Controlling extended systems with spatially filtered, time-delayed feedback

We investigate a control technique for spatially extended systems combining spatial filtering with a previously studied form of time-delay feedback. The scheme is naturally suited to real-time control of optical systems. We apply the control scheme to a model of a transversely extended semiconductor laser in which a desirable, coherent traveling wave state exists, but is a member of a nowhere stable family. Our scheme stabilizes this state, and directs the system towards it from realistic, distant and noisy initial conditions. As confirmed by numerical simulation, a linear stability analysis about the controlled state accurately predicts when the scheme is successful, and illustrates some key features of the control including the individual merit of, and interplay between, the spatial and temporal degrees of freedom in the control.Comment: 9 pages REVTeX including 7 PostScript figures. To appear in Physical Review

The critical properties of the agent-based model with environmental-economic interactions

The steady-state and nonequilibrium properties of the model of environmental-economic interactions are studied. The interacting heterogeneous agents are simulated on the platform of the emission dynamics of cellular automaton. The model possess the discontinuous transition between the safe and catastrophic ecology. Right at the critical line, the broad-scale power-law distributions of emission rates have been identified. Their relationship to Zipf's law and models of self-organized criticality is discussed.Comment: 12 pages, 6 figures, published in Physica

Time-delayed feedback control in astrodynamics

In this paper we present time-delayed feedback control (TDFC) for the purpose of autonomously driving trajectories of nonlinear systems into periodic orbits. As the generation of periodic orbits is a major component of many problems in astodynamics we propose this method as a useful tool in such applications. To motivate the use of this method we apply it to a number of well known problems in the astrodynamics literature. Firstly, TDFC is applied to control in the chaotic attitude motion of an asymmetric satellite in an elliptical orbit. Secondly, we apply TDFC to the problem of maintaining a spacecraft in a periodic orbit about a body with large ellipticity (such as an asteroid) and finally, we apply TDFC to eliminate the drift between two satellites in low Earth orbits to ensure their relative motion is bounded

Creutzfeldt-Jakob disease and homocysteine levels in plasma and cerebrospinal fluid

Background: There is evidence that homocysteine contributes to various neurodegenerative disorders. Objective: To assess the values of homocysteine in patients with Creutzfeldt-Jakob disease (CJD) in both cerebrospinal fluid (CSF) and plasma. Methods: Study design: Case control study. Total homocysteine was quantified in CSF and plasma samples of CJD patients (n = 13) and healthy controls (n = 13). Results: Mean values in healthy controls: 0.15 mumol/l +/- 0.07 (CSF) and 9.10 mumol/l +/- 2.99 (plasma); mean values in CJD patients: 0.13 mumol/l +/- 0.03 (CSF) and 9.22 mumol/l +/- 1.81 (plasma). No significant differences between CJD patients and controls were observed (Mann-Whitney U, p > 0.05). Conclusions: The results indicate that the CSF and plasma of CJD patients showed no higher endogenous levels of homocysteine as compared to normal healthy controls. These findings provide no evidence for an additional role of homocysteine in the pathogenetic mechanisms underlying CJD neurodegeneration. Copyright (C) 2005 S. Karger AG, Basel

Calcification in a marginal sea - influence of seawater [Ca2+] and carbonate chemistry on bivalve shell formation

In estuarine coastal systems such as the Baltic Sea, mussels suffer from low salinity which limits their distribution. Anthropogenic climate change is expected to cause further desalination which will lead to local extinctions of mussels in the low saline areas. It is commonly accepted that mussel distribution is limited by osmotic stress. However, along the salinity gradient environmental conditions for biomineralization are successively becoming more adverse as a result of reduced [Ca2+] and dissolved inorganic carbon (CT) availability. In larvae, calcification is an essential process starting during early development with formation of the prodissoconch I (PD I) shell which is completed under optimal conditions within 2 days. Experimental manipulations of seawater [Ca2+] start to impair PD I formation in Mytilus larvae at concentrations below 3 mM, which corresponds to conditions present in the Baltic at salinities below 8 g kg-1. In addition, lowering dissolved inorganic carbon to critical concentrations (< 1 mM) similarly affected PD I size which was well correlated with calculated ΩAragonite and [Ca2+][HCO3-]/[H+] in all treatments. Comparing results for larvae from the western Baltic with a population from the central Baltic revealed significantly higher tolerance of PD I formation to lowered [Ca2+] and [Ca2+][HCO3-]/[H+] in the low saline adapted population. This may result from genetic adaptation to the more adverse environmental conditions prevailing in the low saline areas of the Baltic. The combined effects of lowered [Ca2+] and adverse carbonate chemistry represent major limiting factors for bivalve calcification and can thereby contribute to distribution limits of mussels in the Baltic Sea

An investigation of ground shock effects due to Rayleigh waves generated by sonic booms

Ground shock effects due to Rayleigh waves generated by sonic boom

Torsional-flexural buckling of unevenly battened columns under eccentrical compressive loading

In this paper, an analytical model is developed to determine the torsional-flexural buckling load of a channel column braced by unevenly distributed batten plates. Solutions of the critical-buckling loads were derived for three boundary cases using the energy method in which the rotating angle between the adjacent battens was presented in the form of a piecewise cubic Hermite interpolation (PCHI) for unequally spaced battens. The validity of the PCHI method was numerically verified by the classic analytical approach for evenly battened columns and a finite-element analysis for unevenly battened ones, respectively. Parameter studies were then performed to examine the effects of loading eccentricities on the torsional-flexural buckling capacity of both evenly and unevenly battened columns. Design parameters taken into account were the ratios of pure torsional buckling load to pure flexural–buckling load, the number and position of battens, and the ratio of the relative extent of the eccentricity. Numerical results were summarized into a series of relative curves indicating the combination of the buckling load and corresponding moments for various buckling ratios.National Natural Science Foundation of China (NSFC) under grant number (No.) 51175442 and Sichuan International Cooperation Research Project under grant No. 2014HH002

Variation in Provider Identification of Obesity by Individual- and Neighborhood-Level Characteristics among an Insured Population

Objective. The purpose of this study was to examine whether neighborhood- and individual-level characteristics affect providers' likelihood of providing an obesity diagnosis code in their obese patients' claims. Methods. Logistic regressions were performed with obesity diagnosis code serving as the outcome variable and neighborhood characteristics and member characteristics serving as the independent variables (N = 16,151 obese plan members). Results. Only 7.7 percent of obese plan members had an obesity diagnosis code listed in their claims. Members living in neighborhoods with the largest proportions of Blacks were 29 percent less likely to receive an obesity diagnosis (P < .05). The odds of having an obesity diagnosis code were greater among members who were female, aged 44 or below, hypertensive, dyslipidemic, BMI ≥ 35 kg/m2, had a larger number of provider visits, or who lived in an urban area (all P < .05). Conclusions. Most health care providers do not include an obesity diagnosis code in their obese patients' claims. Rates of obesity identification were strongly related to individual characteristics and somewhat associated with neighborhood characteristics

Unconventional Josephson Effect in Hybrid Superconductor-Topological Insulator Devices

We report on transport properties of Josephson junctions in hybrid superconducting-topological insulator devices, which show two striking departures from the common Josephson junction behavior: a characteristic energy that scales inversely with the width of the junction, and a low characteristic magnetic field for suppressing supercurrent. To explain these effects, we propose a phenomenological model which expands on the existing theory for topological insulator Josephson junctions