Computational approaches for model-based Diffuse Optical Tomography

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Price of Competition and Dueling Games

We study competition in a general framework introduced by Immorlica et al. and answer their main open question. Immorlica et al. considered classic optimization problems in terms of competition and introduced a general class of games called dueling games. They model this competition as a zero-sum game, where two players are competing for a user's satisfaction. In their main and most natural game, the ranking duel, a user requests a webpage by submitting a query and players output an ordering over all possible webpages based on the submitted query. The user tends to choose the ordering which displays her requested webpage in a higher rank. The goal of both players is to maximize the probability that her ordering beats that of her opponent and gets the user's attention. Immorlica et al. show this game directs both players to provide suboptimal search results. However, they leave the following as their main open question: "does competition between algorithms improve or degrade expected performance?" In this paper, we resolve this question for the ranking duel and a more general class of dueling games. More precisely, we study the quality of orderings in a competition between two players. This game is a zero-sum game, and thus any Nash equilibrium of the game can be described by minimax strategies. Let the value of the user for an ordering be a function of the position of her requested item in the corresponding ordering, and the social welfare for an ordering be the expected value of the corresponding ordering for the user. We propose the price of competition which is the ratio of the social welfare for the worst minimax strategy to the social welfare obtained by a social planner. We use this criterion for analyzing the quality of orderings in the ranking duel. We prove the quality of minimax results is surprisingly close to that of the optimum solution

Evaluation of rigid registration methods for whole head imaging in diffuse optical tomography

Functional brain imaging has become an important neuroimaging technique for the study of brain organization and development. Compared to other imaging techniques, diffuse optical tomography (DOT) is a portable and low-cost technique that can be applied to infants and hospitalized patients using an atlas-based light model. For DOT imaging, the accuracy of the forward model has a direct effect on the resulting recovered brain function within a field of view and so the accuracy of the spatially normalized atlas-based forward models must be evaluated. Herein, the accuracy of atlas-based DOT is evaluated on models that are spatially normalized via a number of different rigid registration methods on 24 subjects. A multileveled approach is developed to evaluate the correlation of the geometrical and sensitivity accuracies across the full field of view as well as within specific functional subregions. Results demonstrate that different registration methods are optimal for recovery of different sets of functional brain regions. However, the “nearest point to point” registration method, based on the EEG 19 landmark system, is shown to be the most appropriate registration method for image quality throughout the field of view of the high-density cap that covers the whole of the optically accessible cortex

Chemical Composition, Antioxidant Potential, and Antimicrobial Activity of Nannorrhops ritchiana (Griff) Aitch

Introduction: Nannorrhops ritchiana (Griff) Aitch (Arecaceae) is an edible, extensively used shrub to small tree dispersed in Iran, Afghanistan, Pakistan, and Arabian Peninsula. In this study, the total phenolic and flavonoid contents, antioxidant capacity, and antimicrobial activity of the fruit and seed extracts of Nannorrhops ritchiana were evaluated in vitro. Materials and Methods: The plant sample was collected from a wild population in Saraydan village, Iranshahr, Sistan and Baluchistan, and the methanolic extracts of the seeds and fruits were obtained by the maceration method The Folin-Ciocalteu and aluminum chloride colorimetric protocols were followed for quantifying total phenolic and flavonoid contents respectively. The total antioxidant and antimicrobial activity of alcoholic extracts were also measured using 2,2-diphenyl-1-picrylhydrazy (DPPH) free radical scavenging assay and disc diffusion method, respectively. Antimicrobial activity was investigated on 5 Gram-positive (Staphylococcus aureus Streptococcus, pneumoniae, Rhodococcus equi, Bacillus subtilis subsp. Spizizenii and Enterococcus faeca) and 3 Gram-negative (Shigella flexneri, Proteus vulgaris, and Salmonella typhi) bacteria, and 3 fungi (Fusarium oxysporum, Aspergillus fumigatus, and Candida albicans). Results: The total phenolic content of the seeds was higher than that of fruit (331.33±8.3 vs 360.93±10.23 μg gallic acid equivalents/g, respectively) while, the total flavonoid content of seeds was almost half as much as that of fruits (70.50±3.1 vs 127.70 ±5.25 μg quercetin equivalents/g, respectively). The ethanolic seed extract exhibited better scavenging ability for DPPH with IC50 of 117.77 ± 6.3 μg/mL compared to fruit extract with IC50 of 204.34±7.59 μg/mL. Moreover, the ethanolic extracts at initial concentrations inhibited the growth of several tested pathogenic bacterial and fungal strains. Conclusion: These findings suggest that the fruits and seeds of Nannorrhops ritchiana are rich sources of phenolic compounds with natural moderate antioxidant and antimicrobial properties which can be a candidate for possible dietary and/or medication applications