Evaluation of thin‐film photodevices and application to an artificial retina

Abstract— First, conventional poly‐Si thin‐film photodevices, p‐i‐n thin‐film photodiodes (TFPDs) and p‐n TFPDs, were evaluated. It was found that the photo‐induced current (Iphoto) is not simultaneously relatively high and independent of the applied voltage (Vapply). Next, a novel poly‐Si thin‐film photodevice, p‐i‐n thin‐film phototransistor (TFPT), is proposed. It is found that the Iphoto is simultaneously relatively high and independent of the Vapply because the depletion layer is formed in the entire intrinsic region and the electric field is always high. These characteristics are preferable for photosensor applications. Finally, the p‐i‐n TFPT was applied to an artificial retina. The photo‐illuminance profile is correctly detected and the output voltage profile is correspondingly outputted. This artificial retina is expected to be suitable for human beings because it can potentially be fabricated on a flexible, harmless, plastic, and organic substrate.     

Local Structural Distortions and Phase Separation in Cuprates

We report evidence from Raman measurements of local lattice distortions in the cuprates, which are induced at room temperature by varying the hydrostatic pressure and correlate with changes in the superconducting transition temperature. Anomalous nonlinear pressure dependence is observed for almost all A_g phonons of the YBa₂Cu₃O_6.5, YBa₂Cu₃O_over, and YBa₂Cu₄O₈ superconducting single crystals, which occurs at pressures where the transition temperature shows also characteristic changes. The results are compared with a similar correlation found between transition temperature and spectral modifications in Bi₂Sr₂CaCu₂O₈ by pressure and in YBa₂Cu₃O_x and La_2–xSr_xCuO₄ by chemical doping. There are strong indications that the saturation of T_c with pressure or compositional doping in these cuprates is mainly related with lattice instabilities and probably also with phase separation phenomena.     

Antiferromagnetic Ordering in the One-Dimensional Edge-Sharing CuO2 Chain System Ca2+x Y2−x Cu5O10

We have investigated the spin state of the one-dimensional edge-sharing chain system Ca_2+x Y_2–x Cu₅O₁₀ with 0x1.667 by means of the magnetic susceptibility and specific heat measurements, using the large-size single-crystals. It has been found that the magnetic ground state is an antiferromagnetically ordered state for 0x1.0, while a spin-gap state seems to be formed for x1.5. Accordingly, it appears that the quantum critical point is located between x=1.0 and 1.5 in Ca_2+x Y_2–x Cu₅O₁₀.     

The GABAA receptor is expressed in human neurons derived from a teratocarcinoma cell line

NT2 cells, a human teratocarcinoma cell line, are shown to be differentiated in neuron-like cells (NT2-N cells) by treatment with retinoic acid. The present study identified the neurotransmitter receptors expressed in NT2-N cells using patch-clamp recording. Voltage-sensitive Na+ currents, which are specific for neurons, were observed in NT2-N cells but not in NT2 cells, suggesting that NT2-N cells actually function as neurons. Glutamate receptor agonists, N-methyl-D-aspartate (NMDA) and kainate, evoked whole-cell currents. In addition, gamma-aminobutyric acid (GABA) evoked currents and the currents were inhibited by the selective GABAA receptor antagonist, bicuculline. In outside-out patches, GABA elicited single channel currents with two classes of the slope conductance (26 and 50 pS). No current, however, was induced by ACh, serotonin, or dopamine NT2-N cells, thus, express at least two types of the major excitatory and inhibitory neurotransmitter receptor in the central nervous system, the glutamate and GAGAA receptors, suggesting that these receptors have a crucial role in neurotransmission from the earlier stage of the brain development.     

Differential interactions of gentamicin with mouse junctional and extrajunctional ACh receptors expressed in Xenopus oocytes

The nicotinic acetylcholine receptors (AChRs) from Torpedo electric organ and mouse muscles when expressed in Xenopus oocytes desensitize with different time courses. Initially, the role of cAMP-dependent phosphorylation on the gamma subunits in the different desensitization rates was investigated by expressing normal and mutant AChRs in the oocytes cultured in the presence of gentamicin. Mutant Torpedo AChRs lacking the potential cAMP-dependent phosphorylation sites in the gamma subunit appear to desensitize like normal Torpedo AChRs. Similarly, mutant mouse extrajunctional AChRs containing a newly created phosphorylation site in the gamma subunit appeared to desensitize like normal mouse AChRs, which lack the potential cAMP-dependent phosphorylation site in the gamma subunit. These results suggest that different rates of desensitization between the Torpedo and muscle extrajunctional AChRs are not attributable to differential cAMP-dependent phosphorylation of these AChRs. Subsequently, to determine whether gentamicin used in culturing oocytes differentially interacts with muscle junctional and extrajunctional AChRs, we analyzed rates of current decay following different gentamicin treatments. Both chronic and acute treatment with gentamicin profoundly accelerated the decay of whole-cell currents mediated by both types of AChR. The effect of prolonged gentamicin treatment on junctional AChRs was long lasting when compared to treatment on extrajunctional AChRs. Although the two types of AChR still desensitize differently in the absence of gentamicin, these results suggest that the characteristic desensitization of junctional and extrajunctional AChRs observed previously is largely due to differential interactions of gentamicin with the two types of AChR.     

Effect of Plasma Treatment on Titanium Surface on the Tissue Surrounding Implant Material

Early osseointegration is important to achieve initial stability after implant placement. We have previously reported that atmospheric-pressure plasma treatment confers superhydrophilicity to titanium. Herein, we examined the effects of titanium implant material, which was conferred superhydrophilicity by atmospheric-pressure plasma treatment, on the surrounding tissue in rat femur. Control and experimental groups included untreated screws and those irradiated with atmospheric-pressure plasma using piezobrush, respectively. The femurs of 8-week-old male Sprague-Dawley rats were used for in vivo experiments. Various data prepared from the Micro-CT analysis showed results showing that more new bone was formed in the test group than in the control group. Similar results were shown in histological analysis. Thus, titanium screw, treated with atmospheric-pressure plasma, could induce high hard tissue differentiation even at the in vivo level. This method may be useful to achieve initial stability after implant placement.     

8-[2-(2-Pentyl-Cyclopropylmethyl)-Cyclopropyl]-Octanoic Acid and Its Diastereomers Improve Age-Related Cognitive Deterioration

Racemic 8-[2-(2-pentyl-cyclopropylmethyl)-cyclopropyl]-octanoic acid (DCP-LA), a linoleic acid derivative with cyclopropane rings instead of cis-double bonds, contains possible four diastereomers such as α,α-, α,β-, β,α-, and β,β-DCP-LA. The present study examined the effect of racemic and diastereomeric DCP-LA on age-related learning and memory disorders using accelerated-senescence-prone mice 8 (SAMP8) and accelerated-senescence-resistant mice 1 (SAMR1). In the water maze test, the acquisition and retention latencies for SAMP8 mice were significantly longer than the latency for SAMR1 mice, indicating spatial learning and memory impairment for SAMP8 mice. All the racemic (1?mg/kg, per os) and diastereomeric DCP-LA (0.25?mg/kg, per os) significantly shortened the acquisition latency for SAMP8 mice, and racemic, α,α- and α,β-DCP-LA significantly shortened the retention latency, with the advantage greater than the acetylcholine (ACh) esterase inhibitor galanthamine. The results of the present study show that all the racemic and diastereomeric DCP-LA, has the potential to improve age-related learning and memory deterioration, the potential varying among them.