1,721,073 research outputs found
Objective detection of evoked potentials using a bootstrap technique
No full textEvoked potentials are usually evaluated subjectively, by visual inspection, and considerable differences between interpretations can occur. Objective, automated methods are normally based on calculating one (or more) parameters from the data, but only some of these techniques can provide statistical significance (p-values) for the presence of a response. In this work, we propose a bootstrap technique to provide such p-values, which can be applied to a wide variety of parameters. The bootstrap method is based on randomly resampling (with replacement) the original data and gives an estimate of the probability that the response obtained is due to random variation in the data rather than a physiological response.The method is illustrated using auditory brainstem responses (ABRs) to detecting hearing thresholds. The flexibility of the approach is illustrated, showing how it can be used with different parameters, numbers of stimuli and with user-defined false-positive rates. The bootstrap method provides a new, simple and yet powerful means of detecting evoked potentials, which is very flexible and readily adapted to a wide variety of signal parameters
Objective measures of auditory temporal resolution with ABR
No full textObjective: to develop a reliable objective method to measure temporal resolution thresholds using Auditory Brainstem Response (ABR) with statistical response detection methods.Design: the ABR paradigms “Two Clicks (2C)” and “Temporal Notched Noise with Click (TNNC)” were evaluated for measuring objective temporal resolution thresholds. Statistical methods were used for ABR detection. Test-retest reliability of both ABR paradigms was also assessed. For comparison, a Gaps in Noise test and psychometric TNNC paradigm measured behavioural thresholds from the same subjects.Study sample: 23 normal-hearing participants in the main study, and an additional 10 in the test-retest experiment, aged 20–35 years.Results: objective temporal resolution thresholds averaged 4.04 ms for the 2C paradigm and 3.21 ms for the TNNC paradigm. Group-level data showed reduced ABR amplitude and detection as gap durations approached threshold, whilst individual ABR amplitudes fluctuated across gap durations. Behavioural thresholds averaged 1.49 and 2.22 ms. In the test-retest experiment, TNNC showed moderate repeatability, while 2C had slight, non-significant repeatability (measured by Cohen’s Kappa).Conclusions: while these objective approaches show promise for measuring temporal resolution at a group level, their application in individuals remains challenging due to high variability across subjects. The TNNC paradigm demonstrated better performance in terms of ABR repeatability
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
Sex-specific programming of cardiovascular physiology in children
No full textAims: Increasing evidence suggests that adverse prenatal environments, as indicated by low birth weight, cause long-term changes in cardiovascular physiology that predispose to circulatory disease. The mechanisms are poorly understood, most human studies have been carried out in adults and little is known about early pathophysiological changes. Therefore, we have assessed the relationship between birth weight and cardiovascular physiology in children. Methods and results: In 140 healthy boys and girls (aged 7–9 years), born at term and followed prospectively, we continuously recorded blood pressure, electrocardiograms and cardiac impedance before, during, and after 10 min of psychosocial stress (Trier Social Stress Test for Children). In boys, an association of lower birth weight with higher resting systemic arterial pressure (? = –6.8 mmHg/kg, P= 0.03) and a trend towards higher vascular resistance (? = –87 dyne s/cm5/kg, ns) were substantially strengthened following stress (? = –9.5 mmHg/kg, P= 0.003 and ? = –139 dyne s/cm5/kg, P = 0.02, respectively). In girls, lower birth weight was associated with a shorter pre-ejection period (? = 8.0 ms/kg, P = 0.005) and corrected QT interval (? = 11.9 ms/kg, P = 0.003) at rest and little changed by stress. Conclusion: Smaller size at birth is associated with sex-specific alterations in cardiac physiology; boys had higher systemic vascular resistance and girls had increased cardiac sympathetic activation
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