1,720,969 research outputs found
Ethiopathogenesis, diagnosis and prevention of vascular calcification in end stage renal disease
No full textExtensive atherosclerosis and heavy vascular and valvular calcifications are common complications of end stage renal disease (ESRD) and are very likely related to the high incidence of cardiovascular disease in these patients. The greatly increased incidence of cardiovascular disease is only partly explained by traditional risk factors for atherosclerosis. In ESRD, vascular calcification occurs both in the vascular intima layer and in the tunica media. Intimal calcification is disseminated and is characteristically associated with damaged and abnormally functioning endothelium, and macrophage and vascular smooth muscle cell (VSMC) infiltration typical of atherosclerosis. On the contrary, medial calcification occurs in patchy distribution and the most frequent cell types found in its vicinity are the VSMC and macrophage. The uremic state is associated with numerous metabolic abnormalities and endocrine disturbances primarily involving calcium and phosphorus metabolism. Furthermore, chronic kidney disease and dialysis are considered states of active and strong inflammatory response. These dysfunctions occur early in the course of renal failure and likely contribute to the development and progression of vascular calcification and atherosclerosis. For many years, vascular calcification was considered solely the result of a passive deposition of hydroxyapatite crystals in the arterial wall due to elevated calcium-phosphate ion product. However, a large body of evidence has now shown that this is a highly regulated process governed by factors that closely resemble calcium deposition in bone tissue. In fact, vascular calcification requires changes in the phenotype of VSMC and the expression of several proteins normally involved in bone metabolism. This review is centered on the etiopathogenesis of vascular calcification in ESRD, its detection with modern imaging modalities and the therapeutic approaches currently available to slow its progression
Coronary artery calcium screening : implications for clinical practice
No full textCardiovascular disease is the most common cause of death in the Western hemisphere, and in the majority of cases the event announcing the presence of atherosclerosis is either sudden death or a disabling myocardial infarction or stroke. Although traditional risk factors are present in most individuals suffering a cardiovascular event, the prognostic ability of risk factors to predict events in the short term is limited. The focus of research has therefore turned to the application of noninvasive modalities to image the atherosclerotic plaque in its preclinical stages. Measurements of coronary artery calcium serve as a quantitative reflection of the severity of coronary artery disease, and greater calcium burdens correlate with more advanced disease. Coronary artery calcium has been shown in several studies to add prognostic value to traditional risk factors in patients at intermediate risk, and in this group of patients it may be cost effective. There is, however, an inherent danger in raising the cost of care by increasing downstream unnecessary testing if such screening were to be applied to low-risk individuals. This article is a systematic review of the most relevant literature regarding the utilization of coronary artery calcium screening as a tool to refine risk assessment and to evaluate the efficacy of therapy for atherosclerosis
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
Pulse wave velocity is inversely related to vertebral bone density in hemodialysis patients
No full textAbnormalities of bone mineral metabolism in patients with stage-5 chronic kidney disease may contribute to the high incidence of cardiovascular disease. Noninvasive imaging methods may help predict the simultaneous presence of vasculopathy and bone disease. Accordingly, we measured pulse wave velocity and bone mineral density (BMD), and T-scores (number of SDs below the BMD of a younger reference group) of the spine by both dual energy x-ray absorptiometry and quantitative computed tomography (QCT) in 110 maintenance hemodialysis patients. Older age, white race, diabetes mellitus, lower diastolic blood pressure, and lower albumin levels were associated with lower QCT-assessed T-scores (each Por=9 m/s was 32.4%, 61.8%, and 76.5% for participants in the highest to the lowest tertile of QCT-assessed BMD; Por=9 m/s for patients taking vitamin D(3) or its analogs was 0.51 (95% CI: 0.19 to 1.39). In conclusion, low spine BMD is associated with increased PWV in stage-5 chronic kidney disease, supporting the notion of a close interaction of vascular and bone disease in this patient group. QCT and not dual energy x-ray absorptiometry should be used to assess spine BMD in dialysis patients
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
Integration of clinical and imaging data to predict death in hemodialysis patients
No full textIn a prior publication, we demonstrated that a model integrating clinical and simple imaging data predicted the presence and severity of coronary artery calcification in prevalent hemodialysis patients. Herein we report the ability of the same model to predict all-cause death. We assessed all-cause mortality in 141 consecutive maintenance hemodialysis patients from two dialysis centers followed for a median of 79 months from enrollment. Patients were risk stratified according to a simple cardiovascular calcification index (CCI) that included patient's age, dialysis vintage, calcification of the cardiac valves, and abdominal aorta. The mean patients' age was 55 ± 14 years. Abdominal aorta calcification was present in 57% of the patients, and 44% and 38% had aortic and mitral valve calcification, respectively. During follow-up, 75 deaths (93 deaths per 1000 person-years) were recorded. The CCI was linearly associated with risk of death, such that the unadjusted hazard risk (HR) increased by 12% for each point increase in CCI (P < 0.001). Further adjustments for age, sex, study center, diabetes mellitus, history of cardiovascular disease, hypertension, congestive heart failure, left ventricular hypertrophy, systolic, and diastolic blood pressure did not substantially change the strength of this association (HR 1.10; 95%CI: 1.00-1.21; P = 0.03). The CCI is a simple clinical model that can be used to risk stratify maintenance hemodialysis patients
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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