6,869 research outputs found
Climateâdriven evolutionary change in reproductive and earlyâacting lifeâhistory traits in the perennial grass Festuca ovina
Reproductive and earlyâacting lifeâhistory traits are likely to be particularly important determinants of plant fitness under a changing climate. There have, however, been few robust tests of the evolution of these traits under chronic climate change in natural ecosystems. Such studies are urgently needed, to evaluate the contribution of evolutionary change to population persistence.
Here, we examine climateâdriven evolutionary change in reproductive and earlyâacting plant lifeâhistory traits in the longâlived perennial plant, Festuca ovina.
We collected established plants of F. ovina from speciesârich calcareous grassland at the Buxton Climate Change Impacts Laboratory (BCCIL), after 17 years of in situ experimental drought treatment.
P1 plants collected from droughtâtreated and control (ambient climate) plots at BCCIL were used to create an openâpollinated F1 progeny array, which was subsequently validated using microsatellite markers to establish a robust biâparental pedigree. We measured the timing of germination and seed mass in the F1 progeny, the P1 paternal contribution to F1 offspring (paternal reproductive success), and assessed the effects of flowering time on the mating system.
F1 seed with ancestry in droughtâtreated plots at BCCIL germinated significantly later than seed derived from individuals from control plots. P1 plants from the drought treatment flowered significantly earlier than those from the control plots in summer 2012, but not in 2013. Male reproductive success was also lower in P1 plants collected from drought plots than those from control plots. Furthermore, our pedigree revealed that mating among parents of the F1 progeny had been assortative with respect to flowering time.
Synthesis. Our study shows that chronic drought treatment at Buxton Climate Change Impacts Laboratory has driven rapid evolutionary change in reproductive and earlyâacting lifeâhistory traits in Festuca ovina, and suggests that evolutionary differentiation may be reinforced through changes in flowering time that reduce the potential for gene flow
QCD Predictions for the Transverse Energy Flow in Deep-Inelastic Scattering in the Small x HERA Regime
The distribution of transverse energy, , which accompanies
deep-inelastic electron-proton scattering at small , is predicted in the
central region away from the current jet and proton remnants. We use BFKL
dynamics, which arises from the summation of multiple gluon emissions at small
, to derive an analytic expression for the flow. One interesting
feature is an increase of the distribution with
decreasing , where . We perform a
numerical study to examine the possibility of using characteristics of the
distribution as a means of identifying BFKL dynamics at HERA.Comment: 16 pages, REVTEX 3.0, no figures. (Hardcopies of figures available on
request from Professor A.D. Martin, Department of Physics, University of
Durham, DH1 3LE, England.) Durham preprint : DTP/94/0
Properties of the BFKL equation and structure function predictions for HERA
The general properties of the Lipatov or BFKL equation are reviewed.
Modifications to the infrared region are proposed. Numerical predictions for
the deep-inelastic electron-proton structure functions at small are
presented and confronted with recent HERA measurements.Comment: 21 pages, 11 figures, Latex file, Durham preprint DTP 92/2
THE GLUON DISTRIBUTION AT SMALL x OBTAINED FROM A UNIFIED EVOLUTION EQUATION.
We solve a unified integral equation to obtain the and
dependence of the gluon distribution of a proton in the small regime; where
and are the longitudinal momentum fraction and the transverse
momentum of the gluon probed at a scale . The equation generates a gluon
with a steep behaviour, with , and a
distribution which broadens as decreases. We compare our solutions with, on
the one hand, those that we obtain using the double-leading-logarithm
approximation to Altarelli-Parisi evolution and, on the other hand, to those
that we determine from the BFKL equation.Comment: LaTeX file with 10 postscript figures (uuencoded
The description of F2 at small x incorporating angular ordering
We study the perturbative QCD description of the HERA measurements of using a gluon distribution that is obtained from an evolution
incorporating angular ordering of the gluon emissions, and which embodies both
GLAP and BFKL dynamics. We compare the predictions with recent HERA data for
. We present estimates of the charm component and of .Comment: 8 LaTeX pages + 4 uuencoded figure
Mathematically gifted and talented learners: Theory and practice
This is an Author's Accepted Manuscript of an article published in International Journal of Mathematical Education in Science and Technology, 40(2), 213-228, 2009, copyright Taylor & Francis, available online at: http://www.tandfonline.com/10.1080/00207390802566907.There is growing recognition of the special needs of mathematically gifted learners. This article reviews policy developments and current research and theory on giftedness in mathematics. It includes a discussion of the nature of mathematical ability as well as the factors that make up giftedness in mathematics. The article is set in the context of current developments in Mathematics Education and Gifted Education in the UK and their implications for Science and Technology. It argues that early identification and appropriate provision for younger mathematically promising pupils capitalizes on an intellectual resource which could provide future mathematicans as well as specialists in Science or Technology. Drawing on a Vygotskian framework, it is suggested that the mathematically gifted require appropriate cognitive challenges as well as attitudinally and motivationally enhancing experiences. In the second half of this article we report on an initiative in which we worked with teachers to identify mathematically gifted pupils and to provide effective enrichment support for them, in a number of London Local Authorities. A number of significant issues are raised relating to the identification of mathematical talent, enrichment provision for students and teachersâ professional development
Constraints on gluon evolution at small x
The BFKL and the unified angular-ordered equations are solved to determine
the gluon distribution at small . The impact of kinematic constraints is
investigated. Predictions are made for observables sensitive to the gluon at
small . In particular comparison is made with measurements at the HERA
electron-proton collider of the proton structure function as a
function of , the charm component, and diffractive
photoproduction.Comment: 17 LaTeX pages and 9 postscript figure
Learning to fear a second-order stimulus following vicarious learning
Vicarious fear learning refers to the acquisition of fear via observation of the fearful responses of others. The present study aims to extend current knowledge by exploring whether second-order vicarious fear learning can be demonstrated in children. That is, whether vicariously learnt fear responses for one stimulus can be elicited in a second stimulus associated with that initial stimulus. Results demonstrated that children's (5â11 years) fear responses for marsupials and caterpillars increased when they were seen with fearful faces compared to no faces. Additionally, the results indicated a second-order effect in which fear-related learning occurred for other animals seen together with the fear-paired animal, even though the animals were never observed with fearful faces themselves. Overall, the findings indicate that for children in this age group vicariously learnt fear-related responses for one stimulus can subsequently be observed for a second stimulus without it being experienced in a fear-related vicarious learning event. These findings may help to explain why some individuals do not recall involvement of a traumatic learning episode in the development of their fear of a specific stimulus
A checklist of the hawkmoths (Lepidoptera: Sphingidae) of the Cayman Islands: with implications for the pollination of the ghost orchid \u3ci\u3eDendrophylax fawcettii \u3c/i\u3eRolfe (Orchidaceae: Angraecinae) and consideration of bat predation
This checklist synthesises historic collections of Sphingidae (Lepidoptera) made during the summer months in the Cayman Islands in 1938 and 1975 with modern records drawn from a variety of sources. We report observations and collections made in all seasons of the year and provide natural history and larval food details. Four species, Phryxus caicus (Cramer) in all three islands, plus Isognathus rimosa (Grote), Enyo lugubris (Linnaeus), and Eumorpha satellitia (Linnaeus) in Grand Cayman only, are here reported as new records, for a total of 25 sphingid species occurring in the Cayman Islands. Seven species are new records for Grand Cayman, five are added for Little Cayman and two for Cayman Brac. Potential hawkmoth pollinators for the Cayman Islands endemic ghost orchid, Dendrophylax fawcettii Rolfe (Orchidaceae: Angraecinae) are reviewed and Cayman records of hawkmoths as prey of the big-eared bat Macrotus waterhousii minor Gundlach (Phyllostomidae) are discussed.
The hawkmoths (Lepidoptera: Sphingidae) of the Cayman Islands are the only moths to have received more than passing treatment as a group in the published literature. The catalogue provided by Askew (1994) remains the most recent, and with one exception, is based only on collections made in the early rainy seasons of 1938 and 1975. The results of the Oxford University Biological Expedition to all three Cayman Islands, conducted between April and August 1938, were reported by Jordan (1940), and those of the Royal SocietyâCayman Islands Government Expedition to Little Cayman in JuneâJuly 1975 by Askew (1980). These combined lists, to which Askew (1994) was able to add the 1911 specimen of Pachylia ficus (Linnaeus) from Grand Cayman deposited at the Natural History Museum, London by T.M. Savage English, resulted in a total of twenty-one species of Sphingidae reported from the Cayman Islands as of 1994. Since that time, insect collections have been established at the National Trust for the Cayman Islands, the Department of Environment and the Department of Agriculture. The authors have also made personal collections. Particularly since the advent of digital equipment, photographic images of hawkmoths made by resident and visiting naturalists have provided significant primary records and supplemental data. This checklist synthesises the historic collections and the modern records, reports occurrence for all months of the year, and provides natural history information where available. We assess the larval food plant availability, the affinities and permanence of the sphingid fauna of the islands
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