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Notes: The involvement of excitatory amino acid (EAA) toxicity in ischaemia-induced neuronal cell death has long been suggested. However, in the hippocampus, the brain site most vulnerable to ischaemia, the detailed spatial and temporal patterns of EAA release are not yet known. To address this issue, we have developed a novel strategy for the continuous, real-time, two-dimensional monitoring of EAA release from brain slices. As EAA detector, we used a cell line transformed with the N-methyl-d-aspartate (NMDA) receptor, which is exclusively activated by EAAs, leading to an increase in the intracellular Ca2+ level. Combined with a calcium imaging technique, the use of this cell line allowed the temporal and regional analysis of EAA release from a brain slice placed directly on top of the clonal cells in a culture dish. Using this strategy, we demonstrated ischaemia-induced EAA release in rat hippocampal slices. Increased EAA release was seen initially in the CA1 region, about 3 min after the beginning of ischaemia, then in the CA3 region and dentate gyrus, and, finally, throughout the hippocampal slice. Regional differences in extracellular EAA levels were also seen, with more EAA being released from the CA1 region than from the middle dentate gyrus. The present results are especially interesting as neurons in the CA1 region are more vulnerable to ischaemia than those in the CA3 region and dentate gyrus.

Notes: A modified atomic force microscopy (AFM) system, based on a force modulation technique, has been used to find an approximate value for the elastic modulus of a single peptide molecule directly from a mechanical test. For this purpose a self-assembled monolayer built from two kinds of peptides, reactive (able to anchor to the AFM tip) and nonreactive, was synthesized. In a typical experiment a single C3K30C (C=cysteine, K=lysine) peptide molecule was stretched between a Au(111) substrate and the gold-coated tip of an AFM cantilever to which it was attached via gold–sulfur bonds. The amplitude of the cantilever oscillations, due to an external force applied via a magnetic particle to the cantilever, was recorded by a lock-in amplifier and recalculated into stiffness of the stretched molecule. A longitudinal Young's modulus for the α-helix of a single peptide molecule and for the elongated state of this molecule has been estimated. The obtained values; 1.2±0.3 and 50±15 GPa, for the peptide α-helix and elongated peptide backbone, respectively, seem to be reasonable comparing them to the Young's modulus of protein crystals and linear organic polymers. We believe this research opens up a means by which scientists can perform quantitative studies of the elastic properties of single molecule, especially of biologically important polymers like peptides or DNA. © 2001 American Institute of Physics.

Notes: In-plane crystal orientation of copper phthalocyanine (CuPc) films formed by organic molecular-beam epitaxy have been successfully controlled by using vicinal Si(001)-(2×1)-H as a substrate, containing atomic steps of an approximately 4 nm period. A continuous film was grown at 60 °C and the film thickness ranged between 5 and 8 molecular layers. By observing a frictional force image of the film, 90% of the molecular columns were found to align across the substrate step rows. The preferential orientation is considered to be induced by artificial surface lattices, which result from the striped effective contact area between the rigid CuPc crystals and the stair-like surfaces. The anisotropic optical properties of the film have been also confirmed by polarized reflection measurements. © 2001 American Institute of Physics.

Notes: Polarization of sintered hydroxyapatite (HAp) ceramics by application of an external dc field at higher temperature was analyzed by thermally stimulated depolarization current (TSDC) measurements. The mechanisms for the polarization and depolarization of HAp were discussed in relation to the instability of the protons in the hydroxide groups. The TSDC spectra consisted of broad peaks, while the ferroelectric substances such as the BaTiO3 ceramics exhibited a sharp peak. Although the maximum current density of 7.87 nA cm−2 for the HAp polarized at 400 °C under 1.0 kV cm−1 was approximately 1/12 lower than that of BaTiO3, the polarization charge of 14.9 μC cm−2 was almost twice as large as that of BaTiO3. Considering the activation energy of 0.72–0.89 eV for the depolarization, it was revealed that the polarization of HAp was ascribed to the migration of protons in the columnar OH− channels with a micrometer-order distance. It was also found that the polarization charge was large and long enough to enhance the biological reactivity of HAp ceramics for biomedical implants. © 2001 American Institute of Physics.

Notes: A niobium membrane was immersed in hydrogen plasma and could be electrically biased to vary the energy of bombarding ions in the range of 1–200 eV. The fluxes of plasma driven absorption and permeation were almost entirely governed by incident suprathermal neutrals (mostly, thermal atoms), whose energy does not depend on membrane bias, but the ions of controllable energy do affect the neutral-induced permeation through modifying the membrane surface. At the zero bias a high temperature-independent plasma driven permeation (superpermeation) was observed alongside of an enhanced absorption. Bombardment by ions of an energy higher than 50 eV resulted in a sharp decrease of the plasma driven permeation/retention and in an acceleration of boundary processes of absorption/reemission of thermal molecules. At ion energies below 50 eV, the effect of ion bombardment on the plasma driven permeation and the kinetic coefficients of boundary processes were nonmonotonic in ion energy, having a maximum at ∼10 eV. Both an in situ doping with O of the bulk of Nb and a membrane temperature increase reduced the effects of ion bombardment to their complete disappearance. Responsible for that was the replenishment by means of surface segregation of an oxygen monolayer sputtered by ion bombardment. © 2001 American Institute of Physics.

Notes: Collisions of ions with charged dust grains are important for the propagation of low frequency waves such as dust acoustic waves and dust ion-acoustic waves. The collision cross-sectional area of charged dust grains depends on the velocity of an ion beam. The collision cross-sectional area of charged dust grains with beam ions is measured. It is compared with the geometrical cross-sectional area of the grain. The experiment is performed in a dusty double-plasma device with glass beads of 8.9 μm in average diameter. The ion beam current and energy are measured with a directional retarding potential analyzer. It is observed that, when dust density inside the system is increased, the beam current ratio is reduced. From the reduction of the ion beam current, the effective cross-sectional area of the dust particle is estimated as a function of the beam energy. © 2001 American Institute of Physics.

Notes: High-n ballooning instabilities are studied with an initial-value code for toroidally rotating tokamaks, where n is a toroidal mode number. The effects of toroidal rotation are classified into two parts: (i) increase of effective pressure gradient due to the centrifugal force of the toroidal flow, and (ii) averaging of local magnetic equilibrium configuration over a period of poloidal angle in the case of finite flow-velocity shear. With the increase of effective pressure gradient in the rigid-rotation case, the growth rate of ballooning mode increases in the low-pressure regime as the toroidal flow velocity is increased, whereas it decreases in the high-pressure regime. The flow-velocity shear generally reduces the growth rate of the high-n ballooning mode by the averaging of the local equilibrium magnetic configuration. However, it is found that the ballooning mode becomes unstable by increasing the flow-velocity shear in a low-aspect-ratio tokamak. This is understood by the change of the local magnetic configuration, and by the changes of both the mode structure and the potential function in the ballooning space. © 2001 American Institute of Physics.

Notes: An experiment on ion-acoustic solitary waves in dusty plasma is performed in a dusty double-plasma device. The leading part of a sinusoidal pulse develops to an oscillation. The troughs of the oscillation become shallow when dust particles are mixed into the plasma. The Mach velocity of the first peak in the oscillation decreases due to the presence of negatively charged dust grains for a fixed height of the peak. The width of the peak normalized with Debye length increases when the dust particles are introduced into the plasma. The experimental results are compared with the numerical integrations of a modified Korteweg–de Vries–Burgers equation which contains the terms of kinematic viscosity and of collisions of ions with the dust particles. © 2001 American Institute of Physics.

Notes: Ideal magnetohydrodynamic stability analysis of local pressure-driven modes in an L=1 heliotron, Heliotron J [M. Wakatani et al., Nucl. Fusion 40, 569 (2000)], is investigated by means of three-dimensional (3D) ballooning formalism and the Mercier criterion. In 3D systems such as heliotrons, the ballooning modes are separated into two categories: One is tokamak-like ballooning modes which are localized only in the poloidal direction, and the other is modes inherent to 3D systems which are localized on the specific flux tubes. The tokamak-like ballooning modes change to the Mercier modes in the limit that the mode is sufficiently extended along the field line, but the nonaxisymmetric ballooning mode does not so. The L=1 Heliotron J equilibrium investigated here has weak global shear and the dominant Fourier amplitudes of magnetic-field strength is rather different from the conventional helical systems with L=2 helical coils. Since the weak global shear causes the reduction of integrated local shear along the field lines easily, which combines with strongly modulated destabilizing effects on the flux surface, the nonaxisymmetric ballooning modes localized on the specific flux tubes can become unstable. On the other hand, the Mercier modes are suppressed due to the deep magnetic well. The results obtained from the model equilibrium of L=2 Large Helical Device (LHD), for which several reports have already published [N. Nakajima, Phys. Plasmas 3, 4556 (1996), for example], are also shown and compared with the results of Heliotron J. The LHD equilibrium employed here has a magnetic hill region at the outer radius, and this tends to make the Mercier modes unstable. It is found that this difference of the Mercier stability property in two equilibria is concerned in the local ballooning stability, and the notable difference of local dispersion relations appears. It is also found from the comparison of two systems that the nonaxisymmetric ballooning modes have a similar property to the tokamak-like ballooning modes, in the sense of the s¯-α¯ diagram where s¯ and α¯ are shear and pressure gradient parameter. © 2001 American Institute of Physics.

Notes: Electrical and hydrophilic properties of TiOx films obtained by plasma enhanced chemical vapor deposition (PECVD) were investigated in connection with OH group content of the films. A microcrystalline TiOx film prepared by rf magnetron sputtering deposition (RFMSD) was used as a reference sample in this study. Compared to the RFMSD film, the PECVD TiOx films had good hydrophilicity after ultraviolet (UV) light irradiation, low dark, and high photoexcited currents in a vacuum and high sensitivity of their dark and photoexcited currents to surface adsorbates. Low dark and high photoexcited currents measured in vacuum for the PECVD TiOx films were explained by the effect of inactivation of the defect states such as dangling bonds by the termination of OH group. Due to this effect, the PECVD TiOx films are referred to as hydro-oxygenated TiOx:OH films in this article. The sensitivity of the photoexcited currents to surface adsorbates noticed for the TiOx:OH films suggests that the surface potential is modified in response to electron affinity of the surface adsorbates during UV light irradiation. This effect contributes to generation of oxidants due to interaction between photoexcited carriers and surface adsorbates and, hence, improves the hydrophilicity of the TiOx:OH films. These results suggest that both the hydrophilicity and electrical properties of the TiOx:OH films are strongly related to the film OH groups. © 2001 American Institute of Physics.