15 research outputs found
Inversion using a new low-dimensional representation of complex binary geological media based on a deep neural network
Efficient and high-fidelity prior sampling and inversion for complex
geological media is still a largely unsolved challenge. Here, we use a deep
neural network of the variational autoencoder type to construct a parametric
low-dimensional base model parameterization of complex binary geological media.
For inversion purposes, it has the attractive feature that random draws from an
uncorrelated standard normal distribution yield model realizations with spatial
characteristics that are in agreement with the training set. In comparison with
the most commonly used parametric representations in probabilistic inversion,
we find that our dimensionality reduction (DR) approach outperforms principle
component analysis (PCA), optimization-PCA (OPCA) and discrete cosine transform
(DCT) DR techniques for unconditional geostatistical simulation of a
channelized prior model. For the considered examples, important compression
ratios (200 - 500) are achieved. Given that the construction of our
parameterization requires a training set of several tens of thousands of prior
model realizations, our DR approach is more suited for probabilistic (or
deterministic) inversion than for unconditional (or point-conditioned)
geostatistical simulation. Probabilistic inversions of 2D steady-state and 3D
transient hydraulic tomography data are used to demonstrate the DR-based
inversion. For the 2D case study, the performance is superior compared to
current state-of-the-art multiple-point statistics inversion by sequential
geostatistical resampling (SGR). Inversion results for the 3D application are
also encouraging
Vitexin attenuates lipopolysaccharide-induced acute lung injury by controlling the Nrf2 pathway
<div><p>Background</p><p>A major feature of acute lung injury (ALI) is excessive inflammation in the lung. Vitexin is an active component from medicinal plants which has antioxidant and anti-inflammatory activities. Oxidative stress and inflammation play important roles in the pathophysiological processes in ALI. In the current study, we investigate the effect and potential mechanisms of Vitexin on lipopolysaccharide (LPS)-induced ALI.</p><p>Methods</p><p>ALI was induced by LPS intratracheal instillation in C57BL/6 wild-type mice and Nrf2 gene knocked down (Nrf2-/-) mice. One hour before LPS challenge, Vitexin or vehicle intraperitoneal injection was performed. Bronchoalveolar lavage fluid and lung tissues were examined for lung inflammation and injury at 24 h after LPS challenge.</p><p>Results</p><p>Our animal study’s results showed that LPS-induced recruitment of neutrophils and elevation of proinflammatory cytokine levels were attenuated by Vitexin treatment. Vitexin decreased lung edema and alveolar protein content. Moreover, Vitexin activated nuclear factor erythroid-2-related factor 2 (Nrf2), and increased the activity of its target gene heme oxygenase (HO)-1. The LPS-induced reactive oxygen species were inhibited by Vitexin. In addition, the activation of the nucleotide-binding domain and leucine-rich repeat PYD-containing protein 3 (NLRP3) inflammasome was suppressed by Vitexin. However, these effects of Vitexin were abolished in the Nrf2-/- mice. Our cell studies showed that Vitexin enhanced the expression of Nrf2 and HO-1 activity. Moreover, reactive oxygen species (ROS) and IL-1β productions were reduced in Vitexin-treated cells. However, knockdown of Nrf2 by siRNA in RAW cells reversed the benefit of Vitexin.</p><p>Conclusions</p><p>Vitexin suppresses LPS-induced ALI by controlling Nrf2 pathway.</p></div
Effects of Vitexin on pulmonary histopathological analysis, lung injury score, lung permeability, and lung water content in lipopolysaccharide (LPS)-treated mice.
<p>Representative haematoxylin-eosin staining images of pulmonary section (A): a, control group (wild type (WT) mice treated with sterile phosphate-buffered saline (PBS)+vehicle); b, WT mice treated with PBS+Vitexin; c, nuclear factor erythroid-2-related factor 2 (Nrf2) gene knockout (Nrf2-/-) mice treated with LPS+vehicle; d, WT mice treated with LPS+vehicle; e, WT mice treated with LPS+Vitexin; f, Nrf2-/- mice treated with LPS+Vitexin. All photographs were taken at 100×magnification. Lung injury score (B). Protein concentrations in bronchoalveolar lavage fluid (BALF) (C). Pulmonary wet to dry (W/D) weight ratio (D). Data was expressed as means ± SEM (n = 6–10 per group). * <i>p</i> < 0.05, versus control group; <sup>#</sup><i>p</i> < 0.05, versus LPS+vehicle group; ** <i>p</i> < 0.05, versus LPS+Vitexin treated WT mice.</p
Effects of Vitexin on cell viability (A), the expressions of nuclear factor erythroid-2-related factor 2 (Nrf2) (B), heme oxygenase (HO)-1 activity (C), reactive oxygen species (ROS) levels (D), and interleukin (IL)-1β levels (E) in lipopolysaccharide (LPS)-activated RAW cells.
<p>TBP, TATA box binding protein. Data was expressed as means ± SEM of three independent experiments. * <i>p</i> < 0.05.</p
Effects of Vitexin on nuclear factor erythroid-2-related factor 2 (Nrf2) activity (A), heme oxygenase (HO)-1 activity (B), and the nucleotide-binding domain and leucine-rich repeat PYD-containing protein 3 (NLRP3) inflammasome (C) in lipopolysaccharide (LPS)-treated mice.
<p>Data was expressed as means ± SEM (n = 6–10 per group). * <i>p</i> < 0.05, versus control group (wild type (WT) mice treated with PBS+vehicle); <sup>#</sup><i>p</i> < 0.05, versus LPS+vehicle group; ** <i>p</i> < 0.05, versus LPS+Vitexin treated WT mice. Nrf2-/-, Nrf2 gene knockout mice.</p
Theoretical Insights on the C<sub>2</sub>H<sub><i>y</i></sub> Formation Mechanism During CH<sub>4</sub> Dissociation on Cu(100) Surface
The
possible C<sub>2</sub>H<sub><i>y</i></sub> (<i>y</i> = 2–6) formation reactions (CH<sub><i>x</i></sub> + CH<sub><i>z</i></sub> → C<sub>2</sub>H<sub><i>y</i></sub> (<i>y</i> = <i>x</i> + <i>z</i>)) and activated second-order CH<sub><i>x</i>+1</sub> + CH<sub><i>z</i>–1</sub> reactions
(CH<sub><i>x</i></sub> + CH<sub><i>z</i></sub> → CH<sub><i>x</i>+1</sub> + CH<sub><i>z</i>–1</sub>) during CH<sub>4</sub> dissociation on Cu(100) surface
have been investigated by using the density functional theory. Our
results show that C<sub>2</sub>H<sub><i>y</i></sub> (<i>y</i> = 2, 4) formation reactions are favorable both kinetically
and thermodynamically, compared with the direct dehydrogenation of
CH<sub>4</sub> (CH<sub><i>x</i></sub> → CH<sub><i>x</i>–1</sub> + H) and second-order CH<sub><i>x</i>+1</sub> + CH<sub><i>z</i>–1</sub> reactions. The
second-order CH<sub><i>x</i>+1</sub> + CH<sub><i>z</i>–1</sub> reactions are less competitive compared with the
direct dehydrogenation of CH<sub><i>x</i></sub>. Both DFT
calculations and microkinetic model demonstrate that the reaction
CH + CH → C<sub>2</sub>H<sub>2</sub> is a major channel to
produce C<sub>2</sub>H<sub><i>y</i></sub> at a temperature
of 860 °C, followed by CH<sub>3</sub> + CH → C<sub>2</sub>H<sub>4</sub>. When the H<sub>2</sub> influence is introduced, the
major intermediate changes from CH to CH<sub>3</sub> on Cu(100) surface
with the increase of H<sub>2</sub> partial pressure, while the coverage
difference between CH and CH<sub>3</sub> is not significant. This
means that both species will have a large influence on the graphene
growth mechanism
3,4-Polymerization of Isoprene by Using NSN- and NPN-Ligated Rare Earth Metal Precursors: Switching of Stereo Selectivity and Mechanism
The rare-earth metal complexes bearing
NSN-bidentate β-diimidosulfonate
ligands (RNSN<sup>dipp</sup>)Ln(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(THF)<sub><i>n</i></sub> (R = Ph, Ln = Lu (<b>1a</b>), <i>n</i> = 1, Y (<b>1b</b>), <i>n</i> = 2, Sc (<b>1c</b>), <i>n</i> = 1; R =
PhNMe<sub>2</sub>, Ln = Lu (<b>1d</b>), <i>n</i> =
1) were synthesized by treatment of the ion-pairs [Ln(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(THF)<sub><i>x</i></sub>][BPh<sub>4</sub>] with equimolar amount of the ligand lithium salts (RNSN<sup>dipp</sup>)Li(THF)<sub>2</sub> (NSN<sup>dipp</sup> = S(NC<sub>6</sub>H<sub>4</sub><sup><i>i</i></sup>Pr<sub>2</sub>-2,6)<sub>2</sub>). Addition reaction between lutetium tris(alkyl)s, Ln(Z)<sub>3</sub>(THF)<sub>n</sub> and NSN<sup>dipp</sup> gave the corresponding
dialkyl complexes (ZNSN<sup>dipp</sup>)Lu(Z)<sub>2</sub>(THF)<sub><i>n</i></sub> (Z = CH<sub>2</sub>SiMe<sub>3</sub>, <i>n</i> = 1 (<b>1e</b>); Z = <i>o</i>-CH<sub>2</sub>C<sub>6</sub>H<sub>4</sub>NMe<sub>2</sub>, <i>n</i> = 0
(<b>1f</b>)). Deprotonation of β-imidophosphonamido ligands
H–NPN<sup>dipp</sup> and H–NPN<sup>Et</sup> (NPN<sup>dipp</sup> = Ph<sub>2</sub>P(NC<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>-2,6)<sub>2</sub>, NPN<sup>Et</sup> = PPh<sub>2</sub>(NC<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>-2,6)(NC<sub>6</sub>H<sub>4</sub>-Et-2)) with
Lu(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(THF)<sub>2</sub> yielded
the corresponding dialkyl complexes (NPN<sup>dipp</sup>)Lu(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(THF) (<b>2</b>) and (NPN<sup>Et</sup>)Lu(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(THF) (<b>3</b>). All the complexes had been structurally well-defined,
and <b>1a</b>, <b>1b</b>, <b>1e, 2</b>, and <b>3</b> were further characterized by X-ray diffraction analysis
where the almost planar NSN rare-earth metal unit is <i>C</i><sub>s</sub> (or pseudo <i>C</i><sub>s</sub>) symmetry
with the two alkyl groups arranging on both sides and a coordinated
THF against it. Upon activation with [PhMe<sub>2</sub>NH][B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>] and Al<sup><i>i</i></sup>Bu<sub>3</sub>, all these complexes exhibited high 3,4-regioselectivity
(ranging from 91% to >99%) for the polymerization of isoprene.
Moreover,
the excellent isospecific selectivity up to <i>mmmm</i> >
99% have been achieved with complexes <b>1</b> depending on
the electronics of the sulfur substituents to give crystalline polyisoprene
with the highest <i>T</i><sub>m</sub> (170 °C) reported
to date. The NPN-bidentate β-imidophosphonamide ligated rare-earth
metal complexes provide both high syndio- and iso- 3,4-selectivities
(3,4 > 99%, <i>rr</i> = 66%, <i>mmmm</i> =
96%)
depending on the frameworks, steric environment and geometry of the
ligands. The regio- and stereo- selective mechanisms proceeded in
these systems were explicated by DFT simulation
Electron Counting and a Large Family of Two-Dimensional Semiconductors
In comparison with conventional semiconductors,
most two-dimensional
semiconductor (2DSC) materials are dissimilar in structure and composition.
Herein, we use electron-counting rules to propose a large family of
2DSCs, which all adopt the same structure and are composed of solely
main group elements. Advanced density functional theory calculations
are used to predict a number of novel 2DSCs, and we show that they
span a large range of lattice constants, band gaps, and band edge
states. As a result, they are good candidate materials for heterojunctions.
This family of two-dimensional materials may be instrumental in the
fabrication of 2DSC devices that may rival the currently employed
3D semiconductors
Flow of Preformed Particle Gel through Porous Media: A Numerical Simulation Study Based on the Size Exclusion Theory
After
swelling, preformed particle gel (PPG) can be suspended in
the aqueous phase to plug small pores while flowing through the formation
or deform under large pressure gradients to move further into the
formation, and achieve in-depth profile control. This paper, based
on the size exclusion theory, introduces the concept of the critical
pressure gradient to capture the phenomenon that PPG plugging small
pores can deform and pass, and the concept of the mean number of bridging
particles and mean bridging probability to characterize the bridging
of the PPG inside large pores. On this basis the numerical simulation
model of the PPG flowing through porous media, combined with the numerical
simulation theory, has been established and validated with physical
simulation experiments. The general regularity of the PPG migrating
inside porous media is then studied using the proposed numerical simulation
model
Stereoelectronic Control in Regioselective Carbohydrate Protection
Organotin-mediated regioselective protection has been
extensively
used in organic synthesis for many years. However, the mechanistic
origin of the resulting regioselectivity is still not clear. By the
comparison of the steric and stereoelectronic effects controlling
the geometry of five-membered rings formed from neighboring group
participation, from intramolecular acyl group migration, or from orthoester
transesterification on pyranoside rings, a theory on the pattern resulting
from the reaction with dibutyltin oxide is presented. It is thus suggested
that the regioselectivity of organotin-mediated protection is controlled
by analogous steric and stereoelectronic effects as in neighboring
group participation and acyl group migration, mainly dependent on
the stereoelectronic effects of the pyranoside itself, and not related
to complex stannylene structures. An organotin protection mechanism
is also suggested, emanating from steric and stereoelectronic effects,
nucleophilicity, and organotin acyl migration