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

Highly <i>Cis</i>-1,4-Selective Living Polymerization of 3‑Methylenehepta-1,6-diene and Its Subsequent Thiol–Ene Reaction: An Efficient Approach to Functionalized Diene-Based Elastomer

Living polymerization of 3-methylenehepta-1,6-diene (MHD) catalyzed by bis­(phosphino)­carbazoleide-ligated yttrium alkyl complex afforded a new product bearing pendant terminal vinyl groups with high stereotacticity (<i>cis</i>-1,4-selectivity up to 98.5%), proved by the NMR (¹H, ¹³C, and 1D ROESY) spectroscopic analyses, which demonstrates overwhelmingly favorable chemoselectivity toward conjugated diene over α-olefin moieties. High <i>cis</i>-1,4 random copolymers of MHD and isoprene could also be obtained with pendant vinyl groups ranging from 10% to 90%. These vinyl groups in every chain unit can be cleanly and quantitatively converted into various functionalities via light-mediated thiol–ene reaction, resulting in homo- and copolymers of various functional butadiene derivatives, which display versatile thermal properties

Legislative Documents

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Binuclear Rare-Earth-Metal Alkyl Complexes Ligated by Phenylene-Bridged β‑Diketiminate Ligands: Synthesis, Characterization, and Catalysis toward Isoprene Polymerization

Deprotonation of <i>m</i>-phenylene-bridged bis­(β-diketiminate) ligands (PBDI^<i>i</i>Pr-H₂ = [2,6-^<i>i</i>Pr₂C₆H₃NHC­(Me)­C­(H)­C­(Me)­N]₂-(<i>m</i>-phenylene); PBDI^Et-H₂ = [2,6-Et₂C₆H₃NHC­(Me)­C­(H)­C­(Me)­N]₂-(<i>m</i>-phenylene); PBDI^Me-H₂ = [2,6-Me₂C₆H₃NHC­(Me)­C­(H)­C­(Me)­N]₂-(<i>m</i>-phenylene)) by rare-earth-metal tris­(alkyls) Ln­(CH₂SiMe₃)₃(THF)₂ (Ln = Y, Lu, Sc) gave a series of rare-earth-metal bis­(alkyl) complexes: PBDI^<i>i</i>Pr-[Y­(CH₂SiMe₃)₂]₂(THF)₂ (<b>1</b>), PBDI^Et-[Ln­(CH₂SiMe₃)₂]₂(THF)_<i>n</i> (<b>2a</b>, Ln = Y, <i>n</i> = 2; <b>2b</b>, Ln = Lu, <i>n</i> = 2; <b>2c</b>, Ln = Sc, <i>n</i> = 1), and PBDI^Me-[Y­(CH₂SiMe₃)₂]₂(THF)₂ (<b>3</b>). All these complexes were fully characterized by NMR spectroscopy, X-ray diffraction, and elemental analyses, adopting binuclear structures with the two rare-earth-metal ions taking <i>trans</i> positions versus the phenyl ring. Complexes <b>1</b>, <b>2a</b>,<b>b</b>, and <b>3</b> coordinate two solvated THF molecules, while the scandium complex <b>2c</b> incorporates only one THF molecule, owing to the steric crowding. Upon activation with 2 equiv of organoborate, the yttrium systems showed higher catalytic activity toward isoprene polymerization in comparison to those based on lutetium, and the scandium system was less active. Addition of aluminum alkyls to the above binary systems accelerated dramatically the polymerization rate irrespective of the central metal type through scavenging impurities in the systems and abstracting the solvated THF molecules in the precursors. The resultant polyisoprene had higher 3,4-regularity (20% vs 5%) as well as higher molecular weights in comparison with the mononuclear systems, which might be attributed to the steric bulky effect of the binuclear systems

Isoprene Polymerization with Iminophosphonamide Rare-Earth-Metal Alkyl Complexes: Influence of Metal Size on the Regio- and Stereoselectivity

The protonolysis reaction of β-iminophosphonamine ligand (NPN^dipp = Ph₂P­(NC₆H₃^<i>i</i>Pr₂-2,6)₂) with one equivalent of rare-earth-metal tris­(alkyl)­s afforded the corresponding bis­(alkyl) complexes NPN^dippLn­(CH₂SiMe₃)₂(THF) (Ln = Sc (<b>1</b>), Lu (<b>2</b>), Y (<b>3</b>), Er (<b>4</b>)). The bis­(4-methylbenzyl) complexes NPN^dippLn­(CH₂Ph-4-Me)₂(THF) (Ln = Nd (<b>5</b>), La (<b>6</b>)) were prepared by treatment of the tris­(4-methylbenzyl) compounds Ln­(CH₂Ph-4-Me)₃(THF)₃ with β-iminophosphonamine ligand. The small-size rare-earth-metal-based complexes <b>1</b>–<b>4</b> upon activation with Al^<i>i</i>Bu₃ and [Ph₃C]­[B­(C₆F₅)₄] showed high 3,4-selectivities up to 98.1% for isoprene polymerization. When the larger size rare-earth-metal-based 4-methylbenzyl complexes <b>5</b> and <b>6</b> were employed instead, moderate 3,4-selectivities were obtained since the opening coordination environment facilitated the 1,4-enchainment (Nd³⁺: 76.1%; La³⁺: 62.9%). Replacing Al^<i>i</i>Bu₃ by AlEt₃, the <b>5</b> and <b>6</b> systems exhibited high activity and excellent <i>trans</i>-1,4 selectivity for both isoprene (96.5%, 0 °C) and butadiene (92.8%, 20 °C) polymerizations

Polymerization of Affinity Ligands on a Surface for Enhanced Ligand Display and Cell Binding

Surfaces functionalized with affinity ligands have been widely studied for applications such as biological separations and cell regulation. While individual ligands can be directly conjugated onto a surface, it is often important to conjugate polyvalent ligands onto the surface to enhance ligand display. This study was aimed at exploring a method for surface functionalization via polymerization of affinity ligands, which was achieved through ligand hybridization with DNA polymers protruding from the surface. The surface with polyvalent ligands was evaluated via aptamer-mediated cell binding. The results show that this surface bound target cells more effectively than a surface directly functionalized with individual ligands in situations with either equal amounts of ligand display or equal amounts of surface reaction sites. Therefore, this study has demonstrated a new strategy for surface functionalization to enhance ligand display and cell binding. This strategy may find broad applications in settings where surface area is limited or the surface of a material does not possess sufficient reaction sites

Programmable Hydrogels for Controlled Cell Catch and Release Using Hybridized Aptamers and Complementary Sequences

The ability to regulate cell–material interactions is important in various applications such as regenerative medicine and cell separation. This study successfully demonstrates that the binding states of cells on a hydrogel surface can be programmed by using hybridized aptamers and triggering complementary sequences (CSs). In the absence of the triggering CSs, the aptamers exhibit a stable, hybridized state in the hydrogel for cell-type-specific catch. In the presence of the triggering CSs, the aptamers are transformed into a new hybridized state that leads to the rapid dissociation of the aptamers from the hydrogel. As a result, the cells are released from the hydrogel. The entire procedure of cell catch and release during the transformation of the aptamers is biocompatible and does not involve any factor destructive to either the cells or the hydrogel. Thus, the programmable hydrogel is regenerable and can be applied to a new round of cell catch and release when needed

Copolymerization of ε‑Caprolactone and l‑Lactide Catalyzed by Multinuclear Aluminum Complexes: An Immortal Approach

A series of aluminum complexes L^aAl₂Me₄ (<b>1</b>), L^b₂Al₄Me₄ (<b>2</b>), and L^cAl₂Me₄ (<b>3</b>) have been prepared from the reaction of AlMe₃ with Salan- and Salen-type ligands (L^aH₂ = [2-OH-3,5-<i>^t</i>Bu₂-C₆H₂CH₂N­(CH₃)]₂-(<i>m</i>-phenylene); L^bH₄ = [2-OH-3,5-<i>^t</i>Bu₂-C₆H₂CH₂NH]₂-(<i>m</i>-phenylene); L^cH₂ = [2-OH-3,5-<i>^t</i>Bu₂-C₆H₂CHN]₂-(<i>m</i>-phenylene)), respectively. All these complexes were characterized by NMR spectroscopy, X-ray diffraction, and elemental analyses, with complexes <b>1</b> and <b>3</b> adopting binuclear structures, while complex <b>2</b> being tetranuclear. In the presence of alcohol, the binuclear complexes <b>1</b> and <b>3</b> catalyzed controlled ring-opening homopolymerizations of both ε-CL and l-LA. In the copolymerization experiments, complexes <b>1</b> and <b>2</b> produced tapered copolymers of ε-CL and l-LA, while complex <b>3</b> was able to provide ε-CL-<i>co</i>-l-LA with tendentially random structure indicated by the average lengths of the caproyl and lactidyl sequences (<i>L</i>_CL = 1.4; <i>L</i>_LA = 2.6). Particularly, addition of excess alcohol into the catalytic system of complex <b>3</b> established the first “immortal” copolymerization of ε-CL/l-LA, which accelerated the polymerization rates of both monomers and, thus, afforded random copolymers with predictable molecular weights and narrow molecular weight distributions

Highly 3,4-Selective Living Polymerization of Isoprene and Copolymerization with ε‑Caprolactone by an Amidino N‑Heterocyclic Carbene Ligated Lutetium Bis(alkyl) Complex

The amidino-modified N-heterocyclic carbene ligated lutetium bis­(alkyl) complex <b>1</b>, (Am-NHC)­Lu­(CH₂SiMe₃)₂, was synthesized by treatment of (AmH-NHC-H)Br ((2,6-^<i>i</i>PrC₆H₃NC­(C₆H₅)­NHCH₂CH₂(NCHCHN­(C₆H₂Me₃-2,4,6)­CH)­Br) with ((trimethylsilyl)­methyl)­lithium (LiCH₂SiMe₃) and lutetium tris­(alkyls) (Lu­(CH₂SiMe₃)₃(THF)₂) via double-deprotonation reactions and characterized by NMR spectroscopy and X-ray diffraction analysis. Under activation of an organoborate, complex <b>1</b> exhibited distinguished catalytic performance for the polymerization of isoprene with respect to high activity, 3,4-regioselectivity (99.3%), and livingness mode. In contrast to the systems reported to date, this system seemed not to be affected obviously by the polymerization temperature (0–80 °C), solvents, monomer-to-initiator ratios (500–5000), and type of organoborate. The resultant polymers have high glass-transition temperatures (38–48 °C) and moderate syndiotacticity (racemic enchainment triad <i>rr</i> 45%, pentad <i>rrrr</i> 20%). In addition, the living lutetium–polyisoprene active species could further initiate the ring-opening polymerization of ε-caprolactone to give selectively the poly­(3,4-isoprene)-<i>b</i>-polycaprolactone block copolymers with controllable molecular weight (from 4.9 × 10⁴ to 10.2 × 10⁴) and narrow polydispersity

Phosphinimino-amino Magnesium Complexes: Synthesis and Catalysis of Heteroselective ROP of <i>rac</i>-Lactide

Alkane elimination reactions of phosphinimino-amine ligands HL^1–8 ((2,6-Me₂-C₆H₃NH)­C­(Ph)CHPPh₂(NAr) (Ar = C₆H₅ (HL¹); 2,6-Me₂-C₆H₃ (HL²); 2,6-Et₂-C₆H₃ (HL³); 2,6-^<i>i</i>Pr₂-C₆H₃ (HL⁴); 2-OMe-C₆H₄ (HL⁵); 2-Cl-C₆H₄ (HL⁶); 3-CF₃-C₆H₄ (HL⁷); 4-MeO-C₆H₄ (HL⁸)) with Mg^<i>n</i>Bu₂, respectively, afforded a series of phosphinimino-amine-based complexes L^1–8Mg^<i>n</i>Bu­(THF) (<b>1</b>–<b>8</b>) by releasing butane. Complexes <b>1</b>–<b>8</b> are phosphinimino-amine-ligated THF-solvated mono­(alkyl)­s, among which <b>1</b>–<b>4</b> adopt twisted tetrahedral geometries, whereas <b>5</b> contains a trigonal bipyramido geometry core. Complexes <b>1</b>–<b>8</b> all display high activity for the ring-opening polymerization of <i>rac</i>-lactide. The molecular weights of the resulting PLA are close to the theoretic values, and the molecular weight distributions are narrow. Moreover, these complexes show medium to high heteroselectivity, which, interestingly, increases with the decrease of the ligand steric hindrance; thus, complex <b>1</b>, bearing a less bulky ligand, exhibits a heteroselectivity of <i>P</i>_r = 0.98, the highest value of a magnesium-based initiator achieved to date. The kinetics study showed that the polymerization rate is first-order dependent on both monomer and initiator concentrations, and the overall rate equation is −d­[LA]/d<i>t</i> = 3.78 M^–1 s^–1 [LA]­[Mg]