A positive type alkaline developable thermally stable and photosensitive polymer based on partially O-methylated poly(2,6-dihydroxy-1,5-naphthylene), an acidolytic de-cross-linker, and a photoacid generator

A positive working and chemically amplified photosensitive polymer based on partially (30%) O-methylated poly(2,6-dihydroxy-1,5-naphthylene) [PMPDHN (30)], 1,3,5-tris[(2-vinyloxy)ethoxy]benzene (TVEB) as an acidolytic de-cross-linker, and a photoacid generator (5-propylsulfonyloxyimino-5H-thiophen-2-ylidene)-(2-methylphenyl)acetonitrile (PTMA) has been developed. Poly(2,6-dihydroxy-1,5-naphthylene) (PDHN) with a number-average molecular weight of 33,000 was prepared by oxidative coupling polymerization of 2,6-dihydroxynaphthalene (2,6-DHN) using di-μ-hydroxo-bis-[(N,N,N′,N′-tetramethylethylenediamine)copper(II)] chloride [CuCl(OH)TMEDA] as the catalyst in 2-methoxyethanol at room temperature. PDHN was converted to PMPDHN by treating with iodomethane. The resist showed a sensitivity of 19.4 mJ cm⁻² and a contrast of 7.5 when it was exposed to 436 nm light, followed by post-baking at 120 °C for 5 min and developing with 2.38 wt% aqueous tetramethylammonium hydroxide (TMAH) solution at 25 °C. A fine positive image featuring 6 μm line and space patterns was obtained on the film exposed to 20 mJ cm⁻² of UV-light at 436 nm by the contact-printed mode. The optically estimated dielectric constants (at 1 MHz) of PMPDHN (30) with and without TVEB and PTMA are 3.03 and 3.01, respectively. The moisture absorption (1.7 wt%) of the resist system based on PMPDHN (30) and TVEB is very low compared to that (4.3%) of the resist system consisting of PDHN and 4,4′-methylenebis[2,6-bis(hydroxymethyl)]phenol (MBHP).     

Mechanism‐Based Inhibitor of DNA Cytosine‐5 Methyltransferase by a SNAr Reaction with an Oligodeoxyribonucleotide Containing a 2‐Amino‐4‐Halopyridine‐C‐Nucleoside

In chromatin, 5‐methylcytosine (mC), which represents the fifth nucleobase in genomic DNA, plays a role as an inducer of epigenetic changes. Tumor cells exhibit aberrant DNA methylation patterns, and inhibition of human DNA cytosine‐5 methyltransferase (DNMT), which is responsible for generating mC in CpG sequences, is an effective strategy to treat various cancers. Here, we describe the design, synthesis, and evaluation of the properties of 2‐amino‐4‐halopyridine‐C‐nucleosides (d^XP) and oligodeoxyribonucleotides (ODNs) containing d^XP as a novel mechanism‐based inhibitor of DNMTs. The designed ODN containing ^XPpG forms a complex with DNMTs by covalent bonding through a nucleophilic aromatic substitution (S_NAr) reaction, and its cell proliferation activity is investigated. This study suggests that d^XP in a CpG sequence of DNA could serve as a potential nucleic acid drug lead in cancer chemotherapy and a useful chemical probe for studies of epigenetics. Our molecular design using a S_NAr reaction would be useful for DNMTs and other protein–DNA interactions.     

Preparation of diblock copolymer based on poly(4-n-butyltriphenylamine) via palladium coupling polymerization

A self-condensing monomer 4-(4′-bromophenyl)-4″-n-butyldiphenylamine (1) was synthesized, and successfully converted to poly(4-n-butyltriphenylamine) (PBTPA) by arylamination using palladium catalyst. PBTPAs can be functionalized at both terminals separately by adding an aryl bromide or arylamine derivatives as a terminator, which enabled us to prepare the diblock copolymer PBTPA-block-PEO. Polymer characterization was performed by ¹H NMR, ¹³C NMR, and DSC, which confirmed that the PEO segment was successfully introduced at the terminal of PBTPA. The surface morphology in a thin film of PBTPA-block-PEO was examined by AFM, revealing that a microphase-separated structure or cup-shaped structure with PEO sphere domains formed when the film was spin-cast from 1,1,2,2-tetrachloroethane solutions of different concentrations.     

Synthesis and luminescent properties of block copolymers based on polyfluorene and polytriphenylamine

For the preparation of block copolymers containing polyfluorene (PF) and hole transporting segment, PF homopolymers with diphenylamine terminals were synthesized by Suzuki coupling polymerization. The terminals of PF were converted to polytriphenylamine (PTPA) block by C–N coupling polymerization to give PTPA-block-PF-block-PTPA (PF-PTPA) triblock copolymers with different PTPA chain lengths. These polymers were soluble in common organic solvents and readily formed thin films by solution processing. All of the polymers exhibited similar UV absorption and PL emission properties both in chloroform solution and in film state. PF-PTPA block copolymers showed relatively high HOMO compared with that of PF by cyclic voltammetry. Compared with corresponding PF homopolymers, the EL devices based on PF-PTPA block copolymers showed higher luminance and current efficiency than those of PF homopolymers because of the improvement of hole injection by the introduction of PTPA segment.     

Dynamic viscoelastic properties of collagen gels in the presence and absence of collagen fibrils

We measured the dynamic viscoelasticities of collagen gels prepared and modified by four different methods: i) collagen gels cross-linked by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) after their preparation, ii) collagen gels cross-linked simultaneously with their preparation, iii) collagen gels irradiated with gamma rays after their preparation, and iv) collagen gels directly formed from an acidic collagen solution by gamma-cross-linking. Dynamic viscoelasticities of all samples were measured using a rheometer before and after heating for 30 min at 80 °C. The collagen gels sequentially cross-linked by 125 mM EDC after preparation and then heated exhibited mechanically strong properties (storage modulus G′, 7010 Pa; loss modulus G″, 288 Pa; Young's modulus E, 0.012 in the rapidly-increasing phase and 0.095 in the moderately-increasing phase; tensile strain, 5.29; tensile stress σ, 0.053). We generally conclude that the G′ value decreases when gels without fibrils are heated. On the other hand, well cross-linked collagen gels with thick fibrils, such as gels sequentially cross-linked with 125 mM EDC after preparation or gamma-cross-linked conventional gels irradiated at 40 kGy, exhibit a distinct increase in G′ value after heating. Those gels also have thick, twisted, or fused fibrils of collagen.     

Identification of a novel gene controlling homothallism in the yeast Kazachstania naganishii isolated in Japan

A novel gene controlling homothallic life cycle was identified in the yeast Kazachstania naganishii isolated in Japan. This gene was isolated by means of complementing a mutation, mti1, which had led to heterothallism from original homothallism in the yeast. The configuration of original mutation in MTI1 gene revealed that a truncated product is formed due to occurrence of a stop codon by a nucleotide insertion. When the gene was disrupted with a marker, the disruptant spore clone was haploid and stably heterothallic. Disfunction of the gene caused inability to self‐diploidize due to defect of mating‐type interconversion. The gene MTI1 (for Mating Type Interconversion) is a weak homolog of the Saccharomyces cerevisiae VID22/ENV11, which has been reported to function in vacuolar protein processing. K. naganishii has a gene representing significant homology with the HO gene of S. cerevisiae on chromosome V, which has not been clarified to be involved in regulation of life cycle in K. naganishii. The MTI1 gene defined in this study is located on K. naganishii chromosome IV and does not represent significant homology to the above ScHO‐like gene and any other genes concerning life cycles of yeasts. From the viewpoint of gene evolution, it is extremely interesting that the MTI1 gene is a new type of gene controlling homothallism in addition to an HO‐type gene, leading to discovery of an unknown mechanism regulating life cycles in yeasts.     

Compact sensor for measuring two-dimensional tilt using a two-dimensional transmission grating and the Talbot effect

This paper proposes a tilt sensor that measures the small two-dimensional tilt of a plane reflective object using the Talbot effect. It is an extension of a previously proposed one-dimensional tilt sensor. The light beam reflected from the object impinges on a hexagonal grating, and the intensity of the diffracted wave is detected on an image sensor located at a Talbot distance from the grating. The diffraction intensity displaces due to the tilt of the object. The displacement is calculated by the Fourier transform method to obtain the two-dimensional tilt. This sensor is very simple and compact. The principle of the sensor is explained for a grating with a general pattern. An experiment using a hexagonal grating shows its validity. Discussions are given for making it more practical.     

Terahertz Imaging System for Medical Applications and Related High Efficiency Terahertz Devices

A terahertz (THz) imaging system and high efficient terahertz sources and detectors for medical applications were developed. A fiber laser based compact time domain terahertz tomography system was developed with a high depth resolution of less than 20 μm. Three-dimensional images of porcine skin were obtained including some physical properties such as applied skin creams. The discrimination between healthy human tissue and tumor tissue has been achieved using reflection spectra. To improve the THz imaging system, a ridge waveguide LiNbO₃ based nonlinear terahertz generator was studied to achieve high output power. A ridge waveguide with 5-7 μm width was designed for high efficiency emission from the LiNbO₃ crystal by the electro-optic Cherenkov effect. Terahertz electronic sources and detectors were also realized for future imaging systems. As electronic source devices, resonant tunneling diode (RTD) oscillators with a patch antenna were fabricated using an InGaAs/InAlAs/AlAs triple barrier structure. On the other side, Schottky barrier diode (SBD) detectors with a log-periodic antenna were fabricated by thin-film technology on a Si substrate. Both devices operate above 1 THz at room temperature. This electronic THz device set could provide a future high performance imaging system.     

A 1.0 V power supply, 9.3 GB/s write speed, Single-Cell Self-Boost program scheme for high performance ferroelectric NAND flash SSD

A Single-Cell Self-Boost (SCSB) program scheme is proposed to achieve a 1.0 V power supply operation in Ferroelectric (Fe-) NAND flash memories. The proposed SCSB scheme only self-boosts the channel voltage of the cell to which the program voltage V_PGM is applied in the program-inhibit NAND string. The program disturb is well suppressed at the 1.0 V power supply voltage in the proposed program scheme. The power consumption of the Fe-NAND at V_CC = 1.0 V decreases by 86% compared with the conventional floating gate (FG-) NAND at V_CC = 1.8 V without the degradation of the write speed. The number of NAND chips written simultaneously in Solid-State Drives (SSD) increases by 6.7 times and the 9.3 GB/s write throughput of the Fe-NAND SSD is achieved for an enterprise application.