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2D-NMR characterization of higher substituted oligosaccharides isolated from enzymatic wheat flour arabinoxylan hydrolysates
No full textArabinoxylans (AXs) play a substantial role in the cell walls of cereals, contributing to their structural integrity and stability. The physicochemical and physiological properties of AX structures vary depending on the degree and pattern of substitution. AX structures are based on a linear b-(1→4)-linked D -xylopyranose backbone, being partially substituted with a-L-arabinofuranose in O2 and/or O3 positions of the xylopyranose units. Alkaline-extracted wheat flour AX were hydrolyzed with endo-b-1,4-xylanases of glycoside hydrolase (GH) families 10 or 11. The resulting arabinoxylooligosaccharides (AXOS) were isolated and purified using various chromatographic techniques, including gel permeation chromatography, semi-preparative hydrophilic interaction chromatography, and high performance anion exchange chromatography. The isolated, purified
compounds were characterized by their monosaccharide composition, molecular weight, and monomer binding positions via one- and twodimensional NMR experiments. In addition to smaller AXOS, higher-substituted oligosaccharides with consecutive mono- and disubstituted xylose residues were identified in the hydrolysates, proving that GH10 and GH11 endo-xylanases can cleave more densely substituted regions of wheat AX, in which disubstitution is preferred. These oligosaccharides were obtained in quantities and purities sufficient for their use as standard compounds. We report complete NMR data sets for the four most complex AXOS (A 2+3 XA 2+3 XX, A2+3 A2+3 XX, XA3 A 2+3 XX, A 3 A2 +3 XX) for the first time and also provide a complete NMR library for 17 (A)XOS that were either isolated here or commercially availabl
Surface morphology control of the Cassie–Wenzel transition: An energy landscape perspective
No full textSurface morphology is widely recognized to influence wetting behavior; however, a comprehensive understanding of how specific morphological factors govern the Cassie–Wenzel transition remains incomplete. In this work, building on a bivariate energy-minimization framework, we focus on a key structural design parameter characterizing individual surface defects and systematically investigate its effect—both independently and in conjunction with surface defect density—on three critical aspects of the Cassie–Wenzel transition: wettability, energy barrier, and static friction. Our results demonstrate that this structural design parameter exerts distinct influences on the Cassie–Wenzel transition, depending on the wetting type: in type A, the Wenzel state is energetically favored, while in type B, the Cassie state represents the global energy minimum. These findings reveal that this parameter modulates the stability and reversibility of wetting states, as well as droplet mobility, through nontrivial energy landscapes. Moreover, we uncover a previously unreported non-monotonic dependence of static friction on the morphological factors, which we attribute to a geometric constraint on the contact angle of the transition state. We anticipate that our findings can offer quantitative design guidelines for engineering surfaces with tunable wettability and droplet transport properties
Too human to model: the uncanny valley of large language models in simulating human systems
No full textBetween policy and practice: Emerging lessons on personal carbon trading at the household level
No full textRoom-temperature anomalous Hall effect in graphene in interfacial magnetic proximity to EuO grown by topotactic reduction
No full textWe show that thin layers of EuO, a ferromagnetic insulator, can be achieved by topotactic reduction under titanium of a EuO film deposited on top of a graphene template. The reduction process leads to the formation of a 7-nm-thick EuO smooth layer, without noticeable structural changes in the underlying chemical vapor deposited graphene. The obtained EuO films exhibit ferromagnetism, with a Curie temperature that decreases with the initially deposited EuO layer thickness. By adjusting the thickness of the EuO layer below 7 nm, we promote the formation of EuO at the very graphene interface: the EuO/graphene heterostructure demonstrates the anomalous Hall effect (AHE), which is a fingerprint of proximity-induced spin polarization in graphene. The AHE signal moreover persists above up to 350 K due to a robust super-paramagnetic phase in EuO. This original high-temperature magnetic phase is attributed to magnetic polarons in EuO: we propose that the high strain in our EuO films grown on graphene stabilizes the magnetic polarons up to room temperature. This effect is different from the case of bulk EuO in which polarons vanish in the vicinity of the Curie temperature =69 K
Catalysts for the hydrogen evolution reaction in alkaline medium: Configuring a cooperative mechanism at the Ag-AgS-MoS interface
No full textDesigning electrocatalysts for HER in alkaline conditions to overcome the sluggish kinetics associated with the additional water dissociation step is a recognized challenge in promoting the hydrogen economy. To this end, delicately tuning the atomic-scale structure and surface composition of nanoparticles is a common strategy and, specifically, making use of hybrid structures, can produce synergistic effects that lead to highly active catalysts. Here, we present a core-shell catalyst of Ag@MoS that shows promising results towards the hydrogen evolution reaction (HER) in both 0.5 M HSO and 0.5 M KOH. In this hybrid structure, the MoS shell is strained and defective, and charge transfer occurs between the conductive core and the shell, contributing to the electrocatalytic activity. The shelling process results in a large fraction of AgS in the cores, and adjusting the relative fractions of Ag, AgS, and MoS leads to improved catalytic activity and fast charge-transfer kinetics. We suggest that the enhancement of alkaline HER is associated with a cooperative effect of the interfaces, where the Ag(I) sites in AgS drive the water dissociation step, and the formed hydrogen subsequently recombines on the defective MoS shell. This study demonstrates the benefits of hybrid structures as functional nanomaterials and provides a scheme to activate MoS for HER in alkaline conditions
Phase plates in the transmission electron microscope: operating principles and applications
No full textIn this paper, we review the current state of phase plate imaging in a transmission electron microscope. We focus especially on the hole-free phase plate design, also referred to as the Volta phase plate. We discuss the implementation, operating principles and applications of phase plate imaging. We provide an imaging theory that accounts for inelastic scattering in both the sample and in the hole-free phase plate
Lab Rotation Reports on the determination of Total Water Storage based on monthly gravity field solutions from the GRACE gravity field mission and from GLDAS data
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