Toward unified satellite climatology of aerosol properties: Direct comparisons of advanced level 2 aerosol products

The development of a unified satellite climatology of aerosol properties requires accurate quantification and deep understanding of the underlying factors contributing to discrepancies between individual satellite products. In this paper we compare the most recent level 2 results obtained for coincident pixels viewed at essentially the same time by the Moderate Resolution Imaging Spectroradiometer (MODIS) and Multiangle Imaging Spectroradiometer (MISR) instruments flown on the EOS Terra platform. This strategy eliminates potential sampling effects and provides a virtually direct comparison of spatially and temporally collocated MODIS and MISR retrievals. We show that the MODIS and MISR Ångström exponent datasets reveal essentially no correlation. Although the corresponding aerosol optical thickness (AOT) datasets can agree worse than expected over the oceans, still the agreement is often satisfactory. However, the agreement over the land is often poor or even unacceptable. Of the collocated pixels for which there is a MODIS aerosol retrieval, only ∼40% or fewer pixels have a MISR aerosol retrieval, and vice versa. These findings further illustrate the complexity of the problem of aerosol retrievals from satellite observations and indicate that the creation of a meaningful unified MODIS-MISR aerosol climatology will be a nontrivial task.     

Runge–Kutta discontinuous Galerkin method using WENO limiters II: Unstructured meshes

In [J. Qiu, C.-W. Shu, Runge–Kutta discontinuous Galerkin method using WENO limiters, SIAM Journal on Scientific Computing 26 (2005) 907–929], Qiu and Shu investigated using weighted essentially non-oscillatory (WENO) finite volume methodology as limiters for the Runge–Kutta discontinuous Galerkin (RKDG) methods for solving nonlinear hyperbolic conservation law systems on structured meshes. In this continuation paper, we extend the method to solve two-dimensional problems on unstructured meshes, with the goal of obtaining a robust and high order limiting procedure to simultaneously obtain uniform high order accuracy and sharp, nonoscillatory shock transition for RKDG methods. Numerical results are provided to illustrate the behavior of this procedure.     

Measuring quark-gluon-plasma thermalization time with dileptons

We calculate the medium dilepton yield from a quark-gluon plasma which has a time-dependent local momentum-space anisotropy. A phenomenological model for the hard momentum scale, p(hard)(tau), and plasma anisotropy parameter, xi(tau), is constructed which interpolates between longitudinal free streaming at early times (tautau(iso)). We show that high-energy dilepton production is sensitive to the plasma isotropization time, tau(iso), and can therefore be used to experimentally determine the time of onset for hydrodynamic expansion of a quark-gluon plasma and the magnitude of expected early-time momentum-space anisotropies.     

An acoustic analysis of laughter produced by congenitally deaf and normally hearing college students

Relatively few empirical data are available concerning the role of auditory experience in nonverbal human vocal behavior, such as laughter production. This study compared the acoustic properties of laughter in 19 congenitally, bilaterally, and profoundly deaf college students and in 23 normally hearing control participants. Analyses focused on degree of voicing, mouth position, air-flow direction, temporal features, relative amplitude, fundamental frequency, and formant frequencies. Results showed that laughter produced by the deaf participants was fundamentally similar to that produced by the normally hearing individuals, which in turn was consistent with previously reported findings. Finding comparable acoustic properties in the sounds produced by deaf and hearing vocalizers confirms the presumption that laughter is importantly grounded in human biology, and that auditory experience with this vocalization is not necessary for it to emerge in species-typical form. Some differences were found between the laughter of deaf and hearing groups; the most important being that the deaf participants produced lower-amplitude and longer-duration laughs. These discrepancies are likely due to a combination of the physiological and social factors that routinely affect profoundly deaf individuals, including low overall rates of vocal fold use and pressure from the hearing world to suppress spontaneous vocalizations.     

Comparison of tumor histology to dynamic contrast enhanced magnetic resonance imaging-based physiological estimates

Purpose

The purpose of this study was to compare histologically determined cellularity and extracellular space to dynamic contrast-enhanced magnetic resonance imaging (DCE MRI)-based maps of a two-compartment model's parameters describing tumor contrast agent extravasation, specifically tumor extravascular extracellular space (EES) volume fraction (v_e), tumor plasma volume fraction (v_p) and volume-normalized contrast agent transfer rate between tumor plasma and interstitium (K_TRANS/V_T).

Materials and Methods

Obtained v_e, v_p and K_TRANS/V_T maps were estimated from gadolinium diethylenetriamine penta-acetic acid DCE T₁-weighted gradient-echo images at resolutions of 469, 938 and 2500 μm. These parameter maps were compared at each resolution to histologically determined tumor type, and the high-resolution 469-μm maps were compared with automated cell counting using Otsu's method and a color-thresholding method for estimated intracellular (V_{intracellular}) and extracellular (V_{extracellular}) space fractions.

Results

The top five K_TRANS/V_T values obtained from each tumor at 469 and 938 μm resolutions are significantly different from those obtained at 2500 μm (P<.0001) and from one another (P=.0014). Using these top five K_TRANS/V_T values and the corresponding tumor EES volume fractions v_e, we can statistically differentiate invasive ductal carcinomas from noninvasive papillary carcinomas for the 469- and 938-μm resolutions (P=.0017 and P=.0047, respectively), but not for the 2500-μm resolution (P=.9008). The color-thresholding method demonstrated that v_e measured by DCE MRI is statistically similar to histologically determined EES. The V_{extracellular} obtained from the color-thresholding method was statistically similar to the v_e measured with DCE MRI for the top 10 K_TRANS/V_T values (P>.05). DCE MRI-based K_TRANS/V_T estimates are not statistically correlated with histologically determined cellularity.

Conclusion

DCE MRI estimates of tumor physiology are a limited representation of tumor histological features. Extracellular spaces measured by both DCE MRI and microscopic analysis are statistically similar. Tumor typing by DCE MRI is spatial resolution dependent, as lower resolutions average out contributions to voxel-based estimates of K_TRANS/V_T. Thus, an appropriate resolution window is essential for DCE MRI tumor diagnosis. Within this resolution window, the top K_TRANS/V_T values with corresponding v_e are diagnostic for the tumor types analyzed in this study.     

Bayesian estimation of Karplus parameters and torsion angles from three-bond scalar couplings constants

We apply Bayesian inference to analyze three-bond scalar coupling constants in an objective and consistent way. The Karplus curve and a Gaussian error law are used to model scalar coupling measurements. By applying Bayes' theorem, we obtain a probability distribution for all unknowns, i.e., the torsion angles, the Karplus parameters, and the standard deviation of the Gaussian. We infer all these unknowns from scalar coupling data using Markov chain Monte Carlo sampling and analytically derive a probability distribution that only involves the torsion angles.     

Control of flexural waves on a beam using distributed vibration neutralisers

This paper is concerned with the use of distributed vibration neutralisers to control the transmission of flexural waves on a beam. Of particular interest is an array of beam-like neutralisers and a continuous plate-like neutraliser. General expressions for wave transmission and reflection metrics either side of the distributed neutralisers are derived. Based on transmission efficiency, the characteristics of multiple neutralisers are investigated in terms of the minimum transmission efficiency, the normalised bandwidth and the shape factor, allowing optimisation of their performance. Analytical results show that the band-stop property of the neutraliser array depends on various factors, including the neutraliser damping, mass, separation distance in the array and the moment arm of each neutraliser. Moreover, it is found that the particular attachment configuration of an uncoupled force-moment-type neutraliser can be used to improve their overall performance. It is also shown that in the limit of many neutralisers in the array, the performance tends to that of a continuous neutraliser.     

The connection of the nuclear “Coriolis” force with classical mechanics

The relation between the socalled Coriolis couplingI · j, operating in rotating nuclei, and the classical Coriolis force is discussed. The system forces acting in the cranking model for non-uniform rotation and in the rotator-particle model are examined. Differences with the molecular Coriolis coupling are indicated.     

Conformally invariant differential operators on Minkowski space and their curved analogues

This article describes the construction of a natural family of conformally invariant differential operators on a four-dimensional (pseudo-)Riemannian manifold. Included in this family are the usual massless field equations for arbitrary helicity but there are many more besides. The article begins by classifying the invariant operators on flat space. This is a fairly straightforward task in representation theory best solved through the theory of Verma modules. The method generates conformally invariant operators in the curved case by means of Penrose's local twistor transport.S.E.R.C. Advanced Fellow and Flinders University Visiting Research Fellow