Stochastic analysis of global traveltime data: mantle heterogeneity and random errors in the ISC data

Analysis of global traveltime data has been formulated in terms of the stochastic properties of the Earth's heterogeneity pattern and random errors in the data. The formalism relates the coherency of traveltime residuals within bundles of rays (summary rays) of varying size to the spherical harmonic power spectrum of the slowness field of the medium. It has been applied to mantle P-wave data from the ISC catalogue. The measure of coherency is the variance within summary rays. It is estimated within bins in source depth, epicentral distance and the scale size of the area defining a summary ray. The variance at infinitesimal scale length represents the incoherent component of the data (random errors). The variation of the variance with scale length contains information about the autocorrelation function or power spectrum of slowness perturbations within the Earth. The variation with epicentral distance reflects the depth variation of the spectrum. The formalism accounts for the uneven distribution (clustering) of stations and events. We find that estimates of random errors correlate well with complexities on the traveltime curve of P-waves. The variance peaks at 1.0–2.0 s^2 at Δ ≈ 20°, where triplications occur on the traveltime curve, drops to 0.15–0.8s^2 at teleseismic distances, and rises to 0.4–1.3 s^2 approaching the core shadow, where the traveltime curves of P-waves and PcP-waves merge. These estimates should be considered upper bounds for the random error variance of the data. The signal to random noise ratio in the teleseismic ISC P-wave data is about S/N ≈ 2. Inversion of the scale-dependent structural signal in the data yields models that concentrate heterogeneity strongly in the upper mantle. The product of correlation length and power drops by about two orders of magnitude from the surface of the Earth to the lower mantle. About half of this quantity in the upper mantle is due to small-scale features (<300km). The lower mantle is devoid of small-scale structure. It contains 0.1 per cent velocity variations at a characteristic scale of about 1000km. This corresponds to a spectral band-width of l ≈ 7. The D″ layer at the bottom 100–200 km of the mantle shows up as a distinct layer in our results. It has 0.3 per cent velocity variations at a characteristic scale of 350km. The top of the lower mantle contains 0.3 per cent velocity variations on a scale of 500km and also contains some small-scale power. These results are compatible with previous deterministic lower mantle studies, although some details differ. The strength of heterogeneity in the upper mantle may obscure attempts to model the Earth's deep interior

Magnetization in short-period mesoscopic electron systems

We calculate the magnetization of the two-dimensional electron gas in a short-period lateral superlattice, with the Coulomb interaction included in Hartree and Hartree-Fock approximations. We compare the results for a finite, mesoscopic system modulated by a periodic potential, with the results for the infinite periodic system. In addition to the expected strong exchange effects, the size of the system, the type and the strength of the lateral modulation leave their fingerprints on the magnetization.Comment: RevTeX4, 10 pages with 14 included postscript figures To be published in PRB. Replaced to repair figure

Orbital current mode in elliptical quantum dots

An orbital current mode peculiar to deformed quantum dots is theoretically investigated; first by using a simple model that allows to interpret analytically its main characteristics, and second, by numerically solving the microscopic equations of time evolution after an initial perturbation within the time-dependent local-spin-density approximation. Results for different deformations and sizes are shown.Comment: 4 REVTEX pages, 4 PDF figures, accepted in PRB:R

High-quality genome-scale metabolic modelling of \u3ci\u3ePseudomonas putida\u3c/i\u3e highlights its broad metabolic capabilities

Genome-scale reconstructions of metabolism are computational species-specific knowledge bases able to compute systemic metabolic properties. We present a comprehensive and validated reconstruction of the biotechnologically relevant bacterium Pseudomonas putida KT2440 that greatly expands computable predictions of its metabolic states. The reconstruction represents a significant reactome expansion over available reconstructed bacterial metabolic networks. Specifically, iJN1462 (i) incorporates several hundred additional genes and associated reactions resulting in new predictive capabilities, including new nutrients supporting growth; (ii) was validated by in vivo growth screens that included previously untested carbon (48) and nitrogen (41) sources; (iii) yielded gene essentiality predictions showing large accuracy when compared with a knock-out library and Bar-seq data; and (iv) allowed mapping of its network to 82 P. putida sequenced strains revealing functional core that reflect the large metabolic versatility of this species, including aromatic compounds derived from lignin. Thus, this study provides a thoroughly updated metabolic reconstruction and new computable phenotypes for P. putida, which can be leveraged as a first step toward understanding the pan metabolic capabilities of Pseudomonas

Lens magnification by CL0024+1654 in the U and R band

[ABRIDGED] We estimate the total mass distribution of the galaxy cluster CL0024+1654 from the measured source depletion due to lens magnification in the R band. Within a radius of 0.54Mpc/h, a total projected mass of (8.1+/-3.2)*10^14 M_sol/h (EdS) is measured, which corresponds to a mass- to-light ratio of M/L(B)=470+/-180. We compute the luminosity function of CL0024+1654 in order to estimate contamination of the background source counts from cluster galaxies. Three different magnification-based reconstruction methods are employed using both local and non-local techniques. We have modified the standard single power-law slope number count theory to incorporate a break and applied this to our observations. Fitting analytical magnification profiles of different cluster models to the observed number counts, we find that the cluster is best described either by a NFW model with scale radius r_s=334+/-191 kpc/h and normalisation kappa_s=0.23+/-0.08 or a power-law profile with slope xi=0.61+/-0.11, central surface mass density kappa_0=1.52+/-0.20 and assuming a core radius of r_core=35 kpc/h. The NFW model predicts that the cumulative projected mass contained within a radius R scales as M(<R)=2.9*10^14*(R/1')^[1.3-0.5lg (R/1')] M_sol/h. Finally, we have exploited the fact that flux magnification effectively enables us to probe deeper than the physical limiting magnitude of our observations in searching for a change of slope in the U band number counts. We rule out both a total flattening of the counts with a break up to U_AB<=26.6 and a change of slope, reported by some studies, from dlog N/dm=0.4->0.15 up to U_AB<=26.4 with 95% confidence.Comment: 19 pages, 12 figures, submitted to A&A. New version includes more robust U band break analysis and contamination estimates, plus new plot

SB7-21/22: Resolution Establishing ASUM\u27s Demands Regarding COVID-19 Vaccine Requirement

SB7-21/22: Resolution Establishing ASUM\u27s Demands Regarding COVID-19 Vaccine Requirement. This resolution passed on a 16Y-2N-0A vote during the September 8, 2021 meeting of the Associated Students of the University of Montana (ASUM)

Memorization of short-range potential fluctuations in Landau levels

We calculate energy spectra of a two-dimensional electron system in a perpendicular magnetic field and periodic potentials of short periods. The Coulomb interaction is included within a screened Hartree-Fock approximation. The electrostatic screening is poor and the exchange interaction amplifies the energy dispersion. We obtain, by numerical iterations, self-consistent solutions that have a hysteresis-like property. With increasing amplitude of the external potential the energy dispersion and the electron density become periodic, and they remain stable when the external potential is reduced to zero. We explain this property in physical terms and speculate that a real system could memorize short-range potential fluctuations after the potential has been turned off.Comment: 11 pages with 4 included figures, Revte

Asymptotically exact dispersion relations for collective modes in a confined charged Fermi liquid

Using general local conservations laws we derive dispersion relations for edge modes in a slab of electron liquid confined by a symmetric potential. The dispersion relations are exact up to $\lambda^{2} q^{2}$, where $q$ is a wave vector and $\lambda$ is an effective screening length. For a harmonic external potential the dispersion relations are expressed in terms of the {\em exact} static pressure and dynamic shear modulus of a homogeneous liquid with the density taken at the slab core. We also derive a simple expression for the frequency shift of the dipole (Kohn) modes in nearly parabolic quantum dots in a magnetic field.Comment: RevTeX4, 4 pages. Revised version with new results on quantum qots and wires. Published in Phys.Rev.

Geometrical effects and signal delay in time-dependent transport at the nanoscale

The nonstationary and steady-state transport through a mesoscopic sample connected to particle reservoirs via time-dependent barriers is investigated within the reduced density operator method. The generalized Master equation is solved via the Crank-Nicolson algorithm by taking into account the memory kernel which embodies the non-Markovian effects that are commonly disregarded. We propose a physically reasonable model for the lead-sample coupling which takes into account the match between the energy of the incident electrons and the levels of the isolated sample, as well as their overlap at the contacts. Using a tight-binding description of the system we investigate the effects induced in the transient current by the spectral structure of the sample and by the localization properties of its eigenfunctions. In strong magnetic fields the transient currents propagate along edge states. The behavior of populations and coherences is discussed, as well as their connection to the tunneling processes that are relevant for transport.Comment: 26 pages, 13 figures. To appear in New Journal of Physic