Reduction of carbon impurities in silicon oxide films prepared by rf plasma-enhanced CVD

Silicon oxide films were deposited at near room temperature by a remote-type radio frequency plasma-enhanced chemical vapor deposition using a mixture of tetramethoxysilane and oxygen as source gas. The temperature of the reactor wall was controlled from 25 to 150°C. Carbon impurities which existed as Si–CH₃ in the deposited films were reduced markedly when the substrate temperature was kept higher than the wall temperature during deposition. The optimum substrate temperature was 50°C to obtain carbon-free silicon oxide films at a wall temperature of 30°C. X-Ray photoelectron spectroscopic analyses of the films proved that carbon impurities existed only on the film surfaces.     

Self‐Degradable Lipid‐Like Materials Based on “Hydrolysis accelerated by the intra‐Particle Enrichment of Reactant (HyPER)” for Messenger RNA Delivery

RNA‐based therapeutics is a promising approach for curing intractable diseases by manipulating various cellular functions. For eliciting RNA (i.e., mRNA and siRNA) functions successfully, the RNA in the extracellular space must be protected and it must be delivered to the cytoplasm. In this study, the development of a self‐degradable lipid‐like material that functions to accelerate the collapse of lipid nanoparticles (LNPs) and the release of RNA into cytoplasm is reported. The self‐degradability is based on a unique reaction “Hydrolysis accelerated by intra‐Particle Enrichment of Reactant (HyPER).” In this reaction, a disulfide bond and a phenyl ester are essential structural components: concentrated hydrophobic thiols that are produced by the cleavage of the disulfide bonds in the LNPs drive an intraparticle nucleophilic attack to the phenyl ester linker, which results in further degradation. An oleic acid‐scaffold lipid‐like material that mounts all of these units (ssPalmO‐Phe) shows superior transfection efficiency to nondegradable or conventional materials. The insertion of the aromatic ring is unexpectedly revealed to contribute to the enhancement of endosomal escape. Since the intracellular trafficking is a sequential process that includes cellular uptake, endosomal escape, the release of mRNA, and translation, the improvement in each process synergistically enhances the gene expression.     

Changes in color of spruce by repetitive treatment of light-irradiation and heat treatment

This paper deals with the changes in color of spruce by the repetitive treatment of light-irradiation and heat treatment. The color of photo-thermally treated wood discolored by light-irradiation is recovered by heat treatment.     

Serum CA125 measurement is useful in 3 cases with pericardial effusion

Previously we reported that serum CA125 level is elevated in cases of pericardial effusion. We report three cases in which serum CA125 measurement is useful for assessing clinical status. In case 1, a 19-year-old came to our hospital for cardiac tamponade. Moderate degree of pericardial effusion and high CA125 level were observed. After the pericardectomy the serum CA125 level was normalized and pericardial effusion disappeared. Case 2, a 50-year-old man with mesothelioma and in whom serum CA125 level was elevated with pericardial effusion. After cardiac drainage his condition improved, with decreased CA125 level. However, later the CA125 level rose and recurrent localized pericardial effusion with worsening condition was observed. In case 3, in a 78-year-old woman with pericardial effusion no recurrence was observed after pericardial drainage. Her CA125 value was normal. These results indicated that measurement of CA125 value is a useful marker for assessing the clinical course of this disease.     

Electronic structures of polyacenacene and polyphenanthrophen anthrene. Design of one-dimensional graphite

The electronic structures of polyacenacene (PAA) and its geometrical isomer, polyphenanthrophenanthrene (PPhP) have been studied using the tight-binding SCF-CO (self consistent field-crystal orbital) method with respect to a design of one-dimensional (1D) graphite. The geometry of each polymer is optimized from the energetic point of view. It has been found that from the analysis of the electronic structure of its optimized geometry, PAA favours the structure without the carbon-carbon bond alternations, yielding no band gap. In this sense, PAA is a typical 1D-graphite. On the other hand, it is predicted that the magnitude of the band gap of PPhP in its optimized geometry is almost equal to that of trans-polyacetylene.     

Effect of pre-treatment and annealing temperature on the strength of SiC-Ni monofilament composites

Monofilament composites were prepared by plating nickel on Nicalon, a commercial SiC fibre obtained from a precursor of polycarbosilane. The surface condition of the fibre was controlled by pre-treatments prior to the nickel plating. The tensile strength of the monofilament composite decreased with increasing annealing temperature, especially above 973 K, where reaction between the fibre and nickel begins. The extent of degradation of the composite caused by the reaction was different for different pre-treatment and annealing temperatures. The degradation was explained by the Griffith theory. The calculated strength of annealed composites agreed fairly well with the measured values. SEM observations showed that the strength is closely related to the morphology of the reaction products.     

Epitaxial growth of strained Si1−yCy films by the hot-wire cell method and its application to metal oxide semiconductor devices

We succeeded in obtaining strained Si_1−yC_y films at a substrate temperature of 200 °C by the hot-wire cell method. The substitutional carbon concentration in films annealed at 700 °C was 0.9%, while it was limited to 0.13% for a sample grown by gas-source molecular beam epitaxy (MBE) at a substrate temperature of 700 °C. We investigated the thermal stability of strained Si_1−yC_y films for device application. Annealing at over 900 °C caused the formation of 3C-SiC and relaxation of the strain occurred. From this result, we found that the process temperature should be lower than 800 °C. A low-temperature MOSFET process, in which all process temperatures after deposition of Si_1−yC_y were lower than 800 °C, was developed and a strained Si_1−yC_y MOSFET was fabricated.     

A risk estimation method of railway embankment collapse due to heavy rainfall

Slope collapses of embankments and cut slopes along railways are often triggered by heavy rainfall of a typhoon, etc., and have much influence on the running safety of trains. It is of vital importance to find out the risky sites along the railway to control railway operations. For this purpose, it is desiable to develop a practical damage estimation method which can accurately predict the risks of slope collapse and can be simply applied by many railway workers. This paper deals with a method of estimating the railway embankment collapse in times of heavy rainfall based on a multivariate analysis. The critical rainfall is proposed to be defined as a product of the amount of accumulated rainfall and the maximum hourly rainfall. This value is also determined by a function whose variables include information on the embankment such as soil and structural properties, the surface ground geotechnical characteristics, the catchment and seepage, and the empirical rainfall. Therefore, the risk evaluation for embankments can be performed with the critical rainfall value.