Multi-Robot Complete Coverage Using Directional Constraints

Complete coverage relies on a path planning algorithm that will move one or more robots, including the actuator, sensor, or body of the robot, over the entire environment. Complete coverage of an unknown environment is used in applications like automated vacuum cleaning, carpet cleaning, lawn mowing, chemical or radioactive spill detection and cleanup, and humanitarian de-mining. The environment is typically decomposed into smaller areas and then assigned to individual robots to cover. The robots typically use the Boustrophedon motion to cover the cells. The location and size of obstacles in the environment are unknown beforehand. An online algorithm using sensor-based coverage with unlimited communication is typically used to plan the path for the robots. For certain applications, like robotic lawn mowing, a pattern might be desirable over a random irregular pattern for the coverage operation. Assigning directional constraints to the cells can help achieve the desired pattern if the path planning part of the algorithm takes the directional constraints into account. The goal of this dissertation is to adapt the distributed coverage algorithm with unrestricted communication developed by Rekleitis et al. (2008) so that it can be used to solve the complete coverage problem with directional constraints in unknown environments while minimizing repeat coverage. It is a sensor-based approach that constructs a cellular decomposition while covering the unknown environment. The new algorithm takes directional constraints into account during the path planning phase. An implementation of the algorithm was evaluated in simulation software and the results from these experiments were compared against experiments conducted by Rekleitis et al. (2008) and with an implementation of their distributed coverage algorithm. The results of this study confirm that directional constraints can be added to the complete coverage algorithm using multiple robots without any significant impact on performance. The high-level goals of complete coverage were still achieved. The work was evenly distributed between the robots to reduce the time required to cover the cells

Chronic defensiveness and neuroendocrine dysfunction reflect a novel cardiac troponin T cut point: The SABPA study.

Background: Sympatho-adrenal responses are activated as an innate defense coping (DefS) mechanism during emotional stress. Whether these sympatho-adrenal responses drive cardiac troponin T (cTnT) increases are unknown. Therefore, associations between cTnT and sympatho-adrenal responses were assessed. Methods: A prospective bi-ethnic cohort, excluding atrial fibrillation, myocardial infarction and stroke cases, was followed for 3 years (N=342; 45.6±9.0 years). We obtained serum high-sensitive cTnT and outcome measures [Coping-Strategy-Indicator, depression/Patient-Health-Questionnarie-9, 24h BP, 24h heart-rate-variability (HRV) and 24h urinary catecholamines]. Results: cTnT levels of the cohort remained similar over 3 years but recovery to cTnT-negative levels was higher in Blacks. Blacks showed moderate depression (45% vs. 16%) and 24h hypertension (67% vs. 42%) prevalence compared to Whites. A receiver-operating-characteristics cTnT cut-point 4.2 ng/L predicting hypertension in Blacks was used as binary exposure measure in relation to outcome measures [AUC 0.68 (95% CI 0.60-0.76); sensitivity/specificity 63/70%; P≤0.001]. In cross-sectional analyses, elevated cTnT was related to DefS [OR 1.08 (95% CI 0.99-1.16); P=0.06]; 24h BP [OR 1.03-1.04 (95% CI 1.01-1.08); P≤0.02] and depressed HRV [OR 2.19 (95% CI 1.09-4.41); P=0.03] in Blacks, but not in Whites. At 3 year follow-up, elevated cTnT was related to attenuated urine norepinephrine:creatinine ratio in Blacks [OR 1.46 (95% CI 1.01-2.10); P=0.04]. In Whites, a cut point of 5.6 ng/L cTnT predicting hypertension was not associated with outcome measures. Conclusion: Central neural control systems exemplified a brain-heart stress pathway. Desensitization of sympatho-adrenal responses occurred with initial neural- (HRV) followed by neuroendocrine dysfunction (norepinephrine:creatinine) in relation to elevated cTnT. Chronic defensiveness may thus drive the desensitization or physiological depression, reflecting ischemic heart disease risk at a 4.2 ng/L cTnT cut-point in Blacks

Dubbele afkomsberekening by die Himba, 'n Hererosprekende volk in Suidwes-Afrika

D.Litt. et Phil. (Folklore)Please refer to full text to view abstrac

Stress-induced cardiac troponin T, S100B and estradiol responses in defensive copers: The SABPA study

Ineffective stress-coping in Africans is associated with cardiac ischemia during acute mental stress. Ischemic conditions may be worsened by stress-induced release of glial-derived S100‑calcium-binding-protein β (S100B), which is pro-apoptotic for cardiomyocytes. Whether estradiol as coping regulator and cardio-protective factor will protect against pro-apoptotic effects, remains unclear. Therefore, we aimed to investigate stress-induced associations between cardiac troponin T/cTnT (cardiac ischemic marker), S100B and estradiol in a bi-ethnic cohort of defensive copers of both sexes. The target population study included African and Caucasian teachers of both sexes (n = 344; aged 20-65 years). The Stroop-color-word-conflict-test was administrated for 1 min to induce acute mental stress in the participants. A chronic stress risk phenotype score was obtained. The Coping Strategy Indicator determined habitual defensive/avoidance/seeking social support coping scores. Fasting blood samples were obtained prior to and 10 min post-Stroop-stress to assess cTnT, S100B and estradiol levels. An interaction between ethnicity, sex and defensive coping (p < 0.05) was found for acute stress-induced percentage changes in estradiol. In defensive coping African men, the Stroop-color-word-conflict-test elicited decreases in S100B and increases in estradiol. Again, in this group, S100B decreases were related to unchanged cTnT, a chronic stress risk phenotype and acute estradiol increases (p < 0.05). No associations among main markers were apparent in the African women or the Caucasian defensive copers of both sexes. In the defensive coping African men, the markers studied may play a relevant role in the brain-cardiovascular system interaction during stress exposure. Further research is needed to elaborate on potential mechanisms and to establish clinical relevance

Associations of conscientiousness with cardiac troponin T and stress coping responses in a teacher cohort: the SABPA prospective cohort study

Background: In a South African bi-ethnic cohort, defensive (DefS)/social support/avoidance coping strategies have been shown to influence cardiac troponin T (cTnT) levels through different stress signalling pathways. Personality traits (extraversion, neuroticism, conscientiousness, openness to experience, agreeableness) partially control stress coping responses and may affect prospective cardiac responses. Hence in this cohort, we aimed to examine relationships between personality traits and coping strategies, and to assess associations between cTnT changes over time, personality traits and coping strategies. Methods: A cohort of African and Caucasian male and female teachers (n = 359) participating in both phases of the Sympathetic activity and Ambulatory Blood Pressure in Africans (SABPA) study, was prospectively followed for three years. Personality traits (Basic Traits Inventory) and coping (Coping Strategy Indicator) scores were determined. Fasting serum samples for cTnT determination were collected. Established hypertension-related cTnT cut-off points of 4.2 pg/ml (Africans) and 5.6 pg/ml (Caucasians) were applied. Results: Higher neuroticism and lower conscientiousness scores were found in the Africans than in the Caucasians (p < 0.05). Both traits correlated with all three coping strategies in Caucasians, but only with DefS and avoidance coping in Africans. Over a period of three years, cTnT levels decreased in both races. Compared to Africans, Caucasians showed a greater recovery from the ethnic-specific cTnT cut-off point over time. In the Africans with high DefS scores, cTnT level changes were inversely associated with conscientiousness (adjusted R2 = 0.14; β = -0.26). In Caucasians scoring high in avoidance coping, conscientiousness (odds ratio 0.84) and neuroticism (odds ratio 0.90) showed a lower likelihood of predicting the cTnT cut-off point. Conclusion: In both races, conscientiousness may contribute to healthier stress coping responses and protect against cardiac ischaemia and risk of hypertension. Keywords: cardiac ischaemia; coping; personality traits; troponin T

Prior experience, cognitive perceptions and psychological skills of senior South African rugby players

http://www.sabinet.co.za/abstracts/sport/sport_v32_n1_a6.htm

Specific coping strategies of Africans during urbanization: comparing cardiovascular responses and perception of health data

Specific coping mechanisms of Africans during urbanization were compared to and correlated with cardiovascular responses and perception of health data. Subjects included men (N = 286) and women (N = 360). The COPE questionnaire classified subjects as active (AC) or passive (PC) copers and the General Health Questionnaire measured subjective perception of health. The Finapres recorded blood pressure continuously before and during application of a handgrip test. Analyses adjusting for age, body mass index and resting cardiovascular data revealed that AC rural subjects showed predominantly cardiac responses and PC rural subjects predominantly vascular responses. All urbanized African men and women showed higher resting blood pressure, vascular responsiveness and hypertension prevalences than their rural counterparts. All rural AC subjects, especially women, and all urban PC subjects, especially men, reported a poorer perception of health. In conclusion, subjects with a PC style showed a predominantly vascular response in rural and urban areas whereas subjects with an AC style seem to shift from a predominant cardiac output response to a predominant vascular resistance response when moving from a rural to an urban area

Coping mechanisms, perception of health and cardiovascular dysfunction in Africans

The purpose of this study was to compare active and passive coping strategies of Africans with perception of own health and cardiovascular data. The subjects included 236 apparently healthy Africans (men = 109; women = 127). The COPE questionnaire was adapted, translated and validated for Africans. Scores on reliable sub-scales were used to classify men and women into more active coping (AC) and more passive coping (PC) subgroups. The General Health Questionnaire measured subjective perception of health. Blood pressure was recorded before and during application of the handgrip test, using the Finapres, a continuous non-invasive blood pressure monitor. Plasma renin activity (PRA) values, measured with radio immuno assay, were compared to blood pressure variables. Analyses of co-variance, adjusted for resting values and age, indicated that PC men responded with a larger increase in total peripheral resistance (TPR) (p = 0.006), larger decrease in stroke volume (p = 0.07), smaller increase in cardiac output (p = 0.09) and larger increases in PRA resting (p = 0.04) and reactivity (p ≤ 0.05) values. PC subjects reported a more negative perception of health than AC subjects. Young PC women presented greater hypertension prevalence rates (p ≤ 0.01) than AC women. In conclusion, all AC and PC subjects reacted with increased vascular reactivity on the handgrip test. PC men presented enhanced vascular reactivity, PRA and perception of poorer health value