Comparative Study of Electrodeposited and Ion Beam Mixed Fe-Ni-Cr Alloys

Electrodeposited Fe-Ni-Cr alloys irradiated with 209 MeV energy ⁸⁴Kr ions were investigated by conversion electron Mössbauer spectroscopy, X-ray diffraction and electron microprobe analysis. Significant dose dependent changes were found between Mössbauer spectra of the irradiated and non-irradiated deposits. These changes reflect the dose dependent transformation of the metastable ferromagnetic phase to the paramagnetic one.     

A new fast type of Mössbauer spectrometer for the rapid determination of iron-bearing minerals used in the paint industry

A new miniaturised Mössbauer spectrometer has been developed for laboratory and industrial application. Equipped with a YAIO₃:Ce crystal fast scintillation detector unit and mini transducer for the energy modulation of gamma rays, the unique mechanical design enhances protection from radiation and prevents disturbance by mechanical vibrations. It can be used with various types of cryostat and furnace.Supported by the LabVIEW graphical programming environment and by the new algorithm for the quantification of iron-components, the spectrometer can be used as a single-purpose instrument for the rapid determination of the Fe²⁺/Fe³⁺ ratio in ilmenite and Morin transition temperature of hematite. It can also be used to monitor the manufacturing processes for titanium white and copperas red.     

Possible new approaches to superheavy elements — the (HI,αχn) reaction and the neutron-rich beam

We first report the recent experiment on the²³²Th(⁴⁰Ar,α3n)²⁶⁵[106] reaction carried out at RIKEN to test the usefulness of the (HI,αχn)-type reaction for the production of very heavy elements. Reaction residues recoiling out of a thin ThO₂ target bombarded with 5.2 MeV/u⁴⁰Ar beam were separated from the beam by using a gas-filled recoil separator and implanted onto a two-dimensionally position-sensitive solid-state detector placed at the focal plane of the separator. The preliminary results of the analysis show that the cross section of the above reaction is around 1 nb, being about four times larger than that of the²⁴⁸Cm(²²Ne,5n)²⁶⁵[106] reaction reported in the literature. Secondly, we discuss briefly the merits and demerits of the use of a neutron-rich beam for the production of superheavy elements, in which we stress the possibility that the demerit of weak secondary-beam intensity is nearly cancelled out by the increase of the survival probability with the increase of the neutron number of the compound nucleus and also by the possible enhancement of near-barrier fusion.     

CEMS Study on Fe Films Deposited by Laser Ablation

Iron thin films deposited on Al foil by pulsed laser ablation were characterized by conversion electron Mössbauer spectrometry (CEMS). The hyperfine fields became large and the isomer shift was closed to that of bulk α-Fe with increasing the thickness of deposited films. The small grains are so reactive that small particles of Fe^III oxides were produced in thin deposited layers. The magnetic orientation of the deposited films became from parallel to in-plane to at random. The small grains were considered to grow by aggregating with ablation time.

     

Metabolism of tetrahydrobiopterin: Its relevance in monoaminergic neurons and neurological disorders

(6R)‐L‐erythro‐5,6,7,8‐tetrahydrobiopterin (BH4) is an essential cofactor for aromatic amino acid hydroxylases, such as phenylalanine hydroxylase (PAH), tyrosine hydroxylase (TH), tryptophan hydroxylase, and nitric oxide synthase, which catalyze physiologically important reactions in mammals. The biosynthesis and metabolism of BH4 is usually studied mostly in the liver and only slightly in the brain, as the BH4 level in the liver is relatively high because BH4 is required for the reaction of PAH. We found that GTP (guanosine triphosphate) cyclohydrolase I, an enzyme for the biosynthesis of BH4, is a causative gene for DOPA (3,4‐dihydroxyphenylalanine)‐responsive dystonia (also called Segawa's disease), and that partial deficiency of BH4 leads to the dysfunction of the nigrostriatal dopaminergic neurons without hyperphenylalaninemia. We analyzed BH4‐deficient mice that were produced by disruption of a BH4‐synthesizing gene by a gene‐knockout technique. We found that the protein amount of TH was highly dependent on the amount of BH4, especially in nerve terminals. Our research suggests that BH4 metabolism in the brain should be different from that in the liver, and that altered metabolism of BH4 should lead to neuropsychiatric disorders including Parkinson's disease. © 2008 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 8: 378–385; 2008: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20166     

Development of heterodyne detection of dynamic light scattering enhanced by the Talbot effect for the size measurement of nanoparticles.

A new type of dynamic light scattering method for the size measurement of nanoparticles was developed using a transmission grating. A sample cell was located behind the grating, and light was incident from the grating side. The scattered light by a solution with nanopariticles was mixed with diffracted light by the grating, and the mixed signal was detected; namely, the diffracted light was used as reference light for heterodyne detection. It was confirmed that the S/N ratio of the autocorrelation curve was 26-times improved by heterodyne detection. Furthermore, the S/N ratio was improved by setting the sample cell at the sample grating distance where the electromagnetic field is maximum due to the Talbot effect. Size measurements for several kinds of nanoparticles were demonstrated by this new method.     

Determination of carbon in copper by photon activation analysis

Determination of carbon in copper has been studied by photon activation analysis using 30 MeV bremsstrahlung. Chemical separation of carbon as CO₂ was performed by the combustion method in a high flow rate of oxygen stream. It has been demonstrated that the trace amount of carbon in copper can be determined accurately and precisely, and that the detection limit is 0.02 g.     

Dimensional stability of regenerated cellulose film in relation to orientations of crystalline and noncrystalline phases

The dimensional stability of regenerated cellulose film on swelling with water is discussed in relation to the biaxial orientation of the two kinds of structural units, cellulose II crystallites and noncrystalline chain segments, and their anisotropic swelling (anisotropic absorption of water). Considerable dimensional stability in the plane of the film but enormous instability of thickness on swelling in water of some commercial cellophanes is qualitatively interpreted in terms of the planar orientation of crystal (101) planes along the film surface and the orientation of the noncrystalline chain segments parallel to the film surface. The dimensional changes on swelling from the completely dry state to 10% moisture regain were further interpreted quantitatively in terms of the degrees of biaxial orientation of the two kinds of structural units and their degrees of anisotropic swelling by modifying the Hermans monophase model for crystalline and noncrystalline biphase structures. The following degrees of anisotropic swelling of the structural units were thus obtained: q_{c, [101]} = 0.40%, q_{c, [101 ]} = ?0.33%, and q_a = 2.42%.