1,721,191 research outputs found
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
Low hemoglobin increases risk for cerebrovascular disease, kidney disease, pulmonary vasculopathy, and mortality in sickle cell disease: A systematic literature review and meta-analysis
Full text linkSickle cell disease (SCD) is characterized by deoxygenation–induced polymerization of hemoglobin in red blood cells, leading to hemolytic anemia, vaso–occlusion, and the development of multiple clinical complications. To characterize the clinical burden associated with differences in hemoglobin concentration and hemolysis measures, a systematic literature review of MEDLINE, EMBASE, and related meta–analyses was undertaken. For quantitative analyses related to hemoglobin concentration, pooled results were analyzed using random effects models to control for within–and between–study variability. To derive risk ratios associated with hemoglobin concentration change, we combined ratios of means from select studies, which reported hazard and odds ratios in meta–analyses for hemoglobin concentration–related outcomes and changes between groups. Forty-one studies were identified for inclusion based on relating hemoglobin concentration to clinical outcomes. Meta–analyses demonstrated that mean hemoglobin concentration was significantly lower in patients with cerebrovascular disease (0.4 g/dL), increased transcranial Doppler velocity in cerebral arteries (0.6 g/dL), albuminuria (0.6 g/dL), elevated estimated pulmonary artery systolic pressure (0.9 g/dL), and in patients that subsequently died (0.6 g/dL). In a risk reduction meta–analysis, modeled increased hemoglobin concentrations of 1 g/dL or greater resulted in decreased risk of negative clinical outcomes of 41% to 64%. In conclusion, chronic anemia is associated with worse clinical outcomes in individuals with SCD and even modest increases in hemoglobin concentration may be beneficial in this patient population. This systematic review has been registered on Prospero (Registration number CRD42018096860; https://www.crd.york.ac.uk/prospero/).</div
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
Effects of chronic exposure to hypoxia on blood rheology : a study of a chronic intermittent hypoxia to intermittent hypoxia in patients with haemoglobin with haemoglobin pathology (DREPAPNEE study) and DREPAPNEE study) and a chronic exposure model to hypoxia in healthy subjects (Expedition 5300)
No full textL’hypoxie définit une circonstance au cours de laquelle la biodisponibilité en dioxygène dans un environnement donné est abaissée. Elle va être responsable de réponses physiologiques qui sont la plupart du temps bénéfiques. Nous avons choisi d’étudier deux modèles d’expositions à l’hypoxie : l’hypoxie d’altitude et l’hypoxie engendrée par le syndrome d’apnées obstructives du sommeil (SAOS). L’altitude est responsable d’une hypoxie que l’on qualifie d’hypobarique, c’est-à-dire qu’elle est liée à la baisse de la pression barométrique induite par la montée en altitude. Le SAOS est responsable d’épisodes de collapsus pharyngés répétés au cours de la nuit conduisant à une interruption du débit d’air en direction des poumons. Cette interruption du débit ventilatoire est responsable d’une hypoxémie intermittente. Ces deux modèles hypoxiques vont être testés sur des populations différentes : une population de sujets sains représentés par les habitants de La Rinconada (plus haute ville du monde, 5100m, Pérou) et une population de malades atteints de la drépanocytose. Le mal chronique des montagnes (CMS) est une pathologie touchant 14% des habitants de La Rinconada, caractérisée par une perte de l’acclimatation ventilatoire qui conduit à une polyglobulie. La drépanocytose est la première maladie génétique en France et dans le monde. Elle se caractérise par la production d’une hémoglobine anormale, l’hémoglobine S (HbS) qui a la caractéristique de polymériser en situation désoxygénée. Cette polymérisation est responsable de la falciformation des globules rouges à l’origine des mécanismes physiopathologiques de la maladie. Nos deux modèles se caractérisent par des perturbations rhéologiques : la polyglobulie d’altitude s’accompagne fréquemment d’une augmentation de la viscosité sanguine et les patients drépanocytaires présentent des modifications de la viscosité sanguine et de la déformabilité érythrocytaire. Le premier objectif de notre travail de thèse était d’évaluer l’effet de l’hypoxie d’altitude sur la viscosité sanguine chez les habitants de la plus haute ville du monde et d’évaluer son retentissement sur la présence ou non d’un CMS. Le second objectif était d’évaluer la fonction respiratoire des patients drépanocytaires. Le troisième objectif était d’évaluer l’effet du SAOS et de l’hypoxémie nocturne sur la sévérité de la maladie drépanocytaire et sur le profil hématologique et hémorhéologique. [...]Hypoxia is defined as a circumstance in which the bioavailability of oxygen in a given environment is decreased. It is accompanied by physiological responses which are most of the time beneficial. We studied two models of exposure to hypoxia: altitude hypoxia and hypoxia caused by obstructive sleep apnea syndrome (OSAS). The altitude is responsible for hypobaric hypoxia caused by the drop in barometric pressure induced by the rise in altitude. OSA is responsible for repeated episodes of pharyngeal collapse throughout the night leading to an interruption in air flow to the lungs. This interruption of ventilatory flow is responsible for intermittent hypoxemia. These two hypoxic models have been tested on different populations: a population of healthy subjects living permanently in La Rinconada (the highest city in the world, 5100m, Peru) and a population of patients with sickle cell disease. Chronic mountain sickness (CMS) is a disease affecting 14% of the inhabitants of La Rinconada characterized by a loss of ventilatory acclimatization which leads to polycythemia. Sickle cell disease is the first genetic disease in France and around the world. It is characterized by the production of an abnormal hemoglobin, hemoglobin S (HbS), which has the characteristic to polymerize when deoxygenated. This polymerization is responsible for the sickling of red blood cells, which is the main cause of the pathophysiological mechanisms of the disease. Our two models are characterized by rheological disturbances: polycythemia of altitude is accompanied by an increase in blood viscosity, and sickle cell patients have altered blood rheology. The first objective of this thesis was to evaluate the effect of altitude hypoxia on blood viscosity in the inhabitants of the highest city in the world and to evaluate its impact on the presence or not of CMS. The second objective was to assess the respiratory function of sickle cell patients. The third objective was to assess the effect of OSA and nocturnal hypoxemia on the severity of sickle cell disease and on the hematologic and hemorheologic profiles. [...
Centrifugation-induced release of ATP from red blood cells
Full text linkCentrifugation is the primary preparation step for isolating red blood cells (RBCs) from whole blood, including for use in studies focused on transduction of adenosine triphosphate (ATP), an important vasodilatory signaling molecule. Despite the wide use of centrifugation, little work has focused on how the centrifugation itself affects release of ATP from RBCs prior to subsequent experimentation. Here we report that both the centrifugation force and duration have a pronounced impact on the concentration of ATP present in the packed RBCs following centrifugation. Multiple subsequent centrifugations yield extracellular ATP concentrations comparable to the amount released during the initial centrifugation, suggesting this effect is cumulative. Pairwise measurements of hemoglobin and ATP suggest the presence of ATP is primarily due to an increase in centrifugation-induced hemolysis. These results indicate that common centrifugation parameters, within the ranges explored here, can release ATP in quantities comparable to the low end of the range of values measured in typical ATP transduction experiments, potentially complicating experimental interpretation of those results.</div
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
Blood rheology microcirculation tissue oxygenation and hypoxemia at rest and during exercise in sickle cell patients
No full textLa drépanocytose est une hémoglobinopathie aux formes et aux sévérités cliniques très hétérogènes qui affectent de nombreux organes chez les patients touchés. Pour cette raison le terme de syndrome drépanocytaire majeur est généralement employé. Tous les syndromes drépanocytaires majeurs ont en commun une mutation ponctuelle du gène β-globine appelée mutation βs . Cette mutation βs conduit à la synthèse de la protéine d'hémoglobine S (HbS) caractérisée par sa capacité à polymériser dans sa forme désoxygénée. La polymérisation de l'HbS est l'élément déclencheur de la falciformation du globule rouge et conduit à de nombreuses altérations hématologiques et hémorhéologiques. Ces dernières sont à l'origine de troubles de l'hémodynamique, de l'oxygénation sanguine et de la perfusion tissulaire en oxygène. Il en résulte de nombreuses complications aigues (crise vaso-occlusive, accident vasculaire cérébral, syndrome thoracique aigu etc.) et/ou chroniques (glomérulopathie, ostéonécrose de la tête fémorale etc.) causés par un défaut d'oxygénation des tissus.Sickle cell anemia is a hemoglobinopathy forms and severities very heterogeneous clinical affecting many organs in affected patients. For this reason the term major sickle cell syndrome is generally used. All major sickle cell syndromes have a common point mutation in the gene called β-globin mutation βs. This βs mutation leads to the synthesis of the protein hemoglobin S (HbS) is characterized by its ability to polymerize in its deoxygenated form. The polymerization of HbS is the trigger for the sickling of red blood cells and leads to many Hematological and hemorheological. These are at the origin of disorders hemodynamics, blood oxygenation and tissue perfusion with oxygen. This results in many acute complications (vaso-occlusive crisis, stroke, acute chest syndrome, etc..) And / or chronic (glomerulopathy, osteonecrosis of the femoral head etc.). Caused by a defect of tissue oxygenation
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