1,721,171 research outputs found
The effects of fetal breathing movements on the utero-fetal-placental circulation.
No full textImportant factors which may affect the fetal circulation are the fetal breathing movements (FBMs) and other movements adn the features of fetal circulation. Recent studies have demonstrated that FBMs are a normal phenomenon of intrauterine development and that there are two patterns of FBMs: (1) A predominant pattern of rapid, irregular (in rate and amplitude) episodic movements, with interspersed episodes of apnea that is present more than 50 percent of the time and accounts for more than 90 percent of the breathing activity. Interestingly, periodic sighs are often seen during these FBMs; (2) There is also a less frequent pattern of sporadic, slow (1 to 4 movements/min), deep inspiratory movements, like sighs or gasps, or espiratory efforts which resemble grunting, coughing, or panting. The first pattern, which represents normal fetal respiratory activity, only occurs during rapid eye movements (REM) sleep, and it is unrelated to changes in blood gases and pH values and to afferent impulses from aortic and carotid bodies; FBMs may produce intrathoracic pressure swings of 35 Torr or more and are independent of Hering-Breuer reflexes. This pattern is usually accompanied by increased FHR beat-to-beat variability and increased systolic and diastolic blood pressure and flow (BF). Therefore, they may influence the velocimetry of B.F. in humans, e.g., RED and ARED in the umbilical artery blood flow (UABF), which do not necessarily indicate impending fetal demise. The second pattern is unrelated to the fetal behavioral state and blood gas tensions. Concerning the effects of drugs on FBMs, we have analysed the effects aminophylline (A)(bolus of 240 mg followed by 0.2 mg/kg/min) given to women not in labor; A caused a prompt and sustained FBMs that started as vorteces and then as regular inspiratory and expiratory movements, which increased in frequency (up to 88/min) and depth. Hexoprenaline given to pregnant women with threatened preterm labor were able to elicit FBMs and NFFV; the infusion of 0.3 microg/min increased UABF. Conjugated estrogens administered to the mother as a 10 mg bolus enhanced FBMs, as documented by TM and nasal flow velocity waveforms (NFFV); this was associated with an increased UABF; betamethasone (4 mg bolus to the mother) was shown to induce FBMs and an increased UABF. In a twin pregnancy betamethasone (0.5 mg/kg) was administered IV into the umbilical vein in one fetus and IM to the other; in both cases bradycardia and increase in UABF occurred, immediately after IV infusion, and after 30 min following IM injection FBMs were induced or enhanced in frequency and depth. The flow in MCA was unchanged. In conclusion, the fetal circulation is influenced by fetal behavioural states, particularly by FBMs that affect the fetal cardiovascular function, including blood pressure and FHR thereby conditioning the velocimetric response of its major vessels, i.e., UA and MCA BF, whose alterations do not necessarily reflect impending fetal demise
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
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