High Field ESR System and Its Application to the Study of Quantum Spin Systems

Developments of the high field ESR system in Kobe University is presented. Using Gunn oscillators and backward traveling oscillators (BWO), we can cover the frequency region from 30 to 1183.6 GHz with the use of InSb detector. Pulsed magnetic field up to 30 T is available and we are now trying to extend the field up to 40 T. Temperature range is from 1.8 to 300 K. Using this system, we studied S=1/2 ladder like system Cu₂(C₅H₁₂N₂)₂Cl₄, and found a new magnetic transition at 10.1 T at 1.8 K. The temperature dependence of ESR in Cu₂(C₅H₁₂N₂)₂CI₄ shows g-shift below 8 K which corresponds to the maximum of the magnetic susceptibility. The g-shift below 8 K suggests the increase of the quantum fluctuation in the system, and the role of the quantum fluctuation in Cu₂(C₅H₁₂N₂)₂CI₄ is discussed.     

Severe myoclonic epilepsy in infancy: evolution of seizures

Demonstration of the full extent of abnormality in patients with the Struge-Weber syndrome (SWS) is important for prognosis and in planning surgery to remove the seizure focus. We compared single-photon emission computed tomography (SPECT), MRI and CT in nine children under the age of 4 years with seizures as part of SWS, in an attempt to determine the optimal method of imaging in different clinical settings. Seven unilateral and two bilateral cases were studied by interictal 99mtechnetium hexamethylpropyleneamineoxime (HMPAO) SPECT, and contrast-enhanced CT and MRI, giving information on 11 abnormal hemispheres. All imaging modalities showed abnormalities in every child. Perfusion imaging showed focal regions of decreased uptake in 9 of 11 (82%) abnormal hemispheres and demonstrated a widespread decrease but no focal defect in 2; it also revealed crossed cerebellar diaschisis in 2 cases. CT demonstrated typical gyriform calcification in 9 of 11 (82%) affected hemispheres. Contrast-enhanced MRI showed more extensive involvement than contrast-enhanced CT in 5 of 11 (45%) cases. The area of hypoperfusion shown by SPECT was smaller than the area of contrast enhancement on MRI in 6 of 11 cases (55%), comparable in 3 (27%) and larger in 2 cases (18%). CT is sufficient to confirm the clinical diagnosis of SWS, but MRI frequently shows more extensive abnormal areas. 99mTc HMPAO imaging is a useful addition when it is important to know the full extent of the disease, for example prior to surgery. It is likely to detect areas of hypoperfusion, representing ischaemic regions, which may act as an epileptogenic focus and may not be shown by CT or MRI.     

Kinetic study on free radical polymerization of alkyl acylamidoacrylates by pulsed laser polymerization using nitrogen laser

Radical polymerization of captodatively substituted alkyl acylamidoacrylates was studied by pulsed laser polymerization using a N₂ laser. Propagation rate coefficient of the acrylates was varied with solvents used in spite of a radical mechanism, but little varied with methyl, n-propyl, and isopropyl substituents on the acrylates. Arrhenius parameters for the propagation indicated that a solvent affected mostly on a frequency factor rather than a activation energy. In addition, it was suggested that these captodatively substituted propagating radicals were thermodynamically persistent but kinetically active in propagation, which resulted in rather smooth propagation in spite of bulky 1,1-disubstituted olefins. The mechanism of the polymerizations was discussed in detail on the basis of the kinetic studies and ESR spectroscopy.     

Development of fabrication process for Ag/polydiacetylene (core/shell) hybridized nanocrystals

Core/shell hybridized nanocrystals composed of Ag nanoparticle core and polydiacetylene shell were fabricated successfully by means of “co-reprecipitation/microwave irradiation method”. The hybridized nanocrystals were characterized using transmission electron microscopy (TEM) observation and UV–vis absorption spectroscopy. UV–vis spectral measurements revealed that polydiacetylene shell was the red phase while π-conjugated backbone is distorted. Detailed mechanism of formation of the red phase was discussed.     

Recovery of Precious and Base Metals from Waste Printed Circuit Boards Using a Sequential Leaching Procedure

This paper considers the issue of recycling of waste printed circuit boards (WPCBs) containing precious and base metals in appreciable amounts. High-pressure oxidative leaching (HPOL) with dilute sulfuric acid resulted in removal of a significant amount of base metals from a WPCB ash sample obtained by incineration at 800°C. The parameters investigated in the precious metal leaching from WPCB residue after HPOL included the sulfuric acid concentration, thiourea concentration, oxidant concentration, leaching temperature, and leaching time. Recovery of gold, silver, and palladium of 100%, 81%, and 13% from the WPCB residue sample was achieved by thiourea leaching under optimized conditions. The results show that the efficiency of precious metal dissolution from the WPCB sample using thiourea solution depended strongly on the concentration of both thiourea and oxidant.     

Palladium‐Catalyzed Three‐Component Reaction of 3‐(Tri‐n‐ butylstannyl)allyl Acetates,Aldehydes, and Triorganoboranes: An Alternative to the Carbonyl Allylation Using α,γ‐Substituted Allylic Tin Reagents

A three‐component reaction of 3‐(tri‐n‐butylstannyl)allyl acetates, aldehydes, and triorganoboranes in the presence of a palladium‐Xantphos catalyst system predominately gave (E)‐anti‐homoallylic alcohols with high diastereoselectivity and good to high levels of alkene stereocontrol. An efficient chirality transfer was observed when an enantioenriched substrate was employed. The reaction was initiated by the formation of an allylic gem‐palladium/stannyl intermediate, which subsequently underwent allylation of the aldehyde by an allyltributyltin followed by a coupling reaction of the in‐situ‐generated (E)‐vinylpalladium acetate with the triorganoborane.

     

Reaction mechanism in Ti–SiC–C powder mixture during pulse discharge sintering

During pulse discharge sintering (PDS) of Ti/SiC/C powder mixture, combustion synthesis reactions occurred at heating rates above 20 °C/min. With an increase in heating rate, combustion synthesis occurred at higher temperatures. The essential of this combustion reaction is the liquid reaction between Ti and formed Ti₅Si₃. The exothermic TiC formation during PDS process promotes this liquid reaction. We have found that the combustion reactions alone did not finish the formation reactions for Ti₃SiC₂, and further heating following the combustion reactions is necessary for the synthesis process of Ti₃SiC₂.     

Resonance surface X-ray scattering technique to determine the structure of electrodeposited Pt ultrathin layers on Au(1 1 1) surface

It is demonstrated that resonance surface X-ray scattering (RSXS), in which incident X-ray energy close to the Pt L_III absorption edge (11.55 keV) is used, is very useful for the determination of the structure of electrodeposited Pt thin layers on a Au(1 1 1) surface. This technique was applied to characterize the structure of electrodeposited Pt layers on Au(1 1 1) substrates prepared under two extreme conditions, which are known to provide rough and atomically flat layers. Detailed structural information was obtained by RSXS measurements and it was confirmed that the structures of the Pt layers were as reported. Pt atoms of the atomically flat monolayer were found to be situated at the threefold hollow cubic closest packing (ccp) sites of the Au(1 1 1)-(1 × 1) surface.     

Structural Investigation of the Binding of 5‐Substituted Swainsonine Analogues to Golgi α‐Mannosidase II

Golgi α‐mannosidase II (GMII) is a key enzyme in the N‐glycosylation pathway and is a potential target for cancer chemotherapy. The natural product swainsonine is a potent inhibitor of GMII. In this paper we characterize the binding of 5α‐substituted swainsonine analogues to the soluble catalytic domain of Drosophila GMII by X‐ray crystallography. These inhibitors enjoy an advantage over previously reported GMII inhibitors in that they did not significantly decrease the inhibitory potential of the swainsonine head‐group. The phenyl groups of these analogues occupy a portion of the binding site not previously seen to be populated with either substrate analogues or other inhibitors and they form novel hydrophobic interactions. They displace a well‐organized water cluster, but the presence of a C(10) carbonyl allows the reestablishment of important hydrogen bonds. Already approximately tenfold more active against the Golgi enzyme than the lysosomal enzyme, these inhibitors offer the potential of being extended into the N‐acetylglucosamine binding site of GMII for the creation of even more potent and selective GMII inhibitors.