2,537 research outputs found
Acute cardiovascular effects of exposure to air pollution: components, vascular mechanisms and protecting the public
No full textExposure to air pollution, particularly fine and ultrafine particulate matter
derived from combustion sources, has been consistently associated with
increased cardiovascular morbidity and mortality. Recent controlled
exposure studies demonstrate that short-term exposure to diesel exhaust,
which can contribute up to 40% of urban particulate air pollution, results in
impaired vascular endothelial and fibrinolytic function in healthy volunteers,
and increased exercise-induced myocardial ischaemia in patients with
coronary heart disease. These observations may, in part, explain the
observed increase in cardiovascular events following exposure to air
pollution.
Despite these observations there remain uncertainties regarding the key
constituents of the air pollution mixture that mediate these adverse effects,
and the underlying physiological and biological pathways involved. In these
studies, using two controlled exposure facilities, I explored the vascular
effects of the most prevalent gaseous component of the air pollution mixture
– nitrogen dioxide – and the mechanisms responsible for impaired
vasomotor function following exposure to diesel exhaust. Furthermore, I
investigated the effect of acute exposure to “real-world” urban air pollution
in both healthy volunteers and patients with coronary heart disease, and the
effect of reducing that exposure using a simple facemask. In total, 10 healthy volunteers were exposed to nitrogen dioxide, and 29
healthy volunteers exposed to dilute diesel exhaust in a series of doubleblind
randomised crossover studies. Exposure to nitrogen dioxide had no
effect on either vasomotor function or endogenous fibrinolysis, providing
indirect evidence that the adverse vascular effects are predominantly driven
by particulate components. Following exposure to diesel exhaust there was
no up regulation of endothelin-1 production, although there was increased
vasoconstriction to intra-arterial infusion of endothelin-1. Following
endothelin A receptor antagonism, there was attenuated vasodilatation
following exposure to diesel exhaust as compared to air, an effect abrogated
by endothelin B receptor antagonism. My findings suggest that the
endothelin system does not play a central role in the adverse vascular effects
of air pollution, but given the tonic interaction between the endothelin and
nitric oxide systems, these observations could be explained by reduced nitric
oxide bioavailability. Following diesel exhaust inhalation, plasma nitrite
concentrations (as a marker for nitric oxide generation) are markedly
increased without changes in haemodynamics or basal blood flow consistent
with increased nitric oxide consumption. In the presence of a nitric oxide
clamp, and without endogenous nitric oxide release, the vascular responses
to vasodilators are similar. This perturbation of nitric oxide consumption and
release appears to underlie the observed vascular endothelial effects. Fifteen healthy volunteers and 98 patients with coronary artery disease were
recruited in Beijing, China. Subjects walked along a predefined city centre
route for 2 hours in the presence and absence of a highly efficient facemask
to reduce personal particulate air pollution exposure in an open label
randomised crossover study. When wearing a facemask, there was an
attenuation of exercise-induced increases in blood pressure, an improvement
in heart rate variability, reduced myocardial ischaemia and subjects reported
fewer symptoms. My findings have identified the biological mechanisms underlying the
adverse vascular effects of exposure to diesel exhaust, and have helped to
clarify the components responsible for these effects. Moreover, I have
identified important benefits of reducing personal exposure to particulate
matter using a simple facemask that have the potential to reduce
cardiovascular events in patients living in urban or industrialised areas.
Ongoing research in this area will provide further insight into the underlying
vascular mechanisms, and the potential benefits of reducing particulate air
pollution exposure, and may result in important targeted interventions to
reduce the impact of air pollution on cardiovascular health
Draft toxicological profile for JP-5, JP-8, and jet A fuels
No full textA Toxicological Profile for JP-5 and JP-8 was released in 1998. This present edition supersedes any previously released draft or final profile.Chemical manager(s)/author(s): John Risher, Obaid Faroon, ATSDR, Division of Toxicology and Human Health Sciences, Atlanta, GA; Fernando Llados, Lisa Ingerman, Mario Citra, SRC, Inc., North Syracuse, NY
Safety of Rotational Atherectomy Using the Radial Access in Patients With Severe Aortic Stenosis
No full textDespite frequent percutaneous coronary intervention (PCI) in calcified vessels of older patients, rotational atherectomy (RA) has not been endorsed in patients with severe aortic stenosis (AS) due to safety concerns and lack of data. We explored periprocedural safety and mortality in severe AS patients undergoing RA. Prospective anonymized clinical, echocardiographic, procedural and outcome data of patients undergoing RA PCI between January 2012 and July 2018 were retrospectively extracted from the institutional coronary database. Patients with severe AS undergoing RA PCI were 1:1 propensity matched with patients undergoing RA PCI in the absence of AS. Outcomes of interest were RA related periprocedural complications, 30-day and 1-year mortality. A prespecified subgroup analysis examined the influence of transcatheter aortic valve replacement on mortality following RA PCI. A total of 544 patients underwent RA PCI; 478 without AS and 66 with AS. Propensity matching yielded 35 matched pairs with improved balance in covariates of interest and no significant differences in baseline characteristics postmatching. In the matched cohort (n = 70) slow flow/no-reflow, coronary dissection, perforation, and hemodynamic instability were rare and not significantly different. Survival analyses revealed significantly higher 30-day (Log-Rank p = 0.02) and 1-year mortality (Log rank p = 0.02, HR 5.24 [95% CI 1.13 to 24.28]) in the severe AS group; driven by a fivefold increase in the hazard of death among patients who did not undergo transcatheter aortic valve replacement HR 4.98 [95% CI 1.03 to 24.1]. In conclusion, our study of 70 patients undergoing radial RA PCI suggests that it can be safely performed in patients with severe AS. Long-term outcomes after RA in patients with severe AS are determined by the presence of the valve disease and other co-morbidities. (C) 2019 Elsevier Inc. All rights reserved
Shock tube study of JP-10 ignition delay time
No full textJP-10 (exo-tetrahydrodicyclopentadiene, C10H16) ignition delay times were measured in a preheated shock tube. The vapor pressures of the JP-10 were measured directly by using a high-precision vacuum gauge, to remedy the difficulty in determining the gaseous concentrations of heavy hydrocarbon fuel arising from the adsorption on the wall in shock tube experiments. The whole variation of pressure and emission of the OH or CH radicals were observed in the ignition process by a pressure transducer and a photomultiplier with a monochromator. The emission of the OH or CH radicals was used to identify the time to ignition. Experiments were performed over the pressure range of 151-556 kPa, temperature range of 1000-2100 K, fuel concentrations of 0.1%-0.55% mole fraction, and stoichiometric ratios of 0.25, 0.5, 1.0 and 2.0. The experimental results show that for the lower and higher temperature ranges, there are different dependency relationships of the ignition time on the temperature and the concentrations of JP-10 and oxygen
Angiography-derived index of microcirculatory resistance as a novel, pressure-wire-free tool to assess coronary microcirculation in ST elevation myocardial infarction
No full textImmediate assessment of coronary microcirculation during treatment of ST elevation myocardial infarction (STEMI) may facilitate patient stratification for targeted treatment algorithms. Use of pressure-wire to measure the index of microcirculatory resistance (IMR) is possible but has inevitable practical restrictions. We aimed to develop and validate angiography-derived index of microcirculatory resistance (IMRangio) as a novel and pressure-wire-free index to facilitate assessment of the coronary microcirculation. 45 STEMI patients treated with primary percutaneous coronary intervention (pPCI) were enrolled. Immediately before stenting and at completion of pPCI, IMR was measured within the infarct related artery (IRA). At the same time points, 2 angiographic views were acquired during hyperaemia to measure quantitative flow ratio (QFR) from which IMRangio was derived. In a subset of 15 patients both IMR and IMRangio were also measured in the non-IRA. Patients underwent cardiovascular magnetic resonance imaging (CMR) at 48 h for assessment of microvascular obstruction (MVO). IMRangio and IMR were significantly correlated (rho: 0.85, p < 0.001). Both IMR and IMRangio were higher in the IRA rather than in the non-IRA (p = 0.01 and p = 0.006, respectively) and were higher in patients with evidence of clinically significant MVO (> 1.55% of left ventricular mass) (p = 0.03 and p = 0.005, respectively). Post-pPCI IMRangio presented and area under the curve (AUC) of 0.96 (CI95% 0.92-1.00, p < 0.001) for prediction of post-pPCI IMR > 40U and of 0.81 (CI95% 0.65-0.97, p < 0.001) for MVO > 1.55%. IMRangio is a promising tool for the assessment of coronary microcirculation. Assessment of IMR without the use of a pressure-wire may enable more rapid, convenient and cost-effective assessment of coronary microvascular function
Dynamics of Network Formation Processes in the Co-Author Model
No full textThis article studies the dynamics in the formation processes of a mutual consent network in game theory setting: the Co-Author Model. In this article, a limited observation is applied and analytical results are derived. Then, 2 parameters are varied: the number of individuals in the network and the initial probability of the links in the network in its initial state. A simulation result shows a finding that is consistent with an analytical result for a state of equilibrium while it also shows different possible equilibria.Dynamics, Network, Game Theory, Model,Simulation, Equilibrium, Complexity
An equivalent formulation of the Fan-Raspaud Conjecture and related problems
No full textIn 1994, it was conjectured by Fan and Raspaud that every simple bridgeless cubic graph has three perfect matchings whose intersection is empty. In this paper we answer a question recently proposed by Mkrtchyan and Vardanyan, by giving an equivalent formulation of the Fan-Raspaud Conjecture. We also study a possibly weaker conjecture originally proposed by the first author, which states that in every simple bridgeless cubic graph there exist two perfect matchings such that the complement of their union is a bipartite graph. Here, we show that this conjecture can be equivalently stated using a variant of Petersen-colourings, we prove it for graphs having oddness at most four and we give a natural extension to bridgeless cubic multigraphs and to certain cubic graphs having bridges
Ephemisms as communication vehicle in the Tiv language and literature
No full textThe beauty of Tiv language and literature is achieved when communication or discourse is laced with euphemistic expressions. Euphemisms aid in turning impolite utterances into polite ones. This study, therefore, investigates the communicative potentials of euphemisms in the Tiv language and literature. The study discusses formations of euphemisms, classifies euphemisms and explores the effects of euphemisms. Connotative theory of meaning has been deployed in this study because the interpretation of euphemisms is contextually and connotatively loaded. Methodologically, the author used primary and secondary materials. The author used a participant-observation tool for data collection. Being a native speaker of the Tiv language, the author collected, translated and classified euphemisms. Secondary materials were sourced from textbooks, journal articles, online sources and dictionaries. The following findings were made: euphemisms constitute phrasal or idiomatic synonyms; they beautify or spice our daily communication; they can becloud meanings. This study will benefit preachers, writers, lecturers/teachers, researchers, semanticists, public speakers, politicians and students
Open Access to Peer-Reviewed Research through Author/Institution Self-Archiving: Maximizing Research Impact by Maximizing Online Access
No full textAll refereed journals will soon be available online; most of them already are. This means that anyone will be able to access them from any networked desk-top. The literature will all be interconnected by citation, author, and keyword/subject links, allowing for unheard-of power and ease of access and navigability. Successive drafts of pre-refereeing preprints will be linked to the official refereed draft, as well as to any subsequent corrections, revisions, updates, comments, responses, and underlying empirical databases, all enhancing the self-correctiveness, interactivity and productivity of scholarly and scientific research and communication in remarkable new ways. New scientometric indicators of digital impact are also emerging <http://opcit.eprints.org> to chart the online course of knowledge. But there is still one last frontier to cross before science reaches the optimal and the inevitable: Just as there is no longer any need for research or researchers to be constrained by the access-blocking restrictions of paper distribution, there is no longer any need to be constrained by the impact-blocking financial fire-walls of Subscription/Site-License/Pay-Per-View (S/L/P) tolls for this give-away literature. Its author/researchers have always donated their research reports for free (and its referee/researchers have refereed for free), with the sole goal of maximizing their impact on subsequent research (by accessing the eyes and minds of fellow-researchers, present and future) and hence on society. Generic (OAi-compliant) software is now available free so that institutions can immediately create Eprint Archives in which their authors can self-archive all their refereed papers for free for all forever <http://www.eprints.org/>. These interoperable Open Archives <http://www.openarchives.org> will then be harvested into global, jointly searchable "virtual archives" (e.g., <http://arc.cs.odu.edu/>). "Scholarly Skywriting" in this PostGutenberg Galaxy will be dramatically (and measurably) more interactive and productive, spawning its own new digital metrics of productivity and impact, allowing for an online "embryology of knowledge.
Why hasn't electronic bill presentment and payment taken off?
No full textThe delivery and payment of bills over the Internet could offer many advantages—low processing costs and enhanced marketing opportunities for billers, savings in time and postage for customers. Nevertheless, electronic billing has not found favor with potential users. A lack of coordination among billers and customers, combined with the high fixed costs of the new technology, may help account for the cool reception.Electronic funds transfers ; Electronic commerce ; Technology ; Payment systems
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