Information-Theoretic Stochastic Optimal Control via Incremental Sampling-based Algorithms

This paper considers optimal control of dynamical systems which are represented by nonlinear stochastic differential equations. It is well-known that the optimal control policy for this problem can be obtained as a function of a value function that satisfies a nonlinear partial differential equation, namely, the Hamilton-Jacobi-Bellman equation. This nonlinear PDE must be solved backwards in time, and this computation is intractable for large scale systems. Under certain assumptions, and after applying a logarithmic transformation, an alternative characterization of the optimal policy can be given in terms of a path integral. Path Integral (PI) based control methods have recently been shown to provide elegant solutions to a broad class of stochastic optimal control problems. One of the implementation challenges with this formalism is the computation of the expectation of a cost functional over the trajectories of the unforced dynamics. Computing such expectation over trajectories that are sampled uniformly may induce numerical instabilities due to the exponentiation of the cost. Therefore, sampling of low-cost trajectories is essential for the practical implementation of PI-based methods. In this paper, we use incremental sampling-based algorithms to sample useful trajectories from the unforced system dynamics, and make a novel connection between Rapidly-exploring Random Trees (RRTs) and information-theoretic stochastic optimal control. We show the results from the numerical implementation of the proposed approach to several examples.Comment: 18 page

Colour contrast and regulation of the long jump approach run

Research has shown that visual perception of the take-off board and the subsequent regulation of the approach run occur 4-5 strides prior to take-off. Contrast in visual perception is determined by the difference in colour and occurs when a surface of one colour induces its antagonist colour in an adjoining surface. The aim of the present study was to investigate if colour contrast between the track surface and the board affects the stride regulation pattern at the long jump approach run. Four long jumpers performed long jumps in two different occasions: 6 from a runway track coloured blue, with a white take-off board and 6 from a modified yellow board. The runway was marked and the approach runs were recorded with a panning camera. Toeboard distance (TBD) for each support phase in every run-up and the percentage distribution of adjustment of the regulated strides was calculated. With the white take-off board, the average TBD variability reached its peak value (21.74cm) on the 5th stride from the board and at a distance of 9.77m from take-off point. With the yellow take-off board the average TBD variability culminated (24.80cm) on the 7th stride from the board and at a distance of 13.40m from take-off point. With the white board, 80% of the adjustment was distributed during the last two strides as opposed to 61% with the yellow board. When a take-off board of a colour complementary to the runway’s blue track surface is used, athletes initiated their regulation 2 strides earlier. This may be attributed to an enhanced visual perception of the approaching target allowing a more uniform distribution of adjustments during the last two strides of the approach

Physicians’ Perceptions and Adherence to Guidelines for the Management of Hypertension: A National, Multicentre, Prospective Study

Background. The aim of the current study was to investigate physicians’ perceptions and adherence to the European guidelines for the management of hypertension. Methods. This is a national, multicentre, prospective, observational study, conducted between November 2007 and June 2008, in Cyprus. Consecutive hypertensive patients have been recruited by a random sample of physicians. The physicians’ recommendations for every single patient have been recorded and compared with the 2007 ESH/ESC guidelines. Results. Of the total of 654 patients, 477 (72.9%) were correctly advised by their physician to receive antihypertensive treatment to control their blood pressure, while 396 (60.5%) correctly got advices to adopt only lifestyle changes. The overall adherence of physicians to the European guidelines (overall agreement rate) was 70.4% (k=0.258, P<0.001). Of the total of 68 physicians, 65 (95.6%) reported that they were aware of some guidelines. There was no statistically significant effect of specific physicians’ characteristics on the overall adherence to guidelines, but there was in the percentage of patients achieving medication guidelines. Conclusions. The study demonstrated that although Cypriot physicians declared that they were aware of the clinical guidelines for the management of hypertension, more than one-fourth of high risk hypertensive patients remained untreated and 40% of low risk patients received inappropriate medication

widespread cross-infection of multiple RNA viruses across wild and managed bees

Declining populations of bee pollinators are a cause of concern, with major repercussions for biodiversity loss and food security. RNA viruses associated with honeybees represent a potential threat to other insect pollinators, but the extent of this threat is poorly understood. This study aims to attain a detailed understanding of the current and ongoing risk of emerging infectious disease (EID) transmission between managed and wild pollinator species across a wide range of RNA viruses. Within a structured large-scale national survey across 26 independent sites, we quantify the prevalence and pathogen loads of multiple RNA viruses in co-occurring managed honeybee (Apis mellifera) and wild bumblebee (Bombus spp.) populations. We then construct models that compare virus prevalence between wild and managed pollinators. Multiple RNA viruses associated with honeybees are widespread in sympatric wild bumblebee populations. Virus prevalence in honeybees is a significant predictor of virus prevalence in bumblebees, but we remain cautious in speculating over the principle direction of pathogen transmission. We demonstrate species-specific differences in prevalence, indicating significant variation in disease susceptibility or tolerance. Pathogen loads within individual bumblebees may be high and in the case of at least one RNA virus, prevalence is higher in wild bumblebees than in managed honeybee populations. Our findings indicate widespread transmission of RNA viruses between managed and wild bee pollinators, pointing to an interconnected network of potential disease pressures within and among pollinator species. In the context of the biodiversity crisis, our study emphasizes the importance of targeting a wide range of pathogens and defining host associations when considering potential drivers of population decline

Intraoperative pleural lavage cytology is an independent prognostic indicator for staging non–small cell lung cancer

AbstractObjectivesFor patients undergoing lung resection for cancer, macroscopic evidence of metastasis is clearly associated with adverse prognosis. However, less is known about the significance of tumor cells detected by using tests such as pleural lavage cytology. To ascertain the frequency and quantify the effect of this finding on survival, we performed a prospective study of intraoperative pleural lavage cytology.MethodsPleural lavage cytology consisted of cytologic analysis of 100 mL of saline irrigated over the lung surface immediately after thoracotomy. Patients were excluded if they had an existing effusion, extreme adhesions, or lateral chest wall invasion or if resection was not performed. Survival was calculated by means of Kaplan-Meier analysis and compared by using log-rank tests. Cox regression was used to ascertain independent predictors of prognosis.ResultsFrom 1995 through 2003, we performed pleural lavage cytology on 292 patients undergoing thoracotomy for lung cancer. The mean age was 64 (SD, 10) years, and 196 (67%) patients were men. Of 292 samples, 13 (4.5%) showed evidence of malignant cells. The median time to follow-up was 15 months (interquartile range, 1-40 months), with a median survival of 49 months for patients with negative pleural lavage cytology results and 13 months for patients with positive pleural lavage cytology results (P = .002). Univariate prognostic predictors were positive pleural lavage cytology status (P = .03), stage (P = .03), adenocarcinoma (P = .06), and parietal pleural involvement (P = .01). In the final multivariate model only positive pleural lavage cytology status (P = .006) and stage (P = .03) remained significant.ConclusionsIntraoperative pleural lavage cytology is a simple addition to intrathoracic staging and an independent predictor of prognosis. Positive results potentially affect survival by upstaging patients to stage IIIB or greater

Effect of dietary protein source on piglet meat quality characteristics

An experiment was conducted to examine the effects of different dietary protein sources (soybean meal vs whey protein) on piglet meat quality characteristics. Eighteen castrated male Large White × Duroc × Landrace piglets were randomly assigned to 2 groups. Piglets were kept in individual metabolic cages and fed ad libitum over a period of 38 days the following 2 diets: diet SB, which was formulated to meet the nutrient requirements of piglets using soybean meal as the main crude protein source and diet WP, where SB was totally replaced by a mixture of whey proteins on equal digestible energy and crude protein basis. At the end of the experiment, piglets were weighed and slaughtered. After overnight chilling, samples of Longissimus dorsi muscle were taken and were used for meat quality measurements.         No significant differences were observed in the values of pH, colour, water holding capacity, shear force and intramuscular fat content of L. dorsi muscle between the dietary treatments. Measurement of lipid oxidation values showed that dietary supplementation with different protein sources did not influence meat antioxidant properties during refrigerated storage. The SB piglets had lower 14:0 (P&lt;0.01) and higher 18:3n-3 (P&lt;0.001) levels in intramuscular fat in comparison with WP piglets. However, these changes were attributed to background differences in the dietary FA profile and not to a direct protein source effect. The results of this preliminary study indicate that the examined dietary protein sources (soybean meal or whey protein) do not have a significant effect on meat quality characteristics of piglets

Applying balanced scorecard methodology in public sector: The case of a vocational school in Greece

Balanced Scorecard is a very important tool for management and evaluation of the long-term organization strategy, which simultaneously observes the improvements at the efficient function, exploiting the most of the organization’s potentials and diffusing the progress to all the employees. The implementation of Balanced Scorecard took place at the 5th Laboratory Centre (LC) of East Attica during the school year 2016-17, after the goals had been set and the measurement indicators had been defined by the school’s administration stuff (School Head, Deputy School Head, Teachers responsible for LC Sectors, Teachers responsible for Direction Laboratories, Teachers Board). The results indicated that the vision, the objectives and the overall strategy of the organization had been clarified and communicated to all customers. The administrative control of the progress of the procedures was more effective and the daily actions were connected with the objectives of the organization. Also it is important that all employees aligned with the organization's long-term strategy, and, furthermore, redesigning the model was possible. In the long term the appropriate background for the ongoing development of the organization and its effectiveness improvement in a constantly changing environment was created