1,454 research outputs found
Electrical charging of ash in Icelandic volcanic plumes
The existence of volcanic lightning and alteration of the atmospheric
potential gradient in the vicinity of near-vent volcanic plumes provides strong
evidence for the charging of volcanic ash. More subtle electrical effects are
also visible in balloon soundings of distal volcanic plumes. Near the vent,
some proposed charging mechanisms are fractoemission, triboelectrification, and
the so-called "dirty thunderstorm" mechanism, which is where ash and convective
clouds interact electrically to enhance charging. Distant from the vent, a
self-charging mechanism, probably triboelectrification, has been suggested to
explain the sustained low levels of charge observed on a distal plume. Recent
research by Houghton et al. (2013) linked the self-charging of volcanic ash to
the properties of the particle size distribution, observing that a highly
polydisperse ash distribution would charge more effectively than a monodisperse
one. Natural radioactivity in some volcanic ash could also contribute to
self-charging of volcanic plumes. Here we present laboratory measurements of
particle size distributions, triboelectrification and radioactivity in ash
samples from the Gr\'{i}msv\"{o}tn and Eyjafjallaj\"{o}kull volcanic eruptions
in 2011 and 2010 respectively, and discuss the implications of our findings.Comment: XV Conference on Atmospheric Electricity, 15-20 June 2014, Norman,
Oklahoma, US
Evaluating the performance of low-energy feed forward osmosis system for desalination using impaired and saline water sources
Forward Osmosis (FO) is a natural process of treating water or wastewater due to the difference in osmotic pressures. FO is a membrane separation technology, applicable to food processing, industrial wastewater treatment and seawater or brackish water desalination. The phenomena of FO processes occur whereby water molecules are driven across a semi-permeable membrane by an osmotic pressure gradient that is generated from a higher concentrate draw solution. FO processes can recover potable water resources from wastewater streams through the flow of pure water from a lower concen-trated feed solution towards higher concentrated draw solutions leaving behind pollutants, impurities, and salts in the semi-permeable membrane. This paper assesses the design, build and testing of a laboratory scaled Feed Forward Osmosis (FFO) system for treating river water collected from the River Medway, Kent, England. The FO process was a highly effective form of river water treatment and able to treat the River Water with high rejection rates of solutes (>90%). Experimental results showed that the FFO system can achieve a better performance when the molarity of the draw solution is higher. The average solute rejection rate of the FO membrane for both inorganic and organic compounds was 94.83 %. Moreover, the operation of the forward osmosis membrane illustrated that it has a lower fouling propensity and higher solute rejection ca-pabilities. The pilot scaled FFO system has the ability for greater salt rejection and lower electronic conductivity levels which resulted from the successful desalination of river water. A sodium chloride (NaCl) or saltwater draw solution performed posi-tively in inducing higher osmotic pressures with a substantial effect of lower energy requirements for the system. Lower en-ergy consumptions of the FFO system allow similar water treatment possibilities with energy savings potential. The FFO system showed to be an environmentally viable and economically feasible river water treatment technology
Recommended from our members
On the microphysical effects of observed cloud edge charging
Liquid layer clouds are abundant globally. Lacking strong convection, they do not become electrified by the usual thunderstorm mechanisms of collisional electrification between hydrometeors of different phases. Instead, the background global circuit current flow in fair weather is largely unaffected by the layer cloud’s presence, and, if the layer cloud is extensive horizontally, the vertical
fair weather conduction current passes through the cloud. A consequence of the vertical current flow is that, at the cloud-air boundary where there is a conductivity transition and droplets form or evaporate, droplet charging occurs. Charge can affect both droplet evaporation and droplet-droplet collisions. Using new radiosonde instrumentation, the charge observed at layer cloud edges is evaluated for both these microphysical droplet processes. This shows that the charging is more likely to affect collision processes than activation, for small droplets. Enhancing the collection efficiency of small droplets modifies their evolution and propagates through the size distribution to shorten the autoconversion timescale to rain drops, and the cloud radiative properties. Because the conduction current density is influenced by both external (e.g. solar modulation of high energy particles) and internal (e.g. ENSO) factors, current flow leading to layer cloud edge charging provides a possible route for expressing solar influences on the climate system and a teleconnection mechanism for communicating internal climate variability
Sustained expression of microRNA-155 in hematopoietic stem cells causes a myeloproliferative disorder
Mammalian microRNAs are emerging as key regulators of the development and function of the immune system. Here, we report a strong but transient induction of miR-155 in mouse bone marrow after injection of bacterial lipopolysaccharide (LPS) correlated with granulocyte/monocyte (GM) expansion. Demonstrating the sufficiency of miR-155 to drive GM expansion, enforced expression in mouse bone marrow cells caused GM proliferation in a manner reminiscent of LPS treatment. However, the miR-155–induced GM populations displayed pathological features characteristic of myeloid neoplasia. Of possible relevance to human disease, miR-155 was found to be overexpressed in the bone marrow of patients with certain subtypes of acute myeloid leukemia (AML). Furthermore, miR-155 repressed a subset of genes implicated in hematopoietic development and disease. These data implicate miR-155 as a contributor to physiological GM expansion during inflammation and to certain pathological features associated with AML, emphasizing the importance of proper miR-155 regulation in developing myeloid cells during times of inflammatory stress
Assessment of human influenza pandemic scenarios in Europe
The response to the emergence of the 2009 influenza A(H1N1) pandemic was the result of a decade of pandemic planning, largely centred on the threat of an avian influenza A(H5N1) pandemic. Based on a literature review, this study aims to define a set of new pandemic scenarios that could be used in case of a future influenza pandemic. A total of 338 documents were identified using a searching strategy based on seven combinations of keywords. Eighty-three of these documents provided useful information on the 13 virus-related and health-system-related parameters initially considered for describing scenarios. Among these, four parameters were finally selected (clinical attack rate, case fatality rate, hospital admission rate, and intensive care admission rate) and four different levels of severity for each of them were set. The definition of six most likely scenarios results from the combination of four different levels of severity of the four final parameters (256 possible scenarios). Although it has some limitations, this approach allows for more flexible scenarios and hence it is far from the classic scenarios structure used for pandemic plans until 2009
Target the fence-sitters
Past waves of vaccine rejection in industrialized nations have a lot to teach us about preventing future ones
Non perturbative renormalization group potentials and quintessence
New solutions to the non perturbative renormalization group equation for the
effective action of a scalar field theory in the Local Potential Approximation
having the exponential form are found. This result could be
relevant for those quintessence phenomenological models where this kind of
potentials are already used, giving them a solid field theoretical derivation.
Other non perturbative solutions, that could also be considered for the
quintessence scenario, are also found. Apart from this particular cosmological
application, these results could be relevant for other models where scalar
fields are involved, in particular for the scalar sector of the standard model.Comment: 4 pages. Corrected typo
Indistinguishable photons from a diode
We generate indistinguishable photons from a semiconductor diode containing a
InAs/GaAs quantum dot. Using an all-electrical technique to populate and
control a single-photon emitting state we filter-out dephasing by
Stark-shifting the emission energy on timescales below the dephasing time of
the state. Mixing consecutive photons on a beam-splitter we observe two-photon
interference with a visibility of 64%
Crossover scaling from classical to nonclassical critical behavior
We study the crossover between classical and nonclassical critical behaviors.
The critical crossover limit is driven by the Ginzburg number G. The
corresponding scaling functions are universal with respect to any possible
microscopic mechanism which can vary G, such as changing the range or the
strength of the interactions. The critical crossover describes the unique flow
from the unstable Gaussian to the stable nonclassical fixed point. The scaling
functions are related to the continuum renormalization-group functions. We show
these features explicitly in the large-N limit of the O(N) phi^4 model. We also
show that the effective susceptibility exponent is nonmonotonic in the
low-temperature phase of the three-dimensional Ising model.Comment: 5 pages, final version to appear in Phys. Rev.
- …