Selective production of phenolic monomer via catalytic depolymerization of lignin over cobalt-nickel-zirconium dioxide catalyst

The utilization of lignin, an abundant and renewable bio-aromatic source, is of significant importance. In this study, lignin oxidation was examined at different temperatures with zirconium oxide (ZrO2)-supported nickel (Ni), cobalt (Co) and bimetallic Ni-Co metal catalysts under different solvents and oxygen pressure. Non-catalytic oxidation reaction produced maximum bio-oil (35.3 wt%), while catalytic oxidation significantly increased the bio-oil yield. The bimetallic catalyst Ni-Co/ZrO2 produced the highest bio-oil yield (67.4 wt%) compared to the monometallic catalyst Ni/ZrO2 (59.3 wt%) and Co/ZrO2 (54.0 wt%). The selectively higher percentage of vanillin, 2-methoxy phenol, acetovanillone, acetosyringone and vanillic acid compounds are found in the catalytic bio-oil. Moreover, it has been observed that the bimetallic Co-Ni/ZrO2 produced a higher amount of vanillin (43.7% and 13.30 wt%) compound. These results demonstrate that the bimetallic Ni-Co/ZrO2 catalyst promotes the selective cleavage of the ether β-O-4 bond in lignin, leading to a higher yield of phenolic monomer compounds.

Mechanistic understanding of perfluorooctane sulfonate (PFOS) sorption by biochars

Biochar has recently emerged as a cost-effective solution to combat per- and polyfluoroalkyl substances (PFAS) pollution in water, but mechanistic understanding of which physicochemical properties of biochars dictate PFAS sorptive removal from water remains elusive. Herein, 15 biochars were pyrolyzed from five feedstocks (corn, Douglas fir, eucalyptus, poplar, and switchgrass) at three pyrolysis temperatures (500, 700, and 900 °C) to investigate their removal efficiencies and mechanisms of perfluorooctane sulfonate (PFOS) from water. A commercial biochar was also included for comparison. Biochar physiochemical properties, including elemental composition, pH, specific surface area (SSA), pore structure, hydrophobicity, surface charge, surface functional groups, and crystalline structure were systematically characterized. Batch sorption data showed that the Douglas fir 900 biochar (Douglas fir and 900 are the feedstock type and pyrolysis temperature, respectively; this naming rule applies to other biochars), poplar 900 biochar, and commercial biochar can remove over 95% of PFOS from water. Structural equation model (SEM) was used to elucidate which biochar properties affect PFOS sorption. Interestingly, biochar pore diameter was identified as the most critical factor controlling PFOS removal, but pore diameter/pore volume ratio, SSA, pyrolysis temperature, hydrophobicity, and elemental composition all played variable roles. Hypothetically, biochars with small pore diameters and large pore volumes had a narrow yet deep pore structure that traps PFOS molecules inside once already sorbed, resulting in an enhanced PFOS sorption. Biochars with small pore diameter, low nitrogen content, and high pyrolysis temperature were also favorable for enhanced PFOS sorption. Our findings advance the knowledge of using biochars with optimized properties to remove PFOS and possibly other similar PFAS compounds from water.

Unraveling hidden rules behind the wet-to-dry transition of bubble array by glass-box physics rule learner

A liquid–gas foam, here called bubble array, is a ubiquitous phenomenon widely observed in daily lives, food, pharmaceutical and cosmetic products, and even bio- and nano-technologies. This intriguing phenomenon has been often studied in a well-controlled environment in laboratories, computations, or analytical models. Still, real-world bubble undergoes complex nonlinear transitions from wet to dry conditions, which are hard to describe by unified rules as a whole. Here, we show that a few early-phase snapshots of bubble array can be learned by a glass-box physics rule learner (GPRL) leading to prediction rules of future bubble array. Unlike the black-box machine learning approach, the glass-box approach seeks to unravel expressive rules of the phenomenon that can evolve. Without known principles, GPRL identifies plausible rules of bubble prediction with an elongated bubble array data that transitions from wet to dry states. Then, the best-so-far GPRL-identified rule is applied to an independent circular bubble array, demonstrating the potential generality of the rule. We explain how GPRL uses the spatio-temporal convolved information of early bubbles to mimic the scientist’s perception of bubble sides, shapes, and inter-bubble influences. This research will help combine foam physics and machine learning to better understand and control bubbles.

Low temperature CO oxidation by doped cerium oxide electrospun fibers

We investigated CO oxidation behavior of doped cerium oxide fibers. Electrospinning technique was used to fabricate the inorganic fibers after burning off polymer component at 600 °C in air. Cu, Ni, Co, Mn, Fe, and La were doped at 10 and 30 mol% by dissolving metal salts into the polymeric electrospinning solution. 10 mol% Cu-doped ceria fiber showed excellent catalytic activity for low temperature CO oxidation with 50% CO conversion at just 52 °C. This 10 mol% Cu-doped sample showed unexpected regeneration behavior under simple ambient air annealing at 400 °C. From the CO oxidation behavior of the 12 samples, we conclude that absolute oxygen vacancy concentration estimated by Raman spectroscopy is not a good indicator for low temperature CO oxidation catalysts unless extra care is taken such that the Raman signal reflects oxide surface status. The experimental trend over the six dopants showed limited agreement with theoretically calculated oxygen vacancy formation energy in the literature.

Metal Nanoparticle Exsolution on a Perovskite Stannate Support with High Electrical Conductivity

In situ exsolution of metal nanoparticles (NPs) is emerging as an alternative technique to deliver thermally stable and evenly dispersed metal NPs, which exhibit excellent adhesion with conducting perovskite oxide supports. Here we provide the first demonstration that Ni metal NPs with high areal density (∼175 μm^-2) and fine size (∼38.65 nm) are exsolved from an A-site-deficient perovskite stannate support (La_0.2Ba_0.7Sn_0.9Ni_0.1O_3-δ (LBSNO)). The NPs are strongly anchored and impart coking resistance, and the Ni-exsolved stannates show exceptionally high electrical conductivity (∼700 S·cm^-1). The excellent conductivity is attributed to conduction between delocalized Sn 5s orbitals along with structural improvement toward ABO₃ stoichiometry in the stannate support. We also reveal that experimental conditions with strong interaction must be optimized to obtain Ni exsolution without degrading the perovskite stannate framework. Our finding suggests a unique process to induce the formation of metal NPs embedded in stannate with excellent electrical properties.

Evidence and Model for Strain-Driven Release of Metal Nanocatalysts from Perovskites during Exsolution

The evolution of the surface morphology during exsolution of Ni from the perovskite La0.4Sr0.4Ti0.97Ni0.03O3-δ under reducing conditions was determined using atomic force microscopy. The exsolution process was found to initially induce the formation of a 20-30 nm deep pit on the oxide surface followed by the emergence of a Ni particle at the bottom of the pit. Continued emergence of the particle results in it nearly filling the pit, producing a unique structure in which the Ni particle is socketed into the oxide surface. We also show that this morphological evolution can be explained using a simple energy-based model that accounts for the interplay between the surface free energy and the strain energy induced by the included metal nucleate. The unique socketed structure results in strong anchorage between the exsolved particles and the oxide host lattice, which imparts both high thermal stability and unique catalytic activity.

Nano-socketed nickel particles with enhanced coking resistance grown in situ by redox exsolution

Metal particles supported on oxide surfaces are used as catalysts for a wide variety of processes in the chemical and energy conversion industries. For catalytic applications, metal particles are generally formed on an oxide support by physical or chemical deposition, or less commonly by exsolution from it. Although fundamentally different, both methods might be assumed to produce morphologically and functionally similar particles. Here we show that unlike nickel particles deposited on perovskite oxides, exsolved analogues are socketed into the parent perovskite, leading to enhanced stability and a significant decrease in the propensity for hydrocarbon coking, indicative of a stronger metal-oxide interface. In addition, we reveal key surface effects and defect interactions critical for future design of exsolution-based perovskite materials for catalytic and other functionalities. This study provides a new dimension for tailoring particle-substrate interactions in the context of increasing interest for emergent interfacial phenomena.

Surface modification of La(0.8)Sr(0.2)CrO(3-δ)-YSZ dual-phase membranes for syngas production

Oxygen permeation fluxes were studied in Mixed Ionic and Electronic Conducting (MIEC) membranes based on composites of 40 vol% La(0.8)Sr(0.2)CrO3 (LSCr) and 60 vol% yttria-stabilized zirconia (YSZ), using ambient air and flowing CO to establish a P(O2) gradient. The ambipolar conductivity of the dense LSCr-YSZ composite was determined for membranes with dense layers that were 115 μm and 650 μm thick. Other parts of the investigation focused on how modifications to the surface on the CO side affected the fluxes. Using a porous LSCr-YSZ composite on the surface as the base case, oxygen fluxes were shown to increase dramatically upon addition of 5 wt% CeO2 as a catalyst and an additional increase was observed with 1 wt% Pt. Changes in the structure of the porous composite LSCr-YSZ surface to improve connectivity of the YSZ phase also led to large increases in the oxygen fluxes.

Electrochemical behavior of thin-film Sm-doped ceria: insights from the point-contact configuration

The electrochemical behavior of chemical vapor deposition (CVD) grown porous films of Sm-doped ceria (SDC) for hydrogen oxidation has been evaluated by impedance spectroscopy using a point contact geometry at a temperature of 650 °C.

Thermoelectric characteristics of the p-type (Bi, Sb)2Te3 nanocomposites processed with silicon nanodispersion

The p-type (Bi0.2Sb0.8)2Te3 powders were mechanically alloyed and hot pressed at 500 degrees C for 30 minutes with dispersion of Si nanopowders up to 3 vol%. The thermal conductivity of the (Bi0.2Sb0.8)2Te3 nanocomposite was substantially reduced with dispersion of 0.3-3 vol% Si nanopowders due to the enhanced phonon scattering. The maximum dimensionless figure-of-merit of 1.32 at 75 degrees C was obtained for the (Bi0.2Sb0.8)2Te3 nanocomposite dispersed with 1 vol% Si nanopowders, compared to 1.08 of the specimen without Si nanopowder dispersion.

Design of an ultra-miniaturized electron optical microcolumn with sub-5 nm very high resolution

The achievement of a microminiaturized electrostatic electron optical column with very-high-resolution probe beam is an important challenge in the fields of electron beam lithography, metrology, and inspection for semiconductor and/or display devices. In this study, we propose an ultra-miniaturized, very-high-resolution electron optical microcolumn that can be assembled more easily compared to previous structures. The design mitigates the complexity of conventional manufacturing processes by eliminating the einzel lens without affecting the resolution performance. According to our numerical simulation results, the proposed ultra-miniaturized electron optical microcolumn produces superior performance with respect to probe beam size and deflection field size as compared to previously published results. A very high, sub-5-nm-resolution probe beam size and a deflection field size larger than 60 μm are achievable at the electron energy of 1 keV and a working distance of 1mm by inserting a focusing electrode and removing the einzel lens.

Low energy microcolumn for large field view inspection

Since the development of microcolumn system, it attracted much attention because multiple microcolumns can be assembled into arrayed form, which is expected to generate multiple electron beams and overcome the disadvantage of electron beam inspection equipments, low throughput. However, it is not easy to apply a microcolumn to the practical inspection or testing equipment since its scanning area is too small. Even if the arrayed operation using multiple microcolumns can overcome this limit, it requires complicated supporting systems and related technologies to operate a number of microcolumns simultaneously. Therefore, we tried to modify microcolumn design itself so that it can have a large field of view. In this work, two kinds of modified columns will be suggested and the preliminary results showing their performance of scanning large area will be discussed.

Effect of Saliva Contamination on the Microshear Bond Strength of One-step Self-etching Adhesive Systems to Dentin

Saliva contamination significantly affects the bond strength of one-step self-etching adhesive systems to dentin; therefore, saliva contamination must be avoided when using these systems.

Androgen receptor: structural domains and functional dynamics after ligand-receptor interaction

Androgens are C-19 steroids secreted primarily from the testes and adrenals that play a critical role in reproduction. Reproductive functions of androgens are mediated through coordination of diverse physiological processes ranging from brain functions to specific cell proliferation and apoptosis. At the molecular level, most of these regulatory influences are exerted by altered expression of appropriate genes by the androgen receptor (AR), a member of the nuclear receptor (NR) superfamily. The unliganded AR is a cytoplasmic protein and, upon ligand binding, it translocates into the nucleus. Thereafter, in conjunction with other transcription factors and coactivators, the AR influences transcription of target genes through a multistep process that includes its clustering in a subnuclear compartment. Here, we describe the genomic organization of the AR, the role of individual structural domains in specific AR function, and the influence of agonistic/antagonistic ligands in the intracellular movement of the receptor. We also show that the AR is capable of undergoing multiple rounds of nucleocytoplasmic recycling after ligand binding and dissociation. Xenobiotic ligands, considered as selective androgen receptor modulators (SARMs), can modulate AR activity by inhibiting either its nuclear translocation or its subnuclear clustering and subsequent transactivation function.

Effect of Nd:YAG laser irradiation on the apical leakage of obturated root canals: an electrochemical study

AIM

The purpose of this laboratory study was to evaluate the effect of Nd:YAG laser irradiation on the apical leakage of obturated root canals using an electrochemical method.

METHODOLOGY

Forty extracted single-rooted teeth were selected and the anatomic crown of each tooth was removed. The specimens were randomly divided into four groups. In group 1, the root canals were prepared with K-files and irradiated with Nd:YAG laser (5 W, 20 Hz) via a 300 microns optical fibre. Then the root canals were obturated with laterally condensed gutta-percha and Pulp Canal Sealer EWT. In group 2, the root canals were treated with the same method as those of group 1 but without laser irradiation. In group 3, the root canals were prepared with ProFiles, laser irradiated and then obturated with vertically condensed gutta-percha and Pulp Canal Sealer EWT. In group 4, the root canals were treated with the same method as those of group 3 but without laser irradiation. The electric resistance between standard and experimental electrodes in the canals was measured over a period of 10 days.

RESULTS

At 2 h, groups 1 and 3 irradiated with laser had significantly less apical leakage than group 2 (P < 0.05). After 10 days, group 4 had the highest leakage, followed by groups 2, 1 and 3; the differences between the groups was statistically significant (P < 0.05).

CONCLUSIONS

Laser irradiation following root canal preparation reduced apical leakage following root canal obturation.

Steroid sulfation by expressed human cytosolic sulfotransferases

The human cytosolic sulfotransferases (STs), dehydroepiandrosterone sulfotransferase (DHEA-ST) and the phenol-sulfating form of phenol sulfotransferase, (P-PST), have been expressed in bacteria and used to investigate the ability of the cloned enzymes to conjugate steroids and related compounds. DHEA-ST was capable of sulfating all of the 3-hydroxysteroids, testosterone and estrogens tested as substrates. The 3-hydroxysteroids, androsterone, epiandrosterone and androstenediol, were conjugated at 50-60% of the rate of DHEA. Of the steroids tested, P-PST was capable of conjugating only the estrogens. The catechol estrogens, 2-hydroxyestradiol, 4-hydroxyestradiol and 4-hydroxyestrone, and compounds with estrogenic activity such as 17 alpha-ethynyl-estradiol and trans-4-hydroxytamoxifen, were also tested as substrates. DHEA-ST showed little or no sulfation activity with these compounds; however, all of these compounds were sulfated by P-PST. These results indicate that the expressed human STs are valuable in analyzing the overlapping substrate specificities of these enzymes and that P-PST may have an important role in the metabolism of estrogens and estrogenic compounds in human tissues.