1,721,088 research outputs found
Oxygen uptake kinetics: why are they so slow? And what do they tell us?
No full textV̇O2 kinetics and O2 deficit are important determinants of exercise tolerance. In "normal" conditions convective and diffusive O2 delivery to skeletal muscle fibers do not represent important determinants of V̇O2 kinetics, whose limiting factors seem mainly located within muscle fibers. Whereas a limiting role by PDH has not been confirmed, the role of inhibition of mitochondrial respiration by NO needs further investigations. Important determinants of skeletal muscle V̇O 2 kinetics likely reside in the interplay between bioenergetic mechanisms at exercise onset. By acting as high-capacitance energy buffers, PCr hydrolysis and anaerobic glycolysis would delay or attenuate the increase in [ADP] within muscle fibers following rapid increases in ATP demand, preventing a more rapid activation of oxidative phosphorylation. The different "localization" of the main limiting factors for V̇O2 kinetics and V̇O2max offers the opportunity to perform a functional evaluation of oxidative metabolism at two different levels of the pathway for O2, from ambient air to mitochondria. Whereas V̇O2max is mainly limited by the capacity of the cardiovascular system to deliver O2 to exercising muscles, by analysis of V̇O2 kinetics the functional evaluation is mainly related to skeletal muscle. In pathological conditions the situation may be less clear, and warrants further investigations
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
A physical mechanism of the atmospheric response over Antarctica to decadal trends in tropical SST
No full textThe atmospheric response to the tendency of oceanic
equatorial temperature observed during recent decades has been simulated, leading to the identification of a possible link between tropical Sea Surface Temperature (SST) and Antarctic climate change. The dynamical mechanism, by which changes in tropical SSTs exert an influence on the upper latitude atmospheric dynamics, is investigated. The analysis of the simulations suggests that the perturbations of the atmospheric circulation are induced by changes in the annual cycle of the tropical convective activity, which influences the intensity of
the wave forcing. In particular, the introduction of the SST perturbation generates a strong vertical wind shear at middle latitude during the Antarctic winter affecting the propagation
of convectively generated waves during the following spring
Simulation of Polar Antarctic trends: influence of tropical SST
No full textThe polar Antarctic atmosphere has been recently characterized by a progressive intensification of the circumpolar westerly winds, both in the stratospheric and tropospheric component. We simulate the response of the polar southern hemisphere atmosphere to a prescribed trend of oceanic equatorial temperature to demonstrate a possible link between the progressive warming of tropical sea surface temperature (SST) and Antarctic climate changes in the last decades. Model simulations produce an atmospheric response suggesting an influence of equatorial SST on polar dynamics, particularly during summer months
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Assimilation of stratospheric ozone in the chemical transport model STRATAQ
No full textWe describe a sequential assimilation approach
useful for assimilating tracer measurements into a three-
dimensional chemical transport model (CTM) of the strato-
sphere. The numerical code, developed largely according
to Khattatov et al. (2000), uses parameterizations and sim-
plifications allowing assimilation of sparse observations and
the simultaneous evaluation of analysis errors, with reason-
able computational requirements. Assimilation parameters
are set by using χ 2 and OmF (Observation minus Forecast)
statistics. The CTM used here is a high resolution three-
dimensional model. It includes a detailed chemical pack-
age and is driven by UKMO (United Kingdom Meteorolog-
ical Office) analyses. We illustrate the method using assim-
ilation of Upper Atmosphere Research Satellite/Microwave
Limb Sounder (UARS/MLS) ozone observations for three
weeks during the 1996 antarctic spring. The comparison
of results from the simulations with TOMS (Total Ozone
Mapping Spectrometer) measurements shows improved total
ozone fields due to assimilation of MLS observations. More-
over, the assimilation gives indications on a possible model
weakness in reproducing polar ozone values during spring-
time
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