2,672 research outputs found
On the boundedness of asymptotic stability regions for the stochastic theta method
The stochastic theta method gives a computational procedure for simulating ordinary stochastic differential equations. The method involves a free parameter, THgr. Here, we characterise the precise value of THgr beyond which the region of linear asymptotic stability of the method becomes unbounded. The cutoff point is seen to differ from that in the deterministic case. Computations that suggest further results are also given
The re-dating of some Scottish specimens by the Oxford Radiocarbon Accelerator Unit (ORAU)
The purpose of this note is to alert readers to the fact that some AMS dates determined by ORAU on Scottish material between 2000 and 2002 have had to be deleted and re-determined, because of a problem in the ultrafiltration system used to pretreat bone samples during that period (see C Bronk Ramsey, T Higham, A Bales and R Hedges 2004, Improvements in the pretreatment of bone at Oxford, Radiocarbon 46(1), 155–63, for details). In many cases it has been possible to undertake the re-dating using left over material from the original (unprocessed) samples; in other cases, re-sampling will be necessary. Lists of both sets of material are appended here, and readers are requested to use only the new dates, and to delete the old versions
The re-dating of some Scottish specimens by the Oxford Radiocarbon Accelerator Unit (ORAU): results received during 2007
Ex-ante measure of patent quality reveals intrinsic fitness for citation-network growth
We have constructed a fitness parameter, characterizing the intrinsic
attractiveness for patents to be cited, from attributes of the associated
inventions known at the time a patent is granted. This exogenously obtained
fitness is shown to determine the temporal growth of the citation network in
conjunction with mechanisms of preferential attachment and obsolescence-induced
ageing that operate without reference to characteristics of individual patents.
Our study opens a window on understanding quantitatively the interplay of the
rich-gets-richer and fit-gets-richer paradigms that have been suggested to
govern the growth dynamics of real-world complex networks.Comment: 6 pages, 3 figures, RevTex4.1, v2: minor changes, version to appear
as a Rapid Communication in Phys. Rev.
Unraveling the dynamics of growth, aging and inflation for citations to scientific articles from specific research fields
We analyze the time evolution of citations acquired by articles from journals
of the American Physical Society (PRA, PRB, PRC, PRD, PRE and PRL). The
observed change over time in the number of papers published in each journal is
considered an exogenously caused variation in citability that is accounted for
by a normalization. The appropriately inflation-adjusted citation rates are
found to be separable into a preferential-attachment-type growth kernel and a
purely obsolescence-related (i.e., monotonously decreasing as a function of
time since publication) aging function. Variations in the empirically extracted
parameters of the growth kernels and aging functions associated with different
journals point to research-field-specific characteristics of citation intensity
and knowledge flow. Comparison with analogous results for the citation dynamics
of technology-disaggregated cohorts of patents provides deeper insight into the
basic principles of information propagation as indicated by citing behavior.Comment: 13 pages, 6 figures, Elsevier style, v2: revised version to appear in
J. Informetric
Characterization of the bubble cluster and velocity field in the focal region of a lithotripter
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Fatigue Alters in Vivo Function Within and Between Limb Muscles During Locomotion
Muscle fatigue, a reduction in force as a consequence of exercise, is an important factor for any animal that moves, and can result from both peripheral and/or central mechanisms. Although much is known about whole-limb force generation and activation patterns in fatigued muscles under sustained isometric contractions, little is known about the in vivo dynamics of limb muscle function in relation to whole-body fatigue. Here we show that limb kinematics and contractile function in the lateral (LG) and medial (MG) gastrocnemius of helmeted guineafowl (Numida meleagris) are significantly altered following fatiguing exercise at 2 m sK1 on an inclined treadmill. The two most significant findings were that the variation in muscle force generation, measured directly from the muscles’ tendons, increased significantly with fatigue, and fascicle shortening in the proximal MG, but not the distal MG, decreased significantly with fatigue. We suggest that the former is a potential mechanism for decreased stability associated with fatigue. The region-specific alteration of fascicle behaviour within the MG as a result of fatigue suggests a complex response to fatigue that probably depends on muscle–aponeurosis and tendon architecture not previously explored. These findings highlight the importance of studying the integrative in vivo dynamics of muscle function in response to fatigue.Organismic and Evolutionary Biolog
Radiocarbon dates from the Oxford AMS system: archaeometry datelist 35
This is the 35th list of AMS radiocarbon determinations measured at the Oxford Radiocarbon Accelerator Unit (ORAU). Amongst some of the sites included here are the latest series of determinations from the key sites of Abydos, El Mirón, Ban Chiang, Grotte de Pigeons (Taforalt), Alepotrypa and Oberkassel, as well as others dating to the Palaeolithic, Mesolithic and later periods. Comments on the significance of the results are provided by the submitters of the material
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