Formation of higher-order fullerene dianions in collisions with Na atoms

We have measured electron capture cross sections in collisions between higher order fullerene anions C_n ^- (n=76, 78, 82, 84, 86, 90 and 96) and Na atoms. The ions were produced in an electrospray ion source (ESI) and accelerated to an energy of 50 keV. The measured cross section for dianion formation is three times larger for C₉₆ than that for C₆₀. The latter cross section was earlier found to be 36 ?². The dramatic increase of the cross section with fullerene size is explained by means of the curve crossing model for electron transfer.     

Synthesis of novel 4(5)-(5-aminotetrahydropyran-2-yl)imidazole derivatives and their in vivo release of neuronal histamine measured by brain microdialysis

The (2R,5S)-trans- and (2S,5S)-cis-stereoisomers 1a and 1b of 4(5)-(5-aminotetrahydropyran-2-yl)imidazole, which have two chiral centers and adopt a stable chair conformation, were synthesized via cyclization of diol intermediates 7 using L-glutamine as the starting material. Their enantiomers, (2S,5R)-trans-1c and (2R,5R)-cis-1d, were synthesized by the same methodology from D-glutamine. Stereo isomers 1a-d were converted into cyanoguanidines 11a-d, and into N-isopropyl and N-3,3-dimethylbutyl derivatives 12a-d and 13a-d, respectively. The results of in vivo brain microdialysis of the derivatives apparently indicated that only (2S,5R)-isomers increased the release of neuronal histamine. Among the many (2S,5R)-N-alkyl derivatives, 13c (OUP-133) and 18 (OUP-153) increased histamine release to 180-190% and 180-200% of basal levels, respectively, and were found to be novel histamine H(3) antagonists.     

Dynamically reconfigurable characteristics of a double phase conjugate mirror using Sn2P2S6 crystals and their application to optical inter-satellite communication

A double phase conjugate mirror (DPCM), created by two mutually incoherent beams entering photorefractive nonlinear materials, can generate a phase conjugate beam whose reflectivity may be greater than 100%. Even though the conditions of the incident beams are changed, the DPCM can be dynamically reconfigured by using a Sn₂P₂S₆ crystal with a high response speed. These features of the DPCM are advantageous, particularly in an optical inter-satellite communication system. In particular, use of the phase conjugate beam from the DPCM offers wavefront compensation and amplification in satellite communication. In addition, the dynamically reconfigurable DPCM using a Sn₂P₂S₆ crystal relaxes the acquisition accuracy of the signal beam in the system. In this study, the temporal and spatial operating characteristics of the DPCM using a Sn2P2S6 crystal were first clarified. Next, an inter-satellite system based on the DPCM was proposed, and it was demonstrated that our system significantly improves the tolerance of the acquisition accuracy and tracking time.     

High performance batch production of LREBa2Cu3Oy using novel thin film Nd-123 seed

A batch production for fabrication of LREBa₂Cu₃O_y (LRE: Sm, Gd, NEG) “LRE-123” pellets are developed in air and Ar-1% O₂ using a novel thin film Nd-123 seeds grown on MgO crystals. The SEM and XRD results conformed that the quality and orientation of the seed crystals are excellent. On the other hand, new seeds can withstand temperatures >1100 °C, as a result, the cold seeding process was applied even to grow Sm-123 material in Air. The trapped field observed in the best 45 mm single-grain puck of Gd-123 was in the range of 1.35 T and 0.35 T at 77.3 K and 87.3 K, respectively. The average trapped field at 77.3 K in the 24 mm diameter NEG-123 samples batch lies between 0.9 and 1 T. The maximum trapped field of 1.2 T was recorded at the sample surface. Further, the maximum trapped field of 0.23 T at 77 K was recorded in a sample with 16 mm diameter of Sm-123 with 3 mol% BaO₂ addition. As a result we made more then 130 single grain pucks within a couple of months. Taking advantage of the single grain batch processed material, we constructed self-made chilled levitation disk, which was used on the open day of railway technical research Institute. More then 150 children stood on the levitation disk and revel the experience of levitation. The present results prove that a high-performance good-quality class of LREBa₂Cu₃O_y material can be made by using a novel thin film Nd-123 seeds.     

Cooling dynamics of self‐assembled monolayer coating for integrated gold nanocrystals on a glass substrate

Picosecond time‐resolved X‐ray diffraction has been used to study the nanoscale thermal transportation dynamics of bare gold nanocrystals and thiol‐based self‐assembled monolayer (SAM)‐coated integrated gold nanocrystals on a SiO₂ glass substrate. A temporal lattice expansion of 0.30–0.33% was observed in the bare and SAM‐coated nanocrystals on the glass substrate; the thermal energy inside the gold nanocrystals was transported to the contacted substrate through the gold–SiO₂ interface. The interfacial thermal conductivity between the single‐layered gold nanocrystal film and the SiO₂ substrate is estimated to be 45 MW m^?2 K^?1 from the decay of the Au 111 peak shift, which was linearly dependent on the transient temperature. For the SAM‐coated gold nanocrystals, the thermal dissipation was faster than that of the bare gold nanocrystal film. The thermal flow from the nanocrystals to the SAM‐coated molecules promotes heat dissipation from the laser‐heated SAM‐coated gold nanocrystals. The thermal transportation of the laser‐heated SAM‐coated gold nanocrystal film was analyzed using the bidirectional thermal dissipation model.     

Experimental and modeling researches of dust particles in the HL-2A tokamak

The investigation of dust particle characteristics in fusion devices has become more and more imperative.In the HL-2A tokamak,the morphologies and compositions of dust particles are analyzed by using scanning electron microscopy(SEM) and energy dispersive x-ray spectroscopy(EDX) with mapping.The results indicate that the sizes of dust particles are in a range from 1 μm to 1 mm.Surprisingly,stainless steel spheres with a diameter of 2.5μm-30 μm are obtained.The production mechanisms of dust particles include flaking,disintegration,agglomeration,and arcing.In addition,dynamic characteristics of the flaking dust particles are observed by a CMOS fast framing camera and simulated by a computer program.Both of the results display that the ion friction force is dominant in the toroidal direction,while the centrifugal force is crucial in the radial direction.Therefore,the visible dust particles are accelerated toriodally by the ion friction force and migrated radially by the centrifugal force.The averaged velocity of the grain is on the order of~100 m/s.These results provide an additional supplement for one of critical plasma-wall interaction(PWI) issues in the framework of the International Thermonuclear Experimental Reactor(ITER) programme.     

Preparation of TiO2 thin films using water-soluble titanium complexes and their photoinduced properties

Titanium dioxide thin films were prepared by using four water-soluble titanium complexes of titanium-lactate, tartalate, malate and salicylate complex solutions. The crystalline phases detected in the films were anatase. The surface microstructures of the four film samples were different in their grain sizes. Photocatalytic decomposition activity of the four films was almost the same, but their photoinduced hydrophilicities were different. The film prepared using titanium-salicylate complex exhibited lower hydrophilic conversion rate than the other films. Grain size and stress yielded to the film are considered to be important factors on the photoinduced hydrophilicity.     

Cross-sectional TEM analysis of laser-induced ripple structures on the 4H–SiC single-crystal surface

The microstructures of femtosecond laser-induced ripples formed on a 4H–SiC single-crystal surface were studied by cross-sectional transmission electron microscopy (TEM), with particular attention on the crystal structure underlying fine and coarse ripples differing in period and morphology. Conventional and high-resolution TEM analyses showed that a continuous amorphous layer approximately 10 to 50 nm thick covers the topmost region of both fine and coarse ripples. These results strongly suggest that the fundamental surface deformation process is common for the entire region of fine and coarse ripples, even though the factors that determine their periods are different.     

Bacterium organizes hierarchical amorphous structure in microbial cellulose

A pellicle, a gel film of microbial cellulose, is a supermolecular system containing 99% of water by weight, which is closely related to an amorphous structure in it. Using ultra-small-angle neutron scattering, in order to cover over a wide range of length scales from nm to 10 microm, we examined the hierarchical amorphous structure in the microbial cellulose, which is synthesized by a bacterium (Acetobacter xylinum). The microbial cellulose swollen by water shows small-angle scattering that obeys a power law q -behavior according to q -alpha as a function of the magnitude of the scattering vector q . The power law, determined by scattering, is attributed to a mass fractal due to the distribution of the center of mass for the crystallite (microfibril) in amorphous cellulose swollen by water. As q increases, alpha takes the values of 2.5, 1, and 2.35, corresponding, respectively, to a gel network composed of bundles, a bundle composed of cellulose ribbons, and concentration fluctuations in a bundle. From the mass fractal q -behavior and its length scale limits, we evaluated a volume fraction of crystallite in microbial cellulose. It was found that 90% of the cellulose bundle is occupied by amorphous cellulose containing water.