Multi-Armed Bandits for Correlated Markovian Environments with Smoothed Reward Feedback

We study a multi-armed bandit problem in a dynamic environment where arm rewards evolve in a correlated fashion according to a Markov chain. Different than much of the work on related problems, in our formulation a learning algorithm does not have access to either a priori information or observations of the state of the Markov chain and only observes smoothed reward feedback following time intervals we refer to as epochs. We demonstrate that existing methods such as UCB and $\varepsilon$-greedy can suffer linear regret in such an environment. Employing mixing-time bounds on Markov chains, we develop algorithms called EpochUCB and EpochGreedy that draw inspiration from the aforementioned methods, yet which admit sublinear regret guarantees for the problem formulation. Our proposed algorithms proceed in epochs in which an arm is played repeatedly for a number of iterations that grows linearly as a function of the number of times an arm has been played in the past. We analyze these algorithms under two types of smoothed reward feedback at the end of each epoch: a reward that is the discount-average of the discounted rewards within an epoch, and a reward that is the time-average of the rewards within an epoch.Comment: Significant revision of prior version including deeper discussion of related work, gap-independent regret bounds, and regret bounds for discounted reward

Hypo‐collagenesis in photoaged skin predicts response to anti‐aging cosmeceuticals

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98115/1/jocd12037.pd

Aging Alters Functionally Human Dermal Papillary Fibroblasts but Not Reticular Fibroblasts: A New View of Skin Morphogenesis and Aging

Understanding the contribution of the dermis in skin aging is a key question, since this tissue is particularly important for skin integrity, and because its properties can affect the epidermis. Characteristics of matched pairs of dermal papillary and reticular fibroblasts (Fp and Fr) were investigated throughout aging, comparing morphology, secretion of cytokines, MMPs/TIMPs, growth potential, and interaction with epidermal keratinocytes. We observed that Fp populations were characterized by a higher proportion of small cells with low granularity and a higher growth potential than Fr populations. However, these differences became less marked with increasing age of donors. Aging was also associated with changes in the secretion activity of both Fp and Fr. Using a reconstructed skin model, we evidenced that Fp and Fr cells do not possess equivalent capacities to sustain keratinopoiesis. Comparing Fp and Fr from young donors, we noticed that dermal equivalents containing Fp were more potent to promote epidermal morphogenesis than those containing Fr. These data emphasize the complexity of dermal fibroblast biology and document the specific functional properties of Fp and Fr. Our results suggest a new model of skin aging in which marked alterations of Fp may affect the histological characteristics of skin

Brazilian Consensus on Photoprotection

Brazil is a country of continental dimensions with a large heterogeneity of climates and massive mixing of the population. Almost the entire national territory is located between the Equator and the Tropic of Capricorn, and the Earth axial tilt to the south certainly makes Brazil one of the countries of the world with greater extent of land in proximity to the sun. The Brazilian coastline, where most of its population lives, is more than 8,500 km long. Due to geographic characteristics and cultural trends, Brazilians are among the peoples with the highest annual exposure to the sun. Epidemiological data show a continuing increase in the incidence of nonmelanoma and melanoma skin cancers. Photoprotection can be understood as a set of measures aimed at reducing sun exposure and at preventing the development of acute and chronic actinic damage. Due to the peculiarities of Brazilian territory and culture, it would not be advisable to replicate the concepts of photoprotection from other developed countries, places with completely different climates and populations. Thus the Brazilian Society of Dermatology has developed the Brazilian Consensus on Photoprotection, the first official document on photoprotection developed in Brazil for Brazilians, with recommendations on matters involving photoprotection

Recommandations pour l’oxygénothérapie chez l’enfant en situations aiguës et chroniques : évaluation du besoin, critères de mise en route, modalités de prescription et de surveillance

International audienceRecommendations for acute and long-term oxygen therapy (needs assessment, implementation criteria, prescription practices, and follow-up) in children were produced by the Groupe de Recherche sur les Avancées en Pneumo-Pédiatrie (GRAPP) under the auspices of the French Paediatric Pulmonology and Allergology Society (SP2A). The Haute Autorité de Santé (HAS) methodology, based on the Formalized Consensus, was used. A first panel of experts analyzed the English and French literature to provide a second panel of experts with recommendations to validate. Only the recommendations are presented here, but the full text (arguments + recommendations) is available at the website of the French Paediatric Society: www.sfpediatrie.com.Le Groupe de recherche sur les avancées en pneumo-pédiatrie (GRAPP) a élaboré en 2010 sous l’égide de la Société pédiatrique de pneumologie et d’allergologie (SP2A) des recommandations sur l’évaluation du besoin, les critères de mise en route, les modalités de prescription et de surveillance de l’oxygénothérapie chez l’enfant, en situations aiguës et chroniques. Ces recommandations ont été réalisées selon les modalités du consensus formalisé de la Haute Autorité de santé (HAS) à partir d’une lecture, par un groupe d’experts, de la bibliographie en langue anglaise et française. Les recommandations ont ensuite été validées par un second groupe d’experts. Seules les recommandations sont présentées dans ce texte court, la totalité du texte (argumentaire + recommandations) est accessible sur le site de la Société française de pédiatrie : www.sfpediatrie.com

Recommandations pour l’oxygénothérapie chez l’enfant en situations aiguës et chroniques : évaluation du besoin, critères de mise en route, modalités de prescription et de surveillance

International audienceRecommendations for acute and long-term oxygen therapy (needs assessment, implementation criteria, prescription practices, and follow-up) in children were produced by the Groupe de Recherche sur les Avancées en Pneumo-Pédiatrie (GRAPP) under the auspices of the French Paediatric Pulmonology and Allergology Society (SP2A). The Haute Autorité de Santé (HAS) methodology, based on the Formalized Consensus, was used. A first panel of experts analyzed the English and French literature to provide a second panel of experts with recommendations to validate. Only the recommendations are presented here, but the full text (arguments + recommendations) is available at the website of the French Paediatric Society: www.sfpediatrie.com.Le Groupe de recherche sur les avancées en pneumo-pédiatrie (GRAPP) a élaboré en 2010 sous l’égide de la Société pédiatrique de pneumologie et d’allergologie (SP2A) des recommandations sur l’évaluation du besoin, les critères de mise en route, les modalités de prescription et de surveillance de l’oxygénothérapie chez l’enfant, en situations aiguës et chroniques. Ces recommandations ont été réalisées selon les modalités du consensus formalisé de la Haute Autorité de santé (HAS) à partir d’une lecture, par un groupe d’experts, de la bibliographie en langue anglaise et française. Les recommandations ont ensuite été validées par un second groupe d’experts. Seules les recommandations sont présentées dans ce texte court, la totalité du texte (argumentaire + recommandations) est accessible sur le site de la Société française de pédiatrie : www.sfpediatrie.com