On the relationship between inflation persistence and temporal aggregation

This paper examines the impact of temporal aggregation on alternative definitions of inflation persistence. Using the CPI and the core PCE deflator of the US, our results show that temporal aggregation from the monthly to the quarterly to the annual frequency induces persistence in the inflation series.

An adjoint for likelihood maximization

The process of likelihood maximization can be found in many different areas of computational modelling. However, the construction of such models via likelihood maximization requires the solution of a difficult multi-modal optimization problem involving an expensive O(n3) factorization. The optimization techniques used to solve this problem may require many such factorizations and can result in a significant bottle-neck. This article derives an adjoint formulation of the likelihood employed in the construction of a kriging model via reverse algorithmic differentiation. This adjoint is found to calculate the likelihood and all of its derivatives more efficiently than the standard analytical method and can therefore be utilised within a simple local search or within a hybrid global optimization to accelerate convergence and therefore reduce the cost of the likelihood optimization

Localization of response functions of spiral waves in the FitzHugh-Nagumo system

Dynamics of spiral waves in perturbed, e. g. slightly inhomogeneous or subject to a small periodic external force, two-dimensional autowave media can be described asymptotically in terms of Aristotelean dynamics, so that the velocities of the spiral wave drift in space and time are proportional to the forces caused by the perturbation. The forces are defined as a convolution of the perturbation with the spiral's Response Functions, which are eigenfunctions of the adjoint linearised problem. In this paper we find numerically the Response Functions of a spiral wave solution in the classic excitable FitzHugh-Nagumo model, and show that they are effectively localised in the vicinity of the spiral core.Comment: 11 pages, 2 figure

Racial Injustice in Astrid Lindgren’s Kati in America

This article addresses Astrid Lindgren’s Kati in America, which was written in 1950 and translated into English in 1964. The novel reflects Lindgren’s impressions of the United States, where she traveled in 1948 on assignment for the publishing house Åhland and Åkerlund. By chance, the author of this article discovered that there is a fifteenth chapter of the book in the Russian, Polish, French, Spanish, and German translations, but which is missing in the English. This missing chapter describes the racism Lindgren’s protagonist witnesses during her visit to New Orleans. Astrid Lindgren’s depiction of racial injustice in the South is especially relevant in the current era, when the subject of race is so prominent in the national conversation. In light of this fact, it is more important than ever that a new, complete English translation of Kati in America be published, one that reflects the racial injustice to which Astrid Lindgren sought to call her readers’ attention in Chapter 15

The rate of convergence of Euler approximations for solutions of stochastic differential equations driven by fractional Brownian motion

The paper focuses on discrete-type approximations of solutions to non-homogeneous stochastic differential equations (SDEs) involving fractional Brownian motion (fBm). We prove that the rate of convergence for Euler approximations of solutions of pathwise SDEs driven by fBm with Hurst index $H>1/2$ can be estimated by $O(\delta^{2H-1})$ ($\delta$ is the diameter of partition). For discrete-time approximations of Skorohod-type quasilinear equation driven by fBm we prove that the rate of convergence is $O(\delta^H)$.Comment: 21 pages, (incorrect) weak convergence result removed, to appear in Stochastic

The Evolution of the Field and Cluster Morphology-Density Relation for Mass-Selected Samples of Galaxies

The Sloan Digital Sky Survey (SDSS) and photometric/spectroscopic surveys in the GOODS-South field (the Chandra Deep Field-South, CDFS) are used to construct volume-limited, stellar mass-selected samples of galaxies at redshifts 0<z<1. The CDFS sample at 0.6<z<1.0 contains 207 galaxies complete down to M=4x10^10 Msol (for a ``diet'' Salpeter IMF), corresponding to a luminosity limit for red galaxies of M_B=-20.1. The SDSS sample at 0.020<z<0.045 contains 2003 galaxies down to the same mass limit, which corresponds to M_B=-19.3 for red galaxies. Morphologies are determined with an automated method, using the Sersic parameter n and a measure of the residual from the model fits, called ``bumpiness'', to distinguish different morphologies. These classifications are verified with visual classifications. In agreement with previous studies, 65-70% of the galaxies are located on the red sequence, both at z~0.03 and at z~0.8. Similarly, 65-70% of the galaxies have n>2.5. The fraction of E+S0 galaxies is 43+/-3%$ at z~0.03 and 48+/-7% at z~0.8, i.e., it has not changed significantly since z~0.8. When combined with recent results for cluster galaxies in the same redshift range, we find that the morphology-density relation for galaxies more massive than 0.5M* has remained constant since at least z~0.8. This implies that galaxies evolve in mass, morphology and density such that the morphology-density relation does not change. In particular, the decline of star formation activity and the accompanying increase in the stellar mass density of red galaxies since z~1 must happen without large changes in the early-type galaxy fraction in a given environment.Comment: 16 pages, 13 figures, 2 tables. Updated to match journal version. Will appear in ApJ (vol. 670, p. 206

Controls on the spatial distribution of oceanic <i>δ</i>¹³C_DIC

We describe the design and evaluation of a large ensemble of coupled climate–carbon cycle simulations with the Earth system model of intermediate complexity GENIE. This ensemble has been designed for application to a range of carbon cycle questions, including the causes of late- Quaternary fluctuations in atmospheric CO2. Here we evaluate the ensemble by applying it to a transient experiment over the recent industrial era (1858 to 2008 AD). We employ singular vector decomposition and principal component emulation to investigate the spatial modes of ensemble variability of oceanic dissolved inorganic carbon (DIC) δ13C, considering both the spun-up pre-industrial state and the transient change. These analyses allow us to separate the natural (preindustrial) and anthropogenic controls on the δ13CDIC distribution. We apply the same dimensionally reduced emulation techniques to consider the drivers of the spatial uncertainty in anthropogenic DIC. We show that the sources of uncertainty related to the uptake of anthropogenic δ13CDIC and DIC are quite distinct. Uncertainty in anthropogenic δ13C uptake is controlled by air–sea gas exchange, which explains 63% of modelled variance. This mode of variability is largely absent from the ensemble variability in CO2 uptake, which is rather driven by uncertainties in thermocline ventilation rates. Although the need to account for air–sea gas exchange is well known, these results suggest that, to leading order, uncertainties in the ocean uptake of anthropogenic 13C and CO2 are governed by very different processes. This illustrates the difficulties in reconstructing one from the other, and furthermore highlights the need for careful targeting of both δ13CDIC and DIC observations to better constrain the ocean sink of anthropogenic CO2

User Satisfaction with Electronic Reference: A Systematic REview

Purpose – The paper aims to systematically review research that analyzes satisfaction with electronic reference services, paying particular attention to how user satisfaction is measured. The application and value of evidence‐based methodologies for library and information science (LIS) research are explored. Design/methodology/approach – Database searches identified research concerned with electronic reference. Articles with a variable of user satisfaction were extracted and subjected to a critical appraisal. The remaining research was analyzed for similarities, differences, and consistency. Findings – A wide variety of methods are used to measure user satisfaction. There was almost no overlap in specific questions considered although there were some similarities in methodologies used. The results of this analysis show a lack of standardization in LIS research on this topic. Research limitations/implications – There may be some bias in the selection of research in that the reviewers were only able to obtain published findings. The lack of consistency in reporting results further limited the articles eligible for review and precluded a meta‐analysis. Practical implications – By synthesizing the research conducted on this topic, practicing librarians should be able to see patterns in user satisfaction with electronic reference, and become aware of common pitfalls in undertaking user satisfaction assessment. Those conducting or planning LIS research will be able to identify the characteristics of sound research and thorough reporting of results. Originality/value – Systematic review is an underutilized methodology in LIS research. As evidence‐based librarianship gains traction, it will become a more important tool for LIS researchers. The synthesis and analysis of previous research bring together disparate findings and show patterns and/or differences in providing these services, and brings into focus the lack of consistency in LIS research on this topic