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Gray Et Al. (gray + et_al)

Distribution by Scientific Domains
Life Sciences40%

Selected Abstracts

A mélange of curves , further dialogue about species,area relationships

GLOBAL ECOLOGY, Issue 6 2004
Samuel M. Scheiner
ABSTRACT Scheiner (2003) presented a classification of species,area curves into six types based on the pattern of sampling and how the data are combined to form the curves. Gray et al. (2004) contended that five of those types should be termed ,species-accumulation curves', reserving ,species,area curve' for those based on island-type data. Their proposition contradicts 70 years of usage and confounds curves that are area-explicit with those that are area-undefined. In exploring these issues, I highlight additional aspects of species,area and species-accumulation curves, including the assumption of nesting in Type IV (island) curves, how to convert area-unspecified curves into area curves, and the effects of the grain of the analysis on the properties of the curve. Further exploration, theoretical development, and dialogue are needed before we will understand all the biology that species,area curves summarize. [source]

Projecting the risk of future climate shifts

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2006
David B. Enfield
Abstract Recent research has shown that decadal-to-multidecadal (D2M) climate variability is associated with environmental changes that have important consequences for human activities, such as public health, water availability, frequency of hurricanes, and so forth. As scientists, how do we convert these relationships into decision support products useful to water managers, insurance actuaries, and others, whose principal interest lies in knowing when future climate regime shifts will likely occur that affect long-horizon decisions? Unfortunately, numerical models are far from being able to make deterministic predictions for future D2M climate shifts. However, the recent development of paleoclimate reconstructions of the Atlantic Multidecadal Oscillation (AMO) (Gray et al., 2004) and Pacific Decadal Oscillation (PDO); (MacDonald and Case, 2005) give us a viable alternative: to estimate probability distribution functions from long climate index series that allow us to calculate the probability of future D2M regime shifts. In this paper, we show how probabilistic projections can be developed for a specific climate mode,the AMO as represented by the Gray et al. (2004) tree-ring reconstruction. The methods are robust and can be applied to any D2M climate mode for which a sufficiently long index series exists, as well as to the growing body of paleo-proxy reconstructions that have become available. The target index need not be a paleo-proxy calibrated against a climate index; it may profitably be calibrated against a specific resource of interest, such as stream flow or lake levels. Copyright © 2006 Royal Meteorological Society [source]

A role for the Werner syndrome protein in epigenetic inactivation of the pluripotency factor Oct4

AGING CELL, Issue 4 2010
Johanna A. Smith
Summary Werner syndrome (WS) is an autosomal recessive disorder, the hallmarks of which are premature aging and early onset of neoplastic diseases (Orren, 2006; Bohr, 2008). The gene, whose mutation underlies the WS phenotype, is called WRN. The protein encoded by the WRN gene, WRNp, has DNA helicase activity (Gray et al., 1997; Orren, 2006; Bohr, 2008; Opresko, 2008). Extensive evidence suggests that WRNp plays a role in DNA replication and DNA repair (Chen et al., 2003; Hickson, 2003; Orren, 2006; Turaga et al., 2007; Bohr, 2008). However, WRNp function is not yet fully understood. In this study, we show that WRNp is involved in de novo DNA methylation of the promoter of the Oct4 gene, which encodes a crucial stem cell transcription factor. We demonstrate that WRNp localizes to the Oct4 promoter during retinoic acid-induced differentiation of human pluripotent cells and associates with the de novo methyltransferase Dnmt3b in the chromatin of differentiating pluripotent cells. Depletion of WRNp does not affect demethylation of lysine 4 of the histone H3 at the Oct4 promoter, nor methylation of lysine 9 of H3, but it blocks the recruitment of Dnmt3b to the promoter and results in the reduced methylation of CpG sites within the Oct4 promoter. The lack of DNA methylation was associated with continued, albeit greatly reduced, Oct4 expression in WRN-deficient, retinoic acid-treated cells, which resulted in attenuated differentiation. The presented results reveal a novel function of WRNp and demonstrate that WRNp controls a key step in pluripotent stem cell differentiation. [source]

Forecasting with k -factor Gegenbauer Processes: Theory and Applications

JOURNAL OF FORECASTING, Issue 8 2001
L. Ferrara
Abstract This paper deals with the k -factor extension of the long memory Gegenbauer process proposed by Gray et al. (1989). We give the analytic expression of the prediction function derived from this long memory process and provide the h -step-ahead prediction error when parameters are either known or estimated. We investigate the predictive ability of the k -factor Gegenbauer model on real data of urban transport traffic in the Paris area, in comparison with other short- and long-memory models. Copyright © 2001 John Wiley & Sons, Ltd. [source]

The ,1L -adrenoceptor is an alternative phenotype of the ,1A -adrenoceptor

BRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2008
C P Nelson
Despite over two decades of research, the molecular identity of the ,1L -adrenoceptor phenotype has remained elusive. In this issue of the BJP, Gray et al. (2008) provide persuasive evidence that the in vivo ,1L -adrenoceptor phenotype requires the expression of the ,1A -adrenoceptor gene. They have shown that in mice lacking the functional ,1A -adrenoceptor gene, ,1L -mediated responses to noradrenaline in prostate smooth muscle are substantially attenuated. These findings support earlier evidence that the ,1L -adrenoceptor profile represents a functional phenotype of the ,1A -adrenoceptor gene product, but additional cell background-dependent factors must act in concert with the ,1A -adrenoceptor protein to determine whether an ,1L - or a classical ,1A -adrenoceptor profile is expressed. The challenge remains to establish the nature of these cellular factors and the mechanism(s) by which they influence G-protein-coupled receptor pharmacology. British Journal of Pharmacology (2008) 155, 1,3; doi:fn1; published online 23 June 2008 [source]