Stochastic models underlying Croston's method for intermittent demand forecasting

Intermittent demand commonly occurs with inventory data, with many time periods having no demand and small demand in the other periods. Croston's method is a widely used procedure for intermittent demand forecasting. However, it is an ad hoc method with no properly formulated underlying stochastic model. In this paper, we explore possible models underlying Croston's method and three related methods, and we show that any underlying model will be inconsistent with the properties of intermittent demand data. However, we find that the point forecasts and prediction intervals based on such underlying models may still be useful.Croston's method, exponential smoothing, forecasting, intermittent demand.

Glider Development in Germany : a Technical Survey of Progress in Design in Germany Since 1922

This report is a recounting of glider development beginning with the "Vampyr" on up to the present day

Genome-wide association study for non-normally distributed traits: A case study for stalk lodging in maize

The abundance of new genomic information available has increased the ability of computational tools to study the genetic basis of agricultural traits, notably with the application of the Genome-Wide Association Study (GWAS). A limitation of GWAS is that the assumptions underlying the linear model typically used to conduct the analysis are often violated in nature, and in such cases, the linear model is inappropriate to use. Alternatively, the mixed logistic regression model is well-suited for a genome-wide association study of binomially distributed agronomic traits because it can include fixed and random effects that account for spurious associations. However, the computational burden associated with fitting this model renders it inefficient to use at every genetic marker that are analyzed in the genome-wide association study.Therefore, the purpose of this work was to assess the ability of simpler statistical models to identify promising subsets of genome-wide markers to apply to the mixed logistic regression model. We tested this approach on stalk lodging, a binomially distributed trait measured on a maize (Zea mays L.) diversity panel. This analysis culminated in the mixed logistic regression model identifying genomic regions coinciding with signals associated with closely related quantitative traits. Using genomic data from the same panel, we conducted a simulation study to determine which parameters of the binomial distribution most likely contribute to the detection of quantitative trait nucleotides. The results suggest that the discovery of such signals is maximized when the probability of a successful Bernoulli trial is 0.5. Based on our findings, we present an analytical framework that involves phenotyping binomially distributed traits so that the possibility of identifying associated markers is maximized and then prioritizes subsets of genome-wide markers for fitting the mixed logistic regression model; such prioritization should make it practical to use the mixed logistic regression model to test for marker-trait associations on an average computer

Resonance-enhanced multiphoton ionization spectroscopy oflaser-ablated copper atoms

Resonance-enhanced multiphoton ionization (REMPI) spectra of laser-ablated copper atoms entrainedin a supersonic free jet expansion are reported. Depending on the ionization scheme employed, andthe conditions under which the copper atoms are produced, very different spectra are produced, whichare discussed. In some circumstances, high proportions of metastable atoms survive the ablation andexpansion process and are clearly seen in the spectra. The spectroscopic transitions for the observedlines are identified, and it is noted that some caution is merited in the assumption that only ground statecopper atoms are present following laser ablation

Characterization of anomalous Zeeman patterns in complex atomic spectra

The modeling of complex atomic spectra is a difficult task, due to the huge number of levels and lines involved. In the presence of a magnetic field, the computation becomes even more difficult. The anomalous Zeeman pattern is a superposition of many absorption or emission profiles with different Zeeman relative strengths, shifts, widths, asymmetries and sharpnesses. We propose a statistical approach to study the effect of a magnetic field on the broadening of spectral lines and transition arrays in atomic spectra. In this model, the sigma and pi profiles are described using the moments of the Zeeman components, which depend on quantum numbers and Land\'{e} factors. A graphical calculation of these moments, together with a statistical modeling of Zeeman profiles as expansions in terms of Hermite polynomials are presented. It is shown that the procedure is more efficient, in terms of convergence and validity range, than the Taylor-series expansion in powers of the magnetic field which was suggested in the past. Finally, a simple approximate method to estimate the contribution of a magnetic field to the width of transition arrays is proposed. It relies on our recently published recursive technique for the numbering of LS-terms of an arbitrary configuration.Comment: submitted to Physical Review

PTPN22 R620W minor allele is a genetic risk factor for giant cell arteritis

Published online 7 April 2016.Giant cell arteritis (GCA) is one of the commonest forms of vasculitis in the elderly, and may result in blindness and stroke. The pathogenesis of GCA is not understood, although environmental, infectious and genetic risk factors are implicated. One gene of interest is PTPN22, encoding lymphoid protein tyrosine phosphatase (Lyp), expressed exclusively in immune cells, which is proposed to be an 'archetypal non-HLA autoimmunity gene'. The minor allele of a functional PTPN22 single nucleotide polymorphism (rs2476601, R620W), which disrupts an interaction motif in the protein, was originally reported to be associated with biopsy-proven GCA in Spanish patients, with supporting data from three replicate Northern European studies. Recently, this observation was extended with additional patients and controls, and studies encompassing European, Scandinavian, UK and American patients. The aim of our study was to determine the association between PTPN22 rs2476601 (R620W) and biopsy-proven GCA in an Australian case cohort.Susan Lester, Alex W Hewitt, Carlee D Ruediger, Linda Bradbury, Elisabeth De Smit, Michael D Wiese, Rachel Black, Andrew Harrison, Graeme Jones, Geoffrey O Littlejohn, Tony R Merriman, Bain Shenstone, Malcolm D Smith, Maureen Rischmueller, Matthew A Brown, Catherine L Hil

From Majorana theory of atomic autoionization to Feshbach resonances in high temperature superconductors

The Ettore Majorana paper - Theory of incomplete P triplets- published in 1931, focuses on the role of selection rules for the non-radiative decay of two electron excitations in atomic spectra, involving the configuration interaction between discrete and continuum channels. This work is a key step for understanding the 1935 work of Ugo Fano on the asymmetric lineshape of two electron excitations and the 1958 Herman Feshbach paper on the shape resonances in nuclear scattering arising from configuration interaction between many different scattering channels. The Feshbach resonances are today of high scientific interest in many different fields and in particular for ultracold gases and high Tc superconductivity.Comment: 13 pages, 7 figures. Journal of Superconductivity and Novel Magnetism to be publishe