University of Costa Rica

About: University of Costa Rica is a education organization based out in San José, Costa Rica. It is known for research contribution in the topics: Population & Venom. The organization has 9817 authors who have published 16781 publications receiving 238208 citations. The organization is also known as: UCR & Universidad de Costa Rica.

Light-Front Dynamics and AdS/QCD Correspondence: Gravitational Form Factors of Composite Hadrons

Abstract: Light-front holography is a remarkable feature of the AdS/CFT correspondence between gravity in AdS space and conformal field theories in physical space-time; it allows string modes $\ensuremath{\Phi}(z)$ in the anti-de Sitter (AdS) fifth dimension to be precisely mapped to the light-front wave functions of hadrons in physical space-time in terms of a specific light-front impact variable $\ensuremath{\zeta}$ which measures the separation of the quark and gluonic constituents within the hadron. This mapping was originally obtained by matching the exact expression for electromagnetic current matrix elements in AdS space with the corresponding exact expression for the current matrix element using light-front theory in physical space-time. In this paper we show that one obtains the identical holographic mapping using matrix elements of the energy-momentum tensor. To prove this, we show that there exists a correspondence between the matrix elements of the energy-momentum tensor of the fundamental hadronic constituents in QCD with the transition amplitudes describing the interaction of string modes in AdS space with an external graviton field which propagates in the AdS interior. The agreement of the results for electromagnetic and gravitational hadronic transition amplitudes provides an important consistency test and verification of holographic mapping from AdS to physical observables defined on the light front.

Distribution models for the amphibian chytrid Batrachochytrium dendrobatidis in Costa Rica: proposing climatic refuges as a conservation tool

Abstract: Aim: We use novel data on the occurrence of the amphibian chytrid fungus Batrachochytrium dendrobatidis in Costa Rica to model its potential distribution in that country. Location: Lowland and montane areas of Costa Rica. Methods: We use published and new data on the presence of B. dendrobatidis on 647 amphibians (35 species). Screening was performed through histological techniques by which 156 sites were surveyed. Of these, 21 were found to have the amphibian chytrid. Maxent, a presence-only distribution modelling technique, was used to create 100 predictions of B. dendrobatidis occurrence, of which the most accurate 10 (based on area under the receiver-operating characteristic curve) were chosen to create a composite distribution model. This approach increased confidence in model predictions, distinguishing areas of high probability of occurrence and low variability across model runs (higher confidence) from those with high probability but high variability (lower confidence). Results: Predicted distribution patterns were not uniform along Costa Rica's mountains, where most amphibian declines have occurred. The pathogen was predicted to occur with greater probability on the Caribbean slopes than on the Pacific slopes. While high temperature seems to constrain the distribution of the pathogen, areas that also have small amounts of rainfall during the driest period of the year were predicted to have low probability of B. dendrobatidis occurrence. Main conclusions: The model predicts that the Santa Elena Peninsula and the Central Valley have low probabilities of B. dendrobatidis occurrence, suggesting that they could function as refuges for amphibians. In such refugial areas, one could expect B. dendrobatidis to be absent, or to be present in low abundance (rendering an epidemic outbreak of chytridiomycosis unlikely). Craugastor ranoides, which belongs to a group of frogs particularly sensitive to chytridiomycosis outbreaks, persists in the hot and seasonally dry Santa Elena Peninsula but disappeared in the nearby colder and more humid Guanacaste Volcanic Chain. This information suggests that climatic refuges, where environmental conditions prevent disease outbreaks, could be an important component in amphibian conservation.

Integrated care pathways for airway diseases (AIRWAYS-ICPs).

Abstract: The objective of Integrated Care Pathways for Airway Diseases (AIRWAYS-ICPs) is to launch a collaboration to develop multi-sectoral care pathways for chronic respiratory diseases in European countries and regions. AIRWAYS-ICPs has strategic relevance to the European Union Health Strategy and will add value to existing public health knowledge by: 1) proposing a common framework of care pathways for chronic respiratory diseases, which will facilitate comparability and trans-national initiatives; 2) informing cost-effective policy development, strengthening in particular those on smoking and environmental exposure; 3) aiding risk stratification in chronic disease patients, using a common strategy; 4) having a significant impact on the health of citizens in the short term (reduction of morbidity, improvement of education in children and of work in adults) and in the long-term (healthy ageing); 5) proposing a common simulation tool to assist physicians; and 6) ultimately reducing the healthcare burden (emergency visits, avoidable hospitalisations, disability and costs) while improving quality of life. In the longer term, the incidence of disease may be reduced by innovative prevention strategies. AIRWAYS-ICPs was initiated by Area 5 of the Action Plan B3 of the European Innovation Partnership on Active and Healthy Ageing. All stakeholders are involved (health and social care, patients, and policy makers).

Recent origin and rapid speciation of Neotropical orchids in the world's richest plant biodiversity hotspot.

Abstract: The Andean mountains of South America are the most species-rich biodiversity hotspot worldwide with c. 15% of the world's plant species, in only 1% of the world's land surface. Orchids are a key element of the Andean flora, and one of the most prominent components of the Neotropical epiphyte diversity, yet very little is known about their origin and diversification. We address this knowledge gap by inferring the biogeographical history and diversification dynamics of the two largest Neotropical orchid groups (Cymbidieae and Pleurothallidinae), using two unparalleled, densely sampled orchid phylogenies (including more than 400 newly generated DNA sequences), comparative phylogenetic methods, geological and biological datasets. We find that the majority of Andean orchid lineages only originated in the last 20-15 million yr. Andean lineages are derived from lowland Amazonian ancestors, with additional contributions from Central America and the Antilles. Species diversification is correlated with Andean orogeny, and multiple migrations and recolonizations across the Andes indicate that mountains do not constrain orchid dispersal over long timescales. Our study sheds new light on the timing and geography of a major Neotropical diversification, and suggests that mountain uplift promotes species diversification across all elevational zones.

Ecological and Evolutionary Implications of Bird Pollination

Abstract: This paper addresses the question of how, and under what ecological circumstances, bird pollination will be optimal for a plant, and which or how many of the available nectar-feeding bird species will be optimal pollen vectors. Pollination by birds is energetically expensive for the plants, and should accur only when birds can mediate optimal patterns of pollen flow and seed set. Each nectar-feeding bird has potential advantages and disadvantages as a pollen vector, related to its size, morphology, and foraging behavior. Which available bird is the optimal pollinator depends on the plant's growth habit, spatial distribution, and breeding system. The various adaptations shown by plants favoring one pollinator over another all revolve around the secretion of nectar and the manner of presenting it to the birds. However, other aspects of plant morphology, physiology, ecology, or life cycle may affect the production and presentation of nectar, and influence plant-pollinator coevolution. Many question remain regarding the interrelations between pollination and the total biology of the plant; bird pollination systems may prove fruitful in yielding meaningful answers.