4,089 research outputs found
CO2 storage properties of nanostructured carbons by a microwave plasma reactor
Nanostructured carbon was successfully produced by methane cracking in a relatively low-energy cold plasma reactor designed in-house. A followed thermal treatment was carried out to further enhance its porosity. The modified plasma carbon was then employed for CO2 adsorption at 25°C. The as-synthesized plasma carbon and the modified carbon were characterized by BET surface area/pore size analyzer, Raman spectra, and transmission electron microscopy (TEM). The results show thermal modification pronouncedly improves BET surface area and porosity of PC due to opening up of accessible micro-/mesopores in the graphitic structure and by the removal of amorphous carbons around the graphite surface. The modified PC displays a higher adsorption capacity at 25°C than that of the commercial activated carbon reported. The low hydrogen storage capacity of the modified PC indicates that it can be considered for CO2 removal in syngas
Channel-Recurrent Autoencoding for Image Modeling
Despite recent successes in synthesizing faces and bedrooms, existing
generative models struggle to capture more complex image types, potentially due
to the oversimplification of their latent space constructions. To tackle this
issue, building on Variational Autoencoders (VAEs), we integrate recurrent
connections across channels to both inference and generation steps, allowing
the high-level features to be captured in global-to-local, coarse-to-fine
manners. Combined with adversarial loss, our channel-recurrent VAE-GAN
(crVAE-GAN) outperforms VAE-GAN in generating a diverse spectrum of high
resolution images while maintaining the same level of computational efficacy.
Our model produces interpretable and expressive latent representations to
benefit downstream tasks such as image completion. Moreover, we propose two
novel regularizations, namely the KL objective weighting scheme over time steps
and mutual information maximization between transformed latent variables and
the outputs, to enhance the training.Comment: Code: https://github.com/WendyShang/crVAE. Supplementary Materials:
http://www-personal.umich.edu/~shangw/wacv18_supplementary_material.pd
Charged BTZ-like black hole solutions and the diffusivity-butterfly velocity relation
We show that there exists a class of charged BTZ-like black hole solutions in
Lifshitz spacetime with a hyperscaling violating factor. The charged BTZ is
characterized by a charge-dependent logarithmic term in the metric function. As
concrete examples, we give five such charged BTZ-like black hole solutions and
the standard charged BTZ metric can be regarded as a special instance of them.
In order to check the recent proposed universal relations between diffusivity
and the butterfly velocity, we first compute the diffusion constants of the
standard charged BTZ black holes and then extend our calculation to arbitrary
dimension , exponents and . Remarkably, the case and
is a very special in that the charge diffusion is a constant and
the energy diffusion might be ill-defined, but diverges. We
also compute the diffusion constants for the case that the DC conductivity is
finite but in the absence of momentum relaxation.Comment: 30 pages, 2 figure
Design of magnetic spirals in layered perovskites: extending the stability range far beyond room temperature
In insulating materials with ordered magnetic spiral phases, ferroelectricity
can emerge due to the breaking of inversion symmetry. This property is of both
fundamental and practical interest, in particular with a view to exploiting it
in low-power electronic devices. Advances towards technological applications
have been hindered, however, by the relatively low ordering temperatures
of most magnetic spiral phases, which rarely exceed 100 K.
We have recently established that the ordering temperature of a magnetic spiral
can be increased up to 310 K by the introduction of chemical disorder. Here we
explore the design space opened up by this novel mechanism by combining it with
a targeted lattice control of some magnetic interactions. In Cu-Fe layered
perovskites we obtain values close to 400 K, comfortably
far from room temperature and almost 100 K higher than using chemical disorder
alone. Moreover, we reveal a linear, universal relationship between the
spiral's wave vector and the onset temperature of the spiral phase. This linear
law ends at a paramagnetic-collinear-spiral triple point, which defines the
highest spiral ordering temperature that can be achieved in this class of
materials. Based on these findings, we propose a general set of rules for
designing magnetic spirals in layered perovskites using external pressure,
chemical substitutions and/or epitaxial strain, which should guide future
efforts to engineer magnetic spiral phases with ordering temperatures suitable
for technological applications.Comment: 5 figures, 35 pages, to be appeared on Science Advanc
Copper(II) Can Kinetically Trap Arctic and Italian Amyloid‑β40 as Toxic Oligomers, Mimicking Cu(II) Binding to Wild-Type Amyloid‑β42: Implications for Familial Alzheimer’s Disease
The self-association of amyloid-β (Aβ) peptide into neurotoxic oligomers is believed to be central to Alzheimer’s disease (AD). Copper is known to impact Aβ assembly, while disrupted copper homeostasis impacts phenotype in Alzheimer’s models. Here we show the presence of substoichiometric Cu(II) has very different impacts on the assembly of Aβ40 and Aβ42 isoforms. Globally fitting microscopic rate constants for fibril assembly indicates copper will accelerate fibril formation of Aβ40 by increasing primary nucleation, while seeding experiments confirm that elongation and secondary nucleation rates are unaffected by Cu(II). In marked contrast, Cu(II) traps Aβ42 as prefibrillar oligomers and curvilinear protofibrils. Remarkably, the Cu(II) addition to preformed Aβ42 fibrils causes the disassembly of fibrils back to protofibrils and oligomers. The very different behaviors of the two Aβ isoforms are centered around differences in their fibril structures, as highlighted by studies of C-terminally amidated Aβ42. Arctic and Italian familiar mutations also support a key role for fibril structure in the interplay of Cu(II) with Aβ40/42 isoforms. The Cu(II) dependent switch in behavior between nonpathogenic Aβ40 wild-type and Aβ40 Arctic or Italian mutants suggests heightened neurotoxicity may be linked to the impact of physiological Cu(II), which traps these familial mutants as oligomers and curvilinear protofibrils, which cause membrane permeability and Ca(II) cellular influx
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