A theory of linear estimation

Theory of linear estimation and applicability to problems of smoothing, filtering, extrapolation, and nonlinear estimatio

Towards a generalized theory of low-frequency sound source localization

Low-frequency sound source localization generates considerable amount of disagreement between audio/acoustics researchers, with some arguing that below a certain frequency humans cannot localize a source with others insisting that in certain cases localization is possible, even down to the lowest audible of frequencies. Nearly all previous work in this area depends on subjective evaluations to formulate theorems for low-frequency localization. This, of course, opens the argument of data reliability, a critical factor that may go some way to explain the reported ambiguities with regard to low-frequency localization. The resulting proposal stipulates that low-frequency source localization is highly dependent on room dimensions, source/listener location and absorptive properties. In some cases, a source can be accurately localized down to the lowest audible of frequencies, while in other situations it cannot. This is relevant as the standard procedure in live sound reinforcement, cinema sound and home-theater surround sound is to have a single mono channel for the low-frequency content, based on the assumption that human’s cannot determine direction in this band. This work takes the first steps towards showing that this may not be a universally valid simplification and that certain sound reproduction systems may actually benefit from directional low-frequency content

Transient microbiota exposures activate dormant Escherichia coli infection in the bladder and drive severe outcomes of recurrent disease

Pathogens often inhabit the body asymptomatically, emerging to cause disease in response to unknown triggers. In the bladder, latent intracellular Escherichia coli reservoirs are regarded as likely origins of recurrent urinary tract infection (rUTI), a problem affecting millions of women worldwide. However, clinically plausible triggers that activate these reservoirs are unknown. Clinical studies suggest that the composition of a woman's vaginal microbiota influences her susceptibility to rUTI, but the mechanisms behind these associations are unclear. Several lines of evidence suggest that the urinary tract is routinely exposed to vaginal bacteria, including Gardnerella vaginalis, a dominant member of the vaginal microbiota in some women. Using a mouse model, we show that bladder exposure to G. vaginalis triggers E. coli egress from latent bladder reservoirs and enhances the potential for life-threatening outcomes of the resulting E. coli rUTI. Transient G. vaginalis exposures were sufficient to cause bladder epithelial apoptosis and exfoliation and interleukin-1-receptor-mediated kidney injury, which persisted after G. vaginalis clearance from the urinary tract. These results support a broader view of UTI pathogenesis in which disease can be driven by short-lived but powerful urinary tract exposures to vaginal bacteria that are themselves not "uropathogenic" in the classic sense. This "covert pathogenesis" paradigm may apply to other latent infections, (e.g., tuberculosis), or for diseases currently defined as noninfectious because routine culture fails to detect microbes of recognized significance

Reduced-order models of the Martian atmospheric dynamics

In this paper we explore the possibility of deriving low-dimensional models of the dynamics of the Martian atmosphere. The analysis consists of a Proper Orthogonal Decomposition (POD) of the atmospheric streamfunction after first decomposing the vertical structure with a set of eigenmodes. The vertical modes were obtained from the quasi-geostrophic vertical structure equation. The empirical orthogonal functions (EOFs) were optimized to represent the atmospheric total energy. The total energy was used as the criterion to retain those modes with large energy content and discard the rest. The principal components (PCs) were analysed by means of Fourier analysis, so that the dominant frequencies could be identified. It was possible to observe the strong influence of the diurnal cycle and to identify the motion and vacillation of baroclinic waves

Teleconnection in the martian atmosphere during the 2001 planet-encircling dust storm

Introduction: In July 2001 (Martian year 25), Mars was enshrouded by a thick veil of dust which lasted for several months and obscured the observation of its surface to spacecraft cameras and ground-based telescopes. The emergence and rapid evolution (within a few days) of multiple, isolated, regional dust storms which eventually attained planetary scale extent were observed by NASA’s Mars Global Surveyor (MGS) spacecraft using high resolution camera images and the thermal profiles and dust opacity measurements pro-vided by the Thermal Emission Spectrometer (TES) [1, 2]. We have applied a technique used in Terrestrial meteorology (sequential data assimilation, [3]) to ob-tain a complete, four-dimensional evolution of all the atmospheric variables during the period of this planet-encircling dust storm, even those which were not di-rectly observed by the MGS satellite, such as surface pressure and winds. We assimilated TES nadir-pointing thermal profiles and total dust opacities in a global circulation model of the Martian atmosphere, developed jointly by the University of Oxford and the Open University in the United Kingdom, with the col-laboration of the Laboratoire de Météorologie Dyna-mique in Paris (UK-MGCM) [4, 5, 6]

A Few More Examples May Be Worth Billions of Parameters

We investigate the dynamics of increasing the number of model parameters versus the number of labeled examples across a wide variety of tasks. Our exploration reveals that while scaling parameters consistently yields performance improvements, the contribution of additional examples highly depends on the task's format. Specifically, in open question answering tasks, enlarging the training set does not improve performance. In contrast, classification, extractive question answering, and multiple choice tasks benefit so much from additional examples that collecting a few hundred examples is often “worth” billions of parameters. We hypothesize that unlike open question answering, which involves recalling specific information, solving strategies for tasks with a more restricted output space transfer across examples, and can therefore be learned with small amounts of labeled data

First mission - towards a global harmonised in-situ data repository for forest biomass datasets validation

Global measurements of forest height, biomass are urgently needed as essential climate and ecosystem variables, but can benefit from greater co-operation between remote sensing (RS) and forest ecological communities. The Forest Observation System - FOS (https://forest-observation-system.net/ [https://forest-observation- system.net/]) is an international cooperation to establish a global in-situ forest biomass database to support earth observation and to encourage investment in relevant field-based observations and science. FOS aims to link the RS community with ecologists who measure forest biomass and estimating biodiversity in the field. The FOS aims to overcome data sharing issues and introduce a standard biomass data flow from tree-level measurement to the plot-level aggregation served in the most suitable form for the RS. Ecologists benefit from the FOS with improved access to global biomass information, data standards, gap identification and potentially improved funding opportunities to address the known gaps and deficiencies in the data. FOS closely collaborate with the CTFS-ForestGEO, the ForestPlots.net (incl. RAfNFOR, AfriTRON and T-FORCES), AusCover, TmFO and the llASA network. FOS is an open initiative with other networks and teams most welcome to join. The online database provides open access for forest plot location, canopy height and above-ground biomass. Plot size is 0.25ha or larger. Comparison of plot biomass data with available global and regional maps (incl. Kindermann et al., 2013; Thurner et al., 2013; Saatchi et al., 2011; Baccini et al., 2012; Avitabile et al., 2016; Hu et al., 2016; Santoro et al., 2018) shows wide range of uncertainties associated with biomass estimation

The Radial Structure of SNR N103B

We report on the results from a Chandra ACIS observation of the young, compact, supernova remnant N103B. The unprecedented spatial resolution of Chandra reveals sub-arcsecond structure, both in the brightness and in spectral variations. Underlying these small-scale variations is a surprisingly simple radial structure in the equivalent widths of the strong Si and S emission lines. We investigate these radial variations through spatially resolved spectroscopy using a plane-parallel, non-equilibrium ionization model with multiple components. The majority of the emission arises from components with a temperature of 1 keV: a fully ionized hydrogen component; a high ionization timescale (n_e*t > 10^12 s cm^-3) component containing Si, S, Ar, Ca, and Fe; and a low ionization timescale (n_e*t ~ 10^{11} s cm^-3) O, Ne, and Mg component. To reproduce the strong Fe Kalpha line, it is necessary to include additional Fe in a hot (> 2 keV), low ionization (n_e*t ~ 10^10.8 s cm^-3) component. This hot Fe may be in the form of hot Fe bubbles, formed in the radioactive decay of clumps of 56Ni. We find no radial variation in the ionization timescales or temperatures of the various components. Rather, the Si and S equivalent widths increase at large radii because these lines, as well as those of Ar and Ca, are formed in a shell occupying the outer half of the remnant. A shell of hot Fe is located interior to this, but there is a large region of overlap between these two shells. In the inner 30% of the remnant, there is a core of cooler, 1 keV Fe. We find that the distribution of the ejecta and the yields of the intermediate mass species are consistent with model prediction for Type Ia events.Comment: 34 pages, including 7 tables and 7 figures, Accepted by Ap

Equilibrium states for the Bose gas

The generating functional of the cyclic representation of the CCR (Canonical Commutation Relations) representation for the thermodynamic limit of the grand canonical ensemble of the free Bose gas with attractive boundary conditions is rigorously computed. We use it to study the condensate localization as a function of the homothety point for the thermodynamic limit using a sequence of growing convex containers. The Kac function is explicitly obtained proving non-equivalence of ensembles in the condensate region in spite of the condensate density being zero locally.Comment: 21 pages, no figure

SN1993J VLBI (I): The Center of the Explosion and a Limit on Anisotropic Expansion

Phase-referenced VLBI observations of supernova 1993J at 24 epochs, from 50 days after shock breakout to the present, allowed us to determine the coordinates of the explosion center relative to the quasi-stationary core of the host galaxy M81 with an accuracy of 45 micro-arcsec, and to determine the nominal proper motion of the geometric center of the radio shell with an accuracy of 9micro-arcsec/yr. The uncertainties correspond to 160 AU for the position and 160 km/s for the proper motion at the distance of the source of 3.63 Mpc. After correcting for the expected galactic proper motion of the supernova around the core of M81 using HI rotation curves, we obtain a peculiar proper motion of the radio shell center of only 320 +/- 160 km/s to the south, which limits any possible one-sided expansion of the shell. We also find that the shell is highly circular, the outer contours in fact being circular to within 3%. Combining our proper motion values with the degree of circular symmetry, we find that the expansion of the shockfront from the explosion center is isotropic to within 5.5% in the plane of the sky. This is a more fundamental result on isotropic expansion than can be derived from the circularity of the images alone. The brightness of the radio shell, however, varies along the ridge and systematically changes with time. The degree of isotropy in the expansion of the shockfront contrasts with the asymmetries and polarization found in optical spectral lines. Asymmetric density distributions in the ejecta or more likely in the circumstellar medium, are favored to reconcile the radio and optical results. We see no sign of any disk-like density distribution of the circumstellar material, with the average axis ratio of the radio shell of SN1993J being less than 1.04.Comment: 21 pages, LaTex + 5 Figures (encapulsated PostScript), Accepted for Publication in the Astrophysical Journa