1,721,072 research outputs found
Equivalence of information from single frequency v. bioimpedance spectroscopy in bodybuilders
No full textBr J Nutr. 2007 Jan;97(1):182-92.
Equivalence of information from single frequency v. bioimpedance spectroscopy in bodybuilders.
Piccoli A, Pastori G, Codognotto M, Paoli A.
Source
Department of Medical and Surgical Sciences, University of Padova, Italy. [email protected]
Abstract
In bioelectrical impedance spectroscopy (BIS), it is assumed that the current path is only extracellular at the lowest frequencies and that it is both extra- and intracellular at the highest frequencies. We tested validity of BIS assumptions in bodybuilders who have an increased intracellular volume due to hypertrophy of muscle fibres. The study was observational cross-sectional in a study group of thirty professional bodybuilders compared with thirty control subjects. Resistance (R) and reactance (Xc) vector components fitting the Cole's arc with BIS (SFB3 analyser) were compared with components at 50 kHz frequency. The average Cole's arc in bodybuilders was significantly smaller and shifted to the left in the R-Xc plane (both R and Xc values were smaller at any individual frequency). The ratio of Xc at 5 kHz and Xc at the characteristic frequency was 70% in bodybuilders and 64% in control subjects, indicating a huge intracellular flow of the electric current at low frequencies in both groups (expected ratio close to 0 if the current path was extracellular). As a consequence of a common path, the correlation coefficient between R values at 50 kHz and at other frequencies (from 0 to infinity) was 0.94 to 1.00. The correlation between total body water estimated with BIS or with R at 50 kHz was 0.98. Hence, there was equivalence between information provided by the vector components R and Xc at 50 kHz and that provided by 496 correlated vectors that were measured with BIS
Qualche spunto di riflessione. Gli Stati Uniti e il mondo. Le dinamiche di un rapporto complesso
No full textIl contributo analizza sinteticamente le complessità del rapporto transatlantico e il modo in cui queste si sono espresse storicamente, evidenziandone i tratti di continuità e ipotizzando possibili linee evolutive, alla luce di quelle che sono le trasformazioni in corso nell'attuale sistema internazionale
Alla ricerca di un posto nel mondo. La politica estera degli Stati Uniti dalla nascita della Federazione alle fine della Guerra fredda
No full textIl contributo analizza sinteticamente lo sviluppo della politica estera statunitense dalla nascita della Federazione alla fine della guerra fredda, evidenziandone le logiche di fondo e i principali punti di continuità e rottura
Le sfide del cambiamento. La fine della Guerra fredda e le trasformazioni della politica estera statunitense
No full textIl contributo analizza sinteticamente l'evoluzione della politica estera statunitense dopo la fine della guerra fredda, evidenziando i principali punti di continuità e rottura rispetto al periodo precedente e mettendo in luce come l'evoluzione dello scenario internazionale influenzi il riposizionamento del paese rispetto al ruolo tradizionalmente assunto
Gli Stati Uniti e la Russia, un vecchio nemico per un nuovo mondo?
No full textIl saggio ripercorre l'evoluzione delle relazioni tra Stati Uniti e Russia dopo la fine della Guerra Fredda, tenendo in considerazione il ruolo della Cina
Stati Uniti ed Europa, l’evoluzione dell’Alleanza Atlantica
No full textIl saggio ripercorre l'evoluzione dell'alleanza tra Stati Uniti ed Europa dagli anni della Guerra Fredda alle sfide e minacce del Ventunesimo secolo
Equivalence of information from single versus multiple frequency bioimpedance vector analysis in hemodialysis
No full textKidney Int. 2005 Jan;67(1):301-13.
Equivalence of information from single versus multiple frequency bioimpedance vector analysis in hemodialysis.
Piccoli A, Pastori G, Guizzo M, Rebeschini M, Naso A, Cascone C.
Source
Department Scienze Mediche e Chirurgiche, University of Padova, Padova, Italy. [email protected]
Abstract
BACKGROUND:
In suspended cells, low-frequency current only passes through extracellular fluids, while current at higher frequencies passes through extra- and intracellular fluids. Cells in soft tissues are in contact with each other, which causes tissue anisotropy, meaning that impedance changes along different cell directions, with part of low-frequency current also passing through cells. Hence, equivalent information on body impedance change is expected at all frequencies, which we proved in a dynamic condition of fluid removal with hemodialysis.
METHODS:
We performed whole-body impedance spectroscopy (496 frequencies from 4 to 1024 kHz, SEAC SFB3 analyzer; Brisbane, Australia) before and during fluid removal (0, 60, 120, 180 min, 2.5 kg) in 67 hemodialysis patients. With increasing current frequency, resistance (R) decreases and reactance (Xc) moves along the Cole's semicircle on the R-Xc plane.
RESULTS:
The Cole's semicircles progressively enlarged and moved to the right on the R-Xc plane following fluid removal (increase in both R and Xc values at any given frequency). Xc values at 5 kHz (expected values close to 0 Ohm) were 70% of the maximun Xc, indicating an intracellular current flows at low frequencies. The correlation coefficient between R at 50 kHz (standard frequency) and R at other frequencies ranged from 0.96 to 0.99, and the correlation coefficient between Xc at 50 kHz and Xc at other frequencies at any time point ranged from 0.65 to 0.99.
CONCLUSION:
From high Xc values at low frequency, tissue anisotropy is inferred. Intra- and extracellular current flow causes equivalence of information based on functions of R and Xc measurements made at 50 kHz versus other frequencies
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
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