Sources of 137Cs fluvial export from a forest catchment evaluated by stable carbon and nitrogen isotopic characterization of organic matter

Fluvial export of particulate and dissolved ¹³⁷Cs was investigated to reveal its sources and transfer mechanisms in a broadleaved forest catchment using a continuous collection system. The finest size fraction (<75 µm), consisting of decomposed litter and surface mineral soil, was the dominant fraction in the particulate ¹³⁷Cs load, although the contribution of coarser size fractions increased during high water discharge in 2014. The dissolved ¹³⁷Cs originated from the decomposition of ¹³⁷Cs-contaminated litter. Temporal changes in ¹³⁷Cs distribution in the litter–mineral soil system indicated that the dissolved ¹³⁷Cs load will be moderated in several years, while particulate ¹³⁷Cs load has the potential to continue for a long time.

     

Highly diastereoselective synthesis of tetrahydrobenzofuran derivatives by palladium-catalyzed reaction of propargylic esters with substituted β-dicarbonyl compounds

Reactions of propargylic esters with 2-substituted cyclohexane-1,3-diones and 2-oxocyclohexanecarboxylic esters in the presence of palladium catalyst are described. Substituted tetrahydrobenzofuran derivatives having a quaternary carbon stereocenter were synthesized in a highly diastereoselective manner.     

Micro-channel fabrication by femtosecond laser to arrange neuronal cells on multi-electrode arrays

The surface of a single-crystal germanium wafer was transformed to crystals of germanium fluorides and oxides upon exposure to a vapor of HF and HNO₃ chemical mixture. Structure analysis indicates that the transformation results in a germanate polycrystalline layer consisting of germanium oxide and ammonium fluogermanate with preferential crystal growth orientation in 〈101〉 direction. Local vibrational mode analysis confirms the presence of N–H and Ge–F vibrational modes in addition to Ge–O stretching modes. Energy dispersive studies reveal the presence of hexagonal α-phase GeO₂ crystal clusters and ammonium fluogermanates around these clusters in addition to a surface oxide layer. Electronic band structure as probed by ellipsometry has been associated with the germanium oxide crystals and disorder-induced band tailing effects at the interface of the germanate layer and the bulk Ge wafer. The acid vapor exposure causes Ge surface to emit yellow photoluminescence at room temperature.     

Preparation of isotactic‐rich poly(dimethyl vinylphosphonate) and poly(vinylphosphonic acid) via the anionic polymerization of dimethyl vinylphosphonate

A vinylphosphonate monomer, dimethyl vinylphosphonate (DMVP), has been polymerized by anionic initiators. Anionic polymerization of DMVP with tert‐butyllithium (t‐BuLi) in combination with a Lewis acid, tributylaluminum (n‐Bu₃Al), in toluene proceeded smoothly to give an isotactic‐rich poly(dimethyl vinylphosphonate) (PDMVP) with relatively narrow molecular weight distribution. Although all the PDMVPs were soluble in water, the isotactic‐rich PDMVP was insoluble in acetone and in chloroform which are good solvents for an atactic PDMVP prepared by radical polymerization. The isotactic‐rich PDMVP showed higher thermal property than that of the atactic PDMVP. Moreover, we successfully prepared poly(vinylphosphonic acid) (PVPA) through the hydrolysis of the isotactic‐rich PDMVP, which formed a highly transparent, self‐standing film. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1677–1682, 2010     

Conversion of Molecular Oxygen into a Hydroperoxo Species by Ring-Opening Protonation of a Cyclic η2-Peroxo Intermediate: Characterization of the η2-Peroxo and Hydroperoxo Complexes

A transition metal–hydroperoxo species is formed by the oxygenation of a low-valent rhodium precursor followed by a protonation of the resulting η²-O₂ ligand; the latter process is assisted by an intramolecular hydrogen-bonding interaction (see scheme). This process is the first structural evidence for an effective method for the activation of molecular oxygen as postulated for the cytochrome P-450 system.     

Plasma polymerization of fluoromethanes

Methane and fluoromethanes (CH_nF_4−n, 1 ≤ n ≤ 3) were subjected to an rf glow discharge plasma. All the fluoromethanes (including methane) polymerized in the plasma and formed thin films. The deposition rate of the fluoromethanes depended on their monomer structure: CH₂F₂, of which the F/H ratio is unity, showed the greatest deposition rate. The elimination of H and F atoms as H—F was found to be a key factor for the polymerization of fluoromethanes. The chemical composition of the polymerized film, measured with X-ray photoelectron spectroscopy and glow discharge emission spectroscopy, was also found to be strongly dependent on monomer structure. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2043–2050, 1998     

SEM Observation of Nucleation and Growth of Ag Crystallites on Graphite Substrate

“In-Situ” observation of nucleation and growth of Ag crystallites on graphite substrate by vapour deposition was carried out by scanning electron microscope (SEM). Irradiation of the SEM electron beam onto the substrate surface before and during deposition enhanced Ag nucleation. The density of the Ag crystallites was 10¹⁰/cm² in room temperature condensation, but decreased to 10⁹/cm² in high temperature condensation at 140 °C. When the substrate was heated after room temperature condensation, the density of the Ag crystallites decreased prominently. This means that coalescence of the Ag crystallites takes place as a result of their migration on the substrate.     

Foldings of Difference Sets in Abelian Groups

 In this paper, we show that under some conditions the existence of a difference set in G implies the existence of another difference set with the same parameters in G′, where G and G′ are abelian groups of the same order. This explains why there are more difference sets in abelian groups of low exponent and high rank than in those of high exponent and low rank. Received: September 1, 1997 / Revised: March 24, 1998     

Application of partial least square on quantitative analysis of L-, D-, and DL-tartaric acid by terahertz absorption spectra

Absorption spectra of polycrystalline L-, D-, and DL-tartaric acid have been measured by terahertz time domain spectroscopy (THz-TDS). Different absorption bands are observed for DL-tartaric acid and its enantiomers (L- and D-tartaric acid). This result shows that the THz-TDS can be used for distinguishing between DL-tartaric acid and enantiomers (L- and D-tartaric acid). Moreover, partial least square (PLS) can be found to improve the quantitation of L-tartaric acid in L- and DL-tartaric acid mixture by THz-TDS.