Environmental changes in Syowa Station area of Antarctica during the last 2300 years inferred from organic components in lake sediment cores

rganic components in sediment cores from Namazu Ike(lake)(length 40cm) and O-ike(lake)(length 32cm) from Syowa Station area, Antarctica were studied to clarify their features in relation to paleoenvironmental changes, together with carbon-14 dating by Tandetron accelerator mass spectrometry. Namazu Ike sediment core was mainly composed of algal(mainly cyanobacteria) and aquatic moss debris, whereas O-ike sediment core was comprised of coarse and fine sands with the influence of algal(mainly cyanobacteria) debris. The ages of core bottoms of Namazu Ike and O-ike were estimated to be 1550 and 2330 years before present(yBP), respectively. The sedimentation rates of Namazu Ike and O-ike were calculated to be 30 and 59 years/cm, respectively. Very high total organic carbon(TOC) contents(average 24.5%) of Namazu Ike revealed that the sediment core was mainly composed of organic matter. Dramatic increase of TOC/total nitrogen ratios at a depth of 25cm in Namazu Ike strongly suggests that aquatic moss increased from 1100yBP to the core top. Changes in n-alkanes, n-alkanoic and n-alkenoic acids, and sterol compositions in the O-ike sediment core, suggest that microbial composition changed considerably, but their source organisms are not clear and further studies are required

Surface Modifier-Free Organic–Inorganic Hybridization To Produce Optically Transparent and Highly Refractive Bulk Materials Composed of Epoxy Resins and ZrO₂ Nanoparticles

Surface modifier-free hybridization of ZrO₂ nanoparticles (NPs) with epoxy-based polymers is demonstrated for the first time to afford highly transparent and refractive bulk materials. This is achieved by a unique and versatile hybridization via the one-pot direct phase transfer of ZrO₂ NPs from water to epoxy monomers without any aggregation followed by curing with anhydride. Three types of representative epoxy monomers, bisphenol A diglycidyl ether (BADGE), 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate (CEL), and 1,3,5-tris­(3-(oxiran-2-yl)­propyl)-1,3,5-triazinane-2,4,6-trione (TEPIC), are used to produce transparent viscous dispersions. The resulting ZrO₂ NPs are thoroughly characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), and solid-state ¹³C CP/MAS NMR measurements. The results from DLS and TEM analyses indicate nanodispersion of ZrO₂ into epoxy monomers as a continuous medium. A surface modification mechanism and the binding fashion during phase transfer are proposed based on the FT-IR and solid-state ¹³C CP/MAS NMR measurements. Epoxy-based hybrid materials with high transparency and refractive index are successfully fabricated by heat curing or polymerizing a mixture of monomers containing epoxy-functionalized ZrO₂ NPs and methylhexahydrophthalic anhydride in the presence of a phosphoric catalyst. The TEM and small-angle X-ray scattering measurements of the hybrids show a nanodispersion of ZrO₂ in the epoxy networks. The refractive index at 594 nm (<i>n</i>₅₉₄) increases up to 1.765 for BADGE-based hybrids, 1.667 for CEL-based hybrids, and 1.693 for TEPIC-based hybrids. Their refractive indices and Abbe’s numbers are quantitatively described by the Lorentz–Lorenz effective medium expansion theory. Their transmissivity is also reasonably explained using Fresnel refraction, Rayleigh scattering, and the Lambert–Beer theories. This surface modifier-free hybridization provides a versatile, fascinating, and promising method for synthesizing a variety of epoxy-based hybrid materials

Controlling the dimension of the quantum resonance in CdTe quantum dot superlattices fabricated via layer-by-layer assembly

Nature Communications. 2020, 11, P.5471