1,720,971 research outputs found
Nonparametric deconvolution provides an objective assessment of GH responsiveness to GH releasing stimuli in normal subjects
No full textOBJECTIVE: Deconvolution analysis has been proposed as an effective method for analysing the physiology of GH secretion. In the literature, it has been applied to spontaneous secretion data characterized by long and uniform sampling paradigms. In the present study we investigated the applicability of non-parametric deconvolution to the analysis of response- to-stimuli (RTS) data characterized by infrequent and non-uniform sampling. PATIENTS: Thirty-six healthy adult male volunteers (age range 24-37 years) were randomly subdivided into two groups (group I, n = 30; group II, n = 6). DESIGN: Subjects of group I were tested with a single 1/μg/kg body weight GH-releasing hormone (GHRH) bolus, administered at 0 minutes. Subjects of group II were tested, in random order, with a 4- or 5-day interval, with (1) two consecutive 1/μg/kg body weight GHRH boluses at 0 and 120 minutes and (2) two consecutive 1 μg/kg body weight hexarelin boluses, administered at 0 and 120 minutes. MEASUREMENTS: GH levels were determined at 0, 15, 30, 45, 60, 90 and 120 minutes (group I) and -30, 0, 15, 30, 45, 60, 120, 135, 150, 165, 180 and 240 minutes (group II). A numerically efficient regularization- based non-parametric deconvolution algorithm incorporating non-negativity constraints was used to estimate the time profile of the instantaneous secretion rate (ISR). Confidence limits allowing for both measurement error and kinetic model uncertainty were computed using a Monte-Carlo procedure. In order to validate the deconvolution method, a simulated benchmark problem was set up. RESULTS: The analysis of the benchmark problem showed that the proposed method is capable of providing an accurate reconstruction of the ISR (as measured by the root mean square (RMS) error). Moreover, it appeared that reliable confidence limits cannot be obtained unless the kinetic model uncertainty is taken into account. The analysis of the data showed a clear rise in the ISR subsequent to the first bolus (either GHRH or hexarelin), with most of the response occurring within 60 minutes of the stimulus. In group I, it was also seen that discarding the samples collected st times 90 and 120 minutes only marginally affected the estimate of the cumulated ISR over 0-60 minutes (the variation was always less than 3%). The analysis of GH responsiveness to repeated stimuli (group II) showed that the amount of hormone secreted after the second bolus was clearly reduced in comparison with that elicited by the first stimulus, most of the response occurring within 60 minutes of the injection. The amount of GH secreted after the second stimulus ranged from 13 to 36% (GHRH 17-36%; hexarelin 13-36%) of the overall amount of hormone secreted after time 0 minutes. CONCLUSIONS: Even with relatively few samples, non-parametric deconvolution of response-to- stimulus data is capable of providing a reliable, smooth and non-negative estimate of the GH instantaneous secretion rate that offers a realistic representation of the GH secretory dynamics. The non-parametric approach compares favourably with respect to discrete deconvolution methods, that yield discontinuous instantaneous secretion rates profiles, and parametric methods that would require more stringent assumptions on the shape of the instantaneous secretion rate. When assessing confidence limits it is essential to take into account both measurement error and kinetic model uncertainty. Using deconvolution in normal subjects, the estimated instantaneous secretion rate between 0 and 60 minutes is scarcely affected by samples taken after time 60 minutes. Since most of the secretory response takes place during this time interval, there is motivation for investigating the use of shorter sampling protocols in conjunction with deconvolution analysis. Although pulse detection and the assessment of the shape of spontaneous pulses have not been investigated, it could be interesting to apply non-parametric deconvolution to spontaneous secretion data as well
Modificazioni acute della pressione arteriosa e del dispendio energetico durante stimolazione elettrica muscolare
No full textObiettivo. Sebbene l’elettrostimolazione (ES) muscolare sia ampiamente utilizzata a scopo riabilitativo e di allenamento, le risposte acute del sistema cardiorespiratorio all’ES sono poco studiate. Scopo di questo studio è valutare gli adattamenti cardiorespiratori acuti all’ES massimale nei muscoli bicipite brachiale e quadricipite femorale.
Metodi. Tredici soggetti di sesso maschile ben allenati (età 27±3 anni (m±SD); peso 74±6 kg, altezza 178±8 cm) hanno partecipato allo studio. Il bicipite brachiale e il quadricipite femorale (lato dominante) sono stati stimolati elettricamente fino alla massima intensità tollerabile in 2 giorni differenti. Il consumo di ossigeno (V.O2), il quoziente respiratorio (QR), la ventilazione polmonare (VE), la frequenza cardiaca (FC) e la pressione arteriosa sistolica (PAS) e diastolica (PAD) sono stati monitorizzati in continuo: 1) a riposo (10 min prima dell’inizio dell’ES) e 2) durante la sessione di ES (ultimi 5 min della fase allenante).
Risultati. Tutti i parametri metabolici sono significativamente aumentati rispetto alle condizioni basali durante l’ES di entrambi i muscoli (p<0,001), senza differenze tra bicipite e quadricipite. Sia la PAS che la PAD sono risultate significativamente incrementate durante la stimolazione (p<0,001), con un incremento della PAS significativamente maggiore durante la stimolazione del quadricipite, rispetto a quella del bicipite (p<0,05). Non è stata osservata alcuna relazione significativa tra parametri fisiologici e intensità della stimolazione. È stata, invece, verificata una correlazione positiva tra area muscolare della coscia e incremento della PAS.
Conclusioni. Sebbene l’ES sia stata applicata monolateralmente, alla massima intensità tollerabile, la stimolazione elettrica ha attivato significativamente il sistema cardiorespiratorio. L’aumento della pressione arteriosa durante la stimolazione potrebbe dipendere sia dall’area di sezione vascolare del muscolo stimolato che da un aumentato rilascio di catecolamine, ma non appare influenzato dall’entità della stimolazione. Pertanto, durante una seduta di ES, dovrebbero essere considerati gli adattamenti cardiovascolari, specialmente nei soggetti con pressione arteriosa borderline/alta o con elevato rischio cardiovascolare
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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