Chemical effects on valence→L emissions of lanthanide compounds

Ce Lβ emission spectra of CeF₃ and CeO₂ have been measured with energy resolution of ~ 3 eV by a wave-dispersive spectrometer. The observed Ce Lβ₇ band shows certain difference between the two compounds both in profile and intensity. The chemical effects can be reproduced by a band calculation using WIEN2k, which suggests that the Ce Lβ₇ reflects valence-band structure of compounds, and therefore, is hopeful as a probe of selective X-ray absorption fine structure.     

Multivariate analysis of DSC–XRD simultaneous measurement data: a study of multistage crystalline structure changes in a linear poly(ethylene imine) thin film

A multivariate analytical technique has been applied to the analysis of simultaneous measurement data from differential scanning calorimetry (DSC) and X-ray diffraction (XRD) in order to study thermal changes in crystalline structure of a linear poly(ethylene imine) (LPEI) film. A large number of XRD patterns generated from the simultaneous measurements were subjected to an augmented alternative least-squares (ALS) regression analysis, and the XRD patterns were readily decomposed into chemically independent XRD patterns and their thermal profiles were also obtained at the same time. The decomposed XRD patterns and the profiles were useful in discussing the minute peaks in the DSC. The analytical results revealed the following changes of polymorphisms in detail: An LPEI film prepared by casting an aqueous solution was composed of sesquihydrate and hemihydrate crystals. The sesquihydrate one was lost at an early stage of heating, and the film changed into an amorphous state. Once the sesquihydrate was lost by heating, it was not recovered even when it was cooled back to room temperature. When the sample was heated again, structural changes were found between the hemihydrate and the amorphous components. In this manner, the simultaneous DSC–XRD measurements combined with ALS analysis proved to be powerful for obtaining a better understanding of the thermally induced changes of the crystalline structure in a polymer film. Figure DSC–XRD combined with ALS analysis provides a powerful method for elucidating thermally induced changes of crystalline structure in a polymer film Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Structural analysis of three novel trisaccharides isolated from the fermented beverage of plant extracts

Background  

A fermented beverage of plant extracts was prepared from about fifty kinds of vegetables and fruits. Natural fermentation was carried out mainly by lactic acid bacteria (Leuconostoc spp.) and yeast (Zygosaccharomyces spp. and Pichia spp.). We have previously examined the preparation of novel four trisaccharides from the beverage: O-β-D-fructopyranosyl-(2->6)-O-β-D-glucopyranosyl-(1->3)-D-glucopyranose, O-β-D-fructopyranosyl-(2->6)-O-[β-D-glucopyranosyl-(1->3)]-D-glucopyranose, O-β-D-glucopyranosyl-(1->1)-O-β-D-fructofuranosyl-(2<->1)-α-D-glucopyranoside and O-β-D-galactopyranosyl-(1->1)-O-β-D-fructofuranosyl-(2<->1)- α-D-glucopyranoside.     

Study of thermal stability for tertiary pyridine ion exchange resin and anti-corrosion property of structural material toward eluents used in the advanced ORIENT cycle process

A multi-functional separation process is proposed as one of the technologies for implementing the Adv.-ORIENT (Advanced Optimization by Recycling Instructive ElemeNTs) Cycle concept [1]. The tertiary pyridine-type anion exchange resin (TPR) embedded in silica beads (silica-supported TPR) was demonstrated suitable for the separation process of actinides from spent fuel. In this process, hydrochloric acid (HCl) and a mixture of nitric acid (HNO₃) and methanol (MeOH) are used as eluents. In order to apply this process to an engineering plant scale, two important issues must be evaluated to prove the system suitability. One is an environmental aspect represented by the use of HCl solution which is corrosive to many materials. The other is clarification of the reactive safety of silica-supported TPR and the HNO₃–MeOH solvent mixture. Four types of metals, Ta, Zr, Nb, and Hastelloy-B (28%Mo–Ni) were selected as candidate materials which are anti-corrosive toward HCl. Corrosion experiments were conducted in HCl type simulated high level liquid waste (SHLLW) solution at room temperature for a maximum 720 h and at 90 °C for 336 h. Ta showed an all-round anti-corrosion property in HCl type SHLLW solution, and Hastelloy-B was only acceptable at room temperature. Thermal analysis by differential scanning calorimetry was done to investigate the thermal stability of silica-supported TPR-NO₃/MeOH/HNO₃ mixtures. Heating experiment results on a gram scale were also obtained and evaluated to determine the conditions necessary to avoid runaway reactions. As a result, it was confirmed that a vigorous exothermic reaction can be avoided by controlled decrease of temperature.     

Surface tension and viscosity of molten vanadium measured with an electrostatic levitation furnace

Surface tension and viscosity of molten vanadium were measured over a wide temperature range by the oscillating drop method in an electrostatic levitation furnace. Over the (2023 to 2517) K temperature range, the surface tension can be expressed as γ(T)/(10^?3 N/m) = 1935 ? 0.27 {(T ? T_m)/K} with T_m = 2183 K. Over the same temperature span, the viscosity can be expressed as η(T)/(10^?3 Pa · s) = 1.23exp[2.27 · 10⁴/(RTK^?1)], where R is the gas constant.     

Specific fragmentation of the K‐shell excited/ionized pyridine derivatives studied by electron impact: 2‐, 3‐ and 4‐methylpyridine

Fragmentation of the pyridine ring upon K‐shell excitation/ionization has been studied with gaseous 2‐, 3‐ and 4‐methylpyridine by the electron‐impact method. Ab initio molecular orbital (MO) calculations were also carried out to explore electronic states correlating with specific fragments. Some specific fragmentation channels were identified from the ionic fragments enhanced characteristically at the N 1s edge. Yields of the C₂HN⁺ and C₅H₅⁺/C₅H₆⁺ ions show that the fission of the N? C2 and C4? C5/C5? C6 bonds of the ring is likely to occur after the N 1s excitation and ionization. Ab initio MO calculations for the 2‐methylpyridine molecule indicate that the dissociation channels to produce these ions are only accessible through the excited states of the parent molecular dication, which can be formed by Auger decays after the N 1s ionization. Fragment ions via hydrogen rearrangement are produced as well, but the rearrangement is not a phenomenon specific to the K‐shell excitation/ionization. Copyright © 2010 John Wiley & Sons, Ltd.     

Photocatalytic hydrogen production from water in self-assembled supramolecular iridium-cobalt systems

Supramolecular photosynthetic systems made up of the [Ir(ppy)(2)(bpy)](+) and [Co(bpy)(3)](2+) cores (ppy = 2-phenylpyridinate, bpy = 2,2'-bipyridine) are in situ self-assembled in aqueous media to generate H(2) upon visible light irradiation, where one of them recorded a relatively high turnover number of 20.     

Electronic structures of single-walled carbon nanotubes encapsulating ellipsoidal C70

The molecular orientation of ellipsoidal C(70) in single-walled carbon nanotubes (SWCNTs) depends on the tube diameter (d(t)). Photoluminescence (PL) studies reveal that the fullerene encapsulation effects on the optical transition energy of SWCNTs are significantly different for C(70) and C(60) at d(t) = 1.405-1.431 nm. This indicates that the transition from the "lying" alignment to the "standing" alignment occurs at d(t) ≈ 1.41 nm and the electronic states of SWCNTs are very sensitive to the interspacing between the encapsulated molecules and the SWCNTs. The present findings suggest that the electronic structure of SWCNTs is tunable not only by alternating the encapsulated molecules but also by controlling their molecular orientations, thus paving the way for development of novel SWCNT-based devices.     

Ice chromatography: current progress and future developments

Ice chromatography, in which water-ice particles are employed as a chromatographic stationary phase, has proven an efficient technique for probing the solution/ice interface. The preparation of fine ice particles has allowed us to not only obtain higher-resolution separation but also investigate the molecular processes occurring on the ice surface in more detail. Chromatographic investigations have revealed that two or more hydrogen bonds are simultaneously formed between a solute and the dangling bonds on the ice surface when the solute gives measurable retention. Several compounds, including estrogens, amino acids, and acyclic polyethers, have been successfully separated by ice chromatography with a hexane-based mobile phase. In addition, this method effectively probes the surface melting of the ice stationary phase and the liquid phase that coexists with water ice at thermodynamic equilibrium. The thickness of the surface liquid layer and the size of the liquid phase that grows inside an ice particle have been evaluated. The perspectives of this method are also discussed.      

Selective determination of mono- and dihydroxylated analogs of polybrominated diphenyl ethers in marine sponges by liquid-chromatography tandem mass spectrometry

A number of bioactive brominated secondary metabolites, including hydroxylated polybrominated diphenyl ethers, have been isolated from algae, sponges, and bacteria. In the present study, a screening method using liquid-chromatography tandem mass spectrometry was developed for the identification and selective determination of dihydroxy (diOH), hydroxy-methoxy (OH-MeO), and dimethoxy (diMeO) analogs of tetra- to hexa-BDEs in marine biota. In negative atmospheric pressure chemical ionization (APCI) mode, diOH and OH-MeO analogs provided intense [M-H](-) ions, whereas diMeO analogs provided characteristic [M-Br+O](-) and [M-CH(3)](-) ions. This enabled the diOH-, OH-MeO-, and diMeO-PBDEs to be distinguished using selected reaction monitoring transitions in the APCI source. Recoveries of 2'-OH-6-MeO-2,3',4,5'-tetra-BDE in spiked marine samples were 84 ± 5 %, with a limit of quantification at 9.1 ng mL(-1) (signal-to-noise ratio = 10). The developed method was used to analyze two sponge species collected from Palau, Micronesia; the concentration ratio of diOH-tetra-BDE:OH-MeO-tetra-BDE was 10:1 for the Lamellodysidea sp., whereas it was 1:30 for the Callyspongia sp.