Means and covariance functions for geostatistical compositional data: an axiomatic approach

This work focuses on the characterization of the central tendency of a sample of compositional data. It provides new results about theoretical properties of means and covariance functions for compositional data, with an axiomatic perspective. Original results that shed new light on the geostatistical modeling of compositional data are presented. As a first result, it is shown that the weighted arithmetic mean is the only central tendency characteristic satisfying a small set of axioms, namely continuity, reflexivity and marginal stability. Moreover, this set of axioms also implies that the weights must be identical for all parts of the composition. This result has deep consequences on the spatial multivariate covariance modeling of compositional data. In a geostatistical setting, it is shown as a second result that the proportional model of covariance functions (i.e., the product of a covariance matrix and a single correlation function) is the only model that provides identical kriging weights for all components of the compositional data. As a consequence of these two results, the proportional model of covariance function is the only covariance model compatible with reflexivity and marginal stability

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Deep-Sea Nematodes Actively Colonise Sediments, Irrespective of the Presence of a Pulse of Organic Matter: Results from an In-Situ Experiment

A colonisation experiment was performed in situ at 2500 m water depth at the Arctic deep-sea long-term observatory HAUSGARTEN to determine the response of deep-sea nematodes to disturbed, newly available patches, enriched with organic matter. Cylindrical tubes,laterally covered with a 500 µm mesh, were filled with azoic deep-sea sediment and 13C-labelled food sources (diatoms and bacteria). After 10 days of incubation the tubes were analysed for nematode response in terms of colonisation and uptake. Nematodes actively colonised the tubes,however with densities that only accounted for a maximum of 2.13% (51 ind.10 cm−2) of the ambient nematode assemblages. Densities did not differ according to the presence or absence of organic matter, nor according to the type of organic matter added. The fact that the organic matter did not function as an attractant to nematodes was confirmed by the absence of notable 13C assimilation by the colonising nematodes. Overall, colonisationappears to be a process that yields reproducible abundance and diversity patterns, with certain taxa showing more efficiency. Together with the high variability between the colonising nematode assemblages, this lends experimental support to the existence of a spatio-temporal mosaic that emerges from highly localised, partially stochastic community dynamics

water chemistry are new challenges possible from coda compositional data analysis point of view

John Aitchison died in December 2016 leaving behind an important inheritance: to continue to explore the fascinating world of compositional data. However, notwithstanding the progress that we have made in this field of investigation and the diffusion of the CoDA theory in different researches, a lot of work has still to be done, particularly in geochemistry. In fact most of the papers published in international journals that manage compositional data ignore their nature and their consequent peculiar statistical properties. On the other hand, when CoDA principles are applied, several efforts are often made to continue to consider the log-ratio transformed variables, for example the centered log-ratio ones, as the original ones, demonstrating a sort of resistance to thinking in relative terms. This appears to be a very strange behavior since geochemists are used to ratios and their analysis is the base of the experimental calibration when standards are evolved to set the instruments. In this chapter some challenges are presented by exploring water chemistry data with the aim to invite people to capture the essence of thinking in a relative and multivariate way since this is the path to obtain a description of natural processes as complete as possible

Determining the Effectiveness of HOV Lanes

This document is the final report for the two-year PATH Project “Determining the Effectiveness of HOV Lanes”. It has been supported by the California Department of Transportation (Caltrans). The primary objectives of this project have been to evaluate freeways having on-freeway HOV lanes in terms of vehicle-travel, person-travel, occupancy distribution, shape and duration of the peak period, congestion patterns, and air quality both in the HOV lane and the adjacent mixed-flow lanes.Based on a comprehensive literature review an extensive list of reference was developed, along with summaries synthesizing the state of the knowledge regarding the effectiveness of HOV lanes and their impact on air quality.Historical and current field data were assembled and analyzed for all of California’s HOV lanes. The analysis revealed that there is strong public support for HOV lanes, California’s HOV lanes are well utilized and offer significant time savings to ride sharers, that there is a steady growth in the number of carpoolers, violation rates are low, and that over time, HOV lanes cause carpools to last longer.The air quality module in the freeway simulation model FREQ was updated to reflect the most up-to-date techniques for predicting air quality developed by the California Air Resources Boardin their EMFAC model. The new air quality methodology was also used to develop an off-line air quality module for use with PeMS data.The design of a successful HOV lane facility is a very difficult task and requires careful analyses prior to implementation in order to move toward an optimum design. Accurate data on vehicle occupancy distributions and traffic demand levels are essential for realistic modeling of such facilities. To demonstrate the types of analyses that would be useful in this process, the modified freeway simulation model FREQ was applied to two freeway study sites, one in Northern California and one in Southern California. The FREQ model proved to be well suited for investigating various combinations of HOV lane design and operating parameters. As traffic demands increase and HOV lanes generate changes in ridesharing choices, the continued success of HOV lane operation is likely to require changes in HOV lane design and operations. This will require careful monitoring of the HOV lane facility and further modeling analyses

Infected chylothorax: a case report and review

Infected chylothorax is a rare complication of a rare pathology with limited literature entirely consisting of case reports, meeting abstracts, and letters to the editor. The case of a 56-year-old male with a spontaneous infected chylothorax successfully treated and discharged to home without any residual effects is described. A systematic review of the literature revealed 11 prior cases of infected chylothoraces. Their etiologies (when known), initial pleural fluid values, and treatment are described. These cases show that while infected chylothorax has a varied presentation and affects a broad range of patients, conservative management including antibiotics, pleural fluid drainage, and symptomatic relief is a safe and appropriate starting point