Genomic RNA of HIV-1 contains localized structures critical for viral replication. Its structural analysis has demonstrated a stem-loop structure, SLSA1, in a nearby region of HIV-1 genomic splicing acceptor 1 (SA1). We have previously shown that the expression level of vif mRNA is considerably altered by some natural single-nucleotide variations (nSNVs) clustering in SLSA1 structure. In this study, besides eleven nSNVs previously identified by us, we totally found nine new nSNVs in the SLSA1-containing sequence from SA1, splicing donor 2, and through to the start codon of Vif that significantly affect the vif mRNA level, and designated the sequence SA1D2prox (142 nucleotides for HIV-1 NL4-3). We then examined by extensive variant and mutagenesis analyses how SA1D2prox sequence and SLSA1 secondary structure are related to vif mRNA level. While the secondary structure and stability of SLSA1 was largely changed by nSNVs and artificial mutations introduced to restore the original NL4-3 form from altered ones by nSNVs, no clear association of the two SLSA1 properties with vif mRNA level was observed. In contrast, when naturally occurring SA1D2prox sequences that contain multiple nSNVs were examined, we attained significant inverse correlation between the vif level and SLSA1 stability. These results may suggest that SA1D2prox sequence adapts over time, and also that the altered SA1D2prox sequence, SLSA1 stability, and vif level are mutually related. In total, we show here that the entire SA1D2prox sequence and SLSA1 stability critically contribute to the modulation of vif mRNA level.

We propose a novel standing technique of fabricating a high-aspect-ratio tip structure. The technique utilizes the bending of films induced by ion irradiation. Using this technique, the position and aspect ratio can be easily controlled by the conventional thin-film deposition and photolithography processes. We found that the standing is realized when ion energy is chosen at which the film internal stress at the medium depth of the film relaxes, while low- and high-energy irradiations simply bend up and bend down the film, respectively. We demonstrate the application of the thin-film standing technique to field emitter fabrication.

A field emitter array (FEA) with four stacked gate electrodes, that is, FEA with a built-in einzel lens, was fabricated using an etch-back technique. In our method, gate hole opening is a self-aligned process; therefore, the axes of electrode holes are well aligned without precise lithography. Emitter tip opening is also a unique process: the tip opening is usually carried out using buffered hydrofluoric (BHF) acid to prevent tip damage. However, in the case of the FEA with a multistacked electrode, BHF etching produces a long undercut under the electrode, particularly under the upper electrode. In our process, the upper lens electrode is used as a photolithography mask when etching silicon dioxide in order to prevent excess undercut. In this paper, the details of fabrication are described.

We propose and demonstrate that vertically curved waveguides (VCWs) enable vertical coupling between silicon wire waveguides and optical fibers with low wavelength dependence and polarization dependence for wide telecommunication wavelength band light. To bend these VCWs, we implanted silicon ions into silicon wire cantilevers from the vertical direction. The internal stress distribution that was induced by ion implantation drove the bending force, and we achieved vertical bending of the waveguides, with curvature radii ranging from 3 to 25 μm. At a radius of curvature of 6 μm, we obtained a coupling loss of 3 dB using a lens fiber.

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