True polar wander driven by late-stage volcanism and the distribution of paleopolar deposits on Mars

The areal centroids of the youngest polar deposits on Mars are offset from those of adjacent paleopolar deposits by 5-10 degrees. We test the hypothesis that the offset is the result of true polar wander (TPW), the motion of the solid surface with respect to the spin axis, caused by a mass redistribution within or on the surface of Mars. In particular, we consider TPW driven by late-stage volcanism during the late Hesperian to Amazonian. There is observational and qualitative support for this hypothesis: in both North and South, observed offsets lie close to a great circle 90 degrees from Tharsis, as expected for polar wander after Tharsis formed. We calculate the magnitude and direction of TPW produced by mapped late-stage lavas for a range of lithospheric thicknesses, lava thicknesses, eruption histories, and prior polar wander events. If Tharsis formed close to the equator, the stabilizing effect of a fossil rotational bulge located close to the equator leads to predicted TPW of <2 degrees, too small to account for observed offsets. If, however, Tharsis formed far from the equator, late-stage TPW driven by low-latitude, late-stage volcanism would be 6-33 degrees, similar to that inferred from the location of paleopolar deposits. 4.4+/-1.3x10^19 kg of young erupted lava can account for the offset of the Dorsa Argentea Formation from the present-day south rotation pole. This mass is consistent with prior mapping-based estimates and would imply a mass release of CO2 by volcanic degassing similar to that in the atmosphere at the present time. The South Polar Layered Deposits are offset from the spin axis in the opposite sense to the other paleopolar deposits. This can be explained by an additional contribution from a plume beneath Elysium. We conclude with a list of observational tests of the TPW hypothesis.Comment: Accepted by Earth and Planetary Science Letters. 3 tables, 8 figure

Robust Tests for Deterministic Seasonality and Seasonal Mean Shifts

We develop tests for the presence of deterministic seasonal behaviour and seasonal mean shifts in a seasonally observed univariate time series. These tests are designed to be asymptotically robust to the order of integration of the series at both the zero and seasonal frequencies. Motivated by the approach of Hylleberg, Engle, Granger and Yoo [1990, Journal of Econometrics vol. 44, pp. 215-238], we base our approach on linear filters of the data which remove any potential unit roots at the frequencies not associated with the deterministic component(s) under test. Test statistics are constructed using the filtered data such that they have well defined limiting null distributions regardless of whether the data are either integrated or stationary at the frequency associated with the deterministic component(s) under test. In the same manner as Vogelsang [1998, Econometrica vol. 66, pp. 123-148], Bunzel and Vogelsang [2005, Journal of Business and Economic Statistics vol. 23, pp. 381-394] and Sayginsoy and Vogelsang [2011, Econometric Theory vol. 27, pp. 992-1025], we scale these statistics by a function of an auxiliary seasonal unit root statistic. This allows us to construct tests which are asymptotically robust to the order of integration of the data at both the zero and seasonal frequencies. Monte Carlo evidence suggests that our proposed tests have good finite sample size and power properties. An empirical application to U.K. GDP indicates the presence of seasonal mean shifts in the data

Statistically derived contributions of diverse human influences to twentieth-century temperature changes

The warming of the climate system is unequivocal as evidenced by an increase in global temperatures by 0.8 °C over the past century. However, the attribution of the observed warming to human activities remains less clear, particularly because of the apparent slow-down in warming since the late 1990s. Here we analyse radiative forcing and temperature time series with state-of-the-art statistical methods to address this question without climate model simulations. We show that long-term trends in total radiative forcing and temperatures have largely been determined by atmospheric greenhouse gas concentrations, and modulated by other radiative factors. We identify a pronounced increase in the growth rates of both temperatures and radiative forcing around 1960, which marks the onset of sustained global warming. Our analyses also reveal a contribution of human interventions to two periods when global warming slowed down. Our statistical analysis suggests that the reduction in the emissions of ozone-depleting substances under the Montreal Protocol, as well as a reduction in methane emissions, contributed to the lower rate of warming since the 1990s. Furthermore, we identify a contribution from the two world wars and the Great Depression to the documented cooling in the mid-twentieth century, through lower carbon dioxide emissions. We conclude that reductions in greenhouse gas emissions are effective in slowing the rate of warming in the short term.F.E. acknowledges financial support from the Consejo Nacional de Ciencia y Tecnologia (http://www.conacyt.gob.mx) under grant CONACYT-310026, as well as from PASPA DGAPA of the Universidad Nacional Autonoma de Mexico. (CONACYT-310026 - Consejo Nacional de Ciencia y Tecnologia; PASPA DGAPA of the Universidad Nacional Autonoma de Mexico

Iron deficiency intravenous substitution in a Swiss academic primary care division: analysis of practices.

BACKGROUND: Iron deficiency is a common problem in primary care and is usually treated with oral iron substitution. With the recent simplification of intravenous (IV) iron administration (ferric carboxymaltose) and its approval in many countries for iron deficiency, physicians may be inclined to overutilize it as a first-line substitution. OBJECTIVE: The aim of this study was to evaluate iron deficiency management and substitution practices in an academic primary care division 5 years after ferric carboxymaltose was approved for treatment of iron deficiency in Switzerland. METHODS: All patients treated for iron deficiency during March and April 2012 at the Geneva University Division of Primary Care were identified. Their medical files were analyzed for information, including initial ferritin value, reasons for the investigation of iron levels, suspected etiology, type of treatment initiated, and clinical and biological follow-up. Findings were assessed using an algorithm for iron deficiency management based on a literature review. RESULTS: Out of 1,671 patients, 93 were treated for iron deficiency. Median patients' age was 40 years and 92.5% (n=86) were female. The average ferritin value was 17.2 μg/L (standard deviation 13.3 μg/L). The reasons for the investigation of iron levels were documented in 82% and the suspected etiology for iron deficiency was reported in 67%. Seventy percent of the patients received oral treatment, 14% IV treatment, and 16% both. The reasons for IV treatment as first- and second-line treatment were reported in 57% and 95%, respectively. Clinical and biological follow-up was planned in less than two-thirds of the cases. CONCLUSION: There was no clear overutilization of IV iron substitution. However, several steps of the iron deficiency management were not optimally documented, suggesting shortcuts in clinical reasoning

A Generalization of the Convex Kakeya Problem

Given a set of line segments in the plane, not necessarily finite, what is a convex region of smallest area that contains a translate of each input segment? This question can be seen as a generalization of Kakeya's problem of finding a convex region of smallest area such that a needle can be rotated through 360 degrees within this region. We show that there is always an optimal region that is a triangle, and we give an optimal \Theta(n log n)-time algorithm to compute such a triangle for a given set of n segments. We also show that, if the goal is to minimize the perimeter of the region instead of its area, then placing the segments with their midpoint at the origin and taking their convex hull results in an optimal solution. Finally, we show that for any compact convex figure G, the smallest enclosing disk of G is a smallest-perimeter region containing a translate of every rotated copy of G.Comment: 14 pages, 9 figure

An algorithm to obtain global solutions of the double confluent Heun equation

A procedure is proposed to construct solutions of the double confluent Heun equation with a determinate behaviour at the singular points. The connection factors are expressed as quotients of Wronskians of the involved solutions. Asymptotic expansions are used in the computation of those Wronskians. The feasibility of the method is shown in an example, namely, the Schroedinger equation with a quasi-exactly-solvable potential

Actions of the braid group, and new algebraic proofs of results of Dehornoy and Larue

This article surveys many standard results about the braid group with emphasis on simplifying the usual algebraic proofs. We use van der Waerden's trick to illuminate the Artin-Magnus proof of the classic presentation of the algebraic mapping-class group of a punctured disc. We give a simple, new proof of the Dehornoy-Larue braid-group trichotomy, and, hence, recover the Dehornoy right-ordering of the braid group. We then turn to the Birman-Hilden theorem concerning braid-group actions on free products of cyclic groups, and the consequences derived by Perron-Vannier, and the connections with the Wada representations. We recall the very simple Crisp-Paris proof of the Birman-Hilden theorem that uses the Larue-Shpilrain technique. Studying ends of free groups permits a deeper understanding of the braid group; this gives us a generalization of the Birman-Hilden theorem. Studying Jordan curves in the punctured disc permits a still deeper understanding of the braid group; this gave Larue, in his PhD thesis, correspondingly deeper results, and, in an appendix, we recall the essence of Larue's thesis, giving simpler combinatorial proofs.Comment: 51`pages, 13 figure

'Do not attempt resuscitation' and 'cardiopulmonary resuscitation' in an inpatient setting : factors influencing physicians' decisions in Switzerland

To determine the prevalence of cardiopulmonary resuscitation (CPR) and do-not-attempt-resuscitation (DNAR) orders, to define factors associated with CPR/DNAR orders and to explore how physicians make and document these decisions. We prospectively reviewed CPR/DNAR forms of 1,446 patients admitted to the General Internal Medicine Department of the Geneva University Hospitals, a tertiary-care teaching hospital in Switzerland. We additionally administered a face-to-face survey to residents in charge of 206 patients including DNAR and CPR orders, with or without patient inclusion.; 21.2% of the patients had a DNAR order, 61.7% a CPR order and 17.1% had neither. The two main factors associated with DNAR orders were a worse prognosis and/or a worse quality of life. Others factors were an older age, cancer and psychiatric diagnoses, and the absence of decision-making capacity. Residents gave four major justifications for DNAR orders: important comorbid conditions (34%), the patients' or their family's resuscitation preferences (18%), the patients' age (14.2%), and the absence of decision-making capacity (8%). Residents who wrote DNAR orders were more experienced. In many of the DNAR or CPR forms (19.8 and 16%, respectively), the order was written using a variety of formulations. For 24% of the residents, the distinction between the resuscitation order and the care objective was not clear. 38% of the residents found the resuscitation form useful.; Patients' prognosis and quality of life were the two main independent factors associated with CPR/DNAR orders. However, in the majority of cases, residents evaluated prognosis only intuitively, and quality of life without involving the patients. The distinction between CPR/DNAR orders and the care objectives was not always clear. Specific training regarding CPR/DNAR orders is necessary to improve the CPR/DNAR decision process used by physicians

Quasi-analyticity and determinacy of the full moment problem from finite to infinite dimensions

This paper is aimed to show the essential role played by the theory of quasi-analytic functions in the study of the determinacy of the moment problem on finite and infinite-dimensional spaces. In particular, the quasi-analytic criterion of self-adjointness of operators and their commutativity are crucial to establish whether or not a measure is uniquely determined by its moments. Our main goal is to point out that this is a common feature of the determinacy question in both the finite and the infinite-dimensional moment problem, by reviewing some of the most known determinacy results from this perspective. We also collect some properties of independent interest concerning the characterization of quasi-analytic classes associated to log-convex sequences.Comment: 28 pages, Stochastic and Infinite Dimensional Analysis, Chapter 9, Trends in Mathematics, Birkh\"auser Basel, 201