76,626 research outputs found
Arbuscular mycorrhizal fungi as mediators of ecosystem responses to nitrogen deposition: A trait-based predictive framework
Anthropogenic nitrogen (N) deposition is exposing plants and their arbuscular mycorrhizal fungi (AMFs) to elevated N availability, often leading to shifts in communities of AMF. However, physiological trade-offs among AMF taxa in their response to N enrichment vs the ability to acquire other soil nutrients could have negative effects on plant and ecosystem productivity. It follows that information on the functional traits of AMF taxa can be used to generate predictions of their potential role in mediating ecosystem responses to N enrichment. Arbuscular mycorrhizal fungi taxa that produce extensive networks of external hyphae should forage for N and phosphorus (P) more effectively, but these services incur greater carbon (C) costs to the plant. If N enrichment ameliorates plant nutrient limitation, then plants may reduce C available for AMF, which in turn could eliminate AMF taxa with large extensive external hyphae from the soil community. As a result, the remaining AMF taxa may confer less P benefit to their host plants. Using a synthesis of data from the literature, we found that the ability of a taxon to persist in the face of increasing soil N availability was particularly high in isolates from the genus Glomus, but especially low among the Gigasporaceae. Across AMF genera, our data support the prediction that AMF with a tolerance for high soil N may confer a lower P benefit to their host plant. Relationships between high N tolerance and production of external hyphae were mixed. Synthesis. If the relationship between N tolerance and plant P benefit is widespread, then shifts in arbuscular mycorrhizal fungi communities associated with N deposition could have negative consequences for the ability of plants to acquire P and possibly other nutrients via a mycorrhizal pathway. Based on this relationship, we predict that arbuscular mycorrhizal fungi responses could constrain net primary productivity in P-limited ecosystems exposed to N enrichment. This prediction could be tested in future empirical and modelling studies
Algorithms for geodesics
Algorithms for the computation of geodesics on an ellipsoid of revolution are
given. These provide accurate, robust, and fast solutions to the direct and
inverse geodesic problems and they allow differential and integral properties
of geodesics to be computed.Comment: LaTex, 12 pages, 8 figures. Version 2 corrects some errors and adds
numerical examples. Supplementary material is available at
http://geographiclib.sourceforge.net/geod.htm
ADVISE: Symbolism and External Knowledge for Decoding Advertisements
In order to convey the most content in their limited space, advertisements
embed references to outside knowledge via symbolism. For example, a motorcycle
stands for adventure (a positive property the ad wants associated with the
product being sold), and a gun stands for danger (a negative property to
dissuade viewers from undesirable behaviors). We show how to use symbolic
references to better understand the meaning of an ad. We further show how
anchoring ad understanding in general-purpose object recognition and image
captioning improves results. We formulate the ad understanding task as matching
the ad image to human-generated statements that describe the action that the ad
prompts, and the rationale it provides for taking this action. Our proposed
method outperforms the state of the art on this task, and on an alternative
formulation of question-answering on ads. We show additional applications of
our learned representations for matching ads to slogans, and clustering ads
according to their topic, without extra training.Comment: To appear, Proceedings of the European Conference on Computer Vision
(ECCV
Asthma Genetic Factors
A asma brônquica é uma doença inflamatória crónica das vias aéreas, de prevalência crescente, particularmente na infância, sendo considerado um importante
problema de saúde pública.
É reconhecidamente uma doença de transmissão familiar, sendo um desafio a descrição e potencial identificação dos genes envolvidos na sua génese.
Pretende-se com o presente artigo de revisão explicitar exaustivamente os genes associados a esta patologia,
bem como esclarecer os métodos laboratoriais que permitem a sua identificação
Heterogeneity among Mycobacterium ulcerans isolates from Africa
Mycobacterium ulcerans causes Buruli ulcer, an ulcerative skin disease in tropical and subtropical areas. Despite restricted genetic diversity, mycobacterial interspersed repetitive unit-variable-number tandem repeat analysis on M. ulcerans revealed 3 genotypes from different African countries. It is the first time this typing method succeeded directly on patient samples
BenefÃcios do Humor na Saúde
O humor contribui para a saúde e bem-estar das pessoas. Este desempenha uma função especial nas interações humanas, permitindo dizer-se que possibilita um encontro e acompanhamento com o
Outro. Analisar estudos publicados entre 2006 e 2011, de modo a identificar o papel que o humor tem na vida e saúde das pessoas.
Materiais e Métodos: Revisão Sistemática de Literatura através do método PICOS.
Foram selecionados artigos a partir da pesquisa em bases de dados eletrónicas (EBSCO e b-on), repositórios nacionais, SciElo e Google Scholar.
Resultados: Foram incluÃdos 26 estudos de 13 paÃses em que os participantes eram estudantes, profissionais de saúde, idosos e pessoas com doença/dor crónica. Os estudos enquadram-se no paradigma qualitativo e quantitativo, apresentando assim, diferentes desenhos de investigação.
Discussão e Conclusões: O humor apresenta benefÃcios a nÃvel organizacional e cuidados de saúde.
Quando se utiliza humor as equipas são mais produtivas, coesas, mostram menor nÃvel de
stress e estão mais motivadas e satisfeitas. Na saúde e na vida das pessoas o humor ajuda a promover o bem-estar; a lidar com situações difÃceis e desagradáveis, a reduzir a tensão, o stress e o desconforto; aumentar a tolerância à dor, e fortalecer o sistema imunitário
Uncomfortable images produce non-sparse responses in a model of primary visual cortex
The processing of visual information by the nervous
system requires significant metabolic resources. To
minimise the energy needed, our visual system
appears to be optimised to encode typical natural
images as efficiently as possible. One consequence
of this is that some atypical images will produce
inefficient, non-optimal responses.Here, we show that
images that are reported to be uncomfortable to view,
and that can trigger migraine attacks and epileptic
seizures, produce relatively non-sparse responses in a
model of the primary visual cortex. In comparison to
the responses to typical inputs, responses to aversive
images were larger and less sparse. We propose that
this difference in the neural population response may
be one cause of visual discomfort in the general
population, and can produce more extreme responses
in clinical populations such as migraine and epilepsy
sufferers
CSF protein biomarkers predicting longitudinal reduction of CSF β-amyloid42 in cognitively healthy elders.
β-amyloid (Aβ) plaque accumulation is a hallmark of Alzheimer's disease (AD). It is believed to start many years prior to symptoms and is reflected by reduced cerebrospinal fluid (CSF) levels of the peptide Aβ1-42 (Aβ42). Here we tested the hypothesis that baseline levels of CSF proteins involved in microglia activity, synaptic function and Aβ metabolism predict the development of Aβ plaques, assessed by longitudinal CSF Aβ42 decrease in cognitively healthy people. Forty-six healthy people with three to four serial CSF samples were included (mean follow-up 3 years, range 2-4 years). There was an overall reduction in Aβ42 from a mean concentration of 211-195 pg ml(-1) after 4 years. Linear mixed-effects models using longitudinal Aβ42 as the response variable, and baseline proteins as explanatory variables (n=69 proteins potentially relevant for Aβ metabolism, microglia or synaptic/neuronal function), identified 10 proteins with significant effects on longitudinal Aβ42. The most significant proteins were angiotensin-converting enzyme (ACE, P=0.009), Chromogranin A (CgA, P=0.009) and Axl receptor tyrosine kinase (AXL, P=0.009). Receiver-operating characteristic analysis identified 11 proteins with significant effects on longitudinal Aβ42 (largely overlapping with the proteins identified by linear mixed-effects models). Several proteins (including ACE, CgA and AXL) were associated with Aβ42 reduction only in subjects with normal baseline Aβ42, and not in subjects with reduced baseline Aβ42. We conclude that baseline CSF proteins related to Aβ metabolism, microglia activity or synapses predict longitudinal Aβ42 reduction in cognitively healthy elders. The finding that some proteins only predict Aβ42 reduction in subjects with normal baseline Aβ42 suggest that they predict future development of the brain Aβ pathology at the earliest stages of AD, prior to widespread development of Aβ plaques
The modulating influence of Indian Ocean sea surface temperatures on Australian region seasonal tropical cyclone counts
© 2017 American Meteorological Society. The Australian region seasonal tropical cyclone count (TCC) maintained a robust statistical relationship with El Niño-Southern Oscillation (ENSO), with skillful forecasts of above (below) average TCC during La Niña (El Niño) years from 1969 until about 1998, weakening thereafter. The current study identifies an additional climate driver that mitigates the loss of predictive skill for Australian TCC after about 1998. It is found that the seasonal Australian TCC is strongly modulated by a southwest-to-northeast-oriented dipole in Indian Ocean sea surface temperature anomalies (SSTAs), referred to here as the transverse Indian Ocean dipole (TIOD). The TIOD emerges as the leading mode of detrended Indian Ocean SSTAs in the Southern Hemisphere during late winter and spring. Active (inactive) TC seasons are linked to positive (negative) TIOD phases, most notably during August-October immediately preceding the TC season, when SSTAs northwest of Australia, in the northeast pole of the TIOD, are positive (negative). To provide a physical interpretation of the TIOD-TCC relationship, 850-hPa zonal winds, 850-hPa relative vorticity, and 600-hPa relative humidity are composited for positive and negative TIOD phases, providing results consistent with observed TCC modulation. Correlations between ENSO and TCC weaken from 1998 onward, becoming statistically insignificant, whereas the TIOD-TCC correlation remains statistically significant until 2003. Overall, TIOD outperforms Niño-4 SSTA as a TCC predictor (46% skill increase since about 1998), when used individually or with Niño-4. The combination of TIOD and Niño 4 provide a skill increase (up to 33%) over climatology, demonstrating reliably accurate seasonal predictions of Australian region TCC
Budget feasible mechanisms on matroids
Motivated by many practical applications, in this paper we study budget feasible mechanisms where the goal is to procure independent sets from matroids. More specifically, we are given a matroid =(,) where each ground (indivisible) element is a selfish agent. The cost of each element (i.e., for selling the item or performing a service) is only known to the element itself. There is a buyer with a budget having additive valuations over the set of elements E. The goal is to design an incentive compatible (truthful) budget feasible mechanism which procures an independent set of the matroid under the given budget that yields the largest value possible to the buyer. Our result is a deterministic, polynomial-time, individually rational, truthful and budget feasible mechanism with 4-approximation to the optimal independent set. Then, we extend our mechanism to the setting of matroid intersections in which the goal is to procure common independent sets from multiple matroids. We show that, given a polynomial time deterministic blackbox that returns -approximation solutions to the matroid intersection problem, there exists a deterministic, polynomial time, individually rational, truthful and budget feasible mechanism with (3+1) -approximation to the optimal common independent set
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