Regression-based seasonal unit root tests

The contribution of this paper is three-fold. Firstly, a characterisation theorem of the sub-hypotheses comprising the seasonal unit root hypothesis is presented which provides a precise formulation of the alternative hypotheses against which regression-based seasonal unit root tests test. Secondly, it proposes regressionbased tests for the seasonal unit root hypothesis which allow a general seasonal aspect for the data and are similar both exactly and asymptotically with respect to initial values and seasonal drift parameters. Thirdly, limiting distribution theory is given for these statistics where, in contrast to previous papers in the literature, in doing so it is not assumed that unit roots hold at all of the zero and seasonal frequencies. This is shown to alter the large sample null distribution theory for regression t-statistics for unit roots at the complex frequencies, but interestingly to not affect the limiting null distributions of the regression t-statistics for unit roots at the zero and Nyquist frequencies and regression Fstatistics for unit roots at the complex frequencies. Our results therefore have important implications for how tests of the seasonal unit root hypothesis should be conducted in practice. Associated simulation evidence on the size and power properties of the statistics presented in this paper is given which is consonant with the predictions from the large sample theory.Seasonal unit root tests; seasonal drifts; characterisation theorem

Bottomâ up vs reactive sintering of Al2O3â YAGâ YSZ composites via one or threeâ phase nanoparticles (NPs). Bottomâ up processing wins this time

The bottomâ up approach describes the synthesis of bulk materials from the finest possible length scales to obtain the best global properties. This approach was adapted to the synthesis of multiâ phase ceramic composites produced from metal oxides produced by liquidâ feed flame spray pyrolysis (LFâ FSP). The effect of length scale of mixing was tested through two processing schemes, mixed single metalâ oxide nanopowders (NPs) and nanocomposite NPs having the desired composition within single particles. For the Al2O3â Y2O3â ZrO2 ternary system, composites prepared from nanostructured nanoparticles sinter to finer grain sizes (<410 nm) at equivalent densities of 95%TD than those prepared from mixed nanoparticle processing. These contrast with our previous studies in this area where mixed NP processing gave the best or equivalent results. The nanocomposite NPs produced in this study exhibit novel nanostructures with three phases contained within single particles <26 nm average particle size (APS). This nanostructure may directly explain the enhanced sintering of the nanocomposite NPs and may provide an impetus for future synthesis of similarly structured NPs.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137592/1/jace14761.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137592/2/jace14761_am.pd

Processing YAG/뱉 Al2O3 composites via reactive sintering Y2O3/Al2O3 NP mixtures. A superior alternative to bottom up processing using atomically mixed YAlOx NPs

This effort contrasts â bottomâ upâ processing of YAG/αâ Al2O3 composites where both elements (as 40â 50 nm APSs nanopowders) are present at close to atomic mixing with reactive sintering where ballâ milled mixtures of the individual nanopowders (40â 50 nm APSs) give uniform elemental mixing at length scales closer to 100â 800 nm with correspondingly much longer diffusion distances. In contrast to expectations, densification with control of final grain sizes is best effected using reactive sintering. Thus, reactive sintering to densities â ¥95% occurs at only 1500°C with final grain sizes of â 1000 nm for all samples. In contrast â bottom upâ processing to â ¥95% densities is only achieved at 1600°C, and with final grain sizes of 1700 nm. The reason for this unexpected behavior is that YAG phase forms early in the bottom up approach greatly inhibiting diffusion promoted densification. In contrast, in reactive sintering, YAG is prevented from forming because of the longer diffusion distances such that densification occurs prior to full conversion of the Y2O3 component to YAG. The found hardness values are statistically superior to literature values for composites near the known eutectic composition. In an accompanying paper, the addition of a third component reverses this behavior.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138233/1/jace14980_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138233/2/jace14980.pd

A Subaru Weak Lensing Survey I: Cluster Candidates and Spectroscopic Verification

We present the results of an ongoing weak lensing survey conducted with the Subaru telescope whose initial goal is to locate and study the distribution of shear-selected structures or halos. Using a Suprime-cam imaging survey spanning 21.82 square degree, we present a catalog of 100 candidate halos located from lensing convergence maps. Our sample is reliably drawn from that subset of our survey area, (totaling 16.72 square degree) uncontaminated by bright stars and edge effects and limited at a convergence signal to noise ratio of 3.69. To validate the sample detailed spectroscopic measures have been made for 26 candidates using the Subaru multi-object spectrograph, FOCAS. All are confirmed as clusters of galaxies but two arise as the superposition of multiple clusters viewed along the line of sight. Including data available in the literature and an ongoing Keck spectroscopic campaign, a total of 41 halos now have reliable redshifts. For one of our survey fields, the XMM LSS (Pierre et al. 2004) field, we compare our lensing-selected halo catalog with its X-ray equivalent. Of 15 halos detected in the XMM-LSS field, 10 match with published X-ray selected clusters and a further 2 are newly-detected and spectroscopically confirmed in this work. Although three halos have not yet been confirmed, the high success rate within the XMM-LSS field (12/15) confirms that weak lensing provides a reliable method for constructing cluster catalogs, irrespective of the nature of the constituent galaxies or the intracluster medium.Comment: To appear in ApJ, High resolution preprint available at http://anela.mtk.nao.ac.jp/suprime33/papers/p1.ps.g

Phase Evolution in the Transformation of Atomically Mixed Versus Ball‐Milled Mixtures of Nanopowders in the Formation of Composite MO·3Al 2 O 3 Spinels: Bottom‐Up Processing is Not Always Optimal

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109657/1/jace13160.pd

Accretion discs models with the "beta"-viscosity prescription derived from laboratory experiments

We examine under which conditions one may apply, to steady state keplerian accretion discs, the "beta"-viscosity prescription which has been derived from rotating shear flow experiments (Richard & Zahn 1999). Using a vertically averaged model, we show that this law may be suitable for all three families of known systems: in young stellar objects, evolved binary stars and Active Galactic Nuclei discs (except in their outer gas pressure dominated regions where turbulence becomes hypersonic). According to the standard criterion for viscous stability, "beta"-discs are always stable throughout. Using realistic opacities and equation of state, we demonstrate that these discs are thermally unstable in the temperature domain where hydrogen recombines, when they are optically thick, and this could lead to limit cycle behavior. Radiation pressure dominated regions are thermally stable, in contrast with "alpha"-discs. This results in a fully stable solution for the innermost parts of AGN discs.Comment: 8 pages, PostScript. accepted in Astron. & Astrophy

Operation Moshtarak and the manufacture of credible, “heroic” warfare

Richard Lance Keeble argues that Fleet Street’s coverage of the Afghan conflict has served largely to promote the interests of the military/industrial/media complex – and marginalise the views of the public who have consistently appealed in polls for the troops to be brought back hom

A library of logic models to explain how interventions to reduce diagnostic error work

OBJECTIVES: We aimed to create a library of logic models for interventions to reduce diagnostic error. This library can be used by those developing, implementing, or evaluating an intervention to improve patient care, to understand what needs to happen, and in what order, if the intervention is to be effective. METHODS: To create the library, we modified an existing method for generating logic models. The following five ordered activities to include in each model were defined: preintervention; implementation of the intervention; postimplementation, but before the immediate outcome can occur; the immediate outcome (usually behavior change); and postimmediate outcome, but before a reduction in diagnostic errors can occur. We also included reasons for lack of progress through the model. Relevant information was extracted about existing evaluations of interventions to reduce diagnostic error, identified by updating a previous systematic review. RESULTS: Data were synthesized to create logic models for four types of intervention, addressing five causes of diagnostic error in seven stages in the diagnostic pathway. In total, 46 interventions from 43 studies were included and 24 different logic models were generated. CONCLUSIONS: We used a novel approach to create a freely available library of logic models. The models highlight the importance of attending to what needs to occur before and after intervention delivery if the intervention is to be effective. Our work provides a useful starting point for intervention developers, helps evaluators identify intermediate outcomes, and provides a method to enable others to generate libraries for interventions targeting other errors

Analysis of time-to-event for observational studies: Guidance to the use of intensity models

This paper provides guidance for researchers with some mathematical background on the conduct of time-to-event analysis in observational studies based on intensity (hazard) models. Discussions of basic concepts like time axis, event definition and censoring are given. Hazard models are introduced, with special emphasis on the Cox proportional hazards regression model. We provide check lists that may be useful both when fitting the model and assessing its goodness of fit and when interpreting the results. Special attention is paid to how to avoid problems with immortal time bias by introducing time-dependent covariates. We discuss prediction based on hazard models and difficulties when attempting to draw proper causal conclusions from such models. Finally, we present a series of examples where the methods and check lists are exemplified. Computational details and implementation using the freely available R software are documented in Supplementary Material. The paper was prepared as part of the STRATOS initiative.Comment: 28 pages, 12 figures. For associated Supplementary material, see http://publicifsv.sund.ku.dk/~pka/STRATOSTG8

Helium ion microscope – secondary ion mass spectrometry for geological materials

The helium ion microscope (HIM) is a focussed ion beam instrument with unprecedented spatial resolution for secondary electron imaging but has traditionally lacked microanalytical capabilities. With the addition of the secondary ion mass spectrometry (SIMS) attachment, the capabilities of the instrument have expanded to microanalysis of isotopes from Li up to hundreds of atomic mass units, effectively opening up the analysis of all natural and geological systems. However, the instrument has thus far been underutilised by the geosciences community, due in no small part to a lack of a thorough understanding of the quantitative capabilities of the instrument. Li represents an ideal element for an exploration of the instrument as a tool for geological samples, due to its importance for economic geology and a green economy, and the difficult nature of observing Li with traditional microanalytical techniques. Also Li represents a “best-case” scenario for isotopic measurements. Here we present details of sample preparation, instrument sensitivity, theoretical, and measured detection limits for both elemental and isotopic analysis as well as practicalities for geological sample analyses of Li alongside a discussion of potential geological use cases of the HIM–SIMS instrument