Fault-Tolerant Formation Driving Mechanism Designed for Heterogeneous MAVs-UGVs Groups

A fault-tolerant method for stabilization and navigation of 3D heterogeneous formations is proposed in this paper. The presented Model Predictive Control (MPC) based approach enables to deploy compact formations of closely cooperating autonomous aerial and ground robots in surveillance scenarios without the necessity of a precise external localization. Instead, the proposed method relies on a top-view visual relative localization provided by the micro aerial vehicles flying above the ground robots and on a simple yet stable visual based navigation using images from an onboard monocular camera. The MPC based schema together with a fault detection and recovery mechanism provide a robust solution applicable in complex environments with static and dynamic obstacles. The core of the proposed leader-follower based formation driving method consists in a representation of the entire 3D formation as a convex hull projected along a desired path that has to be followed by the group. Such an approach provides non-collision solution and respects requirements of the direct visibility between the team members. The uninterrupted visibility is crucial for the employed top-view localization and therefore for the stabilization of the group. The proposed formation driving method and the fault recovery mechanisms are verified by simulations and hardware experiments presented in the paper.     

Comparative analysis of microstructure and fracture surfaces of blade roots

Samples of chromium stainless steel were loaded to investigate fatigue crack growth in roots of steam turbine blades. Images of the material microstructure and fracture surfaces were subjected to textural image analysis. The main steps were normalization, enhancement of fiber structures and 2D Fourier transforms. By means of analysis of spectra in the space of periods, characteristic dimensions of both image sets were investigated. The locations of three peaks of spectral functions are very close in both image sets. It may be concluded that the material microstructure is projected onto the morphology of fracture surfaces much more than was expected.     

Can parental longevity and self-rated life expectancy predict mortality among older persons? Results from an Australian cohort

This study examined the effects of parental longevity and self-rated life expectancy on mortality, building upon the established model of self-rated health predicting mortality. A community sample of Australians aged 70 and over was surveyed in 1992 and 1995. The associations of interest were examined separately by sex using weighted multiple logistic regression. Parental ages at death were not associated with mortality for either men or women. In multivariate models, self-rated life expectancy had an independent effect on men's mortality and did not reduce the effect of self-rated health on mortality. Our findings from Australia are consistent with results from many countries; the effect of self-rated health on mortality is stronger for men than for women. We also found that the effect of self-rated life expectancy on mortality is stronger for men than for women. The independent effects of self-rated health and self-rated life expectancy indicate a need for a more detailed search for explanatory mechanisms.     

Cardiovascular risk reduction in a community setting: some comments

Four case reports are presented of patients who ate the meat of a hog inadvertently fed seed treated with fungicides containing ethyl mercury chloride. The clinical, electrophysiological, and toxicological, and in two of the patients the pathological data, showed that this organic mercury compound has a very high toxicity not only for the brain, but also for the spinal motoneurones, peripheral nerves, skeletal muscles, and myocardium.     

Properties of trivalent-ion doped tungsten bronzes

Measurements of the electrical conductivity and the Hall coefficient have been made on polycrystalline yttrium-doped tungsten oxide, Y _x WO₃, for 0.05 ≤ x ≤ 0.20. This range of x includes the predicted metal–insulator transition. The results are compared with findings for La _x WO₃. Samples were prepared by solid-state reaction. Powder x-ray diffraction results for Y _x WO₃ show a single-phase perovskite cubic structure for 0.08 < x < 0.13, with additional phases occurring outside this range. Room temperature diffuse reflectance properties in the visible and infrared are dominated by the x-dependent metallic carrier concentration. The electrical conductivity and Hall effect results are similar to those of La _x WO₃ for x < 0.13, but show differences at higher x linked to the appearance of non-cubic crystallographic phases. The transport properties are typical of metal–insulator systems, with a change from metallic to activated behavior as x is reduced. The Hall results suggest that the trivalent ions donate their valence electron to the WO₃ conduction band.     

The influence of the work environment on cardiovascular health: a historical, conceptual, and methodological perspective

The framework of psychosocial epidemiology is used to examine research developments that characterize the accumulation of knowledge regarding the role of the work environment in cardiovascular health and disease. The discussion of current programs of research focuses on the work of T. Theorell and R. Karasek (1996) and J. Siegrist (1996) as exemplars of European and American studies that have contributed the most to the understanding of occupational cardiovascular health. It is argued that researchers need to maintain and nurture relatively broad conceptual models of etiology because cardiovascular disease involves multiple biomedical risk factors and because specific aspects of the work environment are embedded in a large, complex matrix of other psychosocial influences. At the same time, investigators need to push ahead with focused research strategies to clarify the precise nature of the work environmental risk factors that emerge in the broad, somewhat imprecise epidemiologic study designs.     

A simple device for obtaining certain verbal activity measures during interviews.

This paper describes a new instrument devised by G. F. Mahl to determine the duration of time spent talking by the participants in psychotherapy, and the amount of time the patient is silent during successive 2-minute intervals of individual interviews as well as during larger and variable time intervals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Depressive symptoms across older spouses and the moderating effect of marital closeness.

Independent interviews with husbands and wives from 317 community-dwelling older couples showed that depressive symptoms in 1 spouse had a significant impact on depressive symptoms in the other spouse, after controlling for potentially confounding respondent sociodemographic and health status variables. Relationship quality moderated the influence, with spouse depressive symptoms contributing more of the variance to a respondent's symptoms when a couple were close than when they were not and closeness to a spouse buffering the potentially depressive effects of a respondent's own frailty and financial distress. Husband's own variables explained more of the variance in his symptoms when the couple were not close than when they were, and closeness to his wife increased a husband's vulnerability to the impact of the wife's health status. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptions of the Neighborhood and the Desire to Move Out

A study of various perceptions of the neighborhood indicates that such perceptions are related to each other and to the desire to move out of the neighborhood. The study sample included 1000 adults, twenty-five to sixty years old, married, and living with their spouse. One half of the respondents lived in high stress census tracts (that is, characterized by a low socioeconomic level and high level of “social disorganization”) and the other half lived in low stress tracts. The sample was also divided equally by sex and race of respondent. The major findings of the study show that living in a high stress area has a strong influence on: familiarity with events of crime and violence in the neighborhood, negative evaluation of the police, perception of the neighborhood as unsafe, criticism of facilities in the neighborhood, dislike of the neighborhood, and desire to move out. Sex of the respondent played a small role in these findings, but race seemed to be a more important factor: black respondents had more negative perceptions of the neighborhood than did white respondents, particularly in the high stress neighborhoods. The perceptions of the neighborhood are interrelated in various ways.     

Can mammography screening explain the race difference in stage at diagnosis of breast cancer?

BACKGROUND: A race difference in the stage at diagnosis of breast cancer is well established: African American women are less likely than white women to be diagnosed at a localized stage. The purpose of this study was to determine the extent to which the observed race (black/white) difference in stage at diagnosis of breast cancer could be accounted for by race differences in the mammography screening history. METHODS: This was a population-based, retrospective study of 145 African American and 177 white women with newly diagnosed breast cancer in Connecticut, between January, 1987 and March, 1989. Cases were ascertained through active surveillance of 22 Connecticut hospitals. RESULTS: Black women were diagnosed more commonly with later stage cancer (TNM stage > or = II) (age-adjusted odds ratio [OR] = 2.01, 95% confidence interval [CI] 1.24-3.24) than were white women. Blacks were also more likely than whites to report that they had not received a mammogram in the 3 years before development of symptoms or diagnosis (OR = 2.05, 95% CI 1.26-3.35); this association was not altered substantially with adjustment for socioeconomic status. In race-specific analyses, mammography was protective against later stage diagnosis in white women, but not in black women. With adjustment for mammography screening, the OR for the race-stage association was reduced only minimally, and race remained a significant predictor of stage at diagnosis. CONCLUSIONS: In these population-based data, history of mammography screening was not an important explanatory variable in the race-stage association. Specifically, history of mammographic screening accounted for less than 10% of the observed black/white difference in stage at diagnosis of breast cancer.