130,533 research outputs found
Enhancing the Oxygen Evolution Reaction Activity of Sputtered Ni, NiO, and NiNiO Thin Films by Incorporating Fe
No full textJournal article. Faculty of Natural and Agricultural Science, North--West University- PotchefstroomThe effect of Fe-containing alkaline electrolyte, on the oxygen evolution reaction (OER) activity of Ni electrocatalysts, has long been of interest as Fe increases the OER activity of Ni electrocatalysts. However, controversy exists as to whether it is surface or bulk Fe that is responsible for the increased activity. In this study, magnetron sputtering was employed to sputter Ni, NiO and NiNiO thin film electrocatalysts to study the effect that different concentrations of Fe in the electrolyte have on their OER activities. It was found that increasing concentrations of Fe increasingly enhanced the OER activity of these thin film electrocatalysts until the electrolyte was saturated with Fe. The lowest overpotential achieved is 279 mV (at 10 mA cm−2) for NiNiO cycled in KOH containing 1 mM Fe, with all three thin film electrocatalysts exhibiting overpotentials within the same range after 30 voltammetry cycles in 0.9 ppm Fe and 1 mM Fe. All Tafel slopes are between 36 and 45 mV dec−1 indicating similar kinetics for the samples cycled in different Fe concentrations. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy results show that Fe is found in the top layers of the electrocatalysts after cycling
The role of stretch-activated channels in atrial fibrillation and the impact of intracellular acidosis
No full textThe incidence of atrial fibrillation correlates with increasing atrial size. The electrical consequences of atrial stretch contribute to both the initiation and maintenance of atrial fibrillation. It is suggested that altered calcium handling and stretch-activated channel activity could explain the experimental findings of stretch-induced depolarisation, shortened refractoriness, slowed conduction and increased heterogeneity of refractoriness and conduction. Stretch-activated channel blocking agents protect against these pro-arrhythmic effects. Gadolinium, GsMTx-4 toxin and streptomycin prevent the stretch-related vulnerability to atrial fibrillation without altering the drop in refractory period associated with stretch. Changes the activity of two-pore K+ channels, which are sensitive to stretch and pH but not gadolinium, could underlie the drop in refractoriness. Intracellular acidosis induced with propionate amplified the change in refractoriness with stretch in the isolated rabbit heart model in keeping with the clinical observation of increased propensity to atrial fibrillation with acidosis. We propose that activation of non-specific cation stretch-activated channels provides the triggers for acute atrial fibrillation with high atrial pressure while activation of atrial two-pore K+ channels shortens atrial refractory period and increases heterogeneity of refractoriness, providing the substrate for atrial fibrillation to be sustained. Stretch-activated channel blockade represents an exciting target for future antiarrhythmic drugs.Daniel M. Ninio and David A. Sain
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Passive pericardial constraint protects against stretch-induced vulnerability to atrial fibrillation in rabbits
No full text© 2006 by the American Physiological Society.Atrial fibrillation is more common in conditions with elevated atrial pressure and can be induced experimentally with acute increases in atrial pressure. We examined the effect of increased atrial pressure with and without pericardial constraint to better separate the effects of increased pressure and atrial stretch. In Langendorff-perfused rabbit hearts with intact pericardium, after ligating the pulmonary and caval veins, intra-atrial pressures were increased in a stepwise manner by adjusting the pulmonary outflow cannula. Rapid burst pacing was applied to induce atrial fibrillation at increasing intra-atrial pressures from 0 to 24 cmH(2)O. The atrial refractory period was recorded at each pressure using a single extra stimulus. The protocol was repeated after the pericardium was removed. When the pericardium was intact, atrial stretch was limited by passive constraint, and sustained atrial fibrillation could not be induced despite atrial pressures in excess of 20 cmH(2)O. In contrast, when the pericardium was removed, atrial fibrillation could be reliably induced when atrial pressure exceeded 15 cmH(2)O. This suggests that the electrophysiological effects of acute atrial volume loading rely on atrial stretch rather than increased atrial pressure alone.Daniel M. Ninio and David A. Sain
Docosahexaenoic acid-rich fish oil improves heart rate variability and heart rate responses to exercise in overweight adults
No full textDietary fish oil supplementation and regular physical activity can improve outcomes in patients with established CVD. Exercise has been shown to improve heart rate variability (HRV), a predictor of cardiac death, but whether fish oil benefits HRV is controversial. Obese adults at risk of future coronary disease have impaired HRV and may benefit from these interventions. We evaluated the effect of DHA-rich tuna fish oil supplementation with and without regular exercise on HRV in sedentary, overweight adults with risk factors for coronary disease. In a randomised, double-blind, parallel comparison, sixty-five volunteers consumed 6 g fish oil/d (DHA 1·56 g/d, EPA 0·36 g/d) or sunflower-seed oil (placebo) for 12 weeks. Half of each oil group also undertook regular moderate physical activity (3 d/week for 45 min, at 75% of age-predicted maximal heart rate (HR)). Resting HR and the HR response to submaximal exercise were measured at weeks 0, 6 and 12. In forty-six subjects, HRV was also assessed by power spectrum analysis of 20 min electrocardiogram recordings taken supine at baseline and 12 weeks. Fish oil supplementation improved HRV by increasing high-frequency power, representing parasympathetic activity, compared with placebo (P = 0·01; oil x time interaction). It also reduced HR at rest and during submaximal exercise (P = 0·008; oil x time interaction). There were no significant fish oil x exercise interactions. Dietary supplementation with DHA-rich fish oil reduced HR and modulated HRV in keeping with an improved parasympathetic–sympathetic balance in overweight adults with risk factors for future coronary disease.Daniel M. Ninio, Alison M. Hill, Peter R. Howe, Jonathan D. Buckley and David A. Sain
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
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Midichloria mitochondrii, an intracellular alphaproteobacteria considered as a symbiont of the tick Ixodes ricinus, found circulating in roe-deer (Capreolus capreolus) through molecular and serological evidences
No full textThe hard tick Ixodes ricinus, vector of pathogens important for both human and animal health (Parola and Raoult, 2001; Socolovschi et al., 2009) harbours Midichloria mitochondrii (order Rickettsiales; family Midichloriaceae), an endocytobiotic bacterium found in 100% of the females (Epis et al. 2008). Although its impact on the biology of its arthropod-host is still unknown, M. mitochondrii has first been detected in the reproductive apparatus of adult females where it is the most abundant and, more recently, also in the salivary glands of the parasite, suggesting the hypothesis of its transmission to the vertebrate host during the tick bite (Mariconti et al., 2012). To validate this hypothesis, the presence of M. mitochondrii DNA in the vertebrate hosts (dogs, sheep, horses and humans) was detected through the amplification of the 16S rDNA gene (Mariconti et al., 2012; Bazzocchi et al. 2013) and serological analysis on sera collected from humans and dogs exposed to the tick bite (Mariconti et al. 2012).
This experimental work aims to investigate the circulation of M. mitochondrii in roe deer (C. capreolus), which is the host of choice especially for the adult stage of I. ricinus in Europe and is therefore considered an efficient animal-sentinel for possible etiologic agents transmitted by this hard tick species. Briefly, we evaluate: 1) the presence of circulating M. mitochondrii DNA in blood of seven roe deer, different in age and sex, from a defined and controlled area (South-East Toulouse, France); 2) the immunological response of the roe deer individuals against a specific recombinant flagellar protein of M. mitochondrii (rFliD).
Molecular analysis were conducted using specific qualitative PCRs for 12S rDNA of C. capreolus (Fajardo et al. (2008) and 16S rDNA of M. mitochondrii ( Epis et al. 2008) after DNA extraction from blood samples. Immunological analysis were conducted using the recombinant protein rFLID as antigen in ELISA and Western blot testsAfter molecular analysis, only three of the seven analyzed blood samples were positive to M. mitochondrii DNA. On the base of the already set cut-off (designed on negative sera), six out of seven roe deer individuals resulted positive in ELISA. Western blot assay instead, showed the presence of a band, at the expected molecular weight, in all the examined samples, except for the negative control.
In conclusion, M. mitochondrii was detected in roe deer individuals through molecular and serological analyses, proving the circulation of M. mitochondrii in C. capreolus parasitized by I. ricinus. As already demonstrated in other studies, roe deer is a good subject to study the spread of tick-borne pathogens (or potentially pathogen). Further studies will allow the understanding of biological interactions of M. mitochondrii, the possible replication of this bacterium inside the host and its role in possible pathological alterations after its transmission
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
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