Kaon Condensation in a Nambu--Jona-Lasinio (NJL) Model at High Density

We demonstrate a fully self-consistent microscopic realization of a kaon-condensed colour-flavour locked state (CFLK0) within the context of a mean-field NJL model at high density. The properties of this state are shown to be consistent with the QCD low-energy effective theory once the proper gauge neutrality conditions are satisfied, and a simple matching procedure is used to compute the pion decay constant, which agrees with the perturbative QCD result. The NJL model is used to compare the energies of the CFLK0 state to the parity even CFL state, and to determine locations of the metal/insulator transition to a phase with gapless fermionic excitations in the presence of a non-zero hypercharge chemical potential and a non-zero strange quark mass. The transition points are compared with results derived previously via effective theories and with partially self-consistent NJL calculations. We find that the qualitative physics does not change, but that the transitions are slightly lower.Comment: 21 pages, ReVTeX4. Clarified discussion and minor change

A More Complete Thermodynamic Framework For Fluent Continua

Polar decomposition of the changing velocity gradient tensor in a deforming fluent continua into pure stretch rates and rates of rotations shows that a location and its neighboring locations can experience different rates of rotations during evolution. Alternatively, we can also consider decomposition of the velocity gradient tensor into symmetric and skew symmetric tensors. The skew symmetric tensor is also a measure of pure rates of rotations whereas the symmetric tensor is a measure of strain rates. The measures of the internal rates of rotations due to deformation in the two approaches describe the same physics but in different forms. Polar decomposition gives the rate of rotation matrix and not the rates of rotation angles whereas the skew symmetric part of the velocity gradient tensor yields rates of rotation angles that are explicitly defined in terms of velocity gradients. These varying rates of rotations at neighboring locations arise due to varying deformation of the continua, hence are internal to the volume of matter and are explicitly defined by deformation. If the internal varying rates of rotations are resisted by the continua, then there must exist internal moments corresponding to these. The internal rates of rotations and the corresponding moments can result in additional rate of energy storage or rate of dissipation. This physics is all internal to the deforming continua and exists in all deforming isotropic, homogeneous fluent continua but is completely neglected in the presently used thermodynamic framework for fluent continua. In this paper we present derivation of a more complete thermodynamic framework in which the derivation of the conservation and balance laws consider additional physics due to varying rates of rotations. The currently used thermodynamic framework for fluent continua is a subset of the thermodynamic framework presented in this paper. The continuum theory presented here considers internal varying rates of rotations and the associated conjugate moments in the derivation of conservation and balance laws, thus the theory presented in this paper can be called “a polar continuum theory” but is different than micropolar continuum theories published currently in which material points have six external degrees of freedom i.e. the rotation rates are additional external degrees of freedom. In the remainder of the paper we refer to this new thermodynamic framework as ‘a polar continuum theory’. The continuum theory presented here only accounts for internal rotation rates and associated moments that exist as a consequence of deformation but are neglected in the present theories hence this theory results in a more complete thermodynamic framework. The polar continuum theory and the resulting thermodynamic framework presented in this paper is suitable for compressible as well as incompressible thermoviscous fluent continua such as Newtonian, Power law, Carreau-Yasuda fluids etc. and thermoviscoelastic fluent continua such as Maxwell, Oldroyd-B, Giesekus etc. The thermodynamic framework presented here is applicable to all isotropic, homogeneous fluent continua. Obviously the constitutive theories will vary depending upon the choice of physics. These are considered in subsequent papers

A MORE COMPLETE THERMODYNAMIC FRAMEWORK FOR SOLID CONTINUA

The Jacobian of deformation at a material point can be decomposed into the stretch tensor and the rotation tensor. Thus, varying Jacobians of deformation at the neighboring material points in the deforming volume of solid continua would yield varying stretch and rotation tensors at the material points. Measures of strain, such as Green’s strain, at a material point are purely a function of the stretch tensor, i.e. the rotation tensor plays no role in these measures. Alternatively, we could also consider decomposition of displacement gradient tensor into symmetric and skew symmetric tensors. Skew symmetric tensor is also a measure of pure rotations whereas symmetric tensor is a measure of strains, i.e. stretches. The measures of rotations in these two approaches describe the same physics but are in different forms. Polar decomposition gives the rotation matrix and not the rotation angles whereas the skew symmetric part of the displacement gradient tensor yields rotation angles that are explicitly and conveniently defined in terms of the displacement gradients. The varying rotations and rotation rates arise in all deforming solid continua due to varying deformation of the continua at neighboring material points, hence are internal to the volume of solid continua and are explicitly defined by the deformation, therefore do not require additional degrees of freedom to define them. If the internal varying rotations and their rates are resisted by the continua, then there must exist internal moments corresponding to these. The internal rotations and their rates and the corresponding moments can result in additional energy storage and dissipation. This physics is all internal to the deforming continua (hence does not require consideration of additional external degrees of freedom and associated external moments) and is neglected in the presently used continuum theories for isotropic, homogeneous solid continua. The continuum theory presented in this paper considers internal varying rotations and associated conjugate moments in the derivation of the conservation and balance laws, thus the theory presented in this paper is “a polar theory for solid continua” but is different than the micropolar theories published currently in which material points have six external degrees of freedom i.e. rotations are additional external degrees of freedom. This polar continuum theory only accounts for internal rotations and associated moments that exist as a consequence of deformation but are neglected in the present theories. We call this theory “a polar continuum theory” as it considers rotations and moments as conjugate pairs in a deforming solid continua though these are internal, hence are purely related to the deformation of the solid. It is shown that the polar continuum theory presented in this paper is not the same as the strain gradient theories reported in the literature. The differences are obviously in terms of the physics described by them and the mathematical details associated with conservation and balance laws. In this paper, we only consider polar continuum theory for small deformation and small strain. This polar continuum theory presented here is a more complete thermodynamic framework as it accounts for additional physics of internally varying rotations that is neglected in the currently used thermodynamic framework. This thermodynamic framework is suitable for isotropic, homogeneous solid matter such as thermoelastic and thermoviscoelastic solid continua with and without memory when the deformation is small. The paper also presents preliminary material helpful in consideration of the constitutive theories for polar continua

Composition of Near-Earth Asteroid 2008 EV5: Potential target for Robotic and Human Exploration

We observed potentially hazardous asteroid (PHA) 2008 EV5 in the visible (0.30-0.92 microns) and near-IR (0.75-2.5 microns) wavelengths to determine its surface composition. This asteroid is especially interesting because it is a potential target for two sample return mission proposals (Marco Polo-R and Hayabusa-2) and human exploration due to its low delta-v for rendezvous. The spectrum of 2008 EV5 is essentially featureless with exception of a weak 0.48-microns spin-forbidden Fe3+ absorption band. The spectrum also has an overall blue slope. The albedo of 2008 EV5 remains uncertain with a lower limit at 0.05 and a higher end at 0.20 based on thermal modeling. The Busch et al. (2011) albedo estimate of 0.12 is consistent with our thermal modeling results. The albedo and composition of 2008 EV5 are also consistent with a C-type taxonomic classification (Somers et al. 2008). The best spectral match is with CI carbonaceous chondrites similar to Orgueil, which also have a weak 0.48-microns feature and an overall blue slope. This 0.48-microns feature is also seen in the spectrum of magnetite. The albedo of CI chondrites is at the lower limit of our estimated range for the albedo of 2008 EV5.Comment: Pages: 19 Figures: 6 Tables:

Dynamic Properties of Municipal Solid Waste in a Bioreactor Cell at Orchard Hills Landfill, Illinois, USA

Bioreactor landfills enhance municipal solid waste (MSW) degradation through recirculation of leachate inside the waste mass. In-situ monitoring of moisture distribution and changes in mechanical properties (stiffness) of MSW is needed to optimize the safe and effective operation of bioreactor landfills. Geophysical methods, such as electrical resistivity tomography, are shown to have great potential to monitor the moisture distribution. This study is aimed at investigating seismic surveys to characterize changes in dynamic properties (e.g., shear wave velocity and Poisson’s ratio) of MSW to infer the extent of degradation and provide the input needed for seismic stability evaluation. To achieve this goal, a seismic survey was performed in a bioreactor cell, within a MSW landfill (Orchard Hills Landfill, 15 km south of Rockford, Illinois, USA), to image seismic velocity structure and the Poisson’s ratio of MSW. Seismic data were collected through the cell using “fan shot” direct P- (compressional) and S- (shear) wave surveys. The fan shot surveys employed a sledgehammer source on one side of the landfill and geophones on the opposite side, thus exploiting the landfill’s topography and geometry to image MSW to a depth of at least 10 m. P- and S- wave velocity tomographic models from these direct-wave (through-pile) raypaths indicated a dramatic velocity increase below 5 m depth, perhaps indicating consolidation and compaction of MSW. Shear-wave velocity ranged from 150 m/s to 170 m/s. The P/S ratio ranged from 1.8 to 3.7, with an average of about 2.7 and Poisson ratios ranged from 0.29 to 0.46, with an average value of 0.42 (standard deviation 0.024). Below 4-5 m depth, compressional-wave seismic refraction profiling also indicates a subtle change in velocity. Repeated electromagnetic (EM) conductivity measurements with maximum sensitivity at 10 m depth show conductivity increased in the MSW approximately 20-40 mS/m over a 14 month period. Conditions appear to be more uniform at depth as well, after this 14-month interval. Overall, this study showed that seismic and EM surveys have potential to monitor spatial and temporal variation of dynamic properties of MSW and infer the extent of degradation

Asteroid (354) Eleonora: Plucking an odd duck

During a survey of the S-type asteroids, Gaffey et al. (Gaffey, M.J., Bell, J.F., Brown, R.H., Burbine, T.H., Piatek, J., Reed, K.L., Chaky, D.A. [1993]. Icarus 106, 573–602) identified Asteroid (354) Eleonora as anomalous with a 1 μm absorption feature ∼2.5 times stronger than any S-asteroid of comparable size. Subsequent investigation revealed significant differences in the 1 μm absorption feature between the visible & very near-infrared CCD spectra (λ \u3c ∼1.0 μm) and other spectral data sets for this asteroid. There were also significant spectral differences among the several CCD survey spectra (SMASS-I, SMASS-II & S3OS2) of Eleonora. These differences could potentially arise from spectral variations across the asteroid surface, from observational phase angle differences, from surface temperature differences, from viewing geometry for a nonspherical body, or from the use of standard stars with deviated to different degrees from a true solar standard. In June 2011 Asteroid (354) Eleonora was observed over two nights using the NASA Infrared Telescope Facility (IRTF) at Mauna Kea Observatory in order to test these possible scenarios and to better understand the nature and history of Eleonora and its relationships to other asteroids and to the meteorites. Analysis of this data set has eliminated the following options as the cause of the differences in the 1 μm absorption feature within the CCD data sets and between the CCD data sets and the other spectral data: (1) rotational spectral variations; (2) variation in surface composition with latitude; (3) observation phase; (4) surface temperature variations with differing heliocentric distance in the asteroid’s elliptical orbit; (5) spectral effects of viewing geometry for a nonspherical body; and (6) differences in spectral standard stars. We conclude that none of the CCD spectra of (354) Eleonora are reliable, and that within the limits of their spectral coverage, analyses of the three CCD spectra would produce significantly different – and generally unreliable – indications of surface mineralogy. An effort needs to be made to determine whether “bad” CCD spectra are rare with the case of (354) Eleonora being an uncommon occurrence or whether there is a broader problem with the CCD asteroid survey data sets, and if so, how to identify the “bad” spectra. While CCD survey spectra show apparently irreconcilable differences, the near-infrared spectra of (354) Eleonora from various observers show only minor differences, primarily in the overall spectral slope, most of which can be attributed to slight differences in the standard stars used to calibrate the data. In June 2011, 226 near-infrared (∼0.76–2.5 μm) spectra of (354) Eleonora were obtained using the SpeX instrument on the NASA Infrared Telescope Facility at Mauna Kea Observatory. These spectra were consistent with the six sets of NIR spectra obtained for Eleonora by previous observers. The primary variation observed in this new data set was an approximately 10% variation in spectral slope between ∼0.8 μm and ∼1.6 μm during the rotation period of the asteroid. Mineralogically diagnostic spectral parameters extracted from this new data are most consistent with a surface assemblage of fine-grained intimately mixed olivine (∼60–70%, ∼Fo61–71) and low nickel (\u3c∼7–8% Ni) NiFe metal. The Fo estimate is consistent with previous estimates (Fo66±5) by Sanchez et al. (Sanchez, J.A., Reddy, V., Kelley, M.S., Cloutis, E.A., Bottke, W.F., Nesvorný, D., Lucas, M.P., Hardersen, P.S., Gaffey, M.J., Abell, P.A., Le Corre, L. [2014]. Icarus 228, 288–300), but not with the estimate (∼Fo90) of Sunshine et al. (Sunshine, J.M., Bus, S.J., Corrigan, C.M., McCoy, T.J., Burbine, T.H. [2007]. Meteorit. Planet. Sci. 42, 155–170). The surface assemblage appears to contain a small component (∼8–10%) of igneous pyroxene (weakly constrained at ∼Fs50Wo10). The parent lithology of the surface regolith may be similar to a pallasite assemblage, although none of the three known types of pallasites are good mineralogical matches

The virtual pedagogy initiative

Contemporary Higher Education Institutions must adapt to address government funded calls for expansion and widened participation. The adoption of e-learning strategies, such as the use of the podcasts, can facilitate flexible learning around the needs and expectations of students. In this article we outline a number of e-learning developments at Aston University collectively referred to as the Virtual Pedagogy Initiative. Each of the strands, podcasts, vodcasts, mobile telephony and the campus wide remote broadcasts, are described pedagogically as well as technically. Where possible data highlighting the student response and experience are included. The article begins with the contention that contemporary undergraduates may be qualitatively different and can considered „digital natives?