1,720,989 research outputs found
MECHANICAL INVESTIGATIONS ON ARTIFICIAL HEMODIALYSIS
No full textThe studies on cardiovascular system introduced by Max Anliker and coll have been very important because have opened a new method to look to determine the mechanical properties of the wall of the large vessels.
The data have given the constant phase velocities for the pressure, axial and torsion waves, also the laws of attenuation of these waves were egual with exponential law with a negative constant multiplied by proportion of distance and wavelength. The law of attenuation has open a great problem of discussion, because the biological tissues have viscous-elastic properties but not linear as everybody who knows such materials knows.
Now if a biological soft tissue has a deformation to return to the original condition is not given by a curve of presenting an egual shape but the presence of Coulomb resistance to deformation gives the particular low damping of the return to original dimension.
The Knopoff theory has been used to arrive to a solution and explication of the experimental results by Anliker. We do not discuss now the mathematical problems and the equations connected to this theoretical biomechanical analysis, but if somebody is interested to discuss we have no problems of fit, because wee must see the interest of this medical people present now.
When a transplant of organ is made we have the arteries of two different persons are connected and we are in presence of two similar but not egual wall are sutured, if the second is more soft then the previous part, will generate to a short period of time a stenosis due to a turbulent movement of the blood in the initial part of the new artery, with the process of sedimentation of the blood cells and obviously the sutured part is closed, the blood has at first difficulty to enter in the donor organs and day by day the blood stops and the donor organ is out owing to a necrosis. We have seen how this process can arrive to interest tilt 10% of patient, when the different age between patient and donor is of 15 years and the donor is younger in kidney transplantation.
The definition of this effect was called Bononiensis Control Parameter (BCP).
In conclusion, the importance of the determination of the viscous-elastic properties of the great vessels of cardiovascular system of a patient is very important to define and know when a transplant is necessary, looking for and selecting the more similar condition of the donor vessels or prosthesis
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
Fluidodynamic evaluation of arteriovenous fistulae for hemodialysis
No full textArteriovenous fistulae (AVF) are commonly used in dialysis treatment of uremic patients. However, many AVF create problems and have to be re-examined. Problems arise in the cannulation site and must be treated with antibiotics, and stenosis, both in the arterial and in the venous side of the AVF. In the worst case, the AVF must be replaced for treatment to continue. However, this can only be repeated once before the AVF site is no longer viable. This increases the discomfort, the morbidity and the mortality of the dialysis patient. Several kinds of AVF were studied to determine whether flow disturbances give rise to these complications. Many studies have already demonstrated the importance of hemodynamic factors in vascular disease pathogenesis. These factors include: the pulsatility of flow, the elasticity of the vessel, the non-Newtonian blood, flow behavior and, very importantly for AVF, the vessel geometry. In model studies, intimal changes have been observed in bends and bifurcations, regions of vessel construction and vessel stenosis. In these regions, blood flow changes abruptly and this contributes to arterial disease. We prepared several one-to-one, true-to-scale elastic silicon rubber models of different AVF. The AVF models were based on angiographic studies of chronic dialysis patients and on AVF from the arms of cadavers. The models had a similar compliance to that of the human blood vessel. Flow was visualized using photoelasticity apparatus and a birefringent blood-like fluid. This method is suitable to analyze the spatial configuration of flow profiles, to differentiate laminar flow from disturbed flow, and to visualize flow separation, vortex formation and secondary flow. It was found that AVF create disturbances that are not found under normal physiological flow conditions. The X-formed AVF was very unsatisfactory, creating significant flow disturbances. The AVF had high velocity fluctuations. These could lead, for example, to aneurysm formation. A better configuration would be an end-to-end AVF. However, this formation creates other complications. For example, there is not enough blood to the hand and parts of the hand lose feeling. The recommended AVF would be an end-to-side anastomosis. In this case, attention is needed for placement geometry, to minimize additional flow disturbances. Several models as well as patient angiographic studies are discussed
STUDY ON THE MECHANICAL PROPERTIES OF THE TISSUES OF THE GREAT ARTERIES
No full textThe studies on cardiovascular system introduced by Max Anliker and coll have been very important because have opened a new method to look to determine the mechanical properties of the wall of the large vessels.
The data have given the constant phase velocities for the pressure, axial and torsion waves, also the laws of attenuation of these waves were egual with exponential law with a negative constant multiplied by proportion of distance and wavelength. The law of attenuation has open a great problem of discussion, because the biological tissues have viscous-elastic properties but not linear as everybody who knows such materials knows.
Now if a biological soft tissue has a deformation to return to the original condition is not given by a curve of presenting an egual shape but the presence of Coulomb resistance to deformation gives the particular low damping of the return to original dimension.
The Knopoff theory has been used to arrive to a solution and explication of the experimental results by Anliker. We do not discuss now the mathematical problems and the equations connected to this theoretical biomechanical analysis, but if somebody is interested to discuss we have no problems of fit, because wee must see the interest of this medical people present now.
When a transplant of organ is made we have the arteries of two different persons are connected and we are in presence of two similar but not egual wall are sutured, if the second is more soft then the previous part, will generate to a short period of time a stenosis due to a turbulent movement of the blood in the initial part of the new artery, with the process of sedimentation of the blood cells and obviously the sutured part is closed, the blood has at first difficulty to enter in the donor organs and day by day the blood stops and the donor organ is out owing to a necrosis. We have seen how this process can arrive to interest tilt 10% of patient, when the different age between patient and donor is of 15 years and the donor is younger in kidney transplantation.
The definition of this effect was called Bononiensis Control Parameter (BCP).
In conclusion, the importance of the determination of the viscous-elastic properties of the great vessels of cardiovascular system of a patient is very important to define and know when a transplant is necessary, looking for and selecting the more similar condition of the donor vessels or prosthesis
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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