Classification of involutions on Enriques surfaces

We present the classification of involutions on Enriques surfaces. We classify those into 18 types with the help of the lattice theory due to Nikulin. We also give all examples of the classification.Comment: 25 pages, 42 figure

Surgical results of sacral perineural (Tarlov) cysts.

The purpose of this study was to investigate the surgical outcomes and to determine indicators of the necessity of surgical intervention. Twelve consecutive patients harboring symptomatic sacral perineural cysts were treated between 1995 and 2003. All patients were assessed for neurological deficits and pain by neurological examination. Magnetic resonance of imaging, computerized tomography, and myelography were performed to detect signs of delayed filling of the cysts. We performed a release of the valve and imbrication of the sacral cysts with laminectomies in 8 cases or recapping laminectomies in 4 cases. After surgery, symptoms improved in 10 (83%) of 12 patients, with an average follow-up of 27 months. Ten patients had sacral perineural cysts with signs of positive filling defect. Two (17%) of 12 patients experienced no significant improvement. In one of these patients, the filling defect was negative. In conclusion, a positive filling defect may become an indicator of good treatment outcomes.</p

ニューロトロフィンによる神経分化の制御機構に関する研究

ニューロトロフィンは発生から老化に至る長期間にわたり神経細胞に作用し、生存維持、分化促進、神経機能の獲得・維持などの役割を担う神経栄養因子と考えられている。神経細胞の分化に及ぼすニューロトロフィンの作用は数多く研究されてきたが、その多くは神経分化の後期過程を対象としており、全貌の解明には程遠いのが現状である。そこで本研究では、神経分化のモデル細胞として繁用されるPC12細胞および多分化能をもつ神経幹細胞を用いて、初期神経分化過程におけるニューロトロフィンの作用を検討した。その結果、ニューロトロフィンの一つであるNGFは、p75を介してPI-3キナーゼ/Akt経路を活性化し、分化に先立って増殖停止を誘導すること、また、ニューロトロフィンが神経幹細胞から神経細胞への分化をプライミングすることを明らかにし、ニューロトロフィンが神経分化の初期過程の制御にも深く関わっている可能性が示唆された。Neurotrophin is a family of neurotrophic factors that have profound influences on neuronal development including survival, neuronal differentiation, procurement and maintenance of neuronal functions. Many previous studies have not yet fully clarified critical roles of neurotrophins for neuronal differentiation because those studies focused on the investigations about the role of neurotrophins at late stages of neuronal differentiation. In the present study, we examined mechanisms of neurotrophin-induced neuronal differentiation using PC12 cells and neural stem cells. The results obtained demonstrated that NGF activates PI-3 kinase/Akt pathways via p75 in cultured PC12 cells, which is necessary for the growth arrest, and that neurotrophins have priming effects on neuronal differentiation of neural stem cells cultured from embryonic mouse telencephalon. These findings suggest that neurotrophins also play roles in neuronal differentiation at much earlier stages of neurogenesis than expected before

Electron spin coherence in metallofullerenes: Y, Sc and La@C82

Endohedral fullerenes encapsulating a spin-active atom or ion within a carbon cage offer a route to self-assembled arrays such as spin chains. In the case of metallofullerenes the charge transfer between the atom and the fullerene cage has been thought to limit the electron spin phase coherence time (T2) to the order of a few microseconds. We study electron spin relaxation in several species of metallofullerene as a function of temperature and solvent environment, yielding a maximum T2 in deuterated o-terphenyl greater than 200 microseconds for Y, Sc and La@C82. The mechanisms governing relaxation (T1, T2) arise from metal-cage vibrational modes, spin-orbit coupling and the nuclear spin environment. The T2 times are over 2 orders of magnitude longer than previously reported and consequently make metallofullerenes of interest in areas such as spin-labelling, spintronics and quantum computing.Comment: 5 pages, 4 figure

Evolution of short-range order and its effects on the plastic deformation behavior of single crystals of the equiatomic Cr-Co-Ni medium-entropy alloy

Short-range ordering (SRO), its evolution in the equiatomic Cr-Co-Ni medium-entropy alloy (MEA), and its effects on mechanical properties were investigated by, respectively, electrical resistivity measurements and tension and compression tests on single crystal specimens at room temperature and liquid nitrogen temperature. SRO below 973 K can be monitored by changes in electrical resistivity, which increases gradually with time to a saturation value during isothermal annealing in the temperature range of 673–973 K. While the time required to reach saturation is shorter at higher temperatures, the saturation resistivity is higher at lower temperatures, indicating a higher degree of SRO at lower temperature although it takes longer to reach saturation because of slower kinetics. No significant change in the plastic deformation behavior is found at room temperature and 77 K for different degrees of SRO. The yield stress as well as the slip localization behavior are basically the same after SRO, and the magnitude of yield drop does not correlate with the degree of SRO. Tensile stress-strain curves are not much affected by SRO up to high strain levels, resulting in identical shear stresses for the onset of deformation twinning at room temperature regardless of the degree of SRO. The dislocation structure, variations in dislocation dissociation width, and stacking fault energy are all essentially unchanged