Biomass-density data analysis: a comment on Cabaco et al. (2013)

Appropriate use of mathematics and statistics is fundamental for sound interpretations of ecological results and to prevent inaccurate conclusions. Throughout the article by Cabaco etal. (2013) emerge cases of biased data analyses including absence of statistical tests, application of unsuited tests, inconsistent geometrical interpretation of xy data scatter, among others. These biases congregated into incorrect conclusions including (i) reporting a generalized nutrient limitation of seagrass meadows, (ii) proposing the intraspecific biomass-density relation of seaweeds as an ecological indicator, when results report little more than randomness, thus suggesting this relation is unsuited as an ecological indicator; (iii) contradicting general ecological theory without any statistical evidence; and (iv) misassociating their results to the ones by other authors.Synthesis. In order to help ecological researchers pinpoint sources of bias, we point out mistakes related to xy data analysis in Cabaco et al. (2013) that can occur in any subject area and flag others specific to biomass-density relations.info:eu-repo/semantics/publishedVersio

A mixed effect model for bivariate meta-analysis of diagnostic test accuracy studies using a copula representation of the random effects distribution

Diagnostic test accuracy studies typically report the number of true positives, false positives, true negatives and false negatives. There usually exists a negative association between the number of true positives and true negatives, because studies that adopt less stringent criterion for declaring a test positive invoke higher sensitivities and lower specificities. A generalized linear mixed model (GLMM) is currently recommended to synthesize diagnostic test accuracy studies. We propose a copula mixed model for bivariate meta-analysis of diagnostic test accuracy studies. Our general model includes the GLMM as a special case and can also operate on the original scale of sensitivity and specificity. Summary receiver operating characteristic curves are deduced for the proposed model through quantile regression techniques and different characterizations of the bivariate random effects distribution. Our general methodology is demonstrated with an extensive simulation study and illustrated by re-analysing the data of two published meta-analyses. Our study suggests that there can be an improvement on GLMM in fit to data and makes the argument for moving to copula random effects models. Our modelling framework is implemented in the package CopulaREMADA within the open source statistical environment R

A phase one AR/C system design

The Phase One AR&C System Design integrates an evolutionary design based on the legacy of previous mission successes, flight tested components from manned Rendezvous and Proximity Operations (RPO) space programs, and additional AR&C components validated using proven methods. The Phase One system has a modular, open architecture with the standardized interfaces proposed for Space Station Freedom system architecture

Pair Events in Superluminal Optics

When an object moves faster than emissions it creates, it may appear at two positions simultaneously. The appearance or disappearance of this bifurcation is referred to as a pair event. Inherently convolved with superluminal motion, pair events have no subluminal counterparts. Common examples of superluminal motions that exhibit pair events include Cherenkov radiation, sonic booms, illumination fronts from variable light sources, and rotating beams. The minimally simple case of pair events from a single massive object is explored here: uniform linear motion. A pair event is perceived when the radial component of the object's speed toward the observer drops from superluminal to subluminal. Emission from the pair creation event will reach the observer before emission from either of the two images created. Potentially observable image pair events are described for sonic booms and Cherenkov light. To date, no detection of discrete images following a projectile pair event have ever been reported, and so the pair event nature of sonic booms and Cherenkov radiation, for example, remains unconfirmed. Recent advances in modern technology have made such pair event tracking feasible. If measured, pair events could provide important information about object distance and history.Comment: 13 pages, 3 figures. in press: Annalen der Physi

Magnetic Susceptibility: Further Insights into Macroscopic and Microscopic Fields and the Sphere of Lorentz

To make certain quantitative interpretations of spectra from NMR experiments carried out on heterogeneous samples, such as cells and tissues, we must be able to estimate the magnetic and electric fields experienced by the resonant nuclei of atoms in the sample. Here, we analyze the relationships between these fields and the fields obtained by solving the Maxwell equations that describe the bulk properties of the materials present. This analysis separates the contribution to these fields of the molecule in which the atom in question is bonded, the "host" fields, from the contribution of all the other molecules in the system, the "external" fields. We discuss the circumstances under which the latter can be found by determining the macroscopic fields in the sample and then removing the averaged contribution of the host molecule. We demonstrate that the results produced by the, so-called, "sphere of Lorentz" construction are of general validity in both static and time-varying cases. This analytic construct, however, is not "mystical" and its justification rests not on any sphericity in the system but on the local uniformity and isotropy, i.e., spherical symmetry, of the medium when averaged over random microscopic configurations. This local averaging is precisely that which defines the equations that describe the macroscopic fields. Hence, the external microscopic fields, in a suitably averaged sense, can be estimated from the macroscopic fields. We then discuss the calculation of the external fields and that of the resonant nucleus in NMR experiments.Comment: 21 pages, 8 figures, v2: updated to resemble the published versio

Assessment of Five Chilling Tolerance Traits and GWAS Mapping in Rice Using the USDA Mini-Core Collection

Rice (Oryza sativa L.) is often exposed to cool temperatures during spring planting in temperate climates. A better understanding of genetic pathways regulating chilling tolerance will enable breeders to develop varieties with improved tolerance during germination and young seedling stages. To dissect chilling tolerance, five assays were developed; one assay for the germination stage, one assay for the germination and seedling stage, and three for the seedling stage. Based on these assays, five chilling tolerance indices were calculated and assessed using 202 O. sativa accessions from the Rice Mini-Core (RMC) collection. Significant differences between RMC accessions made the five indices suitable for genome-wide association study (GWAS) based quantitative trait loci (QTL) mapping. For young seedling stage indices, japonica and indica subspecies clustered into chilling tolerant and chilling sensitive accessions, respectively, while both subspecies had similar low temperature germinability distributions. Indica subspecies were shown to have chilling acclimation potential. GWAS mapping uncovered 48 QTL at 39 chromosome regions distributed across all 12 rice chromosomes. Interestingly, there was no overlap between the germination and seedling stage QTL. Also, 18 QTL and 32 QTL were in regions discovered in previously reported bi-parental and GWAS based QTL mapping studies, respectively. Two novel low temperature seedling survivability (LTSS)–QTL, qLTSS3-4 and qLTSS4-1, were not in a previously reported QTL region. QTL with strong effect alleles identified in this study will be useful for marker assisted breeding efforts to improve chilling tolerance in rice cultivars and enhance gene discovery for chilling tolerance

Vignette 21: How Ecological Time-Series Inform Response to Stressors

An important part of biodiversity monitoring includes assessing the differences in vulnerability across parts of an ecosystem. Hypoxia is one of the big three climate- related stressors causing biodiversity loss in the oceans. As the ocean warms, its capacity to hold oxygen becomes reduced. At the same time, concurrent shifts in circulation result in changes to how oxygen gets transported from the surface (where oxygen dissolves into the ocean) to the seafloor and from offshore to inshore areas. When a habitat experiences a substantial drop in oxygen, below the point needed to sustain everyday life, animals respond by migrating away, adapting to the new conditions, or dying from suffocation. The key to linking the biodiversity response to the oceanographic change is to simultaneously monitor both because high levels of variability are intrinsic to both sides in the ecology equation

High-frequency bistatic scattering by sub-bottom gas bubbles

Author Posting. © Acoustical Society of America, 1997. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 102 (1997): 806-814, doi:10.1121/1.419906.A previous study of high-frequency acoustic backscattering data collected at Eckernfoerde Bay, Germany revealed that scattering is mainly due to methane gas bubbles buried about a meter beneath the seafloor [Tang et al., J. Acoust. Soc. Am. 96, 2930–2936 (1994)]. A backscattering model was developed [Tang, Geo-Marine Lett. 16, 161–169 (1996)] where the gas bubbles were approximated by oblate spheroids. In this paper, a bistatic scattering model is proposed as an extension of the previously developed backscattering model. In this model, gas bubbles are again assumed to be oblate spheroids with varying aspect ratios and a single-scattering approximation is used. The model is compared to bistatic data acquired in Eckernfoerde Bay, Germany. In particular, the azimuthal dependence of the bistatic scattering strength predicted by the model is tested against experimental data and it is found that both the model and the bistatic scattering strength data exhibit a mild azimuthal dependence. Best agreement between model and data requires a 35% reduction in areal bubble density relative to that used in the backscattering model/data comparison. Possible reasons for this are discussed including multiple scattering effects.This work is supported by the Coastal Benthic Boundary Layer Special Research Program, Office of Navel Research Grant No. N00014-95-1-G904

The chiral phase transition in a random matrix model with molecular correlations

The chiral phase transition of QCD is analyzed in a model combining random matrix elements of the Dirac operator with specially chosen non-random ones. The special form of the latter is motivated by the assumption that the fermionic quasi-zero modes associated with instanton and anti-instanton configurations determine the chiral properties of QCD. Our results show that the degree of correlation between these modes plays the decisive role. To reduce the value of the chiral condensate by more than a factor of 2 about 95 percent of the instantons and anti-instantons must form so-called molecules. This conclusion agrees with numerical results of the Stony Brook group.Comment: published version (minor changes in text and one additional reference, one misprint in published version corrected); 12 pages including 1 figure, LaTeX with elsart.sty and psfig.st

Systems And Methods For Performing Geo-User Content Provision Experiments

Systems, methods, and computer-readable storage media that may be used to conduct geo-user advertising experiments. One method includes determining a set of content items and filtering an activity log based on one or more characteristics of the set of content items to determine a subset of users. The method further includes retrieving geo-based data from the subset of users over a first timeframe. The method further includes designating one or more geographic regions associated with the subset of users as a treatment group and one or more geographic regions associated with the subset of users as a control group. The method further includes modifying a spend level associated with the treatment group and retrieving geo-based data over a second timeframe. The method further includes calculating an impact of the modification of the spend level and generating graphical interface data for presentation to a device of a content provider