Decimation and Harmonic Inversion of Periodic Orbit Signals

We present and compare three generically applicable signal processing methods for periodic orbit quantization via harmonic inversion of semiclassical recurrence functions. In a first step of each method, a band-limited decimated periodic orbit signal is obtained by analytical frequency windowing of the periodic orbit sum. In a second step, the frequencies and amplitudes of the decimated signal are determined by either Decimated Linear Predictor, Decimated Pade Approximant, or Decimated Signal Diagonalization. These techniques, which would have been numerically unstable without the windowing, provide numerically more accurate semiclassical spectra than does the filter-diagonalization method.Comment: 22 pages, 3 figures, submitted to J. Phys.

Semiclassical quantization of the diamagnetic hydrogen atom with near action-degenerate periodic-orbit bunches

The existence of periodic orbit bunches is proven for the diamagnetic Kepler problem. Members of each bunch are reconnected differently at self-encounters in phase space but have nearly equal classical action and stability parameters. Orbits can be grouped already on the level of the symbolic dynamics by application of appropriate reconnection rules to the symbolic code in the ternary alphabet. The periodic orbit bunches can significantly improve the efficiency of semiclassical quantization methods for classically chaotic systems, which suffer from the exponential proliferation of orbits. For the diamagnetic hydrogen atom the use of one or few representatives of a periodic orbit bunch in Gutzwiller's trace formula allows for the computation of semiclassical spectra with a classical data set reduced by up to a factor of 20.Comment: 10 pages, 9 figure

Employer Policies and Practices to Manage and Prevent Disability: Conclusion to the Special Issue

Purpose Research of employer policies and practices to manage and prevent disability spans many disciplines and perspectives, and there are many challenges related to stakeholder collaboration, data access, and interventions. The purpose of this article is to synthesize the findings from a conference and year-long collaboration among a group of invited researchers intended to spur new research innovations in this field. Methods A multidisciplinary team of 26 international researchers with published research in employer-based disability management or related fields were invited to attend a 3-day conference in Hopkinton, Massachusetts, USA. The conference goals were to review the status of current research of workplace disability management and prevention, examine its relevance for employer decision-making, compare conceptual frameworks or theoretical perspectives, and recommend future research directions. In this paper, we summarize key points from the 6 resulting papers, compare them with an earlier 2005 conference on improving return-to-work research, and conclude with recommendations for further overarching research directions. Results/Conclusion In comparison with the 2005 conference, a greater emphasis was placed on organizational and social factors, employer roles and responsibilities, methods of implementation, non-clinical approaches, and facilitating stay-at-work as well as return-to-work. A special panel of employer consultants and representatives who were featured at the 2015 conference reinforced the importance of organizational culture, leadership style, and financial decision-making strategies at the employer level. Based on the conference proceedings, we recommend that future research in this area should strive for: (a) broader inclusion of workers and workplaces; (b) attention to multilevel influences in the workplace; (c) a focus on social as well as physical aspects of work; (d) earlier employer collaboration efforts; (e) more attention to implementation factors; and (f) a broader assessment of possible outcome domains

Open circular billiards and the Riemann hypothesis

A comparison of escape rates from one and from two holes in an experimental container (e.g. a laser trap) can be used to obtain information about the dynamics inside the container. If this dynamics is simple enough one can hope to obtain exact formulas. Here we obtain exact formulas for escape from a circular billiard with one and with two holes. The corresponding quantities are expressed as sums over zeroes of the Riemann zeta function. Thus we demonstrate a direct connection between recent experiments and a major unsolved problem in mathematics, the Riemann hypothesis.Comment: 5 pages, 4 embedded postscript figures; v2: more explicit on how the Reimann Hypothesis arises from a comparison of one and two hole escape rate

Photoabsorption spectra of the diamagnetic hydrogen atom in the transition regime to chaos: Closed orbit theory with bifurcating orbits

With increasing energy the diamagnetic hydrogen atom undergoes a transition from regular to chaotic classical dynamics, and the closed orbits pass through various cascades of bifurcations. Closed orbit theory allows for the semiclassical calculation of photoabsorption spectra of the diamagnetic hydrogen atom. However, at the bifurcations the closed orbit contributions diverge. The singularities can be removed with the help of uniform semiclassical approximations which are constructed over a wide energy range for different types of codimension one and two catastrophes. Using the uniform approximations and applying the high-resolution harmonic inversion method we calculate fully resolved semiclassical photoabsorption spectra, i.e., individual eigenenergies and transition matrix elements at laboratory magnetic field strengths, and compare them with the results of exact quantum calculations.Comment: 26 pages, 9 figures, submitted to J. Phys.

Complex genome evolution in Anopheles coluzzii associated with increased insecticide usage in Mali.

In certain cases, a species may have access to important genetic variation present in a related species via adaptive introgression. These novel alleles may interact with their new genetic background, resulting in unexpected phenotypes. In this study, we describe a selective sweep on standing variation on the X chromosome in the mosquito Anopheles coluzzii, a principal malaria vector in West Africa. This event may have been influenced by the recent adaptive introgression of the insecticide resistance gene known as kdr from the sister species Anopheles gambiae. Individuals carrying both kdr and a nearly fixed X-linked haplotype, encompassing at least four genes including the P450 gene CYP9K1 and the cuticular protein CPR125, have rapidly increased in relative frequency. In parallel, a reproductively isolated insecticide-susceptible A. gambiae population (Bamako form) has been driven to local extinction, likely due to strong selection from increased insecticide-treated bed net usage

Factors affecting maritime pilots\u27 health and well-being : a systematic review

Background: Maritime pilotage is a demanding occupation where pilots are required to perform complex procedures in sometimes unfamiliar working environments. These psychological stressors, in addition tothe physical demands associated with the role (e.g., reduced sleep, boarding, and departing vessels), may over time have a damaging effect on pilots’ physical and mental health. Therefore the aim of this paper was to systematically review the existing literature on maritime pilots’ health and well-being.Materials and methods: The databases academic search complete, MEDLINE and MEDLINE complete, PsycINFO, PsycARTICLES, PubMed, and ScienceDirect were searched from the earliest available record until 1 May 2015. From an initial pool of 167 manuscripts retrieved, only 18 were peer-reviewed original research and discussed topics associated with maritime pilots’ health and well-being.Results: In total, 29 factors associated with maritime pilot health and well-being were identified. These were loosely categorised into physical (n = 14), psychosocial (n = 8), and workplace issues (n = 7). The most commonly investigated factors were blood pressure or heart rate, sleep or fatigue, smoking and alcohol consumption, perceived stress, and shift duration or cycle. Conclusions: Findings from the review suggest that the prevention of cardiovascular diseases and associated cardio-metabolic risk factors seems to be of paramount importance, with ample evidence indicating that modern-day pilots present as being overweight or obese. What remains unknown is whether these physical factors are associated with variations in psychosocial functioning. Therefore, it is recommended that future pilotage investigations adopt a multidisciplinary approach to better quantify the impact of maritimepilotage on long-term health and well-being