Electrification of the proof mass of a drag-free or accelerometric satellite

The exploitation of the data provided by the Cactus accelerometer, which makes up the payload of the D5B Castor Satellite of CNES confirmed the existence of an electric current charging the proof mass under the influence of the magnetospheric protons, and revealed a periodic variation of this current, due to the passage of the apogee through the South Atlantic magnetic anomaly. Results of in-orbit measurements of this charging current are presented, as well as calculations made for determining this current and its variations from data on proton flux at the satellite altitudes. The comparison of measured and calculated values shows that the calculation method is valid and precise enough to be used for drag-free or accelerometric satellites

The Impact of Differential Payroll Tax Subsidies on Minimum Wage Employment

In this paper, we study the impact of changes of total labor costs on employment of low-wage workers in France in a period, 1990 to 1998, that saw sudden and large changes in these costs. We use longitudinal data from the French Labor Force survey (? enqu?te emploi ?) in order to understand the consequences of real decreases and real increases of the labor cost. We examine the transition probabilities from employment to non-employment and from non-employment to employment. In particular, we compare the transition probabilities of the workers that were directly affected by the changes (?between? workers) with the transition probabilities of workers closest in the wage distribution to those directly affected (?marginal? workers). In all years with an increasing minimum wage cost, the ?between? group (or the treated using the vocabulary of controlled experiments) comprises all workers whose costs in year t lie between the old (year t) and the new (year t+1) minimum. In all years with a decreasing minimum, the ?between? group comprises all workers whose costs in year t+1 lie between the present minimum wage cost (year t+1) and the old (year t) minimum wage cost. The results can be summarized as follows. Comparing years of increasing and decreasing minimum wage cost, difference-in-difference estimates imply that an increase of 1% of the cost implies roughly an increase of 1.5% in the probability of transiting from employment to non-employment for the treated workers, the resulting elasticity being ?1.5. Second, results for the transitions from non-employment to employment are less clear-cut. Tax subsidies have a small and insignificant impact on entry from non-employment as well as on transitions within the wage distribution. Finally, there is no obvious evidence of substitution between the ?between? and ?marginal? groups of workers, but there is some evidence of substitution between workers within the tax subsidy zone, with wages above those of the ?marginal?, and workers outside the subsidy zone

Skill-biased technological change and the business cycle

Over the past two decades, technological progress in the United States has been biased towards skilled labor. What does this imply for business cycles? We construct a quarterly skill premium from the CPS and use it to identify skill-biased technology shocks in a VAR with long-run zero and sign restrictions. Hours fall in response to skill-biased technology shocks, indicating that part of the technology-induced fall in hours is due to a compositional shift in labor demand. Investment-specific technology shocks reduce the skill premium, indicating that capital and skill are not complementary in aggregate production

Zero Order Estimates for Analytic Functions

The primary goal of this paper is to provide a general multiplicity estimate. Our main theorem allows to reduce a proof of multiplicity lemma to the study of ideals stable under some appropriate transformation of a polynomial ring. In particular, this result leads to a new link between the theory of polarized algebraic dynamical systems and transcendental number theory. On the other hand, it allows to establish an improvement of Nesterenko's conditional result on solutions of systems of differential equations. We also deduce, under some condition on stable varieties, the optimal multiplicity estimate in the case of generalized Mahler's functional equations, previously studied by Mahler, Nishioka, Topfer and others. Further, analyzing stable ideals we prove the unconditional optimal result in the case of linear functional systems of generalized Mahler's type. The latter result generalizes a famous theorem of Nishioka (1986) previously conjectured by Mahler (1969), and simultaneously it gives a counterpart in the case of functional systems for an important unconditional result of Nesterenko (1977) concerning linear differential systems. In summary, we provide a new universal tool for transcendental number theory, applicable with fields of any characteristic. It opens the way to new results on algebraic independence, as shown in Zorin (2010).Comment: 42 page

Usefulness and limitation of dobutamine stress echocardiography to predict acute response to cardiac resynchronization therapy.

peer reviewedBackground: It has been hypothesized that a long-term response to cardiac resynchronization therapy (CRT) could correlate with myocardial viability in patients with left ventricular (LV) dysfunction. Contractile reserve and viability in the region of the pacing lead have not been investigated in regard to acute response after CRT. Methods: Fifty-one consecutive patients with advanced heart failure, LV ejection fraction ≤ 35%, QRS duration > 120 ms, and intraventricular asynchronism ≥ 50 ms were prospectively included. The week before CRT implantation, the presence of viability was evaluated using dobutamine stress echocardiography. Acute responders were defined as a ≥15% increase in LV stroke volume. Results: The average of viable segments was 5.8 ± 1.9 in responders and 3.9 ± 3 in nonresponders (P = 0.03). Viability in the region of the pacing lead had an excellent sensitivity (96%), but a low specificity (56%) to predict acute response to CRT. Mitral regurgitation (MR) was reduced in 21 patients (84%) with acute response. The presence of MR was a poor predictor of response (sensibility 93% and specificity 17%). However, combining the presence of MR and viability in the region of the pacing lead yields a sensibility (89%) and a specificity (70%) to predict acute response to CRT. Conclusion: Myocardial viability is an important factor influencing acute hemodynamic response to CRT. In acute responders, significant MR reduction is frequent. The combined presence of MR and viability in the region of the pacing lead predicts acute response to CRT with the best accuracy

WARNING: Physics Envy May Be Hazardous To Your Wealth!

The quantitative aspirations of economists and financial analysts have for many years been based on the belief that it should be possible to build models of economic systems - and financial markets in particular - that are as predictive as those in physics. While this perspective has led to a number of important breakthroughs in economics, "physics envy" has also created a false sense of mathematical precision in some cases. We speculate on the origins of physics envy, and then describe an alternate perspective of economic behavior based on a new taxonomy of uncertainty. We illustrate the relevance of this taxonomy with two concrete examples: the classical harmonic oscillator with some new twists that make physics look more like economics, and a quantitative equity market-neutral strategy. We conclude by offering a new interpretation of tail events, proposing an "uncertainty checklist" with which our taxonomy can be implemented, and considering the role that quants played in the current financial crisis.Comment: v3 adds 2 reference

Elliptic logarithms, diophantine approximation and the Birch and Swinnerton-Dyer conjecture

Most, if not all, unconditional results towards the abc-conjecture rely ultimately on classical Baker's method. In this article, we turn our attention to its elliptic analogue. Using the elliptic Baker's method, we have recently obtained a new upper bound for the height of the S-integral points on an elliptic curve. This bound depends on some parameters related to the Mordell-Weil group of the curve. We deduce here a bound relying on the conjecture of Birch and Swinnerton-Dyer, involving classical, more manageable quantities. We then study which abc-type inequality over number fields could be derived from this elliptic approach.Comment: 20 pages. Some changes, the most important being on Conjecture 3.2, three references added ([Mas75], [MB90] and [Yu94]) and one reference updated [BS12]. Accepted in Bull. Brazil. Mat. So