1,721,388 research outputs found
Validation of a continuous-wave, single-distance NIRS oxymeter for the determination of muscle oxygenation during cycling.
No full textValidation of a continuous-wave, single-distance NIRS oxymeter for the determination of muscle oxygenation during cycling.
Silvia Pogliaghi1, Lorenzo Casiello1, Andrea Bandera2
1 Faculty of Kinesiology, University of Verona, Italy; 2 Nirox srl, Brescia, Italy
An Italian company recently developed a relatively inexpensive continuous-wave (CW), single-distance near-infrared spectroscopy (NIRS) oxymeter that allows the calculation of absolute values of deoxygenated haemoglobin (deoxyHb). This absolute quantification is made possible by an in-vivo estimate of the scattering coefficient (based on direct measures of the scattering at the water absorption peak and on its linear extrapolation to the near-infrared range). The calculated scattering coefficient is assumed not to change over the time of the experiment. PURPOSE: We tested the possible correspondence between non-invasive measures of muscle deoxyHb obtained using this CW device and a frequency-domain (FD) multi-distance NIRS system, used as a reference method. METHODS: 11 healthy sedentary males (27±5 years, 176±1 cm , 73±8 kg, 54±4 ml*kg-1*min-1 VO2max) performed an incremental cycling test. Following a 3-min rest, subjects pedaled at 50 watt for 3 min. Thereafter, the workload was increased stepwise, 20 watt per minute, up to voluntary exhaustion. During the tests, muscle deoxyHb was monitored continuously on the vastus lateralis of the right leg, using the reference FD device (FDdeoxyHb), and on the right leg, using the CW instrument (CWdeoxyHb). The average values of the last 30s of rest and warm-up cycling, and the last 10 s of each stage were used for statistical analysis. Agreement between the two instruments was tested by Bland Altman analysis (significance ≤0.05). RESULTS: Resting CWdeoxyHb and FDdeoxyHb were 27±6 and 29±5 mmol*l-1 respectively (not different). As expected, deoxyHb increased as a function of exercise intensity reaching 43±9 (CWdeoxyHb) and 44±10 mmol*l-1 (FDdeoxyHb) upon exhaustion (not different). At all exercise intensities, CWdeoxyHb was not significantly different from FDdeoxyHb (bias 0.93, not different from 0; precision 7.6 mmol*l-1).
CONCLUSIONS: The main finding of this study is that there is a very good agreement between muscle deoxyHb values measured by the evaluated CW device and the reference FD oxymeter. Compared to the reference device, the new, relatively inexpensive oxymeter yields unbiased and precise deoxyHb values during incremental cycling exercises in healthy sedentary males.
The study was supported by Nirox srl, Ital
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
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
A NOVEL TISSUE OXYMETER COMBINING THE MULTIDISTANCE APPROACH WITH AN ACCURATE SPECTRAL ANALYSIS
No full textIn this paper a novel optical tissue oxymeter thatintegrates the multidistance approach and the evaluation of thedifferential pathlength qloiting the absorption features of waferis presented This system tukes advantage from the peculiarities ofthese techniques to extract the scatterirrg and the absorptioncoeficient reducing errors introduced by the heterogeneousstructure of the tissue and improving the signal-to-noise ratio
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Design and performance of a wide-bandwidth and sensitive instrument for near-infrared spectroscopic measurements on human tissue
No full textThe article describes an instrument designed to perform in vivo near-infrared spectroscopic measurements on human tissues. The system integrates five continuous-wave laser diode sources emitting in the near-infrared spectral region and a low-noise detection system based on an avalanche photodiode. The optical probe is based on a compact, reliable, and low-cost fiber based system with four quantitative measuring points. The excellent sensitivity of the instrument allows one to perform quantitative assessments of the hemoglobin concentration exploiting precise absorption measurements close to the absorption peak of the water: 975 nm. Moreover, a good signal to noise ratio is obtained also at a high acquisition rate, allowing us to follow rapid changes in oxidative metabolism. The system bandwidth is selectable within the range 2.3-27 Hz, i.e., 20 channels (five chromatic and four spatial channels) can be acquired 27 times for each measuring second, whereas the system amplification can be set to measure optical density ranging from 3.5 to 8.5. A prototype version of the instrument has been realized and characterized
Non-invasive in vivo infrared laser spectroscopy to analyse endogenous oxy-haemoglobin, deoxy-haemoglobin, and blood volume in the rat CNS
No full textOxy-haemoglobin (HbO2) and deoxy-haemoglobin (Hb) are chromophores present in biological tissues. Near infrared spectroscopy (NIRS) is a non-invasive methodology based on the low extinction coefficient of tissue in the near infrared region. NIRS can be used to measure changes in the concentration of these chromophores, i.e., haemoglobin, in muscular tissue. In the present work, NIRS has been used for the non-invasive monitoring of HhO2, Hb, and blood volume (V: representing total haemoglobin, i.e., HhO2 + Hb) in vivo in the whole rat brain. This has been performed by means of prototype instrumentation based on optic fibre probes placed in contact with the head of anaesthetised rats held in a stereotaxic frame. A preliminary test of the instrument has been performed on human muscle, i.e., lateral gastrocnemius, in order to evaluate the ability of the instrument to detect oxygenation changes. Afterwards, the effects of pharmacological treatments, such as sytemic amphetamine and nicotine treatments on the CNS have been detected
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