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; ^#<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); ^#<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 C₂H_<i>y</i> Formation Mechanism During CH₄ Dissociation on Cu(100) Surface

The possible C₂H_<i>y</i> (<i>y</i> = 2–6) formation reactions (CH_<i>x</i> + CH_<i>z</i> → C₂H_<i>y</i> (<i>y</i> = <i>x</i> + <i>z</i>)) and activated second-order CH_<i>x</i>+1 + CH_<i>z</i>–1 reactions (CH_<i>x</i> + CH_<i>z</i> → CH_<i>x</i>+1 + CH_<i>z</i>–1) during CH₄ dissociation on Cu(100) surface have been investigated by using the density functional theory. Our results show that C₂H_<i>y</i> (<i>y</i> = 2, 4) formation reactions are favorable both kinetically and thermodynamically, compared with the direct dehydrogenation of CH₄ (CH_<i>x</i> → CH_<i>x</i>–1 + H) and second-order CH_<i>x</i>+1 + CH_<i>z</i>–1 reactions. The second-order CH_<i>x</i>+1 + CH_<i>z</i>–1 reactions are less competitive compared with the direct dehydrogenation of CH_<i>x</i>. Both DFT calculations and microkinetic model demonstrate that the reaction CH + CH → C₂H₂ is a major channel to produce C₂H_<i>y</i> at a temperature of 860 °C, followed by CH₃ + CH → C₂H₄. When the H₂ influence is introduced, the major intermediate changes from CH to CH₃ on Cu(100) surface with the increase of H₂ partial pressure, while the coverage difference between CH and CH₃ 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^dipp)­Ln­(CH₂SiMe₃)₂(THF)_<i>n</i> (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 = PhNMe₂, Ln = Lu (<b>1d</b>), <i>n</i> = 1) were synthesized by treatment of the ion-pairs [Ln­(CH₂SiMe₃)₂(THF)_<i>x</i>]­[BPh₄] with equimolar amount of the ligand lithium salts (RNSN^dipp)­Li­(THF)₂ (NSN^dipp = S­(NC₆H₄^<i>i</i>Pr₂-2,6)₂). Addition reaction between lutetium tris­(alkyl)­s, Ln­(Z)₃(THF)_n and NSN^dipp gave the corresponding dialkyl complexes (ZNSN^dipp)­Lu­(Z)₂(THF)_<i>n</i> (Z = CH₂SiMe₃, <i>n</i> = 1 (<b>1e</b>); Z = <i>o</i>-CH₂C₆H₄NMe₂, <i>n</i> = 0 (<b>1f</b>)). Deprotonation of β-imidophosphonamido ligands H–NPN^dipp and H–NPN^Et (NPN^dipp = Ph₂P­(NC₆H₃^<i>i</i>Pr₂-2,6)₂, NPN^Et = PPh₂(NC₆H₃^<i>i</i>Pr₂-2,6)­(NC₆H₄-Et-2)) with Lu­(CH₂SiMe₃)₃(THF)₂ yielded the corresponding dialkyl complexes (NPN^dipp)­Lu­(CH₂SiMe₃)₂(THF) (<b>2</b>) and (NPN^Et)­Lu­(CH₂SiMe₃)₂(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>_s (or pseudo <i>C</i>_s) symmetry with the two alkyl groups arranging on both sides and a coordinated THF against it. Upon activation with [PhMe₂NH]­[B­(C₆F₅)₄] and Al^<i>i</i>Bu₃, 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>_m (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

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

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

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