Synchrotron radiation 57Fe-M?ssbauer spectroscopy using nuclear monochromator

Formation of LaFeO₃ nanoparticles obtained from thermal decomposition of organometallic precursors was investigated as a function of the heat-treatment temperature. The precursors heat-treated below 300°C were amorphous, but above 350°C a single-phase of nanocrystalline LaFeO₃ was formed. The LaFeO₃ nanoparticles showed the superparamagnetic behavior in both magnetization and M?ssbauer measurements. With increasing heat-treatment temperature, the crystallite size of LaFeO₃ nanoparticles was gradually increased. The quadrupole splitting and isomer shift of paramagnetic doublet pattern were affected by the growth of LaFeO₃ particles.     

Determining anomalous dynamic patterns in price indexes of the London Metal Exchange by data synchronization

Data synchronization based on the Kuramoto model for collective synchronization and hypothesis testing based on the rank test combined with the random shuffling surrogate method are applied to finding major feature patterns of weekly nonferrous metal returns from the time series of daily spot and futures price indexes in the London Metal Exchange since 1989. Our results suggest the existence of day-of-the-week anomalies in the metal returns. We conjecture that such anomalies are large-scale manifestations of synchronously accumulated risk-aversive actions of individual market players.     

Thermoregulated phase‐transfer catalysis via PEG‐armed Ru(II)‐bearing microgel core star polymers: Efficient and reusable Ru(II) catalysts for aqueous transfer hydrogenation of ketones

Thermoregulated phase‐transfer catalysis for the transfer hydrogenation of 2‐octanone in 2‐propanol/H₂O biphasic media was achieved with ruthenium‐bearing microgel‐core star polymers with amphiphilic, thermosensitive poly(ethylene glycol) (PEG) arms [Ru(II)‐PEG star], which were directly prepared by the ruthenium‐catalyzed living radical polymerization in conjunction with a phosphine ligand‐carrying styrene derivative. The star polymers were first placed in the aqueous (lower) layer at room temperature and immediately moved into the organic (upper) layer at 100 °C, and once again, moved down to the aqueous layer (lower) upon cooling the solution to room temperature. The Ru(II)‐PEG star catalyst was clearly superior to the original Ru(II) catalyst and related non‐microgel catalysts [Ru(II)‐PEG block] in terms of activity and recovery/recycle, due to the unique designer structure of the microgel‐core star polymers. Other substrates (less hydrophobic alkyl ketones and aromatic ketone) were also efficiently hydrogenated into the corresponding sec‐alcohols with the star catalyst in aqueous media. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 373–379, 2010     

Environmentally benign deprotection of dithioacetals using 30% hydrogen peroxide catalyzed by Fe(acac)3 and sodium iodide

The reaction of dithioacetals with 30% hydrogen peroxide in the presence of catalytic amounts of iron(III) acetylacetonate and sodium iodide efficiently produced the corresponding carbonyl compounds in high yields.     

Aldol‐type group‐transfer polymerization of silyl vinyl ethers using silyl perfluoroalkaneimides as nonmetal catalysts

We investigated the catalytic activity of bis(nonafluorobutanesulfonyl)imide (Nf₂NH), acting as a Brønsted acid, and its silylated imide, t‐butyldimethylsilyl nonafluorobutanesulfonylimide (Nf₂NTBDMS), acting as a Lewis acid, for aldol‐type of group‐transfer polymerization (Aldol‐GTP) of silyl vinyl ethers. Aldol‐GTPs of t‐butyldimethylsilyl vinyl ether (VOTBDMS) and triethylsilyl vinyl ether (VOTES) proceeded in dichloromethane at 0 °C with benzaldehyde as the initiator. Nf₂NH catalyzed the polymerization of VOTBDMS although the product poly(VOTBDMS) had a molecular weight of 2510, which was considerably smaller than that predicted by the ratio of the initial monomer to initiator concentrations, and the smaller molecular weight was a consequence of desilylation of VOTBDMS before the polymerization step. Conversely, when Nf₂NTBDMS was used as the catalyst, poly(VOTBDMS) with molecular weight >16,000 was obtained. The Nf₂NTBDMS‐catalyzed polymerization was more rapid than polymerizations that used t‐butyldimethylsilyl trifluoromethanesulfonylimide, t‐butyldimethylsilyl hexafluorocycropropanesulfonylimide, or zinc bromide as the catalyst, even though the ratio of Nf₂NTBDMS to the monomer was the smallest used. With VOTES as the monomer, and Tf₂NTBDMS as the catalyst, a poly(VOTES) with a syndiotactic tendency (mm:mr:rr = 9:44:47) was produced. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3516–3522     

Sequence-regulated copolymers via tandem catalysis of living radical polymerization and in situ transesterification

Sequence regulation of monomers is undoubtedly a challenging issue as an ultimate goal in polymer science. To efficiently produce sequence-controlled copolymers, we herein developed the versatile tandem catalysis, which concurrently and/or sequentially involved ruthenium-catalyzed living radical polymerization and in situ transesterification of methacrylates (monomers: RMA) with metal alkoxides (catalysts) and alcohols (ROH). Typically, gradient copolymers were directly obtained from the synchronization of the two reactions: the instantaneous monomer composition in feed gradually changed via the transesterification of R(1)MA into R(2)MA in the presence of R(2)OH during living polymerization to give R(1)MA/R(2)MA gradient copolymers. The gradient sequence of monomers along a chain was catalytically controlled by the reaction conditions such as temperature, concentration and/or species of catalysts, alcohols, and monomers. The sequence regulation of multimonomer units was also successfully achieved in one-pot by monomer-selective transesterification in concurrent tandem catalysis and iterative tandem catalysis, providing random-gradient copolymers and gradient-block counterparts, respectively. In contrast, sequential tandem catalysis via the variable initiation of either polymerization or in situ transesterification led to random or block copolymers. Due to the versatile adaptability of common and commercially available reagents (monomers, alcohols, catalysts), this tandem catalysis is one of the most efficient, convenient, and powerful tools to design tailor-made sequence-regulated copolymers.     

Grazing‐incidence synchrotron‐radiation 57Fe‐Mössbauer spectroscopy using a nuclear Bragg monochromator and its application to the study of magnetic thin films

Energy‐domain grazing‐incidence ⁵⁷Fe‐Mössbauer spectroscopy (E‐GIMS) with synchrotron radiation (SR) has been developed to study surface and interface structures of thin films. Highly brilliant ⁵⁷Fe‐Mössbauer radiation, filtered from SR by a ⁵⁷FeBO₃ single‐crystal nuclear Bragg monochromator, allows conventional Mössbauer spectroscopy to be performed for dilute ⁵⁷Fe in a mirror‐like film in any bunch‐mode operation of SR. A theoretical and experimental study of the specular reflections from isotope‐enriched (⁵⁷Fe: 95%) and natural‐abundance (⁵⁷Fe: ～2%) iron thin films has been carried out to clarify the basic features of the coherent interference between electronic and nuclear resonant scattering of ⁵⁷Fe‐Mössbauer radiation in thin films. Moreover, a new surface‐ and interface‐sensitive method has been developed by the combination of SR‐based E‐GIMS and the ⁵⁷Fe‐probe layer technique, which enables us to probe interfacial complex magnetic structures in thin films with atomic‐scale depth resolution.     

A microfluidic flow distributor generating stepwise concentrations for high-throughput biochemical processing

In this paper, we describe a microfluidic device in which solutions with stepwise concentrations can be accurately generated by continuously introducing two kinds of miscible liquids from each inlet, and biochemical processing can be conducted at the various conditions. Introduced liquid flows are geometrically divided into a number of downstream flows through multiple distribution channels, and each divided flow is then mixed with the divided flow of another liquid at a confluent point. The lengths of the precisely designed distribution channels determine the mixing ratio of the two liquids, without the influence of flow rate. In this study, a PDMS microfluidic device able to generate nine different concentrations was fabricated, and the performance of this device was estimated via colorimetric assay. As a biological application of this device, cell cultivation was performed under different concentration conditions. Due to its simplicity of operation, this microfluidic flow distributor will be applied to various kinds of biological analysis and screening systems.