Review Peripheral nerve regeneration using non-tubular alginate gel crosslinked with covalent bonds

We have developed a nerve regeneration material consisting of alginate gel crosslinked with covalent bonds. in the first part of this study, we attempted to analyze nerve regeneration through alginate gel in the early stages within 2 weeks. in the second part, we tried to regenerate cat peripheral nerve by using alginate tubular or non-tubular nerve regeneration devices, and compared their efficacies. Four days after surgery, regenerating axons grew without Schwann cell investment through the partially degraded alginate gel, being in direct contact with the alginate without a basal lamina covering. One to 2 weeks after surgery, regenerating axons were surrounded by common Schwann cells, forming small bundles, with some axons at the periphery being partly in direct contact with alginate. At the distal stump, numerous Schwann cells had migrated into the alginate 8–14 days after surgery. Remarkable restorations of the 50-mm gap in cat sciatic nerve were obtained after a long term by using tubular or non-tubular nerve regeneration material consisting mainly of alginate gel. However, there was no significant difference between both groups at electrophysiological and morphological evaluation. Although, nowadays, nerve regeneration materials being marketed mostly have a tubular structure, our results suggest that the tubular structure is not indispensable for peripheral nerve regeneration.     

Solar cell efficiency tables (version 12)

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined and new entries since January 1998 are briefly described. © 1998 John Wiley & Sons, Ltd.     

Carrier separation analysis for clarifying carrier conduction and degradation mechanisms in high-k stack gate dielectrics

The carrier conduction and the degradation mechanism in n⁺gate p-channel metal-insulator-semiconductor field-effect-transistors with HfAlO_X (Hf: 60 at.%, Al: 40 at.%)/SiO₂ dielectric layers have been investigated using carrier separation method. Since gate current depends on substrate bias and both electron and hole currents are independent of temperature over the range of 25–150 °C, the conduction mechanism for both currents is controlled by a tunneling process. As the interfacial SiO₂ layer (IL) thickness increases in a fixed high-k layer thickness (T_high-k), a dominant carrier in the leakage current changes from hole to electron around 2.2-nm-thick IL. This is due to an asymmetric barrier height for electrons and holes at the SiO₂/Si interface. On the contrary, in the case of a fixed IL thickness of 1.3 nm, the hole current is dominant in the leakage current, regardless of T_high-k. It is shown that the dominant carrier in the leakage current depends on the structure of the high-k stack. Both electron and hole currents for the stress-induced-leakage-current (SILC) state increase slightly relative to the initial currents, which means that the trap generation in the high-k stack occurs near both the conduction band edge of n⁺poly-Si gate and the valence band edge of Si substrate. The electron current at soft breakdown (SBD) state dramatically increases over that for the SILC state, while the hole currents for both the SILC state and SBD are almost the same. This indicates that the defect sites generated in the high-k stack after SBD are located at energies near the conduction band edge of n⁺poly-Si gate. Both the defect generation rate and the defect size in the HfAlO_X/SiO₂ stacks are large compared with those in SiO₂. It is inferred that, in high-k dielectric stack, the defect generation mainly occurs in the high-k side rather than the IL side, and the defect size larger than the case of SiO₂ could be related to a larger dielectric constant of the high-k layer.     

Lateral tunneling transistors fabricated by plane-dependent Si-doping in nonplanar epitaxy on GaAs (311)A and (411)A substrates

We have demonstrated the lateral tunneling transistors on GaAs (311)A and (411)A patterned substrates by using the plane-dependent Si-doping technique. Lateral p⁺-n⁺ tunneling junctions are formed by growing heavily Si-doped layers on patterned substrates. Current—voltage curves for both transistors show gate-controlled negative differential resistance characteristics. Furthermore, the peak current density of the lateral tunneling diodes fabricated on the (311)A patterned substrates increases as buffer layer thickness is increased, and a typical peak current density of 58 A/cm² for p = 6 × 10¹⁹ cm⁻³ and n = 7 × 10¹⁸ cm⁻³ is obtained when the buffer layer thickness is 1.2 μm. This study shows that plane-dependent Si-doping in non-planar epitaxy is a promising technique for fabricating tunneling transistors.     

Crystallographic and electrical properties of platinum film grown by chemical vapor deposition using (methylcyclopentadienyl)trimethylplatinum

Platinum thin films grown by chemical vapor deposition (CVD) using a liquid precursor of (methylcyclopentadienyl)trimethylplatinum were characterized in terms of crystallographic nature, morphology, contaminants, and their influence on electrical properties. The lattice constant of these CVD films (3.91–3.92 Å) is smaller than that of bulk platinum. A high oxygen contaminant is observed, irrespective of the oxygen ratio during growth. A film grown at low oxygen content consists of randomly oriented micro-grains and contains a large amount of carbon contaminants. When the film is grown under oxidative conditions, it shows a 111-textured cylindrical morphology with increasing thickness. The electric resistivity is higher than the bulk standard, and it increases with decreasing oxygen ratio during the film growth. These results indicate that the carbon contaminant causes the randomly oriented micro-grains and contributes to the high residual resistivity.     

Enhanced bioactivity of polyvinylidene chloride films using argon ion bombardment for guided bone regeneration

Polyvinylidene chloride (PVDC) is a long chain carbon synthetic polymer. The objective of this study was to improve the bioactivity of PVDC films through surface modification using argon (Ar) ion bombardment to create Ar-modified PVDC films (Ar-PVDC) to address the clinical problems of guided bone regeneration (GBR), which is technique-sensitive, and low bone regenerative ability. First, the effects of Ar ion bombardment, a low temperature plasma etching technique widely used in industry, on PVDC film wettability, surface chemistry, and morphology were confirmed. Next, fibroblast-like and osteoblast-like cell attachment and proliferation on Ar-PVDC were assessed. As a preclinical in vivo study, Ar-PVDC was used to cover a critical-sized bone defect on rat calvaria and osteoconductivity was evaluated by micro-computed tomography analysis and histological examinations. We found that the contact angle of PVDC film decreased by 50° because of the production of –OH groups on the PVDC film surface, though surface morphological was unchanged at 30 min after Ar ion bombardment. We demonstrated that cell attachment increased by about 40 % and proliferation by more than 140 % because of increased wettability, and 2.4 times greater bone regeneration was observed at week 3 with Ar-PVDC compared with untreated PVDC films. These results suggest that Ar ion bombardment modification of PVDC surfaces improves osteoconductivity, indicating its potential to increase bone deposition during GBR.     

Memory mechanism of printable ferroelectric TFT memory with tertiary structured polypeptide as a dielectric layer

Printable nonvolatile memory devices have been attracting considerable interest because of their application to flexible large-area devices. In order to fabricate such memory devices, it is necessary to discover a new ferroelectric material and to develop an efficient process for its preparation. We have previously reported that poly(γ-methyl-L-glutamate) (PMLG) functions as a ferroelectric layer of an organic thin-film transistor (OTFT) memory device [S. Uemura, A. Komukai, R. Sakaida, M. Yoshida, S. Hoshino, T. Kodzasa, T. Kamata, Synth. Met. 153 (2005) 405]. Further, ferroelectricity is observed when α-helical PMLG molecules are aligned in a direction parallel to the film surface. In this study, we investigate the effect of the tertiary structure of PMLG molecules on the hysteresis of OTFT memory devices, i.e., memory performance. From the results, we conclude that the hysteresis of the OTFT is strongly affected by the helical tertiary structure of PMLG molecules, similar to the structure of a cholesteric liquid crystal phase.     

Radioactivity confinement capability of “PARC” concept for the future reprocessing

Aiming at TRU waste arising reduction and economical competitiveness for the future reprocessing, is proposed an advanced process concept which is named PARC (Partitioning Conundrum Key) process. Enhancement of confinement capability for long-lived nuclides in a simplified Purex process is the primary subject of this R&D project. Technologies for long-lived nuclide recovery are under development, focused on ¹⁴C and ¹²⁹I in head end, ²³⁷Np and ⁹⁹Tc in extraction, and ²⁴¹Am the daughter of ²⁴¹Pu in effluents. Those nuclides focused here are mobile in the environment and highly concerned as potential hazardous among the long-lived nuclides in spent fuels. New functions in PARC process concept are designed to mitigate the environmental impacts of reprocessing wastes and also to improve economy of reprocessing in the future.