7,355 research outputs found
Greenhouse Gases Reforming and Hydrogen Upgrading by Using Warm Plasma Technology
Global warming is an alarming problem with adverse impact on climate change. Carbon dioxide (CO2) and methane (CH4) have been identified as the most significant greenhouse gases (GHG) normally arising from anthropogenic activities; therefore, promising treatment technologies are developing all over the world to resolve this problem. The warm plasma is an emergent process with low specific energy requirement capable to reach high temperature to produce excited species and support subsequent chemical reactions. Consequently, warm plasma reactors can be accomplished with simple structure reactors having high gas flow rates and treatment capacity. Plasma interaction with GHG leads into a molecular dissociation, mainly forming CO and H2, also known as syngas, which represents an alternative energy source with innovative applications in microturbines and fuel cells, among other emerging applications. The process here explained assures a significant reduction in CO2 emission and H2 yield upgrading. The reforming experimental results by using two warm plasma reactors are connected in series to improve the syngas yield. This alternative represents a great possibility for CO2 conversion
Gravitational Model of High Energy Particles in a Collimated Jet
Observations suggest that relativistic particles play a fundamental role in
the dynamics of jets emerging from active galactic nuclei as well as in their
interaction with the intracluster medium. However, no general consensus exists
concerning the acceleration mechanism of those high energy particles. A
gravitational acceleration mechanism is here proposed, in which particles
leaving precise regions within the ergosphere of a rotating supermassive black
hole produce a highly collimated flow. These particles follow unbound geodesics
which are asymptotically parallel to the spin axis of the black hole and are
characterized by the energy , the Carter constant and zero
angular momentum of the component . If environmental effects are
neglected, the present model predicts at distances of about 140 kpc from the
ergosphere the presence of electrons with energies around 9.4 GeV. The present
mechanism can also accelerate protons up to the highest energies observed in
cosmic rays by the present experiments.Comment: 27 pages and 5 figures. Accepted for publication in Astrophysical
Journal. arXiv admin note: text overlap with arXiv:1011.654
Ductus venosus agenesis and fetal malformations: what can we expect? - a systematic review of the literature
Background: The ductus venosus agenesis (DVA) is a rare condition with a variable prognosis that relies partly on the presence of associated conditions. The purpose of our study was to analyze the literature regarding the postnatal outcome of fetuses with DVA associated with fetal malformations, in order to discuss the best management options for couples. Methods: We performed a systematic review of the literature of MEDLINE and SCOPUS electronic databases in a 25-year period from 1992 to September 2017. Results: We found 340 cases of DVA associated with fetal abnormalities. The most common chromosomal abnormalities were: monosomy X (12/48, 25%), trisomy 21 (11/48, 22.9%) and trisomy 18 (6/48, 12.5%). From the 340 cases with DVA, in 31 cases the umbilical venous shunt type was not reported. Of the fetuses, 60.8% (188/309) had an extrahepatic umbilical venous drainage while 39.2% (121/309) presented an intrahepatic connection. The DVA was associated in 71 cases (23.0%) with cardiac abnormalities, in 82 cases (26.5%) with extracardiac abnormalities and in 85 cases (27.5%) with both cardiac and extracardiac abnormalities. Conclusion: DVA associated with both cardiac and extracardiac malformations may confer a poorer fetal outcome, a clinically relevant fact that should clarify what can be expected from this entity and help prenatal counseling
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