217 research outputs found
Atmospheric tar balls: aged primary droplets from biomass burning?
Atmospheric tar balls are particles of special morphology and composition
that are fairly abundant in the plumes of biomass smoke. These particles
form a specific subset of brown carbon (BrC) which has been shown to play a
significant role in atmospheric shortwave absorption and, by extension, climate
forcing. Here we suggest that tar balls are produced by the direct emission
of liquid tar droplets followed by heat transformation upon biomass burning.
For the first time in atmospheric chemistry we generated tar-ball particles
from liquid tar obtained previously by dry distillation of wood in an
all-glass apparatus in the laboratory with the total exclusion of flame
processes. The particles were perfectly spherical with a mean optical
diameter of 300 nm, refractory, externally mixed, and homogeneous in the
contrast of the transmission electron microscopy (TEM) images.
They lacked any graphene-like microstructure and
exhibited a mean carbon-to-oxygen ratio of 10. All of the observed
characteristics of laboratory-generated particles were very similar to those
reported for atmospheric tar-ball particles in the literature, strongly
supporting our hypothesis regarding the formation mechanism of atmospheric
tar-ball particles
Competitive percolation strategies for network recovery
Restoring operation of critical infrastructure systems after catastrophic
events is an important issue, inspiring work in multiple fields, including
network science, civil engineering, and operations research. We consider the
problem of finding the optimal order of repairing elements in power grids and
similar infrastructure. Most existing methods either only consider system
network structure, potentially ignoring important features, or incorporate
component level details leading to complex optimization problems with limited
scalability. We aim to narrow the gap between the two approaches. Analyzing
realistic recovery strategies, we identify over- and undersupply penalties of
commodities as primary contributions to reconstruction cost, and we demonstrate
traditional network science methods, which maximize the largest connected
component, are cost inefficient. We propose a novel competitive percolation
recovery model accounting for node demand and supply, and network structure.
Our model well approximates realistic recovery strategies, suppressing growth
of the largest connected component through a process analogous to explosive
percolation. Using synthetic power grids, we investigate the effect of network
characteristics on recovery process efficiency. We learn that high structural
redundancy enables reduced total cost and faster recovery, however, requires
more information at each recovery step. We also confirm that decentralized
supply in networks generally benefits recovery efforts.Comment: 14 pages, 6 figure
Synaptic and cellular changes induced by the schizophrenia susceptibility gene G72 are rescued by N-acetylcysteine treatment
Genetic studies have linked the primate-specific gene locus G72 to the development of schizophrenia and bipolar disorder. Transgenic mice carrying the entire gene locus express G72 mRNA in dentate gyrus (DG) and entorhinal cortex, causing altered electrophysiological properties of their connections. These transgenic mice exhibit behavioral alterations related to psychiatric diseases, including cognitive deficits that can be reversed by treatment with N-acetylcysteine, which was also found to be effective in human patients. Here, we show that G72 transgenic mice have larger excitatory synapses with an increased amount of N-methyl-d-aspartate (NMDA) receptors in the molecular layer of DG, compared with wild-type littermates. Furthermore, transgenic animals have lower number of dentate granule cells with a parallel, but an even stronger decrease in the number of excitatory synapses in the molecular layer. Importantly, we also show that treatment with N-acetylcysteine can effectively normalize all these changes in transgenic animals, resulting in a state similar to wild-type mice. Our results show that G72 transcripts induce robust alterations in the glutamatergic system at the synaptic level that can be rescued with N-acetylcysteine treatment
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