both been classified as 'gabbroic anorthosite'.

Vaniman, D. T.; Papike, J. J.

1978-01-01