1,720,991 research outputs found
Pathophysiological role of heart rate: from ischaemia to left ventricular dysfunction
No full textMyocardial ischaemia results from imbalance between myocardial oxygen demand and
supply. An increase in heart rate (HR) will raise both demand and supply. HR is the
most important determinant of myocardial oxygen consumption and of cardiac
energy demand. HR reduction improves myocardial perfusion by increasing the fraction
of the cardiac cycle occupied by diastole, which accounts for 80% of coronary
flow. Besides these physiological characteristics, HR is also linked to the progression
of atherosclerosis, at least in animals, and an increase in HR is associated with
plaque rupture in humans. The symptom of chest pain in stable angina is almost
always triggered by elevated HR owing to physical or emotional stress. Equally, an
increased HR precedes an episode of asymptomatic or silent myocardial ischaemia.
Therefore, it is not surprising that the efficacy of some anti-anginal drugs such as
b-blockers and non-dihydropyridine calcium antagonists has been related to their
effectiveness in reducing HR. In many studies, multivariate analysis has shown HR
to be an independent predictor of mortality and of hospitalization for heart failure.
A relationship has been found between HR reduction and mortality in patients with
congestive heart failure treated with b-blockers. Thus HR is an important therapeutic
target for ischaemia and left ventricular dysfunction or congestive heart failure, and it
seems likely that relatively high HR is both causative and indicative of important
pathophysiological processes: HR is a risk factor for cardiovascular morbidity and
mortality throughout the cardiovascular continuu
Induction of hormesis in plants by urban trace metal pollution
Full text linkHormesis is a dose–response phenomenon observed in numerous living organisms, caused by low levels of a large number of stressors, among which metal ions. In cities, metal levels are usually below toxicity limits for most plant species, however, it is of primary importance to understand whether urban metal pollution can threaten plant survival, or, conversely, be beneficial by triggering hormesis. The effects of Cd, Cr and Pb urban concentrations were tested in hydroponics on three annual plants, Cardamine hirsuta L., Poa annua L. and Stellaria media (L.) Vill., commonly growing in cities. Results highlighted for the first time that average urban trace metal concentrations do not hinder plant growth but cause instead hormesis, leading to a considerable increase in plant performance (e.g., two to five-fold higher shoot biomass with Cd and Cr). The present findings, show that city habitats are more suitable for plants than previously assumed, and that what is generally considered to be detrimental to plants, such as trace metals, could instead be exactly the plus factor allowing urban plants to thrive
Bradykinin and coronary artery disease
No full textAlthough the benefits of angiotensin-converting enzyme (ACE) inhibitors in limiting the progression of a variety of cardiovascular diseases are well known, their mechanisms of action have not been completely discovered. A reduction in the synthesis of the potent vasoconstricting agent angiotensin II has for a long time been considered to be the leading mechanism to account for the effects of ACE inhibitors. However, another action of these relatively old drugs is emerging: the increased availability of bradykinin. This kinin, which is broken down by ACE, has potent cardioprotective, antithrombotic antitrophic and vasodilator effects occurring through the stimulation of specific receptors on several cells. The recent development of a specific bradykinin-receptor blocking agent, icatibant, has allowed better understanding of the therapeutic properties of ACE inhibitors mediated by bradykinin both in experimental and clinical studies
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
Characterization of Italian honeys: integrating volatile and physico-chemical data
No full textThis article focuses on the comprehensive characterization of Italian honeys using various physicochemical analyses and their volatile organic compounds (VOCs) fingerprint obtained through the PTRToFMS technology. Honey characteristics, including pH, electrical conductivity, moisture content, hydroxymethylfurfural (HMF), and sugar content, were analyzed to assess their quality and origin. Honey samples from different flowers, including acacia, chestnut, citrus, linden, and multifloral, were collected and investigated. Furthermore, a few aged honeys were collected and analyzed and compared with the fresh ones. Physicochemical analysis revealed that chestnut honey is characterized by high pH and EC values. Acacia honey has a higher fructose content, while aging appears to influence HMF levels, a vital indicator of honey quality, with aged samples exhibiting significant increases in HMF content. The VOC profiles have been found to vary among different honey types, suggesting that VOCs could be used as indicators of honey origin. Multivariate statistical analyses, such as partial least squares discriminant analysis (PLSDA), have been applied to the VOCs data to differentiate honey types based on their volatile profiles. Acacia honey exhibited different physicochemical parameters but on the contrary, in the VOCs analysis, it displayed similarities with the linden honey due to their shared low emissions of volatile compounds. Citrus honey had similar chemical parameters to linden and multifloral honeys, but its distinctive VOCs emission allowed for a more accurate identification. In conclusion, the analysis performed with the PTRToFMS was successful in obtaining specific volatile fingerprints of those samples and was effective for improving the characterization of honeys
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