Metabolic theory

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Molnar et al 2013 Metabolic theory and host_parasites

Molnar et al 2013 Metabolic theory and host_parasites

Although we expect Metabolic Theory to be particularly useful for broad-scale analyses, the simultaneous development of tactical models (species-specific models with much biological detail; e.g. Grenfell et al. 1987; Mangal et al. 2008) will be key for furthering theory and for improving prediction accuracy in selected systems. For this, the presented approach could still serve as a framework, and offers great flexibility for assessing a wide range of temperature responses both within and between species, as the models allow accounting for any combination of activation energies, inactivation energies and tempera- ture thresholds in development, mortality and other life history com- ponents. Where needed, Metabolic Theory could still reduce data requirements, but tactical models would ideally be parameterised with species-specific laboratory or field data. Such data could reveal addi- tional covariates necessary to determine physiological rates, such as humidity or soil conditions (O’Connor et al. 2006), and it would be straightforward to include such predictors in our models. Additional species-specific life history details (e.g. time-/temperature-dependent egg production, hypobiosis, differing mortality rates between different developmental stages) may also be incorporated and could outline further sensitivities to climate. Ostertagia gruehneri egg production, for example, is seasonal, peaking in summer and dropping dramatically in fall (Stien et al. 2002), and this could interplay with climate warming- induced increases in summer mortality (Fig. 4) to disproportionately affect the species’ ability to persist in future environments. Similarly, tactical models may include biological details to evaluate indirect cli- mate change impacts, for instance, through changes in biodiversity, host range, or host immunity (Thieltges et al. 2008; Dobson 2009; Al- tizer et al. 2011). For instance, in the O. gruehneri-caribou system, phe- nological mismatches may arise between parasite and host availability due to seasonal changes in parasite viability (Fig. 4) and changes to host migration (Sharma et al. 2009). Ultimately, model complexity will depend on data availability and the model objectives, and may be determined using model selection tools (Burnham & Anderson 2002).
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Spatial patterns of species richness in New World coral snakes and the metabolic theory of ecology

Spatial patterns of species richness in New World coral snakes and the metabolic theory of ecology

Metabolic theory has been criticized based on several grounds ( Muller-Landau et al., 2006; van der Meer, 2006; Hawkins et al., 2007a ), and its application to the study of diversity gradients has been extremely controversial as well. Algar et al. (2007) showed that for several datasets in North America (some of then previously analyzed by Allen et al., 2002 ) the relationship between ln-transformed richness and temperature is actually curvilinear, so slopes vary systemati- cally in geographic space. Cassemiro et al. (2007) expanded this approach by showing that even when the MTE prediction of a linear relationship between ln (richness) and temperature ( Allen et al., 2002 ) was met for New World amphibians, the slopes were spatially variable using a geographically weighted regression (GWR) approach (see Foody, 2004; Wang et al., 2005; Bickford and Laffan, 2006 ). This problem can appear because of non-stationarity in the data, i.e. the relationship between variables can vary systematically from one locality, or region, to another ( Cassemiro et al., 2007 ). Thus, in GWR slopes consistent with MTE may be found in some regions but not in others, and this apparently follows the conjecture proposed by Hawkins et al. (2003b) (see also Whittaker et al., 2007 ) in which energy is thought to be the limiting factor in temperate regions, whereas water is more important in tropical regions. This leads to the question of incorporating other environ- mental variables into the analysis and evaluating the partial role of temperature in respect to these other variables.
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Deviations from predictions of the metabolic theory of ecology can be explained by violations of assumptions

Deviations from predictions of the metabolic theory of ecology can be explained by violations of assumptions

Abstract. The metabolic theory of ecology (MTE) is based on models derived from the first principles of thermodynamics and biochemical kinetics. The MTE predicts that the relationship between temperature and species richness of ectotherms should show a specific slope. Testing the validity of this model, however, depends on whether empirical data do not violate assumptions and are obtained within contour conditions. When dealing with richness gradients, the MTE must be empirically tested only for ectothermic organisms at high organization levels and when their body size as well as abundance does not vary with temperature gradients. Here we evaluate whether the magnitude of the deviations in slope expected from the MTE to empirical data for New World amphibians is due to the violations of model assumptions and to lack of generality due to restricting contour conditions. We found that the MTE correctly predicted biodiversity patterns only at higher levels of organization and when assumptions of the basic model were not violated. Approximately 60% of the deviations from the MTE-predicted slope across amphibian families were due to violations of the model assumptions. The hypothesis that richness patterns are a function of environmental temperature is too restrictive and does not take complex environmental and ecological processes into account. However, our results suggest that it may be possible to obtain multiple derivations of the MTE equation if idiosyncrasies in spatial and biological/ ecological issues that are essential to understanding biodiversity patterns are considered.
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Spatial autocorrelation, model selection and hypothesis testing in geographical ecology: implications for testing metabolic theory in New World amphibians

Spatial autocorrelation, model selection and hypothesis testing in geographical ecology: implications for testing metabolic theory in New World amphibians

In the absence of a formal mathemati- cal model to deal with colinearity among temperature and other predic- tors (i.e., that can generate a different theoretical partial slope b to be formally tested, as previously described – see Hawkins et al., 2007b), the alternative to understand patterns of species rich- ness is to identify the best predictive model and then link this model with the available theories to explain geo- graphic patterns in richness (e.g., Ha- wkins et al., 2003). Within the context of metabolic theory, we can at least verify if temperature is one of the pre- dictors retained in the best environmen- tal model, providing support for a for- mal modelling strategy to understand how collinearity could be incorporated into metabolic theory. It is also possi- ble to verify that the partial coefficient of temperature (i.e., taking into account all other predictors) is still close to MTE predictions. In this case, it might appropriate to abandon the idea of a formal hypothesis testing and shift to a model selection framework under in- formation theory (i.e., we are not inte- rested in simply rejecting the null hypo- thesis of b = 0 for all predictors; rather, it is more interest to compare multiple potential alternative models and to ve- rify the parameter estimated.
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Elucidating the global elapid (Squamata) richness pattern under metabolic theory of ecology

Elucidating the global elapid (Squamata) richness pattern under metabolic theory of ecology

Environmental determinants of global patterns in species richness are still uncertain. The Metabolic Theory of Ecology (MTE) proposes that species richness patterns can be explained by environmental temperature acting on the metabolism of ectothermic organisms. However, the generality of this theory has been questioned due to its low fit to the geographic variation in species richness of different taxo- nomic groups. Here, we investigated whether the MTE drives elapid richness, testing the non- stationarity of the relationship between the natural logarithm of species richness (ln S) and the in- verse function of temperature (1/kT) using a geographically weighted regression (GWR). The relationship between ln S and 1/kT varied systematically over space and showed non-stationarity. Few tropical lo- cations were consistent with MTE predictions, whereas other regions fitted differently. Although the slope of the GWR model ranged from low to high, the temperature did not predict species richness strongly on average and did not limit the upper values of richness. The response of richness to tem- perature in some areas might reflect a recent history of colonization and diversification of species across tropical and subtropical regions. In regions not affected by temperature, species richness should be structured by other biotic and abiotic interactions. This scenario reveals that the non-stationarity of the relationship would be linked to idiosyncrasies in the sample sites, which can drift the magnitude or change the relationship between species richness and temperature throughout space.
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A global evaluation of metabolic theory as an explanation for terrestrial species richness gradients

A global evaluation of metabolic theory as an explanation for terrestrial species richness gradients

The Natural History Museum, Biogeography and Conservation Laboratory, Cromwell Road, London SW7 5BD United Kingdom Abstract. We compiled 46 broadscale data sets of species richness for a wide range of terrestrial plant, invertebrate, and ectothermic vertebrate groups in all parts of the world to test the ability of metabolic theory to account for observed diversity gradients. The theory makes two related predictions: (1) ln-transformed richness is linearly associated with a linear, inverse transformation of annual temperature, and (2) the slope of the relationship is near 0.65. Of the 46 data sets, 14 had no significant relationship; of the remaining 32, nine were linear, meeting prediction 1. Model I (ordinary least squares, OLS) and model II (reduced major axis, RMA) regressions then tested the linear slopes against prediction 2. In the 23 data sets having nonlinear relationships between richness and temperature, split-line regression divided the data into linear components, and regressions were done on each component to test prediction 2 for subsets of the data. Of the 46 data sets analyzed in their entirety using OLS regression, one was consistent with metabolic theory (meeting both predictions), and one was possibly consistent. Using RMA regression, no data sets were consistent. Of 67 analyses of prediction 2 using OLS regression on all linear data sets and subsets, two were consistent with the prediction, and four were possibly consistent. Using RMA regression, one was consistent (albeit weakly), and four were possibly consistent. We also found that the relationship between richness and temperature is both taxonomically and geographically conditional, and there is no evidence for a universal response of diversity to temperature. Meta-analyses confirmed significant heterogeneity in slopes among data sets, and the combined slopes across studies were significantly lower than the range of slopes predicted by metabolic theory based on both OLS and RMA regressions. We conclude that metabolic theory, as currently formulated, is a poor predictor of observed diversity gradients in most terrestrial systems.
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Metabolic theory and diversity gradients: where do we go from here?

Metabolic theory and diversity gradients: where do we go from here?

A global evaluation of metabolic theory as an explanation for terrestrial species richness gradients.. Very high resolution interpolated climate.[r]

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Optimization strategies for metabolic networks

Optimization strategies for metabolic networks

Current metabolic engineering processes allow to manipulate metabolic networks to improve the desired characteristics of biochemical systems [1]. These manip- ulations may lead to the maximization of the normal product yield or redirect the production to a flux that was residual or non-significant in the original network. The high level of uncertainty in metabolic network models knowledge makes it extremely difficult to deter- mine what are the required manipulations needed to attain a given objective. Since an heuristic approach to such problems does not allow to explore the maximum potential of metabolic engineering, two approaches are usually considered when modeling metabolic networks. Kinetic models describe the complete dynamics of the network, and have proven useful to implement optimi-
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Psoriasis and Metabolic Syndrome

Psoriasis and Metabolic Syndrome

Sommer et al. (33) showed, in a cross-sectional study with 581 hospitalized patients with psoriasis and 1044 controls, that the patients had a significant- ly increased risk of metabolic syndrome than controls (OR=4.22; 95% Confidence interval (CI)=2.06-8.65). In a hospital-based case-control study that included 338 patients with psoriasis and 334 patients with other skin diseases, Gisondi et al. found that the pre- dominance of metabolic syndrome was significantly higher in the psoriasis group than in the control group (30.1% vs 20.6%; OR=1.65; 95% CI=1.16-2.35). Concerning the individual components of the meta- bolic syndrome, they found that the predominance of hypertrygliceridemia and abdominal obesity was also increased in psoriasis patients compared to controls, while no difference was observed between cases and controls with respect to low levels of HDL, DM, and hypertension (32). A cross-sectional study conducted in Israel using the database of the Clalit Health Servic- es, with 16851 patients with psoriasis and 48681 con- trols, demonstrated a significant association of pso- riasis with metabolic syndrome (OR=1.3; 95% CI=1.1- 1.4) (34). In the USA, Love et al. reported significant increased risk of metabolic syndrome in patients with psoriasis compared with controls even after adjust- ment for age, sex, race/ethnicity, smoking, and C-re- active protein levels (OR=1.96; 95% CI=1.01-3.77) (44). In a population-base prevalence study in the United Kingdom using the Health Improvement Network da- tabase, with 4065 psoriasis patients and 40650 control subjects, metabolic syndrome was identified in 34%
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Stakeholder Theory vs Agency Theory in Portuguese NPO - an Endowment Approach

Stakeholder Theory vs Agency Theory in Portuguese NPO - an Endowment Approach

For a proper framework of this study, given that NPO lacks shareholders, it was included the assumptions of the Stakeholder Theory. The Stakeholder Theory differs from the Agency Theory in two perspectives: it does not restrict the group of principals to only shareholders and says that the market is inefficient contrary to the position of market efficiency of the principal-agent theory (Hill and Jones, 1992). With this, the notion of principal must be bigger than previously defined on the theory of agency. For the development of this work, principal will be all relevant stakeholders, internal or external, as defined next: the term stakeholders refer to groups of constituents who have a legitimacy claim on the firm (Freeman, 1984; Pearce, 1982 in Hill and Jones, 1992). The use of this theory follows the arguments presented in Van Puyvelde et al.,2012. In this paper, they attribute the various relations between NPO and stakeholder (either internal or external) as similar to principal-agent relationships. Regarding this dissertation, this argument is applicable to validate the use of the Excess Endowment as the dependent variable in the regressions as well indirectly the relations between donors and managers are assessed in principal-agent relations.
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Convexity in semi-metric spaces, decision theory and consumer theory

Convexity in semi-metric spaces, decision theory and consumer theory

Convexity is a concept usually developed in vector spaces. However since the seventies of the 20th century, convexity is also study in metric spaces in general. In this paper we develop a theory of convexity - including convex real functions - in semi-metric spaces and we suggest some possible applications in Economics and Decision Theory.

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Metabolic dysfunction and asthma

Metabolic dysfunction and asthma

metabolism but accumulating experimental findings support their anti-in flammatory properties and potential clinical ben- e fits of PPAR-gamma agonists in the treatment of asthma. 81 However, these drugs ef ficacy remains controversial and larger randomized clinical trials (RCTs) are lacking. PPAR- gamma agonists are also associated with important side effects, which may be possibly minimized by administration via inhalation rather than systemic delivery, or through com- bination of drugs at lower concentrations. 81 Likewise, the metabolic and immunomodulatory properties of statins, tra- ditionally used to manage cholesterol levels, have led to several studies evaluating its role for the treatment of asthma. Epidemiological and observational studies pointed towards therapeutic bene fits in asthma, but RCTs using oral statins yielded con flicting results. 82 – 84 RCTs in severe asthma are lacking and studies using statins delivered by inhalation are also warranted. 84 Evidence of clinical bene fit of metformin in asthma is also growing, 85 – 87 although it has seldom been investigated in real-life clinical settings. In particular, a decrease in asthma exacerbations in response to metformin has been reported in different populations. 88 , 89 This warrants further investigation. Future research may also address whether the effects of metformin are limited to patients with diabetes or whether it could bring advantage also in case of obesity, insulin resistance or the metabolic syndrome. Currently, the role of these and other pharmacological stra- tegies addressing metabolic syndrome conditions in asthma needs appropriate study design and careful analysis to avoid biases and allow successful results to the individual patient.
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Brentano's 'revised' theory consciousness

Brentano's 'revised' theory consciousness

distinction. Moreover, as I have argued, while we can accept that conscious mental states do necessarily involve a subjective character, as many philosophers have recently proposed, it is not necessary to postulate the existence of a mental agent in Brentano’s strong ontological sense, in order to account for the subjective character. In light of a reductionist metaphysics of persons, à la Parfit, the views suggested by 5* and 6 can also account for subjective character. In so far as 5* and 6 would seem to presuppose such a reductionist metaphysics of persons, however, they must postulate the existence of mental conscious states which are inscribed within some psycho-physical continuum. This is hardly a problem, however. Statement 5’, on the other hand, lends itself to a more radically anti-realist view, because it is not committed to the existence of such a psycho-physical continuum. On such a radical view, conscious mental states would be just as much conceptual constructions, as the primary object and as the subject. While 5* is the view I find most appealing, for the reasons I have suggested, and 6 seems problematic, given that it requires a dubious relation of acquaintance, I must admit that I do not find 5’ implausible. Be that as it may, one thing is clear: Brentano’s revised theory of consciousness is indeed implausible and 5*, 6, or 5’ should be preferred.
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Cubic Galileon theory in the Effective Field theory formalism: a cosmological study

Cubic Galileon theory in the Effective Field theory formalism: a cosmological study

O desafio surge, no entanto, do facto de cada modelo ser, geralmente, descrito por um conjunto de equa¸ c˜ oes e parˆ ametros espec´ıficos. Sendo ` a partida necess´ ario um tratamento indi- vidual para cada proposta. De modo a agilizar e simplificar o processo de teste das propostas existentes, procurou-se encontrar um formalismo mais abrangente, sendo capaz de descrever diferentes modelos de EE/GM e que em simultˆ aneo oferecesse uma forma mais pr´ atica de os investigar. V´ arias abordagens foram ent˜ ao desenvolvidas, de entre as quais se destaca a Teoria de Campo Efetivo (Effective Field Theory - EFT) por manter uma maior conex˜ ao com a teoria de gravita¸ c˜ ao subjacente. A EFT oferece um formalismo geral, ou seja, sem dependˆ encia de um modelo espec´ıfico, que descreve a evolu¸ c˜ ao de perturba¸ c˜ oes lineares em modelos que apresentem um ´ unico grau de liberdade escalar extra. Esta revela ser uma abordagem englobante uma vez que a maioria dos modelos de EE/GM propostos podem ser descritos como modifica¸ c˜ oes da RG atrav´ es da adi¸ c˜ ao de um campo escalar extra. Dentro do formalismo da EFT, o comportamento tanto ao n´ıvel da hist´ oria de expans˜ ao como ao n´ıvel das perturba¸ c˜ oes passa a ser descrito por um conjunto de coeficientes com dependˆ encia temporal, designados por fun¸ c˜ oes EFT, que s˜ ao introduzidos na formula¸ c˜ ao da a¸ c˜ ao que descreve a teoria. Esta constru¸ c˜ ao permite que a EFT tenha uma aplica¸ c˜ ao dual. Por um lado, ´ e poss´ıvel investigar o efeito de ligar ou desligar um certo conjunto de coeficientes, sem selecionar nenhum modelo em particular. Por outro lado, ´
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ON THEORY MULTIPLE CONTRACTION

ON THEORY MULTIPLE CONTRACTION

The AGM model of belief change is considered the standard model in the Logic of Theory Change. In such framework essentially three kinds of changes are con- sidered, namely expansions, contractions and revisions. However, in their seminal paper [AGM85], Alchourr´on, G¨ardenfors and Makinson have considered only expan- sions and contractions as basic operations and treated revisions as being operations which are derived from those two. Such option was taken in accordance with the ar- guments presented by Levi [Lev77] supporting that all acceptable revision functions can be obtained by a two steps procedure consisting of a contraction followed by an expansion, as described in equation (2.1), which is, nowadays, commonly known as the Levi identity.
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Revisiting modern portfolio theory

Revisiting modern portfolio theory

The above argument clarifies an important practical issue regarding Diversification. While Finance Theory argues in favor of a well-diversified portfolio, as a mean of reducing idiosyncratic risk; the truth is that a variance minimizing exercise usually results in fairly concentrated portfolios. For instance, a rule of thumb in the practice of Asset Management is that a portfolio comprising of 10 to 15 1 securities would already be sufficiently diversified;

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A theory of weekly specials

A theory of weekly specials

Surprisingly, this result shows that competing retailers facing fixed costs will never charge the same prices even though they access the same technology and serve the[r]

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Hybrid Auctions I: Theory

Hybrid Auctions I: Theory

If at least one more bidder submitted a bid su¢ciently close to the highest bid (that is, if the di¤erence between this bid and the highest bid is smaller than the predetermined amount o[r]

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Toxic and Metabolic Myelopathies

Toxic and Metabolic Myelopathies

Myelopathy describes any neurologic de ficit related to the spinal cord. It is most commonly caused by its compression by neoplasms, degenerative disc disease, trauma, or infection. Less common causes of myelopathy include spinal cord tumors, infection, in flammatory, neurodegenerative, vascular, toxic, and metabolic disorders. Conditions affecting the spinal cord must be recognized as early as possible to prevent progression that may lead to permanent disability. Biopsy is rarely performed, thus the diagnosis and management rely on patient 's history, physical examination, laboratory results, and imaging findings. Here we review the clinical presentations, pathophysiological mechanisms, and magnetic resonance imaging findings of myelopathies related to metabolic or toxic etiologies.
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Texts on game theory

Texts on game theory

This article have as objective study a problem very important that hospitals confront dailythe costs (are linked to PPI (Physician Preference Items) of physicians) with the providers (the latter may send sales representatives to train and demonstrate the new PPIs to physicians in order to facilitate their implementation more quickly). Cara J. Dienes (2011); the author of this dissertation; tries to solve this gap with the help of Game Theory. When the different tests were carried out, it was verified that the games with sales representatives indicate that if they train and assist the physicians, they increase the frequencies of the PPIs where the producer wins. Increasing a sales representative’s ability to provide effective physician training leads to a positive effect of physician‘s payoffs, where tests lead one to conclude that they are almost always better when have a sales representative who provides effective training, contrary to one that does not. To finalize our study we added another test, we were looking for professional opinions on adopting a new generation of product/PPI in the long run. Where we can conclude that, with the right incentives, professionals may prefer to make long-term adoptions.
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