28,665 research outputs found
Cardiac troponin I but not cardiac troponin T adheres to polysulfone dialyser membranes in an in vitro haemodialysis model: explanation for lower serum cTnI concentrations following dialysis.
No full textBACKGROUND: Elevated serum cardiac troponin T (cTnT) and I (cTnI) can occur in patients with chronic kidney disease. Differences in cTn concentrations between cTnT and cTnI have been reported but the mechanism of such discrepancy has not been investigated. This study investigates the clearance of cTn with the aid of an in vitro model of haemodialysis (HD).
METHODS: Serum was obtained before and after a single session of dialysis from 53 patients receiving HD and assayed for cTnT and cTnI. An in vitro model of the dialysis process was used to investigate the mechanism of clearance of cTn during HD.
RESULTS: Serum cTnI was significantly lower (p=0.043) following a session of HD whereas cTnT concentrations were similar to those obtained before HD. Using an in vitro model of dialysis, it was demonstrated that cTnI is not dialysed from the vascular compartment but adheres to the dialyser membrane.
CONCLUSIONS: The adherence of cTnI to the dialyser membrane is responsible for the observed decrease in serum cTnI following a session of dialysis. The adherence of cTnT or T-I-C complex to the dialyser membrane could not be demonstrated and supports the observation that pre-HD and post-HD serum concentrations of cTnT are similar
Maternal cardiac function in early pregnancies with high uterine artery resistance
No full textOBJECTIVE: To compare the maternal cardiac function and serum concentration of cardiac troponin T (cTnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) in first-trimester patients, according to uterine artery Doppler velocimetry (UADV).
METHODS: This cross-sectional study included singleton pregnancies with normal UADV (n=17) and abnormal UADV (n=19). Maternal echocardiography was performed and blood samples were taken at 11-14 weeks. Echocardiographic parameters included: (a) left ventricular (LV) long axis velocities; (b) atrial size; (c) LV filling pressure; (d) the ratio of peak mitral flow velocity in early diastole and early mitral annular diastolic velocity (E/Ea ratio); and (e) the E/flow propagation velocity ratio. The maternal serum concentrations of cTnT and NT-proBNP were determined by sensitive and specific immunoassays. RESULTS: Patients with abnormal UADV had higher estimated left ventricular filling pressure (P=0.004), higher E/Ea ratio (P=0.03), higher E/flow propagation ratio (P=0.02), and lower LV long axis velocity (P=0.02) than those with normal UADV. There were no significant differences in the maternal serum concentration of cTnT or NT-proBNP.
CONCLUSIONS: Patients with abnormal UADV in the first trimester have higher left ventricular filling pressure and may have left ventricular systolic dysfunction
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Probabilistic framework to evaluate the resilience of engineering systems using Bayesian and dynamic Bayesian networks
No full textResilience indicators are a convenient tool to assess the resilience of engineering systems. They are often used in preliminary designs or in the assessment of complex systems. This paper introduces a novel approach to assess the time-dependent resilience of engineering systems using resilience indicators. A Bayesian network (BN) approach is employed to handle the relationships among the indicators. BN is known for its capability of handling causal dependencies between different variables in probabilistic terms. However, the use of BN is limited to static systems that are in a state of equilibrium. Being at equilibrium is often not the case because most engineering systems are dynamic in nature as their performance fluctuates with time, especially after disturbing events (e.g. natural disasters). Therefore, the temporal dimension is tackled in this work using the Dynamic Bayesian Network (DBN). DBN extends the classical BN by adding the time dimension. It permits the interaction among variables at different time steps. It can be used to track the evolution of a system's performance given an evidence recorded at a previous time step. This allows predicting the resilience state of a system given its initial condition. A mathematical probabilistic framework based on the DBN is developed to model the resilience of dynamic engineering systems. Two illustrative examples are presented in the paper to demonstrate the applicability of the introduced framework. One example evaluates the resilience of Brazil. The other one evaluates the resilience of a transportation system.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Integral Design & Managemen
First trimester maternal serum ischaemia-modified albumin: A marker of hypoxia-ischaemia-driven early trophoblast development
No full textBACKGROUND
A hypoxic intrauterine environment is believed to play a pivotal role in physiological trophoblast development. Ischaemia-modified albumin (IMA) is used in the measurement of cardiac ischaemia. We aimed to test the hypothesis that maternal serum IMA may be elevated in early pregnancy as a measurable manifestation of intrauterine ischaemia.
METHODS
Prospective observational study in healthy women with singleton pregnancies ( n = 66) and non-pregnant controls ( n = 26). Maternal serum IMA levels were measured at 11–13 weeks of gestation and in non-pregnant women.
RESULTS
The median IMA level in the pregnant group [115.14 kU/l; interquartile range (IQR) 102.33–124.71 kU/l] was significantly higher ( P 95 kU/l) in 86% of women.
CONCLUSIONS
In early pregnancy, IMA levels were above the concentration used for the diagnosis of myocardial ischaemia in most women, and should therefore not be used as a marker for cardiac ischaemia in pregnancy. Maternal serum IMA is elevated to supra-physiological levels in early normal pregnancy supporting the hypothesis that normal trophoblast development is associated with a hypoxic intrauterine environment, although other mechanisms leading to an IMA increase cannot be excluded
Defective endovascular trophoblast invasion in the first trimester is associated with increased maternal serum ischemia-modified albumin
No full textIschemia-modified albumin (IMA), a protein elevated in cardiac ischemia, is also increased to supra-physiological levels in early normal pregnancy. This finding supports the hypothesis that normal trophoblast development is stimulated by a hypoxic intrauterine environment. The aim of this study was to examine whether first trimester IMA levels are further elevated with defective trophoblast development.Prospective study of healthy women with singleton pregnancies undergoing nuchal translucency assessment at 11-14 weeks. First trimester maternal serum IMA concentrations in those subsequently developing pre-term pre-eclampsia (n = 19) were compared to randomly chosen controls with normal pregnancy outcome (n = 69).Median first trimester serum IMA concentrations were significantly higher in women who subsequently developed pre-eclampsia (median 126.5 kU/L, interquartile range (IQR) 114.33-134.36 kU/L) when compared to those with normal pregnancy outcome (median 115.01 kU/L, IQR 102.29-124.81 kU/L, P = 0.02).Maternal serum IMA levels are elevated in the first trimester in women with pre-eclampsia, a clinical manifestation of defective endovascular trophoblast development. This suggests that abnormally high intrauterine hypoxia and subsequent reperfusion oxidative damage may be associated with defective trophoblast development. First trimester serum IMA may be a potential biomarker for abnormal placental development
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Resourcefulness quantification approach for resilient communities and countries
No full textAvailability of resources is one of the primary criteria for communities to attain a high resilience level during disaster events. This paper introduces a new approach to evaluate resourcefulness at the community and national scales. Resourcefulness is calculated using a proposed composite resourcefulness index, which is a combination of several resourcefulness indicators. To build the resourcefulness index, resourcefulness indicators representing the different aspects of resourcefulness are collected from renowned literary publications. Every indicator is assigned a measure to make it quantifiable. Time-history data for the measures are needed to perform the analysis. While these data could be obtained from different sources, acquiring a full set of data is quite challenging. Hence, to account for missing data, the Multiple Imputation (MI) and the Markov Chain Monte Carlo (MCMC) data imputation methods are adopted. The data are then normalized, assigned weights, and aggregated to obtain the resourcefulness index. A case study is performed to demonstrate the applicability of the approach. The resourcefulness indexes of two countries, namely the United States and Italy, are evaluated. Results show that resourceful communities/countries are more resilient during disaster events as they have more tools to come up with solutions. It is also shown that knowing the current resourcefulness level helps in better identifying what aspects should be improved.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Integral Design & Managemen
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Self-archiving practice and the influence of publisher policies in the social sciences
No full textAuthors in different disciplines exhibit very different behaviours on the so-called ‘green’ road to open access, i.e. self-archiving. This study looks at the self-archiving behaviour of authors publishing in leading journals in six social science disciplines. It tests the hypothesis that authors are self-archiving according to the norms of their respective disciplines rather than following self-archiving policies of publishers, and that, as a result, they are self-archiving significant numbers of publisher PDF versions. It finds significant levels of
self-archiving, as well as significant self-archiving of
the publisher PDF version, in all the disciplines
investigated. Publishers’ self-archiving policies have
no influence on author self-archiving practice
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