8 research outputs found
BFKL versus HERA
The BFKL equation and the kT-factorization theorem are used to obtain
predictions for F2 in the small Bjorken-x region over a wide range of Q**2. The
dependence on the parameters, especially on those concerning the infrared
region, is discussed. After a background fit to recent experimental data
obtained at HERA and at Fermilab (E665 experiment), we find that the predicted,
almost Q**2 independent BFKL slope lambda >= 0.5 appears to be too steep at
lower Q**2 values. Thus there seems to be a chance that future HERA data can
distinguish between pure BFKL and conventional field theoretic renormalization
group approaches.Comment: 26 pages, 6 eps figures, LaTeX2e using epsfig.sty and amssymb.st
What can whiskers tell us about mammalian evolution, behaviour, and ecology?
Most mammals have whiskers; however, nearly everything we know about whiskers derives from just a handful of species, including laboratory rats Rattus norvegicus and mice Mus musculus, as well as some species of pinniped and marsupial. We explore the extent to which the knowledge of the whisker system from a handful of species applies to mammals generally. This will help us understand whisker evolution and function, in order to gain more insights into mammalian behaviour and ecology. This review is structured around Tinbergen’s four questions, since this method is an established, comprehensive, and logical approach to studying behaviour. We ask: how do whiskers work, develop, and evolve? And what are they for? While whiskers are all slender, curved, tapered, keratinised hairs that transmit vibrotactile information, we show that there are marked differences between species with respect to whisker arrangement, numbers, length, musculature, development, and growth cycles. The conservation of form and a common muscle architecture in mammals suggests that early mammals had whiskers. Whiskers may have been functional even in therapsids. However, certain extant mammalian species are equipped with especially long and sensitive whiskers, in particular nocturnal, arboreal species, and aquatic species, which live in complex environments and hunt moving prey. Knowledge of whiskers and whisker use can guide us in developing conservation protocols and designing enriched enclosures for captive mammals. We suggest that further comparative studies, embracing a wider variety of mammalian species, are required before one can make large-scale predictions relating to evolution and function of whiskers. More research is needed to develop robust techniques to enhance the welfare and conservation of mammals
The Gluon density of the proton at low x from a QCD analysis of F2
We present a QCD analysis of the proton structure function measured by
the H1 experiment at HERA, combined with data from previous fixed target
experiments. The gluon density is extracted from the scaling violations of
in the range and compared with an
approximate solution of the QCD evolution equations. The gluon density is found
to rise steeply with decreasing .Comment: 17 pages, latex2e, 5 figures appended as uuencoded file, hep number
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